Direct application of ropivacaine-soaked gauze to sciatic nerve after necrotizing fasciitis exposes underlying muscles and nerves

Abstract

Background:

Necrotizing fasciitis is a rapidly progressive infection of the subcutaneous tissue and fascia with significant morbidity and mortality. There is a paucity of literature published on the benefits of regional anaesthesia in patients with necrotizing fasciitis of the extremities.

Case Presentation:

This study demonstrates novel approaches to management of pain in a patient with necrotizing fasciitis of the lower extremity. A 47-year-old male with polysubstance use disorder was found to have necrotizing fasciitis of the lower extremity. Surgical debridement included 15% of his total body surface area and resultant exposure of his sciatic nerve. A ropivacaine-soaked gauze was applied directly to the exposed sciatic nerve. Femoral and lateral cutaneous nerve blocks were performed to facilitate necessary surgical dressing changes and physical therapy.

Conclusion:

This report details techniques used in postoperative pain management to facilitate surgical dressing changes after extensive debridement of an extremity for necrotizing fasciitis. The use of local anaesthetic-soaked gauze may be a useful adjunct in certain scenarios.

Introduction

Necrotizing fasciitis, also known as necrotizing soft tissue infection (NSTI), is a rapidly progressive infection of the subcutaneous tissue and fascia which can quickly progress to bacteraemia, septic shock and multiorgan failure with estimated mortality rates of 20%. ¹ Prompt diagnosis and treatment are critical to reducing morbidity and mortality. ¹ Treatment includes antibiotic therapy and surgical debridement to provide source control. ¹

Surgical debridement often requires excision of tissue, fascia and overlying skin. This debridement exposes underlying muscles, nerves and other deeper structures typically shielded by soft tissue and skin. In patients who survive the initial infection, rehabilitation and wound healing in the setting of exposed muscles and nerves presents significant challenges in pain management. Pain control is further complicated by the extensive nature of the infection and the limited analgesic armamentarium that is available in the setting of hemodynamic instability and pressor requirements precipitated by the infection. Traditional pain regimens often include intravenous (IV) and oral opioids, anti-inflammatories, N-methyl-d-aspartate antagonists, alpha-2 agonists and others. Regional anesthesia can be a useful treatment modality when there is extremity involvement.

This report aims to describe (1) the use of regional anaesthesia in managing postoperative pain in necrotizing fasciitis of the lower extremity and (2) the novel application of a ropivacaine-soaked gauze to an exposed sciatic nerve.

Case presentation

A 47-year-old male with a history of polysubstance use disorder presented to the hospital with a swollen and erythematous left lower extremity (LLE) in the setting of fevers and general malaise (Figure 1). The patient reported that a few days prior to presentation, he was drinking alcohol and fell while exiting a parked truck causing injury to his left thigh. He reported progressive pain and swelling in that region. On examination, there was crepitus in the LLE and pain with passive range of motion. He was tachycardic, febrile and hypotensive. The general surgery service was consulted for evaluation and the patient was taken to the operating room (OR) emergently given the concerning findings for compartment syndrome. His intraoperative course was notable for extensive leg exploration and debridement, four compartment fasciotomy and thigh fasciectomy (Figure 2). Intraoperative wound and blood cultures were obtained, ultimately growing Escherichia coli. He was transferred to the surgical intensive care unit (SICU) for further haemodynamic monitoring. His postoperative course was complicated by worsening pressor requirements and progressive multiorgan system failure, ultimately requiring another debridement in the OR. In totality, approximately 15% of the patient’s total body surface area (TBSA) was debrided (Figure 2). After multiple days in the SICU, the patient was stabilized and extubated.

Figure 1.

Initial presentation to the emergency department.

Figure 2.

Initial exploration and debridement.

Upon extubation, the patient had significant pain in his LLE due to the extensive nature of his wounds. In addition, the patient required daily bedside dressing changes, which were poorly tolerated with traditional pain medication. As a result, the ICU team consulted the Acute Pain Service (APS) for help managing the patient’s periprocedural pain as dressing changes would be required daily for the next few weeks. The ICU team also discussed the possibility of having the patient return to the OR daily for dressing changes under general anaesthesia if APS was unable to provide further pain control. At the time, the patient was on a regimen that included acetaminophen 975 mg PO every 8 hours, hydromorphone 4 mg PO every 4 hours as needed, hydromorphone 2 mg IV every 2 hours as needed, methadone 10 mg IV every 8 hours scheduled and a ketamine infusion at 5 µg/kg/min. Despite this regimen, the patient continued to be in severe pain. This became a limiting factor in the patient’s ability to undergo dressing changes and participate in physical therapy to prevent contracture of his leg.

