Comparison of ketamine and S(+)-ketamine, with romifidine and diazepam, for total intravenous anesthesia in horses.
OBJECTIVE
To compare the quality of induction and recovery, degree of muscle relaxation, clinically apparent potency and cardiopulmonary effects of racemic ketamine or S(+)-ketamine when used for total intravenous anesthesia in horses.


METHODS
Prospective randomized clinical trial


METHODS
Sixteen healthy stallions (323 +/- 99 kg), with a mean age of 6.2 years, undergoing castration.


METHODS
Horses were pre-medicated with romifidine IV, 15 minutes before induction of anesthesia. Each animal was then randomly allocated to receive either diazepam and ketamine (DK) or diazepam and S(+)-ketamine (DKS) at similar doses to induce anesthesia. For maintenance of anesthesia, 1/4 of the initial bolus of ketamine alone or S(+)-ketamine alone was administered, as required. Heart rate (HR), respiratory rate (RR) and systolic blood pressure were measured before and at 10-minute intervals during recumbency. Time from induction to lateral recumbency, time from induction to first additional dose, time from last additional dose to return to sternal posture and time from last additional dose to standing were recorded, and a subjective evaluation of quality of induction, endotracheal intubation, muscle relaxation and quality of recovery was recorded.


RESULTS
The quality of the induction and duration of anesthesia were similar in both groups. HR, RR and systolic blood pressure were not significantly different between groups. Although some animals which received DKS showed some minor excitatory effects (25% of them) during the induction of anesthesia, these animals received 32% fewer doses for the maintenance of anesthesia and the recovery scores were better.


CONCLUSIONS
S(+)-ketamine showed some advantages over racemic ketamine, such as less anesthetic agent being required and better overall recovery from anesthesia. Further studies are needed to obtain the optimum induction dose for the S(+)-ketamine.
Rossetti
Renata B
RB
Departamento de Cirurgia, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil. rerossetti@uol.com.br
Gaido Cortopassi
Silvia R
SR
Intelizano
Tatiana
T
de Lima Machado
Thaís S
TS
Ferreira da Cruz
Rodrigo S
RS
D000768:Anesthesia, General / Q000662:veterinary*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003975:Diazepam / Q000008:administration & dosage / Q000494:pharmacology; D004311:Double-Blind Method; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology* / Q000601:surgery; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology; D007262:Infusions, Intravenous / Q000662:veterinary; D007649:Ketamine / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D009919:Orchiectomy / Q000662:veterinary; D011446:Prospective Studies; D012119:Respiration / Q000187:drug effects; D016896:Treatment Outcome
D018686:Anesthetics, Intravenous; D007093:Imidazoles; D007649:Ketamine; C076257:romifidine; D003975:Diazepam