A 57 yo F with no relative PMH who presented to the ED one day after experiencing a sudden onset, right anterior chest pain after leaning over into her deep freezer. The pain was sudden onset, not relieved with Tylenol, and made it difficult to take a deep breath as well as sleep the night prior. On physical exam, the patient was uncomfortable, with minimal movement She was tachycardic but otherwise vitals wnl. She had tenderness across her right anterior chest at approximately the 6th or 7th rib. A rib series X-ray was suggestive of a minimally displaced acute fracture of the right anterior 7th rib without a pneumothorax. Despite pain medications, the patient remained in debilitating pain and the ultrasound team was called into action!
Serratus Anterior Block:
Anesthetic can be delivered to either of two locations; either the superficial plane between the latissimus dorsi and the serratus anterior muscles; or the deep plan below the serratus anterior muscle, just above the ribs and intercostal muscles. The deep plane is typically preferred as it can deliver anesthetic directly to the rib near the fracture location, thus increasing anesthetic effects. However, it is also more difficult to reach, especially in patients with large habitus, and has higher risk of secondary injury due to closer proximity to the pleural space. To help reduce this risk, the rib can be used as a “backstop” to help prevent the needle from entering pleura. This can be a very effective way to provide pain relief as Figure 1 below demonstrates the target anatomy.
Figure 1
After identifying the location. A needle specific for ultrasound guided nerve blocks with more echogenicity was utilized in plane with the linear probe in a transverse orientation. The needle was slowly advanced with 1cc of Bupivacaine delivered to the skin surface for initial anesthetic before advancing the needle into deeper layers. Hydro-dissection with saline was done at each plane encountered to verify needle location as well as separate planes for easier viewing and targeting. While the deep plane below the serratus anterior was the original target, the patient’s habitus and needle length was unable to reach the deep plane. Therefore, the superficial plane between the serratus anterior and latissimus dorsi was visualized. Bupivacaine Liposome (Exparel), which can be expected to give 48-72 hrs of relief, was injected into this plane without complication.
Within 5-10 minutes, the patient began to feel immediate relief of her excruciating pain. When the primary team reassessed her shortly thereafter, the patient was almost jumping up and down with relief. She experienced no pain and no dyspnea. On a follow-up phone call 3x days later, the patient continued to endorse being pain-free and was amazed at her remarkable turnaround. This case was a perfect example of the extraordinary benefits that a serratus anterior nerve block can provide.
For a detailed step-by-step video on performing a serratus anterior nerve block please watch the following video:
Resources:
1. Bansidhar BJ, Lagares-Garcia JA, Miller SL. Clinical rib fractures: are follow-up chest X-rays a waste of resources?. Am Surg. 2002;68(5):449-453.
2. Gilbertson J, Pageau P, Ritcey B, et al. Test Characteristics of Chest Ultrasonography for Rib Fractures Following Blunt Chest Trauma: A Systematic Review and Meta-analysis. Ann Emerg Med. 2022;79(6):529-539. doi:10.1016/j.annemergmed.2022.02.006
3. Serra, S., Santonastaso, D.P., Romano, G. et al. Efficacy and safety of the serratus anterior plane block (SAP block) for pain management in patients with multiple rib fractures in the emergency department: a retrospective study. Eur J Trauma Emerg Surg(2024). https://doi.org/10.1007/s00068-024-02597-6
