REDUCTION IN PRIME VOLUME ATTENUATES THE HYPERDYNAMIC RESPONSE AFTER CARDIOPULMONARY BYPASS

Background. A hyperdynamic response to cardiopulmonary bypass is chara cteristically observed in the postoperative course. To determine the e ffect of prime volume on the hemodynamic response, a database study wa s performed on patients who underwent elective coronary artery bypass grafting with an extracorporeal circuit with either a large prime volu me (2,350-mL prime, n = 20) or a small prime volume (1,400-mL prime, n = 20). Methods. Measurements were carried out at fixed time points be fore and after cardiopulmonary bypass (until 18 hours postoperatively) and include hematocrit, colloid oncotic pressure, fluid balance, and hemodynamic profile (mean of three measurements). Results. The lower c olloid oncotic pressure in the large prime group (16.2 +/- 0.6 mm Hg v ersus 19.1 +/- 1.1 mm Hg, p = 0.0002) was associated with a highly pos itive fluid balance (5.5 +/- 0.9 L versus 2.8 +/- 0.7 L, p = 0.0001). With the on-bypass hematocrit aimed at 22% to 23%, autologous blood wa s predonated by 16 patients in the small prime group but by none in th e large prime group. Reinfusion of autologous blood resulted in a redu ction in blood bank requirements (p = 0.03). Mean arterial pressure wa s 83 +/- 4 mm Hg for small prime versus 76 +/- 4 mm Hg for large prime (p = 0.01). Cardiac index was 2.9 +/- 0.2 L . min(-1). m(-2) for smal l prime versus 3.8 +/- 0.3 L . min(-1). m(-2) for large prime (p = 0.0 001). Pulmonary vascular resistance index was 281 +/- 40 dyne . s . cm (5) . m(-2) for small prime versus 188 +/- 22 dyne . s . cm(5) . m(-2) for large prime (p = 0.0009). Oxygen delivery was 42 +/- 5 mL . min(- 1). m(-2) for small prime versus 51 +/- 3 mL . min(-1). m(-2) for larg e prime (p = 0.004). Vasoactive medication was not different among gro ups. Conclusions. Reduction in prime volume attenuates the hyperdynami c response after cardiopulmonary bypass. Furthermore, an important red uction in blood bank products can be obtained with small prime volumes .