A comparison of induction of anaesthesia using two different propofol preparations
Terblanche, N and Coetzee, JF, A comparison of induction of anaesthesia using two different propofol preparations, Southern African Journal of Anaesthesia and Analgesia, 14, (6) pp. 25-29. ISSN 2220-1181 (2008) [Refereed Article]
Copyright 2008 SA Society of Anaesthesiologists. Licensed under Creative Commons Attribution-NonCommercial-NoDerivs 2.5 South Africa (CC BY-NC-ND 2.5 ZA) https://creativecommons.org/licenses/by-nc-nd/2.5/za/
Background: Investigators have reported inter-patient variability with regard to propofol dosage for induction of anesthesia,
since early dose finding studies. With the arrival of generic formulations of propofol, questions have arisen regarding further
variability in dose requirements. Various studies have confirmed that generic propofol preparations are pharmacokinetically
and pharmacodynamically equivalent to DiprivanŽ. Nevertheless a number of practitioners are under the impression that
certain generic propofol preparations require greater doses for induction of anaesthesia than does DiprivanŽ.
Methods: 20 female patients of ASA status I-II, between the ages of 18-55 years, scheduled for routine surgery were randomly
allocated to two groups to undergo induction of anaesthesia using two different propofol formulations; DiprivanŽ and
Propofol 1% FreseniusŽ. Either preparation was administered using a target-controlled infusion of propofol (STEL-TCI)
targeting the plasma (central) compartment at a concentration of 6 ėg.ml-1, employing the pharmacokinetic parameters of
Marsh et al. A processed EEG (bispectral index) was continuously recorded. Loss of consciousness (LOC) was regarded as
the moment at which the patient could not keep her eyes open and was confirmed by the absence of an eyelash reflex.
At this point propofol administration was discontinued and data were recorded for a further two minutes, before administering
an appropriate opioid and/or nitrous oxide/volatile agent and/or muscle relaxant to maintain anaesthesia. Time to LOC
after start of propofol administration, and the dose of propofol administered during induction were annotated.
Results: There were no demographic differences between the groups. There were no differences between the groups with
regard to the mean dose for LOC, time to LOC and to the mean BIS values obtained at the following stages: awake, at LOC,
at 1 and 2 minutes after LOC as well as the lowest recorded value.
Conclusions: Our results confirm that the two propofol formulations that we studied, are pharmacologically equivalent with
regard to induction of anaesthesia. Other mechanisms can explain the variability in clinical response to bolus administration
of propofol. The most important is the recirculatory or "front-end" kinetics of propofol in which cardiac output plays a major
role, as well as the rate of drug administration. Emulsion degradation can also influence dose-response and in this regard
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