Magnesium-Enhanced ESPB for Respiratory Recovery and Analgesia in Unilateral Rib Fractures

Aim of the Study To evaluate the effect of adding magnesium sulfate to bupivacaine in ultrasound-guided erector spinae plane block on analgesic efficacy and respiratory recovery in patients with unilateral rib fractures.

Research Methods and Techniques Study Design: Prospective, randomized, comparative, double-blind controlled clinical trial.

Operative Suite: This study will be conducted in the Trauma Unit located in Trauma Hospital - Assiut University.

Study duration: From September 2026 until completion of patient recruitment. All participants will sign an informed consent before inclusion in the study after being individually informed.

Patient Enrollment and sample size:

Sample Size calculation Sample size was calculated using G*power, version 3.1.9.2. Based on earlier studies, we expected to find significant difference in total postoperative morphine consumption (mg) in control group and Magnesium sulphate group (effect size = 0.80) (El Sherif et al., 2022). With a power of 80% (using independent t-test and α*= 0.05) the sample needed for the study was estimated to be 42 patients (21 per each group). Considering an anticipated drop-out rate of 15%, a final sample size of 25 patients per group (50 patients in total) will be enrolled

.

Patients will be randomly allocated in a 1:1 ratio using a computer-generated randomization sequence. Allocation concealment will be achieved using sequentially numbered opaque sealed envelopes. The study solution will be prepared by an anesthesiologist not involved in:

Block performance. Data collection. Statistical analysis.

Patients, outcome assessors, and treating physicians will remain blinded to group allocation.

Group C (Control Group) Patients in Group C will receive: Bupivacaine 0.25% 20 mL Plus 5 mL normal saline total volume = 25 mL Group M (Magnesium sulfate Group) Patients in Group M will receive: Bupivacaine 0.25% 20 mL Plus Magnesium sulfate 500 mg (5 mL) Total volume adjusted to 25 mL.

Justification of Dose The magnesium sulfate dose of 500 mg was selected based on randomized ESPB studies and recent systematic reviews demonstrating improved analgesia with acceptable safety profiles using doses between 250 and 500 mg7.

Study Protocol

The ESPB protocol will be standardized.

Pre-Block Assessment

All patients will undergo:

Detailed history. Clinical examination. Chest imaging review. Baseline VAS score. Baseline respiratory assessment. Baseline vital signs. Monitoring Standard monitoring: ECG, non-invasive mean arterial blood pressure (MAP), pulse oximetry, and respiratory rate 2.

Intravenous access will be secured. Technical Procedure (Intervention)

ESPB Technique: The block will be performed by an experienced anesthesiologist under strict aseptic precautions.

Positioning: Sitting, lateral decubitus, or prone position based on patient tolerance.

Target Level: Mid-thoracic level corresponding to the center of the fractured ribs (typically T4-T5).

Ultrasound Technique:

A high-frequency linear ultrasound transducer will be placed in a longitudinal paramedian orientation approximately 3 cm lateral to the T5 spinous process on the affected side.

The following structures will be identified:

Trapezius muscle. Rhomboid major muscle. Erector spinae muscle. T5 transverse process Local Anesthesia: the needle insertion site will be infiltrated with 1-2 mL of 1% lidocaine in both groups to facilitate needle insertion and minimize procedural discomfort. The same volume and concentration will be used for all patients.

Needle Insertion: A 22-gauge 80-100 mm block needle will be inserted using an in-plane approach, cranio-caudal or caudo-cranial direction. Advance until the needle tip hits the transverse process .

After negative aspiration:

2 mL saline hydrodissection will confirm correct needle placement. The study solution will then be injected deep into the erector spinae muscle. Adequate linear spread beneath the erector spinae muscle will be confirmed by US.

Thirty minutes after the procedure, a pinprick assessment will be performed to confirm the sensory distribution of the block.

