PubMed1992
The intravenous anaesthetic agent propofol has become more and more popular not only for induction but also for the maintenance of anaesthesia in all fields of surgery. For this purpose, different infusion rates and also combinations of propofol with opioids, nitrous oxide and volatile anaesthetic agents have been described. The present study was designed to find the best dosage regimen for short operations and rapid changes. The necessity for the frequently recommended standardized combination of propofol with opioids should be checked with respect to the cardiovascular effects. METHODS. A series of 60 patients (ASA I and II, age range 22-79 years) selected for discectomy were prospectively randomized to three groups. Half an hour before operation all patient received 0.5 mg atropine, 50 mg promethazine and 50 mg pethidine as i.m. premedication. In all groups anaesthesia was induced with propofol in a bolus dose of 2.5 mg/kg body weight over a period of approximately 45 s. After 5 mg atracurium the patients were intubated under 100 mg succinylcholine and normoventilated with 70% nitrous oxide and 30% oxygen. For relaxation 25 mg of atracurium were given. In group I propofol was administered in a dosage of 15 mg/kg body weight per hour for 10 min after induction. After this time the propofol infusion was reduced to 6 mg/kg body weight per hour. Group II received 0.1 mg fentanyl before induction. The dosage of propofol was similar to group I. In group III 0.1 mg of fentanyl was administered before induction and propofol was given with an infusion rate of 6 mg/kg body weight from the beginning. The following parameters were controlled and documented: systolic and diastolic blood pressure (SAP and DAP), heart rate (HF), end-expiratory carbon dioxide (eeCO2), inspiratory oxygen concentration (FiO2) and peripheral oxygen saturation (sO2). Recovery time was determined as the time from the end of the propofol infusion until eye-opening on command. RESULTS. In all groups anaesthesia could be induced and maintained without complications. There was a slight increase in SAP in group I after intubation, while in the groups with fentanyl a pronounced decrease of SAP was found simultaneously with induction of anaesthesia (Fig. 1). In group I HF showed significantly higher values after intubation and for the next 15 min than in group II and group III. A rapid and pronounced increase of end-tidal carbon dioxide occurred in the fentanyl groups with the beginning of spontaneous ventilation at the end of anaesthesia. There was a significantly longer recovery time in group II with fentanyl and initial higher propofol infusion rate. A correlation between dosage of propofol and recovery time could not be found. DISCUSSION. The results of this study demonstrate that a routine combination of propofol with opioids is not necessary even for painful surgical procedures if the propofol dosage is initially increased. There are differences in cardiovascular reactions between group I without and groups II and III with fentanyl, but in our patients these changes were of no clinical importance. An additional administration of fentanyl can prevent hypertensive reactions or tachycardia with intubation, but on the other hand fentanyl can also increase the cardial depression of propofol with a dangerous decrease in blood pressure and heart rate. Therefore in combination with opioids lower doses of propofol should be used for induction and maintenance of anaesthesia. If opioids are administered, signs of a residual postoperative respiratory depression have to be taken seriously.