Oxygen metabolism during cardiopulmonary bypass with hemodilution using liposome-encapsulated hemoglobin in kid goats.

Cardiopulmonary bypass (CPB) with hemodilution has been proposed as a useful method for many types of cardiovascular surgery. Although the harmful effects of severe hemodilution need to be prevented, blood transfusion should be avoided whenever possible. Therefore, we have been developing a new CPB technique using liposome-encapsulated hemoglobin (LEH). The purpose of this study was to evaluate the combined therapy of diluted CPB and LEH focusing on the influence of LEH on oxygen metabolism. Male kid goats (n = 8) were divided into two groups: the LEH and control groups. CPB was maintained at between 36 degrees and 37 degrees C. There was no significant difference in hemoglobin concentrations (6.3 +/- 1.5 g/dl in the LEH group and 6.2 +/- 1.3 g/dl in the control group) after initiation of CPB between the two groups. Thus, there was no distinction in oxygen deliveries between the two groups (11.0 +/- 2.0 ml/kg/min in the LEH group and 11.0 +/- 2.3 ml/kg/min in the control group). Oxygen consumption in the LEH group (2.5-2.7 ml/kg/min), however, had a tendency to be higher than that in the control group (2.4-2.5 ml/kg/min). In addition, the lactate/pyruvate ratio decreased earlier in the LEH group. These results suggest that the application of LEH in the pump-priming solution improves decreased aerobic oxygen metabolism during CPB without any serious adverse effects.