Pneumonia, HAP & VAP in the ICU — Structured Guide

🫁 1 · Overview & Definitions

Pneumonia in the ICU

"Pneumonia reaches the ICU when it causes respiratory failure or septic shock. Two things drive outcome: timely, appropriate antibiotics, and matching the spectrum to the setting and the patient's resistance risk — then de-escalating. Delayed ICU admission or intubation in severe CAP costs lives."

Summarised from Irwin & Rippe's Intensive Care Medicine; with Marino's The ICU Book, Oh's Intensive Care Manual and ATS/IDSA.

Type	Definition
CAP — community-acquired	Onset in the community or <48 h after admission
HAP — hospital-acquired	≥48 h after admission, not incubating at admission
VAP — ventilator-associated	A subset of HAP developing ≥48 h after intubation
HCAP — healthcare-associated	Abandoned — use local epidemiology + individual MDR risk instead

🚦 2 · Severe CAP — ICU Criteria

Who needs the ICU (ATS/IDSA)

Major criteria (either = ICU)	Minor criteria (≥3 = ICU)
• Septic shock needing vasopressors • Respiratory failure needing mechanical ventilation	RR ≥30; P/F ≤250; multilobar infiltrates; confusion
	Uraemia (urea ≥20 mg/dL); leukopenia; thrombocytopenia; hypothermia; hypotension needing aggressive fluids

CURB-65 (Confusion, Urea >7, RR ≥30, BP <90/60, age ≥65) is a quick severity/triage aid, but the ATS/IDSA major/minor criteria decide ICU admission.

🦠 3 · Pathogens & MDR Risk

Who causes it — and the resistance flags

Setting	Typical pathogens
Severe CAP	S. pneumoniae, Legionella, S. aureus, H. influenzae, Gram-negatives, respiratory viruses (influenza, SARS-CoV-2)
HAP / VAP	Pseudomonas aeruginosa, S. aureus (incl. MRSA), Enterobacterales (incl. ESBL), Acinetobacter

MDR risk factors — the reason to broaden

IV antibiotics in the last 90 days (strongest single risk for both MRSA & Pseudomonas)
Septic shock / need for ventilation at VAP onset
≥5 days of hospitalisation before VAP; high local resistance rates
ARDS or acute renal replacement before VAP onset

🩺 4 · Diagnosis & Work-up

Confirm it, and get microbiology before antibiotics (without delaying them)

Test	Role
Imaging	New/progressive infiltrate on CXR/CT (ultrasound at bedside)
Clinical VAP signs	New infiltrate + fever/leukocytosis + purulent secretions + worsening oxygenation
Respiratory sampling	VAP: non-invasive (endotracheal aspirate) with semi-quantitative culture is adequate; BAL/PSB optional
Blood cultures + urinary antigens	In severe CAP: pneumococcal & Legionella antigens, blood cultures, viral PCR
Procalcitonin	Do not use to start antibiotics; may help guide duration

CPIS (Clinical Pulmonary Infection Score) is not recommended as the sole basis to start or stop antibiotics — combine clinical, imaging and microbiological data.

💊 5 · Empirical Antibiotics

Start early, match the setting, then de-escalate

Scenario	Empirical regimen
Severe CAP	β-lactam (ceftriaxone/cefotaxime/amoxicillin-clavulanate) + macrolide (azithromycin) — or β-lactam + respiratory fluoroquinolone. Add oseltamivir if influenza.
Severe CAP + MRSA risk	Add vancomycin or linezolid (post-influenza necrotising pneumonia, known colonisation)
Severe CAP + Pseudomonas risk	Use an anti-pseudomonal β-lactam (pip-tazobactam, cefepime, meropenem) in place of ceftriaxone
HAP/VAP — low MDR risk	One agent covering Pseudomonas & MSSA (e.g. pip-tazobactam or cefepime)
HAP/VAP — high MDR risk / shock	Two anti-pseudomonals from different classes + MRSA cover (vancomycin/linezolid)

Steroids in severe CAP

Recent evidence (e.g. hydrocortisone in severe CAP) supports adjunctive corticosteroids in severe CAP — reasonable in the sickest, especially with high inflammatory markers; not for routine mild disease.

