Cardiovascular and respiratory effects of epidural lidocaine and morphine administered in dogs anaesthetized with halothane

Extradural co-administration of opioids and local anaesthetics is a popular method for control of pain [3, 5, 18]. Spinal and epidural administration of opioids produce a profound and long lasting segmental analgesia, which is not associated with sensory, sympathetic, or motor blockade [2, 4]. The side effects of epidural opioids in men are dose-dependent and may include pruritus, nausea, respiratory depression and urinary retention [3, 15]. Respiratory depression is the most serious complication associated with the administration of epidural opioids [15]. The dose of epidural morphine, most commonly used in small animals is 0.1 mg/kg [8, 10, 20]. Unlike humans, this dose does not result in any serious adverse side effects in dogs [21]. Epidural local anesthetics may cause hypotention secondary to sympathetic blockade. [1, 18]. The appropriate combination of an opioid and a local anesthetic provides a better analgesia and simultaneously minimizes the side effects associated with either drug, administered alone.