Rosen & Barkin's 5-Minute Emergency Medicine Consult (456 page)

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Authors: Jeffrey J. Schaider,Adam Z. Barkin,Roger M. Barkin,Philip Shayne,Richard E. Wolfe,Stephen R. Hayden,Peter Rosen

Tags: #Medical, #Emergency Medicine

BOOK: Rosen & Barkin's 5-Minute Emergency Medicine Consult
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  • Primarily for depression
  • Selegiline, a selective monoamine oxidase B inhibitor, is sometimes used to treat Parkinson disease, and also comes in a transdermal preparation.
  • Monoamine oxidase inhibitor (MAOI) pharmacologic actions:
    • Disruption of equilibrium between endogenous monoamine synthesis and degradation, resulting in:
      • Increased neural norepinephrine levels
      • Downregulation of several receptor types
    • Inhibition of irreversible (noncompetitive) enzyme
    • Inhibition of other B
      6
      -containing enzymes
  • MAO: Principal inactivator of neural bioactive amines:
    • MAO A:
      • Present in the gut and liver
      • Protects against dietary bioactive amines
    • MAO B:
      • Present in neuron terminals and platelets
      • Sympathomimetic amines: Types of bioactive amines
ETIOLOGY
  • MAOI overdose:
    • Toxicopharmacology poorly understood
    • MAO inhibitors: Amphetamine-like in structure:
      • Early: Indirect sympathomimetic effect
      • Late: Sympatholytic response (hypotension)
  • MAOI hypertensive crisis syndrome:
    • Results from impaired norepinephrine degradation and large norepinephrine release precipitated by an indirect- or mixed-acting sympathomimetic agent
    • Common precipitants: Tyramine, cocaine, amphetamines
  • Serotonin syndrome (SS):
    • Commonly results from exposure to combinations of agents that affect serotonin metabolism or action
    • Increases serotonin synthesis: Tryptophan
    • Increase serotonin release:
      • Indirect- and mixed-acting sympathomimetic agents and dopamine receptor agonists
    • Decrease serotonin reuptake:
      • Selective serotonin reuptake inhibitors
      • Tricyclic antidepressants
      • Newer antidepressants: Trazodone, nefazodone, venlafaxine
      • Phenylpiperidine opioids: Meperidine, dextromethorphan, tramadol, methadone, propoxyphene
    • Direct serotonin receptor agonists:
      • Buspirone, sumatriptan, lysergic acid diethylamide
    • Decrease serotonin breakdown:
      • MAOIs
    • Increases nonspecific serotonin activity:
      • Lithium
DIAGNOSIS
SIGNS AND SYMPTOMS
  • MAOI overdose:
    • Delayed onset (6–12 hr)
    • Initial hypertension with headache
    • Hyperadrenergic activity:
      • Tachycardia
      • Hypertension
      • Mydriasis
      • Agitation
    • Neuromuscular excitation:
      • Nystagmus
      • Hyperreflexia
      • Tremor
      • Myoclonus
      • Rigidity
      • Seizures
    • Hyperthermia
    • Associated complications:
      • Rhabdomyolysis
      • Renal failure
      • Disseminated intravascular coagulation (DIC)
      • Acute respiratory distress syndrome (ARDS)
  • MAOI hypertensive crisis syndrome (MAOI interaction with drug or food):
    • Hypertension
    • Tachycardia or bradycardia
    • Hyperthermia
    • Headache, usually occipital
    • Altered mental status
    • Intracranial hemorrhage
    • Seizures
  • SS:
    • Increased neuromuscular activity
    • Increased deep tendon reflexes:
      • Lower extremity may be greater than upper
    • Tremor
    • Myoclonus
    • Rigidity (when severe)
    • Autonomic nervous system hyperactivity:
      • Hyperthermia
    • CNS:
      • Agitation
      • Hallucinations
      • Delirium
      • Coma
    • Diarrhea
    • SS vs. neuroleptic malignant syndrome (NMS):
      • Both present along a spectrum of severity (mild to severe)
      • Onset: Hours (SS) vs. days (NMS)
      • Gastrointestinal symptoms: May be present (SS) vs. absent (NMS)
      • Only drug/medication history may differentiate in many cases
History
  • Time of ingestion
  • Bottle available
  • Intentional or accidental
  • Coingestions
Physical-Exam
  • Neuromuscular hyperactivity:
    • Myoclonus
    • Rigidity
    • Tremors
    • Hyperreflexia
  • Autonomic hyperactivity:
    • Tachycardia or bradycardia
    • Fever
    • Diaphoresis
  • Altered mental status:
    • Agitation, confusion, or excitement
ESSENTIAL WORKUP
  • History of ingested substances
  • Rectal temperature monitoring as indicated
  • Blood pressure/cardiac monitoring
DIAGNOSIS TESTS & NTERPRETATION
Lab
  • Urinalysis:
    • Blood
    • Myoglobin
  • Electrolytes, BUN/creatinine, glucose:
    • Hypoglycemia may contribute to altered mental status.
    • Acidosis may accompany severe toxicity.
    • Rhabdomyolysis may cause renal failure.
    • Hyperkalemia—life-threatening consequence of acute renal failure
  • Coagulation profile to monitor for potential DIC:
    • INR, prothrombin time, partial thromboplastin time, platelets
  • Creatinine kinase:
    • Markedly elevated in rhabdomyolysis
  • Urine toxicology screen:
    • May be positive for amphetamines, given the structural similarities between some MAOIs and amphetamines
  • Aspirin and acetaminophen levels if suicide attempt a possibility
  • Arterial blood gas
Imaging
  • Chest radiograph:
    • ARDS
  • Head CT if significant headache or altered mental status or focal neurologic signs:
    • Subarachnoid hemorrhage, intracerebral bleed
Diagnostic Procedures/Surgery

