Serotonin Syndrome
Background
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A potentially life-threatening adverse drug reaction due to ↑ CNS serotoninergic activity, characterized by the mnemonic MAD HOT:
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M yoclonus
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A utonomic instability
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D elirium, D iarrhea,
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HOT (fever)
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It is seen with therapeutic medication use, drug interactions, & self-poisoning
Considerations
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Multisystem effects of serotonin excess:
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CNS: seizure, altered LOC
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CVS: tachycardia & HTN, autonomic instability, arrhythmia
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MSK: rigidity, rhabdomyolysis, hyperkalemia & renal failure
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Hyperthermia; DIC
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Psychiatric patient: co-operation, informed consent/substitute decision maker
Anesthetic Management
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Stop offending agent
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Admit to ICU/HAU
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Supportive care & sedation:
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Benzodiazepines very useful for sedation
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Support ventilation & oxygenation
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Fluid resuscitation
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Treat hyperthermia
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Autonomic instability:
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Hypotension: use direct acting vasopressors, reduced doses initially
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Hypertension: use phentolamine, nitroprusside, esmolol
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Specific antidote is cyproheptadine (potent antihistamine & serotonin antagonist):
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Initial: 12 mg followed by 2 mg every 2 hours or 4-8 mg every 6 hours
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DO NOT use bromocriptine (a serotonin agonist, may exacerbate serotonin syndrome), dantrolene (no evidence)
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Rule out other differential diagnosis (e.g., MH, NMS, thyrotoxicosis)