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Deep Serratus Plane Catheter for Management of Acute Postthoracotomy Pain After Descending Aortic Aneurysm Repair in a Morbidly Obese Patient: A Case Report

George, Renuka, M., MD; Yared, Maria, MD; Wilson, Sylvia, H., MD

doi: 10.1213/XAA.0000000000000628
Case Reports
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Regional procedures for postthoracotomy pain control have classically focused on paravertebral blocks and thoracic epidurals; however, these techniques may be challenging in an increasingly obese population and contraindicated with numerous anticoagulant and antiplatelet agents. While less studied, truncal blocks allow analgesic intervention for this growing patient cohort. This case report describes placement of a deep serratus anterior plane catheter in an intubated, morbidly obese patient with a lumbar drain who failed extubation secondary to acute postthoracotomy pain. The serratus plane catheter facilitated extubation and adequate analgesia without prohibiting anticoagulant use or interfering with the monitoring of spinal cord function.

From the Department of Anesthesia and Perioperative Medicine, Medical University of South Carolina, Charleston, South Carolina.

Accepted for publication August 3, 2017.

Funding: Departmental.

The authors declare no conflicts of interest.

Address correspondence to Renuka M. George, MD, Department of Anesthesia and Perioperative Medicine, Medical University of South Carolina, 167 Ashley Ave, Suite 301 MSC 912, Charleston, SC 29425. Address e-mail to georgere@musc.edu.

Acute postthoracotomy pain can be associated with impaired respiratory function, prolonged intubation and intensive care unit (ICU) stay, and potential development into chronic pain.1 Aggressive acute pain management not only alleviates pain and increases patient satisfaction, but it also accelerates patient recovery and mobilization. This promotes faster return to preoperative functional status, which may decrease health care costs. While thoracic epidurals and paravertebral nerve blocks are traditionally used to manage postthoracotomy pain, both may be limited by anticoagulants, positioning, and patient comorbidities.1 Superficial and deep serratus anterior plane blocks are recently described truncal blocks that may provide a less invasive regional anesthesia approach for thoracic analgesia.2,3 We present a case of postthoracotomy pain resulting in reintubation of a morbidly obese patient with a lumbar drain that was successfully treated with a deep serratus plane catheter.

The patient provided written consent for publication of this case.

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CASE REPORT

A 43-year-old morbidly obese woman (111.13 kg; body mass index, 43.4 kg/m2) with 10 pack-year smoking history presented for an aortic arch and proximal descending aortic aneurysm repair. She had a prior repair for coarctation of the aorta with a Dacron patch at 7 years of age, which was now complicated by the development of an asymptomatic 4.1-cm fusiform aneurysmal dilation of the proximal descending aorta just distal to the left subclavian artery. The anatomy on computed tomography scan was deemed unsuitable for endovascular stent graft. Preoperative left heart catheterization and echocardiogram were unremarkable.

Intraoperative course included a general anesthetic with double lumen endotracheal tube for lung isolation, arterial line, central line, and a lumbar spinal drain. A graft was placed in her transverse arch with reimplantation of the left subclavian artery under cardiopulmonary bypass (45- minute pump time; 40-minute cross-clamp time). Heparin was reversed with a final activated clotting time of 121. Intraoperatively, she received rocuronium for paralysis with sugammadex (400 mg) for reversal, while fentanyl (1000 µg intravenous) and hydromorphone (1 mg intravenous) were administered for analgesia over 5 hours. The patient was hemodynamically stable without vasopressor or inotropic support and met all extubation criteria on emergence. However, shortly after extubation, shallow tidal volumes attributed to inadequate pain control resulted in splinting and hypercapnic respiratory failure requiring urgent reintubation.

In the ICU, the regional anesthesia service was consulted for possible analgesic interventions to facilitate extubation. Epidural placement was not ideal given her recent therapeutic heparin dose, lumbar drain, and inability to cooperate or communicate from sedation. Her body habitus, which obscured landmark and ultrasound visualization, also would have made both epidural and paravertebral blocks technically challenging. Since the majority of her pain was presumed to be from her left chest wall secondary to her thoracotomy and chest tube sites, a left-sided deep serratus plane catheter was placed for analgesia.

