FROST-STERN: Functional Recovery and Opioid Sparing Technique for STERNotomy A Randomized Trial of Intraoperative Intercostal Cryoablation for Postoperative Pain Management Following Full Sternotomy

FROST-STERN Research Protocol

1. Study Rationale and Background Median sternotomy remains the gold standard surgical approach for complex open-heart surgeries, including coronary artery bypass grafting (CABG) and valve replacements. However, it is inherently associated with severe acute and chronic postoperative pain. Approximately 28% of patients experience chronic post-sternotomy pain, with 4% characterizing it as severe.

Inadequate acute pain management often results in patient "splinting" and impaired respiratory effort. This poor bronchopulmonary hygiene significantly increases the risks of acute postoperative lung complications, such as atelectasis and pneumonia, which can extend intensive care unit (ICU) and hospital length of stay (LOS). The pathophysiology of this pain stems from direct surgical trauma to peripheral nerve pathways, traction-induced brachial plexus injury, and intercostal neuralgia resulting from internal mammary artery harvesting.

While traditional pain protocols rely heavily on systemic opioids, high narcotic burdens carry substantial side effects, including respiratory depression, sedation, and ileus. Traditional regional plane blocks offer relief that lasts only hours rather than months. This trial introduces intraoperative intercostal nerve cryoablation (INC) into a standardized cardiac Enhanced Recovery After Surgery (ERAS) pathway. By utilizing extreme cold to induce temporary, reversible Wallerian degeneration, INC offers a localized, non-addictive, long-acting analgesic solution designed to reduce early postoperative opioid reliance and accelerate the recovery of objective pulmonary function. 2. Participant Recruitment, Screening, and Consent Potential subjects will be identified and recruited from the Cardiac Surgery Clinic (outpatients) or the Inpatient Cardiac Surgery Service days to weeks prior to their scheduled operation.

• Screening: The Principal Investigator (PI) or a designated Study Nurse will review patients' electronic medical charts against strict eligibility criteria.
• Consent Process: Eligible patients will be approached in a private clinic room or at their hospital bedside. The study team will spend 5 to 10 minutes presenting the trial, emphasizing its voluntary nature. Patients will be provided with the written Informed Consent Form (ICF) to read over. Ample time will be provided to answer all questions. To verify comprehension prior to signing, the investigator will ask the patient several validating questions about the study. Once consent is obtained, it will be documented via a formal clinical note in the patient's medical record, and a copy of the ICF will be given to the participant.

3. Randomization, Allocation, and Blinding The FROST-STERN trial is a prospective, randomized, double-blind, parallel-group, sham-controlled trial with a target enrollment of 100 subjects.