Total I.V. Anaesthesia With Propofol and Alfentanil: Dose Requirements for Propofol and the Effect of Premedication With Clonidine †

Abstract

We determined in 51 healthy patients undergoing body surface surgery the dose requirements for propofol, as part of a total i.v. anaesthesia technique with an alfentanil infusion. After premedication with temazepam, patients received alfentanil 50 micrograms kg-1 followed by an infusion of 50 micrograms kg-1 h-1. Patients were anaesthetized with a loading dose of propofol followed by a three-stage infusion designed to reach one of five preselected blood concentrations of propofol. The motor response to the initial surgical incision was noted and probit analysis was used to derive the ED50 (2.94 mg kg-1 h-1; 95% confidence limits: 2.35-3.37 mg kg-1 h-1) and ED95 (4.98 mg kg-1 h-1; 95% limits: 4.13-8.8 mg kg-1 h-1) for the final propotol infusion rate under these conditions. Whole blood concentration!of propofol at the time of the incision was related linearly to the inf!sion rate and the EC50 and EC95 (probit analysis) were derived as !.44 (95% confidence limits 0.62-1.87) and 4.05 (95% confidence lim!ts 2.78-30.5) micrograms ml-1, respectively. Post-operative recovery was!rapid, uncomplicated and uneventful. In a subgroup of eight patients,!the addition of clonidine 0.6 mg to the premedication significantly decreased the requirement for propofol (P less than 0.05) during surgery, but resulted in prolonged recovery times.

The effect of intravenous dexmedetomidine premedication on the dose requirement of propofol to induce loss of consciousness in patients receiving alfentanil

“…Comparison of EC 50 values for propofol at comparable concentrations of alfentanil give an indication of equipotency. At the lowest propofol infusion rate (2.4 mg.kg 21 .h 21 ), no patients moved, compared with seven of 10 in a study by Richards et al [18]; only three of 40 patients moved in our study as a whole compared with 15 of 50 in Vuorilehto et al [16]. The study by Richards and colleagues was conducted in exactly the same way as this study, except that the alfentanil loading dose and infusion were started at the same time as the propofol and the patients were premedicated with 20±30 mg temazepam.…”

“…Data for move/no move in response to surgical incision are shown for comparison from the study by Richards et al [18] in which patients received the same propofol infusion regimen, with alfentanil commenced at the same time as the propofol, but without dexmedetomidine. At the lowest final propofol infusion rate of 2.4 mg.kg 21 .h 21 , none of the eight patients moved, and only three of the 40 patients moved in response to the initial surgical incision ( Table 4).…”

Influence of sex on propofol metabolism, a pilot study: implications for propofol anesthesia

“…A validating investigation with an extended blood sampling period after propofol administration and more rigorous analysis of interrelated variables is required to confirm this hypothesis. Moreover, the role of confounding factors that may affect propofol metabolism, such as decrease in hepatic perfusion caused by propofol itself [32] and the coadministration of alfentanil [33], should be explored.…”

Recovery from pre‐operative sedation with clonidine—brain stem auditory evoked response

“…However, in these studies [ 1,2, 141 this rapid recovery following clonidine premedication can be explained by reduced requirements for anaesthetics. On the other hand, Richards and colleagues reported prolonged recovery after oral premedication with clonidine and propofol-alfentanil anaesthesia [20]. In that study, clonidine was administered in a dose 1.5 times greater than that used here and it was given in combination with benzodiazepine, thus indicating that recovery after clonidine premedication is dose dependent.…”