Lumbar puncture for:

  • Suspected meningitis (headache, altered mental status, hyperpyrexia)
  • Suspected subarachnoid hemorrhage and CT normal
DIFFERENTIAL DIAGNOSIS
  • Hyperthermia:
    • Infection
    • Hyperthyroidism
    • Heat stroke
    • Anatomic thalamic dysfunction
    • NMS
    • Malignant hyperthermia
    • Malignant catatonia
    • Ethanol or drug withdrawal
    • Anticholinergic toxicity
    • Sympathomimetic overdose
    • Cocaine-associated delirium/rhabdomyolysis
    • Salicylate toxicity
    • Theophylline toxicity
    • Nicotine toxicity
  • Hypertension:
    • Hypoglycemia
    • Carcinoid syndrome
    • Pheochromocytoma
    • Accelerated renovascular hypertension
    • Ethanol or drug withdrawal
    • Sympathomimetic toxicity
TREATMENT
PRE HOSPITAL
  • Patient may be uncooperative or violent.
  • Secure IV access.
  • Protect from self-induced trauma.
INITIAL STABILIZATION/THERAPY
  • Airway, breathing, and circulation (ABCs)
  • IV access and fluid resuscitation if hypotensive
  • Oxygen
  • Cardiac monitor
  • Naloxone, thiamine, D50W (or Accu-Chek) if altered mental status
ED TREATMENT/PROCEDURES
  • Gastrointestinal decontamination:
    • In potential life-threatening ingestions gastric lavage may be carefully considered if within
      1 hr
      of ingestion
    • Administer activated charcoal
  • Hyperthermia:
    • Benzodiazepines if agitated
    • Active cooling if temperature >40°C:
      • Tepid water mist
      • Evaporate with fan
    • Paralysis:
      • Indicated if muscle rigidity and hyperactivity contributing to persistent hyperthermia
      • Nondepolarizing agent (e.g., vecuronium)
      • Avoid succinylcholine
      • Intubation; mechanical ventilation
    • Administer acetaminophen.
    • Apply cooling blankets.
  • Severe, malignant hypertension:
    • Nitroprusside (for MAOI overdose)
    • Calcium-channel blocker or phentolamine (for MAOI + food interaction)
    • Use short-acting IV agent that can be rapidly “turned off.”
  • Hypotension:
    • Initially bolus with isotonic crystalloid solution
    • If no response, administer norepinephrine.
    • Dopamine may be ineffective
  • Dysrhythmias (premorbid sign in MAOI overdose):
    • Treatment based on dysrhythmia
  • Seizures:
    • Benzodiazepines
    • Barbiturates if benzodiazepines unsuccessful
    • Pyridoxine for refractory seizures
  • Rigidity:
    • Benzodiazepines
    • Paralysis with vecuronium, endotracheal intubation, and mechanical ventilation
  • ARDS:
    • Oxygen
    • Intubation and positive end-expiratory pressure as indicated
  • DIC:
    • Fresh-frozen plasma
    • Platelets
    • Whole-blood transfusions
  • Rhabdomyolysis:
    • IV isotonic crystalloid solution
    • Maintain hydration to ensure adequate urine output
  • Specific treatment for SS:
    • Mainstay: Supportive care, discontinuation of offending agents
    • Nonselective serotonin antagonist:
      • Cyproheptadine
ALERT

Phentolamine
contraindicated in MAOI overdose
(results in unopposed β-agonist)

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