Difficult separation from cardiopulmonary bypass and Delta PCO2

Purpose: Veno-arterial and regional differences of the partial pressure in CO2 (Delta PCO2), may be used as index to evaluate the adequacy of the card iac output to the oxygen consumption. To determine the incidence of elevate d Delta PCO2 and its relationship with difficult separation from bypass (DS B) in patients undergoing cardiac surgery, we conducted a prospective obser vational cohort study. Methods: Data were collected from 58 consecutive patients undergoing variou s cardiac operations requiring cardiopulmonary bypass (CPB), During the pro cedure, arterial and venous blood gases and lactate were sampled. Blood was drawn after induction of anesthesia, during bypass and at the closure of t he chest wail. Difficult separations ration from bypass was defined as a sy stolic arterial pressure < 80 mmHg, and diastolic pulmonary artery pressure > 15 mmHg during progressive separation from CPB with inotropic or mechani cal support of cardiac function, or hemodynamic instability resulting in re introduction of extra-corporeal circulation or insertion of an intra-aortic balloon pump. Results: In our study, 65% of the samples were associated with elevated Del ta PCO2 (> 6mmHg). Variables associated with difficult weaning were LVEF; d uration of bypass and aortic cross-clamping, pre-bypass Delta PCO2 and in b ypass lactate values (P < 0.05). Multivariable analysis identified the pre- bypass <Delta>PCO2 and the duration of bypass as predictors of DSB. Conclusion: Elevated Delta PCO2 is frequently observed during cardiac surge ry and values obtained before bypass were associated with DSB. The Delta PC O2 gradients could be used as marker of the adequacy of tissue perfusion du ring cardiac surgery.