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Regional anesthesia techniques are powerful tools for postoperative pain management that have shown to reduce perioperative opioid consumption, Increasing the satisfaction of the patients with their pain control after surgery, and in some cases reducing the length of stay. The lumbar plexus block has been available for several years as an analgesic technique for surgeries involving the hip, the thigh, and the knee, since the first description of this technique several variants and approaches to the lumbar plexus has been described. This activity reviews the anatomy, indication, contraindication, complications of the lumbar plexus block with the neurostimulation approach, and highlights the role of the interprofessional health care team in evaluating and treating postoperative pain. Objectives: Identify the indications for lumbar plexus block. Describe the technique of lumbar plexus block. Outline the potential complications lumbar plexus block. Review interprofessional team strategies for improving care coordination and communication for patients on acute postoperative pain and improve outcomes. Access free multiple choice questions on this topic.

The concept of a regional anesthesia technique that provides neural blockade of the entirety of the lumbar plexus, a lumbar plexus block (LPB), dates back nearly 50 years. The first description of such a block by Winnie et al in 1973 was an “inguinal perivascular technique” alternatively referred to as a “3 in 1 technique”.[1] Winnie proposed that a large volume of local anesthetic injected in the femoral nerve sheath could spread proximally to produce blockade of the obturator, lateral femoral cutaneous, as well as femoral nerve (and presumably the other nerves of the lumbar plexus). Later work would show that, in fact, this rarely succeeded and typically only blocked the femoral and lateral femoral cutaneous nerves. In 1976 Chayen et al. described a “posterior lumbar plexus block” or “psoas compartment block,” which proved to be a more reliable realization of the goal of blocking the whole of the lumbar plexus with a single injection.[2] Touray et al. were among those who demonstrated that whereas both approaches effectively block femoral and lateral femoral cutaneous nerves, indeed, only the posterior lumbar plexus approach is also able to block the obturator nerve.[3] Thus today, the term “lumbar plexus block” is generally not associated with the inguinal femoral nerve block and is considered synonymous with the posterior approach. Since the initial description of the posterior lumbar plexus block, a number of variations of the technique have been described. Most of these differ from the original technique of Chayen et al in only minor detail and are related to the distance of the needle insertion point from the midline or the lumbar level at which the block is performed.[4][5] Perhaps the most significant changes have been in defining the block’s endpoint. The original technique relied on a “loss of resistance,” but this transitioned to the more common use of a nerve stimulator technique (typically looking for motor stimulation of the femoral nerve with quadriceps twitch). More recently, the nerve stimulation method has given way to ultrasound-guided techniques of lumbar plexus block for which several approaches have been described. Thus far, the evidence is lacking to support the superiority of any one of the ultrasound-guided techniques.

Complications related to the lumbar plexus block are infrequent. Although there are authors who report a high incidence of local anesthetic spread to the epidural space, our experience at the University of Pittsburgh is quite the opposite.[5][12] With the epidural spread, one would expect contralateral spread, bilateral weakness, hypotension, and difficulty with micturition. Indeed this is, in our experience, exceedingly rare. More medial needle insertion and a more cephalic approach (L3) may increase the likelihood of this complication.[5] Intrathecal injection and spinal anesthesia as a complication of lumbar plexus block are also rare. Its prevalence is unknown as the vast majority of information comes from case reports and a few observational.[13][14][15] Auroy et al. cited 5 cases of major complications after the LP block from a sample of 394 patients.[16] This report is greatly at odds with the experience of the University of Pittsburgh, where the acute pain service has performed many thousands of LP blocks over the last two decades with few complications altogether, no case of direct intrathecal injection, and only one incident of intrathecal catheter placement. A renal injury such as a subcapsular hematoma is another rare complication of LP block. This complication is associated with the use of a more cephalad injection site, such as at the level of L3. This is one reason that the intercristal line is used as it will lead to needle placement at the L4 or L5 transverse process. Additionally, caution on not advancing the needle more than 2 cm deep to the transverse process will help avoid this complication. Local anesthetic systemic toxicity (LAST) is a potential complication of any nerve block. Most commonly, this is a result of intravascular injection but can also result from the use of an excessive dose of local anesthetic. Treatment should include immediate administration of intravenous intralipid and supportive measures.

A renal injury such as a subcapsular hematoma is another rare complication of LP block. This complication is associated with the use of a more cephalad injection site, such as at the level of L3. This is one reason that the intercristal line is used as it will lead to needle placement at the L4 or L5 transverse process. Additionally, caution on not advancing the needle more than 2 cm deep to the transverse process will help avoid this complication. Local anesthetic systemic toxicity (LAST) is a potential complication of any nerve block. Most commonly, this is a result of intravascular injection but can also result from the use of an excessive dose of local anesthetic. Treatment should include immediate administration of intravenous intralipid and supportive measures. Retroperitoneal or psoas hematoma or other vascular injuries are major complications of LP block but are fortunately quite rare. The risk of bleeding in a non-compressible space such as the psoas compartment is uncertain but is of greater concern when the bleeding site can not be compressed and observed. Therefore patients on anticoagulation therapy or with a diagnosis of coagulopathy may not be proper candidates for this block. Deep plexus blocks such as this should follow the American Society of Regional Anesthesia (ASRA) guidelines of 2018 for neuraxial blocks in patients receiving anticoagulation or anti-aggregation therapy.[17] The risk of a peripheral nerve injury is one of the most common questions patients ask their physicians. Fortunately, it is also a rare complication. The long-term peripheral nerve injury was found to have an incidence of 2 to 4 cases per 10.000 peripheral nerve blocks of all types.[18] Specifically, the rate of peripheral nerve injury reported for the lumbar plexus block may be as low as 0.1%.[19] A muscle twitch response during neurostimulation at a current of less than 0.2 mA is correlated with a high rate of histological nerve injury.[20] When nerve stimulation occurs at such a low current, the needle should be withdrawn a small distance so that 0.5 mA is needed to achieve muscle twitch.

Acute pain management after surgery relies on an interprofessional responsibility, where the surgeon, the nurses, the physical therapist, and the anesthesiologist should work as a team to provide the best strategy for the patient's recovery. The Enhanced Recovery After Surgery defined multiple steps to achieve a faster and better recovery after surgery. The multimodal analgesia strategy for pain management includes the use of Peripheral nerve blocks to reduce opioid consumption, postoperative nausea and vomiting, and the exposure of naive patients to opioids that could end in misuse in up to 10% of the patients that never had opioids before. Additionally, this strategy includes the use of non-opioid medication for pain management like non-steroidal anti-inflammatory drugs, ketamine, and lidocaine, as the first line of treatment for postoperative pain management, reserving the opioids for moderate to severe pain. The education of the surgical team on the importance of an adequate evaluation of pain, treatment, dosing, and strategies for pain control is fundamental for the recovery of the patient.