A 33 years old male, known Myasthenia gravis on Neostigmine 15mg, s/p Thymectomy for Thymoma on April 2024, post radiotherapy, came with complaint of headache and confused state for 3 days. GCS- 14/15. MRI brain has shown bilateral maxillary, posterior Ethmoidal, sphenoid sinusitis-? Fungal origin. Lumbar puncture- Negative. Hence he was posted for Diagnostic Functional Endoscopic Sinus Surgery.

PRE-OPERATIVE PLANNING:

• The results of routine investigations were within normal limits. Normal sinus rhythm on the ECG. 2D ECHO: Lv function Normal.
• Following consultation with the surgeon, the patient and his attendants received a thorough explanation of the anesthesia strategy and associated risks. Written and informed consent was acquired.
• NPO regulations were adhered to.
• Premedication: T. neostigmine 15 mg PO with sips of water, Inj. pantoprazole 40 mg IV, and Inj. palonosetron 0.075 mg IV, IV IG.

INTRA-OPERATIVE MANAGEMENT :

• ASA-standard monitors were connected to the patient when they were in a supine position.
• Preoxygenation for three minutes using 100% O2.
• Intravenous injection of PROPOFOL (1-2 mg/kg; the lower range is suggested) is the induction medication.
• One tenth of the actual IV dose of a non-depolarizing muscle relaxant, such as Inj. CiSATRACURIUM, is administered.
• A 7.5 mm oral RAE tube is used to secure the airway, and ETCO2 confirms this.
• maintained with a TIVA infusion of Injection REMIFENTANIL and Injection PROPOFOL.
• The intraoperative phase went smoothly.
• reached the extubation criteria and was extubated on the table. hemodynamic stability of the patient.

DISCUSSION :                 

Anaesthetic implications of Myasthenia gravis patient:

The type of surgery and the severity of the disease must be taken into consideration when managing the anesthesia for a myasthenic patient. Whenever feasible, the administration of local or regional anesthesia appears to be justified. To lessen the potential effects of anesthetics on neuromuscular transmission, patients may have their local anesthetic dosage lowered whenever local or regional anesthesia is utilized. When patients undergoing anticholinesterase therapy (which inhibits plasma cholinesterase) are given ester local anesthetics, this may be very crucial.

• If the patient is well-prepared and neuromuscular transmission is sufficiently monitored both during and after surgery, general anesthesia can be administered safely.

PRE-OPERATIVE PREPARATION:

• Careful preoperative evaluation of the myasthenic patient is necessary. The response to thymectomy may be influenced by factors such as age, sex, the initiation and progression of the disease, and the presence of a thymoma. It is also necessary to assess the degree of myasthenia and whether the bulbar or respiratory muscles are affected. To allow for a thorough evaluation of respiratory muscle and bulbar function as well as a review of anticholinesterase and corticosteroid therapy, patients should be admitted 24 to 48 hours prior to surgery. Serial forced vital capacity (FVC) testing is the most effective way to track respiratory reserve.
• Preoperative variables such as FVC < 2.91, MG history > 6 years, and major surgery are linked to the necessity for prolonged postoperative IPPV.
• Lung disease that coexists.

Third and fourth grade MG.

It is necessary to provoke further autoimmune diseases and start the proper preoperative examinations.

• Improving myasthenic patients’ conditions can significantly reduce their risk of surgery and enhance their results. Numerous preoperative therapy regimens have been suggested.
• Whether anticholinesterase medication should be taken or stopped prior to and following surgery is up for debate. Since anticholinesterases intensify vagal reflexes, proper atropinization needs to be guaranteed. Additionally, anticholinesterase enzymes can suppress plasma cholinesterase activity, which will reduce succinylcholine hydrolysis and the metabolism of ester local anesthetics.
• The length of succinylcholine block in myasthenic patients is inversely correlated with plasma cholinesterase activity, much like in non-myasthenic patients.
• A myasthenic patient may require more nondepolarizing muscle relaxants if anticholinesterase inhibits acetylcholinesterase, as opposed to succinylcholine, albeit this has not been reported.
• Recently, the myasthenic patient’s medical condition has been improved before major surgery by using plasmapheresis alone, without immunosuppression. While corticosteroid drugs are kept on taper and stopped after surgery, anticholinesterase agents are stopped.
• Premedication: Because myasthenic patients may have little respiratory reserve, depressive medications should be used cautiously before surgery and should not be used in individuals who have bulbar symptoms. However, anticholinergic medications may be helpful. People on long-term corticosteroid medication should be given hydrocortisone “cover.”

