Inguinal hernia repair is a very common outpatient surgical procedure. The use of either preoperative ilioinguinal nerve block or postoperative local anesthetic infiltration is widely accepted to minimize postoperative pain.
Liposomal bupivacaine, a novel long-acting local anesthetic, has found widespread use after its introduction to the U.S. market in 2011 for wound infiltration. Liposomal bupivacaine is a formulation of the amide-type local anesthetic bupivacaine that is encapsulated in multivesicular liposomes. Bupivacaine is released from these multivesicular liposomes over time into the surrounding tissue. Liposomal bupivacaine is currently approved in the United States for injection into the surgical site. Because this medication has not been extensively studied, and expanded clinical use continues, new complications may occur.
We report a case of prolonged femoral nerve palsy secondary to liposomal bupivacaine use during surgical wound infiltration after inguinal herniorrhaphy.
The patient was contacted and gave written consent to review and publish this case report.
A 63-year-old man (weight, 81 kg; height, 180 cm; and American Society of Anesthesiologists physical status II) underwent an uneventful open right inguinal hernia repair with mesh under general anesthesia in an ambulatory surgery center. Before skin closure, the surgeon diluted 266 mg liposomal bupivacaine to a total volume of 40 mL with normal saline. The surgeon then infiltrated the subcutaneous tissue around the incision with 20 mL using a 3.8-cm 22-gauge needle and then injected 20 mL medial to the anterosuperior iliac spine performing a blind ilioinguinal nerve block.
Approximately 2 hours into the recovery period, the patient was unable to ambulate secondary to right leg weakness. On examination, the patient had numbness over the anterior and lateral thigh and over the medial aspect of the lower extremity. He was unable to extend his knee against gravity while thigh adduction and hip flexion were intact. These deficits appeared consistent with femoral and lateral femoral cutaneous nerve blockade.
Ultrasound imaging was used to evaluate the inguinal region, and local anesthetic spread was visualized around the femoral nerve (Fig. 1).
The patient was given a knee immobilizer and a walker to help with ambulation and discharged home after extensive counseling on fall precautions. He was then closely followed with a daily phone call to assess resolution of the palsy.
The patient reported that at 27 hours after infiltration, he noticed a gradual receding of the anterior thigh numbness and felt close to sensory baseline at 45 hours. He reported being able to extend his knee against gravity at 27 hours, ambulate without assistance at 35 hours, and subjectively had full quadriceps function at 51 hours. Ultimately, his nerve palsy had full resolution with no further sequela noted at 6-month follow-up.
Inadvertent transient femoral nerve palsy (TFNP) is a rare but known complication after local wound infiltration or ilioinguinal block for inguinal herniorrhaphy.1–5
The incidence of inadvertent TFNP is unknown but has been reported between 0.1% and 9% in the literature. Berliner6 reported a personal experience of 4384 adult inguinal herniorrhaphies under local anesthetic with 5 cases of TFNP (0.1% incidence). Erez et al.7 reported an incidence of 0.2% in 2624 groin operations in children. Ghani et al.8 reported an incidence of 6% in 99 percutaneous blocks and 4% during surgical visualization. Finally, Lipp et al.9 reported an incidence of 8.8% in 182 ilioinguinal blocks in children. This range in incidence is likely related to different block techniques.
A cadaveric study on the mechanism of TFNP after ilioinguinal block demonstrated continuity of the plane deep to the transverse abdominis muscle and the plane below the fascia iliacus, which contains the femoral nerve.10 The authors of this cadaveric study suspect that injection deep to the transverse abdominis muscle allows tracking of local anesthetic to the femoral nerve. In our case, the blind approach performed by the surgeon and the large volume of liposomal bupivacaine injected likely caused spread to the femoral nerve.
Using ultrasound imaging, we were able to confirm the presence of fluid around the femoral nerve. Assuming that this fluid was a local anesthetic, which matched our clinical findings, the likelihood of an iatrogenic nerve injury from needle or surgical trauma, which has rarely been reported, was less likely.11
This case demonstrates that the prolonged duration of liposomal bupivacaine may worsen the adverse sequela of inadvertent nerve blocks. The duration of femoral nerve block was likely prolonged secondary to liposomal bupivacaine use. A review of duration in previous TFNP case reports11,12 suggests a maximum of 36 hours of motor block (20 mL of 0.5% bupivacaine), shorter than the 51 hours to full resolution in our patient.
Serious adverse sequela have been reported from TFNP after field block for inguinal herniorrhaphy including falls resulting in compound leg fractures and head injuries.13,14 In previous case reports, patients are often admitted for observation, or outpatient discharge is delayed until the nerve palsy recedes. Given that this was an outpatient procedure and we suspected prolonged palsy with liposomal bupivacaine, this patient chose to go home rather than be admitted. Regardless of disposition, adequate precautions should be taken to prevent falls until nerve function normalizes. It is important to alert recovery room staff to be vigilant for TFNP when assessing patients whenever wound infiltration or regional techniques are used.
To our knowledge, a TFNP with liposomal bupivacaine has not been reported. As the use of liposomal bupivacaine increases, it is important to assess for both new and known complications of local anesthetic infiltration techniques.
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