Acute Nausea and Vomiting in Adults

Quick Reference

Critical Alerts

• Life-threatening causes require immediate recognition: Bowel obstruction, acute coronary syndrome, diabetic ketoacidosis, raised intracranial pressure, ruptured ectopic pregnancy
• Hydration assessment is the priority: Dehydration increases morbidity and mortality substantially
• Bilious or feculent vomiting indicates obstruction: Requires emergent imaging and surgical consultation
• Coffee-ground or bloody vomitus signifies upper GI bleeding: Immediate resuscitation and gastroenterology consultation
• Antiemetics treat symptoms, not underlying disease: Diagnostic workup must identify and treat the cause
• Pregnancy test mandatory in all women of childbearing age: Pregnancy changes differential diagnosis and treatment options
• Persistent vomiting can cause catastrophic complications: Mallory-Weiss tear (10-15% of upper GI bleeds), Boerhaave syndrome (15-35% mortality)

Life-Threatening Causes

Emergency Antiemetic Treatments

---

Definition and Classification

Overview

Acute nausea and vomiting represent two of the most common presenting complaints in emergency departments worldwide, accounting for approximately 5-10% of all ED visits. Nausea is defined as the subjective, unpleasant sensation of the imminent need to vomit, often accompanied by autonomic symptoms including pallor, tachycardia, diaphoresis, and salivation. Vomiting (emesis) is the forceful expulsion of gastric contents through the mouth via coordinated contractions of the abdominal muscles, diaphragm, and gastric antrum with simultaneous relaxation of the gastroesophageal sphincter. Retching represents the rhythmic, labored contractions that often precede vomiting but occur without expulsion of gastric contents.

While frequently caused by benign, self-limited conditions such as viral gastroenteritis or medication side effects, nausea and vomiting can herald serious, life-threatening disease processes. The emergency physician's primary responsibility involves systematically excluding dangerous etiologies, restoring adequate hydration, providing symptomatic relief, and identifying the underlying cause for definitive treatment.

Classification Systems

By Temporal Pattern:

By Pathophysiological Mechanism:

Epidemiology

Incidence and Prevalence:

• Emergency department visits: 5-10% of all presentations involve nausea/vomiting as chief complaint or significant associated symptom
• Annual ED visits in United States: >8 million for nausea and vomiting
• Hospitalization rate: Approximately 15-20% of ED patients presenting with nausea/vomiting require admission
• Mortality: Overall low (less than 1%) but substantially elevated in specific etiologies (mesenteric ischemia 60-80%, Boerhaave syndrome 15-35%, severe DKA 0.2-2%)

Age and Sex Distribution:

• Bimodal age distribution: Peaks in children/young adults (infectious etiologies) and elderly (serious organic disease)
• Female predominance (60-65% of presentations): Related to pregnancy, migraine, functional disorders, cyclic vomiting syndrome
• Pregnancy-related nausea affects 50-80% of pregnancies; hyperemesis gravidarum occurs in 0.3-3% of pregnancies

Etiological Distribution in Emergency Department:

• Gastroenteritis/infectious: 35-40%
• Medications/iatrogenic: 20-25%
• Pregnancy-related: 10-15% (in women of childbearing age)
• Acute surgical conditions: 8-12%
• Metabolic causes: 5-8%
• Central nervous system pathology: 3-5%
• Cardiac causes: 1-2%
• Undetermined: 5-10%

---

Pathophysiology

Neuroanatomical Basis of Vomiting

The vomiting reflex represents a complex, coordinated response involving multiple central and peripheral nervous system structures. Understanding this neurocircuitry guides rational antiemetic selection based on the underlying etiology.

Vomiting Center (Central Pattern Generator):

Located in the lateral reticular formation of the medulla oblongata, the vomiting center integrates afferent signals from multiple sources and coordinates the motor output required for emesis. This is not a discrete anatomical structure but rather a distributed network of neurons in the nucleus tractus solitarius (NTS) and adjacent reticular formation. The vomiting center receives input from:

1. Chemoreceptor Trigger Zone (CTZ/Area Postrema):

   • Located on floor of fourth ventricle, outside blood-brain barrier
   • Detects circulating toxins, drugs, metabolic abnormalities
   • Rich in dopamine D2, serotonin 5-HT3, neurokinin NK1, and opioid receptors
   • Stimulated by: chemotherapeutic agents, opioids, digoxin, metabolic derangements (uremia, ketoacidosis, hypercalcemia), bacterial toxins

2. Vestibular System (Labyrinthine Apparatus and Vestibular Nuclei):

   • Detects motion, changes in equilibrium
   • Rich in histamine H1 and muscarinic M1 receptors
   • Stimulated by: motion sickness, labyrinthitis, vestibular neuritis, Meniere's disease, posterior fossa tumors
   • Explains efficacy of antihistamines and anticholinergics for motion-related nausea

3. Gastrointestinal Tract (Vagal and Splanchnic Afferents):

   • Mechanoreceptors detect distension, obstruction
   • Chemoreceptors detect mucosal irritation, toxins
   • Primarily vagal (CN X) afferents to NTS
   • Rich in serotonin 5-HT3 receptors on enterochromaffin cells
   • Stimulated by: gastroenteritis, obstruction, gastroparesis, visceral inflammation (appendicitis, cholecystitis, pancreatitis)

4. Cerebral Cortex and Limbic System:

   • Processes anticipatory, psychogenic, and sensory stimuli
   • Activated by: sights, smells, tastes, memories, anxiety, psychiatric disorders
   • Explains anticipatory nausea in chemotherapy patients, psychogenic vomiting

5. Higher Brain Centers:

   • Thalamus, hypothalamus process pain, stress responses
   • Increased intracranial pressure directly stimulates vomiting center
   • Migraine-associated nausea involves cortical spreading depression

Motor Execution Phase:

Once the vomiting center receives sufficient stimulation, it orchestrates a stereotyped motor sequence:

1. Prodromal Phase: Nausea, autonomic activation (salivation, pallor, tachycardia, diaphoresis)
2. Retching: Rhythmic contractions of diaphragm and abdominal muscles against closed glottis
3. Expulsion: Forceful contraction of abdominal muscles with relaxation of lower esophageal sphincter and gastric fundus, generating intragastric pressure up to 100 mmHg
4. Recovery: Restoration of normal gastric motility

Neurotransmitter Systems and Antiemetic Targets:

Pathophysiology of Common Etiologies

Gastroenteritis: Viral or bacterial pathogens damage intestinal epithelium, triggering release of serotonin from enterochromaffin cells. This activates 5-HT3 receptors on vagal afferents, transmitting signals to the NTS. Bacterial enterotoxins (e.g., Staphylococcus aureus, Bacillus cereus) can directly stimulate the CTZ. Intestinal inflammation releases prostaglandins and cytokines that further sensitize mechanoreceptors and chemoreceptors.

Bowel Obstruction: Mechanical distension of the bowel activates stretch receptors and mechanoreceptors. Vagal afferents transmit these signals to the vomiting center. Proximal obstructions (gastric outlet, proximal small bowel) cause earlier and more severe vomiting. Distal obstructions produce feculent vomiting due to bacterial overgrowth and colonic reflux into the ileum. Strangulation compromises blood supply, leading to ischemia, bacterial translocation, and systemic toxicity.

Diabetic Ketoacidosis: Ketone bodies (acetoacetate, β-hydroxybutyrate) directly stimulate the CTZ. Metabolic acidosis, dehydration, and electrolyte abnormalities contribute. Gastroparesis secondary to autonomic neuropathy impairs gastric emptying, exacerbating nausea. The combination of poor oral intake, vomiting, and osmotic diuresis creates a vicious cycle of worsening hyperglycemia and ketogenesis.

Raised Intracranial Pressure: Increased ICP mechanically distorts the floor of the fourth ventricle, directly stimulating the vomiting center and CTZ. Vomiting is often sudden, projectile, and not preceded by nausea. The Cushing reflex (hypertension, bradycardia, irregular respirations) represents late decompensation. Early recognition and treatment prevent herniation syndromes.

Vestibular Disorders: Asymmetric vestibular input (labyrinthitis, vestibular neuritis, Meniere's disease) creates a sensory mismatch that the vestibular nuclei interpret as motion. These nuclei project directly to the vomiting center. Severe vertigo typically accompanies nausea. The HINTS examination (Head Impulse, Nystagmus, Test of Skew) differentiates peripheral from central (stroke) etiologies.

Medication and Toxin-Induced: Opioids stimulate μ-receptors in the CTZ and decrease GI motility. Chemotherapy agents damage intestinal mucosa (releasing serotonin) and directly activate the CTZ. Digoxin toxicity increases vagal tone and stimulates CTZ dopamine receptors. Alcohol causes gastric irritation and acetaldehyde accumulation stimulates the CTZ.

---

Clinical Presentation

History Taking

A thorough, systematic history often narrows the differential diagnosis substantially and guides appropriate investigation.

Onset and Temporal Pattern:

• Sudden onset (less than 1 hour): Consider toxin ingestion, vascular event (mesenteric ischemia, MI), acute obstruction, ruptured viscus
• Gradual onset (hours to days): Infectious gastroenteritis, medication side effect, metabolic derangement, early pregnancy
• Episodic/Cyclical: Cyclic vomiting syndrome (stereotyped episodes separated by symptom-free intervals), cannabinoid hyperemesis syndrome
• Time of day: Morning predominance suggests pregnancy, increased ICP, alcohol withdrawal

Characteristics of Vomitus:

Associated Symptoms - System-Based Approach:

Gastrointestinal:

• Abdominal pain: Location (RUQ cholecystitis, RLQ appendicitis, epigastric pancreatitis, periumbilical early obstruction), character (colicky vs. constant), severity
• Diarrhea: Suggests gastroenteritis (usually concurrent), inflammatory bowel disease; absence with vomiting suggests obstruction
• Constipation/obstipation: No passage of stool or flatus suggests obstruction
• Hematemesis/hematochezia/melena: GI bleeding
• Jaundice: Hepatobiliary pathology

Neurological:

• Headache: Migraine (unilateral, throbbing, photophobia), raised ICP (worse with lying flat, morning predominance, thunderclap), subarachnoid hemorrhage (worst headache of life)
• Vertigo/dizziness: Vestibular disorders, posterior circulation stroke, cerebellar pathology
• Altered mental status: Metabolic encephalopathy (DKA, uremia, hepatic), CNS infection (meningitis, encephalitis), intoxication
• Focal neurological deficits: Stroke, space-occupying lesion, posterior fossa pathology
• Visual changes: Papilledema (raised ICP), scotoma (migraine aura)

Cardiovascular:

• Chest pain: Acute coronary syndrome (inferior MI classically presents with nausea/vomiting), aortic dissection, pericarditis
• Dyspnea: Heart failure, pulmonary embolism
• Palpitations: Arrhythmia-induced hypotension

