Cardiorespiratory, endocrine and metabolic changes in ponies undergoing intravenous or inhalation anaesthesia

Abstract

Six Welsh gelding ponies (weight 246 +/- 6 kg) were premedicated with 0.03 mg/kg of acepromazine intravenously (i.v.) followed by 0.02 mg/kg of detomidine i.v. Anaesthesia was induced with 2 mg/kg of ketamine i.v. Ponies were intubated and lay in left lateral recumbency. On one occasion anaesthesia was maintained for 2 h using 1.2% halothane in oxygen. The same group of ponies were anaesthetized 1 month later using the same induction regime and anaesthesia was maintained with a combination of detomidine, ketamine and guaiphenesin, while the ponies breathed oxygen-enriched air. Electrocardiogram, heart rate, mean arterial blood pressure, cardiac output, respiratory rate, blood gases, temperature, haematocrit, glucose, lactate and cortisol were measured and cardiac index and systemic vascular resistance were calculated in both groups. Beta-endorphin, met-enkephalin, dynorphin, arginine vasopressin (AVP), adrenocorticotrophic hormone (ACTH) and catecholamines were measured in the halothane anaesthesia group only and 11-deoxycortisol during total intravenous anaesthesia (TIVA) only. Cardiorespiratory depression was more marked during halothane anaesthesia. Hyperglycaemia developed in both groups. Lactate and AVP increased during halothane anaesthesia. Cortisol increased during halothane and decreased during TIVA. There were no changes in the other hormones during anaesthesia. Recovery was smooth in both groups. TIVA produced better cardiorespiratory performance and suppressed the endocrine stress response observed during halothane anaesthesia.

Adrenocortical Insufficiency in Horses and Foals

“…However, if ACTH concentrations increase but 11-deoxycortisol remains low, primary adrenocortical dysfunction is implied. Measurement of 11-deoxycortisol is described in the horse,31 but commercial assays are not readily available in all clinical settings, and many assays require a cumbersome extraction step. Furthermore, while intravenous infusions of metyrapone have been described in horses,32 oral metyrapone has not been used for HPA axis function assessment in ill horses to date.…”

Anesthesia of the critically ill equine patient

“…Several TIVA protocols have been reported to provide adequate analgesia with preservation of cardiovascular function and arterial oxygenation [47,52,[58][59][60][61]. Two studies demonstrated that the TIVA protocol used provided superior arterial blood pressure values compared with halothane [62,63]. These TIVA studies were performed on healthy individuals, and supplemental oxygen, with or without controlled ventilation, was provided.…”

Comparison of the effect of two Ringer-Lactate-Solutions on electrolyte-, lactate- and acid-base-status in horses during balanced long-term-anaesthesia with Isoflurane and Medetomidine

“…Gesunde anästhesierte Pferden zeigen bei Einleitung Laktatkonzentrationen von 1,4 mmol/l, welche nach 2,5 Stunden Allgemeinanästhesie auf 2,1 mmol/l ansteigen (Boscan et al 2007 (Luna et al 1996), anaerober Metabolismus durch Hypoxie, erniedrigter Laktatstoffwechsel sowie ein Überschuss von Laktatadministration durch die Verabreichung von 10 ml/kg/h RL über die Anästhesiezeit von 2,5 Stunden (Boscan et al 2007). Bei Hunden mit Lymphom wurde gezeigt, dass nach Verabreichung von RL ein transienter Laktatanstieg ausgelöst wird, der sich zwei Stunden nach Infusionsende normalisiert (Vail et al 1990).…”