OBJECTIVES:To examine the hypothesis that nitrite/nitrate, neopterin, and procalcitonin (PCT) levels can be useful predictors of sepsis-associated mortality and predictors of the postoperative complications after cardiopulmonary bypass (CPB). DESIGN:Prospective clinical study. SETTING:Intensive care unit of the Medical University Hospital. PATIENTS:41 patients with sepsis, 42 patients subjected to open heart surgery with CPB, and 30 healthy volunteers. MEASUREMENTS AND RESULTS:Nitrite/nitrate, neopterin, and PCT levels were measured in septic patients as soon as sepsis was recognized and then on the 2nd, 3rd, and 5th days of treatment. Statistically significant differences between survivors and nonsurvivors were found for neopterin and PCT. The area under receiver operating characteristic curve (AUC) for both parameters as predictors of mortality was above 0.8. The nitrite/nitrate level was also higher in nonsurvivors, but the AUC remained below 0.8, which indicates poor predictive power. The same parameters were measured in patients undergoing cardiac surgery before, during and after CPB establishment. The development of post-operative complications was correlated with increased postoperative neopterin and PCT levels. Additionally, neopterin was found as an early marker for the prognosis of postoperative complications, since patients who developed organ dysfunction had had elevated concentration of this parameter even before surgery (AUC 0.83). Measurement of NO metabolite levels was less specific and less sensitive. CONCLUSIONS:Our results confirm the value of PCT and neopterin measurement as diagnostic tools in monitoring the clinical course of patients in intensive care units.