🛡 6 · VAP Prevention Bundle

Stop it before it starts

Element	Why
Head-up 30–45°	Reduces aspiration
Daily SAT + SBT, minimise sedation	Shorter ventilation = less VAP
Subglottic-suction ETT; maintain cuff pressure	Reduces micro-aspiration past the cuff
Oral care (chlorhexidine — increasingly debated)	Reduces oropharyngeal colonisation
Avoid unnecessary re-intubation; prefer NIV/HFNO where suitable	Each intubation adds risk
VTE & stress-ulcer prophylaxis, early mobilisation	General ventilator bundle

🎯 7 · Management Principles

After the first dose

Appropriate & early beats broad-and-late: inadequate initial cover increases mortality.
De-escalate at 48–72 h on culture results and clinical response; stop MRSA/Pseudomonas cover if not grown.
Duration ~7 days for most CAP and VAP/HAP if responding (longer only for non-fermenters/complications, guided by response ± procalcitonin).
Support & source control: oxygen/ventilation, fluids/vasopressors for sepsis, drain empyema, treat the complication.
Prevent recurrence: pneumococcal & influenza vaccination.

🚫 8 · Common Mistakes

Common mistakes

❌ 1 — Delaying antibiotics for tests

Take cultures, but don't wait — early appropriate therapy saves lives in severe CAP and VAP.

❌ 2 — Broad-spectrum forever

Failure to de-escalate at 48–72 h breeds resistance and toxicity. Narrow to the organism.

❌ 3 — Missing MDR risk (or over-calling it)

Recent IV antibiotics and shock justify broadening; their absence justifies a single agent. Tailor, don't guess.

❌ 4 — Treating colonisation as VAP

A positive tracheal aspirate without new clinical/radiological change is often colonisation — don't reflexively treat.

❌ 5 — Long courses by default

Most respond to ~7 days; prolonged courses add harm without benefit.

🎓 9 · Exam Pearls — DrNB / IDCCM / IFCCM

Exam pearls

Q: Define CAP, HAP, VAP.
CAP <48 h / community; HAP ≥48 h after admission; VAP ≥48 h after intubation (a subset of HAP). HCAP is abandoned.

Q: ICU admission criteria for CAP?
ATS/IDSA: 1 major (shock needing pressors, or ventilation) or ≥3 minor criteria.

Q: Strongest MDR risk factor?
IV antibiotics within the previous 90 days (for both MRSA and Pseudomonas).

Q: Role of procalcitonin?
Not to start antibiotics; useful to help decide when to stop.

Q: Typical treatment duration?
About 7 days for most CAP and VAP/HAP that are responding.

⭐ 10 · Key Differences

All the comparisons in one place

The distinctions that steer antibiotics and answers — gathered at the end.

CAP vs HAP vs VAP

Feature	CAP	HAP	VAP
Onset	Community / <48 h	≥48 h after admission	≥48 h after intubation
Typical bugs	Pneumococcus, atypicals, viruses	GNB, S. aureus	Pseudomonas, MRSA, resistant GNB
Empirical spectrum	β-lactam + macrolide	Anti-pseudomonal ± MRSA by risk	Broadest; two-drug if high MDR risk

Severe CAP — major vs minor criteria

Major (either)	Minor (need ≥3)
Septic shock on vasopressors; mechanical ventilation	RR ≥30; P/F ≤250; multilobar infiltrates; confusion; uraemia; leukopenia; thrombocytopenia; hypothermia; hypotension needing aggressive fluids

Early-onset vs Late-onset VAP

Feature	Early (<5 days)	Late (≥5 days)
Organisms	More sensitive (pneumococcus, MSSA, sensitive GNB)	More MDR (Pseudomonas, MRSA, Acinetobacter)
Empirical breadth	Narrower possible if no MDR risk	Broader, often two-drug + MRSA cover

📚 11 · References

References

Irwin RS, Lilly CM, Mayo PH, Rippe JM (eds). Irwin & Rippe's Intensive Care Medicine. 9th ed. Wolters Kluwer; 2023.
Marino PL. Marino's The ICU Book. 5th ed. Wolters Kluwer; 2025.
Bersten AD, Handy JM (eds). Oh's Intensive Care Manual. Elsevier; 2026.
Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia (ATS/IDSA). Am J Respir Crit Care Med. 2019;200:e45–e67.
Kalil AC, Metersky ML, Klompas M, et al. Management of adults with HAP and VAP (IDSA/ATS). Clin Infect Dis. 2016;63:e61–e111.
Dequin PF, Meziani F, Quenot JP, et al. (CAPE COD). Hydrocortisone in severe community-acquired pneumonia. N Engl J Med. 2023;388:1931–1941.