Adding Different Doses of Dexmedetomidine to Bupivecaine in Erector Spinae Plane Block

Scientific committee approval:

(Was it scientifically approved by the department?) Yes Date of approval: 5/11/2025

Background and Rationale:

Lumbosacral spine fixation surgeries are among the most common spinal surgical operations done by neurosurgeons and spine surgeons nowadays. (1, 2) The spine instrumentation in this surgery lead to severe postoperative pain that annoys most patients and may lengthen the hospital stay and prolong the rehabilitation time.(3) The postoperative pain seen immediately after lumbosacral fixation surgery is either musculoskeletal pain or acute inflammatory pain that starts with the inflammatory tissue response and decreases over time with wound healing, with a risk of becoming chronic low back pain if not treated early and adequately.(4) Multimodal analgesia techniques are applied to provide adequate postoperative analgesia and pain control. The traditional use of opioid-based analgesia techniques is usually accompanied by some annoying adverse side effects, such as nausea, vomiting, pruritus, and respiratory depression. Although epidural analgesia is considered the gold standard approach for control of postoperative pain and proper postoperative analgesia, in the lumbosacral spine fixation surgery, the insertion of epidural catheter preoperatively or intraoperatively is not applicable as this will interfere with surgical field, dural tear may occur during surgery leading to leakage of the local anesthetic and also still the epidural catheter carry the risk of infections, hematomas, and other adverse effects.(5,6) Ultrasound-guided plane blocks using local anesthetics are standard multimodal analgesia techniques due to their low complication rate, ease of application, and adequate postoperative analgesia. Followed by the first documentation by Forero et al in 2016, the erector spine plane block [ESPB] has been used to provide postoperative analgesia in thoracic and thoracoabdominal surgeries, bariatric surgery, and recently, ESPB has also been used to provide adequate postoperative analgesia in spine surgery.(7) Ultrasound-guided ESPB is considered a novel interfascial plane block technique in which local anesthetic is injected into the fascial plane, which is localized anatomically between the transverse process of the spinal vertebrae and the erector spinae muscles, and it is considered a safe, simple procedure used to perform adequate postoperative analgesia.(8,9) Many studies and case reports have reported that ultrasound-guided ESPB leads to adequate and effective postoperative analgesia management in spinal surgeries. However, ESPB makes short postoperative analgesia and pain control not exceeding 6 or 8 hours, even using medium or long-acting local anesthetics.(10,11) Dexmedetomidine is a highly selective alpha 2-adrenoceptor agonist with sedative, anxiolytic, sympatholytic, and analgesic-sparing effects and minimal depression of respiratory function.(12) Dexmedetomidine acts on presynaptic and postsynaptic sympathetic nerve terminals and the central nervous system, decreasing the sympathetic outflow and noradrenaline release and causing sedation, anxiolytic, analgesic, and sympatholytic effects. It lacks opioid like properties, so opioid related adverse side effects are not found.(13) Recently, the use of dexmedetomidine as a local anesthetic adjuvant raised the interest issue of regional anesthesia and analgesia due to many causes. It shortens the onset time of anesthesia, extending the duration of peripheral nerve block, decreasing the postoperative pain with maximal analgesic effect, and with acceptable adverse effects.(14-19) To our knowledge, only one study resulted in the conclusion; dexmedetomidine, as an adjuvant to bupivacaine used in ESPB for postoperative pain control of posterior lumbosacral spine fixation procedures had significantly prolonged the efficacy and time of analgesia of (up to 36 hours). This study used patient controlled analgesia ( PCA )for all patients.(20)

Objectives:

Comparing the quality of analgesia between bupivecaine versus bupivecaine plus different doses of dexmedetomidine.

