I.v. anaesthesia and EEG burst suppression in rats: bolus injections and closed-loop infusions.
We describe a system for monitoring and controlling i.v. anaesthesia in rats using burst suppression ratio (BSR) detection in the extradural EEG. After bolus injection, peak BSR values of 95% were achieved with propofol 8 mg kg-1, etomidate 3.5 mg kg-1 and alphaxalone 4.5 mg kg-1. Thiopental 32 mg kg-1 produced a peak BSR of 70% (larger doses were not tolerated). Recovery was fastest with propofol, followed by etomidate and alphaxalone with equal duration, and slowest with thiopental. In further experiments, a closed-loop infusion system maintained BSR accurately at targets of 30%, 50%, 70% or 90% for 60 min with propofol or etomidate. During these experiments the infusion rates were found to decrease with time, more so with etomidate (approximately 40%) than with propofol (approximately 20%). Recovery times were 2-3 times longer with etomidate than with propofol. This model demonstrated differences between i.v. anaesthetics and may be useful in screening new compounds in preclinical development.
Vijn
P C
PC
Organon Laboratories Ltd, Newhouse.
Sneyd
J R
JR
D000771:Anesthesia, Intravenous / Q000379:methods*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D000818:Animals; D016503:Drug Delivery Systems / Q000379:methods*; D004569:Electroencephalography / Q000187:drug effects*; D005045:Etomidate / Q000008:administration & dosage; D005246:Feedback; D007260:Infusion Pumps; D007262:Infusions, Intravenous; D007275:Injections, Intravenous; D008297:Male; D015742:Propofol / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar
D018686:Anesthetics, Intravenous; D015742:Propofol; D005045:Etomidate