Figure Severe CAP — the sepsis hour-1 bundle is non-negotiable: antibiotics within ONE HOUR (each hour delay raises mortality). Empiric beta-lactam plus macrolide (or respiratory fluoroquinolone); add anti-pseudomonal cover if risk, MRSA cover if post-influenza or cavitary. De-escalate at 48-72 h. Severe CAP ICU pathway (hour-1) : cultures + lactate + antibiotics within 1 hour + goal-directed fluids + vasopressors if shock. Empiric therapy (IDSA/ATS 2019): STANDARD — beta-lactam (ceftriaxone) + macrolide (azithromycin) OR beta-lactam + respiratory fluoroquinolone (moxifloxacin). SEVERE/ICU — beta-lactam + macrolide (or fluoroquinolone). PSEUDOMONAS risk — anti-pseudomonal beta-lactam (pip-tazo, cefepime) + ciprofloxacin or aminoglycoside + macrolide. MRSA risk — add vancomycin/linezolid. De-escalate at 48-72h (cultures). Duration 5-7 days (afebrile 48-72h + improved; PCT-guided — PRORATA).
[3]
[16]
[3]
[11]
SAQ — Severe CAP in the ICU: empiric therapy and complications
SAQ — Severe community-acquired pneumonia with septic shock 10 minutes · 10 marks
Reveal all A 67-year-old man with a 40 pack-year smoking history and COPD presents with 3 days of fever, productive cough and dyspnoea. He is confused, RR 34, SpO2 88% on room air, BP 82/48 after 2 L crystalloid, HR 128, temperature 38.9C. CXR shows right lower and middle lobe consolidation. Lactate 4.1 mmol/L, WCC 18, urea 12 mmol/L, Na 128. CURB-65 score 4. Blood cultures and sputum have been sent.
a Outline your initial ICU management including your empiric antibiotic regimen and doses. Justify your choices with reference to severity scores and risk factors. (5 marks)
b Discuss the role of procalcitonin in guiding antibiotic duration in this patient, with reference to relevant evidence. (3 marks)
c What complications of severe CAP should you actively monitor for during his ICU stay? (2 marks)
[3]
SAQ — Post-influenza necrotising MRSA pneumonia 10 minutes · 10 marks
Reveal all A 54-year-old woman is admitted to ICU 5 days after the onset of influenza A (confirmed on nasopharyngeal PCR). She has deteriorated with high fever, copious bloody sputum, septic shock and rapidly progressive multilobar cavitary infiltrates on CXR. WCC 26, platelets 80, INR 1.8, creatinine 210 micromol/L. She was previously well. Sputum Gram stain shows gram-positive cocci in clusters.
a What is the likely diagnosis and how would you tailor her empiric antibiotic therapy? Justify your choices with doses. (5 marks)
b Discuss the evidence and dosing of oseltamivir in critically ill influenza, including the timing question. (3 marks)
c What other bacteria commonly superinfect influenza, and why does this matter for empiric cover? (2 marks)
[4]
Clinical pearls
High-yield severe CAP ICU points for CICM/FFICM exam
Antibiotics within 1 HOUR — mortality rises with delay. (1) EVIDENCE: (a) Seymour (2017, NEJM): in sepsis, each HOUR delay in antibiotics -> ~4% increase in mortality (after adjusting for severity). (b) Kumar (2006): in septic shock, each hour delay after hypotension -> 7.6% increase in mortality. (c) Ferrer (2014): early antibiotics reduce mortality in severe sepsis/septic shock. (2) RATIONALE: (a) Severe CAP = sepsis (infection -> SIRS -> organ dysfunction). (b) The infection is progressing (bacteria multiplying, toxins spreading). (c) Antibiotics STOP the progression — but each hour of delay -> more bacterial load + more inflammation + more organ damage. (d) EARLY = before the inflammatory cascade is fully established -> better outcomes. (3) PRACTICE: give antibiotics IMMEDIATELY (within 1 hour) — BEFORE full workup if needed (take cultures first if possible, but don't delay antibiotics for cultures beyond a few minutes). (4) KEY: 'shoot first' (antibiotics) — the cost of unnecessary antibiotics (one dose) is FAR less than the cost of delayed antibiotics (death).[2] }Typical vs atypical pathogens — cover BOTH. (1) TYPICAL (bacteria — Gram stain visible): (a) Streptococcus pneumoniae (MOST COMMON — 30-50% of CAP). (b) Haemophilus influenzae (especially COPD). (c) Moraxella catarrhalis (COPD). (d) Staphylococcus aureus (post-influenza, cavitary). (e) Gram-negatives (Klebsiella — especially alcoholic, Pseudomonas — bronchiectasis). (2) ATYPICAL (not seen on Gram stain — need special culture/serology/PCR): (a) Legionella pneumophila (severe CAP, hyponatraemia, GI symptoms, confusion — Legionnaires' disease). (b) Mycoplasma pneumoniae (young, mild — 'walking pneumonia' — but can be severe). (c) Chlamydia pneumoniae. (d) Chlamydia psittaci (birds — psittacosis). (e) Coxiella burnetii (Q fever — livestock). (3) VIRUSES (increasingly recognised — up to 30% of CAP): influenza, COVID, RSV, adenovirus. (4) EMPIRIC COVER: (a) Beta-lactam (penicillin/cephalosporin) covers TYPICAL. (b) MACROLIDE (azithromycin) or fluoroquinolone (moxifloxacin) covers ATYPICAL. (c) BOTH needed (beta-lactam alone misses atypicals — Legionella, Mycoplasma). (d) ADD antiviral (oseltamivir) in influenza season. (5) THE RATIONALE: severe CAP — can't wait for cultures -> cover ALL likely organisms empirically -> de-escalate when results available.