The effect of lipid emulsion on depth of anaesthesia following thiopental administration to rabbits.

Intravenous lipid emulsion has proven benefit in lipophilic drug-induced cardiotoxicity. Its effect in reversal of central nervous system depression secondary to overdose with lipophilic psychotropic agents remains uncertain. Twenty adult New Zealand White rabbits were anaesthetised with 20 mg.kg(-1) thiopental and randomised to receive either 4 ml.kg(-1) saline 0.9% or 4 ml.kg(-1) lipid emulsion 20% immediately afterwards. Depth of anaesthesia was monitored using bispectral index (BIS) at 1-min intervals. Duration of anaesthesia was measured as time to regain the righting reflex (ability of the animal to right spontaneously from dorsal recumbency to sternal recumbency). The BIS was greater in the control group (p = 0.011). The greatest BIS differential was observed immediately following treatment (mean (SD) BIS 75.0 (9.5) for saline vs 58.6 (10.4) for lipid, 95% CI 5.75-27.1; p < 0.001). No difference was observed in duration of anaesthesia (mean (SD) 15.5 (0.8) min for saline vs 15.6 (0.7) min for lipid, p = 0.86). Lipid emulsion administration may serve to increase central nervous system depression in the early phase of lipophilic toxin distribution.