The bispectral index during recovery from halothane and sevoflurane anaesthesia in horses.
OBJECTIVE
To record the bispectral index (BIS) when horses moved during either halothane or sevoflurane anaesthesia and when they made volitional movements during recovery from these anaesthetics.


METHODS
Randomized prospective clinical study.


METHODS
Twenty-five client-owned horses undergoing surgery aged 8.8 (+/- 5.3; 1-19) years (mean +/- SD; range).


METHODS
Baseline BIS values were recorded before pre-anaesthetic medication (BIS(B)) and during anaesthesia (BIS(A)) maintained with halothane (group H; n = 12) or sevoflurane (group S; n =13) at approximately 0.8-0.9 x minimum alveolar concentrations (MAC). Bispectral indices were recorded during the surgery when unexpected movement occurred (BIS(MA)), during recovery when the first movement convincingly associated with consciousness was observed (BIS(M1)) and once sternal recumbency was achieved (BIS(ST)).


RESULTS
No significant difference in BIS(M1) was found between halothane- (85 +/- 7; 75-93) and sevoflurane- (87 +/- 10; 70-98) anaesthetized horses although BIS(A) was significantly (p = 0.0002) lower in group S (62 +/- 7; 53-72) than group H (74 +/- 7; 60-84). Differences between BIS(M1) and BIS(A) were significant in sevoflurane (p = 0.00001) and halothane recipients (p = 0.002) but were greater in group S (25 +/- 9; 4-38) compared with group H (12 +/- 10; -9-25). In six of eight horses, BIS(MA) values ranged between those recorded during anaesthesia and at first movement.


CONCLUSIONS
Bispectral indices appear to approximate levels of unconsciousness, suggesting that monitoring the BIS may assist equine anaesthesia. However, it does not predict intra-operative movement.
Belda
Eliseo
E
Departamento de Medicina y Cirugía Animal, Hospital Clínico Veterinario, Universidad de Murcia, Murcia, Spain.
Beldao
Eliseo
E
Blissitt
Karen J
KJ
Duncan
Juliet C
JC
Laredo
Francisco G
FG
Escobar Gil de Montes
Mayte
M
Clutton
R Eddie
RE
D000762:Anesthesia Recovery Period; D000769:Anesthesia, Inhalation / Q000662:veterinary*; D018685:Anesthetics, Inhalation; D000818:Animals; D056805:Consciousness Monitors / Q000662:veterinary*; D005260:Female; D006221:Halothane; D006736:Horses / Q000502:physiology; D007430:Intraoperative Care / Q000662:veterinary; D008297:Male; D008738:Methyl Ethers; D011229:Preanesthetic Medication / Q000662:veterinary; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D006221:Halothane