To assess the postoperative VAS score. To determine the time of the first analgesic request. To calculate intraoperative and postoperative opioid consumption. To evaluate the postoperative patient satisfaction. Study Design: (Please fill in the appropriate study design, see attached PDF guide) Descriptive: - Survey (cross sectional)

• Qualitative (Please fill in the appropriate study design, see attached PDF guide) Descriptive: - Survey (cross sectional)
• Qualitative

Analytic: - Observational: - Case-control study

• Cross sectional analytic study
• Cohort (Longitudinal) study
• Experimental: - Randomized Clinical Trial Phase:
• Non-randomized clinical trial
• Animal study
• Cellular study

Others: Please describe:

Study Methods Study design A double blinded randomized controlled study. Study setting and location The study will be conducted in Cairo university hospitals. Study population Patients aged 18 years or above, undergoing lumbar spine surgery. Eligibility criteria Inclusion criteria Both genders. Physical status ASA I, II. Age more than or equal 18 years. Body mass index (BMI): > 20 kg/m2 and \< 35 kg/m2. Exclusion criteria Patient's refusal Patients with known sensitivity or contraindication to drugs used in the study (local anesthetics, dexmedetomidine and opioids).

History of psychological disorders and/or chronic pain. Pre- existing peripheral neuropathies. Coagulopathy ; INR more than 1.5, platelets less than 100 ×103/mm3 Infection of the skin at the site of needle puncture area. Study procedures Randomisation (in RCT only) The patients will be allocated into three groups using computer-generated random numbers that will be concealed in opaque envelopes.

The data collector, surgeons and participants will be blinded to the group allocation.

Study protocol:

All patients will be instructed to fast for 6 hours for solid food and 2 hours for clear liquids. On arrival at the operating room, immediate preoperative evaluation will be done, peripheral intravenous line will be inserted, standard mointoring will be connected including pulse oximetry, ECG, NIBP, capnography and readings will be documented preopertaive and every 5 minutes throughout the procedure. General anesthesia will be induced by fentanyl 2 mcg/kg, propofol 2 mg/kg, rocuronium 0.6 mg/kg. Maintenance of anesthesia will be done by isoflurane. The prone position will be established after tracheal intubation. Before the surgery, ultrasound guided ESPB will be done preoperative under complete aseptic condition. A sterile ultrasound curved probe (25 MHz convex probe, (GE Logiq P5 Ultrasound System) will be used for the technique. The ultrasound probe will be placed on the third lumbar vertebral body level in the parasagittal plane. When the spinous process will be first seen, the probe will be moved laterally from the midline, and then the transverse process (TP) of L3 and erector spinae muscle will be observed at about 2 to 3 cm from the midline.

Using the in-plane technique, a 100-mm, 20-gauge (100 mm, 20G, 30o visioplex, VYGON, Ecouen, France) needle will be used to make a puncture. The direction of the needle will be craniocaudal, and the proper position of the needle will be confirmed by injecting 2 mL of saline solution. After ensuring the position of the needle, 30 ml volume will injected per side slowly according to grouping; Group A (control group); 29 ml bupivecaine 0.25 % plus 1 ml normal saline per side.

Group B (lower dose dexmedetomidine); 29 ml bupivecaine 0.25 % plus dexmetomidine 0.25 mcg/kg in 1 ml normal saline per side.

Group C (higher dose dexmedetomidine); 29 ml bupivecaine 0.25 % plus dexmetomidine 0.5 mcg /kg in 1 ml normal saline per side.

30 minutes will be elapsed after completion of ESPB and before starting of surgery. Ringer acetate will be infused to replace their fluid deficit, maintenance, and losses.

First reading of mean arterial pressure (MAP) and heart rate (HR) will be taken before induction of anesthesia to be defined as a baseline reading. Another reading will be taken after the application of the block and every 5 minutes to give the mean for each 15 minutes. Sudden rise of HR and/or MAP more than 20% of basal readings as a response of surgical incision will be treated by intravenous morphine 0.05 mg/kg and will be repeated after 15 minutes as required till effect of stable hemodynamics.

Hypotension (reduction of MAP more than 20% of baseline reading) will be treated with 0.9% normal saline and/or 5mg ephedrine in incremental doses to maintain mean blood pressure above 70 mmHg.

