US Case of the Month: October
/The Case:
A male in his 20s with no past medical history presents to the Emergency Department with acute onset of right sided pleuritic chest pain. He states that he woke up this morning with mild right sided chest pain that progressed throughout the day to the point where he called EMS. Initial evaluation by EMS was reassuring but they recommended transport to the hospital. The patient elected to drive himself and on presentation to the ED he complained of 4/10 non-radiating, dull, right-sided chest pain. His pain was pleuritic in nature and was alleviated by rest. It was not exertional in nature. He denied associated nausea, diaphoresis, fevers, cough, congestion, shortness of breath. He has no family history of cardiac disease and denied any previous PE/DVTs, recent travel or surgeries, leg swelling, or hemoptysis.
Vitals: T 98.7 F, HR 78, BP 117/70, RR 21, O2 sat 96% on RA. Physical Exam: The patient was resting comfortably in bed with no signs of distress. His cardiac exam reveals a regular rate and rhythm with no murmurs, rubs, or gallops. His pulmonary exam reveals slightly diminished breath sounds on the right but was without any signs of respiratory distress, wheezing, or crackles.
A 12 lead EKG showed normal sinus rhythm with no signs of ischemia or arrhythmia. Due to the nature of his symptoms, a bedside echocardiogram and thoracic exam were obtained while awaiting additional workup.
Right anterior Superior Lung field
Left Anterior Superior Lung Field
What We see on ultrasound:
The echocardiogram reveals normal left ventricular function with no pericardial effusion or signs of right heart strain. Thoracic ultrasound reveals absent lung sliding in the right hemi-thorax. A chest x-ray confirmed a moderate sized pneumothorax without signs of tension. The patient subsequently underwent a serratus anterior block for chest tube placement.
The Serratus Anterior Plane Block
Anatomy
Sensation to the lateral chest wall is provided by the lateral cutaneous branches of the thoracic intercostal nerves, the target of the serratus anterior block. The intercostal nerves arise from the thoracic spinal nerves and travel adjacent to the intercostal vessels within the intercostal margin. As the intercostal nerve travels anteriorly around the thorax it branches, near the mid-axillary line, forming the lateral cutaneous nerve. The lateral cutaneous nerve promptly tracks superficially, traversing the intercostal muscles and serratus anterior muscle. After penetrating the serratus anterior, the lateral cutaneous nerve divides into anterior and posterior branches which innervate respective areas of the lateral thoracic wall. When performing the serratus anterior block, anesthetic is deposited just superficial to the serratus anterior muscle to engulf the lateral cutaneous nerves. As the patient subsequently respires, the anesthetic spreads along the fascial plane to the adjacent lateral cutaneous
nerves, providing anesthesia to multiple thoracic levels (1,2). Several studies have shown that a successful serratus anterior plane block in the ED can reduce, and even eliminate, the need for additional pain medication in patients with rib fractures or undergoing thoracostomy tube placement (3,4).
the procedure
Supplies needed:
1. High frequency linear probe
2. Sterile probe cover
3. Cleaning solution (Chlorhexidine or Betadine)
4. Sterile gloves
5. Surgical cap
6. Sterile towels
7. 20 cc syringe
8. Extension tubing
9. Echogenic 22g block needle
10. Anesthetic agent of choice
11. Intralipid (at minimum must be in the department before beginning the procedure)
Choice of anesthetic
Prior to starting any regional block, it is important to carefully consider which agent(s) you will want to use as and calculate the dose you will need. Below is a table showing some of the more common anesthetic agents and their associated doses.
Table 1: Anesthetic choices (adapted from Taming the SRU and Highland EM Ultrasound4 (5,6))
Procedure Details
Ensure that the patient is placed in a favorable position. While the serratus anterior block can be performed with the patient in the supine position (useful for patients with traumatic injuries), it is often much easier to perform this with the patient in the lateral decubitus position with the affected side up (7,8). Once the patient is positioned appropriately, perform an anatomy scan and identify your landmarks. In transverse orientation , place the probe along the mid axillary line at the level of the fifth rib. This will provide you with a view similar to the one below, with the serratus anterior muscle sandwiched between the fifth rib (deep) and the latissimus dorsi (superficial).
