Serratus Anterior Plane Block for Clinically Suspected Rib Fractures in Prehospital and Retrieval Medicine

Abstract

Objective: To describe the use of the serratus anterior plane block (SAPB) in the prehospital and retrieval environment including the ability to accurately identify those patients with thoracic trauma and clinically suspected rib fractures who would benefit from this procedure. Methods: This is a retrospective case series of all patients with thoracic trauma and clinically suspected rib fractures who received SAPB by a prehospital and retrieval medical team in New South Wales, Australia, between 2018 and 2021. The primary outcome was to identify the proportion of patients who received appropriate blocks based on the criteria of reporting moderate pain after receiving adequate pre-block analgesia. Secondary outcomes included the proportions of patients with rib fractures identified on thoracic imaging, concomitant time-critical pathology, radiologist identification of fluid adjacent to the serratus anterior muscle, and local anesthetic systemic toxicity. Results: Of the 2004 patients who sustained thoracic trauma, only 13 received a SAPB. Nine (69.2%) met the predetermined definition of appropriate selection. Of the four patients who did not meet this criteria, three reported less than moderate pain and one did not receive adequate pre-block analgesia. There was no significant effect on median scene interval when compared to other thoracic trauma patients who did not receive a SAPB. Ten patients had rib fractures identified on in-patient imaging (chest x-ray or computed tomography (CT)) with a median (IQR) number of ribs fractured of 5 (interquartile range 2–10). Three of these patients had radiological flail segments. Prespecified time-critical pathology was identified in three patients (23.1%) on initial hospital imaging. Five out of eight patients with post-SAPB CT imaging (62.5%) available for radiologist review had fluid identified adjacent to the serratus anterior muscle. None of the 13 patients had local anesthetic systemic toxicity. Conclusion: The SAPB can be safely and successfully performed in the prehospital and retrieval environment, where clinicians can appropriately identify patients with thoracic trauma and clinically suspected rib fractures who would benefit from this technique. Further research is required to identify the ideal patient population to perform the SAPB upon and compare its performance to current analgesic options.