Kinetics of changes in serum concentrations of procalcitonin, interleukin-6, and C- reactive protein after elective abdominal surgery. Can it be used to detect postoperative complications?

Postoperative increase in inflammation biologic markers is associated with a nonspecific inflammatory response to a surgical injury. We investigated the kinetics of changes in serum concentrations of procalcitonin (PCT), C-reactive protein (CRP) and interleukin-6 (IL-6) after abdominal surgeries and we focused on the behaviour of those markers in the case of development of the systemic inflammatory response syndrome (SIRS). In the single centre we conducted a prospective observational study and we included patients admitted to the ICU after elective abdominal surgery. A total of 41 patients were included and 8 (19.5%) of them had clinical and laboratory signs of SIRS. Sepsis was confirmed in one of the patients, a 72-year old patient operated due to having an abdominal aortic aneurysm. Plasma concentrations of PCT, CRP and IL-6 were measured in all the patients before surgery and at the postoperative day 1 (POD1), postoperative day 2 (POD2) and postoperative day 3 (POD3). Systemic release of PCT, CRP and IL-6 was present in all the measured time points after the abdominal surgery. Median concentrations of IL-6 (100.4 pg/mL) and PCT (1, 17 pg/mL) production were measured highest at POD1 and the median of CRP (147 mg/L) was measured at highest POD2. A larger increase of all three measured markers was found in patients with SIRS compared to those without. IL-6 at POD1 and POD2 was a good predictor of SIRS (areas under curves were 0.71 and 0.765, respectively), showing the highest accuracy among investigated markers at those time points. CRP at POD3 was a good predictor of SIRS (AUC was 0.76). A cut-off of 95 mg/mL in the level of CRP at POD3 yielded a sensitivity of 87.5% and specificity of 66.7% in detecting SIRS. IL-6 and CRP were the best in detecting postoperative SIRS after abdominal surgery with the highest area under ROC curve. This study is showing that PCT is not a good marker of SIRS caused only by surgical injury without sepsis.