Pneumonia — Written Clinical Reasoning

SAQ 1 — Severe CAP: Immediate Management, Empiric Therapy, and Corticosteroid Decision (20 marks, 30 minutes)

Prompt: Outline your immediate resuscitation and empiric antibiotic management of this patient. Include your ventilatory strategy, the specific drug regimens with doses, whether you would use adjunctive corticosteroids and why, and your plan for the right pleural effusion. Include the evidence base for each major decision. ^[1]

Model Answer

Immediate resuscitation and Sepsis Six (4 marks): ^[1]

This patient has severe CAP (CURB-65 = 5, PSI likely class V) with septic shock (hypotension, lactataemia, confusion) and type 1 respiratory failure. She meets IDSA/ATS major criteria for severe CAP (need for vasopressor support anticipated). My immediate priorities follow the Sepsis Six: ^[1]

1. High-flow oxygen via face mask targeting SpO2 94-98% (she does not have known CO2 retention, though COPD is a risk — I would check an arterial blood gas at 30-60 minutes and adjust the target to 88-92% if she is retaining CO2).
2. Take blood cultures (two sets), send lactate (already 3.2 — rising lactate confirms tissue hypoperfusion), and obtain a venous gas.
3. Administer broad-spectrum antibiotics within one hour — this is the single most time-critical intervention in septic shock.
4. Give intravenous crystalloid — 30 mL/kg of balanced crystalloid (Hartmann's or Plasma-Lyte) over the first 3 hours, then reassess fluid responsiveness.
5. Measure urine output — urinary catheter and hourly monitoring as a marker of perfusion.
6. Assess for vasopressor need — if she remains hypotensive after fluid resuscitation, start noradrenaline via a central line, titrated to MAP at least 65 mmHg. ^[1]

Empiric antibiotic therapy (5 marks): ^[1]

Given severe CAP in the ICU without current risk factors for Pseudomonas (no bronchiectasis, no recent hospitalisation, no known colonisation) or MRSA (not post-influenza, no cavitating infiltrates), I would prescribe: ^[1]

• Piperacillin-tazobactam 4.5 g IV every 8 hours (or ceftriaxone 2 g IV daily) — for pneumococcal, Haemophilus, and other typical bacterial cover, with the anti-pseudomonal breadth of pip-tazo as a prudent choice given her COPD and the severity
• PLUS azithromycin 500 mg IV daily — for atypical cover (Legionella, Mycoplasma, Chlamydia), which is mandatory in severe CAP ^[1]

The rationale for the beta-lactam plus macrolide combination is that observational data consistently show lower mortality with combination therapy than with beta-lactam monotherapy in severe CAP, attributable to the atypical cover and possibly the anti-inflammatory (immunomodulatory) effect of macrolides. The IDSA/ATS 2019 guideline mandates atypical cover in severe CAP ^[1].

I would also send pneumococcal and Legionella urinary antigens (rapid, high-yield in severe CAP), and sputum culture if obtainable. If the Legionella urinary antigen is positive, I would continue the macrolide and extend the duration to 5-10 days (azithromycin) or switch to a respiratory fluoroquinolone (moxifloxacin) for 14-21 days. ^[1]

Corticosteroid decision (4 marks): ^[1]

Yes — I would add adjunctive corticosteroids. The evidence supports their use in severe CAP: ^[1]

• The Blum et al. RCT (Lancet 2015) showed prednisone 50 mg orally daily for 7 days shortened time to clinical stability by approximately 1.5 days ^[4].
• The Siemieniuk et al. meta-analysis (Ann Intern Med 2015) showed corticosteroids reduced mortality (RR 0.67), mechanical ventilation (RR 0.45), and ARDS (RR 0.24) in severe CAP, with the benefit concentrated in the severe subgroup ^[3].

The main adverse effect is hyperglycaemia (RR 1.49), which is relevant given her type 2 diabetes — I would monitor blood glucose closely and may need an insulin sliding scale while she is on steroids. There was no increase in gastrointestinal haemorrhage or secondary infection in the meta-analysis. ^[1]

The regimen: prednisone 50 mg orally (or via nasogastric tube) daily for 7 days (or hydrocortisone 200 mg/day IV if unable to tolerate oral). I would not extend beyond 7 days unless there was a separate indication (e.g., refractory septic shock per the Surviving Sepsis guidelines, which use hydrocortisone 200 mg/day when vasopressors are ongoing). ^[1]

Parapneumonic effusion management (4 marks): ^[1]

Her right pleural effusion (25 mm on lateral decubitus) requires diagnostic thoracentesis because it is moderate in size and she has severe pneumonia — the effusion may already be complicated. I would: ^[1]

1. Perform a pleural ultrasound to characterise the effusion (size, loculation, echogenicity) and mark a safe site for aspiration.
2. Perform diagnostic thoracentesis, sending pleural fluid for pH (using a blood gas analyser), protein, LDH, glucose, cell count and differential, Gram stain, and culture.
3. Interpret using Light's criteria for exudate versus transudate, and the pH and glucose for the decision to drain:
   • pH over 7.20 and glucose over 3.3 mmol/L — uncomplicated; antibiotics alone
   • pH 7.0-7.20 or loculated — complicated parapneumonic effusion; chest drain plus antibiotics, consider intrapleural fibrinolytics (tPA/DNase) if loculated
   • pH under 7.0 or frank pus — empyema; chest drain plus fibrinolytics or surgical drainage (VATS) ^[1]

The key teaching point is that a patient with CAP who is not improving after 48-72 hours of appropriate antibiotics must be re-evaluated for a parapneumonic effusion or empyema — this is a common reason for treatment failure and must not be missed. ^[1]

Communication and follow-up (3 marks): ^[1]

• I would explain to the patient's family that she has severe pneumonia with sepsis, that she is being treated in the ICU, and that the first 48-72 hours are critical.
• Once she recovers, I would address smoking cessation (the single most effective intervention to reduce future CAP risk) with varenicline or nicotine replacement therapy.
• Arrange pneumococcal and influenza vaccination before discharge (after recovery from the acute illness, typically 2-4 weeks).
• Arrange a repeat CXR at 6 weeks to ensure radiographic resolution and exclude an underlying lesion (especially important in a 40 pack-year smoker — underlying bronchial obstruction from lung cancer can present as a non-resolving pneumonia). ^[1]