Download GBS,MG crisis, NMS and Serotonin syndrome

GBS,MG crisis, NMS and
Serotonin syndrome
雙和醫院神經科 洪千岱醫師
Guillain-Barre syndrome
• Acute immune polyradiculoneuropathy predominantly
characterized by flaccid weakness with areflexia, which in its
most severe form can cause neuromuscular respiratory failure.
• The syndrome is most often caused by demyelination (acute
inflammatory demyelinating polyradiculoneuropathy [AIDP]),
but an axonal type of greater severity exists (acute motor
axonal neuropathy [AMAN]).
• This section will focus on the diagnosis and management of
patients with severe GBS associated with neuromuscular
respiratory failure and requiring ICU care
Clinical features
• The hallmark of the syndrome is the rapid development of
ascending weakness associated with loss of deep tendon
reflexes.
• Cranial nerve deficits are present in approximately half of
patients with GBS.
• Dysautonomia is a major feature of severe GBS. Involvement of
autonomic fibers can lead to cardiac arrhythmias,
hemodynamic instability, gastroparesis, paralytic ileus, and
urinary retention.
Respiratory Failure in GBS
• Approximately 25% of patients with classic GBS.
• Diaphragmatic failure can develop very suddenly and force
emergency intubation.
• Checking for the presence of a paradoxical breathing pattern.
• A shorter interval between the onset of symptoms and
hospitalization, more severe appendicular weakness and
presence of bulbar or facial weakness are associated with a
higher risk of respiratory insufficiency.
• Patients with axonal GBS are also at increased risk of requiring
mechanical ventilation.
Diagnostic work-up
• A diagnosis of Guillain-Barre syndrome can be confirmed by
electrophysiology and supported by the presence of elevated
protein without increased nucleated cell count in the CSF.
• Prolonged F-wave latency is usually the earliest sign of GuillainBarre syndrome in nerve conduction studies.
• Protein elevation in the CSF may be delayed and is not present
in all cases.
Management
• The first management priority when evaluating a patient with
Guillain-Barre syndrome is to determine whether the patient
needs admission to an intensive care unit.
• Patients with Guillain-Barre syndrome with severe and rapidly
progressive weakness should always be admitted to the
intensive care unit for close monitoring.
• Intubation and initiation of mechanical ventilation should not
be delayed in patients with Guillain-Barre syndrome who
develop early signs of ventilatory insufficiency or have
substantial bulbar weakness.
Management
• Immune therapy with plasma exchange or IV immunoglobulin
(IVIg) is effective in patients withGBS.
• A full course of plasma exchange usually consists of five
sessions (plasma exchange volume 250 mL/kg each) over
alternating days.
• The full dose of IVIg is 2 g/kg (administered either as 0.4
g/kg/d for 5 consecutive days or 1 g/kg/d for 2 days).
• Plasma exchange and IVIg are comparably effective
• The combination of plasma exchange followed by IVIg is not
more effective than either treatment alone.
• Corticosteroids are not beneficial in GBS.
Myasthenic Crisis
• The presence of respiratory failure and the need for invasive or
noninvasive mechanical ventilation.
• About one-fifth of patients with MG will have at least one crisis
during their disease course.
• Common triggers include infections, surgery, and medication
changes
Clinical Features
• Ptosis, inability to sustain upgaze, bilateral facial weakness, jaw
weakness, flaccid dysarthria, and very weak and fatigable limb
muscles.
• Cough is often weak. Poor vital capacity can be surmised when
the patient cannot complete sentences and cannot count
aloud from 1 to 20 in a single breath.
• A paradoxical breathing pattern is a reliable marker of
diaphragmatic weakness.
• Cholinergic overactivity: increased miosis, salivation, and
bronchial secretions, sweating, bradycardia, diarrhea, and,
rarely, fasciculations
Diagnostic Evaluation
• Serology, electrophysiology, or a therapeutic trial with a
cholinesterase inhibitor.