Genitourinary:

• Amenorrhea: Pregnancy (intrauterine or ectopic)
• Vaginal bleeding: Ectopic pregnancy, threatened abortion
• Dysuria/hematuria: Urinary tract infection, pyelonephritis, nephrolithiasis
• Flank pain: Pyelonephritis, nephrolithiasis, renal infarction

Constitutional:

• Fever: Infection (gastroenteritis, appendicitis, cholecystitis, pyelonephritis, meningitis), inflammatory (IBD)
• Weight loss: Malignancy, gastroparesis, chronic pancreatitis, hyperthyroidism, eating disorder
• Night sweats: Malignancy, tuberculosis, endocarditis

Medication and Substance Use History:

Critical to assess all medications, including:

• Opioids: Morphine, oxycodone, hydrocodone, fentanyl - dose-dependent nausea via CTZ stimulation and decreased GI motility
• Chemotherapy: Cisplatin, cyclophosphamide, doxorubicin - highly emetogenic
• Antibiotics: Macrolides, fluoroquinolones, metronidazole - GI irritation
• Cardiac medications: Digoxin (toxicity), antiarrhythmics
• Psychiatric medications: SSRIs (especially when initiated), lithium toxicity
• Nonsteroidal anti-inflammatory drugs: Gastric irritation, peptic ulcer disease
• Alcohol: Acute intoxication, withdrawal, gastritis, pancreatitis, hepatitis
• Recreational drugs: Cannabis (cannabinoid hyperemesis syndrome), cocaine, amphetamines
• Over-the-counter: Aspirin, iron supplements, multivitamins

Recent Steroid Use: Sudden cessation risks adrenal insufficiency/Addisonian crisis

Pregnancy and Gynecologic History:

• Last menstrual period (possibility of pregnancy)
• Previous pregnancies and complications
• Contraception use
• Sexual activity and possibility of ectopic pregnancy

Past Medical History:

• Diabetes mellitus: DKA, gastroparesis, increased infection risk
• Chronic kidney disease: Uremia, medication accumulation
• Prior abdominal surgery: Adhesion-related obstruction (70% of small bowel obstructions)
• Malignancy: Chemotherapy side effects, bowel obstruction, hypercalcemia, brain metastases
• Psychiatric disorders: Eating disorders (bulimia, rumination syndrome), anxiety, cyclic vomiting syndrome
• Migraine history: Recurrent migraine-associated nausea
• Cardiovascular disease: MI risk

Social and Travel History:

• Recent travel: Infectious gastroenteritis (traveler's diarrhea), tropical diseases
• Sick contacts: Viral gastroenteritis clusters
• Food exposure: Food poisoning (onset less than 6 hours suggests preformed toxin from Staphylococcus aureus or Bacillus cereus)
• Occupational exposures: Toxins, radiation
• Cannabis use: Cannabinoid hyperemesis syndrome (compulsive hot bathing behavior pathognomonic)

Physical Examination

General Appearance and Vital Signs:

• Overall appearance: Toxic-appearing, distressed, lethargic, cachexic
• Vital signs interpretation:
  • "Tachycardia: Dehydration, pain, anxiety, infection, heart failure, pulmonary embolism"
  • "Hypotension: Severe dehydration, GI bleeding, sepsis, adrenal crisis, cardiogenic shock"
  • "Fever: Infection, inflammation"
  • "Tachypnea: Metabolic acidosis (Kussmaul respirations in DKA), pulmonary embolism, pneumonia"
  • "Hypertension with bradycardia: Cushing reflex (raised ICP)"

Hydration Status Assessment:

Orthostatic vital signs (if safe to perform): Positive if heart rate increases ≥30 bpm or systolic BP decreases ≥20 mmHg (or diastolic ≥10 mmHg) within 3 minutes of standing; indicates ≥15% volume loss (≥1 liter in 70 kg adult).

Abdominal Examination:

Systematic approach essential to identify surgical emergencies:

1. Inspection:

   • Distension: Obstruction, ascites, organomegaly, pregnancy
   • Surgical scars: Previous surgery increases adhesion risk (70% of small bowel obstructions in patients with prior laparotomy)
   • Visible peristalsis: Bowel obstruction
   • Ecchymosis: Cullen's sign (periumbilical) or Grey Turner's sign (flank) suggest retroperitoneal hemorrhage (pancreatitis, ruptured AAA)

2. Auscultation (before palpation):

   • High-pitched, tinkling bowel sounds with rushes: Early obstruction
   • Absent bowel sounds: Ileus, peritonitis, late obstruction
   • Succussion splash: Gastric outlet obstruction, gastroparesis

3. Percussion:

   • Tympany: Bowel obstruction, gaseous distension
   • Shifting dullness: Ascites
   • Loss of liver dullness: Perforated viscus (free air)

4. Palpation:

   • Tenderness localization:
     • Right upper quadrant: Cholecystitis (Murphy's sign), hepatitis, liver abscess, right lower lobe pneumonia, Fitz-Hugh-Curtis syndrome
     • Epigastric: Pancreatitis, peptic ulcer disease, gastritis, MI, AAA
     • Right lower quadrant: Appendicitis (McBurney's point, Rovsing's sign), ectopic pregnancy, ovarian torsion, ruptured ovarian cyst
     • Left lower quadrant: Diverticulitis, ectopic pregnancy, ovarian pathology
     • Periumbilical migrating to RLQ: Classic appendicitis pattern
   • Rebound tenderness, guarding, rigidity: Peritonitis (surgical abdomen)
   • Pulsatile mass: Abdominal aortic aneurysm
   • Hernia orifices: Incarcerated or strangulated hernia (inguinal, femoral, umbilical, incisional)

Neurological Examination:

Focused assessment for CNS causes:

• Mental status: Glasgow Coma Scale, orientation, attention
• Cranial nerves: Pupillary responses (asymmetry suggests herniation), extraocular movements, facial symmetry
• Fundoscopy: Papilledema (raised ICP - blurred disc margins, loss of venous pulsations, disc elevation)
• Motor/sensory: Focal deficits suggest stroke, space-occupying lesion
• Cerebellar: Finger-to-nose, heel-to-shin, gait (if safe) - ataxia suggests posterior fossa pathology
• Meningismus: Nuchal rigidity, Kernig's sign, Brudzinski's sign (meningitis, subarachnoid hemorrhage)
• HINTS examination (for acute vestibular syndrome with nystagmus):
  • "Head Impulse test: Corrective saccade indicates peripheral lesion (safe); absence suggests central (stroke)"
  • "Nystagmus: Unidirectional horizontal nystagmus = peripheral; direction-changing or vertical = central"
  • "Test of Skew: Vertical ocular misalignment = central"

Cardiovascular Examination:

• Jugular venous pressure: Low in dehydration, elevated in heart failure
• Heart sounds: Murmurs, S3 gallop (heart failure), irregular rhythm (atrial fibrillation - mesenteric ischemia risk)
• Peripheral pulses: Assess perfusion, vascular disease

Ear, Nose, Throat Examination:

• Pharyngitis: Streptococcal pharyngitis can cause nausea
• Dental pathology: Abscess, referred pain
• Otoscopy: Acute otitis media (children), cholesteatoma

Pelvic Examination (when indicated):

• Pregnancy-related complications: Ectopic pregnancy (adnexal mass, cervical motion tenderness), ovarian torsion
• Pelvic inflammatory disease
• Cervical dilation (threatened/inevitable abortion)

---

Red Flags and Emergency Presentations

Critical Warning Signs Requiring Immediate Action

---

Differential Diagnosis by System

Gastrointestinal Causes

Infectious Gastroenteritis (Most Common Overall):

Viral (60-70% of acute gastroenteritis):

• Norovirus, rotavirus, adenovirus, astrovirus
• Presentation: Acute onset nausea, vomiting, watery diarrhea, low-grade fever, abdominal cramping
• Transmission: Fecal-oral, highly contagious (cruise ships, nursing homes, schools)
• Duration: Self-limited, 24-72 hours
• Management: Supportive care, oral rehydration, antiemetics

Bacterial:

• Toxin-mediated (rapid onset less than 6 hours): Staphylococcus aureus, Bacillus cereus - severe vomiting predominates
• Invasive (onset 12-72 hours): Salmonella, Campylobacter, Shigella, E. coli - diarrhea predominates, fever common
• Clostridium difficile: Recent antibiotic exposure, profuse watery diarrhea

Food Poisoning:

• Scombroid (histamine): Onset minutes, flushing, headache
• Ciguatera: Large reef fish, neurological symptoms (paresthesias)

Bowel Obstruction:

Small Bowel Obstruction (80% of obstructions):

• Causes: Adhesions (70%), hernias (15%), malignancy (5%), Crohn's disease (3%), volvulus
• Presentation: Colicky periumbilical pain, bilious vomiting (proximal) or feculent vomiting (distal), abdominal distension, high-pitched bowel sounds, absence of flatus
• Complications: Closed-loop obstruction risks strangulation → ischemia → perforation
• Imaging: CT abdomen/pelvis shows transition point, dilated proximal bowel (>3 cm small bowel), air-fluid levels
• Management: NPO, NG decompression, IV fluids, surgical consultation (surgery if strangulation, peritonitis, or failed conservative management)

Large Bowel Obstruction (20% of obstructions):

• Causes: Colorectal cancer (60%), diverticulitis (20%), volvulus (cecal or sigmoid)
• Presentation: Constipation more prominent than vomiting, progressive distension
• Imaging: Cecal diameter >12 cm indicates impending perforation
• Management: Surgical consultation, cecal volvulus and closed-loop obstructions require emergent surgery

Acute Appendicitis:

• Presentation: Periumbilical pain migrating to RLQ, anorexia, nausea, low-grade fever, rebound tenderness at McBurney's point
• Alvarado score: Migration of pain, anorexia, nausea/vomiting, RLQ tenderness, rebound, fever, leukocytosis, left shift
• Imaging: CT abdomen/pelvis (sensitivity 94%, specificity 95%) shows dilated appendix >6mm, periappendiceal fat stranding, appendicolith
• Complications: Perforation (20% at presentation), abscess formation
• Management: Surgical consultation, antibiotics (cefoxitin or ceftriaxone + metronidazole), appendectomy vs. antibiotics-first approach

Acute Cholecystitis:

• Presentation: RUQ pain (often postprandial), nausea, vomiting, fever, Murphy's sign (inspiratory arrest with RUQ palpation)
• Labs: Leukocytosis, elevated alkaline phosphatase and bilirubin (if choledocholithiasis)
• Imaging: RUQ ultrasound (gallstones, gallbladder wall thickening >4mm, pericholecystic fluid, sonographic Murphy's sign)
• Complications: Gangrenous cholecystitis, emphysematous cholecystitis (diabetics), perforation, cholangitis
• Management: NPO, IV fluids, antibiotics (ceftriaxone + metronidazole), cholecystectomy within 72 hours

