Background: Lambert Eaton Myasthenic Syndrome (LEMS) is an autoimmune disorder that forms antibodies against presynaptic voltage-gated calcium channels, resulting in muscle weakness, especially the limbs. The prevalence is... [ view full abstract ]
Background: Lambert Eaton Myasthenic Syndrome (LEMS) is an autoimmune disorder that forms antibodies against presynaptic voltage-gated calcium channels, resulting in muscle weakness, especially the limbs. The prevalence is around 3.4 per million. Sixty percent of the patients have an underlying malignancy, which is most commonly small cell lung cancer. In contrast to myasthenia gravis, muscle weakness is most often seen in proximal arms and legs and may be temporarily relieved after exertion. This can present as an anesthetic challenge as patients have increased sensitivity to both depolarizing and non-depolarizing muscle relaxants and may have associated perioperative complications.
Case description: Our patient is a sixty-nine year old female with past medical history significant for metastatic small cell lung cancer complicated by LEMS, hypertension, type 2 diabetes mellitus and CKD on dialysis, presenting for mediastinoscopy and bronchoscopy. She had generalized weakness and limited exercise tolerance, likely due to a combination of LEMS and her chronic disease process, but she was able to walk short distances with a walker. Preoperatively, she continued her home pyridostigmine dose and was pre-medicated with ranitidine. She was induced with propofol and ventilated by mask while we checked for baseline train-of-four response. She was then paralyzed with less than 0.6mg per kg dose of rocuronium after taking into account of increased sensitivity to NMBAs in LEMS patients. Anesthesia was maintained with desflurane while analgesia was provided with fentanyl. At the end of the case, the patient had 2/4 twitches on ToF. We reversed muscle relaxation with 4mg per kg sugammadex. We confirmed 4/4 strong ToF twitches and sustained tetanus prior to extubation. She remained stable throughout the whole case and was discharged home on POD#1 without residual weakness in PACU or during the remainder of her hospital stay.
Discussion: The preferred method in managing patients with LEMS includes the avoidance of NMBAs in order to prevent the need for post-operative mechanical ventilation due to residual muscle weakness. However, since FDA approval of Sugammadex use in the US, we have been presented with another option. Sugammadex is a modified gamma-cyclodextrin that sequesters rocuronium and vecuronium. Upon reviewing the literature, we found a fair amount of literature on use of sugammadex in patients with MG but very limited case reports and studies on the use of sugammadex for NMBA reversal in patients with LEMS. Historically, compared to MG patients, LEMS patients have a poorer response to neostigmine, which may result in increased risk of postoperative residual muscle weakness. This makes sugammadex an ideal NMBA reversal agent in patients with LEMS.
