[Influence of posture changes on hemodynamics under fentanyl-diazepam anesthesia--effects of nitrous oxide]

Abstract

Patients for myocardial revascularization were divided into 50% oxygen-50% nitrogen group (group A) and 50% oxygen-50% nitrous oxide group (group B) according to the kind of gas administered after the induction of anesthesia. Anesthetic induction was carried out with fentanyl and diazepam in both groups. With sufficient hemodynamic stabilization following the induction of anesthesia, the hemodynamic parameters were measured in supine position for baseline data (BASELINE). The operating table was kept at Trendelenburg position (TREND), i.e., head down position, to measure hemodynamic parameters. Next, the operating table was kept at Fowler position (FOW), i.e., head up position, and hemodynamic parameters were measured. Heart rate was little influenced by posture change in both groups. While mean arterial pressure, mean pulmonary arterial pressure, central venous pressure and pulmonary capillary wedge pressure increased significantly in TREND in both groups, and decreased significantly in FOW. Cardiac index increased significantly in TREND in group A, but no such change occurred in group B. In FOW, cardiac index showed no significant change in group A, but decreased significantly in group B. Systemic vascular resistance was little influenced by posture change in both groups. This study suggests that it is necessary to exert a great caution in administering nitrous oxide when posture change is needed under fentanyl-diazepam anesthesia.