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

Abstract

ABSTRACT. The anesthetic and cardiopulmonary effects of midazolam, ketamine and medetomidine for total intravenous anesthesia (MKM-TIVA) were evaluated in 14 horses. Horses were administered medetomidine 5 µg/kg intravenously as pre-anesthetic medication and anesthetized with an intravenous injection of ketamine 2.5 mg/kg and midazolam 0.04 mg/kg followed by the infusion of MKMdrug combination (midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.1 mg/ml). Nine stallions (3 thoroughbred and 6 draft horses) were castrated during infusion of MKM-drug combination. The average duration of anesthesia was 38 ± 8 min and infusion rate of MKM-drug combination was 0.091 ± 0.021 ml/kg/hr. Time to standing after discontinuing MKM-TIVA was 33 ± 13 min. The quality of recovery from anesthesia was satisfactory in 3 horses and good in 6 horses. An additional 5 healthy thoroughbred horses were anesthetized with MKM-TIVA in order to assess cardiopulmonary effects. These 5 horses were anesthetized for 60 min and administered MKM-drug combination at 0.1 ml/kg/hr. Cardiac output and cardiac index decreased to 70-80%, stroke volume increased to 110% and systemic vascular resistance increased to 130% of baseline value. The partial pressure of arterial blood carbon dioxide was maintained at approximately 50 mmHg while the arterial partial pressure of oxygen pressure decreased to 50-60 mmHg. MKM-TIVA provides clinically acceptable general anesthesia with mild cardiopulmonary depression in horses. Inspired air should be supplemented with oxygen to prevent hypoxemia during MKM-TIVA. KEY WORDS: equine, ketamine, medetomidine, midazolam, total intravenous anesthesia.

Evaluation of intranasal oxygen supplementation in mules anesthetized with the combination of ketamine, butorphanol, and guaifenesin

“…Therefore, hypoxemia was observed in horses (Yamashita et al, 2007), and in donkeys (Molinaro et al, 2014), and in both studies, the animals were anesthetized with total intravenous anesthesia and breathed room air.…”

“…Hypoventilation and decreased pulmonary blood perfusion are among the possible causes of decreased PaO 2 during anesthesia (Yamashita et al, 2007). The first is because most anesthetic drugs decrease the respiration rate and/or tidal volume, resulting in CO 2 accumulation in the alveolus and, consequently decreased alveolar O 2 concentration, thereby decreasing the alveolar oxygen gradient for blood, producing hypoxemia and hypercapnia (Robinson, 2009).…”

Evaluation of the effects of intravenous anaesthesia using a combination of ketamine - medetomidine in Sahel goats

“…Current veterinary anaesthesia in large animals concentrates on the use of ketamine, guaifenesin, alpha 2 agonists, barbiturates and chloral hydrate (Yamashita et al, 2007). Advantages of intravenous anaesthesia include rapid and smooth induction of anaesthesia, little equipment requirements (needles, syringes, catheters), easy administration of drugs and achievement of balanced anaesthesia (Yamashita et al, 2007).…”

“…Advantages of intravenous anaesthesia include rapid and smooth induction of anaesthesia, little equipment requirements (needles, syringes, catheters), easy administration of drugs and achievement of balanced anaesthesia (Yamashita et al, 2007). Intravenous anaesthesia is indicated mostly for major surgery such as orthopaedic surgeries in animals including limb amputation, management, arthroscopy, obstetrical procedures like ceasarian section and orchidectomy in large animals (Hall et al, 2001;Umar et al, 2006;Kilic, 2008).…”

“…Medetomidine is an alpha 2 agonist which produces sedation, analgesia and muscle relaxation in veterinary practice. Medetomidine is an effective sedative in small animal practice (Sinclair, 2003) and horses (Umar et al, 2006;Yamashita et al, 2007). Indeed, ketamine and medetomidine combinations have been found to provide excellent immobilization and muscle relaxation in a wide range of species of animals while the ability to reverse the sedative effect of alpha 2 adrenoreceptor agonist has proved to be particularly useful (Hall et al, 2001).…”