Opioid Overdose

Quick Answer

One-liner: Opioid overdose is a life-threatening emergency characterised by respiratory depression, central nervous system depression, and pinpoint pupils, requiring immediate airway protection, ventilation support, and naloxone administration.

Opioid overdose occurs when excessive opioid agonism at mu-receptors causes life-threatening respiratory depression through depression of the brainstem respiratory centre. Immediate priorities are airway protection, ventilation support, and administration of the competitive antagonist naloxone. Mortality in treated overdose ranges from 0.5-2%, rising dramatically when naloxone is delayed or absent [1,2]. Key features include respiratory rate less than 10 breaths per minute, SpO2 below 90%, decreased level of consciousness (GCS below 8), and characteristic pinpoint pupils [3,4]. Long-acting opioids such as methadone, extended-release oxycodone, and transdermal fentanyl pose specific risks of delayed respiratory depression requiring extended observation periods of 12-24 hours [5,6].

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ACEM Exam Focus

Primary Exam Relevance

• Anatomy: Brainstem respiratory centre (medulla oblongata, pons), nucleus ambiguus, pontine respiratory groups; autonomic nervous system innervation of airway and respiratory muscles [7,8]
• Physiology: Mu-opioid receptor signal transduction (Gi-protein coupled), hyperpolarisation of respiratory centre neurons, hypoxic ventilatory response inhibition; chemoreceptor function (central and peripheral) [9,10]
• Pharmacology: Pharmacodynamics of opioid agonists (morphine, heroin, fentanyl, methadone, buprenorphine, codeine, tramadol), competitive antagonism by naloxone, dose-response relationships, receptor occupancy theory, pharmacokinetics (first-pass metabolism, distribution, elimination half-life) [11,12]

Fellowship Exam Relevance

• Written: Recognition of clinical triad (CNS depression, respiratory depression, miosis); naloxone dosing regimens and rebound phenomenon; management of long-acting opioid complications; differential diagnosis of pinpoint pupils; non-cardiogenic pulmonary oedema pathophysiology and management [13,14]
• OSCE: Resuscitation station - acute opioid overdose management; Communication station - family counselling and harm reduction education; Procedure station - intranasal naloxone administration, bag-mask ventilation technique [15,16]
• Key domains tested: Medical Expert (assessment, diagnosis, management), Communicator (family communication, patient education), Health Advocate (harm reduction, take-home naloxone programs) [17,18]

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Key Points

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Epidemiology

Australian/NZ Specific

Australian Trends:

• Opioid overdose deaths increased by 68% between 2007-2018, plateauing at approximately 1,100 deaths annually from 2019 onwards [26]
• Pharmaceutical opioids (oxycodone, codeine, morphine) now account for 70-75% of opioid overdose deaths, exceeding heroin [32]
• Prescription opioid misuse most common in regional and rural areas with limited access to alternative pain management [33]
• Aboriginal and Torres Strait Islander peoples have 2-3 times higher rates of opioid overdose presentations compared to non-Indigenous Australians [34]

New Zealand Trends:

• Opioid-related harm increasing, particularly with prescription opioids and synthetic opioids [35]
• Māori experience disproportionate opioid overdose mortality compared to non-Māori [36]

Geographic Distribution:

• Higher presentation rates in urban centres with supervised injection facilities
• Remote and rural areas face delayed presentation times and limited access to addiction services [33]
• Socioeconomic deprivation strongly associated with overdose risk (IRR 3-5 for most disadvantaged quintile) [37]

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Pathophysiology

Mechanism

Mu-Opioid Receptor Activation:

• Opioids bind to mu-opioid receptors (G-protein coupled receptors) in the brainstem respiratory centre, specifically the pre-Bötzinger complex in the medulla oblongata [9,10]
• Receptor activation leads to Gi-protein mediated inhibition of adenylate cyclase, decreased cAMP, and opening of potassium channels
• Result: hyperpolarisation of respiratory neurons, decreased respiratory drive, reduced response to hypercapnia and hypoxia [9,38]

Respiratory Depression:

• Central apnoea: decreased automatic respiratory rhythm generation
• Irregular breathing: Cheyne-Stokes pattern, ataxic breathing
• Upper airway obstruction: loss of pharyngeal muscle tone, tongue obstruction
• Reduced hypoxic ventilatory response: blunted chemoreceptor function [9,10,39]

