Episode #64 Be Prepared for Peripartum Peripheral Nerve Injuries

Hello and welcome back to the Anesthesia Patient Safety Podcast.  My name is Alli Bechtel and I am your host. Thank you for joining us for another show. We have reviewed many outstanding articles from the June 2021 APSF Newsletter. Have you read everything in the newsletter yet? We haven’t covered everything on the podcast yet which is why we are diving back in today to talk about an important obstetric anesthesia patient safety concern. I hope you will join me up on the labor and delivery floor.

Before we dive into today’s episode, we’d like to recognize Blink Device Company, a major corporate supporter of APSF. Blink Device Company has generously provided unrestricted support to further our vision that “no one shall be harmed by anesthesia care”. Thank you, Blink Device Company – we wouldn’t be able to do all that we do without you!”

Whew, we made it to the labor and delivery floor and we are ready to talk about our featured article today. It is “Postpartum Peripheral Nerve Injuries – What is Anesthesia’s Role?” by McCrory, Banayan, and Toledo. To follow along with us, head over to APSF.org and click on the Newsletter heading. First one down is the current issue. Then scroll down until you see our featured article. I will include a link in the show notes as well. Before we get into the article, we are going to hear from one of the authors for this article, Emery McCrory and I will let her introduce herself now.

[McCrory] “My name is Emery McCrory and I am an assistant professor of anesthesiology at Northwestern University in Chicago, IL.”

To kick off the show, I asked McCrory why she wrote this article. Let’s take a listen to what she had to say.

[McCrory] “Peripartum peripheral nerve injuries had been studied previously at my institution, but after I had personally experienced a femoral nerve palsy after labor with my first child, I became even more invested in the topic. I recognized how scary it could to have a nerve injury without an existing knowledge base of why they occur and how long they could last.”

Thank you to McCrory for pointing out why this is such an important topic. Don’t worry, we will be hearing more from her at the end of the show. Now, let’s get into the article. This is something that you will want to keep on your radar because postpartum peripheral nerve injuries occur with an incidence of 0.3-2% of all deliveries. It is not a common event, but it can cause significant problems for patients and it is difficult to identify patients at risk for this complication. Why do these occur? The most common culprit is intrinsic obstetric palsy from nerve compression or stretch during delivery. It is important to keep neuraxial anesthesia on your differential as well even though this is less likely. The authors start with a call to action for anesthesia professionals to develop systems that identify women with postpartum lower extremity nerve injuries and make sure that there are resources available to help with diagnosis and recovery.

Let’s get into some of the data regarding postpartum peripheral nerve injuries. We will start with a review of a study of 6,000 patients by Wong and colleagues. Check out Table 1 in the article for a review of the most common postpartum peripheral nerve injuries and the possible mechanism of injury. The two nerves at the top of the list include the lateral femoral cutaneous nerve and the femoral nerve. The nerves at the lower end of the list include common peroneal, lumbosacral plexus, sciatic, obturator, and radicular nerves.

At the top of the list is Lateral femoral cutaneous nerve which occurs in about 4 out of 1,000 parturients. When this nerve is injured, there may be a sensory deficit including decreased sensation on the anterolateral thigh. This is also known as meralgia paresthetica and patients may report tingling, numbness, and burning pain. The good news is that this is often self-limited with a short recovery period. For symptomatic patients, treatment may include nonsteroidal anti-inflammatory medications or lidocaine patches. This injury may occur due to nerve compression during prolonged hip flexion under the inguinal ligament. Obesity is a risk factor from increased compression under the inguinal ligament.

Next up is the femoral nerve injury which may lead to sensory and motor deficits. The sensory deficits include decreased sensation on the anterior thigh and medial calf. The motor deficits include weak knee extension and weak thigh flexion if the iliacus nerve is also involved. A femoral nerve injury may be due to compression under the inguinal ligament following prolonged hip flexion, abduction, and external rotation. Retraction during cesarean delivery and decreased perineural blood flow to the iliacus nerve may contribute to this injury as well.

Moving down the table, the lumbosacral plexus and sciatic nerve may have a compression injury from fetal position, nerve compression on the pelvic rim, and following a forceps assisted vaginal delivery. Patients with this nerve injury may have sensory deficits in the posterior thigh as well as weak quadriceps, weak hip adduction, and foot drop.

