THE EFFECTS OF NITROUS-OXIDE ON LEFT-VENTRICULAR SYSTOLIC AND DIASTOLIC PERFORMANCE BEFORE AND AFTER CARDIOPULMONARY BYPASS - EVALUATION BYCOMPUTER-ASSISTED 2-DIMENSIONAL AND DOPPLER-ECHOCARDIOGRAPHY IN PATIENTS UNDERGOING CORONARY-ARTERY SURGERY

We investigated the effects of nitrous oxide (N2O) on central hemodyna mics and left ventricular systolic and diastolic function in 25 patien ts undergoing coronary artery bypass surgery. All patients were receiv ing beta-blockers and had good left ventricular function. Global and r egional systolic left ventricular performance and diastolic function w ere determined by computer-assisted analysis of transesophageal echoca rdiographic (TEE) images, and mitral Doppler flow profiles, respective ly. The patients were anesthetized with fentanyl and ventilated with o xygen in air. Hemodynamic and TEE measurements were obtained before an d after the introduction of N2O in oxygen (60%/40%), before and after cardiopulmonary bypass (CPB). N2O reduced mean arterial pressure, hear t rate, stroke volume, and cardiac output both before and after CPB. L eft ventricular global area ejection fraction (GAEF) was not changed b y the introduction of N2O, either before or after CPB. N2O induced a s ignificant change in regional wall motion after, but not before CPB, a s assessed by the relationship between segmental area ejection fractio n (SAEF) and GAEF. Analysis of the mitral flow profile indicated an in crease in early diastolic relaxation in the pre-CPB period after intro duction of N2O, that was absent in the post-CPB period. We conclude th at N2O induces regional wall motion abnormalities and possibly diastol ic dysfunction post-CPB.