Dexmedetomidine Combined With Bupivacaine in Ultrasound-guided Pecto-Intercostal Fascial Block in Cardiac Surgery

Optimal management of median sternotomy pain is a critical factor for achieving adequate recovery after cardiac surgery. The mechanisms of postoperative pain related to cardiac surgeries are intricate and multifaceted. The origins of cardiac surgery pain can be neurogenic, musculoskeletal, or visceral. The skin incision, subcutaneous tissue dissection, sternal retraction, preparation of the internal mammary artery graft, placement of chest drains, and sternal wires directly cause tissue injury. Inadequate pain control can potentially be associated with severe adverse effects such as respiratory compromise, increased myocardial work and oxygen demand, delayed mobilisation, and prolonged hospital stay. Further, increased postoperative pain scores are associated with an increased incidence of chronic pain syndromes.

Patient-controlled analgesia with intravenous opioids is most used to alleviate pain after cardiac surgery. Still, opioids can cause adverse effects, including delayed tracheal extubation, respiratory depression, sedation, ileus, nausea, vomiting, immunosuppression, cough suppression, drowsiness and increased risk of chronic pain. Epidural anaesthesia and paravertebral blocks can provide adequate analgesia with earlier extubation and reduced opioid use in cardiac surgical patients. Still, adverse effects related to pneumothorax, injury to the spinal cord, sympathectomy-induced hypotension, and devastating epidural hematoma after full heparinisation have limited their application in cardiac surgical patients.

An ultrasound-guided peripheral nerve block technique may benefit cardiac surgery patients. Interfascial thoracic wall plane blocks have emerged as a valuable component of multimodal analgesia after cardiac surgery. The pecto-intercostal fascial plane block (PIFPB) is an ultrasound-guided parasternal technique that involves the injection of local anaesthetic (LA) into the plane between the intercostal muscles and the pectoralis major muscle. This technique aims to block the anterior cutaneous branches of the thoracic nerves, specifically T2-T6, which innervate the anteromedial chest wall, including the sternum.

A single dose of a local anaesthetic in a peripheral nerve block could provide short-term analgesia, with bupivacaine typically lasting between 4 and 12 hours. Previous studies reported a mean duration of postoperative analgesia after PIFPB ranged from 8 to 12 hours.

Dexmedetomidine had been successfully used with local anaesthetic in peripheral nerve blocks to prolong the duration of analgesia. Dexmedetomidine is a highly selective alpha-2 adrenergic receptor agonist. As an adjuvant to LAs, dexmedetomidine has been the subject of increasing interest because it has the potential to prolong blockade duration. Dexmedetomidine facilitates nerve block through several mechanisms. It inhibits neurons' sodium channels and potassium currents while blocking the hyperpolarization-activated cyclic nucleotide-gated channel, enhancing activity-dependent hyperpolarisation.

The application of dexmedetomidine in enhancing the quality and duration of analgesia for post-sternotomy pain via the pecto-intercostal fascial plane block has yet to be explored in the existing literature. In this study, we hypothesise that dexmedetomidine in conjunction with bupivacaine within an ultrasound-guided PIFPB block may prolong the duration of postoperative analgesia, reduce opioid consumption and achieve better analgesia after sternotomy compared to bupivacaine alone.

• time to extubation [Time frame: 6 hours after ICU admiision]
• the intensity of postoperative pain at rest and upon coughing [Time frame: 24 hours after extubation]
• time to first rescue analgesia [Time frame: 24 hour after ICU admission]
• patient satisfaction [Time frame: 24 hour after ICU admission]