Ultrasonographic assessment of diaphragmatic excursion Patients will undergo ultrasonographic assessment of ipsilateral diaphragmatic excursion before performing the block and at predetermined postoperative intervals.

A low-frequency curved-array ultrasound transducer (approximately 2-5 MHz) will be placed in the subcostal region at the mid-clavicular line with the ultrasound beam directed perpendicular to the posterior third of the ipsilateral hemidiaphragm.

M-mode ultrasonography will be used to record diaphragmatic displacement during deep inspiration.

Patients will be instructed to perform maximal deep inspiration following normal expiration.

Three consecutive respiratory cycles will be recorded, and the mean of three measurements will be used as the diaphragmatic excursion value at each assessment point.

Incentive spirometry Volumetric incentive spirometry (VIS) is a simple, non-invasive respiratory device.

It provides a direct measurement of inspired volume, allowing objective assessment of inspiratory capacity.

IT is used to encourage slow, deep inspiration and promote lung expansion

Analgesic Regimen Patients will receive rescue analgesia if VAS ≥ 4: IV Morphine 0.05 mg/kg (time of first dose).

Total morphine consumption will be recorded during the first 24 hours.

Data collection Demographic Data Age, Sex, Weight, Height, and BMI ASA status.

Trauma Characteristics Number of fractured ribs Type and timing of the trauma Side of injury Presence of pulmonary contusion.

Hemodynamic Variables Recorded at:

Time: Baseline, 30 min, 2 h, 4 h, 6 h, 12 h, 24 h, and at the time of rescue analgesia.

Including:

Heart rate Mean arterial pressure Respiratory rate SpO₂ Pain Assessment

VAS score:

Baseline, 30 min, 2 h, 4 h, 6 h, 12 h, 24 h, and at the time of rescue analgesia.

At:

Rest. Coughing. Visual Analog Scale [VAS] scores 8 Pain Level Score No pain 0 Mild pain 1-3 Moderate pain 4-6 Severe pain 7-10

Respiratory Assessment Respiratory rate Ipsilateral diaphragmatic excursion will be recorded at Baseline, 30 min, 2 h, 4 h, 6 h, 12 h, 24 h, and at the time of rescue analgesia, assessed in the same position and by blinded assessor.

ΔDE=DEt -DE at baseline AUCΔDE,0-24h Incentive spirometry volume will be recorded at Baseline, 30 min, 2 h, 4 h, 6 h, 12 h, 24 h, and at the time of rescue analgesia, assessed in the same position and by blinded assessor.

Effective cough score. Pulmonary complications.

Semiquantitative Cough Strength Score (SCSS)9 Cough Strength Score No cough on command 0 Audible movement of air but no audible cough 1 Weakly (barely) audible cough 2 Clearly audible cough 3 Strong cough 4 Multiple sequential strong coughs 5

Analgesic Assessment VAS pain scores at rest and during exertion at predefined intervals over the first 24 hours post-block.

Time to first request for rescue analgesia (administered according to institutional pain management protocols if pain scores exceed specific thresholds).

Total cumulative dose of rescue analgesia consumed during the study period. Patient satisfaction score. Number of morphine boluses. Patient Satisfaction Score10 Description Score Very dissatisfied

1 Dissatisfied 2 Neutral 3 Satisfied 4 Very satisfied 5

Statistical Analysis Statistical analysis was performed using SPSS (Statistical Package for the Social Sciences), version 20 (IBM Corp., Armonk, NY, USA). Data normality was assessed using the Shapiro-Wilk test. Quantitative variables were expressed as mean ± standard deviation (SD). Serial measurements (VAS score, heart rate, mean arterial pressure, respiratory rate, and SpO₂) were analyzed using repeated-measures analysis of variance (ANOVA), followed by appropriate post hoc testing when indicated. Categorical variables were presented as frequency (n) and percentage (%) and compared using the Chi-square test. A two-sided P value \< 0.05 was considered statistically significant.