Abstract
Background: Anesthesia for lower limb surgeries can be administered locally, regionally (spinal or epidural), or generally. The primary option is still spinal anesthesia because of its quick onset, excellent blockage, low infection risk, low failure rate, and affordability. The most widely utilized method is bupivacaine spinal anesthesia. By extending and strengthening the sensory blockade, an adjuvant not only boosts the effectiveness of a local anesthetic but also lowers the dosage of local anesthetic drugs.

Aims and Objectives: The aims and objectives of the study are to assess the synergistic effect and safety of adding dexmedetomidine to ropivacaine 0.75% in the subarachnoid block for lower limb surgeries compared to fentanyl to ropivacaine 0.75%.

Materials and Methods: The present study was a prospective randomized control study, carried out at the Department of Anesthesiology and Critical Care, Kempegowda Institute of Medical Sciences, Bangalore, for a period of 2 years. Two groups of 30 subjects each were selected for the study by simple random sampling. Patients with physical status ASA 1 or 2 who underwent elective lower limb surgeries were included. Patients in Group F (n = 30) received 3 mL of isobaric 0.75% ropivacaine and 25 μg fentanyl (0.5 mL) and in Group D (n = 30) received 3 mL of isobaric 0.75% ropivacaine with 10 μg dexmedetomidine (0.5 mL). Sensory testing was assessed by loss of pinprick sensation. The motor block in the lower limb was graded according to the modified Bromage scale. Duration of analgesia was noted. Hemodynamic parameters were recorded every 5 min for 1st 30 min and thereafter every 30 min till the patient complained of pain. Results were analyzed using the SPSS 20.0 version and the association was tested using Student t-test and Chi-square test.

Results: The average time for sensory block onset was 2.93 ± 0.25 min in Group D and 2.43 ± 1.14 min in Group F. In both Group D and Group F, the length of the sensory block was 281.33 ± 25.15 and 144.67 ± 19.43, respectively, and was extremely significant both statistically and clinically. When compared to Group F, which had analgesia for 144.67 ± 19.43 min, Group D experienced analgesia for a significantly longer duration, 360.67 ± 16.17 min. There was a statistically significant difference (<0.001). In Group D, the average motor block duration was 339.67 ± 19.21 min, whereas in Group F, it was 92.33 ± 16.95 min.

Conclusion: When compared to fentanyl as an adjuvant to ropivacaine, intrathecal dexmedetomidine causes a faster onset of sensory and motor blockade and a longer duration of motor and sensory block, as well as hemodynamic stability, higher sedation, and a longer duration of post-operative analgesia.

Key words: Anesthesia; Dexmedetomidine; Fentanyl; Intrathecal; Ropivacaine