Acute Pancreatitis:

• Causes: Gallstones (45%), alcohol (35%), hypertriglyceridemia (4%), medications (azathioprine, valproic acid, furosemide)
• Presentation: Severe epigastric pain radiating to back, nausea, vomiting, fever
• Diagnosis: Lipase >3× upper limit normal (sensitivity 85-95%), CT abdomen/pelvis (after 48-72 hours to assess necrosis)
• Ranson criteria and APACHE II predict severity
• Complications: Pancreatic necrosis, pseudocyst, ARDS, shock
• Management: NPO, aggressive IV fluid resuscitation (250-500 mL/hr crystalloid), analgesia, ERCP if biliary obstruction

Peptic Ulcer Disease:

• Presentation: Epigastric pain (duodenal ulcer improves with food, gastric ulcer worsens), nausea, bleeding (hematemesis, melena)
• Risk factors: H. pylori, NSAIDs, smoking, alcohol
• Complications: Perforation (sudden severe pain, peritonitis, pneumoperitoneum), bleeding, gastric outlet obstruction
• Management: PPI (pantoprazole 40mg IV BID), H. pylori eradication if positive, EGD if bleeding or refractory

Gastroparesis:

• Causes: Diabetic autonomic neuropathy (30%), post-viral (20%), idiopathic (35%)
• Presentation: Chronic nausea, early satiety, postprandial vomiting of undigested food, bloating
• Diagnosis: Gastric emptying scintigraphy (>10% retention at 4 hours)
• Management: Dietary modification (small, frequent, low-fat meals), prokinetics (metoclopramide), antiemetics

Hepatitis:

• Viral (A, B, C, E), alcoholic, drug-induced (acetaminophen), autoimmune
• Presentation: RUQ pain, nausea, vomiting, jaundice, dark urine, hepatomegaly
• Labs: Elevated transaminases (AST, ALT), bilirubin, prolonged PT/INR if severe
• Management: Supportive care, specific antiviral therapy (e.g., tenofovir for HBV), N-acetylcysteine for acetaminophen toxicity

Central Nervous System Causes

Raised Intracranial Pressure:

• Causes: Brain tumor, intracranial hemorrhage (subdural, epidural, subarachnoid, intraparenchymal), hydrocephalus, cerebral edema, idiopathic intracranial hypertension (pseudotumor cerebri)
• Presentation: Headache (worse morning, lying flat, Valsalva), projectile vomiting (often without nausea), papilledema, altered mental status, Cushing triad (late: hypertension, bradycardia, irregular respirations)
• Diagnosis: Non-contrast CT head, MRI brain (more sensitive), LP opening pressure (contraindicated if mass lesion)
• Management: Head elevation 30°, avoid hypotension (maintain CPP >60 mmHg), osmotic therapy (mannitol 0.25-1 g/kg IV or hypertonic saline 3% 250 mL bolus), hyperventilation (target PaCO2 30-35 mmHg) if impending herniation, neurosurgical consultation

Migraine:

• Presentation: Unilateral throbbing headache, photophobia, phonophobia, nausea, vomiting, aura (visual, sensory, motor) in 25%
• Triggers: Stress, foods (chocolate, cheese, wine), hormonal changes, sleep deprivation
• Management: Dark, quiet environment; NSAIDs (ibuprofen 400-800mg, ketorolac 30mg IV), antiemetics (metoclopramide 10mg IV, prochlorperazine 10mg IV - also abortive), triptans (sumatriptan 6mg SC), IV fluids, consider dexamethasone 10mg IV to prevent recurrence

Vestibular Neuritis/Labyrinthitis:

• Presentation: Acute severe vertigo (room-spinning), nausea, vomiting, nystagmus, gait instability; labyrinthitis includes hearing loss
• Differentiation from stroke: HINTS examination (peripheral = positive head impulse test, unidirectional horizontal nystagmus, no skew deviation)
• Management: Antihistamines (meclizine 25mg PO TID), antiemetics, benzodiazepines (lorazepam 0.5-1mg), vestibular rehabilitation, corticosteroids if early

Meningitis/Encephalitis:

• Presentation: Fever, headache, nuchal rigidity, altered mental status, nausea, vomiting, photophobia, Kernig/Brudzinski signs
• Diagnosis: LP (CSF analysis: cell count, glucose, protein, Gram stain, culture, PCR for HSV/enterovirus)
• Management: Empiric antibiotics immediately after blood cultures (ceftriaxone 2g IV + vancomycin 15-20mg/kg IV), add ampicillin if >50 years or immunocompromised (Listeria coverage), acyclovir 10mg/kg IV if encephalitis suspected, dexamethasone 10mg IV before or with first antibiotic dose

Acute Stroke (Posterior Circulation):

• Vertebrobasilar strokes present with vertigo, nausea, vomiting, ataxia, cranial nerve deficits
• HINTS examination helps differentiate from peripheral vertigo
• Management: Stroke protocol, neurology consultation, thrombolysis if within window and no contraindications

Metabolic and Endocrine Causes

Diabetic Ketoacidosis:

• Presentation: Polyuria, polydipsia, nausea, vomiting, abdominal pain ("pseudoperitonitis"), Kussmaul respirations, fruity breath, altered mental status
• Diagnostic criteria: Glucose >250 mg/dL, pH less than 7.3, bicarbonate less than 18 mEq/L, anion gap >10, positive ketones
• Precipitants: Infection (40%), medication non-compliance (25%), new-onset diabetes (15%), MI, pancreatitis
• Management: Aggressive IV fluid resuscitation (1-2L NS bolus, then 250-500 mL/hr), IV insulin infusion (0.1 units/kg/hr after initial bolus), potassium replacement (goal 4-5 mEq/L), identify and treat precipitant, monitor glucose hourly, transition to subcutaneous insulin when anion gap closes

Hypercalcemia:

• Causes: Malignancy (PTHrP from solid tumors, multiple myeloma), primary hyperparathyroidism, vitamin D toxicity, granulomatous disease
• Presentation: "Stones, bones, groans, psychiatric overtones"
• nausea, vomiting, constipation, confusion, weakness, polyuria
• Diagnosis: Corrected calcium >12 mg/dL (add 0.8 mg/dL for each 1 g/dL albumin below 4 g/dL)
• Management: IV normal saline (200-300 mL/hr), furosemide after euvolemia, bisphosphonates (zoledronic acid 4mg IV), calcitonin 4 units/kg SC for rapid effect, dialysis if severe (Ca >18 mg/dL) or renal failure

Acute Kidney Injury/Uremia:

• Presentation: Nausea, vomiting, altered mental status, fatigue, pruritus, pericarditis, uremic frost (late)
• Labs: Elevated BUN and creatinine, hyperkalemia, metabolic acidosis, uremic toxins
• Management: Identify and treat cause (prerenal, intrinsic renal, postrenal obstruction), fluid resuscitation if prerenal, nephrology consultation, dialysis if severe (refractory hyperkalemia, acidosis, volume overload, uremic pericarditis)

Adrenal Insufficiency/Addisonian Crisis:

• Presentation: Nausea, vomiting, abdominal pain, hypotension refractory to fluids, hyperpigmentation (chronic), weakness, altered mental status
• Precipitants: Infection, surgery, trauma, abrupt steroid cessation
• Labs: Hyponatremia, hyperkalemia, hypoglycemia, eosinophilia
• Diagnosis: Random cortisol less than 18 μg/dL suggests insufficiency; ACTH stimulation test confirmatory but don't delay treatment
• Management: Hydrocortisone 100mg IV immediately (mineralocorticoid activity at high doses), aggressive IV normal saline resuscitation (1-2L bolus), dextrose if hypoglycemic, identify and treat precipitant

Hyperthyroidism/Thyroid Storm:

• Presentation: Nausea, vomiting, diarrhea, fever, tachycardia, atrial fibrillation, tremor, agitation, heart failure
• Labs: Suppressed TSH, elevated free T4 and T3
• Management: Propylthiouracil 500-1000mg loading dose (blocks synthesis and peripheral conversion), beta-blocker (propranolol 1-2mg IV), hydrocortisone 100mg IV, iodine (1 hour after PTU), supportive care

Pregnancy-Related:

• Hyperemesis gravidarum: Severe nausea/vomiting preventing adequate oral intake, weight loss >5%, ketonuria, dehydration; presents first trimester; management includes IV fluids, antiemetics (ondansetron, metoclopramide), thiamine supplementation (prevent Wernicke's), pyridoxine 25mg TID + doxylamine 25mg QHS
• Acute fatty liver of pregnancy: Third trimester, nausea, vomiting, jaundice, abdominal pain, elevated transaminases, hypoglycemia, coagulopathy, encephalopathy; emergent delivery required
• HELLP syndrome: Hemolysis, Elevated Liver enzymes, Low Platelets; third trimester preeclampsia complication; delivery required

Medications and Toxins

Opioids:

• Mechanism: μ-receptor stimulation of CTZ, decreased GI motility
• Management: Antiemetics (ondansetron first-line), consider dose reduction, opioid rotation

Chemotherapy:

• Highly emetogenic: Cisplatin, cyclophosphamide, doxorubicin
• Prophylaxis: 5-HT3 antagonist (ondansetron, palonosetron) + dexamethasone + NK1 antagonist (aprepitant)

Alcohol:

• Acute intoxication: Direct gastric irritation, CNS effects
• Withdrawal: Autonomic hyperactivity, tremor, seizures
• Chronic: Alcoholic gastritis, pancreatitis, hepatitis
• Wernicke encephalopathy: Thiamine deficiency (ataxia, ophthalmoplegia, confusion); prevent with thiamine 500mg IV before dextrose

Cannabinoid Hyperemesis Syndrome:

• Paradoxical vomiting with chronic cannabis use (daily for months to years)
• Pathognomonic: Compulsive hot bathing behavior (temporary relief)
• Phases: Prodromal (morning nausea), hyperemetic (persistent vomiting, dehydration), recovery (resolution with abstinence)
• Management: Cannabis cessation (only definitive treatment), supportive care, capsaicin cream (topical), haloperidol 5mg IV (most effective antiemetic)

Digoxin Toxicity:

• Presentation: Nausea, vomiting, visual changes (yellow-green halos), arrhythmias (PVCs, heart block)
• Diagnosis: Digoxin level >2 ng/mL, hyperkalemia
• Management: Digoxin-specific antibody fragments (Digibind), atropine for bradycardia, avoid calcium (worsens cardiotoxicity)

Acetaminophen Overdose:

• Phases: Phase I (0.5-24h) nausea, vomiting; Phase II (24-72h) RUQ pain, transaminitis; Phase III (72-96h) hepatic failure; Phase IV (4d-2wk) recovery or death
• Management: N-acetylcysteine (within 8 hours optimal), activated charcoal if less than 4 hours