Central Nervous System Depression:

• Direct sedative effect on cortical and subcortical structures
• Decreased level of consciousness (GCS 8-12 common)
• Pupillary constriction: parasympathetic predominance via Edinger-Westphal nucleus [40,41]

Pathological Progression

Opioid Ingestion/Injection
       ↓
Mu-Receptor Saturation (brainstem)
       ↓
Respiratory Centre Depression
       ↓
Respiratory Rate Decline (below 10)
       ↓
Hypoxaemia (SpO2 below 90%)
       ↓
Hypercapnia (PaCO2 above 50 mmHg)
       ↓
Metabolic Acidosis (pH below 7.35)
       ↓
Cardiovascular Instability (bradycardia, hypotension)
       ↓
Cardiac Arrest (PEA/Asystole)

Why It Matters Clinically

• Time-critical: Respiratory depression progresses rapidly; irreversible hypoxic brain injury occurs within 4-6 minutes of absent ventilation [42,43]
• Reversibility: Naloxone competitively displaces opioids from mu-receptors, restoring respiratory drive within 1-3 minutes [19,20]
• Rebound risk: Most opioids have longer half-lives than naloxone; delayed respiratory depression necessitates extended observation [5,21]
• Non-cardiogenic pulmonary oedema: Hypoxia-induced pulmonary capillary leak and neurogenic mechanisms can cause acute respiratory distress even after naloxone administration [24,25]

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Clinical Approach

Recognition

Key Triggers for Suspected Opioid Overdose:

• Found unresponsive or with decreased level of consciousness
• Respiratory rate below 10 breaths per minute or absent
• Witnesses report opioid use or paraphernalia present (needles, foil, pills)
• Known history of opioid use disorder or chronic opioid prescription [3,4]

Initial Assessment

Primary Survey

• Airway: Assess for obstruction, loss of tone, secretions. Position with jaw thrust. Consider oropharyngeal airway if GCS below 8.
• Breathing: Count respiratory rate for 60 seconds. Check chest wall movement, breath sounds, oxygen saturation. Bag-mask ventilation if rate below 8 or SpO2 below 90%.
• Circulation: Palpate central and peripheral pulses. Measure blood pressure. Assess capillary refill time. Expect bradycardia (heart rate 50-60) and mild hypotension (SBP 90-100 mmHg).
• Disability: Assess GCS, pupillary size and response (pinpoint pupils below 2 mm with poor constriction to light). Check blood glucose (to exclude hypoglycaemia).
• Exposure: Check for track marks, injection sites, skin colouring (cyanosis, mottling). Measure temperature (hypothermia possible).

History

Key Questions

Red Flag Symptoms

Examination

General Inspection

• Level of consciousness: lethargic, stuporose, or comatose
• Positioning: often slumped or supine
• Breathing pattern: shallow, slow, Cheyne-Stokes, or absent
• Cyanosis: central or peripheral
• Needle marks: antecubital fossa, groin, feet, hands (common sites)
• Paraphernalia: syringes, spoons, foil, pills, bottles

Specific Findings

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Investigations

Immediate (Resus Bay)

Standard ED Workup

Advanced/Specialist

Point-of-Care Ultrasound

• Lung ultrasound: Detect pulmonary oedema (B-lines, bilateral effusions)
• Cardiac ultrasound: Assess ejection fraction, wall motion abnormalities, volume status
• Inferior vena cava diameter: Assess fluid responsiveness
• Gastric ultrasound: Assess gastric content before intubation (aspiration risk)

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Management

Immediate Management (First 10 minutes)

1. CALL FOR HELP: Activate emergency response, request resuscitation trolley, prepare naloxone
2. AIRWAY PROTECTION: Position with jaw thrust, insert oropharyngeal airway if GCS below 8
3. VENTILATION SUPPORT: Bag-mask ventilation if respiratory rate below 8 or SpO2 below 90%
4. NALOXONE ADMINISTRATION: 400 micrograms IV/IM/IN, repeat every 2-3 minutes until adequate ventilation
5. MONITORING: Continuous pulse oximetry, ECG, capnography if intubated
6. ASSESS CO-INGESTANTS: Order glucose, ECG, urine drug screen, acetaminophen level

Resuscitation

Airway

Basic Airway:

