Factors that determine cell-free hemoglobin concentration in blood prime during cardiac surgery with cardiopulmonary bypass: a prospective observational study

Abstract

INTRODUCTION: Plasma cell-free hemoglobin (Hbf) has a negative effect on the results of cardiac surgery. OBJECTIVE: Analysis of the dynamics of the Hbf during cardiosurgical operations with CPB. Identification of the main factors for increasing the Hbf. MATERIALS AND METHODS: A prospective, single-center, cohort study included 50 patients who underwent cardiac surgery with CPB. Hbf was monitored before surgery, during CPB (10 minutes after the start, then every 30 minutes) and every 6 hours for two days. RESULTS: An increase in Hbf levels was found in 90 % of surgical procedure. In 8 % of cases, hemolysis was mild (0.1 < Hbf ≤ 0.4 g/l), in 48 % — moderate (0.4 < Hbf < 1 g/l), severe (Hbf ≥ 1 g/l) was after 34 % of operations. After weaning from CPB Hbf rapidly decreases and after 12 hours drop to the preoperative level. Aortic cross-clamping is a risk factor with an odds ratio of 1.038 (p = 0.036). A positive correlation was established between the Hbf level and the duration of CPB (r = 0.76; p < 0.001). In ROC-analysis, a good predictive ability for development of severe hemolysis was demonstrated by the time of CPB: AUC 0.74 (p = 0.014) with a threshold value of 76 minutes. During CABG, severe hemolysis developed significantly less frequently than during valve corrections — 12.5 % versus 44.1 %, p = 0.026. Hbf content was significantly lower with an initial hemoglobin concentration < 140 g/l than in patients with an initial hemoglobin level ≥ 140 g/l — 0.7 (0.5; 0.95) g/l versus 0.9 (0.7; 1.28) g/l, p = 0.036. CONCLUSIONS: Hemolysis is typical for the cardiac surgeries with CPB. The time of aoral clamping and CPB, the type of surgcry, the hemoglobin content before surgcry have an impact on the severity of hemolysis.