What is the most common cause of fever in a post-operative (postoperative) patient?

From the Guidelines

Fever in the initial 48 hours after surgery is usually non-infectious in origin, with atelectasis being a common cause. According to the guidelines for evaluation of new fever in critically ill adult patients, updated in 2008 by the American College of Critical Care Medicine and the Infectious Diseases Society of America 1, atelectasis is often considered a cause of postoperative fever, although this should be a diagnosis of exclusion.

Key Considerations

• Atelectasis typically occurs within the first 48 hours after surgery due to shallow breathing, pain, anesthesia effects, or immobility, leading to mucus plugging and airway closure.
• Beyond atelectasis, other important causes of post-operative fever follow a timeline:
  • Wound infections typically appear 3-5 days post-surgery
  • Urinary tract infections around days 3-5, often related to the use of urinary drainage catheters 1
  • Deep vein thrombosis and pulmonary embolism can also occur, typically around days 4-7 and 4-10, respectively
• Management of post-operative fever should include a thorough assessment based on timing, including physical examination, laboratory tests, and imaging as appropriate.

Prevention and Management

• Early mobilization, incentive spirometry, adequate pain control, and deep breathing exercises can help prevent atelectasis.
• Antibiotics should only be initiated if there is clear evidence of infection, not for fever alone, to avoid unnecessary antibiotic use and potential resistance.
• A chest radiograph is not mandatory for evaluation of postoperative fever unless respiratory rate, auscultation, abnormal blood gas, or pulmonary secretions suggest a high probability of utility 1.
• Urinalysis or culture is not mandatory to evaluate fever during the initial 2 to 3 days postoperatively unless there is reason by history or examination to suspect an infection at this site 1.

From the Research

Causes of Fever in Post-Op Patients

• Fever is common in surgical patients, with only about 40% of fever episodes caused by infection 2
• Non-infective etiologies are a significant cause of fever in post-op patients, but the exact cause can be difficult to determine

Infectious Causes of Fever

• Surgical site infections (SSIs) are a common cause of fever in post-op patients, and can be classified into different grades depending on the severity of the infection 3, 4
• Risk factors for SSIs include anemia, immunosuppression, diabetes mellitus, obesity, smoking, and malnutrition 3
• Other infectious causes of fever in post-op patients can include acute cholecystitis, antibiotic-related pseudomembranous colitis, systemic candidiasis, and transfusion-related cytomegalovirus disease 2

Prevention and Treatment of Infectious Causes

• Preventive measures such as antisepsis of the surgical area, antibiotic prophylaxis, and intraoperative subcutaneous wound irrigation with an antiseptic solution can reduce the risk of SSIs 3, 5
• Treatment of SSIs typically involves aggressive surgical debridement and effective antimicrobial therapy 4
• Early recognition and treatment of infections is crucial to reduce morbidity and mortality in post-op patients 2, 6