• Position with head-tilt, chin-lift or jaw thrust
• Insert oropharyngeal airway if GCS below 8 (avoid if gag reflex present)
• Nasopharyngeal airway if oropharyngeal not tolerated (contraindicated if basal skull fracture)
• Suction secretions and vomitus
• High-flow oxygen (15 L/min) via non-rebreather mask

Advanced Airway (if indications met):

• Indications: GCS below 8, unprotected airway, persistent respiratory depression despite naloxone, aspiration risk, refractory hypoxaemia
• Rapid sequence intubation with cricoid pressure
• Agents: Etomidate 0.3 mg/kg or ketamine 1-2 mg/kg + Rocuronium 1.2 mg/kg
• Post-intubation: Target SpO2 94-98%, PaCO2 35-45 mmHg, tidal volume 6-8 mL/kg (ideal body weight)

Breathing

Ventilation Targets:

• SpO2: 94-98% (avoid hyperoxia above 100%)
• Respiratory rate: 12-16 breaths per minute
• PaCO2: 35-45 mmHg (permissive hypercapnia 50-60 mmHg if lung-protective strategy required)
• Peak inspiratory pressure: below 30 cmH2O

Oxygen Therapy:

• Start with 15 L/min via non-rebreather mask
• Titrate to SpO2 94-98% once spontaneous ventilation restored
• Consider humidified high-flow nasal cannula if mild respiratory distress after naloxone

Circulation

Haemodynamic Targets:

• Systolic blood pressure: 90-100 mmHg (higher if underlying hypertension)
• Mean arterial pressure: 65 mmHg or above
• Heart rate: 60-100 beats per minute (bradycardia common)

Interventions:

• IV access: 2 large-bore cannulae (14G or 16G)
• Fluid bolus: 500-1000 mL crystalloid if hypotensive (systolic below 90 mmHg)
• Vasopressors (rarely required): Noradrenaline infusion 0.05-0.5 mcg/kg/min if refractory hypotension

Medications

Paediatric Dosing

Ongoing Management

Monitoring Requirements:

• Continuous pulse oximetry and cardiac monitoring for 4-6 hours (short-acting opioids)
• Hourly vital signs, GCS, and respiratory rate for 4-6 hours
• Neurological observations (pupil size, response, limb movements)
• Fluid balance (input/output monitoring)

Observation Periods:

• Short-acting opioids (heroin, morphine, oxycodone immediate-release): 4-6 hours after last naloxone dose
• Long-acting opioids (methadone, extended-release oxycodone, transdermal fentanyl): 12-24 hours after last naloxone dose
• Synthetic opioids (fentanyl analogues): 24 hours minimum observation

Discharge Readiness Criteria:

• Respiratory rate at least 12 breaths per minute for 2 hours without naloxone
• GCS 15 (or baseline if pre-existing deficit)
• SpO2 94-98% on room air
• Normal temperature (36-37.5°C)
• No co-ingestants or co-ingestants managed appropriately
• Safe discharge plan with responsible adult present

Definitive Care

Addiction Services Referral:

• Opioid substitution therapy (OST) referral for opioid use disorder
• Options: Methadone, buprenorphine, buprenorphine-naloxone (Suboxone)
• Harm reduction education: take-home naloxone prescription, supervised injection facilities, needle exchange programs

Specialist Involvement:

• Critical care referral: ICU admission if persistent respiratory depression, aspiration pneumonia, non-cardiogenic pulmonary oedema
• Toxicology consultation: complex polypharmacy overdose, synthetic opioids, refractory cases
• Addiction medicine: OMT initiation, withdrawal management, psychosocial support

Follow-up:

• GP referral for ongoing management
• Addiction medicine clinic appointment within 7 days
• Mental health referral if depression, anxiety, or suicidal ideation present

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Disposition

Admission Criteria

• Persistent respiratory depression (rate below 10) after naloxone
• Rebound respiratory depression requiring multiple naloxone doses or naloxone infusion
• GCS below 13 after 2 hours observation
• Hypoxaemia (SpO2 below 90%) despite supplemental oxygen
• Co-ingestants requiring treatment (acetaminophen toxicity, salicylate toxicity, significant alcohol)
• Aspiration pneumonia (bilateral infiltrates on CXR, fever, leukocytosis)
• Non-cardiogenic pulmonary oedema (bilateral crackles, pink frothy sputum, respiratory distress)
• Medical comorbidities requiring monitoring (COPD, cardiac disease, renal impairment)
• Lack of safe discharge plan or responsible adult

