Usefulness of procalcitonin for diagnosis of infection in cardiac surgicalpatients

Objective: To determine the value of procalcitonin (PCT) as a marker of pos toperative infection after cardiac surgery. Design: A prospective single institution three phase study. Setting: Univer sity cardiac surgical intensive care unit(31 beds). Patients. Phase I: To determine the normal perioperative kinetics of PCT, 2 0 consecutive patients undergoing elective cardiac surgery with cardiopulmo nary bypass were included. Phase 2:To determine whether PCT may be useful f or diagnosis of postoperative infection, 97 consecutive patients with suspe cted infection were included. Phase 3: To determine the ability of PCT to d ifferentiate patients with septic shock from those with cardiogenic shock, 26 patients with postoperative circulatory failure were compared. Measurements and Main Results: Phase 1: Serum samples were drawn for PCT de termination after induction of anesthesia (baseline), at the end of surgery , and daily until postoperative day (POD) 8. Baseline serum PCT concentrati on was 0.17 +/- 0.08 ng/mL (mean +/- SD). Serum PCT increased after cardiac surgery with a peak on POD 1 (1.08 +/- 1.36). Serum PCT returned to normal range on POD 3 and remained stable thereafter. Phase 2: in patients with s uspected infection, serum PCT was measured at the same time of G-reactive p rotein (GRP) and bacteriologic samples. Among the 97 included patients, 54 were infected with pneumonia (n = 17), bacteremia (n = 16), mediastinitis ( n = 9), or septic shock (n = 12). In the 43 remaining patients, infection w as excluded by microbiological examinations. In noninfected patients, serum PCT concentration was 0.41 +/- 0.36 ng/mL (range, 0.08-1.67 ng/mL). Serum PCT concentration was markedly higher in patients with septic shock (96.98 +/- 119.61 ng/mL). Moderate increase in serum PCT concentration occurred du ring pneumonia (4.85 +/- 3.31 ng/mL) and bacteremia (3.57 +/- 2.98 ng/mL). Serum PCT concentration remained low during mediastinitis (0.80 +/- 0.58 ng /mL). Five patients with mediastinitis, two patients with bacteremia, and o ne patient with pneumonia had serum PCT concentrations of <1 ng/mL. These e ight patients were administered antibiotics previously and serum PCT was me asured during a therapeutic antibiotic window. For prediction of infection by PCT, the best cutoff value was 1 ng/mL, with sensitivity 85%, specificit y 95%, positive predictive value 96%, and negative predictive value 84%. Se rum GRP was high in all patients without intergroup difference. For predict ion of infection by CRP, a value of 50 mg/L was sensitive (84%) but poorly specific (40%). Comparing the area under the receiver operating characteris tic curves, PCT was better than GRP for diagnosis of postoperative sepsis ( 0.82 for PCT vs. 0.68 for CRP). Phase 3:Serum PCT concentration was signifi cantly higher in patients with septic shock than in those with cardiogenic shock (96.98 +/- 119.61 ng/mL vs. 11.30 +/- 12.3 ng/mL). For discrimination between septic and cardiogenic shock, the best cutoff value was 10 ng/mL, with sensitivity of 100% and specificity of 62%. Conclusion:Cardiac surgery with cardiopulmonary bypass influences serum PCT concentration with a peak on POD 1. In the presence of fever, PCT is a rel iable marker for diagnosis of infection after cardiac surgery, except in pa tients who previously received antibiotics. PCT was more relevant than CRP for diagnosis of postoperative infection. During a postoperative circulator y failure, a serum PCT concentration >10 ng/mL is highly indicative of a se ptic shock.