Dexmedetomidine as an Additive to Spinal Anaesthesia in Orthopaedic Patients Undergoing Lower Limb Surgeries: A Randomized Clinical Trial Comparing Two Different Doses of Dexmedetomidine.

Introduction: Use of dexmedetomidine as an additive to spinal anaesthesia is gaining popularity; but there seems to be no clear consensus on the ideal dose to be used. Because of dose related prolongation of duration of motor blockade along with increase in the incidence of side effects of dexmedetomidine namely hypotension and bradycardia, use of higher doses is not recommended.

Aim: To evaluate the efficacy of two different doses of dexmedetomidine (3 μg and 5 μg) given in combination with 0.5% hyperbaric bupivacaine via intrathecal route with regard to the quality of anaesthesia namely the time to attain highest sensory and motor blockade, side effects of dexmedetomidine and time to first rescue analgesia.

Materials And Methods: Sixty American Society of Anaesthesiologist (ASA) Grade I and II orthopaedic patients undergoing lower limb surgeries between the ages of 20-60 years and height >150 cm were randomly divided into two groups of 30 patients each: Group D3 to receive 3 μg of Inj. Dexmedetomidine (0.5 ml, reconstituted using normal saline) along with 12.5 mg (2.5 ml) of 0.5% hyperbaric bupivacaine and Group D5 to receive 5 μg of inj. Dexmedetomidine (0.5 ml, reconstituted using normal saline) along with 12.5 mg (2.5 ml) of 0.5% hyperbaric bupivacaine keeping the total volume of study drug constant in all 60 patients (3 ml). Data recordings were done for time to reach best sensory and motor block, intraoperative haemodynamic changes and time to first postoperative rescue analgesia. Statistical analysis was done using student's t-test and Chi-square test with p-value of <0.05 considered to be significant.

Results: The two groups analysed were similar in terms of demographic profile, time to reach highest sensory block (T10) dermatome, time to reach Bromage scale 4, time to surgical incision after spinal and the total duration of surgery (p>0.05). The change in haemodynamics was similar (p>0.05). A statistically significant difference (p<0.001) was observed in time to first rescue analgesia after skin closure with Group D3 having 206.47 minutes while in Group D5 the time was 271.33 minutes.

Conclusion: Used in a dose of 5 μg (in 0.5 ml volume) as an additive in spinal anaesthesia maximal beneficial effect of dexmedetomidine can be obtained without any side effects.