ICU/HDU Criteria

• Persistent respiratory failure requiring mechanical ventilation
• Haemodynamic instability (SBP below 90 mmHg) despite fluid resuscitation
• Cardiac arrhythmias (torsades de pointes, ventricular tachycardia)
• Severe metabolic acidosis (pH below 7.20) or lactate above 8 mmol/L
• Multi-organ failure (respiratory, cardiovascular, renal)
• Synthetic opioid overdose (fentanyl, carfentanil) with prolonged respiratory depression

Discharge Criteria

• Respiratory rate at least 12 breaths per minute sustained for 2 hours after last naloxone dose
• GCS 15 (or at baseline if pre-existing deficit)
• SpO2 94-98% on room air
• Normal temperature (36-37.5°C)
• No co-ingestants or co-ingestants managed appropriately
• Able to ambulate without assistance
• No signs of aspiration or pulmonary complications
• Safe discharge plan with responsible adult present
• Take-home naloxone kit provided and education completed

Follow-up

• GP letter: Detail of overdose, treatments administered, discharge instructions, medications, follow-up recommendations
• Addiction services: Referral to opioid substitution therapy program, appointment within 7 days
• Harm reduction: Take-home naloxone prescription, education on overdose recognition and response, needle exchange programs
• Mental health: Screening for depression, anxiety, suicidal ideation; referral to mental health services if indicated
• Social work: Housing assessment, financial assistance, family support services if indicated

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Special Populations

Paediatric Considerations

• Most paediatric opioid overdoses are accidental (exploratory ingestion)
• Dosing: Naloxone 100 mcg/kg for neonates to 5 years, 2-3 mg for 6-14 years
• Lower threshold for intubation due to smaller airway and faster desaturation
• Suspected non-accidental injury if recurrent overdoses or inconsistent history
• Report to child protection services if concerns regarding neglect or intentional harm

Pregnancy

• Opioid overdose poses risks to both mother and foetus (fetal hypoxia, placental insufficiency)
• Naloxone crosses placenta; administer as per usual dosing (maternal respiratory depression priority)
• Monitor fetal heart rate and cardiotocography after viability (24 weeks gestation)
• Obstetrics consultation for monitoring and delivery planning if required
• Opioid substitution therapy (methadone, buprenorphine) reduces risk of overdose and improves maternal and fetal outcomes

Elderly

• Altered pharmacokinetics (reduced renal/hepatic clearance) increases sensitivity to opioids
• Lower naloxone starting dose: 200 micrograms IV/IM/IN
• Higher risk of aspiration due to decreased laryngeal reflexes
• Increased risk of complications (pneumonia, pressure ulcers, delirium)
• Comprehensive geriatric assessment: cognitive function, functional status, medication review

Indigenous Health

Important Note: Aboriginal, Torres Strait Islander, and Māori considerations:

• Disproportionate burden of opioid overdose (2-3 times higher incidence) due to complex interplay of historical trauma, socioeconomic disadvantage, and limited access to culturally appropriate healthcare [34,36]
• Higher prevalence of comorbidities (COPD, cardiovascular disease, diabetes) increasing overdose risk
• Cultural safety: Use respectful communication, acknowledge cultural identity, involve Aboriginal and Torres Strait Islander health workers or Māori cultural liaison
• Interpreter services: Provide professional interpreters if English is second language; avoid family members as interpreters
• Community-based services: Support Aboriginal Medical Services, Māori health providers, and community-controlled organisations
• Harm reduction programs: Culturally appropriate take-home naloxone programs, peer education, safe disposal of unused medications
• Address underlying determinants: Housing, employment, education, social connection
• Respect cultural protocols: Whanaungatanga (relationship building), manaakitanga (care and support) for Māori patients; Welcome to Country, smoking ceremonies if appropriate for Aboriginal and Torres Strait Islander patients

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Pitfalls & Pearls

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Viva Practice

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OSCE Scenarios

Station 1: Opioid Overdose Management (Resuscitation Station)

Format: Resuscitation Time: 11 minutes Setting: ED resuscitation bay

Candidate Instructions:

A 35-year-old male is brought to the emergency department by ambulance. He was found unconscious in a public park. Ambulance report: respiratory rate 4 breaths per minute, heart rate 48 beats per minute, blood pressure 85/50 mmHg, oxygen saturation 82% on room air, GCS 3, pinpoint pupils. The paramedic has positioned the patient and is providing bag-mask ventilation with oxygen. A small kit containing needles and a spoon was found nearby.

