Evaluation of the Effects of Doses of Dexmedetomidine as Adjuvants to Hyperbaric Bupivacaine in Subarachnoid Blocks for Elective Caesarean Sections: A Prospective, Randomised, Triple-blind Controlled Study

Introduction: Since single-shot spinal anaesthesia for caesarean section operations provides limited postoperative analgesia, several adjuvants are employed to obtain the prolonged duration of sensory block. Dexmedetomidine (DMT) used as an adjuvant to 0.5% hyperbaric bupivacaine is found to provide a longer duration of analgesia.

Aim: To evaluate the block characteristics and neonatal effects of three doses of DMT 2.5 μg, 5 μg and 7.5 μg used as adjuvants to 0.5% hyperbaric bupivacaine (10 mg).

Materials and Methods: A prospective randomised multi arm triple-blind controlled study was conducted at the Gayatri Vidya Parishad Institute of Health Care and Medical Technology, Andhra Pradesh, India from May 2020 to May 2022 on parturients who were assigned to four groups of 20 each. Parturients of Groups A, B and C were given 0.5% hyperbaric bupivacaine (10 mg) with DMT 2.5 μg (0.1), 5 μg (0.2 ) or 7.5 μg (0.3 ) ml respectively as adjuvant and those in Group D were given 2 mL of 0.5% hyperbaric bupivacaine alone and the final volume was made 2.5 in all four groups by adding sterile normal saline (0.9% NaCl). Characteristics of the mother and neonate like age, height, body weight, Body Mass Index (BMI), gravida status etc., were recorded, the duration of analgesia, the total quantity of the analgesic medicine consumed during the 1st 24 hours of the postoperative period, duration of the motor and sensory blocks, changes in haemodynamic variables were also noted. Ramsay Sedation Scores (RSS), surgeon and patient satisfaction scores were recorded for statistical analysis.

Parametric data was analysed using the Analysis of Variance (ANOVA) and Tukey’s post-hoc test and non parametric data using the Chi-square test. Statistical analysis was carried out using Statistical Package for the Social Sciences (SPSS) version 20.0 and a p-value of ≤0.05 was considered statistically significant.

Results: Parturients of Groups A, B and C had an earlier onset of sensory block 4.3±0.8, 3.6±0.5, 2.7±0.5 minutes respectively compared to control 5.7±0.6 minutes (p-value <0.001). They also had a longer duration of analgesia 203.6±14.4, 320.2±24.0, 340.0±14.4 minutes respectively compared to those in control 150.1±7.1 minutes (p-value <0.0001) and consumed a lesser amount of analgesic medication; 165.0±14.4, 110.0±30.7, 100.0±0.0 mg compared to control 190.0±30.7 mg (p-value <0.001). Surgeon scores regarding the anaesthetic technique were satisfactory in a greater proportion/percentage of parturients in Groups A, B and C; 13 (65%), 16 (80%) and 18 (90%), respectively vs 9 (45%) in control p-value <0.01198. Patient scores regarding the anaesthetic technique were satisfactory in a greater proportion/percentage of parturients in Groups A, B and C; 14 (70%), 17 (85%), 19 (95%), respectively vs 10 (50%) in control p-value <0.00652.

Conclusion: On the basis of the results of the present study, it was concluded that 5 μg DMT added as an adjuvant to 10 mg of 0.5% hyperbaric bupivacaine intrathecally was the optimal drug combination to be used for spinal anaesthesia for caesarean section cases, whereas a higher dose of 7.5 μg DMT had resulted in greater fluctuations in Pulse Rate (PR) and Mean Arterial Pressure (MAP) and a lower dose of 2.5 μg DMT had resulted in a shorter duration of analgesia.