[1] }Pseudomonas risk factors — know when to cover. (1) RISK FACTORS for Pseudomonas CAP: (a) BRONCHIECTASIS (structural lung disease — chronically colonised). (b) PRIOR PSEUDOMONAS isolation (within 1 year — likely still colonised). (c) RECENT HOSPITALISATION or antibiotics (healthcare-associated — resistant organisms). (d) Severe COPD (frequent exacerbations + antibiotics). (e) IMMUNOCOMPROMISED (neutropenia, transplant, chemotherapy — broader organisms). (2) WHY PSEUDOMONAS IS DANGEROUS: (a) RESISTANT (many strains — ESBL, carbapenemase). (b) AGGRESSIVE (causes necrotising pneumonia — cavitary). (c) High mortality in severe CAP (if not covered empirically). (3) EMPIRIC COVER: (a) Anti-PSEUDOMONAL beta-lactam: pip-tazo, cefepime, meropenem (NOT ceftriaxone — doesn't cover Pseudomonas). (b) SECOND agent: ciprofloxacin OR aminoglycoside (gentamicin/tobramycin) — dual anti-pseudomonal (synergy + resistance prevention). (c) + atypical cover (azithromycin or levofloxacin — levofloxacin has some Pseudomonas activity). (4) DE-ESCALATE: if cultures show no Pseudomonas -> switch to standard (ceftriaxone + azithromycin). (5) AVOID: routine anti-pseudomonal for all CAP (overuse -> resistance) — only for RISK factors.[6] }MRSA risk factors — post-influenza and cavitary. (1) RISK FACTORS for MRSA CAP: (a) POST-INFLUENZA (S. aureus — including MRSA — superinfects influenza lung damage — high mortality). (b) CAVITARY infiltrates (S. aureus causes necrotising pneumonia — cavities). (c) Recent hospitalisation or healthcare exposure (MRSA colonisation). (d) End-stage renal disease (dialysis — high MRSA carriage). (e) Prior MRSA infection/colonisation. (f) Injection drug use. (2) WHY MRSA IS DANGEROUS: (a) Necrotising pneumonia (Panton-Valentine leukocidin — PVL — toxin — causes tissue destruction). (b) High mortality (especially post-influenza). (c) Requires specific cover (vancomycin/linezolid — NOT covered by standard beta-lactams). (3) EMPIRIC COVER: (a) ADD VANCOMYCIN 15-20 mg/kg q8-12h (target trough 15-20 or AUC 400-600). (b) OR LINEZOLID 600 mg q12h (if vancomycin allergy, renal failure, or concern for PVL — linezolid suppresses toxin production). (c) ADD to standard CAP regimen (ceftriaxone + azithromycin + vancomycin). (4) DE-ESCALATE: if cultures negative for MRSA -> STOP vancomycin/linezolid. (5) POST-INFLUENZA: ALWAYS add MRSA cover if severe CAP after influenza (high risk).[6] }De-escalation at 48-72h — antimicrobial stewardship. (1) WHY DE-ESCALATE: (a) Reduces RESISTANCE (narrow -> less selection pressure). (b) Reduces C. DIFFICILE. (c) Reduces SIDE EFFECTS (nephrotoxicity — vancomycin; QT — azithromycin). (d) Reduces COST. (2) WHEN: at 48-72 hours (when cultures available). (3) HOW: (a) REVIEW cultures: (i) Blood + sputum: organism identified -> narrow to specific (e.g., S. pneumoniae -> penicillin/ceftriaxone; Legionella -> azithromycin/levofloxacin alone; H. influenzae -> ampicillin/ceftriaxone). (ii) STOP unnecessary: if no Pseudomonas -> stop anti-pseudomonal; if no MRSA -> stop vancomycin; if no anaerobes -> stop metronidazole. (iii) STOP atypicals if identified typical (e.g., S. pneumoniae confirmed -> can stop macrolide — UNLESS concern for co-infection). (b) IF CULTURES NEGATIVE + clearly CAP (radiographic + clinical) -> continue narrow-spectrum empiric (ceftriaxone + azithromycin — culture-negative CAP common — ~50%). (c) IF CULTURES NEGATIVE + alternative diagnosis (PE, heart failure, haemorrhage) + low PCT -> STOP antibiotics (no infection). (4) PCT-GUIDED (PRORATA): stop when PCT <0.5 or falls 80% from peak — reduces duration without worsening outcomes. (5) DURATION after de-escalation: 5-7 days total (or PCT-guided).[3] }Legionella — the severe CAP with extra-pulmonary features. (1) LEGIONELLA PNEUMOPHILA (serogroup 1 — most common pathogenic): (a) SEVERE CAP (especially ICU — 2-8% of severe CAP). (b) EXCELLENT extrapulmonary features (distinguishes from other CAP). (2) CLINICAL: (a) GI: diarrhoea, nausea, abdominal pain (common — 30-50%). (b) NEUROLOGICAL: confusion, headache (Legionella affects brain — 'Legionnaires' encephalopathy'). (c) RENAL: AKI, proteinuria, haematuria. (d) HEPATIC: elevated transaminases. (e) HYPONATRAEMIA (SIADH — Legionella classic). (f) FEVER (high), relative bradycardia (classic — but non-specific). (g) DISEASE PROGRESSION: rapid — multilobar infiltrates within 24-48h. (3) DIAGNOSIS: (a) URINARY LEGIONELLA ANTIGEN (sensitive for serogroup 1 — most common — RAPID — within hours). (b) SPUTUM/RESPIRATORY CULTURE (special media — BCYE agar — slow — takes 3-5 days). (c) PCR (rapid — if available). (d) SEROLOGY (paired — 4-fold rise — retrospective). (4) TREATMENT: (a) MACROLIDE (azithromycin 500 mg) OR FLUOROQUINOLONE (levofloxacin 750 mg, moxifloxacin 400 mg). (b) SEVERE: fluoroquinolone (better tissue penetration — some evidence). (c) DURATION: 7-14 days (longer than typical — Legionella is intracellular). (5) SOURCE: contaminated water (cooling towers, hot tubs, plumbing — 'Legionnaires' from 1976 Philadelphia legion convention — air conditioning cooling tower). (6) REPORT: notifiable disease (public health — investigate source — prevent outbreak).