We have two more nerves to review. The obturator nerve may be compressed from the position of the fetus, improper positioning, or following a forceps assisted vaginal delivery. The deficits of an obturator nerve injury include decreased sensation on the medial thigh as well as motor deficits including weak hip adduction leading to a wide gait. We made it to the last nerve injury on our list, the common peroneal nerve which may present with decreased sensation on the lateral calf and foot drop. This nerve may be injured due to improper lower extremity position with compression at the fibular head. One example of this is against stirrups in patients under general anesthesia. The common peroneal nerve may also be injured from compression while pushing.

Which parturients are at risk for this complication? Nulliparous parturients and those with prolonged second stage of labor as well as certain methods of delivery such as forceps or vacuum assisted vaginal deliveries  are known risk factors. Another risk factor includes patients with neuraxial catheters since once the catheter is placed, patients are less mobile and more likely to stay in the same position for a longer duration of time which increases the risk for a compression injury. Another consideration is certain anatomical variations in the epidural space leading to high concentration of local anesthesia remaining around individual nerve roots and subsequent neurotoxicity at a high enough dose of local anesthetic. The clinical evidence for this variation is a patchy block. Keep in mind that a low concentration of local anesthesia given through the epidural catheter may help to prevent this complication while still providing adequate pain relief. The authors remind us that patients with a very dense analgesic block may not be able to feel neuropathic pain from nerve compression due to positioning and thus may be at higher risk for nerve compression injuries.

Let’s continue our literature review with the 2017 article by Haller and colleagues that looked at 20,000 parturients who underwent neuraxial anesthesia during labor. The results revealed an incidence of nerve injury of 0.96%. The risk factors for nerve injury included forceps-assisted vaginal deliveries, newborn birth weight more than 3.5 kg, gestational age greater than 41 weeks, and late initiation of neuraxial procedure. A couple factors were identified that did NOT contribute to nerve injuries including time of day for neuraxial placement or provider level of training. In this study, there were 19 injuries. 4 of these occurred due to direct trauma from the Tuohy needle or catheter to the nerve root. Diagnosis was made with electromyography, MRI, or CT scan within 48 hours of delivery. In the 4 cases of trauma to the nerve root, 3 out of the 4 patients experienced a paresthesia during placement at the same level. In addition, 3 of these patients underwent the neuraxial procedure with a cervical dilation of more than 5 cm. Finally, the common finding in all 4 patients was documented difficult neuraxial procedure requiring multiple attempts or severe pain during the procedure. This is an important finding and anesthesia professionals need to discuss the risk for nerve injury when obtaining consent for a neuraxial procedure and following a difficult or traumatic procedure, it may be necessary to counsel patients about the risk for nerve injury.

Have you ever had a patient experience a paresthesia while performing a neuraxial procedure? How do you troubleshoot at this point? The authors provide guidance about what is done at their institution.

Situation #1: If a patient reports a transient paresthesia during spinal or epidural needle placement that resolves without intervention, the you may proceed with the injection.

Situation #2: For a patient with a persistent paresthesia during initial needle placement, this is the time to move the needle away from the paresthesia.

Situation #3 involves performing a spinal anesthetic: If a patient reports a paresthesia during spinal injection of local anesthetic, this is the time to stop the injection and re-identify the intrathecal space prior to intrathecal local anesthesia administration.

Situation #4: If a patient reports a persistent paresthesia during placement of the epidural catheter, this is the time to remove the catheter. The next step is to administer saline through the Touhy into the epidural space to dilate the epidural space prior to re-threading the catheter. Another option is to reposition the Touhy needle away from the direction of the paresthesia and enter the epidural space at a different location.

What about postpartum peripheral nerve injuries that are unlikely to be due to nerve compression or stretch? Another etiology is decreased perfusion to the nerve. In the 2003 study by Wong and colleagues, the researchers identified 4 patients with lateral femoral cutaneous nerve injury who underwent scheduled cesarean section and 22 patients with femoral nerve injuries associated with iliopsoas muscle weakness (which is more cranial than the inguinal ligament). The authors discuss that hypoperfusion to the nerve may have led to injury in these cases, but more studies are needed to determine if there is an appropriate blood pressure management strategy that can help to prevent or decrease the risk for these nerve injuries.  And speaking of new studies, McCrory and her colleagues are completing an Agency for Healthcare Research and Quality-funded study now looking at risk factors related to the patient, obstetric, neonatal, and anesthetic care for new onset postpartum lower extremity nerve injuries. This is exciting work that may be able to determine if there are any modifiable risk factors.

