Neuromuscular Flashcards
Myasthenia Gravis is autoimmune destruction of what subunit of the muscle type nicotinic acetylcholine receptor?
Alpha subunit
What muscles are affected by myasthenia gravis?
Ocular and bulbar (laryngeal and pharyngeal) .. skeletal muscles innervated by cranial nerves most vulnerable
What is the Tensilon test?
Edrophonium test differentiates cholinergic crisis - need less pyridostigmine – muscle weakness with administration from myasthenic crisis – muscle strengthens with administration - need more pyridostigmine
Depolarizing vs Nondepolarizing NMBAs for myasthenia gravis
Resistance to succ, very sensitive to nondepolarizing, use cisatracurium if necessary
Greatest risk for postoperative respiratory failure with myasthenia gravis (5 items)
Duration of diagnosis over 6 years, concomitant pulmonary disease, PIP 750 mg/day, vital capacity
Lambert-Eaton Myasthenic Syndrome is what?
Autoimmune destruction of presynaptic voltage-gated calcium channels at nerve terminal - reduced ACh at motor-end plate
What muscles are affected by Lambert-Eaton myasthenic syndrome?
Originates in lower extremities and spreads upward
Depolarizing vs nondepolarizing NMBAs for Lambert-Eaton myasthenic syndrome
Sensitive to both, avoid – less response to anticholinesterases
Duchenne’s muscular dystrophy pathophysiology
Failure to code and produce dystrophin, fat starts to grow in areas where muscle cannot regrow
Depolarizing vs nondepolarizing NMBAs for Duchenne’s muscular dystrophy
AVOID SUCC– risk for rhabdomyolysis – causing massive hyperK = hypermetabolism and cardiac arrest, longer than normal recovery time for non-depolarizing
Rhabdomyolysis vs MH
Rhabdo will have really red urine output quickly - happens later with MH
CPK levels and Duchenne’s muscular dystrophy
Will be elevated in early disease - some muscle disease, late disease will have lower levels due to muscle loss
Myotonic dystrophy- steinerts
Repeats cytosine, thymine and guanine with severity related to number of extra trinucleotide repeats - extra Ca2+ availability.
Depolarizing vs nondepolarizing and myotonic dystrophy
SUCC CONTRAINDICATED - would have repeated fasciculations. Cisatracurium ND-NMBA of choice- normal to prolonged DOA, AVOID reversal (aggravates myotonia). Peripheral nerve stimulator likely inaccurate
Triad of myotonic dystrophy
Mental retardation, frontal baldness in males, presenile cataracts
Treatment of severe myotonia
IV phenytoin, IM quinine, or IM procaine
Demerol and myotonic dystrophy
Use it! Shivering induces myotonia, increases oxygen consumption– avoid hypothermia
Glucose-6-phosphatase deficiency is?
Impaired glycogenolysis, causes repetitive fasting hypoglycemia, lactic acidosis, lipotoxicity.
Anesthesia considerations with Glucose-6-phosphatase deficiency
AVOID LR (unable to convert lactic acid to glycogen), monitor glucose
Acid Maltase Deficiency (Pompe’s disease) - is and anesthetic consideration?
Rapidly progressive weakness and enlargement of tongue, heart and liver– propofol may cause reduction in afterload precipitating MI
Hypokalemic periodic paralysis is?
Defect in VGCa channels - decreases potassium = prevention of action potential
Hyperkalemic periodic paralysis is?
Defect in VGNaChannels - prevents generation of AP.
Malignant hyperthermia is?
Mutation of ryanodine receptor of many different genes (mostly 19)- uncontrolled release of Ca removes inhibition of troponin and increases ATP activity.
Which patients are at increased risk for MH?
Duchenne’s MD, central core disease, osteogenesis imperfecta, king-denborough syndrome, ortho joint-dislocation repair, opthalmic ptosis and strabismus, ENT cleft palate, T and A, dental, family history, intolerance to caffeine, unexplained fevers/muscle cramps, trismus with induction, baseline CK chronically elevated, positive halothane-caffeine contracture test
What medications to avoid with autonomic dysfunction?
Indirect acting pressors (ephedrine)
Guillain-Barre syndrome and hemodynamic response with anesthesia
Autonomic dysfunction creates wide fluctuations in BP with absent cardiac compensation to PEEP, blood loss and postural changes
Regional anesthesia and autonomic dysfunction
Putting numbing medications on nerves that are already struggling is a bad idea
Charcot-Marie-Tooth syndrome and depolarizing vs nondepolarizing medications
Sensitive to ND and reduced response to Succ with increased risk for exaggerated hyperkalemic resopnse
Upper motor neuron disease - where is the damage located?
Frontal cortex or tracts
Lower motor neuron disease - where is the damage located
Ventral horn of spinal cord - NO SUCC
Multiple sclerosis and regional type best used, temperature related anesthesia considerations
avoid spinal, ok for epidural, and increase by 0.5 degree may block conduction across demyelinated axons
Benadryl and parkinson’s disease
Increases muscle tension and tremor
Parkinson’s disease treatment aims
Increasing concentration of dopamine or decreasing neuronal effects of ACh
Side effects of LevoDopa
Orthostatic hypotension (catecholamine deplation) and N/V (dopamine stimulating medullary CRTZ)
Alzheimer’s disease treatment
cholinesterase inhibitors slow deterioration of mental status (tacrine, donepezil, galantamine, rivastigmine)– prolong succ, resistance to nondepolarizers
Postpolio syndrome main anesthesia consideration
Extreme sensitivity to anesthesia drugs with delayed awakening due to poliovirus damage to RAS
Neurofibromastosis main anesthesia concerns
Consider potential for pheo, tumors are highly vascular - be prepared for blood loss