[4] }Procalcitonin — antibiotic stewardship marker. (1) PCT (procalcitonin): (a) Normally produced by THYROID (as precursor of calcitonin). (b) In BACTERIAL infection: produced by EXTRA-THYROID tissues (liver, lung, monocytes) -> rises in serum. (c) In VIRAL infection or NON-INFECTIOUS inflammation: PCT stays LOW (viral interferon-gamma suppresses PCT production). (2) ROLE: (a) DISTINGUISH bacterial from viral/non-infectious (bacterial -> high PCT; viral -> low). (b) GUIDE antibiotic INITIATION (PCT <0.1 — unlikely bacterial -> consider not starting). (c) GUIDE antibiotic DURATION (PRORATA — stop when PCT <0.5 or falls 80% — reduces duration). (3) LIMITATIONS: (a) Early bacterial infection: PCT may be low (takes 6-24h to rise — repeat if initially low). (b) Severe sepsis/septic shock: PCT very high (but non-specific — any severe bacterial infection). (c) Trauma/surgery: PCT rises (non-infectious inflammation — misleading). (d) Immunocompromised: PCT may be blunted. (e) NOT perfect (false positives/negatives) — use WITH clinical judgement. (4) PRACTICE: PCT trend (falling = responding to antibiotics; rising = failing/ongoing infection). Stop antibiotics when PCT <0.5 or falls 80%. Don't rely on a single value — trend + clinical.[3] }Empyema — pleural infection. (1) DEFINITION: pus in pleural space (pleural empyema) OR pleural fluid with pH <7.2 (biochemical evidence of infection). (2) STAGES: (a) EXUDATIVE (stage I — free-flowing fluid, sterile): treat with antibiotics. (b) FIBRINOPURULENT (stage II — fibrin deposition, loculation, infected): antibiotics + DRAINAGE (chest tube). (c) ORGANISING (stage III — thick peel, trapped lung): surgery (VATS decortication). (3) DIAGNOSIS: (a) PLEURAL FLUID (thoracentesis — if effusion present): (i) pH <7.2 -> empyema (drain). (ii) pH >7.2 -> uncomplicated parapneumonic (antibiotics only). (iii) ALSO: glucose <2.2, LDH >1000, Gram stain/culture (positive = empyema). (iv) PUS (macroscopic) -> empyema (drain). (b) IMAGING: CXR (effusion), CT (loculation, size, guide drainage), ultrasound (guide thoracentesis/drains). (4) MANAGEMENT: (a) ANTIBIOTICS (longer than uncomplicated CAP — 4-6 weeks — empyema is deep infection). (b) CHEST TUBE drainage (if empyema — pH <7.2 or pus). (c) INTRAPLEURAL FIBRINOLYTICS (tPA + DNase — if loculated — MIST trial — improves drainage). (d) SURGERY (VATS — video-assisted thoracoscopic surgery — decortication): if drainage fails, loculated, organising (stage III). (e) NUTRITION (empyema is catabolic — high protein). (5) MORTALITY: 10-20% (higher in elderly, comorbidities, delayed drainage).[5] }Lung abscess — cavitary lesion. (1) DEFINITION: localised collection of pus in lung (cavity with air-fluid level). (2) CAUSES: (a) ASPIRATION (most common — alcoholism, seizures, impaired consciousness, dysphagia — mixed anaerobic + aerobic infection). (b) POST-PNEUMONIA (S. aureus, Klebsiella, Pseudomonas — necrotising pneumonia). (c) BRONCHIAL OBSTRUCTION (tumour, foreign body — post-obstructive infection). (d) HAEMATOGENOUS (septic emboli — endocarditis, Lemierre). (3) ORGANISMS: anaerobes (Bacteroides, Peptostreptoccus, Fusobacterium — aspiration), S. aureus, Klebsiella, Pseudomonas, MRSA. (4) DIAGNOSIS: (a) CT chest (cavity with air-fluid level + thick wall). (b) Sputum culture (may miss anaerobes — need special culture or BAL). (c) Bronchoscopy (exclude obstruction — tumour, foreign body). (5) MANAGEMENT: (a) ANTIBIOTICS (LONG course — 4-6 weeks — until cavity resolves on CT). (b) Anaerobic cover (clindamycin, amoxicillin-clavulanate, or carbapenem). (c) ADD organism-specific (S. aureus -> vancomycin/linezolid if MRSA). (d) DRAINAGE (percutaneous or surgical — if large, fails medical, or rupture risk). (e) TREAT underlying (aspiration — dental, swallowing; obstruction — tumour resection, foreign body removal). (6) COMPLICATIONS: rupture into pleural space (empyema + bronchopleural fistula), massive haemoptysis (erosion into vessel), brain abscess (haematogenous spread). (7) MORTALITY: 5-10% (higher in elderly, immunocompromised, large abscess).[5] }Post-influenza CAP — MRSA superinfection. (1) INFLUENZA damages respiratory epithelium -> creates environment for bacterial SUPERINFECTION (post-viral bacterial pneumonia). (2) COMMON SUPERINFECTING ORGANISMS: (a) S. aureus (including MRSA — the classic post-influenza — high mortality — PVL toxin causes necrotising pneumonia). (b) S. pneumoniae. (c) H. influenzae. (d) Group A Streptococcus. (3) CLINICAL: (a) Patient with influenza (or recovering) -> DETERIORATION (new fever, worsening respiratory distress, new infiltrates). (b) TIMING: 3-14 days after influenza onset (post-viral). (4) DIAGNOSIS: sputum/blood cultures (S. aureus), viral PCR (influenza — may still be positive), CT (cavitary if S. aureus). (5) MANAGEMENT: (a) ANTIBIOTICS: ALWAYS add MRSA cover (vancomycin/linezolid) + standard CAP (ceftriaxone + azithromycin). (b) OSELTAMIVIR (if influenza still active — continue). (c) AGGRESSIVE support (these patients are SICK — high mortality — often need ventilation, vasopressors, ECMO). (6) PREVENTION: INFLUENZA VACCINATION (reduces influenza -> reduces post-influenza CAP). (7) This is a HIGH-YIELD exam topic — 'patient with flu, now deteriorating with cavitary pneumonia -> post-influenza MRSA CAP.'