Postoperative fever

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)