Cardiac Causes

Acute Myocardial Infarction (Especially Inferior Wall):

• Inferior STEMI (RCA occlusion) activates vagal afferents, causing nausea, vomiting, bradycardia
• Presentation: Chest pain, diaphoresis, dyspnea, nausea; ECG shows ST elevation in leads II, III, aVF
• Management: Aspirin 325mg chewed, DAPT, anticoagulation, emergent PCI, avoid beta-blockers if RV involvement (reciprocal ST depression V1-V2)

Acute Heart Failure:

• Presentation: Dyspnea, orthopnea, edema, nausea, hepatic congestion (RUQ pain)
• Management: Diuretics, vasodilators, treat underlying cause

Psychiatric and Functional Disorders

Cyclic Vomiting Syndrome:

• Rome IV criteria: Stereotyped episodes of vomiting (onset, duration, frequency), separated by symptom-free intervals (weeks to months)
• Migraine association common (80%)
• Management: Prophylaxis (amitriptyline, propranolol), abortive (triptans, antiemetics), IV fluids during episodes

Eating Disorders:

• Bulimia nervosa: Self-induced vomiting, parotid enlargement, dental erosion, hypokalemia, metabolic alkalosis
• Rumination syndrome: Effortless regurgitation and re-chewing

Psychogenic Vomiting:

• Diagnosis of exclusion
• Often associated with anxiety, depression, somatization disorder
• Management: Reassurance, psychiatric referral, CBT

---

Diagnostic Approach and Investigations

Risk Stratification

Initial assessment determines investigation intensity:

Low Risk (likely benign, self-limited):

• Young, healthy patient
• Classic viral gastroenteritis presentation
• No red flags
• Adequate hydration
• Normal vital signs
• Benign abdominal exam
• Management: Minimal or no testing, symptomatic treatment, discharge with precautions

Moderate Risk:

• Uncertain diagnosis
• Moderate dehydration
• Comorbidities (diabetes, elderly)
• Persistent symptoms despite treatment
• Management: Targeted laboratory testing (BMP, CBC, lipase if indicated), consider imaging, treat underlying cause, discharge vs. observation

High Risk (likely serious pathology):

• Any red flag present
• Hemodynamic instability
• Severe dehydration
• Peritoneal signs
• Altered mental status
• Significant comorbidities
• Management: Comprehensive workup, imaging, specialist consultation, admission

Laboratory Investigations

Basic Metabolic Panel (Most useful initial test):

• Sodium: Hyponatremia (SIADH, adrenal insufficiency, excess free water), hypernatremia (dehydration)
• Potassium: Hypokalemia (vomiting, diarrhea - concerning for arrhythmias), hyperkalemia (adrenal insufficiency, AKI)
• Chloride: Hypochloremia with metabolic alkalosis (persistent vomiting)
• Bicarbonate: Low in DKA, high in metabolic alkalosis from vomiting
• BUN/Creatinine: Elevated in dehydration (BUN:Cr ratio >20:1 suggests prerenal), AKI
• Glucose: Hyperglycemia (DKA, HHS), hypoglycemia (adrenal insufficiency, insulinoma, alcohol)
• Anion gap: Elevated in DKA, lactic acidosis, uremia, toxins (methanol, ethylene glycol, salicylates)

Complete Blood Count:

• WBC: Leukocytosis (infection, inflammation), leukopenia (viral, severe sepsis)
• Hemoglobin/Hematocrit: Anemia (GI bleeding), hemoconcentration (dehydration)
• Platelets: Thrombocytopenia (HELLP syndrome, DIC, sepsis)

Liver Function Tests:

• Transaminases (AST, ALT): Hepatitis, cholecystitis, medication toxicity
• Alkaline phosphatase: Cholestasis, biliary obstruction
• Bilirubin: Hepatobiliary disease, hemolysis
• Albumin: Chronic liver disease, malnutrition

Pancreatic Enzymes:

• Lipase: More specific than amylase for pancreatitis; >3× ULN diagnostic (sensitivity 85-95%)
• Amylase: Less specific (elevated in salivary disease, renal failure, ectopic pregnancy)

Urinalysis:

• Ketones: DKA, starvation ketosis, alcoholic ketoacidosis
• Leukocyte esterase/nitrites: UTI, pyelonephritis
• Specific gravity: Dehydration (>1.020), diabetes insipidus (less than 1.005)
• Protein: Preeclampsia, renal disease
• Myoglobin: Rhabdomyolysis

Pregnancy Testing:

• Quantitative β-hCG: Mandatory in all women of childbearing age
• Levels: less than 1500 mIU/mL suggests early pregnancy, >1500 mIU/mL without intrauterine pregnancy on ultrasound suggests ectopic
• Doubling time: Normally doubles every 48-72 hours in early pregnancy

Cardiac Biomarkers:

• Troponin I or T: Myocardial infarction (at presentation and 3 hours)
• BNP/NT-proBNP: Heart failure

Additional Tests (Targeted):

• Lactate: Mesenteric ischemia (>2 mmol/L concerning), sepsis
• Cortisol (random): Adrenal insufficiency (AM cortisol less than 3 μg/dL diagnostic, >18 μg/dL rules out)
• Thyroid function tests: Hyperthyroidism, hypothyroidism
• Digoxin level: Toxicity (therapeutic 0.5-2 ng/mL, toxic >2 ng/mL)
• Toxicology screen: Suspected ingestion
• Serum/urine ketones: β-hydroxybutyrate most specific for DKA
• Calcium (corrected): Hypercalcemia
• Magnesium: Hypomagnesemia exacerbates hypokalemia
• Phosphate: Refeeding syndrome, DKA treatment

Imaging Studies

Plain Radiography:

Abdominal X-ray (KUB + Upright):

• Indications: Suspected obstruction, perforation, foreign body
• Findings:
  • "Bowel obstruction: Dilated bowel loops (small bowel >3 cm, large bowel >6 cm, cecum >9 cm), air-fluid levels (upright or decubitus), absence of colonic gas"
  • "Perforation: Free air under diaphragm (upright CXR more sensitive)"
  • Volvulus: "Coffee bean" sign (sigmoid volvulus), cecal volvulus
  • "Appendicolith: Visible in 10% of appendicitis cases"
• Limitations: Sensitivity 50-80% for obstruction, poor for solid organ pathology

Chest X-ray:

• Free air under diaphragm: Perforated viscus
• Pneumonia (especially RLL): Can cause referred abdominal pain and vomiting
• Aspiration pneumonia: Complication of vomiting

Computed Tomography:

CT Abdomen/Pelvis with IV Contrast:

• Gold standard for acute abdomen workup
• Indications: Undifferentiated abdominal pain with vomiting, suspected obstruction, appendicitis, diverticulitis, pancreatitis, malignancy
• Bowel obstruction: Sensitivity 95%, specificity 96%; identifies transition point, closed-loop obstruction, ischemia (bowel wall thickening, pneumatosis, portal venous gas)
• Appendicitis: Sensitivity 94%, specificity 95%; shows dilated appendix >6 mm, appendicolith, periappendiceal fat stranding
• Pancreatitis: Peripancreatic inflammation, fluid collections, necrosis (best assessed 48-72 hours after onset)
• Cholecystitis: Gallstones, gallbladder wall thickening >4 mm, pericholecystic fluid
• Oral contrast: Not routinely needed, may delay diagnosis, contraindicated if aspiration risk

CT Head Non-Contrast:

• Indications: Severe headache, altered mental status, focal neurological deficits, suspected raised ICP
• Findings: Hemorrhage (hyper-dense), mass lesion, hydrocephalus, cerebral edema, midline shift
• Limitations: Poor sensitivity for early ischemic stroke (MRI superior), subarachnoid hemorrhage (sensitivity decreases with time - LP required if high suspicion and negative CT)

CT Angiography:

• Mesenteric ischemia: CTA abdomen/pelvis shows arterial occlusion, venous thrombosis
• Aortic dissection: CTA chest/abdomen/pelvis shows intimal flap, false lumen
• Pulmonary embolism: CTPA shows filling defects in pulmonary arteries

Ultrasonography:

Right Upper Quadrant Ultrasound:

• First-line for cholecystitis: Sensitivity 88%, specificity 80%; shows gallstones, gallbladder wall thickening >4 mm, pericholecystic fluid, sonographic Murphy's sign
• Biliary duct dilation: Choledocholithiasis (common bile duct >6 mm)

Transvaginal Ultrasound:

• Ectopic pregnancy: Absence of intrauterine pregnancy with β-hCG >1500 mIU/mL (discriminatory zone)
• Ovarian torsion: Enlarged ovary, absent Doppler flow
• Tubo-ovarian abscess: Complex adnexal mass

Point-of-Care Ultrasound (POCUS):

• IVC collapsibility: Assess volume status (>50% collapsibility suggests hypovolemia)
• FAST exam: Free fluid in abdomen (ruptured ectopic, hemorrhage, ascites)
• Cardiac: Global function, pericardial effusion

Magnetic Resonance Imaging:

• Indications: Pregnant patients (avoid radiation), CNS pathology (more sensitive than CT for stroke, posterior fossa lesions, encephalitis), hepatobiliary disease (MRCP for choledocholithiasis)
• Limitations: Time-consuming, expensive, limited availability, requires patient cooperation

Electrocardiography

Indications:

• All patients >40 years with nausea/vomiting
• Cardiac risk factors
• Chest pain, dyspnea
• Electrolyte abnormalities (hypokalemia, hypercalcemia)
• Before administering QT-prolonging antiemetics (ondansetron, droperidol)

Key Findings:

• Acute MI: ST elevation (STEMI), ST depression, T wave inversion, new LBBB; inferior MI (II, III, aVF) commonly presents with nausea
• Electrolyte abnormalities: Peaked T waves (hyperkalemia), flattened T waves and U waves (hypokalemia), shortened QT (hypercalcemia)
• Arrhythmias: Atrial fibrillation (mesenteric ischemia risk)
• QT prolongation: Baseline before antiemetics, drug toxicity

Lumbar Puncture

Indications:

• Suspected meningitis, encephalitis, subarachnoid hemorrhage (after negative CT)

Contraindications:

• Mass lesion on CT (herniation risk)
• Coagulopathy (INR >1.5, platelets less than 50,000)
• Infection at puncture site
• Hemodynamic instability

CSF Analysis:

• Bacterial meningitis: WBC >1000 (PMN predominance), glucose less than 40 mg/dL (or less than 50% serum), protein >200 mg/dL, positive Gram stain/culture
• Viral meningitis: WBC 10-1000 (lymphocyte predominance), normal glucose, protein 50-100 mg/dL
• Subarachnoid hemorrhage: RBCs, xanthochromia (after centrifugation)

