Syndrome Specific Management

Syndromic specific management involves the following:

Serotonin syndrome

  • General measures and supportive treatment as described previously.
  • Discontinue causative agent
  • Patients with serotonin syndrome with severe hypertension and tachycardia should be treated with short acting cardiovascular agents such as esmolol or nitroprusside [14]. Longer acting agents such as propranolol should be avoided due to the autonomic instability in this group of patients [14]
  • If supportive measures are not leading to an improvement then the antidotal therapy in cases of serotonin syndrome is cyproheptadine 12 mg orally or via NG tube [14]
  • Other agents such as olanzapine, chlorpromazine, bromcriptine or dantrolene are not recommended for use in the treatment of serotonin syndrome [14]

Neuroleptic malignant syndrome

  • General measures and supportive treatment as described previously
  • Discontinue causative agent
  • There is little data on the use of specific drugs in the treatment of neuroleptic malignant syndrome – most data is from case reports. The use of the following agents has been described:
  • Bromocriptine (a dopamine agonist) 2.5-10 mg 6 hourly [9]
  • Amantadine 100 mg orally has been used as an alternative to bromocriptine [9]
  • Dantrolene 1-2.5 mg/kg up to a maximum of 10 mg/kg/day. This is the treatment for malignant hyperthermia but its use has been described in neuroleptic malignant syndrome [9]

Anticholinergic syndrome

  • Supportive and general measures as previously described including benzodiazepines for the management of agitation and seizures. Phenothiazines and butyrophenones are themselves anticholinergic so their use should be avoided in anticholinergic toxicity [11]
  • Sodium bicarbonate should be used in the case of arrhythmias or prolonged QRS intervals related to the anticholinergic poisoning
  • Most patients with anticholinergic syndrome improve with supportive care alone. Patients with features of both peripheral and moderate central toxicity may benefit from treatment with physostigmine 0.5-2 mg over 5 minutes with continuous cardiac monitoring [11]. Physostigmine is uncommonly used and should only be used after consultation with NPIS

Sympathomimetic syndrome

  • General measures and supportive treatment as described previously
  • There is no specific antidote to treat the hyperthermia in sympathomimetic poisoning. Treatment should aim for control of hyperthermia by reducing excessive muscle activity and supportive care to normalise vital signs
  • Treatment might also be required for associated features such as hyponatraemia, hypertension and myocardial ischaemia
  • Sympathomimetics such as cocaine and MDMA might also cause serotonin toxicity. If there are features of serotonin toxicity as suggested by the Hunter diagnositic criteria [8] then consider treatment with cyproheptadine alongside supportive measures

Malignant hyperthermia syndrome

  • Immediate discontinuation of causative agents and stop surgery as soon as possible
  • Hyperventilate with 100% oxygen and maintain anaesthesia with opioids and hypnotic drugs [12,13]
  • Supportive and cooling measures as described previously
  • Dantrolene is the treatment for malignant hyperthermia in doses of 2.5 mg/kg repeated every 5 minutes until symptoms resolved or maximum dose of 10 mg/kg reached [12,13]
  • The patient should be monitored closely during treatment including the core temperature, cardiac rhythm, serial arterial gases and electrolytes. The patient should be managed on ICU for signs of recurrence for at least 24 hours