Lumbosacral epidural magnesium prolongs ketamine analgesia in conscious sheep.

PURPOSE To determine the analgesic, motor, sedation and systemic effects of lumbosacral epidural magnesium sulphate added to ketamine in the sheep. METHODS Six healthy adult male mixed-breed sheep; weighing 43 ± 5 kg and aged 20-36 months. Each sheep underwent three treatments, at least 2 weeks apart, via epidural injection: (1) ketamine (KE; 2.5 mg/kg), (2) magnesium sulphate (MG; 100 mg), and (3) KE + MG (KEMG; 2.5 mg/kg + 100 mg, respectively). Epidural injections were administered through the lumbosacral space. Analgesia, motor block, sedation, cardiovascular effects, respiratory rate, skin temperature, and rectal temperature were evaluated before (baseline) and after drug administration as needed. RESULTS The duration of analgesia with the lumbosacral epidural KEMG combination was 115 ± 17 min (mean ± SD), that is, more than twice that obtained with KE (41 ± 7 min) or MG (29 ± 5 min) alone. KE and KEMG used in this experiment induced severe ataxia. The heart rate and arterial blood pressures changes were no statistical difference in these clinically health sheep. CONCLUSION The dose of magnesium sulphate to lumbosacral epidural ketamine in sheep is feasible, and can be used in procedures analgesics in sheep.