---

Management

General Principles

1. Exclude life-threatening causes first: Systematic assessment for red flags
2. Resuscitation before diagnosis: Airway protection if altered mental status, IV access, fluid resuscitation if dehydrated, correct hypoglycemia/electrolyte abnormalities
3. Correct dehydration: Most important intervention for uncomplicated gastroenteritis
4. Antiemetics for symptomatic relief: Choose based on mechanism and patient factors
5. Treat underlying cause definitively: Antiemetics alone insufficient
6. Prevent complications: Aspiration, electrolyte disturbances, Mallory-Weiss tear, Boerhaave syndrome

Fluid Resuscitation

Assessment of Deficit:

• Mild (3-5%): ~2-3 liters in 70 kg adult
• Moderate (6-9%): ~4-6 liters
• Severe (≥10%): ≥7 liters

Oral Rehydration Therapy (Preferred if tolerated):

• Indications: Mild-moderate dehydration, able to tolerate oral fluids, no red flags
• WHO oral rehydration solution: Glucose-electrolyte solution (enhances sodium-glucose cotransport in intestine)
• Technique: Small, frequent sips (5-10 mL every 5-10 minutes), gradually increase
• Goal: 50-100 mL/kg over 4 hours
• Evidence: Equally effective as IV hydration for mild-moderate dehydration, faster ED discharge, lower cost

Intravenous Fluid Therapy:

• Indications: Moderate-severe dehydration, unable to tolerate oral (persistent vomiting, altered mental status), hemodynamic instability, electrolyte abnormalities requiring correction

Crystalloid Choice:

• Normal Saline (0.9% NaCl): First-line for most patients, especially DKA, hypochloremic metabolic alkalosis; risk of hyperchloremic metabolic acidosis with large volumes
• Lactated Ringer's: Balanced solution, preferred for large-volume resuscitation (>3-4 liters), hemorrhagic shock; avoid in hyperkalemia (contains 4 mEq/L potassium)
• Dextrose-containing fluids: Add D5 to maintenance fluids once euvolemic; avoid in hyperglycemia

Resuscitation Protocol:

1. Bolus: 1-2 liters (or 20 mL/kg) NS or LR over 1-2 hours
2. Reassess: Vital signs, urine output, exam
3. Maintenance: 100-200 mL/hour, adjust based on response
4. Monitor: Urine output (goal >0.5 mL/kg/hr), electrolytes (repeat BMP after 1-2 L), fluid balance

Special Populations:

• Heart failure: Cautious fluid administration, consider furosemide
• Renal failure: Avoid excessive potassium, monitor fluid balance closely
• Elderly: Reduced cardiovascular reserve, frequent reassessment

Antiemetic Pharmacotherapy

Selection Algorithm:

Combination Therapy: Evidence supports combining antiemetics with different mechanisms:

• Ondansetron + Metoclopramide: Synergistic effect
• Ondansetron + Dexamethasone: Standard for chemotherapy-induced nausea
• Antiemetic + Benzodiazepine: If anxiety component

Adverse Effects and Precautions:

Ondansetron:

• QT prolongation: Risk highest with IV doses >16 mg (now contraindicated); monitor ECG if baseline QT prolongation or concurrent QT-prolonging drugs
• Constipation: Especially problematic in opioid-treated patients
• Serotonin syndrome: Theoretical risk when combined with other serotonergic agents (SSRIs, SNRIs, MAOIs, linezolid, methylene blue)
• Pregnancy: Generally considered safe; some studies suggest small increased risk of cleft palate with first-trimester exposure (absolute risk less than 1%)

Metoclopramide:

• BLACK BOX WARNING: Tardive dyskinesia (irreversible involuntary movements) with chronic use (>12 weeks) or high doses
• Extrapyramidal symptoms (EPS): Acute dystonia (4-15% incidence), akathisia, parkinsonism; higher risk in young females, elderly, higher doses
• EPS treatment: Diphenhydramine 50 mg IV or benztropine 1-2 mg IV
• Contraindications: Bowel obstruction (prokinetic increases perforation risk), Parkinson's disease, pheochromocytoma, seizure disorder
• Neuroleptic malignant syndrome: Rare but life-threatening (fever, rigidity, autonomic instability, elevated CK)

Prochlorperazine:

• Extrapyramidal symptoms: Similar to metoclopramide but less prokinetic effect
• Sedation: Moderate
• Anticholinergic effects: Dry mouth, urinary retention, blurred vision

Promethazine:

• Beers Criteria: Avoid in elderly (high anticholinergic burden, sedation, delirium risk)
• Severe sedation: Impairs discharge safety
• IV administration: Tissue necrosis risk (extravasation), severe pain - use large vein, dilute, slow push
• Respiratory depression: Especially in combination with opioids
• Contraindications: Children less than 2 years (respiratory depression), concomitant MAOIs

Droperidol:

• BLACK BOX WARNING: QT prolongation and torsades de pointes (incidence very low at antiemetic doses 0.625-1.25 mg)
• Requirements: ECG before and 2-3 hours after administration, continuous cardiac monitoring
• Availability: Removed from many formularies due to regulatory burden despite excellent efficacy
• Sedation: Mild at antiemetic doses

Haloperidol:

• QT prolongation: Lower risk than droperidol at antiemetic doses
• Extrapyramidal symptoms: Dose-dependent
• Particularly effective for cannabinoid hyperemesis syndrome

Antihistamines (Diphenhydramine, Meclizine):

• Sedation: Significant with diphenhydramine, less with meclizine
• Anticholinergic effects: Dry mouth, urinary retention, constipation, blurred vision, confusion/delirium (especially elderly)
• Paradoxical excitation: Rare, more common in children and elderly

Dexamethasone:

• Hyperglycemia: Monitor in diabetics
• Insomnia: Dose in morning if possible
• GI irritation: Usually not an issue with single dose
• Immunosuppression: Avoid in active infection

Scopolamine:

• Anticholinergic effects: Dry mouth, urinary retention, blurred vision, confusion (especially elderly)
• CNS effects: Drowsiness, dizziness
• Delayed onset: 4-6 hours for patch, not useful for acute treatment

Non-Pharmacological Management

Supportive Measures:

• NPO initially if severe vomiting or surgical abdomen suspected
• Gradual oral intake: Start with small sips of clear liquids (water, ice chips, electrolyte solutions), advance as tolerated
• BRAT diet: Bananas, Rice, Applesauce, Toast (bland, low-fiber, easily digestible); transition to regular diet as tolerated
• Avoid irritants: Spicy, fatty, acidic foods; alcohol; caffeine
• Upright positioning: 30-45° head elevation reduces aspiration risk
• Quiet, dark environment: Especially for migraine

Nasogastric Tube Decompression:

• Indications: Bowel obstruction, severe gastroparesis, intractable vomiting with aspiration risk
• Technique: Salem sump or single-lumen tube, confirm placement (auscultation, X-ray), low intermittent suction
• Complications: Epistaxis, esophageal trauma, aspiration during placement, sinusitis (prolonged use)

Airway Protection:

• High-risk patients: Altered mental status, severe intoxication, neuromuscular disorders
• Positioning: Left lateral decubitus (recovery position) reduces aspiration
• Intubation: Consider if GCS ≤8, refractory vomiting with aspiration, hematemesis with airway compromise

Electrolyte Correction:

Hypokalemia (Most common with vomiting):

• Mild (3.0-3.5 mEq/L): Oral replacement (KCl 20-40 mEq PO)
• Moderate (2.5-3.0 mEq/L): IV replacement (KCl 10-20 mEq/hr via peripheral line, up to 40 mEq/hr via central line)
• Severe (less than 2.5 mEq/L) or symptomatic (arrhythmias, weakness): 10-20 mEq/hr, cardiac monitoring, frequent reassessment
• Correct hypomagnesemia concurrently (refractory hypokalemia if Mg low)

Metabolic Alkalosis:

• Caused by loss of HCl in gastric secretions, volume contraction (contraction alkalosis)
• Treatment: IV normal saline (chloride repletes, volume expands), correct hypokalemia
• Severe (pH >7.55): Rare with vomiting alone, consider acetazolamide 250-500 mg IV if refractory

Hyponatremia:

• Free water excess: Restrict free water
• Hypovolemic hyponatremia: NS resuscitation
• Severe (less than 120 mEq/L) or symptomatic: 3% hypertonic saline, correct slowly (8-12 mEq/L in 24 hours to avoid osmotic demyelination syndrome)

Condition-Specific Treatments

Bowel Obstruction:

• NPO
• Large-bore NG tube: Decompression, reduce aspiration risk
• IV fluid resuscitation: Correct dehydration (third-spacing causes significant losses)
• Analgesia: Avoid masking peritonitis
• Antibiotics: If strangulation, perforation, or sepsis suspected (ceftriaxone 2g IV + metronidazole 500 mg IV)
• Surgical consultation: Emergent for strangulation, closed-loop, complete obstruction; conservative management for partial obstruction from adhesions (NPO, NG, IV fluids for 48-72 hours)

Upper GI Bleeding:

• Resuscitation: 2 large-bore IVs, crystalloid bolus, type and crossmatch, transfuse if Hgb less than 7 g/dL (or less than 9 g/dL if CAD), target Hgb 7-9 g/dL
• Proton pump inhibitor: Pantoprazole 80 mg IV bolus then 8 mg/hr infusion
• Octreotide: If variceal bleeding suspected (50 μg bolus then 50 μg/hr infusion)
• Antiemetic: Ondansetron 4 mg IV
• Correct coagulopathy: Reverse anticoagulation (vitamin K, FFP, PCC), platelet transfusion if less than 50,000
• Endoscopy: Emergent if unstable, within 24 hours if stable
• GI consultation

Diabetic Ketoacidosis:

• IV fluids: 1-2 L NS bolus, then 250-500 mL/hr
• Insulin: Regular insulin 0.1 units/kg IV bolus, then 0.1 units/kg/hr infusion
• Potassium: Replace when K less than 5.3 mEq/L (insulin drives K intracellularly)
• Dextrose: Add D5 to fluids when glucose less than 250 mg/dL (continue insulin until anion gap closes)
• Search for precipitant: Infection (UA, CXR, blood cultures), MI (ECG, troponin), medication non-compliance
• Monitor: Glucose hourly, BMP every 2-4 hours, anion gap closure
• Transition: Subcutaneous insulin when eating, anion gap normalized, pH >7.3, bicarbonate >18

Acute Pancreatitis:

• NPO initially
• Aggressive IV fluid resuscitation: 250-500 mL/hr crystalloid (associated with reduced mortality)
• Analgesia: Opioids (morphine does NOT worsen pancreatitis despite historical teaching)
• Antiemetic: Ondansetron 4-8 mg IV
• Early enteral nutrition: Start within 24-48 hours if tolerated (reduces complications vs. prolonged NPO)
• ERCP: Emergent if biliary obstruction (cholangitis), otherwise within 24-72 hours for gallstone pancreatitis
• Antibiotics: NOT routinely indicated; only if infected necrosis, cholangitis, or sepsis

