Anesthetic and Cardiovascular Effects of Balanced Anesthesia Using Constant Rate Infusion of Midazolam-Ketamine-Medetomidine with Inhalation of Oxygen-Sevoflurane (MKM-OS Anesthesia) in Horses

Abstract

ABSTRACT. The anesthetic sparring and cardiovascular effects produced by midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.05 mg/ml (0.025 ml/kg/hr) drug infusion during sevoflurane in oxygen (MKM-OS) anesthesia was determined in healthy horses. The anesthetic sparring effects of MKM-OS were assessed in 6 healthy thoroughbred horses in which the right carotid artery was surgically relocated to a subcutaneous position. All horses were intubated and ventilated with oxygen using intermittent positive pressure ventilation (IPPV). The end-tidal concentration of sevoflurane (ET SEV ) required to maintain surgical anesthesia was approximately 1.7%. Heart rate and mean arterial blood pressure averaged 23-41 beats/min and 70-112 mmHg, respectively. All horses stood between 23-44 min after the cessation of all anesthetic drugs. The cardiovascular effects of MKM-OS anesthesia were evaluated in 5 healthy thoroughbred horses ventilated using IPPV. Anesthesia was maintained for 4 hr at an ET SEV of 1.7%. Each horse was studied during left lateral (LR) and dorsal recumbency (DR) with a minimum interval between evaluations of 1 month. Cardiac output and cardiac index were maintained between 70-80% of baseline values during LR and 65-70% of baseline values during DR. Stroke volume was maintained between 75-85% of baseline values during LR and 60-70% of baseline values during DR. Systemic vascular resistance was not different from baseline values regardless of position. MKM-OS anesthesia may be useful for prolonged equine surgery because of its minimal cardiovascular depression in both of lateral and dorsal recumbency.

Anesthetic and Cardiopulmonary Effects of Total Intravenous Anesthesia Using a Midazolam, Ketamine and Medetomidine Drug Combination in Horses

“…Taylor et al [22] reported that surgical anesthesia for castration could be maintained in ponies using a mixture of guaifenesin (100 mg/ml), ketamine (4 mg/ml) and detomidine (40 µg/ml) at an infusion rate of 0.8 ml/kg/hr (guaifenesin 80 mg/kg/hr, ketamine 3.2 mg/kg/hr and detomidine 32 µg/kg/hr). Recently, Kushiro et al [9] reported that midazolam 0.02 mg/kg/hr could be substituted for guaifenesin 25 mg/kg/hr in horses. In this study, surgical anesthesia for castration was achieved by infusing MKM-drug combination at 0.091 ± 0.021 ml/kg/hr.…”

“…The central muscular relaxation produced by guaifenesin can be replaced by benzodiazepines, including diazepam [4], climazolam [1] and midazolam [5,9,12]. Midazolam may be one of the most useful injectable benzodiazepine because it is water-soluble.…”

Clinical assessment of anesthesia with isoflurane and medetomidine in 300 equidae

“…Different authors showed a reduction of the minimal alveolar concentration (MAC) of various inhalational agents by administration of a constant rate infusion (CRI) of medetomidine, ketamine or a combination of different drugs (Bettschart-Wolfensberger et al 2001, Muir and Sams 1992, Neges et al 2003. Some regimes were investigated in experimental animals (Bettschart-Wolfensberger et al 2001, Dzikiti et al 2003, Kushiro et al 2005, Muir and Sams 1992, some in clinical studies with caseloads of 12 to 40 horses (Spadavecchia et al 2002, Yamashita et al 2002. One study including 69 clinical patients compared isoflurane-lidocaine versus isoflurane-medetomidine balanced anesthesia in a randomized, prospective, blinded manner (Ringer et al 2005).…”

Chelonia (Tortoises, Turtles, and Terrapins)

“…For this reason, the use of combinations of small doses of multiple drugs has become popular in anesthesia. This anesthetic technique is referred to as balanced anesthesia and has been shown to be superior to single-agent anesthesia in humans and many veterinary species (Kushiro et al 2005;Sanders et al 2008). The explanation of its success is the use of small doses summates the advantages, but not the disadvantages, of the individual components of the mixture.…”