Ultrasound-guided serratus anterior plane (SAP) block is a relatively new technique that provides analgesia for thoracic wall surgeries by blocking the lateral branches of the intercostal nerves (T2–L2).1 The procedure has been largely discussed for managing pain after breast surgery, and new interest has arisen for the treatment of thoracic trauma, specifically rib fractures. Inadequate pain management of rib fractures causes significant morbidity and mortality of rib fractures, particularly the development of pneumonia.2 Patients attempt to limit rib movement with smaller tidal volumes and do not cough adequately, which predisposes to atelectasis and abnormal mucous secretion clearance. The incidence of pneumonia in hospitalized patients with 1 or more rib fractures is approximately 6%.3 In 2 retrospective studies, the incidence of pneumonia was especially higher in elderly patients (≥65 years old) with rib fractures at 31% and 34%.4,5 By adequately treating thoracic pain in patients with rib fractures, we not only provide symptomatic relief, but also improve respiratory mechanics and in turn potentially decrease the risk of significant morbidity and mortality in these patients.
There are various strategies for pain control in patients with rib fractures, including intravenous (IV) narcotics and nonsteroidal anti-inflammatory drugs (NSAIDs), continuous epidural infusion, paravertebral block, intrapleural infusion, and intercostal nerve block.6 Current guidelines for blunt thoracic trauma with level I recommendations are the use of thoracic epidural analgesia for patients who do not have any contraindications.7 For those not suitable for an epidural, parenteral opioids administered IV or via patient-controlled analgesia (PCA) with NSAID supplementation are the next option. However, in patients who have contraindications to any of these methods, local anesthetic regional blocks are a remaining option. The following is a case report of a patient with multiple rib fractures who received pain relief from an SAP catheter.
The patient was a 98-year-old, 67-kg woman with hypertension, dementia, seizure disorder, and atrial fibrillation with unknown anticoagulation status who presented to the emergency department (ED) after a mechanical fall at her assisted living home. The fall occurred approximately 5 days before initial ED presentation, and since then she had been reporting right shoulder, arm, and right chest wall pain. Initially, the assisted living staff observed her, but when she developed worsening pain and a change in her mental status, she was brought to the ED.
On arrival to the ED, the patient was hypothermic (body temperature 34.2°C), hypotensive to 80/48 mm Hg, with a heart rate of 68 beats per minute, and an oxygen saturation of 96% on room air. On physical examination, there was no evidence of trauma to the head or neck. Despite her dementia, she was alert and oriented to person, place, and time and reported excruciating pain in her right upper extremity and hemithorax. She reported a pain level of 8 on the numerical rating scale (NRS). She had severely limited range of motion of her right upper extremity secondary to pain. Her basic metabolic panel and complete blood count were within normal limits. However, her coagulation studies were noticeably prolonged: prothrombin time 21.7 seconds (11–14 seconds), partial thromboplastin time 49.1 seconds (25–35 seconds), and international normalized ratio 2.0 (0.8–1.2). Electrocardiogram revealed atrial fibrillation with a ventricular rate of 63 beats per minute and no other abnormalities. She received a 1-L crystalloid solution, which normalized the blood pressure, and she was actively rewarmed.
Radiologic studies were performed with computed tomography of the head and neck negative for any trauma. Chest x-ray revealed a “mild opacity in the right mid chest which could reflect pneumonia or contusion. No pleural effusions. No pneumothorax. Several fractures of the lateral right ribs are identified.” Computed tomography of the thorax with IV contrast revealed “inferior right scapular fracture with surrounding hematoma. Multiple right upper lateral thoracic rib fractures again noted.” Orthopedic surgeons were consulted, confirming the fractures of the second through fifth ribs and the inferior pole of the right scapula. However, no acute surgical intervention was indicated, and the plan was for a right upper extremity sling for comfort, physical therapy, and pain control.
By hospital day 1, the patient remained in significant pain uncontrolled with IV opioids and a lidocaine patch. She had received 8 mg morphine IV in her 16-hour hospital course thus far. However, her pain was essentially unchanged (NRS 7) and located primarily in her right hemithorax, corresponding to the site of her rib fractures. Thus, the Anesthesia Pain Service was consulted for symptom management. The patient’s clinical status had changed in terms of altered mental status, specifically with intermittent periods of agitation, restlessness, and somnolence, consistent with delirium. The most likely etiology was the combination of sedating opioids, quetiapine given by the primary team, and her baseline dementia. Because of her altered mental status, she was not a good candidate for a PCA regimen. Given her prolonged clotting times, thoracic epidural and paravertebral analgesia were contraindicated. We discussed the risks and benefits of an interscalene nerve block (to facilitate positioning of her arm) and an SAP catheter with her health care proxy and obtained consent. Our goal was to administer little to no IV opioid for the procedure to prevent potential exacerbation of her altered mental status.