Acute Cholecystitis:

• NPO
• IV fluids
• Antibiotics: Ceftriaxone 2g IV daily + metronidazole 500 mg IV TID, or piperacillin-tazobactam 3.375g IV q6h
• Analgesia
• Surgical consultation: Cholecystectomy within 72 hours of symptom onset (reduces complications vs. delayed surgery)

Acute Appendicitis:

• NPO
• IV fluids
• Antibiotics: Cefoxitin 2g IV q6h or ceftriaxone 2g IV daily + metronidazole 500 mg IV q8h
• Surgical consultation: Appendectomy vs. antibiotics-first approach (noninferiority in uncomplicated appendicitis, but 20-30% recurrence within 1 year)

Raised Intracranial Pressure:

• Head elevation: 30°
• Avoid hypotension: Maintain MAP >80 mmHg (CPP = MAP - ICP, goal CPP >60 mmHg)
• Osmotic therapy: Mannitol 0.25-1 g/kg IV (onset 10-15 min, duration 6-8 hours) or hypertonic saline 3% 250 mL bolus (preferred if hypotensive)
• Hyperventilation: Target PaCO2 30-35 mmHg (lowers ICP via vasoconstriction but risks ischemia; reserve for impending herniation)
• Sedation: Propofol reduces ICP, facilitates ventilation
• Neurosurgical consultation: Ventriculostomy, decompressive craniotomy
• Treat underlying cause: Evacuation of hematoma, tumor resection, shunt for hydrocephalus

Migraine:

• IV fluids: 1 L NS
• NSAID: Ketorolac 30 mg IV or ibuprofen 800 mg PO
• Dopamine antagonist: Metoclopramide 10-20 mg IV or prochlorperazine 10 mg IV (dual antiemetic + migraine abortive effect)
• Triptan: Sumatriptan 6 mg SC (if no contraindications: CAD, uncontrolled HTN, hemiplegic migraine)
• Dexamethasone: 10 mg IV reduces recurrence within 72 hours
• Quiet, dark room

Vestibular Neuritis:

• Antihistamine: Meclizine 25 mg PO TID
• Antiemetic: Ondansetron 4 mg IV/PO
• Benzodiazepine: Lorazepam 0.5-1 mg IV/PO (acute vestibular suppression)
• Corticosteroids: Methylprednisolone 100 mg IV (if within 3 days of onset, improves vestibular recovery)
• Vestibular rehabilitation: Outpatient physical therapy

Hyperemesis Gravidarum:

• IV fluids: LR or NS with dextrose (prevent ketosis)
• Thiamine: 100 mg IV before dextrose (prevent Wernicke encephalopathy)
• Antiemetic: Ondansetron 4-8 mg IV, metoclopramide 10 mg IV
• Pyridoxine/doxylamine: Diclegis (delayed-release combination) or separate (pyridoxine 25 mg PO TID + doxylamine 25 mg PO QHS)
• Admit if: Ketonuria, weight loss >5%, unable to tolerate oral intake, electrolyte abnormalities

Cannabinoid Hyperemesis Syndrome:

• Cannabis cessation: ONLY definitive treatment (symptoms resolve within days to weeks)
• Haloperidol: 5 mg IV (most effective antiemetic for this syndrome)
• Capsaicin cream: 0.075% topical to abdomen (temporary relief)
• Hot shower: Temporary symptomatic relief (pathognomonic behavior)
• Avoid chronic antiemetic therapy: Does not address underlying cause, perpetuates cannabis use
• Avoid opioids: Not effective, worsen nausea

Cyclic Vomiting Syndrome:

• IV fluids: Aggressive (dehydration common)
• Antiemetic: Ondansetron 8 mg IV
• Triptan: Sumatriptan 6 mg SC (migraine-associated pathophysiology)
• Benzodiazepine: Lorazepam 1-2 mg IV
• Prophylaxis: Amitriptyline 25-50 mg PO QHS, propranolol 20-40 mg PO BID

---

Complications of Persistent Vomiting

Mallory-Weiss Tear:

• Pathophysiology: Longitudinal mucosal laceration at gastroesophageal junction from forceful vomiting; accounts for 10-15% of upper GI bleeding
• Presentation: Hematemesis after repeated non-bloody vomiting (classic history)
• Diagnosis: Upper endoscopy
• Management: Usually self-limited (80-90% stop bleeding spontaneously); IV PPI, endoscopic hemostasis if persistent bleeding (epinephrine injection, thermal coagulation, hemoclips)
• Prognosis: Excellent, rarely life-threatening

Boerhaave Syndrome (Spontaneous Esophageal Rupture):

• Pathophysiology: Full-thickness esophageal perforation from forceful vomiting (sudden increase in intraesophageal pressure against closed glottis)
• Presentation: Mackler triad (vomiting, lower chest pain, subcutaneous emphysema); dysphagia, dyspnea, shock
• Diagnosis: CXR (pneumomediastinum, pleural effusion, subcutaneous emphysema), CT chest with oral contrast (extravasation), esophagram (water-soluble contrast)
• Management: NPO, broad-spectrum antibiotics (gram-positive, gram-negative, anaerobic coverage), surgical consultation (emergent thoracotomy and primary repair within 24 hours), ICU admission
• Prognosis: Mortality 15-35% (increases with delayed diagnosis >24 hours to 50-70%)

Electrolyte Disturbances:

• Hypokalemia: Arrhythmias (PVCs, torsades de pointes), muscle weakness, rhabdomyolysis
• Hypomagnesemia: Refractory hypokalemia, arrhythmias, tetany
• Hypochloremic metabolic alkalosis: Usually well-tolerated, rarely severe
• Hyponatremia: Confusion, seizures (if severe less than 120 mEq/L)

Aspiration Pneumonia:

• Risk factors: Altered mental status, elderly, neuromuscular disorders, recumbent position
• Presentation: Fever, cough, dyspnea, hypoxia
• Diagnosis: CXR (infiltrate in dependent lung zones - RLL, posterior segments)
• Management: Antibiotics (community-acquired: ampicillin-sulbactam or clindamycin; hospital-acquired: piperacillin-tazobactam), supportive care, oxygen

Dental Erosion:

• Chronic vomiting (bulimia, GERD, cyclic vomiting): Gastric acid erodes enamel
• Prevention: Rinse with water after vomiting, avoid brushing immediately (softened enamel), fluoride treatments

Esophagitis:

• Chronic acid exposure from vomiting
• Symptoms: Dysphagia, odynophagia, chest pain
• Management: PPI therapy

Volume Depletion and Shock:

• Severe vomiting/diarrhea: Hypovolemic shock
• Presentation: Hypotension, tachycardia, oliguria, altered mental status, lactic acidosis
• Management: Aggressive IV crystalloid resuscitation (20-30 mL/kg boluses), vasopressors if refractory

Refeeding Syndrome:

• After prolonged starvation and vomiting, rapid refeeding causes insulin surge → intracellular shift of phosphate, potassium, magnesium
• Presentation: Hypophosphatemia, hypokalemia, hypomagnesemia; cardiac arrhythmias, respiratory failure, confusion, rhabdomyolysis
• Prevention: Slow refeeding, supplement electrolytes (phosphate, potassium, magnesium), thiamine before carbohydrates

---

Disposition and Follow-Up

Discharge Criteria

Safe discharge requires ALL of the following:

• ✓ Hydration restored (normal vital signs, adequate urine output, tolerating oral fluids)
• ✓ Nausea/vomiting controlled with oral antiemetics
• ✓ No red flags or life-threatening causes identified
• ✓ Underlying etiology identified and treated (or benign self-limited process)
• ✓ Electrolyte abnormalities corrected or mild and stable
• ✓ Patient reliable for follow-up
• ✓ Safe home environment with support

Discharge Medications:

• Antiemetic: Ondansetron 4-8 mg PO/ODT q8h PRN, or meclizine 25 mg PO TID (vestibular)
• Proton pump inhibitor: Omeprazole 20-40 mg PO daily (if gastritis, GERD suspected)
• Rehydration solution: Oral electrolyte solution for home use

Discharge Instructions:

• Oral intake: Small, frequent sips of clear liquids; advance to bland diet (BRAT) as tolerated; avoid fatty, spicy, acidic foods
• Hydration monitoring: Track urine output (should urinate every 6-8 hours, light yellow color)
• Antiemetic use: Take 30 minutes before attempting oral intake
• Activity: Rest, avoid strenuous activity until recovered
• Return precautions (provide written instructions):
  • ✗ Unable to keep down any fluids for >12 hours
  • ✗ Blood in vomit (red or coffee-ground appearance)
  • ✗ Severe abdominal pain
  • ✗ High fever (>101.5°F/38.6°C)
  • ✗ Confusion, severe dizziness, fainting
  • ✗ No urination for >12 hours
  • ✗ Severe weakness or inability to walk
  • ✗ Chest pain or difficulty breathing

Follow-Up:

• Primary care physician: 2-7 days (sooner if high-risk or persistent symptoms)
• Specialist referral: GI (chronic vomiting, dyspepsia, suspected gastroparesis), OB (pregnancy-related), neurology (migraine, vestibular disorders)

Admission Criteria

Hospitalization indicated if ANY of the following:

• ✗ Severe dehydration not corrected in ED (persistent hypotension, oliguria despite 2-3 L IV fluids)
• ✗ Unable to tolerate oral intake after antiemetics and observation
• ✗ Electrolyte abnormalities requiring IV correction (severe hypokalemia less than 2.5 mEq/L, symptomatic hyponatremia)
• ✗ Significant comorbidities at risk of decompensation (heart failure, chronic kidney disease, diabetes with poor control)
• ✗ Serious underlying etiology requiring inpatient treatment:
  • Bowel obstruction (surgical consultation, NPO, NG, IV fluids, possible surgery)
  • GI bleeding (ICU if unstable, GI consultation, endoscopy)
  • Pancreatitis (moderate-severe Ranson ≥3, aggressive IV fluids)
  • DKA (insulin infusion, frequent monitoring)
  • Hyperemesis gravidarum (IV fluids, thiamine, antiemetics)
  • Meningitis/encephalitis (IV antibiotics/antivirals)
  • Acute kidney injury (nephrology, possible dialysis)
  • Adrenal crisis (IV steroids, aggressive fluids)
• ✗ Age extremes with poor reserve (elderly with multiple comorbidities, frail)
• ✗ Social factors: Homelessness, no support, unreliable for follow-up, concern for self-care

Admission Level:

• Floor: Most admissions (uncomplicated obstruction, mild-moderate pancreatitis, hyperemesis gravidarum)
• Telemetry: Electrolyte abnormalities risking arrhythmia (K less than 2.5 or >6.0, severe hypomagnesemia), cardiac etiology
• ICU: Hemodynamic instability, GI bleeding with shock, DKA with severe acidosis or altered mental status, septic shock, respiratory failure, Boerhaave syndrome, severe pancreatitis (Ranson ≥3, APACHE II >8)

