Serratus Posterior Superior Plane Block for Postoperative Pain in Cardiac Surgery

Acute pain following cardiac surgery is a prevalent clinical problem that may negatively affect postoperative recovery, pulmonary function, and overall quality of life. Reported rates of moderate to severe pain after sternotomy range widely in the literature, largely due to factors such as vasospasm, heightened inflammatory responses, tissue and bone trauma during surgical dissection, and the placement of chest tubes. Although pain intensity usually subsides after the first 24 hours, inadequate analgesia during this critical period can prolong acute pain, delay mobilization, and increase the risk of chronic post-sternotomy pain syndrome.

Traditionally, neuraxial techniques such as thoracic epidural and paravertebral blocks have been used for pain management in cardiac surgery. However, their application remains controversial due to technical difficulties and patient-related risks, including coagulation disorders, complete heparinization, hemodynamic instability, and potential complications such as pneumothorax. In recent years, fascial plane chest wall blocks, including serratus anterior, parasternal blocks and erector spinae plane blocks, have gained traction as safer alternatives, particularly in patients receiving antiplatelet or anticoagulant therapy.

The serratus posterior superior intercostal plane (SPSIP) block, first described in 2023, represents a novel approach for thoracic analgesia, providing extensive dermatomal coverage from C3 to T10. By targeting the fascial plane between the serratus posterior superior and intercostal muscles, this block offers the potential for effective analgesia across cervical and thoracic regions. Preliminary reports and case series have demonstrated its promising role in thoracic and minimally invasive cardiac surgery.

This prospective, randomized, double-blind, parallel-group trial will evaluate the efficacy of bilateral SPSIP block in patients undergoing on-pump open-heart surgery. Participants will be allocated to either:

SPSIP Group: General anesthesia + SPSIP Block + Patient-Controlled Analgesia (PCA)

Control Group: General anesthesia + Sham Block + PCA

The primary outcome is cumulative morphine consumption during the first 24 postoperative hours. Secondary outcomes include acute pain scores at rest and with movement, time to first opioid demand, rescue analgesia requirements, incidence of postoperative nausea and vomiting (PONV), opioid-related side effects, intraoperative remifentanil consumption, and quality of recovery assessed by the QoR-15 questionnaire.

Inclusion criteria

• Patients aged 18-80 undergoing elective on-pump open-heart surgery via median sternotomy.
• American Society of Anesthesiologists (ASA) classification II-III patients.
• Patients who can use PCA.
• Patients who will sign the informed consent form.

Exclusion criteria

• History of opioid use for more than four weeks
• Chronic pain syndromes
• Patients with a history of local anesthetic or opioid allergy, hypersensitivity
• Alcohol and drug addiction
• Conditions where regional anesthesia is contraindicated
• Failure in the dermatomal examination performed after the block
• Emergency surgeries and redo surgeries.
• Individuals with obstructive sleep apnea.
• Left ventricular ejection fraction less than 30%.
• Patients with severe psychiatric illnesses (such as psychosis, dementia) that limit cooperation with verbal numerical pain scales.
• Pregnant and breastfeeding patients.
• Hematological disorders.
• Significant impairment in the function of a major organ (e.g., severe hepatic or renal disease). • Patients who cannot be extubated within the first 6 hours postoperatively.