The patient was placed in the supine position with the head of the bed elevated approximately 30°. Standard American Society of Anesthesiologists monitors were placed, and oxygen was provided via a nasal cannula. Because of her delirium, it was decided that sedation with small doses of fentanyl and propofol would provide the safest conditions to perform the procedure. Midazolam was not administered because of age and altered mental status. Fentanyl at 50 μg followed by 20 mg propofol was given IV for sedation. As expected, the patient was unable to move her right upper extremity secondary to pain. To gain proper field access but to minimize the amount of procedural sedation, a right interscalene nerve block was performed under sterile conditions with 10 mL mepivacaine 1.5%. The patient obtained immediate pain relief in her shoulder, which facilitated the positioning of her right upper extremity out of the field for SAP catheter placement.
With the patient remaining in a supine position, we placed a linear ultrasound transducer (Philips SonoSite M-Turbo) sagittally over the right midclavicular thorax and located the fourth and fifth ribs. While scanning laterally to the midaxilla, the serratus anterior muscle and overlying latissimus dorsi muscle were identified (Figure). Using sterile technique, a 17-gauge, 3-inch Tuohy needle was advanced between the latissimus dorsi and the serratus anterior muscle. The plane was opened with hydrodissection using sterile saline. A 19-gauge peripheral nerve catheter was then easily threaded into the space. The Tuohy needle was withdrawn into the latissimus dorsi, and the catheter was then threaded to secure it within the muscle. The Tuohy needle was removed, and the catheter was secured in place at 13 cm from the skin. Despite her prolonged clotting times, there was no excess bleeding or hematoma formation. A total of 40 mL ropivacaine 0.25% was administered through the catheter with intermittent negative aspiration every 5 mL. A continuous infusion of 0.2% bupivacaine at 10 mL/h was then initiated. She tolerated the procedure well, with immediate symptomatic relief, and was admitted to the surgical intensive care unit for further monitoring because of possible pulmonary contusion from her rib fractures. After catheter placement, her NRS score decreased from 7 to 0.
On hospital day 2 (catheter day 1), the patient self-reported “pain well controlled at rest, worse with repositioning.” Her pain with movement was localized to her shoulder injury, which was expected, because an SAP catheter would not provide relief in that anatomic region. However, she was able to breathe without any splinting, which was the primary goal of the SAP catheter. She had not required IV opioids in over 24 hours; her delirium had resolved. In addition, she began to tolerate oral intake and denied any nausea, vomiting, or pruritus. On examination, she had decreased sensation from T2 to T7 on the side of the catheter. There was still no evidence of hematoma formation. She was discharged from the surgical intensive care unit on hospital day 3 (catheter day 2) to the floor. On hospital day 4, she continued to do well in terms of pain control, and the infusion was held, but the catheter was left in place. She was transitioned to an oral pain medication regimen of 5 to 10 mg oxycodone every 4 hours as needed for moderate to severe pain and 650 mg acetaminophen every 6 hours. Of note, she did not require any oral opioid medication because her pain was well controlled solely by acetaminophen. By hospital day 5, the catheter was removed, and she was discharged from the hospital with an NRS score of 0.
Our patient was an elderly woman with altered mental status (secondary to baseline dementia exacerbated by polypharmacy) and prolonged clotting times, who presented after a mechanical fall resulting in an inferior scapula fracture and multiple rib fractures. She had failed standard multimodal analgesia with NSAIDs, opioids, and a lidocaine patch. She was referred to the Anesthesia Pain Service for further management. Because of her mental status, PCA was not an ideal option, and thoracic epidural and paravertebral analgesia was not an option because of her prolonged clotting times. Furthermore, the patient refused to move from the supine position, which would make neuraxial or paravertebral analgesia impossible. Therefore, we opted for the SAP catheter placement.
The SAP block evolved from the Pec I and Pec II block by Blanco et al1 in 2013. In their study, 4 female volunteers underwent an SAP single-shot block and achieved dermatomal coverage of the intercostal nerves from T2 to T9. We performed the technique as detailed by Blanco et al, scanning along the midaxilla and locating the fourth and fifth ribs. After locating the latissimus dorsi and the serratus anterior muscle, we used real-time ultrasound guidance to aim the bevel of the Tuohy needle in between these muscles and placed our catheter in this location. In the limited study by Blanco et al, they found a longer duration of effect and greater spread of local anesthesia with superficial injection to the serratus anterior muscle versus deep injection underneath the serratus anterior muscle. Thus, we opted to place the catheter superficial to the serratus anterior muscle.