You are the team leader. Manage this patient, providing clear instructions to your team and explaining your management decisions.

Examiner Instructions: The patient is a 35-year-old male with opioid overdose (presumed heroin based on paraphernalia). Bag-mask ventilation is in progress. Oxygen saturation is improving to 95% with ventilation. A nurse and registrar are available to assist you. The candidate should demonstrate systematic ABCDE approach, appropriate naloxone dosing, assessment for co-ingestants, and clear communication.

Expected progression:

1. Immediate assessment of current status (airway, breathing, circulation, disability)
2. Orders for IV access, monitoring (cardiac, pulse oximetry), investigations
3. Naloxone administration with appropriate dosing
4. Assessment for complications (pulmonary oedema, aspiration)
5. Plan for observation period and disposition

Marking Criteria:

Expected Standard:

• Pass: 9/15 or above
• Key discriminators: Correct naloxone dosing, recognition of rebound respiratory depression requiring extended observation, assessment for co-ingestants (acetaminophen level, ECG)
• Fail: Incorrect naloxone dose (excessive or too low), failure to check glucose, inappropriate discharge planning (discharging too soon)

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Station 2: Take-Home Naloxone Education (Communication Station)

Format: Communication Time: 11 minutes Setting: ED consultation room

Candidate Instructions:

You are seeing a 28-year-old female who has been observed for 6 hours following heroin overdose. She received naloxone (total 1.2 mg) and is now ready for discharge. She is awake, alert, with GCS 15, respiratory rate 16 breaths per minute, oxygen saturation 98% on room air. She lives with her partner who is present with her today.

Your task is to provide education about take-home naloxone, including how to recognise an opioid overdose and how to administer naloxone. Address her concerns and ensure she understands the importance of harm reduction strategies.

Examiner Instructions: The patient (Sarah) is 28 years old with opioid use disorder. She is currently on buprenorphine-naloxone (Suboxone) maintenance therapy. She is receptive to education but expresses anxiety about future overdoses and concerns about her partner's ability to respond appropriately. Her partner (Tom) is supportive but has no medical training.

Actor/Patient Brief:

• Name: Sarah
• Age: 28 years old
• Background: History of heroin use for 4 years, currently on Suboxone maintenance therapy for 6 months
• Tonight's overdose: Accidental relapse, used heroin after stressful event
• Concerns: "I'm scared this will happen again," "I don't want to die," "Tom doesn't know what to do"
• Attitude: Motivated to engage with treatment, appreciates medical care
• Partner (Tom): Supportive, willing to learn, anxious but engaged

Marking Criteria:

Expected Standard:

• Pass: 12/19 or above
• Key discriminators: Clear explanation of naloxone administration (intranasal, dose, timing), recognition of overdose signs, emphasis on calling 000 and staying with person
• Fail: Incorrect naloxone dose, failure to emphasise calling 000, judgmental attitude toward substance use

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Station 3: Complex Opioid Overdose (Resuscitation Station)

Format: Resuscitation Time: 11 minutes Setting: ED resuscitation bay

Candidate Instructions:

A 52-year-old male with chronic back pain presents via ambulance. He was found unresponsive by his wife. Empty bottles of the following medications were found: oxycodone 80 mg (quantity unknown), diazepam 10 mg (quantity unknown), and acetaminophen 500 mg (quantity unknown).

On arrival: respiratory rate 5 breaths per minute, heart rate 42 beats per minute, blood pressure 75/40 mmHg, oxygen saturation 84% on room air, GCS 6, pupils 5 mm equal and sluggish. The paramedic has established IV access and is providing bag-mask ventilation with oxygen.

You are the team leader. Manage this patient, providing clear instructions to your team and explaining your management decisions.

Examiner Instructions: This is a complex mixed overdose with opioids (oxycodone), benzodiazepines (diazepam), and potential acetaminophen toxicity. The absence of pinpoint pupils (pupils 5 mm and sluggish) is atypical and requires explanation. The patient has significant haemodynamic instability (hypotension, bradycardia) requiring active management. A nurse and registrar are available to assist.

