Postoperative Fever: Causes and Management

Definition

PART 1: Causes of Postoperative Fever [4 marks]

The "Five Ws" Mnemonic (Classic Surgical Teaching)

Comprehensive Classification by Timing and Etiology

A. Immediate (< 24 hours)

• Atelectasis - most common cause of early postoperative fever; alveolar collapse due to reduced functional residual capacity (FRC), accumulated secretions, pain-related hypoventilation
• Transfusion reaction (febrile non-hemolytic or hemolytic)
• Pre-existing infection present before surgery
• Malignant hyperthermia - rare but life-threatening; triggered by volatile anaesthetics or succinylcholine
• Systemic inflammatory response syndrome (SIRS) - proinflammatory mediator cascade from the surgical insult itself

B. Early (24-72 hours)

• Pneumonia - typically days 2-4; polymicrobial in hospital-acquired cases; predisposed by prolonged ventilation and aspiration
• Urinary tract infection - from bladder catheterization; common organisms: E. coli, Klebsiella, Pseudomonas, Staphylococcus
• Intravenous catheter-related bloodstream infection (CRBSI) - most common cause of nosocomial bacteremia; organisms include Staphylococci (including coagulase-negative), enterococci, gram-negative bacilli, Candida
• Drug fever - any drug can cause it; suspect when no other source found

C. Late (> 72 hours / Days 5-10)

• Surgical site infection (SSI) - wound infection (superficial or deep)
• Intra-abdominal / pelvic abscess - especially after GI surgery
• Deep vein thrombosis and pulmonary embolism - dyspnoea is often the main symptom
• Pseudomembranous colitis (Clostridioides difficile) - after antibiotic use
• Anastomotic leak - following bowel surgery; presents with peritonitis
• Parotitis (suppurative) - in dehydrated, elderly, or immunocompromised patients

D. Noninfectious Causes (Any Time)

• Pulmonary embolism (also Day 5+)
• Pancreatitis (post-ERCP or post-abdominal surgery)
• Acalculous cholecystitis (ICU patients)
• Myocardial infarction (especially in elderly)
• Adrenal insufficiency
• Dehydration / haematoma resorption
• Withdrawal syndromes (alcohol, opioids)
• Thyroid storm / pheochromocytoma (rare)

PART 2: Management of Postoperative Fever [6 marks]

Step 1: Initial Assessment

• Precise timing of fever onset (guides likely aetiology)
• Nature of surgery performed; any intraoperative events
• Duration of urinary catheter, IV lines, ventilation
• Recent blood transfusions, new medications
• Symptoms: cough, dysuria, wound pain, diarrhoea, dyspnoea, leg swelling

• Vital signs (tachycardia, hypotension = suggest sepsis)
• Chest auscultation (absent/reduced breath sounds = atelectasis; crackles = pneumonia)
• Wound inspection (erythema, discharge, dehiscence)
• IV line insertion sites (redness, swelling, purulence)
• Calf tenderness / leg swelling (DVT)
• Abdominal examination (peritonism, ileus)

Step 2: Investigations

In early fever (< 48 h), overzealous investigation should be avoided as most early fevers are non-infectious SIRS responses. Clinical judgment should guide the extent of workup. (Berek & Novak's Gynecology)

Step 3: Specific Management by Cause

Atelectasis

• First-line: Pulmonary toilet - incentive spirometry, deep breathing exercises (5 sequential breaths held for 5-6 seconds), coughing, early ambulation, chest physiotherapy
• Adequate analgesia (to enable deep breathing)
• Bronchodilator therapy, hydration
• Supplemental oxygen
• Nebulized mucolytics if secretion-heavy
• Admission indicated for hypoxemia, underlying pulmonary disease, or debilitated patients
• (Sabiston Textbook of Surgery)

Pneumonia

• Sputum and blood cultures before starting antibiotics
• Parenteral broad-spectrum antibiotics covering gram-negative organisms and Staphylococcus; follow local hospital-acquired pneumonia guidelines
• Respiratory support as needed (supplemental O2, NIV, ventilation)
• (Tintinalli's Emergency Medicine)

UTI

• Most can be managed with oral antibiotics as outpatients
• Ciprofloxacin 500 mg twice daily or levofloxacin 750 mg once daily (guided by local antibiogram)
• Admission with parenteral antibiotics (levofloxacin 750 mg IV) for elderly, debilitated patients, or sepsis
• Remove indwelling catheter as early as possible
• (Tintinalli's Emergency Medicine)

Catheter-Related Bloodstream Infection (CRBSI)

• Remove the central venous catheter immediately
• Blood cultures from peripheral vein AND catheter tip (if short-term)
• Empirical broad-spectrum antibiotics covering Staphylococci and gram-negatives (e.g., vancomycin + piperacillin-tazobactam)
• Duration guided by organism and severity; longer course if endocarditis suspected
• (Sabiston Textbook of Surgery)

Surgical Site Infection

• Open the wound, drain pus, pack with dressing (wet-to-dry)
• Send wound swab for culture and sensitivity
• Antibiotics only if there is surrounding cellulitis, systemic sepsis, or immunocompromise (cellulitis does not require antibiotics if wound is opened and drained)
• Wound care with regular dressings; consider VAC therapy for large wounds

DVT / Pulmonary Embolism

• DVT: therapeutic anticoagulation (LMWH or direct oral anticoagulants)
• PE: full anticoagulation; thrombolysis or surgical embolectomy for massive PE with haemodynamic compromise
• Prevention: early ambulation, TED stockings, LMWH prophylaxis perioperatively

Intra-abdominal Abscess

• CT-guided percutaneous drainage (preferred)
• Broad-spectrum antibiotics (covering gram-negatives and anaerobes)
• Surgical drainage if percutaneous approach not feasible
• Early diagnosis by CT imaging

Drug Fever

• Identify and discontinue the offending drug
• Antipyretics (paracetamol)
• Typically resolves within 48-72 hours of stopping the drug

Pseudomembranous Colitis (C. difficile)

• Stop offending antibiotics if possible
• Oral vancomycin 125 mg QID for 10 days (preferred over metronidazole for non-mild disease)
• Fidaxomicin as alternative
• Isolation precautions; contact precautions

Step 4: General Supportive Measures

• Antipyretics: Paracetamol (acetaminophen) 1 g every 6 hours; NSAIDs if no contraindication
• Adequate hydration (fever increases insensible losses)
• Nutritional support (fever increases metabolic rate; early enteral nutrition preferred)
• Remove foreign bodies as soon as clinically possible - urinary catheters, IV lines, drains
• Contact the operating surgeon for all significant postoperative complications - continuity of care is essential

Key Points Summary