[4] }Steroids in severe CAP — controversial. (1) RATIONALE: (a) Severe CAP -> excessive INFLAMMATION (cytokine storm, SIRS). (b) Steroids SUPPRESS inflammation -> may reduce lung injury, improve outcomes. (2) EVIDENCE: (a) CONFLICTING — some trials benefit (Meduri 2007 — methylprednisolone reduced mortality in severe CAP; Torres 2015 — dexamethasone reduced treatment failure). (b) OTHERS no benefit or harm (NIH NHLBI CAPO trials — heterogeneous). (c) META-ANALYSES: trend to benefit in SEVERE CAP (but not consistently significant). (3) IDSA/ATS 2019: recommends AGAINST routine steroids (insufficient evidence — risk of harm — immunosuppression, hyperglycaemia, delayed clearance). (4) CONSIDER steroids in: (a) REFRACTORY SEPTIC SHOCK (ADRENAL — hydrocortisone 200 mg/day — if vasopressor-dependent). (b) SEVERE CAP with HIGH INFLAMMATORY BURDEN (very high CRP, cytokines — controversial — some specialists). (c) UNDERLYING condition requiring steroids (COPD exacerbation, asthma, adrenal insufficiency). (5) CAUTION: (a) May DELAY bacterial clearance (immunosuppression). (b) Hyperglycaemia (infection). (c) GI bleed. (d) Delirium. (6) PRACTICE: NOT routine; consider in selected severe (refractory shock, high inflammation) — discuss with ID/respirology.[1] }Vaccination — prevention. (1) PNEUMOCOCCAL: (a) PCV13 (13-valent conjugate — children, immunocompromised, >65 in some guidelines). (b) PPSV23 (23-valent polysaccharide — adults >65, chronic disease, immunocompromised — CAPRIE — reduces invasive pneumococcal disease). (2) INFLUENZA (annual — all adults >65, chronic disease, healthcare workers, pregnancy — reduces influenza + post-influenza CAP). (3) COVID (reduces severe COVID pneumonia). (4) H. INFLUENZAE type b (Hib — children — less relevant for adult CAP). (5) RSV (newer — for elderly, chronic disease). (6) GIVE at DISCHARGE (after severe CAP) — vaccination reduces recurrence. (7) BARRIERS: vaccine hesitancy, access, storage. (8) PUBLIC HEALTH: herd immunity (especially influenza — protects vulnerable).[1] }Immunocompromised CAP — broader differential. (1) IMMUNOCOMPROMISED patients (transplant, chemotherapy, HIV, immunosuppression) have BROADER differential: (a) BACTERIAL: same as immunocompetent + Pseudomonas, Gram-negatives, Nocardia. (b) PNEUMOCYSTIS JIROVECI (PJP/PCP — especially CD4 <200, steroid use — bilateral interstitial infiltrates, hypoxaemia out of proportion, elevated LDH). (c) FUNGAL: Aspergillus (especially neutropenic, transplant — invasive), Cryptococcus, endemic fungi (Histoplasma, Coccidioides). (d) VIRAL: CMV (transplant), HSV, VZV, severe influenza/COVID/RSV. (e) MYCOBACTERIA: TB, atypical (MAI). (2) DIAGNOSIS: (a) BROADER workup — BAL (bronchoalveolar lavage — for PJP stain, CMV PCR, fungal galactomannan, AFB). (b) CT chest (more sensitive — PJP interstitial, fungal nodules/halo). (c) Beta-D-glucan (PJP, fungal), galactomannan (Aspergillus). (d) Biopsy (if non-resolving — invasive). (3) EMPIRIC THERAPY: (a) BROADER — anti-pseudomonal beta-lactam + macrolide. (b) ADD PJP cover (co-trimoxazole — high-dose — if CD4 <200 or suspicion). (c) ADD antifungal/antiviral if suspicion. (d) LOWER threshold for BAL (need to identify organism — atypicals not covered by standard). (4) MORTALITY: higher (immunosuppression + aggressive organisms). (5) COORDINATE: ID, transplant/infectious disease, haematology.[6] }Follow-up + CXR at 6 weeks. (1) CXR at 6 WEEKS after CAP (routine — to ensure RESOLUTION): (a) Most CAP resolves radiographically within 6-8 weeks. (b) If NOT resolved (persistent infiltrate) -> investigate: (i) Underlying LUNG CANCER (5-10% of CAP have underlying malignancy — especially smoker, elderly — 'post-obstructive pneumonia' — tumour blocks bronchus -> infection). (ii) TB (if risk factors). (iii) Bronchiectasis. (iv) Immunodeficiency. (v) Aspiration (recurrent). (2) INVESTIGATE non-resolution: (a) CT chest (better detail — mass, cavity, bronchiectasis). (b) Bronchoscopy (if mass/obstruction — biopsy). (c) Sputum AFB (TB). (3) SMOKING CESSATION (reduces recurrence — smoking impairs cilia, macrophages). (4) VACCINATION (pneumococcal, influenza, COVID — reduce recurrence). (5) RECURRENT CAP: if ≥2 episodes -> investigate (immunodeficiency, structural lung disease, aspiration). (6) PATIENT EDUCATION: complete antibiotic course, return if worsening, follow-up CXR, vaccination, smoking cessation.[1] }CURB-65 — the quick bedside severity score. (1) CURB-65 is a 5-variable score: C onfusion (new-onset disorientation in person, place, or time — marks cerebral hypoperfusion/toxicity), U rea >7 mmol/L (renal dysfunction from dehydration/sepsis), R espiratory rate ≥30/min (respiratory compromise — the EARLIEST and most sensitive sign of clinical deterioration), B lood pressure (SBP <90 OR DBP ≤60 mmHg — septic shock/hypoperfusion), age ≥65 years (independent mortality risk factor). Each criterion scores 1 point; total 0-5. (2) INTERPRETATION (Lim 2003, Thorax): 0-1 = LOW risk (mortality ~1.5% — consider outpatient management). 2 = MODERATE (mortality ~9% — hospital admission, consider short-stay unit). 3 = HIGH (mortality ~15% — hospital, consider ICU). 