What are the causes of postoperative fever?

From the Guidelines

Postoperative fever is usually non-infectious in origin during the initial 48 hours after surgery, but after 96 hours, it is likely to represent infection.

Common Causes of Postoperative Fever

• Atelectasis: often considered a cause of postoperative fever, although this should be a diagnosis of exclusion 1
• Urinary tract infection: common postoperatively due to the use of urinary drainage catheters, with the duration of catheterization being the most important risk factor 1
• Surgical site infections (SSIs): can be superficial incisional, deep incisional, or organ/space, with SSIs being a common cause of postoperative fever, especially after 48 hours 1
• Hematoma or infection of the surgical field: can cause postoperative fever, with wound infection being rare in the first few days after operation, except for group A streptococcal infections and clostridial infections 1
• Aspiration: can occur during the perioperative period and cause postoperative fever 1
• Community-acquired infections: such as influenza A or Legionella pneumonia, can also cause postoperative fever 1

Diagnosis and Management

• Physical examination: is crucial in diagnosing SSIs, with local signs of pain, swelling, erythema, and purulent drainage being usually present 1
• Laboratory tests: such as urinalysis or culture, may be necessary to evaluate fever, especially if there is reason to suspect an infection at a specific site 1
• Imaging studies: such as chest radiograph, may be necessary to evaluate postoperative fever, especially if respiratory symptoms are present 1
• Antibiotic therapy: may be necessary to treat SSIs, especially if systemic inflammatory response criteria or signs of organ failure are present 1
• Surgical intervention: may be necessary to drain and debride infected wounds, especially if fascial disruption is suspected 1

From the Research

Causes of Postoperative Fever

The causes of postoperative fever can be categorized into infectious and non-infectious etiologies.

• Non-infectious causes include:
  • Inflammation caused by surgical trauma 2
  • Blood contact with cardiopulmonary bypass circuit resulting in the release of cytokines 2
  • Aseptic meningitis 3
  • Transient elevation in temperature (TET) 3
• Infectious causes include:
  • Urinary tract infections 3, 4, 5
  • Wound infections 3, 4, 5
  • Pneumonia 3, 4, 5
  • COVID-19 3
  • Mediastinitis 6
  • Postpericardiotomy syndrome 6
  • Prosthetic valve endocarditis 6
  • Aortic vascular graft infections 6
  • Ventricular assist device infections 6

Risk Factors for Postoperative Fever

Certain factors can increase the risk of developing postoperative fever, including:

• Cranial surgery 3
• Prolonged duration of surgery 3
• Use of urinary catheters 3
• Use of wound drains retained beyond postoperative day 3 3

Evaluation of Postoperative Fever

A focused approach is recommended when evaluating postoperative fever, taking into account the patient's history, physical examination, and laboratory results 4. The "four Ws" mnemonic can be helpful in identifying potential causes: wind (pulmonary causes), water (urinary tract infection), wound (surgical site infection), and "what did we do?" (iatrogenic causes) 4.