Because the use of SAP catheters is a relatively new technique, there are no studies detailing the optimal local anesthetic dosing for SAP catheter infusions. A literature review reveals case reports with largely varying doses and types of local anesthetics.8–11 To date, there are 2 relevant case reports. The first, by Madabushi et al,8 involved an SAP catheter for a patient with postthoracotomy pain. In that case report, the clinicians obtained adequate analgesia without adverse effects with an initial injection of 6 mL lidocaine 1% and a continuous infusion of 0.1% bupivacaine with 1 μg/mL fentanyl at 7 mL/h.8 In the second case report by Kunhabdulla et al,12 the authors obtained adequate analgesia with an initial injection of 20 mL bupivacaine 0.125% followed by a continuous infusion of 0.0625% bupivacaine with 1 μg/mL fentanyl at 12 mL/h. We opted for a higher concentration infusion dose of bupivacaine 0.2% and decided to forego any opioids because of her mental status. Our initial bolus dose of 40 mL ropivacaine 0.25% (100 mg total) was calculated to be well below the generally accepted maximum doses for ropivacaine of 2 to 3 mg/kg (134–201 mg for her weight of 67 kg). We assumed that the local anesthetic absorption with the SAP technique was most similar to that of intercostal blocks, which are known to produce the highest serum local anesthetic concentration of all regional techniques. Although the exact toxic plasma levels of ropivacaine in humans are not well characterized, the clinical study by Kopacz et al13 involving ropivacaine intercostal blocks showed no signs of central nervous or cardiovascular toxicity in patients who weighed 63.6 to 80.4 kg and received 56 mL ropivacaine 0.25% (140 mg). Thus, we assumed our ropivacaine dose of 100 mg in a 67-kg patient to be reasonably safe while still effective.
Pain management is a crucial component of effectively decreasing the morbidity and mortality of patients with multiple rib fractures. Ultrasound-guided SAP catheters are a novel and effective technique in providing pain relief in unilateral multiple rib fractures in patients with altered mental status and/or abnormal clotting times. The future of SAP catheters is promising because there are advantages over the currently recommended neuraxial techniques for patients with rib fractures such as the ease of performing these techniques under ultrasound guidance, the ability to perform on patients on anticoagulation therapy, and the avoidance of sympathetic blockade. However, further studies should be performed to more clearly define optimal catheter placement, dosing regimens, pharmacokinetics of local anesthesia placed in the serratus anterior fascial plane, and effectiveness compared with other treatment modalities.
Name: Peter Fu, MD.
Contribution: This author helped complete the manuscript.
Name: Paul D. Weyker, MD.
Contribution: This author helped complete the manuscript.
Name: Christopher A. J. Webb, MD.
Contribution: This author helped complete the manuscript.
This manuscript was handled by: Hans-Joachim Priebe, MD, FRCA, FCAI.
1. Blanco R, Parras T, McDonnell JG, Prats-Galino A. Serratus plane block: a novel ultrasound-guided thoracic wall nerve block. Anaesthesia. 2013;68:11071113.
2. May L, Hillermann C, Patil S. Rib fracture management. Br J Anaesth Educ. 2015;16:2632.
3. Brasel KJ, Guse CE, Layde P, Weigelt JA. Rib fractures: relationship with pneumonia and mortality. Crit Care Med. 2006;34:16421646.
4. Bulger EM, Arneson MA, Mock CN, Jurkovich GJ. Rib fractures in the elderly. J Trauma. 2000;48:10401046.
5. Bergeron E, Lavoie A, Clas D, et al. Elderly trauma patients with rib fractures are at greater risk of death and pneumonia. J Trauma. 2003;54:478485.
6. Ho AM, Karmakar MK, Critchley LA. Acute pain management of patients with multiple fractured ribs: a focus on regional techniques. Curr Opin Crit Care. 2011;17:323327.
7. Simon BJ, Cushman J, Barraco R, et al.; EAST Practice Management Guidelines Work Group. Pain management guidelines for blunt thoracic trauma. J Trauma. 2005;59:12561267.
8. Madabushi R, Tewari S, Gautam SK, Agarwal A, Agarwal A. Serratus anterior plane block: a new analgesic technique for post-thoracotomy pain. Pain Physician. 2015;18:E421E424.
9. Khemka R, Chakraborty A, Ahmed R, Datta T, Agarwal S. Ultrasound-guided serratus anterior plane block in breast reconstruction surgery. A A Case Rep. 2016;6:280282.
10. Broseta AM, Errando C, De Andrés J, Díaz-Cambronero O, Ortega-Monzó J. Serratus plane block: the regional analgesia technique for thoracoscopy? Anaesthesia. 2015;70:13291330.
11. Bhoi D, Pushparajan HK, Talawar P, Kumar A, Baidya DK. Serratus anterior plane block for breast surgery in a morbidly obese patient. J Clin Anesth. 2016;33:500501.
12. Kunhabdulla NP, Agarwal A, Gaur A, Gautam SK, Gupta R, Agarwal A. Serratus anterior plane block for multiple rib fractures. Pain Physician. 2014;17:553555.
13. Kopacz DJ, Emanuelsson BM, Thompson GE, Carpenter RL, Stephenson CA. Pharmacokinetics of ropivacaine and bupivacaine for bilateral intercostal blockade in healthy male volunteers. Anesthesiology. 1994;81:11391148.