Comparison of Analgesic Efficacy of Intrathecal Bupivacaine Versus Bupivacaine Plus Dexmedetomidine in Patients Undergoing Orthopedic Surgeries.

TITLE Comparison of analgesic efficacy of Intrathecal Bupivacaine versus Bupivacaine plus Dexmedetomidine in Patients Undergoing Orthopedic Surgeries.

INTRODUCTION Spinal anesthesia is the preferred regional anesthesia technique for lower-limb orthopedic surgeries owing to its rapid onset, profound sensory and motor blockade, cost-effectiveness, and minimal systemic side effects. Hyperbaric bupivacaine remains the most commonly used local anesthetic for spinal anesthesia; however, its duration of postoperative analgesia is limited to approximately 150-210 minutes, frequently requiring early administration of systemic analgesics in the recovery period. 1, 2 Dexmedetomidine, a highly selective α₂-adrenergic agonist, has been widely studied as an intrathecal adjuvant because of its analgesic and sympatholytic properties. Previous studies have demonstrated that the addition of dexmedetomidine to hyperbaric bupivacaine significantly shortens the onset of sensory and motor blockade, prolongs sensory and motor regression, reduces postoperative analgesic requirements, and provides better hemodynamic stability with minimal adverse effects, it can eve reduce bupivacaine related cardiac toxicity.3,6 As Local anesthetics alone have short duration of action and patients may need postoperative systemic analgesics and orthopedic surgeries are associated with postoperative pain leading to unsuccessful rehabilitation and suboptimal healing. So adding an adjuvant like dexmedetomidine can significantly reduce post operative pain and use of systemic analgesics leading to better patient recovery and less morbidity 7,8, Patients receiving 10 µg intrathecal dexmedetomidine with 0.5% hyperbaric bupivacaine showed significantly prolonged sensory regression to S1 segment (413±46 minutes vs 163±24 minutes) and motor block regression to Bromage 0 (307±18 minutes vs 145±25 minutes) compared with patients receiving plain bupivacaine alone. The dexmedetomidine group also required less rescue analgesia during the first 12 postoperative hours.2 Despite this strong and consistent international evidence published in the last five years in surgeries related to gynae and obs, there is still a lack of data in orthopedic surgeries. 9,10 The present study is therefore designed to provide evidence on the analgesic efficacy, block characteristics, and safety of adding 10 µg dexmedetomidine to intrathecal hyperbaric bupivacaine in adult patients undergoing elective lower-limb orthopedic surgery.

OBJECTIVES Primary Objective To compare the mean duration of postoperative analgesia of intrathecal hyperbaric bupivacaine alone versus bupivacaine plus dexmedetomidine in adult patients undergoing elective lower limb orthopedic surgeries.

Secondary Objectives To compare the sensory and motor blockade and hemodynamic side-effect profile of both groups.

OPERATIONAL DEFINITIONS

1. Duration of Analgesia: Time from intrathecal injection to the first request for rescue analgesia or when the Numeric Rating Scale (NRS) score becomes ≥ 4.
2. Duration of Sensory Block: Time from intrathecal injection to two-segment regression of sensory level or regression to the L1 dermatome (assessed by loss of pinprick sensation).
3. Onset of Sensory Block: Time from intrathecal injection to reach sensory block at the T10 dermatome.
4. Duration of Motor Block: Time from intrathecal injection to Modified Bromage Score = 0 (full recovery).
5. Hypotension: Fall in mean arterial pressure (MAP) > 20% from baseline.
6. Bradycardia: Heart rate \< 50 beats/min.
7. Elective Lower Limb Orthopaedic Surgery: Surgical procedures involving the femur, tibia, fibula, or ankle joints, planned in advance and expected to last between 60 and 150 minutes, requiring sensory blockade at or above the T10 dermatome.

HYPOTHESIS Addition of 10 µg dexmedetomidine to intrathecal hyperbaric bupivacaine significantly prolongs the mean duration of postoperative analgesia compared to hyperbaric bupivacaine alone in adult patients undergoing elective lower limb orthopaedic surgeries.

Secondary Hypothesis Addition of 10ug of Dexmedetomidine into intrathecal hyperbaric bupivacaine affects sensory and motor blockade and reduces hemodynamic side effects of bupivacaine alone.

