Anaesthesia in myasthenia

1. Anaesthesia in myasthenia Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statistics, PhD (physio) Mahatma Gandhi Medical college and research institute , puducherry India

2. What is myasthenia gravis • MG is an autoimmune disorder – • circulating antibodies to nicotinic acetylcholine receptors at the neuromuscular junction • antibodies reduce the numbers of receptors • Symptoms if only 30% receptors are present reUp to 25% of patients have a concurrent thymoma, • About 10% have evidence for other autoimmune diseases

3. ors reduced to 30% of normal

4. Clinical features • muscle weakness -an overall fatigability increases with exertion over the course of the day. 14:100,000 age 10 and 40. (bimodal ) Females are more frequently affected • diplopia and ptosis resulting from weakness of the ocular muscles. • slowly spread to bulbar muscles, which may lead to aspiration and respiratory failure, and later affect the proximal extremities

5. Osserman and Genkins • class I (ocular muscles only); • class II (eye symptoms plus mild generalize weakness); • class III (eye plus moderate weakness); • class IV (eye plus severe weakness); • class V (intubation, ventilation)

6. How to diagnose ? • blood tests for antibodies; • electromyographic recordings; • electrophysiologic evaluation is often performed and shows a classic decrement in the compound muscle action potential after repetitive nerve stimulation.

7. cholinesterase inhibitor test (edrophonium test); • Tensilon test (administration of an anticholinesterase, e.g., edrophonium). Improvement is usually seen within 5 minutes after administration of the drug and lasts for about 10 minutes • Imaging (to identify thymoma).

8. Drugs aggravate Neuromuscular weakness • Penicillamine • Nondepolarizing muscle relaxants   • Aminoglycosides • Procainamide

9. Some other DD s of myasthenia • Graves' disease • Eaton lambert syndrome • Cranial nerve palsies • Congenital myasthenic syndromes

10. Other autoimmune diseases coexisting • hyperthyroidism is present in approximately 10% of patients with myasthenia gravis. • Rheumatoid arthritis, SLE, and pernicious anemia occur more commonly in MG

11. Treatment • Two problems • I. muscle weakness • Cholinesterase inhibitors (neostigmine, • Pyridostigmine • (maximal dose )120 mg every 3 hours)

12. Problem 2. immunosupression • corticosteroids and • immunosuppressive drugs (cyclosporine, azathioprine) • Plasmapheresis-(four to eight treatments over 2 weeks • thymectomy is performed if general symptoms are present

13. Anaesthetic challengesPreop evaluation • preoperative interview that they may be intubated and ventilated when they awaken • All routine investigations • ECG -- Cardiac arrhythmias and myocarditis

14. Preop preparation • pyridostigmine ↓ • Bad response ↓ good response • Young old ↓ ↓ • Steroids steroids + azathioprine • ↓ ↓ • Imp. Not imp imp.→taper steroids →thy • ↓ ↓ • Thy add plasma

15. Preop preparation • Only plasmapheresis

16. Preop • Lung function testing • Respiratory and bulbar functions should be carefully evaluated during the preoperative evaluation • Preop neurologist evaluation • Preoperative plasmapheresis

17. Post op ventilation ?? • Four Factors • disease duration of longer than 6 years, • chronic obstructive pulmonary disease(COPD) unrelated to myasthenia gravis, • a daily dose of pyridostigmine higher than 750 mg, • and a vital capacity less than 2.9 L.

18. Premed • Anticholinesterase to continue ?? • Small dose benzodiazepine • Anticholinergics

19. Anaesthetics-Nondepolarizing Neuromuscular Blockers • Long acting NDNMB (pancuronium, pipecuronium, doxacuronium) :avoided • Intermediate and short acting: used with careful monitoring..

20. Depolarizers nondepolarizers

21. Succinylcholine • resistance to depolarizing agents.( ED95 : 2.6 times of control) • because of the decreased number of functional acetylcholine receptors • more likely to develop phase II block • decrease in cholinesterase activity achieved by anticholinesterase treatment

22. So regarding relaxants • NDP s more sensitive • Depolarizers more resistant

23. Inhaled Anaesthetics • Isoflurane , enflurane: decrease TOF responses • Sevoflurane at 2.5% depresses EMG responses • effects of desflurane in MG ??

