Effectiveness of stroma-free hemoglobin solution as seen in a right heart bypass swine model

To determine if tolerance to severe anemia (Hct less than or equal to 10%) might be improved with stroma-free hemoglobin solution (SFH), 15 swine were placed on normothermic right heart bypass (RHBP) for evaluation of stroke volume (SV), coronary blood flow (CBF), arterial-coronary sinus oxygen content difference S(a-cs)O2, and myocardial oxygen consumption (MVO2) during a control period at a hematocrit (Hct) level of 30%. These 15 animals, divided into three equal groups, subsequently underwent exchange transfusion either to a Hct of 5% using 7% SFH (group 1), or to a Hct of 5% (group 2) or 10% (group 3) using 7% bovine albumin solution. All tests were repeated during these experimental conditions. Myocardial performance after albumin solution exchange was sustained on RHBP in only 1 of 10 animals. SFH animals (group 1) had a significant drop in SV at 14 torr after exchange (20 +/- 3 ml vs 10 +/- 4 ml, p less than 0.025), but this 50% performance level could be sustained. CBF rose and MVO2 fell in all groups, although the statistically nonsignificant mean differences were less with SFH. S(a-c)O2 fell significantly (p less than 0.05) with albumin solution (group 2 7.3 +/- 1.4 vs 2.2 +/- 0.2, group 3 8.9 +/- 2.0 vs 3.8 +/- 1.0), and nonsignificantly with SFH (5.6 +/- 0.7 vs 4.1 +/- 1.4). Although myocardial performance decreased with SFH, the authors believe these comparative results support the use of SFH at an Hct of 5%.