In the postoperative period, regular analgesia in the form of intravenous paracetamol one gram/8hr will be prescribed. Pain severity will be assessed by using the visual analogue scale (VAS, passive and active.) (0= no pain and 10= worst pain) at 1,4, 8, 12,16,20 and 24 hr after the end of the ESPB block procedure. The VAS will be assessed at rest and movement. Rescue analgesia in the form of intravenous morphine 0.05 mg/kg will be given on the patient's complaint or if VAS ≥ 4 to be repeated every 15_20 minutes until VAS \< 4. The time of the first analgesic request will be calculated as the time elapsed from the end of the ESPB block procedure till VAS ≥ 4. The total dose of morphine consumption (intraoperative and postoperative) over 24 hours will be calculated (maximum dose of morphine rescue analgesia in 24 hours is 40 mg). Postoperative complications including nausea, vomiting, and dizziness will be recorded and managed accordingly. Before leaving the hospital, patient satisfaction will be assessed using a four-point score 0 = not satisfied, 1= satisfied with major comments, 2= satisfied with minor comments, and 3= satisfied with no comment). All postoperative data will be collected by an anesthesiologist who will be blinded to the patient's allocation.

Intervention:

Diagnostic intervention (please describe):

Therapeutic intervention (please describe):

No intervention

Does the research involve? Human participants Biological samples/Tissues Identifiable private data/Information

Type of consent of study participants:

Written consent Oral consent No consent needed (Please justify)

Potential risks:

(Please mention all risks involved even mild ones as pain, discomfort, chance of infection or psychological effects) Confidentiality of data: (Please explain how privacy and confidentiality of data and records will be maintained)

Study outcomes:

Primary outcome Mean value of VAS (passive and active) at 1,4, 8,12,16,20 and 24 hr postoperative.

Secondary outcomes The total dose of morphine consumption (intraoperative and postoperative) over the first 24 hrs.

Heart rate (HR), mean arterial pressure (MAP), and oxygen saturation (SaO2) at 1, 4, 8, 12, 16, 20 and 24 hr postoperative.

Time of first analgesic requirement (postoperative 1st dose of morphine) Postoperative complications ; nausea, vomiting, dizziness, block failure. Patients satisfaction.

Criteria of ESPB block failure :

Intraoperative: suden in rise of HR and/or MAP more than 20% of basal readings as a response to skin incision.

Postoperative: If the VAS score is greater than or equal to 4 in the 1st hour after the recovery of general anesthesia.

Sample size:

Study subjects include the use of dexmedetomidine as an adjuvant to bupivacaine in erector spinae plane block in patients undergoing lumbar spine surgery. A total of 90 patients will be recruited (30 in each group, 1:1:1 allocation).

The primary outcome for sample size determination is the time-weighted average Visual Analogue Scale (VAS) at rest over the first 24 hours postoperatively (010), which is a continuous measure. Accordingly, sample size was calculated using an ANOVA design appropriate for comparing means across three independent groups (bupivacaine alone; bupivacaine + dexmedetomidine 0.25 μg/kg; bupivacaine + dexmedetomidine 0.5 μg/kg).

Based on one-way ANOVA assumptions (k = 3, α = 0.05, power = 80%, equal allocation), and taking into account feasibility and resource constraints, the final chosen sample size is 90 patients (30 per group). This number is sufficient to detect at least a moderate effect size (Cohen's f ≈ 0.35) with a power ≥80%.(21) Statistical analysis: (Please describe your data analysis plan) Statistical presentation and analysis of the present study was conducted, using the mean, standard deviation, chi-square test was used to compare between groups in qualitative data and ANOVA test was used for comparison among different times in the same group in quantitative data by (IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.).

Significant level:

>0.05 Non significant \<0.05* significant \<0.001* High significant Source of funding Faculty of Medicine, Cairo University

Other sources:

Please specify: Self-funded.