Sustained Fevers After Spinal Fusion: A Sentinel for Infection?

Postoperative fevers occur frequently. During the first 2 to 3 days after surgery, these fevers are often due to atelectasis or the increased inflammatory response that arises from tissue injury during surgery. However, persistent postoperative fevers should be cause for concern. In the August 19, 2020 issue of The Journal, Hwang et al. examine the relationship between sustained fevers after spine instrumentation and postoperative surgical site infection.

The authors retrospectively reviewed 598 consecutive patients who underwent lumbar or thoracic spinal instrumentation. They excluded patients who underwent surgery to treat tumors or infections and those with other identified causes of fever, such as a urinary tract infection or pneumonia. Sustained fevers were defined as those that began on or after postoperative day (POD) 4 and those that started on POD 1 to 3 if they persisted until or beyond POD 5.

Sixty-eight patients (11.4%) met the criteria for a sustained fever after spinal instrumentation. Nine of those 68 (13.2%) were diagnosed with a surgical site infection. Of the 530 patients who did not have a sustained fever, only 5 (0.9%) developed a surgical site infection (p<0.001 for the between-group difference).

Further analysis revealed 3 diagnostic clues for surgical site infections among the patients with sustained fevers:

  • Continuous fever (rather than cyclic or intermittent)
  • Levels of C-reactive protein (CRP) >4 mg/dL after POD 7
  • Increasing or stationary patterns of CRP level and neutrophil differential

In addition, the authors found that CRP levels >4 mg/dL between PODs 7 and 10 had much greater sensitivity for discriminating surgical site infection than gadolinium-enhanced magnetic resonance imaging data obtained within 1 month of the surgical procedure.

Although a vast majority (87%) of patients with sustained postoperative fevers in this study did not develop an infection, persistent fever after spine instrumentation surgery is something to be mindful of. The authors describe their findings as “tentative” and advise readers to interpret them with caution. Those caveats notwithstanding, I consider this information to be valuable because it might help prevent delays in the diagnosis of a potentially serious perioperative complication.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

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