Study design
This study was a prospective, parallel group, randomized, and single blinded comparative study, carried out in Ain Shams University Hospitals operation theater between July 2021, and November 2022.
We planned to measure the VAS postoperatively at rest, and on passive movement but most patients were instructed not to move by the surgeon in the immediate postoperative period. We intended to measure the patient satisfaction after 24 hours postoperatively, but we found that many patients were discharged from the hospital before completing 24 hours so the sample size was affected.
The participants
Patients aged between 20-60 from both sexes, ASAI, and II classification undergoing lumbar spine surgeries were enrolled.
Patients with BMI > 35 or < 20, pregnancy, infection at site of injection, psychiatric illness affecting the patient’s judgement, history of coagulaopathies, and allergy to any local anesthestic or any of the drugs used were excluded. Patients with spine deformities (e.g scoliosis) and patients who received massive blood transfusion were excluded also.
Fig (1). Shows the process of patient enrollment, allocation, and statistical analysis.
Sampling Method
All patients were enrolled to the study by our anesthesia residents in Ain Shams University Hospitals, and they were randomly allocated using computer-generated block randomization made by the first generator of randomization.com prepared by an anesthesiologist not participating in the study, which divided them into two equal groups (26 patients each) as shown in Fig.(1):
Group BM: GA + Bupivacaine with Magnesium Sulphate ESPB.
Group BD: GA + Bupivacaine with Dexmedetomidine ESPB.
Sample Size Calculation
Based on the study done by Yesiltas et al., [9] Sample size 52 patients at confidence interval 95 percent. Assuming an effect size of 0.7 as regard duration of analgesic between the 2 groups, a sample of 26 patients in each group would be enough to detect such effect.
Methods
General anesthesia was induced using 2 mg/kg propofol, fentanyl 2 µg/kg, and atracurium besylate 0.5 mg/kg, and it was maintained using isoflurane 1.5-2%. All patients received no additional intra operative opioids except the fentanyl induction dose.
After induction the patients were flipped to the prone position and ESP block was performed using, a high frequency linear ultrasound probe placed longitudinally 2 to 3 cm lateral to the 10th thoracic vertebrae, and the trapezius and erector Spinae muscles identified.
An 18-G Tuohy needle passed along the plane of the transducer until its tip hit the transverse process of T10; the needle was then withdrawn slightly.
Total volume of 25 mL was injected including 20 mL 0.25% bupivacaine plus 3.75 ml NS and 125 mg MgSO4 (1.25 mL) in group (BM) [10].
The other group (BD) received 20 mL 0.25% bupivacaine plus 5ml NS with 1 μg/kg dexmedetomidine [11].
The anesthetic was injected deep to the erector spinae muscle, and the procedure repeated on the other side.
Hemodynamic changes were recorded following the bilateral blocks, adverse intraoperative events, and surgery time were documented.
Following surgery all patients received Diclofenac 0.5 mg/kg 8 hourly, and rescue analgesia with intravenous Nalbuphine 10 mg as required [11].
Postoperatively, pain was rated on Visual Analog Scale (VAS) every 2 hours for 12 hours.
Equipment used for each patient was:
- SonoSite M-Turbo C ® Ultrasound device with HFL – 38 X Linear probe (USA) with high frequency (6 -13 MHz) was used in imaging of patient.
- A 22-G, 5-cm and 10-cm nerve block needle.
- A 20 mL vial of Bupivacaine HCl 0.25%, Dexmedetomidine ampoule (200 mcg/2ml), Magnesium Sulphate vial (25 ml 10%).
The patients were instructed preoperatively to use visual analogue scale (VAS) for pain.
Data Collection
Age, weight, sex, and duration and type of surgery were recorded.
Time needed to perform the block in each group was recorded.
VAS score from 0 = (no pain) to 10 = (worst pain) was used to assess the postoperative pain at rest and on passive movement at the following times: in the recovery room and 2, 4, 6, 8, 10, and 12 postoperatively.
The time to first analgesic request was recorded. It was defined as the time from recovery until VAS score greater than 4.
The total dose of Nalbuphine 10 mg per dose over 24 h postoperatively was recorded. [12]
Patient satisfaction: the following day after the operation the patients were evaluated with a questionnaire on a 10-point scale to assess the patient satisfaction about the postoperative outcome, 24 h postoperatively (from 0 = not satisfied to 10 = fully satisfied).
Any complications during and after the performance of the block – for example, pneumothorax, Horner’s syndrome, hoarseness, difficulty in breathing, weakness, and paresthesia in the arm – was recorded. Postoperative nausea and vomiting, and bradycardia were recorded.
Statistical analysis
SPSS statistics for windows (Statistical Package for the Social Sciences) version 26 (IBM, Armonk, NY, USA) was used for statistical analysis of the collected data. Shapiro-Wilk test was used to check the normality of the data distribution.
All tests were conducted with 95% confidence interval. P (probability) value < 0.05 was considered statistically significant. Charts were generated using SPSS’ chart builder and Microsoft Excel for windows 2019.
Descriptive
Quantitative variables were expressed as mean and standard deviation, median, inter-quartile range, minimum and maximum as appropriate while categorical variables were expressed as frequency and percentage.
Continuous Group differences
Independent sample T and Mann Whitney tests were used for inter-group (between subjects) comparison of parametric and non-parametric continuous data respectively.
For pair-wise comparison of data (within subjects), the follow-up values were compared to their corresponding basal value using paired samples T test or Wilcoxon matched pairs signed ranks test for parametric and non-parametric continuous data respectively.
Categorical Group differences
Fisher exact and Chi square tests were used for inter-group comparison of nominal data using the crosstabs function Anesthesia and the surgical procedure