[The effect of Fentanyl and Althesin on haemodynamics, inotropism of the heart and myocardial oxygen consumption in man (author's transl)]

Abstract

The acute effect of Fentanyl and Althesin upon haemodynamics, inotropism of the heart and myocardial oxygen consumption has not been studied in man so far. Healthy premedicated pateints (n = 16) were lightly anaesthetized with nitrous oxide-oxygen (ratio 2:1), 0.3 Vol.-% forane and 0.3 Vol.-% halothane respectively. In order to avoid any interference with respiratory depression all subjects were normoventilated via an orotracheal tube. In a circulatory steady state a single dose of 0.01 mg/kg Fentanyl (n = 7) and 0.075 mg/kg Althesin (n = 9) respectively was injected intravenously within 20 sec. After the application of Fentanyl there was a delayed (5th min) fall in blood pressure by 23%, which was due to a reduction in total peripheral resistance (12%) and in cardiac output (thermodilution technique) by 13%. The decrease in cardiac output was the result of a bradycardia (18%). Considering heart rate, pre- and afterload simultaneously, the fall in max dp/dt (catheter-tip manometer) by 20% could not be explained as a decrease in myocardial contractility. The altered haemodynamics led to a decrease of the myocardial oxygen consumption (control 6.4 ml O2/min x 100 g) by 31%. The energy demand of the heart was quantitatively calculated using the formula of the complex haemodynamic parameter developed by Bretschneider. Immediately after the administration of Althesin the cardiac output rose on account of tachycardia slightly, while stroke volume (19%), total peripheral resistance (32%) and mean arterial pressure (24%) reacted reversely. Since heart rate increased (11%), preload remainded unchanged and afterload decreased, the fall in dp/dt max (20%) has to be understood as a moderate reduction in myocardial inotropism. The energy demand of the heart decreased only initially by 15%. The clinical implications of the results were discussed.