Erector Spinae Plane vs Serratus Anterior Plane Catheter Infusions for Acute Pain Management in Patients With Traumatic Rib Fractures

Traumatic rib fractures occur in 10%-20% of blunt trauma patients and are associated with significant mortality (22% and 10%, in the elderly and young patients, respectively). Patients with rib fractures are predisposed to multiple pulmonary complications including pneumonia, aspiration, pleural effusion, pulmonary embolism, atelectasis and acute respiratory distress syndrome. Effective analgesia, albeit challenging, has been found to reduce the incidence of those complications. It is postulated that pulmonary complications occur post rib fractures due to impaired pulmonary mechanics, inappropriate clearance of secretions, and atelectasis; hence the need for adequate and affective pain control.

Opioids are commonly used for analgesia in critically ill patients but they carry notable adverse effects including: respiratory depression, hemodynamic instability, tolerance, hyperalgesia, delirium and gastrointestinal side effects. They are also associated with prolonged mechanical ventilation, counteracting goals for rib fracture management. Therefore, alternative analgesic option such as regional anesthesia techniques have gained more popularity. Regional anesthetic blocks can improve analgesia and reduce opioid requirements. Options for rib fractures include thoracic epidural analgesia (TEA), paravertebral block, intercostal block, erector spinae plane block (ESP), and serratus anterior plane block (SAP).

Continuous peripheral nerve blockage has gained more popularity in trauma settings; especially continuous fascial plane catheters which can offer effective analgesia without many contraindications associated with thoracic epidurals. Frequent contraindications to thoracic epidural blocks in trauma populations have driven interest in alternative analgesic modalities such as continuous fascial plane infusions, despite the lower pneumonia rates that are associated with thoracic epidural analgesia.

Serratus Anterior Plane Block (SAP Block): The SAP block is an ultrasound guided block that involves the injection of local anesthetic superficial to the serratus anterior muscle in the mid axillary line. It provides effective analgesia for patients with anterolateral rib fractures but might be ineffective for posterior rib fractures. It consistently involves the lateral cutaneous branches of intercostal nerves, which innervate the superficial anterolateral chest wall. It might spare the intercostal nerves supplying the posterior ribs and intercostal muscles. However, a cadaveric study showed that disruption of tissue planes in trauma may promote deeper spread of local anesthetic reaching the intercostal nerves and reaching the posterior rib space.

Erector Spinae Plane Block (ESP Block): The ESP block is an ultrasound guided block which involves injection of local anesthetic into the erector spinae fascial plane. It is thought to work by blocking the lateral cutaneous and intercostal nerves with potential diffusion into the paravertebral space. It is technically easy and can be performed at bedside. Risks are low, particularly when performed under ultrasound guidance, and include hypotension, vascular puncture, contralateral spread via the epidural space, and pneumothorax. A continuous nerve catheter is typically used for rib fractures with the goal of inserting the needle midpoint of the rib levels. A randomized trial has showed that continuous ESP block is as effective is thoracic epidural analgesia for pain control in patients with unilateral rib fractures.

Addressing evidence gaps: A recent scoping review published by our research group indicated that SAP and ESP are the most common regional anesthesia techniques for acute traumatic rib fractures. There has been one head-to-head study comparing SAP to ESP that demonstrated superior analgesia in favour of ESP for traumatic rib fractures however it was designed as a single injection study. Given that the SAP catheter is potentially easier to perform (i.e., no need to place patient in lateral decubitus position and shallower sonographic target), is ESP superior to SAP catheter infusion to warrant the additional time and effort? To our best knowledge, no prospective comparative studies on SAP and ESP catheters have directly evaluated analgesic efficacy, opioid consumption, respiratory outcomes, and ease of performance between these two catheter techniques in a systematic manner. Understanding which technique provides superior analgesia while remaining technically straightforward for widespread implementation is critical for standardizing regional anesthesia practice in rib fracture management. We propose a pragmatic, randomized controlled trial (RCT) comparing ESP and SAP to identify the best regional anesthesia catheter technique regardless of the pattern of rib fracture (anterior vs. posterior) and to allow adoption of a single technique to facilitate streamlined care. This knowledge gap represents an important opportunity to advance our understanding of the two established techniques in this trauma population.

Inclusion criteria

• Age >18;
• Traumatic rib fractures (unilateral or bilateral);
• Minimum of 3 rib fractures per side;
• Admitted to hospital for <72 hours
• NRS pain score > 4 at rest or with movement for chest pain at the time of eligibility assessment

Exclusion criteria

• Severe traumatic brain injury (Glasgow Coma Scale < 9);
• Surgery performed/planned within 72 hours of catheter infusion start;
• Uncontrolled coagulopathy;
• Skin infection or anatomical abnormality (i.e. open fracture) at insertion sites;
• Allergy to local anesthetic;
• Chronic high dose opioid use preadmission (Morphine Equivalent Dose > 30mg per day);
• Pregnancy;
• Acute respiratory failure requiring intubation at enrolment;
• Inability to comply with Intravenous Patient-Controlled Analgesia use;
• Contraindications to nerve blocks
• High likelihood of loss to follow-up