24. Intravenous Anaesthetic Agents • Propofol√ • -- no effect on NMJ • Etomidate, althesin and ketamine : Reports of uneventful anesthesia. • Opioids • do not appear to depress NM transmission in MG muscle. • Central respiratory depression may be a problem

25. Anaesthesia -1 • IV induction • + inh. Drugs + • intubation • Maintain on N2O ,O2, Inh. Agent • No NonDepolarizers • Extubate without reversal

26. Anaesthesia - 2 • Propofol • Scoline • N2O ,O2, Inh. Agent • Nondepolarizers (10% dose with NMJ monitor) • unsuccessful extubation, longer postoperative mechanical ventilation and hospital stay • Suggamadex or post op ventilation

27. Regional Anesthesia • Ester anesthetics, metabolized by cholinesterase, may present particular problems in patients taking anticholinesterases. • Use reduced doses of amide (lidocaine, bupivacaine) to avoid high blood levels. • Remember drugs and coexisting diseases

28. Anaesthesia 3, 4 • TIVA for the management of myasthenics has been reported. • Local anaesthesia is successful

29. Postoperative considerations • Weakness • Pain (local ,epidural opioids ) • Myasthenic crisis • Cholinergic crisis • Resume the anticholinergic therapy as soon as possible after surgery. The postop requirements may be different from the routine preoperative dose and • careful titration because the IV dose is only about 1/30 to 1/120

30. Post op problems • Nerve stimulator - bulbar Vs limb muscles • Inspiratory force of > - 25 cm is OK • Trans sternalthymectomy – 50 % req. ventilation • Trans cervical thymectomy OR • video-assisted thorascopic (VATS)– • less post op ventilation ,remission more ?? • Early thymectomy better !!

31. Your icu ready

32. Myasthenic crisis • Myasthenic crisis is a life-threatening condition, which is defined as weakness from acquired myasthenia gravis (MG) that is severe enough to necessitate intubation

33. precipitants • infection. • Surgery • Pregnancy, • certain antibiotics (aminoglycosides, erythromycin and azithromycin), cardiac drugs (beta-blockers, procainamide, and quinidine), and magnesium. • TREAT VIGOROUS WITH POSSIBLE OPTIONS

34. Cholinergic crisis • excess of cholinesterase inhibitors (ie, neostigmine, pyridostigmine, physostigmine) • resembles organophosphate poisoning. • excessive ACh stimulation of striated muscle at nicotinic junctions produces flaccid muscle paralysis that is clinically indistinguishable from weakness due to MG.

35. Cholinergic crisis • Miosis and the SLUDGE syndrome (ie, salivation, lacrimation, urinary incontinence, diarrhea, GI upset and hypermotility, emesis) also may mark cholinergic crisis. • Despite muscle weakness, deep tendon reflexes are preserved.

36. Cholinergic crisis • When muscarinic effects are obvious , diagnosis is easily made. Antimuscarinics and respiratory support are given • EDROPHONIUM TEST WILL DIFFERENTIATE BOTH CRISES

37. Myasthenia and pregnancy • Exacerbations of myasthenia must be anticipated during pregnancy • Epidural analgesia and anaesthesia can be used for labour and delivery • Muscle relaxation induced by regional anaesthesia may compound the weakness caused by myasthenia.

38. Myasthenic syndrome • Acq. Disorder • Small cell ca of lungs • IgG antibodies to pre synaptic voltage dep. Calcium channels • Abn. Vesicular release • Exercise improves • Diaminopyridine improves • Sensitive to both DPs and NDPs • anticholinesterase agent - not dependable

39. SUMMARY • Preop bulbar? Anticholinestrase , plasmapheresis , premed atropine • GA with propofol, inh. agents ,no NDPs • Post op ventilation • Or GA, relaxants, suggamadex, ventilation • Other surgeries – possible RA, LA • Post op epidural opioids, muscle weakness

40. Thank you all