Effects of the morphine-lidocaine-ketamine combination on cardiopulmonary function and isoflurane sparing in sheep

Abstract

The aims of this study were to evaluate the isoflurane sparing and clinical effects of a constant rate infusion of morphine – lidocaine – ketamine (MLK) in healthy sheep undergoing experimental gastrointestinal surgery. Twelve adult female sheep (Texel breed) were used, weighing 36.5 ± 8.1 kg. The sheep were anesthetized for the implantation of duodenal cannulas. The sheep were premedicated with 0.3 mg kg-1 intramuscular (IM) morphine and 20 ?g kg-1 intravenous (IV) detomidine. After premedication, anesthesia was induced using 5 mg kg-1 ketamine and 0.5 mg kg-1 diazepam IV and maintained using isoflurane in 100% oxygen. After the induction of anesthesia, the animals were allocated into two groups (each n=6); the GMLK (MLK group – 10 mg morphine, 150 mg lidocaine, 30 mg de ketamine were added in 500 mL saline) received a 10 mL kg-1h-1 MLK infusion during the maintenance of anesthesia, and GCON (control group) received 10 mL kg-1h-1 of 0.9% sodium chloride. The animals were mechanically ventilated. Cardiopulmonary variables and end-tidal isoflurane concentration (FE´Iso) were measured at baseline (immediately before the surgery) and 15, 30 and 45 minutes after initiation of surgery. In GMLK, there was a decrease in the FE´Iso at 15, 30 and 45 minutes, a reduction of up to 75.6% during the surgery. The HR was lower in GMLK compared with GCON at 30 minutes, and the MAP was at during baseline in GCON compared with GMLK. The standing time was less in GMLK than in GCON. The use of intravenous MLK was demonstrated to offer great efficiency as part of a balanced anesthesia protocol in sheep, with a 75.6% reduction in the need for isoflurane, providing stability of the cardiovascular parameters and blood gases with a shortened recovery period.

Keywords

• Sheep; Morphine; Lidocaine; Ketamine; Isoflurane