Utilizing the technique outlined by Blanco et al,3 the patient was positioned supine with the left arm abducted overhead while a linear high-frequency ultrasound probe (10–12 MHz) was placed along the midaxillary line. Serratus anterior muscle, fourth and fifth ribs, intercostal muscles, and parietal pleura were identified (Figure 1). Under sterile technique, a 17-gauge, 8.5-cm Tuohy needle was inserted in-plane (cephalad to caudad) to a depth of 8 cm. Local anesthetic (20 mL, ropivacaine 0.5%) was injected deep to the serratus anterior muscle, elevating it from the ribs, and a 19-gauge catheter was secured at 16 cm and an infusion started (ropivacaine 0.2%, 8 mL/h).

Figure 1

Figure 1

Shortly after block placement, the ICU team changed her ventilation settings from pressure-regulated volume control to pressure support, and the patient comfortably achieved similar tidal volumes (473 vs 411 mL). Although her pain control appeared to improve with block placement, the critical care team decided to keep her intubated overnight after her failed extubation attempt, attributed to atelectasis on imaging, overhydration requiring diuresis, and morbid obesity.

Table

Table

Figure 2

Figure 2

Chest x-ray demonstrated improved atelectasis at 6 AM on postoperative day (POD) 1 (Figure 2). On assessment by the regional team before extubation, the patient was alert, cooperative, and able to communicate that her pain was controlled. On evaluation to pinprick, she had decreased sensation and adequate analgesia from T2 to T5. Although this covered the thoracotomy incision, she continued to have pain at the chest tube site, located slightly anterior to the midaxillary line between ribs 6 and 7, along the T7 dermatome. The catheter infusion rate was increased without bolusing over the course of POD1 (10 then 12 mL/h) and dermatomal spread improved to T2–7. After diuresis and the increase in infusion rate to cover the chest tube site, she was successfully extubated, (approximately 24 hours after reintubation and 19.5 hours after nerve block placement). She required minimal postoperative opiates (Table) and took acetaminophen 650 mg every 6 hours as needed. The lumbar drain was removed on POD2, and the patient was noted to be moving all 4 extremities equally. On POD3, the ropivacaine infusion was paused, but the patient developed uncontrolled pain at the chest tube site. Pain was relieved by restarting the local anesthetic infusion (12 mL/h without bolus), and this was continued until chest tube removal on POD4. The patient was discharged home on POD5. Notably, before discharge, she was diagnosed with left vocal cord dysfunction secondary to left recurrent laryngeal nerve injury sacrificed during the aortic aneurysm repair. Additionally, chart review of clinic notes revealed an uneventful postoperative course without complaint of chronic postthoracotomy pain at 2 months postdischarge.

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DISCUSSION

Early postextubation respiratory failure after thoracotomy is often multifactorial. One lung ventilation and inadequate reexpansion of the collapsed lung increases oxygen requirements and decreases pulmonary compliance, functional residual capacity, pulmonary blood flow, and carbon dioxide elimination.4 Although opiates help manage pain, they also decrease ventilatory response to hypoxia and hypercarbia.5 Thoracotomy patients have an increased incidence of postoperative pulmonary complications, length of stay, and time in high dependency units compared to patients undergoing video-assisted thoracoscopic surgery.6 Managing acute postthoracotomy pain is important in aiding recovery of respiratory mechanics and facilitating return to baseline functional status. The combination of splinting secondary to pain, upper airway obstruction from unrecognized vocal cord injury, restrictive lung disease from morbid obesity, and atelectasis during 1-lung ventilation likely all contributed to our patient requiring reintubation. Both operating room and ICU teams felt that thoracotomy pain was the main cause of this patient’s postextubation respiratory failure.