4-5 = VERY HIGH (mortality 25-40% — ICU admission strongly recommended). (3) ADVANTAGE: SIMPLE — can calculate at bedside in <1 minute. Only one lab (urea) needed. Validated internationally. (4) LIMITATION: (a) Less sensitive than PSI for identifying low-risk patients (risk of false 'moderate' classification). (b) Does NOT incorporate O2 saturation (a critical marker of respiratory compromise). (c) Binary age cutoff (≥65) — does not weight by degree (an 80-year-old scores same as a 66-year-old). (d) Does not weight comorbidities. (5) CRB-65 variant (drop Urea) — for COMMUNITY use (no labs): 0 = outpatient, ≥1 = hospital, ≥2 = consider ICU. [7] } }PSI / PORT score — the comprehensive risk stratification. (1) PSI (Pneumonia Severity Index) / PORT (Pneumonia Patient Outcomes Research Team) score uses 20+ variables across 4 domains: (a) DEMOGRAPHICS: age (men), age-10 (women), nursing home resident (+10). (b) COMORBIDITIES: neoplastic disease (+30), liver disease (+20), CHF (+10), cerebrovascular disease (+10), renal disease (+10). (c) PHYSICAL EXAM: altered mental status (+20), RR ≥30 (+20), SBP <90 (+20), temp <35 or ≥40 (+15), HR ≥125 (+10). (d) LABS/RADIOLOGY: arterial pH <7.35 (+30), BUN ≥11 mmol/L (+20), Na <130 (+20), glucose ≥14 (+10), haematocrit <30% (+10), PaO2 <60 or O2 sat <90% (+10), pleural effusion (+10). (2) RISK CLASSES: I (low, outpatient, mortality <1%); II (low, outpatient, <1%); III (moderate, ward/observation, ~3%); IV (high, hospital, ~9%); V (very high, ICU/hospital, ~27%). (3) ADVANTAGE: MORE ACCURATE than CURB-65 for identifying low-risk patients (high sensitivity — few false negatives for safe discharge). Validated prospectively in 38,000+ patients (Fine 1997, NEJM). (4) LIMITATION: (a) COMPLEX — requires multiple labs (pH, BUN, Na, glucose, Hct, PaO2) and calculation. (b) AGE-WEIGHTED — a young patient with no comorbidities but severe acute physiology (high RR, low O2 sat, hypotensive) may still score 'low' despite being critically ill. PSI UNDER-weights acute physiological derangement relative to age and comorbidity. (c) Over-identifies moderate-risk patients for admission. (5) COMPLEMENTARY USE: many centres use CURB-65 for quick triage and PSI for formal risk documentation — neither is a substitute for clinical judgement. [8] } }IDSA/ATS severe CAP criteria — defines who needs ICU. (1) SEVERE CAP = 1 MAJOR criterion OR ≥3 MINOR criteria (from the 2007 IDSA/ATS consensus, reaffirmed in 2019). (2) MAJOR criteria (need any 1): (a) Invasive mechanical ventilation (severe respiratory failure, refractory hypoxaemia, fatigue). (b) Septic shock requiring vasopressors (severe perfusion failure). (3) MINOR criteria (need ≥3 of 9): (a) RR ≥30/min. (b) PaO2/FiO2 ≤250 (hypoxaemia — on room air or supplemental O2). (c) Multilobar infiltrates on CXR (bilateral or ≥2 lobes). (d) Confusion/disorientation (new onset). (e) BUN ≥20 mg/dL (≥7.1 mmol/L). (f) Leucopenia (WBC <4 ×10⁹/L — immunocompromise or severe sepsis bone marrow suppression). (g) Thrombocytopenia (platelets <100 ×10⁹/L). (h) Hypothermia (core temp <36°C — worse prognosis than fever). (i) Hypotension requiring aggressive fluid resuscitation ( crystalloids to maintain BP). (4) SENSITIVITY: the 3-minor-criteria threshold captures ~70-80% of ICU-admitted CAP; using 2 minor criteria increases sensitivity but decreases specificity (more false 'severe'). (5) LIMITATION: minor criteria require labs (not immediately available) — use CRB-65 or clinical judgement in the FIRST HOUR (don't delay antibiotics while calculating scores). (6) SMART-COP (Charles 2008, CID): alternative score predicting the need for Intensive Respiratory or Vasopressor Support (IRVS) — score ≥3 identifies patients likely to need ICU; uses SBP <90, multilobar CXR, low albumin, high RR, high HR, confusion, low PaO2, low pH. (7) EXAM TIP: know BOTH the major and minor criteria — this is a classic CICM/FFICM question ('What criteria define severe CAP requiring ICU admission?'). [1] } } [9] } } [17] } }Failure to respond (non-responding pneumonia) — systematic approach. (1) DEFINITION: lack of clinical improvement (or active deterioration) by 48-72 hours despite appropriate antibiotics. Most CAP patients achieve clinical stability (afebrile, HR <100, RR <24, SBP >90, SpO2 >90%, normal mental status, able to eat) within 3-5 days. (2) INCIDENCE: ~6-15% of hospitalised CAP patients fail to respond; higher in ICU (~30%). (3) CATEGORIES of non-response: (a) PROGRESSIVE (worsening in 24-72h — ~35% of non-responders): wrong pathogen/resistance (Pseudomonas, MRSA, ESBL, atypicals), complication (empyema, ARDS, metastatic infection), or alternative diagnosis (PE, heart failure, vasculitis). (b) STAGNANT (no improvement at 3-5 days — ~30%): inadequate antibiotic dosing or penetration, wrong organism (atypical, viral [influenza/COVID], fungal, TB), immunocompromise (HIV, neutropenia, transplant immunosuppression). (c) DETERIORATION after initial improvement (~35%): nosocomial superinfection (VAP after intubation, catheter-related bacteraemia), drug fever (beta-lactams, sulfa), new complication (PE, AF, MI). (4) MOST COMMON CAUSES: (a) Resistant or inappropriate organism (especially Pseudomonas in COPD/bronchiectasis — Arancibia 2002 showed Pseudomonas CAP has 2-3× higher mortality). (b) Complication (empyema, lung abscess, ARDS, PE). (c) Wrong diagnosis (PE mimics CAP; heart failure with bilateral infiltrates; organising pneumonia; vasculitis [ANCA]; malignancy with post-obstructive infection). (5) EVALUATION: (a) REPEAT cultures (blood x2, sputum/ETA, BAL if intubated). (b) CT chest (complications, alternative diagnosis — cavitation, abscess, effusion, PE, mass). (c) Thoracentesis if effusion (pH, glucose, LDH, Gram stain, culture — rule out empyema). (d) CTPA if PE suspected (D-dimer, sudden hypoxaemia, pleuritic pain). (e) Echocardiogram (endocarditis, heart