SummaryThe haemodynamic eflects of propofol (2 mglkg), etomidate (0.2 mglkg) and thiopentone ( 4 mglkg) were studied in 30 ASA 1 and 2 patients in whom anaesthesia had been induced with midazolam 0.1 mglkg, fentanyl5 pglkg, vecuronium 0.1 mglkg and atropine 10 pglkg, and maintained with nitrous oxide in oxygen. Arterial pressure was measured directly and left ventricular diameters were determined by transoesophageal echocardiography. Systolic blood pressure after propofol and thiopentone and the end-systolic quotient (systolic pressurelend-systolic diameter), a measure of inotropy, decreased. Fractional shortening ( end-diastolic -end-systolic diameterlend-diastolic diameter) decreased only in the thiopentone group, Diastolic blood pressure and end-diastolic diameter ( a measure of preload) did not change in any of the groups, and the etomidate group showed no changes in the haemodynamic variables measured. Propofol shows simultaneous negative inotropy and afterload reduction, while thiopentone is exclusively negatively inotropic.
Key wordsAnaesthetics, intravenous; propofol, thiopentone, etomidate. Measurement techniques; transoesophageal echocardiography, electroencephalography.Many studies have reported a reduction in arterial blood pressure after injection of the intravenous anaesthetic agent propofol. Reductions in blood pressure were more marked, and hypotensive reactions more frequent after propofol in comparison with etomidate' and thio~entone?~ but there is still no consensus in the literature why these reductions occur, be they negative inotropy, afterload reduction or both.Almost all the patient studies to date, which were based on load-dependent variables, have differentiated poorly between the inotropic effects of propofol and its influence on myocardial loading factors.The aim of our study was to demonstrate whether the decrease in arterial blood pressure after propofol is from negative inotropy and (or) changes in myocardial loading (prelafterload), using a method considered to be relatively insensitive to load factors: namely inotropy measurements by transoesophageal echocardiography (TEE). In addition, we compared the haemodynamic effects of propofol with those of thiopentone and etomidate.
MethodsThirty normotensive surgical or orthopaedic patients in ASA groups 1 and 2 were placed at random into either a propofol (n = lo), thiopentone (n = 10) or etomidate (n = 10) group. None of the patients was receiving any concomitant cardiovascular medication, and all gave written informed consent to the study; the study itself was approved by the Ethics committee of the University of Ulm.Each patient received orally 20 mg clorazepam as premedication one hour before the study. We injected atropine 10 pg/kg intravenously 5 minutes before induction, which was with midazolam 0.1 mg/kg and fentanyl 5 pg/kg. Vecuronium 0.1 mg/kg was given to facilitate tracheal intubation. Anaesthesia was continued after tracheal intubation, with controlled ventilation with N,O:O, (no, = 0.3) to normocapnia (PE'co, = 4.6-6.0 k...