National Board Ex- 6 Book .pmd - National Board Of Examination

equired, and improvementmay last only 4 days or as longas 12 weeks. Plasmapheresisalso decreases pseudocholinestraselevels, which resultsin prolonged durationof action of succinylcholine.l Thymectomy has providedlong term improvement bydecreasing production, or thestimulus for production ofantibodies directed at nicotineacetylcholine receptors.Thymus may be responsiblefor the pathogenesis of MGbecause the thymus containsmyoid cells with nicotinic receptorsand a number ofmyasthenics have thymic abnormalities.It may also besource of autoreactive helperT-cells. It is the preferredtreatment under 55 years ofage, but can be done if patientis medically fit.Approaches of thymectomyl Transcervical - Less interferencewith respiratory mechanics,complete removal isdoubtful.l Transsternal -Completeremoval possible.l Thoracoscopic removal-Needs one lung ventilation,supposed to cause less pain.l When thymoma is present,removal of thymus gland viasternotomy may be required.Anaesthetic managementThe anaesthetic management ofthe myasthenic patient must beindividualized to the severity ofthe disease and to the type ofsurgery. The use of regional orlocal anaesthesia is warrantedwhenever possible, Generalanaesthesia can be performedsafely, provided the patientis optimally prepared andneuromuscular transmission isadequately monitored during andafter surgery 6 .Preoperative preparation-Adequate preoperative evaluationof the myasthenic patient mustbe carried out carefully. Specifichistory and examination shouldinclude:l Age, sex, onset and durationof the disease – These as wellas the presence of thymomamay determine the responseto thymectomy.l The severity of myastheniaand the involvement ofbulbar or respiratory musclesmust be evaluated.l Preoperative respiratoryfunction tests must beperformed since chronicrespiratory disease and/or apreoperative vital capacity