failure, new murmur). (f) EXPANDED microbiology (Legionella urinary antigen, atypical serology/PCR, respiratory viral panel, AFB, fungal galactomannan, PJP if immunocompromised). (6) MANAGEMENT: (a) BROADEN empirically (meropenem + vancomycin + azithromycin) if deteriorating. (b) TREAT complications (drain empyema, debride abscess, anticoagulate PE, manage heart failure). (c) RECONSIDER DIAGNOSIS (consider non-infectious causes). (d) RE-DE-ESCALATE when results available. [4] } } [16] } }Corticosteroids in severe CAP — the CAPO evidence and controversy. (1) RATIONALE: severe CAP triggers excessive inflammation (cytokine cascade, SIRS, complement activation) → lung injury, ARDS, septic shock, multi-organ dysfunction. Corticosteroids dampen this inflammatory response by inhibiting NF-κB, cytokine transcription, and neutrophil activation. (2) KEY RCTs: (a) CONFALONIERI (2005, AJRCCM): hydrocortisone infusion (240mg/day × 7d then taper) in severe CAP → reduced multi-organ dysfunction score, improved survival (small study n=46, stopped early for benefit — overestimation risk). (b) TORRES (2015, JAMA): dexamethasone 20mg × 1 then 10mg/day × 5d in severe CAP with HIGH inflammation (CRP >150 mg/L) → reduced LATE treatment failure (day 5-9: 14% vs 34%, p=0.02); NO mortality benefit; increased hyperglycaemia. (c) BLUM (2015, Lancet — GLUCAN trial): prednisone 50mg/day × 7d in ALL hospitalised CAP → FASTER time to clinical stability (3 vs 4 days, HR 1.42), SHORTER LOS (6 vs 7 days); NO mortality benefit; more insulin-requiring hyperglycaemia (19% vs 11%). (3) CAPO META-ANALYSIS (Siemieniuk 2015, Ann Intern Med — INDIVIDUAL PATIENT DATA from the Corticosteroids in Pneumonia Outcome [CAPO] collaboration): (a) POOLED 13 RCTs (~2000 patients). (b) CORTICOSTEROIDS REDUCED: (i) all-cause MORTALITY (RR 0.67, driven by severe CAP — PSI IV-V); (ii) need for MECHANICAL VENTILATION (RR 0.44); (iii) DURATION of antibiotics; (iv) time to clinical STABILITY. (c) GREATER benefit in SEVERE CAP (PSI class IV-V — NNT ~10 for mortality); minimal benefit in non-severe CAP. (d) ADVERSE EFFECTS: hyperglycaemia requiring insulin increased (RR 1.8) — no increase in GI bleeding, neuromyopathy, or secondary infection. (4) IDSA/ATS 2019: recommends AGAINST routine corticosteroids in CAP (cites insufficient evidence for mortality, concerns about heterogeneity, hyperglycaemia, immunosuppression). (5) PRACTICE (consensus): many ICU clinicians USE corticosteroids selectively in SEVERE CAP with (a) high inflammatory burden (CRP >150 mg/L — Torres subgroup), (b) refractory SEPTIC SHOCK (hydrocortisone 200mg/day per ADRENAL/APROCCHSS), (c) ARDS (dexamethasone 6-12mg/day). Typical regimens: HYDROCORTISONE 200mg/day continuous infusion or q6h × 5-7d; or DEXAMETHASONE 6mg/day × 5-10d. (6) EXAM TIP: know that the IDSA/ATS 2019 does NOT recommend routine steroids, but be prepared to discuss the CAPO data — this is a common CICM/FFICM viva topic. [10] } } [11] } } [12] } } [13] } } [1] } }Mycoplasma pneumoniae — the atypical that can be severe. (1) EPIDEMIOLOGY: (a) MOST COMMON atypical pneumonia pathogen worldwide; endemic with 3-5-year EPIDEMIC cycles (outbreaks in closed communities: military barracks, university dormitories, nursing homes). (b) Typically affects young adults and school-age children ('walking pneumonia' — mild, ambulatory). (c) Usually MILD and outpatient, but 5-10% require hospitalisation; severe ICU cases are rare but occur, especially in immunocompromised or those with underlying lung disease. (2) CLINICAL FEATURES: (a) INSIDIOUS onset over days (viral-like prodrome: fever, malaise, headache, sore throat, myalgias). (b) PERSISTENT DRY cough (lasts weeks — often the presenting complaint). (c) CXR: PATCHY, unilateral, lower-lobe interstitial infiltrates (non-specific — CXR often looks WORSE than patient — 'clinical-radiological dissociation'). (d) WHITE BLOOD CELL COUNT often normal or mildly elevated (unlike bacterial CAP). (3) EXTRAPULMONARY MANIFESTATIONS (Mycoplasma has more than any other CAP pathogen — caused by molecular mimicry/cross-reactive antibodies — may dominate presentation): (a) SKIN: erythema multiforme, Stevens-Johnson syndrome (classic association). (b) NEUROLOGICAL: meningoencephalitis, transverse myelitis, Guillain-Barré syndrome, cranial nerve palsies. (c) HAEMATOLOGICAL: cold agglutinin autoimmune haemolytic anaemia (IgM anti-I on RBC surface — positive cold agglutinin test in ~50%). (d) CARDIAC: myocarditis, pericarditis (can be life-threatening). (e) GI: pancreatitis, hepatitis. (f) RENAL: glomerulonephritis. (g) MUSCULOSKELETAL: arthralgia, myositis. (4) DIAGNOSIS: (a) SEROLOGY: 4-fold rise in IgM/IgG in paired sera (2-4 weeks apart) — retrospective (not useful for acute management). (b) PCR: respiratory sample (sputum, NPA, BAL) — rapid, sensitive, specific — the preferred acute test. (c) COLD AGGLUTININS: positive in ~50%, non-specific (also positive in EBV, CMV, other viral). (d) CULTURE: possible but slow (weeks) and technically difficult — NOT routinely done. (5) TREATMENT: (a) MACROLIDE: azithromycin 500mg day 1 then 250mg daily (or 500mg daily for severe) — FIRST LINE. (b) FLUOROQUINOLONE: moxifloxacin 400mg daily or levofloxacin 750mg daily. (c) DOXYCYCLINE: 100mg BD. (d) CRITICAL: beta-lactams (penicillin, cephalosporins) are INEFFECTIVE — Mycoplasma has NO CELL WALL. (6) MACROLIDE RESISTANCE: rising globally (23S rRNA methylation — especially East Asia: China/Japan/Korea >70-90%; lower rates in Europe/North America ~10-15%). If macrolide treatment FAILURE (no improvement in 48-72h) → switch to fluoroquinolone or doxycycline. (7) SEVERE Mycoplasma CAP: rare but occurs — especially with extrapulmonary complications (encephalitis, myocarditis, SJS) or underlying immunodeficiency. [1] } }Respiratory fluoroquinolone vs macrolide — choosing the atypical cover. (1) BOTH classes cover atypicals (Legionella, Mycoplasma, Chlamydia, Coxiella) and are acceptable partners with a beta-lactam for severe CAP (IDSA/ATS 2019). (2) MACROLIDE (azithromycin, clarithromycin) — FIRST-LINE partner: (a) Excellent Legionella cover (azithromycin preferred over erythromycin — better tissue levels, fewer GI/IV side effects). (b) Anti-inflammatory effect (reduces cytokine production — may improve clinical stability). (c) Once-daily dosing (azithromycin — convenient). (d) Low cost. (e) LIMITATIONS: QT prolongation (check ECG — avoid with other QT drugs), GI upset, CYP3A4 inhibition (drug interactions — statins, warfarin), rising Mycoplasma resistance (23S rRNA — especially Asia). (3) RESPIRATORY FLUOROQUINOLONE (moxifloxacin, levofloxacin) — ALTERNATIVE partner or monotherapy (for beta-lactam allergy): (a) BROADER Gram-negative cover (levofloxacin has Pseudomonas activity; moxifloxacin covers anaerobes). (b) Excellent tissue penetration (alveolar macrophage concentration 10-20× serum). (c) Preferred if beta-lactam ALLERGY (covers typical + atypical as monotherapy). (d) Slightly superior to macrolide for Legionella (observational data — lower mortality with fluoroquinolone). (e) LIMITATIONS: QT prolongation (avoid combining with macrolide), ACHILLES TENDON rupture/tendinopathy (especially elderly, concurrent steroids, renal impairment), aortic dissection/aneurysm (FDA black box warning), CNS effects (lower seizure threshold, confusion, psychosis), C. difficile risk (highest of all CAP antibiotics), dysglycaemia (both hyper- and hypoglycaemia), photosensitivity. (4) WHEN TO CHOOSE FLUOROQUINOLONE over macrolide: (a) Beta-lactam allergy. (b) High suspicion of Legionella (fluoroquinolone may be marginally superior). (c) Macrolide-resistant Mycoplasma (fluoroquinolone is effective alternative). (d) Aspiration pneumonia (moxifloxacin covers anaerobes). (e) Severe COPD with Pseudomonas concern (levofloxacin — not moxifloxacin — has anti-Pseudomonal activity). (5) WHEN TO CHOOSE MACROLIDE over fluoroquinolone: (a) Known QT prolongation or aortic disease (though both prolong QT, fluoroquinolones have additional aortic risk). (b) Tendon risk factors (elderly, steroids, renal failure). (c) Seizure history. (d) Significant drug interactions (warfarin INR, theophylline levels). (e) Prior fluoroquinolone-related C. difficile. (6) CRITICAL INTERACTION: both macrolides and fluoroquinolones PROLONG QT — AVOID combining them unless absolutely necessary; if combined, continuous ECG monitoring is essential (risk of torsades de pointes). [1] } }Duration of therapy — the 5-7 day rule and procalcitonin guidance. (1) IDSA/ATS 2019: treat for a MINIMUM of 5 days, discontinue when the patient is CLINICALLY STABLE (afebrile for 48-72h + no more than 1 sign of clinical instability) and afebrile. Most patients need 5-7 days. (2) CLINICAL STABILITY CRITERIA (Halm criteria — meet all to be 'stable'): (a) Temperature ≤37.8°C. (b) HR ≤100/min. (c) RR ≤24/min. (d) SBP ≥90 mmHg. (e) SpO2 ≥90% on room air. (f) Able to maintain oral intake. (g) Normal mental status. Once stable + afebrile 48-72h → safe to stop or switch to oral. (3) SHORT-COURSE EVIDENCE: multiple RCTs show 5-day courses are NON-INFERIOR to longer courses for UNCOMPLICATED CAP (including a 2018 JAMA Internal Medicine trial of 5 vs 10 days). Shorter courses reduce C. difficile, resistance, side effects, and cost. (4) PCT-GUIDED DURATION (PRORATA — Schuetz 2018, Lancet): stop antibiotics when PCT <0.5 ng/mL OR falls ≥80% from peak — reduces duration by ~2-3 days WITHOUT increasing mortality, recurrence, or treatment failure. (5) LONGER COURSES (>7 days) REQUIRED for: (a) Legionella (7-14 days — azithromycin or fluoroquinolone). (b) MRSA pneumonia (7-14 days — vancomycin/linezolid). (c) Pseudomonas (7-14 days — anti-pseudomonal). (d) Complicated CAP (empyema 4-6 weeks, lung abscess 4-6 weeks, endocarditis, meningitis, metastatic infection). (e) Immunocompromised. (f) Slow clinical resolution or persistent bacteraemia. (6) ORAL SWITCH: switch to oral when (a) clinically stable (meets Halm criteria), (b) afebrile, (c) able to absorb oral (eating, no ileus), (d) improving CXR (or at least not worsening). Oral bioavailability of moxifloxacin/levofloxacin is >90% — no dose change needed. (7) DO NOT extend duration for persistent CXR infiltrates alone — radiographic resolution LAGS behind clinical resolution by 4-12 weeks (especially elderly, multilobar, Legionella). [1] } } [3] } } Red flags
Critical severe CAP red flags
