Intravenous anaesthesia in goats: A review

Abstract

Intravenous anaesthesia is gradually becoming popular in veterinary practice. Traditionally, general anaesthesia is induced with intravenous drugs and then maintained with inhalation agents. Inhalation anaesthetic agents cause more significant dose-dependent cardiorespiratory depression than intravenous anaesthetic drugs, creating a need to use less of the inhalation anaesthetic agents for maintenance of general anaesthesia by supplementing with intravenous anaesthesia drugs. Better still, if anaesthesia is maintained completely with intravenous anaesthetic drugs, autonomic functions remain more stable intra-operatively. Patient recovery from anaesthesia is smoother and there is less pollution of the working environment than happens with inhalation anaesthetic agents. Recently, a number of drugs with profiles (pharmacokinetic and pharmacodynamic) suitable for prolonged intravenous anaesthesia have been studied, mostly in humans and, to a certain extent, in dogs and horses. There is currently very little scientific information on total intravenous anaesthesia in goats, although, in the past few years, some scholarly scientific articles on drugs suitable for partial intravenous anaesthesia in goats have been published. This review article explored the information available on drugs that have been assessed for partial intravenous anaesthesia in goats, with the aim of promoting incorporation of these drugs into total intravenous anaesthesia protocols in clinical practice. That way, balanced anaesthesia, a technique in which drugs are included in anaesthetic protocols for specific desired effects (hypnosis, analgesia, muscle relaxation, autonomic stabilisation) may be utilised in improving the welfare of goats undergoing general anaesthesia.

The effects of midazolam and butorphanol, administered alone or combined, on the dose and quality of anaesthetic induction with alfaxalone in goats

“…Bloat is known to occur in laterally recumbent goats despite prior starvation (Dzikiti 2013;Galatos 2011;Taylor 1991). Brisk palpebral movements and nystagmus have been reported in horses (Goodwin et al 2011).…”

“…In small ruminants, the commonly used sedatives before induction of general anaesthesia include: α 2 -adrenoceptor agonists such as xylazine; phenothiazines such as acepromazine; benzodiazepines such as diazepam and midazolam; and opioids such as butorphanol (Riebold 2007). In goats, induction of general anaesthesia can be achieved by administration of ketamine, propofol or thiopentone (Dzikiti 2013;Prassinos et al 2005). Recently, alfaxalone has been shown to be an alternative induction agent in: dogs (Ferré et al 2006;Muir et al 2008;Suarez et al 2012); cats ; sheep ); ponies (Klöppel & Leece 2011;Leece et al 2009); and horses (Goodwin et al 2011).…”

Anestesia geral inalatória ou total intravenosa associada à anestesia subaracnoidea, em ovinos

“…Sabe-se que a redução da pressão arterial causada pelo propofol se deve à redução do débito cardíaco, do volume sistólico e, principalmente, a um decréscimo da resistência vascular sistêmica por inibição de mecanismos vasopressores medulares, levando à vasodilatação (Dzikiti, 2013).…”

“…A cetamina pode promover efeitos diretos e indiretos por meio do aumento do tônus simpático, aumento do DC, aumento da PAM, da estimulação direta do sistema nervoso central (SNC), do efeito inotrópico positivo sobre o miocárdio e do efeito no bloqueio da recaptação de catecolaminas (Dzikiti, 2013). Embora este protocolo de indução seja amplamente utilizado e até mesmo indicado para pacientes críticos por desencadear mínimos efeitos cardiorrespiratórios (Abrahamsen, 2013), observou-se a ocorrência de hipercapnia no momento pós-indução, com níveis de PaCO 2 maiores que 50mmHg em cinco dos sete animais, corroborando os achados de Ismail et al (2010) em ovinos anestesiados com 0,1mg.kg -1 de xilazina, 0,25mg.kg -1 de diazepam e 5mg.kg -1 de cetamina IV.…”

“…No estudo em questão, após início da manutenção com isoflurano, os valores de FC e pressões arteriais mantiveram-se estáveis. Dzikiti et al (2013), em estudo com a espécie caprina, e Mattos-Júnior (2012), em estudo com a espécie ovina, empregaram o isoflurano de forma isolada na dose de 1 CAM e relataram estabilidade cardiovascular, referente a FC, pressões arteriais, PVC e DC, sem alterações significativas desses parâmetros.…”