Anesthetic Management of a Parturient with Amyotrophic Lateral Sclerosis Undergoing Cesarean Section
Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive neuromuscular disease characterized by the degeneration of both upper and lower motor neurons. This condition leads to muscle weakness, atrophy, and eventual death, typically within 3 to 5 years, most commonly due to respiratory failure. Managing anesthesia in patients with ALS, particularly parturients, presents unique challenges for anesthesiologists. This article delves into the anesthetic management of a 31-year-old pregnant woman with ALS undergoing a cesarean section, highlighting the strategies employed to ensure a safe and effective procedure.
Case Presentation
The patient was a 31-year-old woman at 37 weeks of gestation, weighing 65 kg and measuring 165 cm in height. She had been diagnosed with ALS 13 months prior to the procedure. Her symptoms included dysarthria, difficulty lifting her head from the bed, and motor weakness in her upper extremities, with motor power graded at 3 and 4 for the right and left proximal upper extremities, respectively. She also exhibited mildly impaired swallowing and respiratory dysfunction, requiring non-invasive ventilator support at midnight using bi-level positive airway pressure (BiPAP) synchrony.
Pre-operative evaluation revealed an Amyotrophic Lateral Sclerosis Functional Rating Scale Revised (ALSFRS-R) score of 28, indicating moderate functional impairment. Her family history was notable for hereditary features of motor neuron disease, with her mother’s brother diagnosed with lower motor neuron syndrome and her grandfather’s brother presenting with neck weakness. Both relatives died within 1 to 3 years of symptom onset. The patient had previously delivered a boy at the age of 27 but experienced postpartum urinary retention lasting 40 days following vaginal delivery, attributed to meperidine use. Pulmonary function tests showed a restrictive pattern with a forced vital capacity of 52% of normal. Arterial blood gas analysis revealed a PaCO2 of 34.1 mmHg and oxygen saturation of 98.7% with non-invasive ventilator support.
Anesthetic Strategy
Given the patient’s condition, a multidisciplinary team decided to implement a combination of bilateral ultrasound-guided transversus abdominis plane (TAP) block and incision infiltration before delivery, followed by total intravenous anesthesia (TIVA) with remifentanil and propofol administered via target-controlled infusion after delivery to achieve adequate analgesia.
Upon entering the operating room, standard monitoring was established, including a 5-lead electrocardiogram with ST-segment analysis, non-invasive blood pressure monitoring, and pulse oximetry. The patient was positioned supine and continued to receive oxygen through her BiPAP ventilator. Under ultrasound guidance, a 17 G Touhy needle was positioned via an in-plane approach at the mid-axillary line between the subcostal margin and iliac crest. A total of 20 ml of 0.5% ropivacaine was injected on each side, ensuring adequate spread between the internal oblique and transversus abdominis muscles. Partial onset of sensory blockade was observed within 10 minutes, and 0.5% lidocaine was injected around the incision site at the time of surgical incision.
A live girl weighing 2650 g was delivered, with Apgar scores of 10-10-10 at 1, 5, and 10 minutes. Anesthesia was maintained with propofol at a plasma target concentration of 2 mg/mL (Marsh model) and remifentanil at 3 ng/mL (Minto model), effectively managing intra-operative discomfort. Throughout the procedure, the minimal oxygen saturation (SpO2) was 98%, and arterial blood gas measurements shortly after delivery showed a PaCO2 of 31 mmHg and PaO2 of 106 mmHg. Post-operative pain was managed without opioids, with pain intensity scores of less than 4 on the numerical rating scale (NRS) at 2 and 24 hours. The patient was discharged on postoperative day 3 without complications.
Discussion
ALS is a degenerative disease affecting the motor ganglia in the anterior horn of the spinal cord and the spinal pyramidal tracts. It is the most common form of motor neuron disease, with an annual incidence of 1.5 to 2.5 cases per 100,000 people. Approximately 10% of ALS cases are familial, with autosomal-dominant inheritance. Recent research has identified mutations in the fused in sarcoma (FUS)/translocated in liposarcoma gene as a cause of familial ALS. In this case, polymerase chain reaction analysis of the patient’s total RNA revealed a minor mutation in the FUS gene (NM_004960).
Cesarean section was deemed the safer delivery option due to the patient’s progressive respiratory muscle weakness, which could compromise her ability to meet the respiratory demands of labor and delivery. The choice of anesthetic method for ALS patients must consider the potential impact on disease progression. The use of local anesthetics near nerves or needle trauma could exacerbate pre-existing symptoms, leading to the decision to avoid neuraxial block in favor of a more conservative and safer approach.
General anesthesia (GA) carries its own risks, particularly in patients with bulbar involvement, who are at increased risk of postoperative aspiration and respiratory insufficiency. Literature suggests that mortality rates may rise in ALS patients with ALSFRS-R scores below 39. Therefore, peripheral nerve blockade was chosen to minimize the potential effects of local anesthetics on the spinal cord, and TIVA without muscle relaxants was employed to ensure a smooth recovery after GA. The use of ropivacaine for peripheral nerve blockade in ALS patients has been recommended in other studies. For instance, Belavy et al. used 0.5% ropivacaine (40 mL) for bilateral TAP blocks after cesarean section, effectively blocking pain at the level of the skin, subcutaneous tissue, and muscle, though not affecting visceral pain. Intravenous anesthetics can address visceral pain, with sub-anesthetic concentrations of propofol, sevoflurane, remifentanil, and ketamine reducing visceral pain-evoked potential amplitudes. In this case, the rapid-acting analgesic remifentanil and the amnestic agent propofol were selected to manage visceral pain effectively.
The avoidance of muscle relaxants was crucial, as depolarizing neuromuscular blockers like succinylcholine can cause a lethal elevation of serum potassium in neuromuscular disorders such as ALS. Non-depolarizing neuromuscular blockers should be used sparingly and at the lowest possible doses, with neuromuscular function monitoring to ensure safety.
Conclusion
This case highlights the importance of a tailored anesthetic approach for parturients with ALS undergoing cesarean section. The use of peripheral nerve blockade minimizes the potential effects of local anesthetics on the spinal cord, while TIVA with rapidly reversible short-acting analgesic and amnestic agents, without neuromuscular relaxants, ensures a safe and effective procedure. The overall strategy outlined in this case underscores the need for careful consideration of the patient’s condition and the potential risks associated with different anesthetic techniques in ALS patients.
doi.org/10.1097/CM9.0000000000000809
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