Optimizing liquid ventilation as a lung protection strategy for neonatal cardiopulmonary bypass: Full functional residual capacity dosing is more effective than half functional residual capacity dosing

Objective: To evaluate and compare the protective effects of two different perflubron doses on hemodynamics and lung function in a neonatal animal mod el of cardiopulmonary bypass-induced lung injury. Design: Prospective, randomized, controlled study. Setting: Animal laboratory of the Department of Surgery, Duke University Me dical Center. Subjects: Twenty-one neonatal swine. Interventions: One-wk-old swine (2.2-3.2 kg) were randomized to receive car diopulmonary bypass with full functional residual capacity perflubron (n = 7), cardiopulmonary bypass with half functional residual capacity perflubro n (n = 7), or cardiopulmonary bypass alone (n = 7). This last group served as control animals, receiving cardiopulmonary bypass with conventional vent ilation. Liquid lung ventilation animals received perflubron via the endotr acheal tube at either full functional residual capacity (16-20 mL/kg) or ha lf functional residual capacity (10 mL/kg) before the initiation of cardiop ulmonary bypass. Each animal was placed on nonpulsatile cardiopulmonary byp ass and cooled to a nasopharyngeal temperature of 18 degrees C (64.4 degree s F). Low-flow cardiopulmonary bypass (35 mL/kg/min) was instituted for 90 mins. The blood flow rate was then returned to 100 mL/kg/min. The animals w ere warmed to 36 degrees C (96.8 degrees F) and separated from cardiopulmon ary bypass. Data were obtained at 30, 60, and 90 mins after separation from cardiopulmonary bypass. Measurements and Main Results: Cardiopulmonary bypass without liquid lung v entilation resulted in a significant decrease in cardiac output and oxygen delivery and a significant increase in pulmonary vascular resistance in the post-bypass period. Full functional residual capacity liquid lung ventilat ion administered before bypass resulted in no change in cardiac output and oxygen delivery after bypass. Full functional residual capacity liquid lung ventilation resulted in lower pulmonary vascular resistance after bypass c ompared with both control and half functional residual capacity liquid lung ventilation animals. Conclusions: These data suggest that liquid lung ventilation dosing at full functional residual capacity before bypass is more effective than half fun ctional residual capacity in minimizing the lung injury associated with neo natal cardiopulmonary bypass. Full functional residual capacity dosing may optimize alveolar distention and lung volume, as well as improve oxygen del ivery compared with half functional residual capacity dosing.