• In the ICU, these tests are only necessary when the patient
does not have a previously established diagnosis of MG or the
diagnosis is in question.
• The value of pulmonary function tests in MG is much less well
established than in GBS.
• The fluctuating nature of weakness in patients with MG may
result in variable and unpredictable measurements with serial
spirometry.
Pharmacological Treatment
• Plasma exchange and IVIg accelerate recovery in patients with
MG exacerbation.
• All patients with myasthenic crisis should receive
corticosteroids. However, the ideal form of administration (eg,
oral versus IV, optimal dose) in myasthenic crisis is not well
established.
• Pyridostigmine can be transiently discontinued after intubation
to reduce respiratory secretions. Yet, pyridostigmine should
never be stopped when the patient is receiving noninvasive
ventilation and should always be restarted in adequate doses
before initiating weaning from invasive ventilation
Neuroleptic malignant syndrome (NMS)
• Idiosyncratic abrupt reaction to antidopaminergic drug treatment
• Causative agents:
–
–
–
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“classic” neuroleptics, however
the “atypical” agents have also been implicated
other dopamine blocking drugs
abrupt withdrawal of dopaminergic agents
• Risk of NMS
– male, young age, concomitant use of lithium SSRIs, high ambient temperatures,
hyponatremia, dehydration, physical exhaustion, mental retardation,
extrapyramidal syndromes, psychomotor agitation and a previous episode of
NMS.
Clinical Phenomenon
• Classic tetrad: hyperthermia, rigidity, altered mental status and
dysautonomia
• Can be associated with other signs: action and/or rest tremor,
dystonia, chorea, myoclonus, seizures, ataxia, hyporeflexia and
extensor plantar reflexes
• May be associated with laboratory changes : High CK (>1000
IU/L), impaired liver, renal and coagulation status tests,
leukocytosis, electrolyte disturbances, proteinuria and
rhabdomyolysis with myoglobinuria
Management
• Early recognition and offending medication withdrawal
• Supportive care includes correction of volume and electrolyte
imbalance, prevention of infection, thrombosis and pressure
ulcers, and body cooling.
• Patients with severe symptoms often require management in
an intensive care facility
• Pharmacological interventions
– benzodiazepines or dantrolene: reducing muscle rigidity
– reversing dopaminergic blockade: bromocriptine, levodopa or
amantadine
Management
• Finally, patients should be withdrawn of neuroleptics for, at
least, two weeks after the termination of management of the
acute phase of NMS.
• Restart the background neuroleptic agent: low doses, slow
titration, avoiding concomitant use of lithium, and close
observation to prevent dehydration and the initial symptoms
of NMS.
Serotonin syndrome (SS)
• Combined use of two or more agents that enhance serotonin
activity or concentration in the central nervous system
• Acute development of agitation, mental status changes,
myoclonus, incoordination, postural instability, hyperreflexia,
rigidity and dysautonomic features (diaphoresis, fever, diarrhea,
tachycardia and hemodynamic instability) after a change in
serotonergic drug regimen
• SS is not an idiosyncratic reaction, but a predictable one.
Offending drugs
• Inhibitors of serotonin reuptake (SSRIs, tricyclic
antidepressants, dextromethorphan, amphetamine and
cocaine)
• Inhibitors of serotonin metabolism (monoamine oxidase
inhibitors [MAOIs])
• Serotonin precursors (L-tryptophan)
• Enhancers of serotonin release (amphetamines, cocaine,
fenfluramine)
• Serotonin agonists (risperidone, sumatriptan, ergotamines)
• Nonspecific enhancers of serotonin activity, as lithium and
electroconvulsive therapy
Management
• Withdrawal of the offending agents
• Nonspecific 5-HT receptor blockers, such as cyproheptadine
and methysergide have been credited with shortening the
syndrome’s duration
• Others: benzodiazepines, chlorpromazine and propranolol
• Supportive measures include treatment of seizures, cardiac
arrhythmias, disseminated intravascular coagulation, muscle
rigidity and hyperthermia.
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