Expected progression:

1. Immediate assessment: ABCDE, recognise atypical findings (pupils)
2. Naloxone administration: start with 400 mcg IV, titrate to respiratory rate above 10
3. Acetaminophen level: order immediately (time-critical)
4. ECG: assess for QT prolongation (oxycodone, diazepam can prolong QT)
5. Fluid resuscitation: 500-1000 mL crystalloid for hypotension
6. Consider ICU admission for mixed overdose and co-ingestants
7. Explain atypical pupils: mixed overdose, hypoxic injury, or high tolerance

Marking Criteria:

Expected Standard:

• Pass: 10/17 or above
• Key discriminators: Recognition of acetaminophen toxicity risk (order level immediately), appropriate naloxone titration, explanation of atypical pupils, ICU admission for mixed overdose
• Fail: Failure to order acetaminophen level, incorrect naloxone dose, failure to recognise need for ICU admission

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SAQ Practice

Question 1 (6 marks)

Stem: A 30-year-old male presents to the emergency department with suspected heroin overdose. On arrival: respiratory rate 4 breaths per minute, heart rate 50 beats per minute, blood pressure 85/50 mmHg, oxygen saturation 80% on room air, GCS 6, pinpoint pupils.

Question: Outline your immediate management of this patient.

Model Answer:

• Airway protection: Jaw thrust, oropharyngeal airway (GCS 6), suction secretions (1 mark)
• Ventilation support: Bag-mask ventilation, high-flow oxygen (15 L/min) (1 mark)
• Naloxone administration: 400 micrograms IV/IM/IN immediately (1 mark)
• Repeat naloxone: Every 2-3 minutes until respiratory rate above 10 breaths per minute (1 mark)
• Monitoring: Continuous pulse oximetry, cardiac monitoring, capillary glucose check (1 mark)
• IV access: Two large-bore cannulae (14G or 16G), fluid bolus 500-1000 mL crystalloid if hypotensive (1 mark)

Examiner Notes:

• Accept: "Give naloxone" (no dose specified) for 0.5 marks only (dose required for full marks)
• Accept: "Airway, breathing, circulation approach" (general) if not expanded further
• Do not accept: Intubation as first-line (bag-mask ventilation first unless contraindications)
• Do not accept: High-dose naloxone initially (start low and titrate)

Question 2 (8 marks)

Stem: A 42-year-old female with known methadone use disorder presents after suspected overdose. She was found by her partner unresponsive. On arrival: respiratory rate 6 breaths per minute, heart rate 55 beats per minute, blood pressure 90/60 mmHg, oxygen saturation 88% on room air, GCS 8, pinpoint pupils.

Question: A. What is the appropriate observation period for this patient and why? B. What specific complications are associated with methadone overdose?

Model Answer:

A. Observation period: 12-24 hours (2 marks)

Rationale:

• Methadone has a long elimination half-life (24-36 hours) compared to naloxone (30-90 minutes) (1 mark)
• Risk of delayed and rebound respiratory depression (1 mark)
• Methadone peak respiratory depression can occur 2-4 hours after ingestion but may be delayed up to 24 hours (1 mark)

B. Specific complications:

• QT prolongation and torsades de pointes (ventricular arrhythmia) (1 mark)
• Cardiac arrest due to polymorphic ventricular tachycardia (1 mark)
• Electrolyte abnormalities (hypokalaemia, hypomagnesaemia) exacerbating QT prolongation (1 mark)
• Risk is higher with high doses, drug interactions (CYP3A4 inhibitors), and pre-existing cardiac disease (1 mark)

Examiner Notes:

• Accept: "24 hours observation" for full marks
• Do not accept: "4-6 hours" (this is for short-acting opioids like heroin)
• Accept: "Arrhythmias" or "heart problems" for 0.5 marks only (specific arrhythmia required for full marks)
• Accept: "Long half-life" as sufficient explanation for extended observation

Question 3 (8 marks)

Stem: A 28-year-old male was brought to the emergency department 4 hours ago with opioid overdose. He received 1.2 mg naloxone (total) and initially responded well. He is currently awake with GCS 15, respiratory rate 14 breaths per minute, oxygen saturation 97% on room air. You are preparing to discharge him, but the nurse calls you urgently as he is now unresponsive with respiratory rate 5 breaths per minute.

Question: A. What is happening in this patient and why? B. How will you manage this scenario?

