Austin, Texas – October 24, 2007 – According to the textbooks, C-reactive protein (CRP) will return to normal 5 to 7 days after surgery. If CRP level remains high after this point, the surgeon can assume that a surgical site infection is to blame. New research being presented here at the North American Spine Society’s 22nd Annual Meeting indicates that CRP and other inflammatory markers remain high for up to two weeks after instrumented spinal surgery.
“A higher value of conventional inflammatory markers such as white blood cell count, CRP, and body temperature does not always indicate the coincidence of surgical site infection,” said Masao Deguchi, MD, Nagano Red Cross Hospital, Japan. The normal upper limit for these inflammatory markers is much higher after spinal instrumentation than previously thought.
“In other words, it is next to impossible to detect surgical site infection in the acute stage when these inflammatory markers … are within the values shown in this paper.”
Deguchi’s study showed that a normal CRP reading is 22.2 mg/dL at day 3 postoperatively, 5.6 mg/dL at day 7 and 3/6 mg/dL at day 14. A white blood cell count reading of 12,700 at day 3, 9,200 at day 7 and 9,900 at day 14 are all normal. Normal body temperatures are as follows: 38.4° C at day 3, 37.6° C at day 7 and 37.7° C at day 14.
Deguchi included all patients who underwent spinal decompression and/or fusion from 1997 to 2006. He excluded any patients with confirmed infections.
He examined two groups of patients: a control group who underwent uninstrumented spinal decompression surgery (n=589) and a group that underwent spinal decompression and fusion with instrumentation (n=468). Deguchi recorded CRP, white blood cell count one day before surgery and on postoperative days 3, 7 and 14. He recorded body temperature one day before surgery until postoperative day 14. In addition, he performed a physical exam and wound observation to check for surgical site infection.
Three patients who received instrumented surgery developed a surgical site infection.
Deguchi defined the upper limit for each parameter as the mean and 2 times of standard deviation. He diagnosed surgical site infections according to the Centers for Disease Control and Prevention guidelines.
“When surgical site infection is confirmed two to three weeks after instrumented surgery, [patients may criticize] the surgeon that the diagnosis of postoperative infection was late,” Deguchi said. “Patients may complain that the surgeon overlooked the signs of surgical site infection. This kind of argument may be caused by a misunderstanding of the postoperative normal changes in CRP.”
To avoid this, informing the patient before surgery is critical. “Patients should be told before surgery that inflammatory markers will usually remain higher than expected, and that they should not be overly concerned. When inflammatory marker such as CRP rises above the reference value, it is very possible that the patient is developing surgical site infection.”
The role that instrumentation plays in increasing these inflammatory markers remains unclear. “Instrumented surgery is much more invasive than decompression surgery without instrumentation. Excessive dissection of muscles to make room for the instrumentation may promote the increase of inflammatory markers.”
Source: Abstract # 9. Masao Deguchi, I, MD. “Determination of the Normal Upper Limit of Early-phase Enhanced Inflammatory Reaction Following Spinal Instrumentation Surgery.”
FDA Device/Drug Status: This abstract does not discuss or include any applicable devices or drugs.
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