After confirming your landmarks, prep and drape the patient in the usual sterile fashion. Ensure a sterile probe cover is placed over the ultrasound probe. Prep the needle by flushing the tubing which connects it to the syringe of anesthetic. Obtain the view as described above and insert your needle in parallel to the ultrasound probe (so the needle will be in long axis) and visualize it entering the subcutaneous tissue. While keeping your needle in view, advance it until it enters the fascial plane formed between the serratus anterior and latissimus dorsi. Inject 1 cc of anesthetic solution to ensure you are in the correct space before injecting a full dose. With proper placement, you should see an anechoic collection just proximal to the muscle (as demonstrated in the clip below). While maintaining your view, slowly inject the remainder of your anesthetic solution.
Complications
One of the most feared complications with any regional block is local anesthetic systemic toxicity (LAST). It is important to have the patient on a monitor and carefully observe for any new changes during the procedure, as there should be a low threshold to abort and treat for LAST. Some of the more common signs and symptoms are shown below in Table 2.
Treatment includes the administration of 20% lipid emulsion, also known as intralipid (table 3).
Other uncommon but potential complications of the serratus anterior regional block include nerve injury, rebound pain, and pneumothorax.
Case Resolution:
The patient was successfully anesthetized with the serratus anterior block and tolerated the procedure well without additional pain medication or sedation. Post-procedure CXR showed resolution of his pneumothorax. The patient was admitted to the hospital and had an uncomplicated course. His chest tube was put to water seal the following morning and he was discharged within 24 hours without recurrence.
POST BY Shawn Hassani, MD
Dr. Hassani is a PGY-3 in Emergency Medicine at the University of Cincinnati
EDITING BY Jessica Baez, MD and Meaghan Frederick, MD
Dr. Baez is Fellowship Trained in Ultrasound, an Assistant Professor and Assistant Program Director of Emergency Medicine at the University of Cincinnati.
Dr. Frederick is a PGY-3 in Emergency Medicine at the University of Cincinnati.
References
Mayes, J., Davison, E., Panahi, P., Patten, D., Eljelani, F., Womack, J., & Varma, M. (2016). An anatomical evaluation of the serratus anterior plane block. Anaesthesia, 71(9), 1064-1069. doi:10.1111/anae.13549
Durant, E., Dixon, B., Luftig, J., Mantuani, D., & Herring, A. (2017). Ultrasound-guided serratus plane block for ED rib fracture pain control. The American Journal of Emergency Medicine, 35(1). doi:10.1016/j.ajem.2016.07.021
Jadon, A., & Jain, P. (2017). Serratus Anterior Plane Block-An Analgesic Technique for Multiple Rib Fractures: A Case Series. American J Anesth Clin Res, 3(1), 1-4.
Lin, J., Hoffman, T., Badashova, K., Motov, S., & Haines, L. (2020). Serratus anterior plane block in the emergency department: a case series. Clinical Practice and Cases in Emergency Medicine, 4(1), 21.
Regional Anesthesia. Retrieved August 21, 2020, from http://www.tamingthesru.com/regional-anesthesia
What med?. Retrieved August 21, 2020, from http://highlandultrasound.com/med-guide
Blanco, R., Parras, T., Mcdonnell, J. G., & Prats-Galino, A. (2013). Serratus plane block: A novel ultrasound-guided thoracic wall nerve block. Anaesthesia, 68(11), 1107-1113. doi:10.1111/anae.12344
Ultrasound-Guided Serratus Anterior Plane Block Can Help Avoid Opioid Use for Patients with Rib Fractures (2019, April 05). Retrieved August 21, 2020, from https://www.acepnow.com/article/ultrasound-guided-serratus-anterior-plane-block-can-help-avoid-opioid-use-patients-rib-fractures/2/
Golden, A. D., & Dickerson, D. (2018). Local Anesthetic Systemic Toxicity: Diagnosis, Prevention, and Management. Oxford Medicine Online. doi:10.1093/med/9780190271787.003.0043
Neal, J. M., Barrington, M. J., Fettiplace, M. R., Gitman, M., Memtsoudis, S. G., Mörwald, E. E., . ..Weinberg, G. (2018). The Third American Society of Regional Anesthesia and Pain Medicine Practice Advisory on Local Anesthetic Systemic Toxicity. Regional Anesthesia and Pain Medicine, 43(2), 113-123. doi:10.1097/aap.0000000000000720
