Mini-circuit cardiopulmonary bypass with vacuum assisted venous drainage: feasibility of an asanguineous prime in the neonate.

Conventional cardiopulmonary bypass (CPB) in neonates results in increased transfusion requirements and hemodilution. There has been little advancement in CPB for the neonatal population. There is evidence that increased priming volumes and blood product transfusion enhances inflammatory response to CPB and increases myocardial and pulmonary dysfunction. We have devised a miniaturized CPB circuit that utilizes vacuum-assisted venous drainage (VAVD) in an effort to decrease priming volume and avoid transfusion requirements. The purpose of this study was to evaluate the safety and efficacy of this miniaturized CPB system and determine the feasibility of an asanguineous prime. Ten 1-week-old piglets were randomized to five mini- and five conventional CPB pump circuits. Subjects were supported with CPB at 100 ml/kg/min, cooled to 28 degrees C, exposed to 10 min aortic crossclamp with cardioplegic arrest, rewarmed to 37 degrees C, weaned from bypass, and subjected to modified-ultrafiltration (MUF) for approximately 10 min. This method was chosen to simulate a situation with all the elements of clinical CPB. Blood transfusion trigger was a hematocrit <15 on CPB. Serum samples were obtained pre-CPB, at 15 min of CPB onset, immediately post-CPB completion, and immediately post-MUF. Indices of hemolysis (SGOT, LDH), production of inflammatory mediators (interleukin (IL)-8, tumor necrosis factor-alpha (TNFalpha)), and physiologic parameters of inflammation were measured. The overall blood requirement was significantly less in the mini-circuit compared to conventional CPB (47.0+/-5.8 ml vs 314.2+/-31.6 ml; p < 0.0001). The only significant blood requirement in the mini-circuit was to replace the volume removed for samples. During the study, mean arterial pressure (MAP) (p = 0.004), static pulmonary compliance (p = 0.04), platelets (p = 0.0003), and white blood cells (p = 0.003) significantly decreased across the groups. Lung water content (p = 0.02), TNFalpha levels (p = 0.05), and SGOT (p = 0.009) increased significantly during the study, across the groups. Among all parameters tested, except for blood requirement and hematocrit post-CPB, there were no significant differences between the two circuits. VAVD makes asanguineous prime in neonates feasible. When used in this study to miniaturize a conventional-CPB circuit, VAVD with a reconfigured neonatal CPB console and circuit resulted in no detrimental effects, and allowed for markedly decreased priming volumes and blood transfusion requirements.