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Serotonin Syndrome





  • A potentially life-threatening adverse drug reaction due to ↑ CNS serotoninergic activity, characterized by the mnemonic MAD HOT: 

    • yoclonus

    • utonomic instability 

    • elirium, D iarrhea, 

    • HOT (fever) 

  •  It is seen with therapeutic medication use, drug interactions, & self-poisoning





  • Multisystem effects of serotonin excess:

    • CNS: seizure, altered LOC

    • CVS: tachycardia & HTN, autonomic instability, arrhythmia

    • MSK: rigidity, rhabdomyolysis, hyperkalemia & renal failure

    • Hyperthermia; DIC

  • Psychiatric patient: co-operation, informed consent/substitute decision maker 



Anesthetic Management


  • Stop offending agent 

  • Admit to ICU/HAU 

  • Supportive care & sedation: 

    • Benzodiazepines very useful for sedation 

    • Support ventilation & oxygenation 

    • Fluid resuscitation 

    • Treat hyperthermia 

  • Autonomic instability:

    • Hypotension: use direct acting vasopressors, reduced doses initially

    • Hypertension: use phentolamine, nitroprusside, esmolol

  • Specific antidote is cyproheptadine (potent antihistamine & serotonin antagonist):  

    • Initial: 12 mg followed by 2 mg every 2 hours or 4-8 mg every 6 hours

    • DO NOT use bromocriptine (a serotonin agonist, may exacerbate serotonin syndrome), dantrolene (no evidence) 

  • Rule out other differential diagnosis (e.g., MH, NMS, thyrotoxicosis) 

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