The recovery of horses from inhalant anesthesia: a comparison of halothane and isoflurane.
OBJECTIVE
Recovery is one of the more precarious phases of equine general anesthesia. The quality and rate of recovery of horses from halothane and isoflurane anesthesia were compared to determine differences in the characteristics of emergence from these commonly used inhalant anesthetics.


METHODS
Prospective, randomized blinded clinical trial.


METHODS
A total of 96 Thoroughbred and 3 Standardbred racehorses admitted for elective distal forelimb arthroscopy.


METHODS
All horses were premedicated with intravenous xylazine, induced with guaifenesin and ketamine, and maintained on a large animal circle system fitted with an out of the circle, agent specific vaporizer. Recoveries were managed by a blinded scorer with a standardized protocol. A 10 category scoring system was used to assess each horse's overall attitude, purposeful activity, muscle coordination, strength and balance from the time of arrival in recovery to standing. Times to extubation, sternal recumbency and standing were recorded. Median recovery scores and mean times to extubation, sternal and standing were compared using the Mann-Whitney U test and student's t test, respectively.


RESULTS
The median score for horses recovering from halothane was lower (20.0; range, 10 to 57) than that for horses recovering from isoflurane (27.5; range, 10 to 55). Horses in the two groups were extubated at similar mean times (halothane, 11.3 +/- 5.5 and isoflurane, 9.5 +/- 5.2 minutes) but horses recovering from isoflurane achieved sternal recumbency (halothane, 37.7 +/- 12.1 and isoflurane, 24.7 +/- 8.8 minutes) and stood (halothane, 40.6 +/- 12.9 and isoflurane, 27.6 +/- 9.6 minutes) sooner than those recovering from halothane.


CONCLUSIONS
The recovery of horses from isoflurane anesthesia was more rapid but less composed than that from halothane.


CONCLUSIONS
The quality of recovery following isoflurane was worse than after halothane anesthesia using the criteria chosen for this study. However, the range of recovery scores was similar for both groups and all horses recovered without significant injury.
Donaldson
L L
LL
Marion duPont Scott Equine Medical Center, Virginia-Maryland Regional College of Veterinary Medicine, Leesburg 20177, USA.
Dunlop
G S
GS
Holland
M S
MS
Burton
B A
BA
D000762:Anesthesia Recovery Period; D000769:Anesthesia, Inhalation / Q000662:veterinary*; D000818:Animals; D001182:Arthroscopy / Q000662:veterinary; D004311:Double-Blind Method; D005260:Female; D005552:Forelimb; D006221:Halothane; D006736:Horses / Q000502:physiology* / Q000601:surgery; D007530:Isoflurane; D008297:Male; D011446:Prospective Studies
D007530:Isoflurane; D006221:Halothane