Combined SPSP and TTP Blocks for Postoperative Analgesia Post-CABG

This is a single-center, patient- and outcome-assessor-blinded, randomized controlled trial conducted at Ain Shams University Hospitals, Cairo, Egypt. Adults aged 18-75 years scheduled for elective isolated CABG via median sternotomy will be enrolled.

Eligible participants will be randomized 1:1 to either:

Intervention group: Bilateral transversus thoracic plane (TTP) block + bilateral serratus posterior superior (SPSP) block with 0.25% bupivacaine (15 mL per side per block, total 60 mL = 150 mg), performed after induction of general anesthesia and before surgical incision, plus standardized multimodal systemic analgesia.

Control group: Standardized multimodal systemic analgesia alone (no nerve blocks).

Both groups will receive identical standardized anesthesia (fentanyl, propofol, atracurium, sevoflurane), intraoperative hemodynamic management, and postoperative analgesia (IV paracetamol 1 g q6h scheduled, IV ketorolac 30 mg q8h for 24h then 15 mg q8h, rescue IV morphine via protocolized algorithm and patient-controlled analgesia).

The primary endpoint is cumulative 24-hour postoperative opioid consumption (IV morphine milligram equivalents) from extubation. Secondary endpoints include NRS pain scores at rest and with movement at 0, 6, 12, 24, and 48 hours; time to first rescue analgesia; time to first ambulation; respiratory outcomes (time to extubation, PaO₂/FiO₂ ratio, pulmonary complications); hemodynamic stability; ICU and hospital length of stay; patient satisfaction (Likert 1-5); and safety outcomes (block-related complications, LAST, opioid-related adverse events).

Sample size: 88 patients (44 per group), calculated for 80% power to detect a 30% reduction in 24-hour opioid consumption (Cohen's d = 0.60) at α = 0.05, with 15% dropout allowance.

Randomization will be computer-generated with permuted blocks (sizes 4 and 6), stratified by on-pump versus off-pump status and sex. Allocation concealment via sequentially numbered opaque sealed envelopes. Blinding: patients, outcome assessors, ICU staff, data collectors, statisticians, and non-performing anesthesiologists/surgeons will be blinded; only the performing anesthesiologist will be unblinded.

A Data and Safety Monitoring Board will review unblinded safety data at 25% and 50% enrollment. Stopping rules: any death attributable to intervention, ≥2 symptomatic pneumothoraces, or ≥2 severe LAST events.

Statistical analysis: ITT as primary population, per-protocol for sensitivity. Primary analysis: ANCOVA adjusting for age, sex, BMI, on-pump status, and intraoperative opioid dose. Missing data handled via multiple imputation (MICE, 20 datasets) with sensitivity analyses.

Inclusion criteria

• Adults aged 18-65 years.
• Scheduled for elective, isolated CABG via median sternotomy.
• American Society of Anesthesiologists (ASA) physical status II-III.
• Ability to understand the study procedures, provide written informed consent, and reliably report pain scores using the NRS.

Exclusion criteria

• Emergency surgery or pre-operative hemodynamics instability.
• Known allergies or hypersensitivity to local anesthetics, paracetamol, morphine, or any study medication.
• Coagulopathy, uncontrolled bleeding risk, or therapeutic anticoagulation that cannot be safely withheld per institutional guidelines (INR > 1.5; platelets < 100 × 10⁹/L at time of block).
• Local infection or cellulitis at any planned injection site on the anterior or lateral chest wall.
• Pre-existing chronic pain syndrome requiring daily opioid analgesia or known opioid dependence.
• Significant cognitive impairment, severe psychiatric disorder, or inability to reliably use pain scales.
• History of prior thoracic surgery or major chest wall deformity distorting anatomy or limiting the ultrasound window.
• Pregnancy or breastfeeding.
• Any other condition judged by the investigator to represent unacceptable risk or preclude study participation.
• Patient refusal or withdrawal of consent.