Prolongation of anesthesia with xylazine, ketamine, and guaifenesin in horses: 64 cases (1986-1989)

• Published in: Journal of the American Veterinary Medical Association Vol. 197; no. 12; p. 1646
• Main Authors: McCarty, J.E. (The University of Georgia, Athens, GA), Trim, C.M, Ferguson, D
• Format: Journal Article
• Language: English
• Published: United States 15.12.1990
• Subjects: ADVERSE EFFECTS; ANAESTHESIA; ANESTESIA; Anesthesia - veterinary; ANESTHESIE; Animals; Blood Pressure - drug effects; Butorphanol; CABALLOS; CHEVAL; DURACION; DURATION; DUREE; EFECTOS SECUNDARIOS; EFFET SECONDAIRE; Female; Guaifenesin; Heart Rate - drug effects; HORSES; Horses - physiology; KETAMINA; KETAMINE; Ketamine - pharmacokinetics; Male; MEDICAMENTOS APARATO RESPIRATORIO; MODIFICATEUR SYSTEME RESPIRATOIRE; Preanesthetic Medication - veterinary; Respiration - drug effects; RESPIRATORY SYSTEM AGENTS; Retrospective Studies; SIDE EFFECTS; Time Factors; XILAZINA; XYLASINE; XYLAZINE
• ISSN: 0003-1488; 1943-569X
• DOI: 10.2460/javma.1990.197.12.1646

On 74 occasions, 54 horses and 6 foals were anesthetized with xylazine and ketamine or xylazine, guaifenesin, and ketamine, with or without butorphanol. On 64 occasions, anesthesia was prolonged for up to 70 minutes (34 +/- 15 min) by administration of 1 to 9 supplemental IV injections of xylazine and ketamine at approximately a third the initial dosage. All horses except 5 were positioned in lateral recumbency, and oxygen was insufflated. In adult horses, the time from induction of anesthesia to the first supplemental xylazine and ketamine injection was 13 +/- 4 minutes and the time between supplemental injections was 12.1 +/- 3.7 minutes. These results were consistent with predicted plasma ketamine concentration calculated from previously published pharmacokinetic data for ketamine in horses. Respiratory and heart rates and coccygeal artery pressure remained consistent for the duration of anesthesia. The average interval between the last injection of ketamine and assumption of sternal position was approximately 30 minutes, and was the same regardless of the number of supplemental injections. The time to standing was significantly longer (P less than 0.05) in horses given 2 supplemental injections, compared with those not given any or only given 1, but was not longer in horses given 3 supplemental injections. Recovery was considered unsatisfactory in 5 horses, but did not appear to be related to prolongation of anesthesia.