Postoperative fever is classified based on the timing of onset and the likely causes. Here’s a general guide according to the days after surgery:
Day 0-2 (Immediate/Acute):
Causes:
• Inflammatory response to surgical trauma or anesthesia (common and benign)
• Atelectasis (controversial, but frequently cited as a cause)
• Pre-existing infection or bacteremia (e.g., from procedures or underlying conditions)
• Medication reaction (e.g., to anesthetics or blood products)
Day 3-5 (Early):
Causes:
• Urinary tract infection (UTI) (commonly associated with indwelling catheters)
• Pneumonia (especially in patients with poor pulmonary function or inadequate mobilization)
• Surgical site infection (SSI) (early signs, but often delayed)
Day 5-7 (Intermediate):
Causes:
• Surgical site infection (more likely to present by this time with redness, swelling, or drainage)
• Deep vein thrombosis (DVT) or pulmonary embolism (PE) (especially in immobile patients)
• Catheter-related bloodstream infection (CRBSI) (central or peripheral lines)
Day 7 and beyond (Late):
Causes:
• Abscesses (e.g., intra-abdominal or pelvic abscess)
• Anastomotic leak (in gastrointestinal surgeries)
• Persistent or chronic infections (related to prosthetic materials, such as implants or grafts)