EXPERIENCES WITH MORPHINE INJECTED INTO THE SUBARACHNOID SPACE IN SHEEP

The effects of morphine (M), 0.1 mg/kg, administered into the lumbosac ral subarachnoid space of sheep used for experimental stifle surgery, were investigated. In a pilot study, preservative-free morphine was ad ministered to three sheep, morphine containing preservatives to two sh eep, and saline (S) to one sheep. After recovery from anesthesia, all five sheep administered M displayed rear limb weakness. One sheep, whi ch had received morphine containing preservatives, also licked and che wed incessantly at its flank and hindquarters during recovery. A group of 24 sheep was used to study the effects of morphine containing pres ervatives, injected intrathecally, on recovery from general anesthesia and hindlimb orthopedic surgery. Eight sheep received M, eight sheep received S, and eight sheep had a needle placed in the subarachnoid sp ace without any injection (N). Times from end of anesthesia to standin g varied greatly and did not differ significantly among groups (P = .7 3), with M sheep averaging 119 minutes; S sheep, 87 minutes; and N she ep, 83 minutes. One sheep administered M licked and chewed at its hind quarters during recovery. Another group of 24 sheep was used to study the effects of morphine containing preservatives, injected intrathecal ly, on postoperative lameness. Treatments were as described previously . Sheep were videotaped intermittently for 36 hours after surgery, and each sheep was scored as follows: 0 = not lame; 1 = slightly lame; an d 2 = very lame. The average lameness scores, which did not differ sig nificantly among groups (P = .21), were: M sheep, 1.07; S sheep, 0.81; and N sheep, 0.68. One sheep administered M displayed extensor spasms of the hindlimbs, and could not stand until several hours after surge ry. We conclude that subarachnoid morphine at the dosage used produces no apparent benefit in sheep which have had stifle surgery, and in fa ct may cause detrimental side effects, such as hindlimb weakness, and pruritis or irritation of the hindquarters. (C)Copyright 1996 by The A merican College of Veterinary Surgeons