Hospital Medicine

Post-operative fever

Post-Operative Fever

I. Problem/Condition.

A temperature of greater than 38.0° C (100.4° F) following a surgical procedure defines a post-operative fever. However, if a patient does not meet this threshold and otherwise appears ill, further investigation may still be warranted. Post-operative fevers are a common phenomenon, occurring in up to 40% of patients following certain surgical procedures. The pathophysiology of a postoperative fever is either a reflection of the cytokines released following the tissue trauma from the procedure itself, an underlying infection, or other non-infectious causes.

II. Diagnostic Approach.

A. What is the differential diagnosis for this problem?

The differential diagnosis of post-operative fevers can be divided into infectious versus non-infectious. Non-infectious causes can be further divided into surgical site inflammation, thrombus formation (e.g., DVT and PE), inflammatory states (e.g., gout and pancreatitis), medications, and transfusion reactions.

The likelihood of any etiology is dependent on the timing of the fever in relation to the surgery. Immediate postoperative fevers occur within hours of the procedure and are usually caused by medications, peri-operative transfusions, or preoperative infection. Acute and subacute post-operative fevers develop within the first week to 2-4 weeks respectively and are typically related to infections (e.g., surgical site, UTI, pneumonia, line infection), thrombus, or other inflammatory states (e.g., gout, pancreatitis). Delayed post-operative fevers occur more than a month following the procedure and are caused by indolent surgical site infections or viral infections acquired via perioperative transfusions.

B. Describe a diagnostic approach/method to the patient with this problem.

After documentation of a post-operative fever, all patients should be assessed for evidence of localizing infection. The surgical site should be inspected as well as any remaining indwelling lines or catheters. The medical record should be reviewed for any peri-operative medications or transfusions given. It may be necessary to revisit a patient's social history if there is concern about withdrawal from alcohol or other illicit drugs.

1. Historical information important in the diagnosis of this problem.

Patients should be asked about symptoms that might point to a cause for their fever. Questions like the presence of productive cough, dysuria, diarrhea, abdominal pain, or painful IV site can help uncover an infection. It is also important to ask questions that would point to thrombus formation such as painful calf, shortness of breath, and/or chest pain. Also, remember to ask questions about gout as the stress of surgery can cause a flare.

2. Physical Examination maneuvers that are likely to be useful in diagnosing the cause of this problem.

Patients with a postoperative fever should receive a focused physical exam honing in on areas of concern gathered in the history. Other useful physical examination includes inspection of all lines and noting the presence of an indwelling urinary catheter. The surgical site also should needs to be inspected for signs of inflammation or infection.

3. Laboratory, radiographic and other tests that are likely to be useful in diagnosing the cause of this problem.

In many cases, laboratory and ancillary studies do not need to be ordered. A stable patient without localizing symptoms or concerning physical exam likely does not need any studies ordered, especially if they are less than 48-92 hours out from surgery. During this time period the majority of post-operative fevers are non-infectious and resolve without the need for any intervention. Reflexive orders for a CBC, urinalysis, chest x-ray, and blood cultures should not be the norm.

Information gathered in the focused history and physical should help guide the ordering of any laboratory testing. Tests that may be useful in the right clinical setting include cell blood count (CBC), chest x-ray, urinalysis, lower extremity Doppler, computed tomography (CT), and/or blood cultures. Procalcitonin levels might be helpful in determining if a bacterial infection is the cause of the fever. This laboratory test has been best studied in lower respiratory tract infections and sepsis. While it may provide useful information, but levels can also be affected by surgery. Therefore, routine collection of procalcitonin is not recommended in the post-operative setting.

C. Criteria for Diagnosing Each Diagnosis in the Method Above.

There is no special criterion used to determine the etiology of a postoperative fever. Normal disease-specific criteria should be utilized.

D. Over-utilized or “wasted” diagnostic tests associated with the evaluation of this problem.

In many settings, ordering any diagnostic testing would be wasteful. Again, testing should be based on the history and physical examination gathered at the time of the postoperative fever.

III. Management while the Diagnostic Process is Proceeding.

A. Management of Clinical Problem Postoperative Fever.

As mentioned before, most postoperative fevers are benign, but there are several life-threatening etiologies that should not be missed. Surgical site infections that occur within hours of the procedure should raise concern over group A Streptococcus or Clostridium perfringens infections. Both of these need immediate attention and require surgical and antibiotic therapy. Concerns of thrombus formation should prompt evaluation with lower extremity Dopplers or CT of the chest.

Anticoagulation management of DVT or PE may need to be tailored based on the risk of surgical site bleeding. The deployment of an IVC filter should be considered if the risk of bleeding is too high. Line-associated bacteremia or sepsis is also a diagnosis that should not be missed. In situations where there is concern about the above etiologies, the health care provider should take immediate action, which may include empiric treatment of infections. Stable patients however should have definitive testing confirming infection come back prior to starting treatment.

B. Common Pitfalls and Side-Effects of Management.

One common pitfall to managing postoperative fever is ordering diagnostic testing in a "shotgun" approach. All testing should be ordered based on information gathered after chart review and a focused history and physical. A second pitfall would be the use of empiric antibiotics for presumed infections. In a stable patient, it is okay to confirm the diagnosis prior to starting therapy. Within the first 48-92 hours, most fevers are benign and starting empiric antibiotics only contributes to antibiotic resistance.

VII. What's the evidence?

Garibaldi, RA, Brodine, S, Matsumiya, S, Coleman, M. "Evidence for the non-infectious etiology of early postoperative fever". Infect Control. vol. 6. 1985. pp. 273.

Wallace, WC, Cinat, ME, Nastanski, F, Gornick, WB, Wilson, SE. "New epidemiology for postoperative nosocomial infections". Am Surg. vol. 66. 2000. pp. 874.

Schwandt, A, Andrews, SJ, Fanning, J. "Prospective analysis of a fever evaluation algorithm after major gynecologic surgery". Am J Obstet Gynecol. vol. 184. 2001. pp. 1066.

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