Background and Purpose: Median sternotomy is the standard surgical approach for cardiac procedures, yet it is associated with significant postoperative pain. Inadequate pain management can lead to pulmonary complications and chronic pain syndromes. While opioids are a cornerstone of multimodal analgesia, their side effects-such as sedation, respiratory depression, and nausea-can delay recovery. Furthermore, neuraxial techniques like epidural analgesia are often avoided in cardiac surgery due to the risks associated with systemic heparinization. This study aims to compare the efficacy of two non-neuraxial regional anesthesia techniques: the combination of Transversus Thoracic Plane Block (TTPB) and Serratus Anterior Plane Block (SAPB) versus the Erector Spinae Plane Block (ESPB).

Study Design and Population: This prospective, randomized study includes 50 patients (ASA I-III, aged 18-80) undergoing elective cardiac surgery via median sternotomy. Patients are randomized into two groups:

TTPB + SAPB Group: Patients receive ultrasound-guided blocks targeting the anterior and lateral chest wall.

ESPB Group: Patients receive ultrasound-guided blocks targeting the paravertebral and intercostal spaces from a posterior approach.

Intervention and Procedures: Following standardized anesthesia induction and invasive monitoring, the respective blocks are performed under ultrasound guidance. Intraoperative hemodynamic data are recorded at key surgical stages (incision, sternotomy, CPB). In the postoperative period in the intensive care unit (ICU), all patients will receive a standardized multimodal analgesia protocol including intravenous (IV) paracetamol and IV tenoxicam. While patients are intubated, pain will be assessed using the Behavioral Pain Scale (BPS). If the BPS score is above 3, IV fentanyl will be administered as rescue analgesia.

Following extubation, pain levels will be evaluated using the Visual Analog Scale (VAS) at rest and during coughing at specific time points (0, 1, 2, 4, 8, 12, 16, and 24 hours). If the post-extubation VAS score is 4 or higher, intramuscular meperidine will be given as rescue analgesia. Additionally, IV ondansetron will be administered in case of nausea or vomiting. The study will also evaluate the time to extubation, time to clinical transport, and patient/surgeon satisfaction using a 5-point Likert scale.

Primary and Secondary Outcomes:

The primary objective of this study is to compare postoperative pain intensity between the study groups using the Visual Analog Scale (VAS) (0-10) and the Behavioral Pain Scale (BPS) (3-12).

Secondary objectives include:

Opioid Consumption: Comparison of total intraoperative and postoperative opioid (IV fentanyl and IM meperidine) consumption within the first 24 hours.

Recovery Milestones: Measurement of time to extubation, time to first mobilization, and time to clinical transport to the surgical ward.

Clinical Satisfaction and Safety: Assessment of patient and surgeon satisfaction using a 5-point Likert scale, and monitoring the incidence of opioid-related side effects, specifically postoperative nausea and vomiting (PONV) requiring ondansetron.

Expected Impact:

By identifying the most effective regional anesthesia technique (TTPB+SAPB vs. ESPB) in conjunction with a standardized multimodal analgesia protocol (IV paracetamol and tenoxicam), this study seeks to maximize postoperative pain control and patient comfort. The results aim to achieve superior analgesia with lower pain scores, thereby facilitating earlier mobilization, reducing the incidence of postoperative complications, and enhancing the overall recovery process for patients undergoing cardiac surgery via median sternotomy. This approach ultimately contributes to the development of more effective, pain-centered recovery protocols in the intensive care unit.

Following informed consent, patients will be randomly assigned to either Group TTPB+SAPB or Group ESPB in a 1:1 ratio using a computer-generated sequence to ensure allocation concealment. This is a prospective, observer-blinded trial. While the anesthesiologist performing the blocks is aware of group assignments, the investigators responsible for postoperative data collection will be blinded to the intervention to minimize bias.

Standardized Anesthesia Management All patients will receive a standardized anesthetic protocol. Premedication with IV midazolam will be followed by standard monitoring including ECG, SpO2, and invasive arterial pressure. General anesthesia will be induced with propofol, fentanyl, and rocuronium, and maintained with sevoflurane in an oxygen-air mixture. The Bispectral Index (BIS) will be monitored to maintain a target range between 40 and 60.

Regional Anesthesia Interventions

Blocks will be performed under ultrasound guidance after induction but before surgical incision:

Group TTPB + SAPB: Transversus Thoracic Plane Block will be performed at the T4-T5 level between the internal intercostal and transversus thoracis muscles. Serratus Anterior Plane Block will be performed over the 5th rib in the mid-axillary line targeting the lateral cutaneous branches.

Group ESPB: The T4 transverse process will be identified, and local anesthetic will be injected into the plane between the erector spinae muscle and the transverse process tip to allow for cranio-caudal spread.

Intraoperative and Postoperative Analgesia Protocol Intraoperative hemodynamic parameters will be recorded at key stages (baseline, incision, sternotomy, CPB). If heart rate or MAP increases by >20% from baseline, a rescue bolus of fentanyl will be administered. Postoperatively, all patients will receive a multimodal analgesia regimen consisting of IV paracetamol and IV tenoxicam. Rescue analgesia will be provided based on pain scale assessments as defined in the protocol.

Statistical Analysis Sample size calculation was performed to achieve 80% power with a 5% significance level, requiring a total of 50 patients to account for potential dropouts. Continuous variables will be compared using the Student's t-test or Mann-Whitney U test, while categorical variables will be analyzed using the Chi-square or Fisher's exact test.

Inclusion Criteria:

• Patients aged between 18 and 80 years.
• Patients with American Society of Anesthesiologists (ASA) physical status I, II, or III.
• Patients who provide written informed consent.
• Patients scheduled for cardiac surgery via elective sternotomy.

Exclusion Criteria:

• Pregnancy or suspected pregnancy
• Body Mass Index (BMI) > 35 kg/m²
• History of allergy to local anesthetics or opioids
• Suspected coagulopathy or infection at the injection site
• Severe neurological, psychiatric, hepatic, or renal failure

"The individual participant data (IPD) will not be shared to protect patient privacy and confidentiality. The data collected for this study will only be used for the purposes of this specific research and will not be made available to other researchers to comply with institutional ethical guidelines."