Comparison of Fentanyl and Dexmedetomidine as Intrathecal Adjuvants to Spinal Anaesthesia for Abdominal Hysterectomy

Spinal anaesthesia, although advantageous for conducting abdominal hysterectomy, is not the first choice amongst surgeons for fear of intra-operative visceral pain. Intrathecal adjuvants may improve quality of spinal anaesthesia. This study aims to compare efficacy of intrathecal Fentanyl and Dexmedetomidine to reduce visceral pain during abdominal hysterectomy performed under spinal anaesthesia.

Sixty women undergoing abdominal hysterectomy for benign indications were randomly assigned to two equal groups in a double-blind fashion. Fentanyl 25 micrograms in group A or Dexmedetomidine 10 micrograms in group B was co-administered with hyperbaric Bupivacaine 15 milligrams for spinal anesthesia. Surgery through Pfannenstiel incision proceeded once sensory block reached eighth thoracic dermatome. The intra-operative visceral pain was assessed using a five-point scale: none, mild, intermediate, severe, and failed spinal anaesthesia. Duration of analgesia and peri-operative events were studied for 24 hours. Chi-square test, Mann-Whitney U-test and Student's t-test were used for analysis. Level of significance used was P<0.05.

Fifty eight participants completed the study. Demographic variables and sensory block were similar between groups. General anaesthesia was not required in both groups. Significantly greater number of patients in group A required medications for visceral pain with Relative Risk of 2.8 (1.16-6.7). Pruritus and shivering occurred significantly higher in group A. Hypotension was significantly higher in group B. Post-operatively, group B patients showed a significantly longer duration of analgesia.

Dexmedetomidine is better than Fentanyl as an intrathecal adjuvant to spinal anaesthesia in minimizing visceral pain during abdominal hysterectomy and in prolonging post-operative analgesia.