At this point, we have talked about the nerve injuries and what we know about risk factors, but what is our role as anesthesia professionals in this event? Good news, anesthesia professionals can collaborate with their obstetric colleagues to identify patients who develop postpartum nerve injuries and make sure that they have resources for education about and management of these injuries. Identification of patients may be done by asking about any symptoms consistent with a lower extremity nerve injury prior to discharge. Remember, if we ask these questions immediately after delivery, patients may not have symptoms due to residual neuraxial block. Thus, a member of the OB, anesthesia, or nursing team may evaluate the patient on postpartum day #1 and ask the following question:

“Are you having any difficulty walking or do you have any new numbness or weakness in your legs?”

For patients who answer, “yes” a complete evaluation is necessary including additional history and physical exam. Some patients may benefit from a neurology consult and electromyography to determine the location of the injured nerves and muscles.

We need to keep in mind that patients with a lower extremity nerve injury have an increased risk for falling. It is imperative that patients with motor weakness including femoral nerve and lumbosacral plexus injuries are examined prior to discharge so that they can receive information and follow-up to prevent fall injuries and stay safe at home. A physical therapy evaluation prior to discharge may help to determine what assistive devices including knee brace, orthotic shoe, or walker, that patient will need at home. Another management option may include Gabapentin for neuropathic pain. This medication is safe for breastfeeding mothers, but needs to be used with caution due to the risk for increased fatigue. Emotional support and education are also vital components that need to be addressed prior to discharge in order to prevent an increased risk for postpartum depression or anxiety in patients with postpartum peripheral nerve injuries.

The recovery time frame for these injuries is within weeks. Two studies evaluated recovery with reported median symptom duration of 2 months and 18 days, respectively. There may be a small subset of patients who continue to have symptoms for an extended time period, even up to 1 year following delivery.  Patient follow-up can safely be done with the obstetric team, but patients with persistent or worsening symptoms may need to be seen by a neurologist or physical medicine and rehabilitation physician.

Postpartum peripheral nerve injuries remain a threat to patient, I mean, parturient safety. Anesthesia related nerve injuries may occur due to nerve hypoperfusion, traumatic neuraxial placement, and a dense motor block leading to decreased motor function and patient movement during labor. We need more information about the risk factors in order to identify high risk patients and prevent this from happening in the future. The authors leave us with a call to action that anesthesia professionals need to provide education for perinatal clinicians so that all patients are screened for new-onset postpartum nerve injuries prior to discharge. When this screening is positive, then it is important to identify the injured nerve and describe the injury including motor, sensory, or mixed and symptoms in the medical record. It is important to provide patients with information about the injury as well as what to expect from the recovery period.  The last step is a physical therapy evaluation and it is crucial: Make sure that the patient can ambulate safely with their infant and is not a fall risk, especially not when they are carrying their infant at home.

Before we wrap up for today, I asked McCrory the following question, “What do you hope to see going forward?” We are going to listen to McCrory’s thoughtful response now.

[McCrory] “In addition to studying how we can reduce the risk of these events from occurring, I also would like to see more standardization of care for patients who experience peripartum peripheral nerve injuries. I am lucky to work at an institution that has the resources to help ensure that these patients are safe to be discharged from the hospital, but this is not the case everywhere which puts both the patient and the newborn at risk in the instance of a fall.”

Thank you so much to McCrory for contributing to the show today. We will be looking forward to learning more about reducing the risk for these nerve injuries and standardization of care in the future.

If you have any questions or comments from today’s show, please email us at [email protected].

Visit APSF.org for detailed information and check out the show notes for links to all the topics we discussed today.   Please keep in mind that the information in this show is provided for informational purposes only and does not constitute medical or legal advice.

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Until next time, stay vigilant so that no one shall be harmed by anesthesia care.

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