No abstract

Infusion of propofol by a target-controlled infusion (TCI) system is effective in achieving conscious sedation for anxious patients presenting for dental surgery. It is a common clinical observation that anxious patients require more anaesthetic drugs than non-anxious individuals. In study 1 we have defined blood propofol concentrations necessary for conscious sedation in both anxious (n = 23) and non-anxious (n = 18) patients. The pump performance of the TCI system, using Gepts' pharmacokinetic model, was evaluated in these two patient groups. Subsequently, clearance of propofol was compared in the two groups. Mean measured venous serum propofol concentrations obtained between 20 and 35 min after the optimal sedation level was reached were 1.6 (SD 0.2) micrograms ml-1 in the anxious patients compared with 1.7 (0.3) micrograms ml-1 in the control group (study 1) and 1.4 (0.27) micrograms ml-1 in study 2. The pump systematically overpredicted measured propofol concentrations in both groups (study 1). There was no significant difference in propofol clearance between the two groups. In study 2, an optimized set of microconstants was derived which should more accurately predict the pharmacokinetic profile of the anxious population and this set was tested prospectively in another group of 12 anxious dental patients. Bias and precision with the optimized kinetic set were significantly less than the values obtained in study 1. We conclude that there was no significant pharmacokinetic differences between anxious and non-anxious subjects receiving subanaesthetic doses of propofol for conscious sedation.

Hypoventilation as a consequence of deep intravenous sedation is the most frequently reported cause of cardiac arrest during upper gastrointestinal endoscopy (UGIE). Haemodynamic stress can contribute to myocardial ischaemia; therefore, this study was designed to observe prospectively the cardiorespiratory changes during UGIE using either midazolam or propofol for conscious sedation. Thirty-four patients, aged 50 years and older, ASA physical status I-III, scheduled for elective UGIE with sedation, were studied. Oxygen saturation, heart rate, non-invasive blood pressure and Holter ECG were recorded continuously starting 15 min before sedation until 15 min after the endoscopy. In addition, plasma catecholamine concentrations were determined. The results of this study are consistent with previous reports that cardiopulmonary events may occur during endoscopy, with or without sedation. Both midazolam and propofol sedation may provide some protection against haemodynamic stress in response to insertion and manipulation of the endoscope, but sedation can also contribute to the occurrence of hypoxaemia.

No abstract