It’s Gettin’ Hot in Here, So....What Should I Do about This Post-Operative Fever?

Fever is one of the most common post-operative issues encountered: in the Trauma ICU, in the Obs unit, on the floor, and in the front room with patients returning. So what should a resident do when encountering a post-operative fever?

Fever Defined

At our institution, we most often use the threshold of 101.5 degrees Fahrenheit (38.6 degrees Celsius) to define a fever. The literature varies according to definition, with lower thresholds (i.e. 100.4 degrees Fahrenheit (38 degrees Celsius)) more sensitive to find infectious causes but less specific. Keep in mind that antipyretics such as acetaminophen and NSAIDs may mask fevers.

Pathophysiology

Fever is caused by cytokine release, most often IL-1, IL-6, TNF-alpha, and IFN-gamma, with IL-6 most often implicated as the cause of post-operative fever (1). Tissue trauma from surgery can cause fever itself; in general, the greater the tissue trauma, the more likely the patient is to experience fever (2). Fever due to tissue trauma usually resolves within two days; this is important for how we respond to a patient who is febrile.

Differential Diagnosis

A broad array of conditions can cause post-operative fever, often with varying time courses. It is easiest to separate out these causes into infectious causes and non-infectious causes.

Common Infectious Causes of Post-Operative Fevers

Surgical Site Infection (SSI): These most often occur after POD5 in the form of a superficial SSI – a wound infection – or a deep SSI – like an intra-abdominal abscess after a GI tract procedure. However, keep in mind that group A Streptococcus and Clostridium perfringens are implicated in immediate SSI that behave like necrotizing soft-tissue infections (NSTI). This entity is why all patients with a post-operative fever should have physical examination of the wound, as NSTI is best diagnosed by high-clinical suspicion.

Pneumonia: Patients in the ICU who are being mechanically ventilated are at highest risk for pneumonias. A longer duration of ventilator dependence portends a greater risk for ventilator-associated pneumonias (3). These VAPs can be prevented with prophylactic measures, including keeping the head of the bed elevated greater than 30 degrees and good oral hygiene.

Urinary Tract Infection: This is amongst the most common causes of post-operative infection. Catheters should be removed as early as possible as the longer they are indwelling, the higher the risk of UTI. UTIs most commonly cause fever after POD3.

Intravascular Catheter-Associated Infection: Indwelling vascular catheters are another cause of post-operative fever, especially if the catheters are placed under non-sterile conditions (we often place a cordis under non-sterile condition for emergent access for resuscitation). Any unnecessary vascular catheter should be discontinued.

Antibiotic-Associated Diarrhea: Any patient who receives antibiotics is at list for antibiotic-associated diarrhea, most often caused by Clostridium difficile. As most patients received antibiotics prior to incision to prevent SSI, most of our patients will be at risk for this.

Other causes that are common but will not be discussed here: Sinusitis, Acalculous cholecystitis, Foreign-body infection, Endocarditis

Common Non- Infectious Causes of Post-Operative Fevers

Deep Vein Thrombosis: These occur most common in our patients with limited post-operative mobility. It is important to remember DVT prophylaxis: sequential compression devices, chemoprophylaxis, and early mobilization.

Medications: If onset within during or the first few hours after surgery, anesthetic agents can cause fever. The most notorious disease process in this category is malignant hyperthermia, often caused my volatile anesthetics and treated with Dantrolene. Later in the hospital course, the most common offending drugs for drug fever are antibiotics and heparin.

Other causes that are common but will not be discussed here: Transfusion reaction, Drug and alcohol withdrawal, Pancreatitis, Hematoma, Suture reaction:

Mnemonics

The most common mnemonic used to remember the causes of post-operative fever is ‘The 5 W’s’: wind – pneumonia; water – UTI, wound – wound infections, walking – DVTs; wonderdrug – drug fever.

Is it Atelectasis?

Traditional surgical dogma teaches that atelectasis causes post-operative fever, especially in the first 24-48 hours. The sensitivity of fever in predicting atelectasis is less than 50% (4). Further, there is no association between the presence of fever and the degree of atelectasis (5). This association is likely correlative and not causal.

What Should I Do?

Whenever a patient has a fever, the physician should examine the patient. In the first 48 hours after surgery, the wound can be examined to rule out an early post-operative wound infection with Clostridium or Group A Streptococcus. If there are no signs of this type of infection, the patient can be monitored safely and the fever can likely be attributed to tissue trauma. All indwelling catheters should be evaluated for their necessity and discontinued if possible to prevent potential infection.

After 48 hours, the cause of fever is more likely to be infectious. We most often ask for a “pan-culture” of these patients, which includes a chest X-ray, urinanalysis (and reflexive culture) and blood cultures, as well as potential culture of other available pertinent fluids (i.e. CSF in a patient with an indwelling drain). However, the yield and utility of this practice has been questioned (6).

Empiric antibiotics are rarely started unless there are signs of hemodynamic compromise. Cultures should only be drawn once every 24 hours in patients who are persistently febrile.

Conclusion

Post-operative fever is common in our patients. Maintaining a broad differential, both infectious and non-infectious, is essential. Timing can yield clues as to the etiology of the fever. Physical examination remains a necessity in these cases, with adjunct laboratory tests being potentially useful as well.

References

1.       Mitchell, JD, Grocott, HP, Phillips-Bute, B, et al. Cytokine secretion after cardiac surgery and its relationship to postoperative fever. Cytokine. 2007; 39:37.

2.       Dauleh MI, Rahman S, Townell NH. Open versus laparoscopic cholecystectomy: a comparison of postoperative temperature. J R Coll Surg Edinb. 1995;40(2):116.

3.       Horan TC, Culver DH, Gaynes RP, Jarvis WR, Edwards JR, Reid CR. Nosocomial infections in surgical patients in the United States, January 1986-June 1992. National Nosocomial Infections Surveillance (NNIS) System. Infect Control Hosp Epidemiol. 1993;14(2):73.

4.       Roberts J, Barnes W, Pennock M, Browne G. Diagnostic accuracy of fever as a measure of postoperative pulmonary complications. Heart Lung. 1988;17(2):166.

5.       Engoren M. Lack of association between atelectasis and fever. Chest. 1995;107(1):81.

6.       Freischlag J, Busuttil RW. The value of postoperative fever evaluation. Surgery. 1983 Aug;94(2):358-63.

from Baddr Shakhsheer, MD