Observation Unit

Appropriate for borderline cases requiring extended monitoring (6-24 hours):

• Moderate dehydration responding to IV fluids but not yet ready for discharge
• Vomiting controlled but not yet tolerating oral intake
• Mild electrolyte abnormalities requiring recheck after IV correction
• Unclear diagnosis requiring serial exams and repeat labs

---

Special Populations

Pregnancy

Physiological Nausea of Pregnancy:

• 50-80% of pregnancies, peaks 9-12 weeks, resolves by 20 weeks
• Mild symptoms, maintains adequate oral intake and weight
• Management: Dietary modification (small frequent meals, avoid triggers), ginger, vitamin B6 (pyridoxine) 25 mg TID

Hyperemesis Gravidarum:

• Severe nausea/vomiting preventing adequate oral intake, weight loss >5%, dehydration, ketonuria
• 0.3-3% of pregnancies
• Risk factors: Multiple gestation, molar pregnancy, first pregnancy, history of hyperemesis in prior pregnancy
• Complications: Wernicke encephalopathy (thiamine deficiency), Mallory-Weiss tear, esophageal rupture, electrolyte disturbances (hypokalemia, hyponatremia)
• Management: IV fluids (add dextrose to prevent ketosis), thiamine 100 mg IV before dextrose, antiemetics (ondansetron, metoclopramide, pyridoxine/doxylamine), admission if severe

Pregnancy-Specific Serious Causes:

• Ectopic pregnancy: First trimester, abdominal pain, vaginal bleeding, hemodynamic instability if ruptured
• Acute fatty liver of pregnancy: Third trimester, nausea, vomiting, jaundice, elevated transaminases, hypoglycemia, coagulopathy, encephalopathy; delivery required
• HELLP syndrome: Third trimester, hemolysis, elevated liver enzymes, low platelets; preeclampsia complication; delivery required
• Appendicitis in pregnancy: Displaced RLQ mass by gravid uterus, delayed diagnosis increases perforation risk

Antiemetic Safety:

• Safe: Pyridoxine/doxylamine (FDA pregnancy category A), ondansetron (generally safe, small increased cleft palate risk controversial), metoclopramide
• Avoid: Scopolamine (limited data), promethazine (respiratory depression near term)

Elderly

Increased Risk Factors:

• Serious organic disease more common (malignancy, MI, bowel obstruction, mesenteric ischemia)
• Reduced physiological reserve (dehydration → shock faster)
• Polypharmacy (medication side effects, interactions)
• Atypical presentations (MI without chest pain, appendicitis without fever)

Diagnostic Approach:

• Lower threshold for comprehensive workup (labs, imaging)
• ECG for all elderly patients with nausea/vomiting
• Consider serious causes first (MI, obstruction, ischemia)

Medication Precautions:

• Avoid promethazine: Beers Criteria (anticholinergic, sedation, delirium risk)
• Reduce doses: Ondansetron 4 mg (vs. 8 mg in younger patients)
• Caution with metoclopramide: Higher EPS risk
• Fluid resuscitation: Cautious in heart failure, frequent reassessment

Disposition:

• Lower threshold for admission (reduced reserve, higher complication risk)

Postoperative Patients

Postoperative Nausea and Vomiting (PONV):

• Incidence: 20-30% of all surgeries, up to 70% in high-risk patients
• Risk factors (Apfel score): Female sex, non-smoker, history of PONV or motion sickness, postoperative opioids
• Prophylaxis: Ondansetron 4 mg IV at end of surgery + dexamethasone 4 mg IV at induction
• Treatment: Ondansetron 4 mg IV, switch to multimodal analgesia (reduce opioids), IV fluids

Ileus:

• Common after abdominal surgery, typically resolves 3-5 days
• Presentation: Nausea, vomiting, abdominal distension, absent bowel sounds
• Differentiation from obstruction: Gradual onset, diffuse (not localized), no transition point on imaging
• Management: NPO, NG tube if severe, IV fluids, early ambulation, minimize opioids, consider alvimopan (if postoperative ileus prevention protocol)

Chemotherapy Patients

Chemotherapy-Induced Nausea and Vomiting (CINV):

• Acute: Within 24 hours of chemotherapy
• Delayed: 24 hours to 5 days after chemotherapy
• Anticipatory: Before chemotherapy (conditioned response)

Emetogenicity Classification:

• High (>90%): Cisplatin, cyclophosphamide high-dose, dacarbazine
• Moderate (30-90%): Carboplatin, doxorubicin, oxaliplatin
• Low (10-30%): Paclitaxel, docetaxel, 5-FU
• Minimal (less than 10%): Vincristine, bevacizumab

Prophylaxis Protocol (Highly Emetogenic):

• 5-HT3 antagonist: Palonosetron 0.25 mg IV (longer half-life than ondansetron)
• NK1 antagonist: Aprepitant 125 mg PO day 1, then 80 mg PO days 2-3
• Dexamethasone: 12 mg PO day 1, then 8 mg PO days 2-4
• PRN: Lorazepam 0.5-1 mg q4-6h (anticipatory nausea)

Breakthrough CINV:

• Add agent from different class (if on 5-HT3 antagonist, add dopamine antagonist)
• Olanzapine 10 mg PO daily (emerging evidence for refractory CINV)
• Consider non-pharmacological: Acupuncture, ginger

Patients with Chronic Conditions

Diabetes Mellitus:

• Gastroparesis: Common chronic complication (autonomic neuropathy)
• DKA risk: Vomiting → poor oral intake → missed insulin → hyperglycemia → ketoacidosis (vicious cycle)
• Management: Check glucose, ketones; treat DKA if present; metoclopramide for gastroparesis

Chronic Kidney Disease:

• Uremia: Chronic nausea; improves with dialysis
• Medication accumulation: Renally-cleared drugs (metoclopramide) accumulate → increased toxicity

Heart Failure:

• Nausea from hepatic congestion, gut edema
• Fluid resuscitation: Cautious (risk of pulmonary edema)
• Consider diuresis if volume overloaded

Cirrhosis:

• Variceal bleeding risk: Upper GI bleeding protocol
• Hepatic encephalopathy: Worsened by GI bleeding, dehydration, electrolyte disturbances
• Ascites: Spontaneous bacterial peritonitis can present with nausea, vomiting, abdominal pain

---

Prognosis and Outcomes

Overall Prognosis:

• Benign causes (viral gastroenteritis, medication side effects): Excellent, self-limited within 24-72 hours
• Serious causes: Prognosis depends on underlying etiology and timeliness of intervention

Etiology-Specific Mortality:

• Viral gastroenteritis: less than 0.01% (developed countries)
• Bowel obstruction (uncomplicated): 2-5%; strangulation 8-25%
• Acute pancreatitis (mild): less than 1%; severe necrotizing 15-30%
• DKA: 0.2-2% (developed countries with ICU care)
• Boerhaave syndrome: 15-35%; >50% if diagnosis delayed >24 hours
• Mesenteric ischemia: 60-80%
• Ruptured ectopic pregnancy: less than 0.1% (with timely intervention)

Recurrence Rates:

• Cyclic vomiting syndrome: Recurrent by definition; prophylaxis reduces frequency
• Cannabinoid hyperemesis: 100% recurrence if cannabis use continues; 0% if abstinent
• Gastroparesis: Chronic condition; symptom management ongoing

Quality of Life Impact:

• Acute episodes: Temporary disruption, rapid return to baseline
• Chronic recurrent vomiting: Significant QOL impairment (cyclic vomiting syndrome, gastroparesis, chronic pancreatitis)

---

Prevention Strategies

Primary Prevention:

• Hand hygiene: Prevents gastroenteritis transmission (20 seconds with soap, alcohol-based sanitizer)
• Food safety: Proper cooking temperatures, avoid raw/undercooked foods, refrigerate promptly
• Vaccination: Rotavirus vaccine (infants), hepatitis A vaccine
• Medication review: Minimize emetogenic medications when possible, prophylactic antiemetics for high-risk (chemotherapy, postoperative)

Secondary Prevention (Reduce Recurrence):

• Migraine prophylaxis: Beta-blockers, anticonvulsants (if frequent migraines)
• Cyclic vomiting syndrome: Amitriptyline 25-50 mg QHS, propranolol 20-40 mg BID
• GERD management: PPI, lifestyle modifications
• Diabetic gastroparesis: Glycemic control, dietary modifications, prokinetics
• PONV prophylaxis: Multimodal approach (reduce opioids, adequate hydration, prophylactic antiemetics)

Tertiary Prevention (Prevent Complications):

• Hydration maintenance: Oral rehydration at symptom onset
• Early antiemetic use: Prevent progression to severe vomiting
• Aspiration precautions: Upright positioning, airway protection if altered mental status
• Electrolyte monitoring: Chronic vomiting patients require periodic labs

---

Patient Education

Condition Explanation

"Nausea and vomiting are very common symptoms that can be caused by many different conditions. Most of the time, they're due to viral infections (stomach bugs) or side effects from medications, and they get better on their own within a day or two. However, sometimes nausea and vomiting can be signs of more serious problems, so we've done tests to make sure you don't have anything dangerous."

"The most important part of treatment is staying hydrated - when you vomit, you lose a lot of fluid and electrolytes (salts) that your body needs. We've given you IV fluids to replace what you've lost, and medication to help control the nausea so you can drink fluids at home."

Home Care Instructions

Hydration:

• "Drink small amounts frequently - take small sips (1-2 tablespoons) every 5-10 minutes rather than large amounts at once."
• "Clear liquids first: water, ice chips, electrolyte solutions (Gatorade, Pedialyte), clear broth, ginger ale (let it go flat)."
• "Goal: 8-10 cups of fluid per day once tolerating."
• "Track your urine: should urinate every 6-8 hours, light yellow color means well-hydrated."

Diet Progression:

• "Don't rush eating - wait until nausea improves and you can keep down clear liquids."
• "Start with bland foods: crackers, toast, rice, bananas, applesauce (BRAT diet)."
• "Gradually add: chicken, fish, cooked vegetables, pasta."
• "Avoid for 24-48 hours: fatty foods (fried foods, pizza), spicy foods, dairy products, caffeine, alcohol."
• "Small, frequent meals (5-6 times per day) better tolerated than large meals."

Medication Use:

• "Take anti-nausea medication 30 minutes before trying to eat or drink."
• "Don't wait until nausea is severe - take medication at first sign of nausea returning."
• "Ondansetron dissolves on tongue (no water needed) - good if having trouble swallowing."

Activity:

• "Rest - your body needs energy to recover."
• "Avoid strenuous activity until you're eating and drinking normally."
• "If dizzy when standing, stand up slowly (sit at edge of bed first, then stand)."

