Effect of Intravenous Dexmedetomidine on Bupivacaine for Spinal Anaesthesia

Since the discovery of spinal anaesthesia, it has been used widely with different additives in local anaesthetic drugs. Vasoconstrictors like phenylephrine, opioids, neostigmine and clonidine are some of the well known agents used to prolong the duration of block; whereas hypnotic, sedative and amnesic drugs are required to reduce the discomfort. However, they affect the ventilatory mechanisms and may lead to respiratory depression, with consequent hypercarbia and hypoxemia. A promising alternative to these drugs in anaesthesiology is the group of alpha-adrenergic agonist, which have excellent sedative and analgesic properties without respiratory depression. Clonidine an alpha 2 agonist has been used widely in the intrathecal route oral and intravenous routes to prolong the duration of spinal anagesia. dexmedetomidine, also an alpha 2 agonist, has eight times more affinity for alpha 2 receptors than does clonidine and has been used for pre-medication and as an adjunct to general anaesthesia. Various studies show that intravenous dexmedetomidine prolonged the sensory and motor blockade of bupivacaine spinal anaesthesia with good sedation and hemodynamic stability. The present study is designed to study the effect of intravenous dexmedetomidine with a loading dose of 1µg/kg and a maintenance dose of 0.5µg/kg on bupivacaine spinal anaesthesia with respect to duration of sensory and motor blockade, level of sedation and hemodynamic stability.