Evaluation of xylazine and ketamine for total intravenous anesthesia in horses.
OBJECTIVE
To evaluate the use of xylazine and ketamine for total i.v. anesthesia in horses.


METHODS
8 horses.


METHODS
Anesthetic induction was performed on 4 occasions in each horse with xylazine (0.75 mg/kg, i.v.), guaifenesin (75 mg/kg, i.v.), and ketamine (2 mg/kg, i.v.). Intravenous infusions of xylazine and ketamine were then started by use of 1 of 6 treatments as follows for which 35, 90, 120, and 150 represent infusion dosages (microg/kg/min) and X and K represent xylazine and ketamine, respectively: X35 + K90 with 100% inspired oxygen (O2), X35 + K120-(O2), X35 + K150-(O2), X70 + K90-(O2), K150-(O2), and X35 + K120 with a 21% fraction of inspired oxygen (ie, air). Cardiopulmonary measurements were performed. Response to a noxious electrical stimulus was observed at 20, 40, and 60 minutes after induction. Times to achieve sternal recumbency and standing were recorded. Quality of sedation, induction, and recovery to sternal recumbency and standing were subjectively evaluated.


RESULTS
Heart rate and cardiac index were higher and total peripheral resistance lower in K150-(O2) and X35 + K120-air groups. The mean arterial pressure was highest in the X35 + K120-air group and lowest in the K150-(O2) group (125 +/- 6 vs 85 +/- 8 at 20 minutes, respectively). Mean Pa(O2) was lowest in the X35 + K120-air group. Times to sternal recumbency and standing were shortest for horses receiving K150-(O2) (23 +/- 6 minutes and 33 +/- 8 minutes, respectively) and longest for those receiving X70 + K90-(O2) (58 +/- 28 minutes and 69 +/- 27 minutes, respectively).


CONCLUSIONS
Infusions of xylazine and ketamine may be used with oxygen supplementation to maintain 60 minutes of anesthesia in healthy adult horses.
Mama
Khursheed R
KR
Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
Wagner
Ann E
AE
Steffey
Eugene P
EP
Kollias-Baker
Cynthia
C
Hellyer
Peter W
PW
Golden
Anne E
AE
Brevard
Lucien F
LF
D000771:Anesthesia, Intravenous / Q000379:methods / Q000662:veterinary*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005069:Evaluation Studies as Topic; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D007649:Ketamine / Q000494:pharmacology*; D013997:Time Factors; D014991:Xylazine / Q000494:pharmacology*
D018686:Anesthetics, Intravenous; D014991:Xylazine; D007649:Ketamine