Associations between oxygen delivery and cardiac index with hyperlactatemia during cardiopulmonary bypass

OBJECTIVE: Metabolism management plays an essential role during cardiopulmonary bypass (CPB). There are different metabolic management devices integrated to heart–lung machines; the most commonly used and accepted metabolic target is indexed oxygen delivery (DO(2i)) (280 mL/min/m(2)) and cardiac index (CI) (2.4 L/min/m(2)), which can be managed independently or according to other metabolic parameters. Our objective was to compare lactate production during CPB procedures using different metabolic management: DO(2i) in relation to indexed oxygen extraction ratio (O(2)ER(i)) and CI in relation to mixed venous oxygen saturation (SvO(2)). METHODS: Data on 500 CPB procedures were retrospectively collected in a specialized regional tertiary cardiac surgery center in Italy between September and 2012 and November 2019. In group A, the DO(2i) with 280 mL/min/m(2) target in relation to O(2)ER(i) 25% was used; in group B, CI with 2.4 L/min/m(2) target in relation to SvO(2) 75% was used. During CPB, serial arterial blood gas analyses with blood lactate and glucose determinations were obtained. Hyperlactatemia (HL) was defined as a peak arterial blood lactate concentration >3 mmol/L. The postoperative outcome of patients with or without HL was compared. RESULTS: Eight pre- and intraoperative factors were found to be significantly associated with peak blood lactate level during CPB at univariate analysis. HL (>3 mmol/L) was detected in 15 (6%) patients of group A and in 42 (16.8%) patients of group B (P = .022); hyperglycemia (>160 mg/dL) was found in 23 (9.2%) patients of group A and in 53 (21.2%) patients of group B (P = .038). Patients with HL during CPB had a significant increase in serum creatinine value, higher rate of prolonged mechanical ventilation time and intensive care unit stay. A cutoff of DO(2i) <270 mL/min/m(2) in relation to O(2)ER(i) >35% in group A and a cutoff of CI <2.4 L/min/m(2) in relation to SvO(2) <65% in group B were found to have a positive predictive value of 80% and 75% for HL, respectively. A cutoff of DO(2i) >290 mL/min/m(2) in relation to O(2)ER(i) 24% in group A and a cutoff of CI >2.4 L/min/m(2) in relation to SvO(2) >75% in group B were found to have a negative predictive value of 78% and 62% for HL, respectively. CONCLUSIONS: This retrospective observational analysis showed that management of DO(2i) in relation to O(2)ER(i) was 16% more specific in terms of negative predictive value for HL during CPB compared with the use of CI in relation to SvO(2). Group A reported a significant reduction in the incidence of intraoperative lactate peak, correlated with postoperative reduction of serum creatinine value, mechanical ventilation time, and intensive care unit stay, compared with group B.