What is considered a postoperative fever?

Postoperative Fever Definition

Postoperative fever is defined as a temperature ≥38.0°C (100.4°F), with fever occurring after 48 hours postoperatively having a higher probability of representing an infection, while fever in the first 48 hours is generally of non-infectious origin. 1

Timing of Postoperative Fever

Postoperative fever follows a predictable pattern based on timing:

• First 48 hours (up to 4 days):

  • Rarely represents infection
  • Usually related to the normal inflammatory response to surgical trauma
  • Caused by cytokine release from tissue damage
  • Extensive evaluations during this period have little to no benefit 1, 2

• After 48 hours:

  • Higher probability of representing an infection
  • Requires more thorough evaluation
  • More likely to need intervention 3, 1

Evaluation Based on Temperature and Clinical Status

The Infectious Diseases Society of America guidelines provide a clear algorithm for evaluating postoperative fever 3:

• Temperature <38.5°C without tachycardia:

  • Observation and dressing changes are recommended
  • No antibiotics typically needed

• Temperature ≥38.5°C or heart rate ≥110 beats/min:

  • Antibiotics and opening of the suture line are required
  • More aggressive evaluation is warranted

Diagnostic Approach

The approach to postoperative fever should be systematic:

1. Timing-based assessment: Consider when the fever occurred relative to surgery
2. Daily inspection of the surgical wound: Look for signs of infection
3. Selective testing: Only if specific indicators are present
   • Avoid overzealous testing in the first 48-72 hours as it wastes resources with minimal yield 1
   • Blood cultures have extremely low yield in elective surgery patients with early postoperative fever 2

Common Pitfalls

• Attributing fever to atelectasis: This should be a diagnosis of exclusion only 1
• Excessive testing: Early postoperative fever is common (occurring in approximately 24% of patients) and rarely caused by infection 2
• Missing non-infectious causes: In clean surgeries, non-infectious fever is more frequent than infectious fever 4
• Assuming all late fevers are infectious: Even fevers up to the seventh postoperative day may not distinguish infection from general inflammation in clean orthopedic surgery 5

Evidence Quality

The most recent and comprehensive guidelines from the American College of Critical Care Medicine and the Society of Critical Care Medicine (summarized in Praxis Medical Insights) provide the strongest recommendations regarding the definition and evaluation of postoperative fever 1. These align with the Infectious Diseases Society of America guidelines, which provide specific temperature thresholds for clinical decision-making 3.

Research studies consistently show that early postoperative fever is common and rarely indicative of infection, with bedside evaluation having the highest yield for determining fever etiology 2, 5, 6.