This interventional study aims to learn about the postoperative analgesic efficacy of a new fascial plane block, recto-intercostal fascial plane block, at coronary artery bypass grafting with sternotomy. There will be two groups, one of which will be the control group, and the other will be the study group randomly receiving postoperative recto-intercostal fascial plane block.

The main questions it aims to answer are the effect of this new block on postoperative opioid consumption and pain scores. Also, postoperative outcomes related to respiratory ( postoperative oxygenation and atelectasis score), hemodynamic functions ( newly developed arrhythmias), total postanesthesia care unit stay, and hospital stay will be questioned.

All patients will receive standard general anaesthesia under standard monitoring along with the bispectral index (Medtronic). Intubation will be performed by administering intravenous (IV) 0,03 mg/kg midazolam, propofol (Lipuro, Braun, max. 2 mg/kg according to BIS), two mcg/kg fentanyl (Talinat, VEM), 1 mg /kg rocuronium (Esmeron, Alessandroorsini) followed by 1 MAC sevoflurane (Sevorane, Abbott) in an air-oxygen mixture for maintenance of anaesthesia. Following anaesthesia induction, all participants will receive superficial parasternal intercostal plane block (SPIP) bilaterally along with 8 mg dexamethasone before surgical incision as part of multimodal analgesia by a single experienced regional anaesthesiologist (B.C.) under ultrasound guidance (Esaote MyLab ™ Seven). SPIPB will be performed using a high-frequency probe to visualize the pectointercostal fascial area at the intercostal level of the intercostal 3-4 level, and 20 ml %0,25 bupivacaine was injected bilaterally. After applying SPIPB, the surgery is set to begin after at least 15 minutes of block procedure. The intraoperative analgesic need will be supplied by fentanyl bolus doses as 50 mcq if necessary, as heart rate or systolic blood pressure increases by more than %15. According to randomization, the intervention group will receive RIFPB with 10 ml %0,25 bupivacaine.

From the beginning of acclaimed arousal till the 24th hour, rescue analgesia as tramadol 100 mg (maximum daily dose 400 mg) is applied if NRS is over four or with the patient's request. The routine analgesia regimen was 1 gram IV paracetamol 6th hourly postoperatively at the PACU. All patients were followed up from the extubation time till hospital discharge to evaluate respiratory and hemodynamic changes, possible complications and total postoperative time.

Inclusion Criteria:

• patients who will undergo CABG surgery with sternotomy
• patients who have an American Society of Anesthesiologists (ASA) Physical Status classification of III to IV

Exclusion Criteria:

• refusal to participate
• a history of neurological deficits or neuropathy affecting the thoracal innervation
• infection at the site of block application
• allergy to local anesthetics
• epilepsy or treatment with antipsychotics
• abuse of alcohol or drugs
• previous surgery distorting the anatomy of the sternum, thorax or upper abdominal area
• severe organ dysfunction ( kidney, liver and other); patients who fail at weaning after 12 hours of surgery.

The participants under general anaesthesia and the cardiovascular surgeon responsible for the study were blinded to the study groups. This surgeon served as the sole evaluator of postoperative outcomes. Intraoperative results were recorded by the anaesthesia technician, who was present in the operating room and unaware of the block procedures performed. Moreover, the data analysis was conducted before the unblinding of the data.