Comparison of dexmedetomidine dosing strategies based on Bispectral Index (BIS) and Ramsay Sedation Scale (RSS) in patients undergoing infraumbilical surgeries under spinal anesthesia: A prospective comparative study

Objectives and Aim: This study aimed to evaluate the impact of dexmedetomidine infusion dosage adjustment strategies guided by BIS and RSS on total consumption in patients undergoing infraumbilical surgeries under spinal anesthesia.Materials and Method: Eighty patients aged between 18-70 years, classified as American Society of Anesthesiologists (ASA) I and II, who underwent orthopaedic, urological, and plastic surgery under spinal anesthesia were included. Patients received spinal anesthesia in the lateral position through the L3-4 interval using a median approach. Following the observation of free flow of cerebrospinal fluid, spinal anesthesia was induced with 10 mg (2 ml of 5% hyperbaric bupivacaine) bupivacaine and 25 µg of intrathecal fentanyl. When the sensory block reached the T10 level, all patients were administered a dexmedetomidine loading dose of 1 µg/kg IV over 10 min for sedation, and the maintenance drug infusion dose was titrated to maintain BIS values between 60-80 in the first group and RSS at 3-4 in the second group. Throughout the surgery, hemodynamic variables (heart rate and blood pressure), respiratory parameters (respiratory rate), SpO2, sedation scores (BIS and RSS), and drug infusion doses and perioperative complications were recorded. Drug infusion was stopped 5 min before the end of surgery, and the duration of surgery, anesthesia, and total drug consumption were recorded. Statistical analyses were performed, and a p-value of less than 0.05 was considered statistically significant.Results: Desired sedation was achieved by dexmedetomidine administration. A decrease in BIS values and an increase in RSS were observed with the loading dose. In both groups, the heart rate and systolic and diastolic blood pressures were significantly lower at all measurement times than the control values. There was no significant difference in the mean blood pressure between groups B and R (p>0.05). The average blood pressure for B group was 92 ± 14.12 mmHg, while the average blood pressure for R group was 90 ± 12.73 mmHg. There was no statistically significant difference between the two groups in terms of dexmedetomidine infusion doses required to achieve the desired sedation and total drug consumption 110 ± 20 (µg) in B group and 111 ± 22 µg in R group (p>0.05).Conclusions: Dexmedetomidine provides a targeted level of sedation in patients undergoing spinal anesthesia without causing significant respiratory depression. Monitoring sedation depth using the BIS did not change the total drug consumption.