Comparison of analgesic efficacy of dexamethasone and dexmedetomidine as an adjuvant to local anaesthetic in transversus thoracic muscle plane block in adult patient undergoing median sternotomy: A randomized control trial

Median sternotomy is commonly practiced approach for patients undergoing open heart surgery. Postoperative sternotomy pain, which is common after cardiac surgery, can result from various factors such as rib fractures, damage to costal cartilage, or injury to intercostal nerves due to extended sternal retraction and surgical incisions. While this pain is typically most intense on the initial day following surgery, it can persist for as long as one week during the postoperative period.1 Multimodal analgesic techniques are required to alleviate this acute post sternotomy pain and aid in early weaning and recovery post surgery. In cardiothoracic surgery, regional anesthesia is used as a component of multimodal analgesic techniques to prevent acute post sternotomy pain. Thus, fast-track anesthetic approaches for early weaning and recovery have become popular by decreasing preference of opioid use and its associated side effects. Moreover, these regional techniques have proven useful in aiding faster extubation and shortening the duration of intensive care (ICU) and hospital stays for patients undergoing cardiac surgery. Over the years, different neuraxial techniques like thoracic epidural anesthesia, intrathecal spinal morphine or paravertebral blocks have been identified as a part of multimodal analgesia for median sternotomy but all have their own limitations. The ultrasound guided transversus thoracic muscle plane block (TTPB) is relatively new truncal interfascial plane blocks that aim to anesthetize the anterior cutaneous branches of the thoracic intercostal nerves (Th2-6) through a single injection. Perineural dexamethasone or dexmedetomidine prolongs the duration of single-injection peripheral nerve block when added to the local anesthetic solution. 3,4,5 Few case reports and observational studies have been carried out to study the efficacy of this block, however no RCTs have been done comparing efficacy of two different additives to local anesthetic in transversus thoracic muscle plane block. We propose to conduct this randomized clinical trial to study the analgesic efficacy of dexamethasone and dexmedetomidine as an adjuvant to local anaesthetic in transversus thoracic muscle plane block in adult patient undergoing median sternotomy.

  Problem statement- Perioperative sternotomy pain management in cardiac surgery has always remained a challenging concern. Adequate pain control reduces postoperative respiratory dysfunction and promote early weaning and recovery. Opioids are one of component of perioperative pain management, however its usage is associated with adverse effects like respiratory depression, postoperative nausea vomiting. Use of neuraxial techniques like thoracic epidural anesthesia with catheter in situ, intrathecal technique, paravertebral blocks may predispose to the complications such as an increased risk of epidural/spinal hematoma due to systemic heparinization, potential hemodynamic instability, technical difficulties, and pneumothorax. Infiltration of the sternotomy wound with indwelling catheters, intercostal nerve blocks, parasternal blocks, or erector spinae blocks has been used to anesthetize the parasternal region but inability to block the parasternal region, systemic heparinization limits their utility. A regional analgesia technique like the TTM plane block would reduce perioperative opioid requirement and enhance early weaning and recovery.

 Rationale – TTPB is aimed to anesthetize the anterior cutaneous branches of the thoracic intercostal nerves (Th2-6). These blocks may reduce acute sternotomy pain and opioid consumption by blocking the anterior chest wall. This block is technically easy to perform with the aid of ultrasonography while patient in supine position.

 Novelty- There are few case reports showing TTPB as a part of multimodal analgesic regime in cardiac surgeries. No RCT have been done comparing efficacy of two different additives to local anesthetic in transversus thoracic muscle plane block for patient undergoing median sternotomy.

 Expected outcome and application – Increased duration of time to first request of rescue analgesia in postoperative period and thus reducing total opioid consumption within 24 hours post surgery. This will facilitate to include this block with both additives as a part of multimodal analgesic regimen in routine practice in our set up in this set of patients.

 1. Research question- Does addition of dexmedetomidine and dexamethasone to bupivacaine in transversus thoracic muscle plane block effectively prolong the analgesia for post sternotomy pain and reduce the perioperative opioid consumption after open heart surgery?

2. Research hypothesis: Addition of dexmedetomidine and dexamethasone to bupivacaine in transversus thoracic muscle plane block effectively prolong the analgesia for post sternotomy pain and reduce the perioperative opioid consumption after open heart surgery.