[Oxygen uptake and blood circulation parameters during anesthesia using EEG-assisted determination of anesthetic dosages].

Abstract

Anaesthesia has significant effects on circulation and oxidative metabolism which are closely related to each other. Usually there is a marked reduction of oxygen uptake (VO2) and energy expenditure. A controversial discussion on the effects of the drugs administered and the degree of metabolic depression has continued in the literature fuelled by a lack of studies in patients under standardized conditions. 18 patients (ASA I-II) scheduled for major abdominal surgery were given closed-loop feedback control anaesthesia by quantitative EEG analysis. Group 1 received a total intravenous anaesthesia with methohexital and fentanyl whereas group 2 was given a combined anaesthesia with alfentanil and N2O. The aim of this comparative study was to evaluate the effects of different techniques for general anaesthesia on oxygen uptake and on the cardiovascular system. Preanaesthetic values of VO2 taken after flunitrazepam premedication were slightly below the predicted range determined by indirect calorimetry for basal metabolism. Steady-state general anaesthesia led to an approximately 30% reduction of VO2 for both groups. In contrast to oxygen uptake, blood pressure and especially heart rate were defined by the type of anaesthesia as in the methohexital fentanyl group higher values of both blood pressure and heart rate were observed.