MYASTHENIA GRAVIS (MG) is a rare autoimmune disease that is characterized by fluctuating muscle weakness due to autoantibodies against the acetylcholine receptor or other related functional molecules at the neuromuscular junction.
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Thymoma frequently is associated with several types of diseases, of which MG is the most common. It is diagnosed in 10% to 15% of these patients.2
Resection of the thymoma remains the main therapeutic strategy. In recent years, focus has shifted from thoracotomy and transsternal thymectomy toward minimally invasive approaches, including video-assisted thoracoscopic surgery (VATS) and robotic-assisted thoracoscopic surgery (RATS).1
RATS in particular offers some unique advantages, including capacity for 10 × magnification, 3-dimensional vision, and highly precise dissections of the thymus. These minimally invasive surgical techniques present a challenge for the anesthesiologist due to the impact of MG on perioperative anesthetic management.One of the main challenges in patients with MG undergoing thymectomy by RATS is the prediction of the need for postoperative mechanical ventilation
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and the level of postoperative recovery care—that is, in the postanesthesia care unit or intensive care unit (ICU). In this issue of the Journal, Scheriau et al5
reported a retrospective, single-center study of postoperative respiratory complications and the care environment (ICU v recovery room/surgical ward) in patients who underwent thymectomy by RATS for MG. The primary focus of the report was on 72 patients who underwent RATS thymectomy from 2014 to 2019, prior to implementation of a postthymectomy care algorithm. The authors reported, in some detail, the respiratory complications that occurred in this patient group, with myasthenic crisis reported in 5.6% of their patient cohort. Additionally, the authors described their new postthymectomy care algorithm, in which patients are predetermined for ICU versus recovery room/surgical ward based on preoperative criteria (ie, presence of bulbar symptoms, myasthenic crisis within the previous 3 months, functional vital capacity <70% or forced expiratory volume in the first second <70%, body mass index >28 kg/m2, or Osserman score >IIb). The new postthymectomy algorithm also prescribes an observation period of 4 hours for non-ICU patients and criteria for progression to the surgical ward (ie, absence of bulbar symptoms, neck strength, ability to count to 50 without observed dysarthria, and ability to swallow water). The outcomes of 30 patients who underwent RATS thymectomy after implementation of this new algorithm briefly were described.Contribution to Existing Knowledge
Several previous studies have focused on which preoperative and intraoperative factors may predict the need for postthymectomy mechanical ventilation or the risk of myasthenic crisis. Liu et al
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conducted a systematic review and meta-analysis of 25 studies (including 3,728 patients and 692 myasthenic crisis cases) that investigated risk factors associated with postthymectomy myasthenic crisis. These included preoperative factors (eg, history of myasthenic crisis, bulbar symptoms, advanced Osserman stages, pyridostigmine dosage, serum acetylcholine receptor antibody level, preoperative lung function, and disease duration before thymectomy), surgical factors (eg, intraoperative blood loss, World Health Organization thymic classification, and surgical approach), and postoperative factors (eg, postoperative lung function and major postoperative complications).6
Studies specific to RATS thymectomy have reported low incidence of postoperative myasthenic crisis (2.2%-5.4%), without providing specific recommendations for risk stratification in this patient population.7
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The level of care (ICU v non-ICU) has been studied less commonly as an outcome. Scheriau et al
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presented their experience of implementing an algorithm for bypassing ICU care in postthymectomy patients as a somewhat novel practice or departure from typical practice. Although postoperative care for the transsternal approach to thymectomy may include postoperative mechanical ventilation and ICU care,3
minimally invasive approaches, such as VATS and RATS, may require less intensive care.4
A prior study of a perioperative management protocol in VATS-extended thymectomy reported a reduction in postthymectomy ICU admission after implementation of the protocol, from 26% ICU admission preprotocol to 6.8% ICU admission postprotocol, and demonstrated the feasibility of safe postoperative care for thymectomy patients outside of an ICU setting.9
When combined with the low postoperative myasthenic crisis incidence reported for RATS thymectomy,7
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it may be reasonable to extrapolate that non-ICU care also can be safe for RATS thymectomy patients. It has been advocated that postoperative disposition and patient monitoring should be determined based on the patient's clinical presentation to include appropriateness for extubation and surgical and anesthetic course.10
Study Limitations
As with many studies on this topic, the generalizability of the results of this study was limited by the single-center retrospective study design and the limited sample size. In addition, as the findings of this study largely were descriptive, the absence of statistical analysis limited the interpretation of effect size of their intervention.