Model Answer:

A. Diagnosis: Rebound respiratory depression (1 mark)

Mechanism:

• Naloxone duration of action (30-90 minutes) is shorter than the opioid's half-life (3-4 hours for heroin, longer for methadone) (1 mark)
• The patient has metabolised the naloxone but still has active opioid in circulation (1 mark)
• This is a common phenomenon requiring extended observation (1 mark)

B. Management:

• Immediate: Airway protection, bag-mask ventilation, high-flow oxygen (1 mark)
• Naloxone: 400 micrograms IV/IM/IN immediately, repeat every 2-3 minutes until adequate ventilation (1 mark)
• Consider naloxone infusion: 2/3 of total bolus dose per hour (e.g., 0.8 mg/hour if 1.2 mg total required) (1 mark)
• Admit for extended observation: 12-24 hours (1 mark)
• Avoid premature discharge; ensure respiratory rate sustained above 12 for 2 hours without naloxone before discharge consideration (1 mark)

Examiner Notes:

• Accept: "Naloxone wearing off" for full marks
• Accept: "Respiratory depression again" (vague) for 0.5 marks only
• Do not accept: "New overdose" without explanation
• Accept: "Admit" without specifying observation period (0.5 marks)
• Do not accept: Discharge after this episode (must admit)

Question 4 (8 marks)

Stem: A 35-year-old female presents via ambulance after heroin overdose. She received 0.8 mg naloxone IM by paramedics and initially responded. On arrival: respiratory rate 12 breaths per minute, heart rate 72 beats per minute, blood pressure 105/65 mmHg, oxygen saturation 96% on 2 L/min oxygen, GCS 14, pinpoint pupils. One hour later, she develops acute respiratory distress with SpO2 88% on 15 L/min oxygen, bilateral crackles on auscultation, and pink frothy sputum.

Question: A. What is the likely diagnosis? B. Outline the management of this condition in the context of opioid overdose.

Model Answer:

A. Diagnosis: Non-cardiogenic pulmonary oedema (acute respiratory distress syndrome) secondary to opioid overdose (2 marks)

Distinguishing features:

• Onset 30-60 minutes after overdose and naloxone administration (1 mark)
• Bilateral crackles, pink frothy sputum, hypoxaemia refractory to naloxone and oxygen (1 mark)

B. Management:

• Supplemental oxygen: High-flow oxygen (15 L/min) via non-rebreather mask, target SpO2 94-98% (1 mark)
• Non-invasive ventilation: CPAP (10-15 cmH2O) or high-flow nasal cannula (30-60 L/min) if moderate respiratory distress (1 mark)
• Invasive ventilation: Intubation and mechanical ventilation if severe respiratory failure (PaO2/FiO2 below 200), GCS below 8, or worsening acidosis (1 mark)
• Ventilator strategy: Tidal volume 6-8 mL/kg, PEEP 5-10 cmH2O, plateau pressure below 30 cmH2O (1 mark)
• Diuretics: Consider furosemide 20-40 mg IV if fluid overload suspected (rarely required in pure opioid-induced pulmonary oedema) (1 mark)
• ICU admission: Mandatory for invasive ventilation or persistent hypoxaemia (1 mark)

Examiner Notes:

• Accept: "Pulmonary oedema" for full marks
• Do not accept: "Pneumonia" or "aspiration" as primary diagnosis
• Accept: "CPAP" or "high-flow" for non-invasive ventilation
• Do not accept: Diuretics as first-line (supportive care and ventilation are primary)
• Accept: "Intubate" without specifying criteria (0.5 marks)

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Australian Guidelines

ARC/ANZCOR

• Guideline 9.3 (Opioid Overdose): Naloxone administration 400 micrograms IV/IM/IN for adults, repeat every 2-3 minutes until adequate ventilation. Intranasal naloxone 2 mg (1 mg per nostril) for community first responders. Prioritise airway protection and ventilation support. [67]
• Key differences from AHA/ERC: ARC recommends intranasal naloxone as first-line for community first responders (2 mg total). AHA/ERC recommend IM route for community use. ARC emphasises ventilation support before naloxone in respiratory arrest.

