Changes in micturition volume thresholds in conscious dogs following spinal opiate administration
Abstract
Micturition difficulties appear as an often-reported side effect of the clinical use of opiates for spinal analgesia. Only a few experimental studies have focused specifically on this problem, especially in an unanesthetized animal model where chronic pharmacological studies can be carried out. The changes in micturition volume thresholds that occurred following spinal intrathecal injections of 1 mg of morphine sulphate were measured in 11 conscious dogs and compared with threshold changes produced in these same dogs by i.v. injections of various doses of morphine sulphate and by intrathecal and i.v. injections of naloxone HCl. In all cases, intrathecal or systemic morphine at doses of 1.0 mg or greater significantly (P less than 0.05) increased the bladder volume at which micturition took place. Naloxone, injected intrathecally to reverse the effects of intrathecal morphine, significantly reduced the micturition volume threshold, in most cases to below control volumes. A 400 microgram dose of naloxone, injected intrathecally without prior injection of morphine, significantly lowered the volume threshold in 9 dogs, even though two of these dogs had elevated thresholds following naloxone injection. The reduction in volume thresh...Continue Reading
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Effects of fentanyl, naloxone, and clonidine on hemodynamics and plasma catecholamine levels in dogs
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