Circulating C-reactive protein (CRP) concentrations increase after surgery as a result of the inflammatory response to surgical trauma. However, CRP values also increase with sepsis, so it can be difficult to differentiate between inflammation and infection when trying to interpret CRP changes after surgery.
Dr. Jean-Louis Vincent, Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium, and colleagues measured daily CRP concentrations after major elective and emergency surgery in infected and noninfected patients. Their results are discussed in the article titled “C- Reactive Protein Kinetics After Major Surgery,” which is published in this month’s edition of Anesthesia and Analgesia. The investigators concluded that CRP levels increase in the first week after major surgery, but to a much greater extent in infected patients. Persistently high CRP values after postoperative day 4, specifically >100mg/L, suggested the presence of a postoperative infection.
Over a 4-month period between May 2011 and August 2011, 151 patients were studied. The majority of cases were neurosurgical (n=65) and cardiac (n=49). Only 25 patients had abdominal surgery, a group whose CRP measurements are frequently taken to try to determine the presence of infection. CRP responses in noninfected patients were dependent on the surgical procedure with abdominal surgery patients having higher CRP levels than patients undergoing cardiac surgery, and both groups’ CRP levels measuring higher than neurosurgery patients. Only 4 cardiac surgical patients developed an infection; unsurprisingly there was no difference in CRP values between infected and noninfected patients in this group. In contrast, significant increases in CRP levels were shown in the infected patients compared to the noninfected patients after neurosurgery and abdominal surgery.
Interpretation of these results would be helped if more surgical details were provided. Clearly all patients had major surgery since they were admitted to the intensive care unit, but within a group such as abdominal surgery, the size of the inflammatory response is dependent on the surgical approach, namely laparotomy versus laparoscopy. Nevertheless, this is an interesting study that addresses a difficult clinical problem. The key message is that daily CRP measurements are essential when trying to distinguish between infection and inflammation after major surgery.