Comparative study between intrathecal dexmedetomidine and fentanyl as adjuvants to bupivacaine in total hip arthroplasty surgeries

Abstract

Spinal anaesthesia is the most commonly used technique for lower limb surgeries as it is very economical and easy to administer. However, postoperative pain control is a major problem because spinal anaesthesia using only local anaesthetics is associated with relatively short duration of action, and thus early analgesic intervention is needed in the postoperative period (Elia et al., 2008).

A number of adjuvants, such as clonidine, midazolam and others have been studied to prolong the effect of spinal anaesthesia (Boussofara et al., 2006).

The addition of fentanyl to hyperbaric bupivacaine improves the quality of intraoperative and early postoperative analgesia. The addition of opioids to local anaesthetic solution has disadvantages, such as pruritus and respiratory depression. Dexmedetomidine, a new highly selective α2 agonist, is under evaluation as a neuraxial adjuvant as it provides stable hemodynamic conditions, good quality of intraoperative and prolonged postoperative analgesia with minimal side effects (Rajni et al., 2011).

The mechanism by which intrathecal α2 adrenoceptor agonists prolong the motor and sensory block of local anesthetics is not well known. They act by binding to presynaptic C-fibers and postsynaptic dorsal horn neurons. Their analgesic action is a result of depression of the release of C fiber transmitters and hyperpolarization of postsynaptic dorsal horn neurons. Local anaesthetic agents act by blocking sodium channels. The prolongation of effect may result from synergism between local anaesthetic and α2adrenoceptor agonist, while the prolongation of the motor block of spinal anaesthetics may result from the binding of α2 adrenoceptor agonists to motor neurons in the dorsal horn. Intrathecal α2 receptor agonists have been found to have antinociceptive action for both somatic and visceral pain (Rajni et al., 2011).

Fentanyl is a lipophilic μ-receptor agonist. In spinal anaesthesia, fentanyl exerts its effect by combining with opioid receptors in the dorsal horn of spinal cord and may have a supraspinal spread and action (Shukla et al., 2011).

All Patients underwent total hip arthroplasty surgeries were be assigned randomly in this prospective double blinded clinical trial by using computerized program to one of three parallel groups. Each group consisted of fifty patients.