ANAESTHETIC TECHNIQUES:

• Although none is better, two methods have been suggested for general myasthenic patients. Some anesthetists avoid using muscle relaxants and rely on deep inhalational anesthesia for tracheal intubation and anesthesia maintenance due to the patient’s unpredictable reaction to succinylcholine and their strong sensitivity to non-depolarizing muscle relaxants. After surgery, these substances are quickly removed, allowing neuromuscular transmission to restore.
• Because of their limited blood solubility, desflurane and sevoflurane may theoretically have certain advantages. Because sevoflurane causes less excitatory airway responses during inhalational induction, it is likely preferable to desflurane.
• Others, on the other hand, employ a well-rounded approach that involves the use of muscle relaxants; deep inhalational anesthesia is not necessary, and small doses (10–25% of the ED95) of intermediate-acting relaxants are titrated while being monitored with a peripheral nerve stimulator for both intubation and, if necessary, surgical relaxation. It is debatable whether residual neuromuscular blockade should be reversed after surgery. Anticholinesterase and antimuscarinic medications, according to some, will make it more difficult to distinguish between cholinergic crisis and weakness brought on by insufficient neuromuscular transmission in the recovery room. When the patient has shown sufficient extubation characteristics (head lift, tongue protrusion), some people prefer spontaneous recovery and extubation.
• There have been reports of using total intravenous anesthesia (TIVA) to treat myasthenics. While younger patients typically tolerate this method, elderly patients’ hemodynamic instability makes it more challenging. Hemodynamic instability may be somewhat reduced by using Remifentanil as part of TIVA.
• Many practitioners prefer to use local or regional anesthetic treatments whenever available. In abdominal surgery, regional procedures may lessen or even completely eliminate the requirement for muscle relaxants. The benefit of epidural methods is that they can reduce postoperative pain with little to no narcotic use.

POSTOPERATIVE MANAGEMENT:

• Following surgery, ventilation function needs to be closely evaluated. Adequate breathing is correlated with only a few neuromuscular function tests.
• Patients who have myasthenia may be more susceptible to postoperative respiratory failure; after a transsternal thymectomy, up to 50% of patients need ongoing postoperative support.

FOUR RISK FACTORS HAVE BEEN IDENTIFIED:

• Longer than six-year duration of myasthenia gravis (12 points). The most valuable factor in predicting the requirement for ventilatory assistance was the duration of MG.
• Other than respiratory impairment directly caused by MG, a history of chronic respiratory disease (10 points).
• A daily pyridostigmine dosage of more than 750 mg, 48 hours before to surgery (8 points).
• A critical capacity of less than 2.9 L prior to surgery (4 points).

A total score of ≥ 10 points indicated which patients were most likely to require postoperative pulmonary ventilation for more than three hours. These risk factors were weighted based on their importance as predictors.

REFERENCES:

• Miller’s Anesthesia,9th edition.
• Stoelting’s Anesthesia and Co-Existing Disease, 8th edition.
• Morgan & Mikhail’s clinical Anaesthesiology, 7th edition.
• Hossain, Md. M., and Peter D. Smith. “Anesthesia Considerations in Patients with Myasthenia Gravis.” Journal of Clinical Anesthesia 35, no. 5 (2020): 100-107.

Dr Velmurugan Deisingh,
Head of the Department,
Department of Anaesthesiology,
Kauvery Hospital, Chennai.

Dr Moushiga Subhashini,
II year DNB Resident,
Department of Anaesthesiology,
Kauvery Hospital, Chennai.