Comparison of the Analgesic Effects of Parasternal Intercostal Plane Block Versus Combined Parasternal and Serratus Plane Block After Cardiac Surgery: A Randomized Controlled Trial

Poststernotomy pain after cardiac surgery is a major clinical concern, often leading to impaired respiratory function, limited mobilization, and prolonged intensive care unit (ICU) stay. Although opioids are traditionally used as the mainstay of postoperative analgesia, their side effects-including respiratory depression, nausea, constipation, and delirium-limit their optimal use. Therefore, regional anesthesia techniques that reduce opioid consumption have gained increasing importance in cardiac anesthesia practice.

The parasternal intercostal plane block (PIPB) targets the anterior branches of the thoracic intercostal nerves and has been shown to provide effective analgesia around the sternotomy site. However, PIPB alone may be insufficient for controlling pain originating from lateral chest wall regions, particularly at chest drain insertion sites, which are innervated by the lateral cutaneous branches of the intercostal nerves. To address this limitation, the serratus anterior plane block (SAPB) has been proposed, as it effectively blocks the lateral thoracic dermatomes and thus may provide broader postoperative pain coverage.

This prospective, randomized, single-blind clinical trial is designed to compare the analgesic efficacy of bilateral PIPB alone versus bilateral PIPB combined with unilateral SAPB in adult patients undergoing elective cardiac surgery via sternotomy. A total of 70 patients will be randomly allocated into two groups: Group A will receive bilateral PIPB with standard intravenous morphine, while Group B will receive bilateral PIPB plus unilateral SAPB on the side of chest drain placement. Blocks will be performed under ultrasound guidance using bupivacaine at safe dose limits.

The primary outcome is postoperative pain intensity assessed by the visual analog scale (VAS) at rest and during coughing/movement within the first 24 hours. Secondary outcomes include time to extubation, ICU length of stay, and time to first mobilization. Additional endpoints are rescue opioid requirements and total analgesic consumption within the first 24 hours. We hypothesize that the combined PIPB + SAPB technique will provide superior analgesia, reduce opioid use, and enhance recovery parameters compared with PIPB alone.