Antibiotics within 1 HOUR (sepsis) — mortality rises ~4-8% per hour delay.[2] }Cover typical + atypical : beta-lactam + macrolide (or fluoroquinolone).[1] }Pseudomonas risk (bronchiectasis, prior, recent hospital) -> anti-pseudomonal cover.[6] }MRSA risk (post-influenza, cavitary) -> add vancomycin/linezolid.[6] }De-escalate at 48-72h (cultures) -> narrow, stop if no infection.[3] }Duration 5-7 days (afebrile 48-72h + improved; PCT-guided — PRORATA).[3] }Empyema : pH <7.2 or pus -> drain + antibiotics (4-6 weeks).[5] }Post-influenza MRSA CAP : high mortality -> ALWAYS add MRSA cover.[4] }Legionella : hyponatraemia + GI/neuro + severe -> urinary antigen.[4] }CXR at 6 weeks : ensure resolution — exclude underlying malignancy.[1] }CURB-65 ≥4 or PSI class V : severe CAP → ICU admission.[7] } }IDSA/ATS severe CAP : 1 major (MV, vasopressors) OR ≥3 minor criteria.[1] } }Non-responding by day 3-5 : reassess pathogen, antibiotic, complications — broaden empirically.[4] } }Corticosteroids : NOT routine (IDSA/ATS); consider in severe CAP + CRP >150 or refractory shock (CAPO data).[10] } } Prognosis
Severe CAP evidence and outcomes [3]
Corticosteroids in severe CAP — the CAPO evidence base [11]
Figure Exam overview — key physiology, red flags and first-hour management. Figure Stepwise ICU management: immediate priorities, disease-specific therapy, escalation. Figure Classification / severity framework used in written and viva answers. Densification notes for fellowship revision
This leaf is densified to the ICU fellowship gate standard (CICM / FFICM / EDIC): embedded SAQ practice, multi-figure visual scaffolding, examiner map alignment, and MCQ coverage of definition, mechanism, first-hour management, evidence, and traps.
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Revision checkpoint 1: restate definition, one number examiners expect, and one absolute do-not-miss action for severe-cap-icu-pathway-empiric-therapy .
Revision checkpoint 2: restate pathophysiology in one sentence and the first investigation that changes management.
Revision checkpoint 3: restate first-hour management priorities in order.
Revision checkpoint 4: restate the key severity or risk score and how it alters disposition.
Revision checkpoint 5: restate one landmark trial or guideline and its practical bedside message.
Revision checkpoint 6: restate the most dangerous treatment trap.
Revision checkpoint 7: restate monitoring targets for the first 24 hours.
Revision checkpoint 8: restate escalation criteria (what forces source control, advanced support, or transfer).
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[17] References [1] Metlay JP, et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America. American journal of respiratory and critical care medicine , 2019.PMID 31573350 [2] Seymour CW, et al. Time to Treatment and Mortality during Mandated Emergency Care for Sepsis. The New England journal of medicine , 2017.PMID 28528569 [3] Bouadma L, et al. Use of procalcitonin to reduce patients' exposure to antibiotics in intensive care units (PRORATA trial): a multicentre randomised controlled trial. Lancet (London, England) , 2010.PMID 20097417 [4] Martin-Loeches I, et al. Choosing antibiotic therapy for severe community-acquired pneumonia. Current opinion in infectious diseases , 2022.PMID 35190510 [5] Psallidas I, et al. Management of parapneumonic effusions and empyema. Seminars in respiratory and critical care medicine , 2014.PMID 25463162 [6] Amati F, et al. Emerging Resistance of Gram Negative Pathogens in Community-Acquired Pneumonia. Seminars in respiratory and critical care medicine , 2020.PMID 32629487 [7] Lim WS, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax , 2003.PMID 12728155 [8] Fine MJ, et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. The New England journal of medicine , 1997.PMID 8995086 [9] Charles PG, et al. SMART-COP: a tool for predicting the need for intensive respiratory or vasopressor support in community-acquired pneumonia. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America , 2008.PMID 18558884 [10] Siemieniuk RA, et al. Corticosteroid Therapy for Patients Hospitalized With Community-Acquired Pneumonia: A Systematic Review and Meta-analysis. Annals of internal medicine , 2015.PMID 26258555 [11] Torres A, et al. Effect of corticosteroids on treatment failure among hospitalized patients with severe community-acquired pneumonia and high inflammatory response: a randomized clinical trial. JAMA , 2015.PMID 25688779 [12] Confalonieri M, et al. Hydrocortisone infusion for severe community-acquired pneumonia: a preliminary randomized study. American journal of respiratory and critical care medicine , 2005.PMID 15557131 [13] Blum CA, et al. Adjunct prednisone therapy for patients with community-acquired pneumonia: a multicentre, double-blind, randomised, placebo-controlled trial. Lancet (London, England) , 2015.PMID 25608756 [14] Seymour CW, et al. Time to Treatment and Mortality during Mandated Emergency Care for Sepsis. The New England journal of medicine , 2017.PMID 28528569 [15] Kumar A, et al. Duration of hypotension before initiation of effective antimicrobial therapy is the critical determinant of survival in human septic shock. Critical care medicine , 2006.PMID 16625125 [16] Arancibia F, et al. Community-acquired pneumonia due to gram-negative bacteria and pseudomonas aeruginosa: incidence, risk, and prognosis. Archives of internal medicine , 2002.PMID 12196083 [17] Mandell LA, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America , 2007.PMID 17278083 
