Effect of high volume epidural morphine, ketamine and butorphanol on halothane minimum alveolar concentration in ponies

Abstract

Summary This study determined the effects of epidurally administered morphine, ketamine and butorphanol on halothane minimum alveolar concentration (MAC) in ponies. Seven ponies were anaesthetised with thiopentone and succinylcholine, intubated and anaesthesia maintained with halothane. Ventilation was controlled and blood pressure was maintained within normal limits. Following the determination of baseline halothane MAC for the pelvic and thoracic limbs the ponies were given morphine (0.1 mg/kg bwt), ketamine (0.8 or 1.2 mg/kg bwt), butorphanol (0.05 mg/kg bwt) or saline, epidurally, to a final volume of 0.15 ml/kg bwt. The halothane MAC for the pelvic and thoracic limbs was redetermined following each treatment. The baseline halothane MAC for the control group was mean ± s.e. 0.85 ± 0.02% and no significant change occurred after saline administration. Morphine significantly (P = 0.002) decreased MAC from, mean ± s.e. 0.90 ± 0.05% to 0.77 ± 0.06% in the pelvic limb. Ketamine significantly decreased MAC in the pelvic limb from mean ± s.e. 0.86 ± 0.06% to 0.71 ± 0.04%, and 0.82 ± 0.03% to 0.71 ± 0.02%, for the low (P = 0.008) and high dose (P = 0.001), respectively. No significant change in MAC occurred following butorphanol. No treatment reduced halothane MAC for the thoracic limb.

Anesthesia of the critically ill equine patient

“…Epidural administration of ketamine and morphine to horses provides analgesia and decreases inhalant anesthetic requirements (see Table 1) [110]. Preoperative administration of these agents may be particularly useful in critically ill patients to reduce the risk of intraoperative hypotension (inhalant-sparing effect) and to provide preemptive and postoperative analgesia [110][111][112].…”

Changes in minimal alveolar concentration of isoflurane following treatment with medetomidine and tiletamine/zolazepam, epidural morphine or systemic buprenorphine in pigs

“…Reduction of isoflurane MAC by epidural morphine has been observed in other studies. For example, epidural morphine reduced halothane MAC by at least 33% in dogs (Valverde et al 1989) and 14% in ponies (Doherty et al 1997). In humans, it is reported that epidural morphine reduces the halothane MAC by 28% (Schwieger et al 1992) and isoflurane MAC by 14% (Kashyap et al 2003).…”

“…Furthermore, these opioids have been reported to decrease minimum alveolar concentration (MAC) of the volatile anaesthetic when given preoperatively in many species (Valverde et al 1989, Steffey et al 1994, Doherty et al 2002. For instance, epidural morphine has been reported to reduce MAC of halothane in dogs (Valverde et al 1989), ponies (Doherty et al 1997) and the requirement of isoflurane in pigs (Malavasi et al 2006). Treatment with IM buprenorphine has been reported to reduce the MAC of halothane in humans (Inagaki & Kuzukawa 1997).…”

Injeção epidural preventiva de xilazina ou amitraz, em eqüinos: efeito antinociceptivo

“…O uso epidural de fármacos antinociceptivos possibilita intervenções urogenitais em eqüinos em estação (SKARDA, 1991;SALMON et al, 1995;DOHERTY et al, 1997), sendo que os anestésicos locais são utilizados, mas geram bloqueio motor e simpático além do sensorial (DE ROSSI et al 2005). Na busca de mais seletividade por fibras sensoriais, surgem os agonistas α 2 (LE BLANC & CARON, 1990;LE BLANC & EBERHART, 1990;GRUBB et al, 1992).…”