MATERIAL AND METHODS Study Design: Prospective, randomized, double-blind, parallel-group controlled clinical trial.

Study Setting: The study will be conducted at SKBZ-AK CMH, Muzaffarabad, Azad Kashmir Duration of Study: The study will be carried out over a period of 03 months after the approval of synopsis.

Sample Size: The sample size was calculated using a two-sided two-sample parallel means comparison formula based on the reference study by Alam et al. evaluating the effectiveness of intrathecal dexmedetomidine in combination with hyperbaric bupivacaine. Using a 95% confidence level, 90% statistical power, and a 1:1 group allocation ratio, the statistical calculation yields a minimal size of 32 patients per group. However, to account for potential dropouts, technical failures of the subarachnoid block, or intraoperative alterations in the surgical plan, the sample size was increased to 40 patients per group (Group B = 40, Group D = 40), making a total sample size of 80 patients.

Sampling Technique: Non-probability, consecutive sampling. Sample Selection

DATA COLLECTION PROCEDURE The study will be performed after taking approval from the ethics review committee of SKBZ-AK CMH Muzaffarabad and CPSP. A total of 80 patients presenting to the pre-anaesthesia clinic, meeting the enrollment criteria, will be recruited in the study after obtaining informed consent of the patients. Patient characteristics like age, gender, weight, height, ASA status, and baseline hemodynamics will be recorded.

Patients will be randomly allocated to either Group B (Control) or Group BD (Study) using computer-generated random numbers with SNOSE allocation concealment. Group B will receive 15 mg of 0.5% hyperbaric bupivacaine plus 0.5 mL normal saline. Group BD will receive 15 mg of 0.5% hyperbaric bupivacaine plus 10 µg dexmedetomidine. The study drug will be prepared by an independent technician to maintain double-blinding.

Standard monitoring will be established and spinal anaesthesia will be performed at L3-L4/L4-L5 space. Onset and duration of sensory and motor blocks will be assessed using pinprick and Modified Bromage Scale. The duration of analgesia will be recorded as the time to the first request for rescue analgesia (NRS ≥ 4). All the patients will be monitored for side effects like hypotension and bradycardia for 24 hours. All the data will be recorded on a pre-designed proforma.

DATA ANALYSIS PROCEDURE Data will be analyzed using Statistical Package for the Social Sciences (SPSS) version 26.0. Descriptive statistics will be calculated for all variables. Continuous variables-including age, weight, height, BMI, onset of sensory block, duration of sensory and motor blockade, and the primary outcome (duration of postoperative analgesia)-will be assessed for normality using the Shapiro-Wilk test.

Normally distributed continuous data will be presented as Mean ± SD and compared between the two groups using the Independent samples t-test. Non-normally distributed data will be presented as Median (Interquartile Range) and analyzed using the Mann-Whitney U test. Hemodynamic trends (Heart Rate, MAP) and pain scores (NRS) recorded at multiple time intervals will be analyzed using Repeated Measures ANOVA to evaluate differences over time between the groups.

Categorical data, including Gender, ASA Status, and the incidence of adverse events (hypotension and bradycardia), will be expressed as frequencies and percentages, and compared using the Chi-square test or Fisher's exact test where cell counts are less than 5. A p-value of \< 0.05 will be considered statistically significant for all analyses.

Research Performa

Name:__________________ Age:_______________ Gender:_________________ Phone:_______________ Weight:_________________ Height:_______________ BMI___________ Level of Block_____________ ASA Class______________ Type of Surgery ___________

Time Pulse SBP Diastolic MAP SPO² Pre SAB 5 min 10 min 20 min 30 min 40 min 50 min 60 min 70 min 80 min 90 min 100 min 110 min 120 min

Time NRS Sensory Block Bromage score RASS Onset

1st hour 2nd hour 3rd hour 4th hour 5th hour 6th hour 8th hour 10th hour 12th hour

1. st Hour
2. nd Hour
3. rd Hour
4. th Hour
5. th Hour
6. th Hour

8th Hour

10th Hour

12th Hour

Comments (If any):

Sign and Stamp:_______________________. Date:________________