Combination of continuous intravenous infusion using a mixture of guaifenesin-ketamine-medetomidine and sevoflurane anesthesia in horses

The anesthetic and cardiovascular effects of a combination of continuous in travenous infusion using a mixture of 100 g/L guaifenesin-4 g/L ketamine-5 mg/L medetomidine (0.25 ml/kg/hr) and oxygen-sevoflurane (OS) anesthesia (G KM-OS anesthesia) in horses were evaluated. The right carotid artery of eac h of 12 horses was raised surgically into a subcutaneous position under GKM -OS anesthesia (n=6) or OS anesthesia (n=6). The end-tidal concentration of sevoflurane (EtSEV) required to maintain surgical anesthesia was around 1. 5% in GKM-OS and 3.0% in OS anesthesia. Mean arterial blood pressure (MABP) was maintained at around 80 mmHg under GKM-OS anesthesia, while infusion o f dobutamine (0.39 +/- 0.10 mu g/kg/min) was necessary to maintain MABP at 60 mmHg under OS anesthesia. The horses were able to stand at 36 +/- 26 min after cessation of GKM-OS anesthesia and at 48 +/- 19 minutes after OS ane sthesia. The cardiovascular effects were evaluated in 12 horses anesthetize d with GKM-OS anesthesia using 1.5% of EtSEV (n=6) or OS anesthesia using 3 .0% of EtSEV (n=6). During GKM-OS anesthesia, cardiac output and peripheral vascular resistance was maintained at about 70% of the baseline value befo re anesthesia, and MABP was maintained over 70 mmHg. During OS anesthesia, infusion of dobutamine (0.59 +/- 0.24 mu g/kg/min) was necessary to maintai n MABP at 70 mmHg. Infusion of dobutamine enabled to maintaine cardiac outp ut at about 80% of the baseline value; however, it induced the development of severe tachycardia in a horse anesthetized with sevoflurane. GKM-OS anes thesia may be useful for prolonged equine surgery because of its minimal ca rdiovascular effect and good recovery.