Perfusing and ventilating the patient’s lungs during bypass ameliorates the increase in extravascular thermal volume after coronary bypass grafting

Abstract

Background To test the hypothesis that bilateral extracorporeal circulation (ECC) (Drew technique) ameliorates the increase in extravascular thermal volume (ETV) observed after conventional cardiopulmonary bypass (CPB) in patients undergoing coronary artery bypass grafting. Methods Thirty-four consecutive patients underwent either bilateral ECC (n = 24, additional cannulation of pulmonary artery and left atrium and lungs perfused and ventilated during bypass) or conventional CPB (n = 10, right atrial and aortic cannulation, lungs statically inflated to 4 mbar (0.41 cm H 2O) with oxygen, 500 mL/min). Determinations of ETV (thermodye dilution technique) and intraoperative fluid balance were made before surgery, at the end of surgery, and 4 hours thereafter. In addition, interleukin (IL)-8, thromboxane B2 (TxB 2), and endothelin (ET)-1 concentrations were measured in the right atrium and pulmonary vein at specified time points. Results Comparisons of ETV made at the start of surgery, after aortic declamping, and after termination of ECC, respectively, revealed an increase from 4.8 ± 0.2 mL/kg (mean ± SEM) to 6.7 ± 0.4 mL/kg, and 6.3 ± 0.3 mL/kg with conventional CPB but ETV remained unchanged at 5.2 ± 0.3 mL/kg, 5.1 ± 0.2 mL/kg, and 4.9 ± 0.3 mL/kg with bilateral ECC. Priming volume (1,580 ± 10 mL versus 2,213 ± 77 mL, p < 0.001) and intraoperative fluid balance (+1,955 ± 233 mL versus +2,654 ± 210 mL, p < 0.05) were less with conventional CPB. Concentrations of IL-8, TxB 2, and ET-1 were not different between groups. Conclusions Despite a significantly greater prime volume and a more positive intraoperative fluid balance, ETV did not change with bilateral ECC but increased with conventional CPB. Thus, using the patient’s lungs as an oxygenator during bypass mitigates the increase in extravascular pulmonary fluid.