While epidurals and paravertebral blocks are most commonly used to alleviate postthoracotomy pain and facilitate extubation,1 their utilization may be limited by obesity, anticoagulants, and the need for unambiguous neurological assessment by ICU nurses. Individual intercostal nerve blocks are another possible regional option. They are less ideal because they require multilevel injections or multiple catheters for effective long-term pain control. Thus, the decision was made to place a deep serratus anterior plane catheter for maximum benefit and minimal risks. The serratus anterior muscle originates from ribs 1 to 8 and inserts along the medial border of the scapula. A relatively novel technique, the serratus plane block provides thoracic anesthesia or analgesia by targeting the lateral cutaneous branches of the intercostal nerves from T2 to T9 as they traverse the serratus anterior muscle.2,3,7,8 Benefits of this technique include supine positioning and superficial location with easy visualization under ultrasound regardless of body habitus. The superficial location also permits continuation of anticoagulants for block placement and catheter removal with relative safety. This is particularly ideal after aortic graft placement, because aortic grafts increase the risk of both thrombocytopenia and graft thrombosis, the latter of which may necessitate therapeutic anticoagulation.

Although initially evaluated in healthy volunteers for chest wall analgesia,3 other indications have more recently appeared in the literature.2,7,8 Randomized studies have not compared the deep serratus anterior plane catheter to other truncal techniques, such as paravertebral blocks or epidurals. However, its utility is supported by our case presentation. Our patient experienced improved analgesia that facilitated atelectasis resolution on chest x-ray (Figure 2) and successful extubation. Its effectiveness was also supported by numbness to pinprick on physical examination, low opiate consumption, and adequate pain scores throughout her hospitalization after extubation (Table). Further, when the catheter infusion was paused, the patient experienced uncontrolled pain, which quickly resolved after restarting the infusion. Because pain is exacerbated by activity, the regional catheter facilitated ambulation on POD2, while minimizing opiate consumption and consequent sedation. Thus, the serratus plane catheter played an important role in providing analgesia for both thoracotomy and chest tube pain.

Information is limited regarding the superiority of a superficial versus deep serratus plane block. Blanco et al3 found that loss of pinprick sensation was comparable in both blocks (T2–T9). However, both the sensory and motor blocks (long thoracic nerve) were prolonged in the superficial serratus anterior block (752 and 778 minutes, respectively) compared to the deep block (386 and 502 minutes, respectively).3 More recently, Piracha et al9 reported improved analgesia and duration (3 weeks to 4 months) with the deep serratus plane block while sparing the long thoracic nerve in patients with chronic postmastectomy pain. The authors theorized that when scar tissue exists between the serratus anterior and latissimus dorsi muscles, local anesthetic spread, duration, and efficacy are less predictable with the superficial serratus plane block. Notably, Piracha et al9 added methylprednisolone to the local anesthetic, while Blanco et al3 used plain local anesthetic. The deeper approach may have other benefits including easier sonographic identification and decreased catheter movement since it traverses more muscle tissue (Figure 1). Although there are case reports of using serratus plane blocks for rib fractures and acute postthoracotomy pain, prospective studies comparing superficial and deep serratus plane blocks are lacking.2,7,8

Currently, epidurals and paravertebral blocks are the gold standard for effective pain control for chest wall surgery.1 Both of these techniques can confound postoperative neuromonitoring and be limited by body habitus, positioning, and use of anticoagulants. Although further prospective investigations are warranted to explore its efficacy, reliability, and analgesic potential, the deep serratus anterior plane block may prove to be an attractive alternative in the interim, when traditional regional anesthesia options are less feasible or contraindicated.

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DISCLOSURES

Name: Renuka M. George, MD.

Contribution: This author helped write the manuscript.

Name: Maria Yared, MD.

Contribution: This author helped write the manuscript.

Name: Sylvia H. Wilson, MD.

Contribution: This author helped write the manuscript.

This manuscript was handled by: Raymond C. Roy, MD.

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REFERENCES

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3. Blanco R, Parras T, McDonnell JG, Prats-Galino A. Serratus plane block: a novel ultrasound-guided thoracic wall nerve block. Anaesthesia. 2013;68:1107–1113.
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8. Fu P, Weyker PD, Webb CA. Case report of serratus plane catheter for pain management in a patient with multiple rib fractures and an inferior scapular fracture. A A Case Rep. 2017;8:132–135.
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