Anaesthesia for lambs undergoing spinal surgery: a case series

Abstract

SummarySix I-month-old lambs were anaesthetized for cervical spinal cord surgery. Anaesthesia was induced with intravenous midazolam (0.5 mg/kg) then halothane delivered by mask in an 02-N20 mixture. After endotracheal intubation, the lungs were ventilated mechanically and anaesthesia maintained with halothane and nitrous oxide. Buprenorphine and flunixin were given before and after surgery, and the wound margin was infiltrated with 0.5% bupivacaine solution. Neuromuscular block was produced with repeated injections of atracurium; neuromuscular transmission was restored with edrophonium. Lambs made a rapid recovery without obvious signs of discomfort, sedation, or weakness after operations lasting up to 156 min. Anaesthesia was induced in a seventh lamb using etomidate, which probably contributed to death during recovery from anaesthesia.

Clinical effects of isoflurane and sevoflurane in lambs

“…Clutton et al. (1998) evaluated the effect of halothane on similar recovery time points in another study involving lambs of a similar age undergoing surgical avulsion of spinal nerve roots.…”

“…It seems unlikely that the (possible excessive) depth of anaesthesia in the two groups was different. Clutton et al (1998) evaluated the effect of halothane on similar recovery time points in another study involving lambs of a similar age undergoing surgical avulsion of spinal nerve roots. Their results were similar to those obtained here despite the higher blood/gas solubility of halothane.…”

“…Problems with anaesthetizing neonate or paediatric subjects – such as lambs – arise from the animals’ high metabolic rate, high body water content, low body fat and poorly developed thermoregulatory reflexes (Ward 1984; Clutton et al. 1998).…”

“…Problems with anaesthetizing neonate or paediatric subjects -such as lambs -arise from the animals' high metabolic rate, high body water content, low body fat and poorly developed thermoregulatory reflexes (Ward 1984;Clutton et al 1998). Immature hepatic enzyme systems and an incomplete blood-brain barrier aggravate these problems (Jenkins 1986).…”

The perioperative care of lambs and ewes when the former undergo major experimental (scoliotic) surgery

“…P1-8 had a mean age of 4.6 (range 3-6) weeks and weight of 11 (9)(10)(11)(12)(13)(14)(15)(16)(17) kg. Operating conditions were adequate in all cases, but two lambs died.…”