Serratus Posterior Superior Intercostal Plane Block in Minimally Invasive Cardiac Surgery

Study design and setting: This is a single-centre, prospective, randomised controlled, parallel-group trial with a 1:1 allocation ratio, conducted at Kosuyolu High Specialization Education and Research Hospital, Istanbul, Turkey. Ethics committee approval (2025/12/1164) covers elective minimally invasive cardiac procedures performed through a right or left minithoracotomy.

Participants: Adults with American Society of Anesthesiologists (ASA) physical status I-III who are scheduled for elective minimally invasive cardiac surgery through a right or left minithoracotomy, irrespective of the cardiac procedure (coronary artery bypass grafting with or without cardiopulmonary bypass, valve surgery, atrial septal defect closure or cardiac tumour excision).

Randomisation and blinding: An investigator who is not involved in block performance or outcome assessment generates the allocation sequence using block randomisation (block size of six; 1:1 allocation) and places assignments in sequentially numbered, sealed, opaque envelopes. The principal investigator, who performs all blocks, opens the envelope immediately before the procedure. The anaesthesiologist responsible for intraoperative management, surgical team, intensive care unit staff, nurses and acute pain team performing postoperative assessments are unaware of group allocation. Patients are not explicitly informed of their allocation; no sham block is performed in the control group.

Intervention: In the SPSIPB group, ultrasound-guided serratus posterior superior intercostal plane block is performed in the block room approximately 30 min before transfer to the operating room, with the patient in the lateral decubitus position and the operative side uppermost. The needle is advanced in-plane in a caudocranial direction until its tip is positioned between the serratus posterior superior muscle and the third rib, followed by injection of 30 mL of 0.25% bupivacaine. No regional block is performed in the control group.

Anaesthesia and analgesia: General anaesthesia is standardised in both groups using propofol, rocuronium and sevoflurane. Intraoperative remifentanil infusion is titrated to maintain systolic blood pressure within ±20% of the pre-incision value. Postoperatively, all patients receive intravenous paracetamol 1 g every 8 h and intravenous tramadol patient-controlled analgesia (10-mg bolus, 15-min lockout interval, no basal infusion, maximum 100 mg over 4 h and 400 mg over 24 h). Intravenous tenoxicam 20 mg is administered as rescue analgesia for a numeric rating scale (NRS) score ≥4 at rest and/or on movement.

Assessments and outcomes: The primary outcome is cumulative tramadol consumption recorded from the patient-controlled analgesia device during the first 24 h after extubation. Blinded nurses and the acute pain team assess NRS pain scores at rest and during shoulder flexion, as well as postoperative nausea and vomiting, at 1, 4, 8, 16 and 24 h after extubation. Secondary outcomes include rescue analgesia requirements, intraoperative remifentanil consumption, the change in systolic blood pressure 1 min after skin incision, time to extubation and intensive care unit length of stay. The timing of the first rescue analgesic dose and other perioperative haemodynamic variables are also recorded.