[Anesthesia induction using etomidate in a lipid emulsion]

The use of etomidate as an anaesthetic induction agent has been hampered significantly by unwanted side effects such as pain on injection and thrombophlebitis. Investigations by Doenicke et al. have shown that the solubilizer propylene glycol is responsible for these side effects and that they can be avoided by the use of a lipid emulsion formulation. It was the goal of the present study to quantitate the reduction of thrombophlebitis and pain on injection following both formulations under double-blind study conditions. METHODS. In 100 patients anaesthesia was induced either with a new galenic formulation of etomidate--etomidate in lipid emulsion formulation (Lipofundin MCT 20%; eto-lip)--or with etomidate in propylene glycol 35% (eto-pg). Both groups received 0.3 mg kg-1 etomidate in double-blind randomized fashion. After the injection of etomidate the venous cannula was removed. The observing anaesthetist was unaware of the study drug used, to guarantee blinded investigation conditions. Discomfort and pain during and following injection were recorded, as was local skin irritation. Venous sequelae were assessed for 7 days following injection to register the occurrence of thrombophlebitis. RESULTS. Demographic data were not different between the two groups. For induction of anaesthesia the same dose of both preparations was necessary, and no difference in heart rate and blood pressure before, during or after anaesthesia induction was observed. Pain on injection (78% vs 14%), myoclonus (24% vs 8%) and local skin reaction (50% vs 6%) were present significantly more often in the eto-pg group (P < 0.01; P < 0.05 respectively, chi-square test) than in the eto-lip group. On the 1st and 2nd postoperative days, examination of the injected vein revealed a significantly higher incidence of symptoms of thrombophlebitis in the group treated with eto-pg (25% vs 3%). CONCLUSION. From these results it is concluded that in terms of vein compatibility the new galenic formulation of etomidate with lipofundin MCT 20% is superior to the propylene glycol preparation while pharmacodynamic properties seem not to be affected.