In this retrospective, cohort study, the authors did not seem to define clearly the comparator cohorts. The comparator cohorts could be interpreted to be patients undergoing RATS thymectomy from 2014 to 2019 who developed postoperative respiratory complications versus those who did not develop postoperative respiratory complications. Another interpretation of the comparator cohorts could be that one cohort was the prealgorithm patient group (2014-2019) and the other cohort was the postalgorithm patient group (2020-2022). Patient populations before and after implementation of the new algorithm have some apparent differences, with at least 30% to 45% of prealgorithm patients meeting one or more criteria for postoperative ICU care ,compared with 20% of postalgorithm patients.
Notably, details of neuromuscular blockade patient monitoring were not included. This represents a significant omission due to the potential impact of residual neuromuscular blockade on respiratory function in this patient population. The increased sensitivity to nondepolarizing neuromuscular blockade agents in patients with MG warrants exercising caution in administering these agents and close monitoring of their effects. Although it is reported that train-of-four (TOF) monitoring was used to guide neuromuscular blockade agent management in the prealgorithm group, TOF parameters (eg, TOF count, TOF ratio) prior to extubation were not reported. Given that neuromuscular blockade reversal was administered in only 47% of the patients who received neuromuscular blockade agents, it would be difficult to exclude the role of residual neuromuscular blockade in postoperative respiratory complications, especially in such a high-risk population. Indeed, a retrospective, observational study of postthymectomy patients demonstrated a reduction in myasthenic crisis in patients who received the neuromuscular blockade reversal agent sugammadex.
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Others have described successful extubation in the operating room in patients with MG undergoing VATS thymectomy. In a small series of 10 patients with MG undergoing VATS thymectomy, rocuronium was administered and titrated to TOF parameters.
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At the conclusion of surgery and prior to extubation, the patients received sugammadex, 2 mg/kg. In this report, all patients were extubated in the operating room after administration of sugammadex, and none of the patients required mechanical ventilation due to respiratory failure or myasthenic crisis. This preliminary report12
appeared to indicate that in patients with MG undergoing minimally invasive thymectomy, reversal with sugammadex may facilitate early extubation, and this should be considered as a factor when immediate extubation is possible.Future Work
In this study, Scheriau et al
5
presented their experience that patients after RATS thymectomy can bypass ICU care safely in their center. A systematic validation of their algorithm would strengthen its utility and value. The generalizability of their algorithm and experience could vary greatly depending on patient population and center-specific resources and care protocols.We appreciate the contributions of Scheriau et al on this important topic and welcome further work in future studies.
Conflict of Interest
None.
References
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- Prediction of postoperative mechanical ventilation after thymectomy in patients with myasthenia gravis: A myth or reality.J Cardiothorac Vasc Anesth. 2018; 32: 331-333
- Perioperative management of patients with myasthenia gravis undergoing robotic-assisted thymectomy-a retrospective analysis and clinical evaluation.J Cardiothorac Vasc Anesth. 2022; 36: 3806-3813
- Assessment of the risks of a myasthenic crisis after thymectomy in patients with myasthenia gravis: A systematic review and meta-analysis of 25 studies.J Cardiothorac Surg. 2020; 15: 270
- 8 years' experience with robotic thymectomy for thymomas.Surg Endosc. 2014; 28: 1202-1208
- Multi-institutional European experience of robotic thymectomy for thymoma.Ann Cardiothorac Surg. 2016; 5: 18-25
- A standardized protocol for the perioperative management of myasthenia gravis patients. Experience with 110 patients.Acta Anaesthesiol Scand. 2012; 56: 66-75
- Myasthenia gravis and thymoma surgery: A clinical update for the cardiothoracic anesthesiologist.J Cardiothorac Vasc Anesth. 2019; 33: 2537-2545
- Effect of sugammadex on postoperative myasthenic crisis in myasthenia gravis patients: Propensity score analysis of a Japanese nationwide database.Anesth Analg. 2020; 130: 367-373
- Rocuronium and sugammadex in patients with myasthenia gravis undergoing thymectomy.Acta Anaesthesiol Scand. 2013; 57: 745-748
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Published online: June 29, 2022
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- Perioperative Management of Patients With Myasthenia Gravis Undergoing Robotic-Assisted Thymectomy—A Retrospective Analysis and Clinical EvaluationJournal of Cardiothoracic and Vascular AnesthesiaVol. 36Issue 10
- PreviewPostoperative myasthenic crisis with respiratory failure is a potentially lethal complication, warranting careful perioperative planning and extended postoperative surveillance of patients. Data on the incidence of postoperative respiratory failure and optimal management of patients after robotic-assisted thymectomy are limited. The objective of this study was to evaluate the incidence of respiratory complications and the need for intensive care unit (ICU) capacities after robotic-assisted thymectomy in patients with myasthenia gravis.
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