Hemodynamic effects of ventilating or not, during cardiopulmonary bypass in a porcine model

Background Optimal ventilator setting during cardiopulmonary bypass is unknown. Improved gas exchange and lung compliance have been suggested as favorable outcomes when lungs are ventilated. However, long-time effects have been hard to demonstrate. There has been less focus on the immediate circulatory effects of ventilator settings during cardioplegia and cardiopulmonary bypass, and potentially hemodynamic effects of different ventilator strategies are unknown.Methods Sixteen anesthetized pigs on normothermic cardiopulmonary bypass with 80 minutes of aortic cross-clamp and cardioplegic arrest were randomized to a ventilated and a not ventilated group. After weaning, both cardiac-, hemodynamic-, and pulmonary functions were evaluated for up to 120 minutes. Results: Left ventricular variables and cardiac output did not differ between the two study groups, neither before nor after weaning. After weaning, mean pulmonary artery pressure was increased in ventilated compared to not ventilated animals. Neither pulmonary compliance nor oxygen uptake differed between groups in surviving animals. Conclusions: Disconnection of the ventilator during cardiopulmonary bypass and cardiac arrest did not affect lung compliance and oxygen uptake, neither positively nor negatively. In the ventilated group a temporary increase in the pulmonary pressure after weaning was observed.