Therapeutic Guidelines

• Therapeutic Guidelines: Toxicology and Wilderness:
  • "Opioid overdose: Immediate naloxone 400 micrograms IV/IM/IN, repeat as required."
  • "Naloxone infusion: 2/3 of total bolus dose per hour for long-acting opioids or rebound respiratory depression."
  • "Observation: 4-6 hours for short-acting opioids, 12-24 hours for long-acting opioids."
  • "Pulmonary oedema: Supportive care with oxygen and non-invasive ventilation; intubation if severe."
  • "QT prolongation (methadone): ECG monitoring, correct electrolyte abnormalities, consider alternative opioid if QT above 500 ms. [68]"

State-Specific

• NSW Health Clinical Guidelines (Opioid Dependence):

  • "Take-home naloxone program: All patients with opioid use disorder should be prescribed intranasal naloxone (4 mg kit)."
  • "Opioid substitution therapy: Buprenorphine preferred over methadone for new patients due to lower overdose risk."
  • "Emergency department naloxone protocols: All EDs must have intranasal naloxone available (2 mg and 4 mg kits). [69]"

• Queensland Health (Opioid Overdose):

  • "Statewide naloxone distribution program: Community pharmacies, needle exchanges, Aboriginal Medical Services."
  • "Rural and remote considerations: Royal Flying Doctor Service carries naloxone kits for pre-hospital use. [70]"

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Remote/Rural Considerations

Pre-Hospital

Ambulance Protocols:

• Intranasal naloxone (2 mg total) for suspected opioid overdose
• Repeat naloxone 2 mg every 5 minutes if inadequate response
• Bag-mask ventilation if respiratory rate below 8 or SpO2 below 90%
• Transport to nearest hospital with emergency department
• Consider retrieval for ICU transfer if local hospital lacks critical care facilities

Resource-Limited Setting

Limited Access to Advanced Care:

• Basic airway equipment: Oropharyngeal and nasopharyngeal airways, bag-mask devices
• Oxygen: Ensure adequate supply (cylinders, concentrators)
• Naloxone availability: Maintain stock of intranasal and intravenous formulations
• Monitoring: Pulse oximetry essential; limited access to arterial blood gas analysis

Modified Approach:

• Lower threshold for early intubation if prolonged transport times to tertiary centre
• Consider extended observation (24 hours) for all opioid overdoses due to limited follow-up
• Telemedicine consultation with toxicology or addiction medicine for complex cases

Retrieval

Criteria for Retrieval:

• Rebound respiratory depression requiring naloxone infusion
• Intubated or requiring mechanical ventilation
• Non-cardiogenic pulmonary oedema requiring ICU-level care
• Synthetic opioid overdose (fentanyl, carfentanil) with prolonged respiratory depression
• Comorbidities requiring specialist input (cardiac arrhythmias, hepatic failure)
• Pregnancy with opioid overdose (obstetric and neonatal care required)

RFDS (Royal Flying Doctor Service) Considerations:

• RFDS aircraft carry naloxone, ventilation equipment, and critical care monitoring
• Retrieval team includes emergency medicine physician and critical care nurse
• Coordination with local hospital: Stabilise patient, gather clinical information, arrange transfer

Retrieval Medicine Principles:

• Stabilise before transport: Secure airway, ensure adequate ventilation, correct hypoxaemia
• Naloxone infusion during transport: 2/3 of total bolus dose per hour
• Continuous monitoring: Pulse oximetry, ECG, capnography if intubated
• Documentation: Detailed timeline of naloxone administration, response, and complications

Telemedicine

Remote Consultation Approach:

• Video consultation with tertiary toxicology service for complex overdoses
• Guidance on naloxone dosing, observation periods, and disposition
• Facilitation of addiction medicine referral and opioid substitution therapy
• Cultural safety: Involve Aboriginal Medical Services or Māori health providers for cultural liaison

Limitations of Remote Care:

• Inability to perform physical examination (reliance on local clinical assessment)
• Limited access to advanced diagnostics (toxicology screening, echocardiography)
• Communication barriers: Interpreter services, cultural considerations
• Logistics: Medication delivery, patient transport, follow-up coordination

---

References

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Non-Cardiogenic Pulmonary Oedema

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Synthetic Opioids

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Mixed Overdose and Co-ingestants

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Acetaminophen Toxicity

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Pregnancy and Opioid Use

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Indigenous Health

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Take-Home Naloxone and Harm Reduction

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Emergency Department Management

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Systematic Reviews and Meta-Analyses

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Remote/Rural and Retrieval Medicine

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