Hygiene (If Infectious Gastroenteritis):

• "Wash hands frequently with soap and water for 20 seconds (alcohol sanitizer less effective against some viruses)."
• "Avoid preparing food for others until symptom-free for 48 hours."
• "Disinfect contaminated surfaces (bathroom, doorknobs) with bleach solution."
• "Avoid close contact with others (highly contagious)."

Warning Signs to Return to Emergency Department

Seek immediate medical attention if you experience:

• ✗ Blood in vomit (bright red or looks like coffee grounds)
• ✗ Unable to keep down any liquids for more than 12 hours (risk of severe dehydration)
• ✗ Severe abdominal pain (especially if worsening, sharp, or constant)
• ✗ High fever (temperature >101.5°F or 38.6°C)
• ✗ Severe headache (worst headache of your life, sudden onset)
• ✗ Confusion, severe dizziness, or fainting
• ✗ No urination for more than 12 hours or very dark urine (dehydration)
• ✗ Chest pain or difficulty breathing
• ✗ Severe weakness (unable to stand or walk)
• ✗ Stiff neck with fever and headache
• ✗ Pregnancy with severe pain or vaginal bleeding
• ✗ Symptoms not improving after 2-3 days

When to Follow Up with Primary Care Doctor

• Schedule appointment within 2-7 days if:
  • Symptoms improving but not completely resolved
  • Need medication refills or adjustments
  • Recurrent episodes of nausea/vomiting (may need further workup)
  • Underlying condition requiring ongoing management (diabetes, GERD)

---

Key Clinical Pearls

Diagnostic Pearls

Red Flag Recognition:

• Feculent vomiting = Advanced bowel obstruction: NPO, NG tube, surgical consult immediately
• Bilious vomiting in infant = Malrotation with volvulus: Surgical emergency
• Coffee-ground emesis = Upper GI bleed: Resuscitate, IV PPI, GI consult
• Projectile vomiting without nausea = Raised ICP: CT head urgently
• Nausea/vomiting + inferior STEMI: Common presentation (vagal stimulation); don't miss MI
• Compulsive hot bathing = Cannabinoid hyperemesis: Pathognomonic behavior
• Kussmaul respirations + fruity breath = DKA: Check glucose/ketones immediately

Physical Exam Findings:

• Succussion splash: Gastric outlet obstruction, gastroparesis
• Absent bowel sounds: Ileus, peritonitis, late obstruction (high-pitched tinkling = early obstruction)
• Murphy's sign: Acute cholecystitis (inspiratory arrest with RUQ palpation)
• Periumbilical pain → RLQ: Classic appendicitis migration
• Papilledema: Raised ICP (loss of venous pulsations earliest sign)
• Positive HINTS exam: Central vertigo (stroke) not peripheral; HINTS negative = safe peripheral cause

Laboratory Clues:

• Hypokalemia + metabolic alkalosis: Persistent vomiting (gastric HCl loss)
• Hyperkalemia + hyponatremia + hypoglycemia: Adrenal insufficiency (give hydrocortisone immediately)
• Anion gap metabolic acidosis: DKA, lactic acidosis (ischemic bowel), uremia, toxins
• Lipase >3× ULN: Pancreatitis (but can be elevated in bowel obstruction, renal failure)
• Elevated BUN:Cr ratio >20:1: Prerenal azotemia (dehydration, upper GI bleed)

Treatment Pearls

Antiemetic Selection:

• Ondansetron first-line: Broad efficacy, minimal side effects, works for most etiologies
• Metoclopramide if gastroparesis: Prokinetic effect; AVOID in obstruction (increases perforation risk)
• Prochlorperazine for migraine: Dual benefit (antiemetic + abortive)
• Haloperidol for cannabinoid hyperemesis: Most effective; standard antiemetics often fail
• Meclizine for vestibular: Antihistamine blocks vestibular input
• Dexamethasone for refractory nausea: Synergistic with other antiemetics; prevents migraine recurrence
• Combination therapy: Different mechanisms synergize (ondansetron + metoclopramide better than either alone)

Fluid Resuscitation:

• Aggressive early fluids prevent complications: Especially in pancreatitis (reduces mortality), DKA
• Oral rehydration equally effective for mild-moderate dehydration: Faster discharge, patient preference, lower cost
• Add potassium to IV fluids: Vomiting causes significant K+ loss; replace when less than 5.3 mEq/L
• Normal saline for DKA, hypochloremic alkalosis: Replaces chloride; lactated Ringer's for large volumes otherwise

Avoid Common Errors:

• Don't give metoclopramide if obstruction suspected: Prokinetic worsens against fixed obstruction
• Don't delay antibiotics in meningitis for LP: Blood cultures, then empiric antibiotics immediately; LP after (ideally within 1 hour)
• Don't forget pregnancy test: Changes differential diagnosis and treatment options entirely
• Don't attribute to gastroenteritis without considering red flags: Especially in elderly, immunocompromised
• Don't discharge severe dehydration: Must correct to normal vital signs, tolerate oral fluids
• Don't give thiamine AFTER dextrose: Risk Wernicke encephalopathy in malnourished/chronic vomiting

Disposition Pearls

Safe to Discharge:

• Viral gastroenteritis: After hydration restored, tolerating oral fluids, no red flags
• Medication side effect: After antiemetic given, underlying cause addressed
• Mild pregnancy-related nausea: Tolerating fluids, no ketonuria, reliable follow-up

Requires Admission:

• Bowel obstruction: Surgical consultation, NPO, NG tube, IV fluids, possible surgery
• GI bleeding: Hemodynamically unstable, Hgb less than 7, high-risk features (varices, ongoing bleeding)
• DKA: Insulin infusion, frequent monitoring (hourly glucose, BMP q2-4h)
• Pancreatitis: Moderate-severe (Ranson ≥3), aggressive IV fluids (250-500 mL/hr)
• Hyperemesis gravidarum: Unable to tolerate oral, ketonuria, weight loss >5%
• Severe dehydration: Not corrected in ED, elderly with poor reserve
• Electrolyte emergencies: Severe hypokalemia less than 2.5 mEq/L, symptomatic hyponatremia

Observation Unit Appropriate:

• Moderate dehydration responding to IV fluids but not yet ready for discharge
• Unclear diagnosis requiring serial exams (possible early appendicitis, obstruction)
• Mild electrolyte abnormalities requiring recheck after IV correction

---

References

1. Johns T, Alsolaimani R, Greenwald K, et al. Evaluation and Treatment of Nausea and Vomiting in Adults. Am Fam Physician. 2024;109(5):439-447. PMID: 38804756.

2. Graves NS. Acute gastroenteritis. Prim Care. 2013;40(3):727-741. doi:10.1016/j.pop.2013.05.006

3. Patanwala AE, Amini R, Hays DP, Rosen P. Antiemetic therapy for nausea and vomiting in the emergency department. J Emerg Med. 2010;39(3):330-336. doi:10.1016/j.jemermed.2009.08.060

4. Di Saverio S, Podda M, De Simone B, et al. Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. World J Emerg Surg. 2020;15(1):27. doi:10.1186/s13017-020-00306-3

5. Koffler J, Friedman D, Rothstein RD. Antiemetic efficacy of intravenous ondansetron versus intravenous metoclopramide in the emergency department setting. Ann Emerg Med. 2002;40(4):388-393. doi:10.1067/mem.2002.127935

6. Freedman SB, Pasichnyk D, Black KJL, et al. Gastroenteritis Therapies in Developed Countries: Systematic Review and Meta-Analysis. PLoS One. 2015;10(6):e0128754. doi:10.1371/journal.pone.0128754

7. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 189: Nausea and Vomiting of Pregnancy. Obstet Gynecol. 2018;131(1):e15-e30. doi:10.1097/AOG.0000000000002456

8. Kitabchi AE, Umpierrez GE, Miles JM, Fisher JN. Hyperglycemic crises in adult patients with diabetes. Diabetes Care. 2009;32(7):1335-1343. doi:10.2337/dc09-9032

9. Hesketh PJ. Chemotherapy-induced nausea and vomiting. N Engl J Med. 2008;358(23):2482-2494. doi:10.1056/NEJMra0706547

10. Li BU, Lefevre F, Chelimsky GG, et al. North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition consensus statement on the diagnosis and management of cyclic vomiting syndrome. J Pediatr Gastroenterol Nutr. 2008;47(3):379-393. doi:10.1097/MPG.0b013e318173ed39

11. Blumentrath CG, Dohrmann B, Ebert MP, Brenner D. Cannabinoid hyperemesis and the cyclic vomiting syndrome in adults: recognition, diagnosis, acute and long-term treatment. Ger Med Sci. 2017;15:Doc06. doi:10.3205/000247

12. Siket MS, Edlow JA. Transient ischemic attack: Reviewing the evolution of the definition, diagnosis, risk stratification, and management for the emergency physician. Emerg Med Clin North Am. 2012;30(3):745-770. doi:10.1016/j.emc.2012.05.001

13. Taylor JR, Streetman DS, Castle SS. Medication-related problems in the emergency department: A systematic review. J Clin Pharm Ther. 2016;41(3):344-352. doi:10.1111/jcpt.12391

14. Quigley EM, Hasler WL, Parkman HP. AGA technical review on nausea and vomiting. Gastroenterology. 2001;120(1):263-286. doi:10.1053/gast.2001.20516

15. Tack J, Talley NJ, Camilleri M, et al. Functional gastroduodenal disorders. Gastroenterology. 2006;130(5):1466-1479. doi:10.1053/j.gastro.2005.11.059

16. Gan TJ, Belani KG, Bergese S, et al. Fourth Consensus Guidelines for the Management of Postoperative Nausea and Vomiting. Anesth Analg. 2020;131(2):411-448. doi:10.1213/ANE.0000000000004833

17. Katzung BG, Masters SB, Trevor AJ. Basic and Clinical Pharmacology. 14th ed. McGraw-Hill Education; 2018.

18. Hasler WL, Chey WD. Nausea and vomiting. Gastroenterology. 2003;125(6):1860-1867. doi:10.1053/j.gastro.2003.08.025

19. Scorza K, Williams A, Phillips JD, Shaw J. Evaluation of nausea and vomiting. Am Fam Physician. 2007;76(1):76-84. PMID: 17668843.

20. Koch KL, Stern RM, Stewart WR, Vasey MW. Gastric emptying and gastric myoelectrical activity in patients with diabetic gastroparesis: effect of long-term domperidone treatment. Am J Gastroenterol. 1989;84(9):1069-1075. PMID: 2773901.

21. Metz A, Hebbard G. Nausea and vomiting in adults--a diagnostic approach. Aust Fam Physician. 2007;36(9):688-692. PMID: 17885699.

22. Singh P, Yoon SS, Kuo B. Nausea: a review of pathophysiology and therapeutics. Therap Adv Gastroenterol. 2016;9(1):98-112. doi:10.1177/1756283X15618131