Upon inspection of the patient’s surgical wound, the sciatic nerve was directly visualized in the subgluteal region between his exposed gluteus maximus and femur (Figure 3). After informed consent was obtained from his healthcare proxy, we directly applied a gauze soaked in 20 mL of 0.5% ropivacaine with epinephrine 1:400,000 circumferentially around the sciatic nerve during a dressing change with the surgical team (Figure 4). This gauze was left in place for 24 hours, until the next dressing change. Under ultrasonic guidance, the femoral nerve was identified, and a needle advanced through the fascia lata and fascia iliaca, and 20 mL of 0.5% ropivacaine with 1:400,000 epinephrine was administered around the femoral nerve (Figure 5). Subsequently, the lateral femoral cutaneous nerve (LFCN) was anaesthetized using 15 mL of 0.2% ropivacaine with epinephrine 1:400,000 (Figure 6). The application of the local anaesthetic-soaked gauze and the traditional ultrasound-guided nerve blocks were repeated every 24 hours in coordination with the surgery team’s dressing change.

Figure 3.

Exposed sciatic nerve in the subgluteal region.

Figure 4.

Ropivacaine-soaked gauze wrapped circumferentially around sciatic nerve.

Figure 5.

Ultrasound-guided femoral nerve block; left image is the patient’s anatomy prior to injection of local anaesthetic, and right image is during injection of local anaesthetic.

Figure 6.

Ultrasound-guided lateral femoral cutaneous nerve block; left image is the patient’s anatomy prior to injection of local anaesthetic, and right image is during injection of local anaesthetic.

After the combination of the femoral nerve block, LFCN block and direct application of a ropivacaine-soaked gauze to the sciatic nerve, the patient had a significant improvement in pain. Subsequent dressing changes were performed at the bedside without the need for returning to the OR solely for dressing changes. On serial follow-up examinations, the patient reported improved pain scores, ranging from 4 to 6 out of 10 on the pain scale. This was a significant improvement from his prior pain ratings of 9–10 out of 10 on the pain scale. In addition, the surgical team noted dressing changes were easier to perform with less patient discomfort. The physical therapists also noted the patient was able to participate significantly more in his daily physical therapy regimen, a necessary part of his treatment to prevent contracture and reduction in range of motion.

Once his fevers resolved, white blood cell (WBC) count downtrended, and serial blood cultures remained negative, definitive management of his pain was performed with a lumbar epidural at the L3/L4 level (Figure 7).

Figure 7.

Lumbar epidural at L3/4 level.

Discussion

This is the first report to describe pain management techniques in a patient who underwent extensive debridement of his LLE resulting in an exposed sciatic nerve. We used a novel regional technique by circumferentially wrapping the exposed sciatic nerve with a ropivacaine-soaked gauze to alleviate pain and facilitate the patient’s dressing changes and participation in his recovery.

There is a paucity of literature describing pain management in patients with necrotizing fasciitis. ² Many patients require serial debridement and daily dressing changes over an extended duration as part of rehabilitation. In patients with extremity-associated necrotizing fasciitis, the extensive surface involvement presents significant challenges in pain control, but it also allows opportunities for alternative strategies to pain management.

With regard to this case report, various approaches were first weighed by the APS. First, the authors considered escalating the patient’s PO and IV regimen. However, given the patient’s critical illness, tenuous haemodynamics and ongoing pressor requirements, this option was deferred. Second, the authors considered a lumbar epidural. However, at the time of consultation, the patient was febrile with an elevated WBC count of 47,000, and blood cultures were positive for E. coli. Neuraxial anaesthesia, especially with catheter placement, is contraindicated in the setting of an active infection given the concern for spreading the infection to the central nervous system. ³ Ultimately, regional anaesthesia was felt to be the best option for this patient given the clinical constraints. The authors felt that regional blocks of the femoral nerve, LFCN and sciatic nerve were appropriate given the wound was restricted to one extremity. As described earlier, the femoral nerve and LFCN blocks were performed in the traditional manner with ultrasound guidance. However, the novelty of this case report lies in the anaesthetic management of the exposed sciatic nerve. The authors were able to directly visualize the exposed sciatic nerve and were able to cover it circumferentially with a ropivacaine-soaked gauze to effectively anaesthetize the nerve in the subgluteal region. Direct application of ropivacaine to the sciatic nerve allows for immediate diffusion of the local anaesthetic through the epineurium into the various layers of the sciatic nerve without the typical anatomic constraints, such as fascial planes, which can limit the diffusion of the anaesthetic and efficacy of the medication. ⁴ The authors hypothesize that the observed clinical efficacy may be in part owing to this proposed mechanism. There was an appropriate physiological response to this approach with clinically relevant reductions in pain and improvement in physical therapy participation.

In conclusion, this study highlights a novel pain management technique in a patient with extensive necrotizing fasciitis of the lower extremity. Although it is rare to directly visualize a peripheral nerve in clinical practice, this case report demonstrates the viability of direct application of a local anaesthetic-soaked gauze to a peripheral nerve. In select patients, under certain scenarios, the use of a local anaesthetic-soaked gauze may be a useful adjunct to traditional regional techniques.