Cyanide

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Cyanide

• By Jack Hay
• 3/2/06

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Introduction

• Potent cellular toxin with nefarious history
• Poisoning can occur from
• Occupation, accidental ingestion of
  pre-metabolites
• Sodium nitroprusside infusion
• Cyanogenic glycoside plant ingestion
• Inhalation of burning plastics

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Sources of Exposure

• Industrial
• Hydrogen cyanide gas and cyanide salts
• Smoke inhalation
• Fires or Burning of vinyl or wool
• Chronic
• Workers have higher thyroid dz and B12 deficiency
• Other
• Suicides, homicides, acetonitrile-containing
  cosmetics

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Sources of Biodegradation
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Biochemical Toxicology

• Inhibits final step of oxydative phosphorylation
• Pyruvate ? lactate (anaerobically) ? severe
  metabolic acidosis
• Alters calcium homeostasis
• Constricts pulmonary and coronary vessels

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Clinical Time CourseRoutes of Exposure

• Inhalation ? immediate symptoms
• Ingestion ? within minutes
• Delayed if requires metabolic activation
• Acetonitrile nail remover releases HCN after
  hepatic oxidative metabolism

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Did I Just Take Cyanide?
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Cyanide Clinical Features

• History
• Watch for delayed toxicity with ingestion
• CNS
• Headache
• Drowsiness
• Seizures
• Coma

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Cyanide Clinical Features

• Cardiovascular
• Tachycardia
• HTN
• Collapse/asystole
• Pulmonary
• Dyspnea
• Tachypnea
• Apnea

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Cyanide Clinical Features

• Smell of bitter almonds on exam
• Laboratory
• Severe metabolic acidosis
• Absence of met acidosis precludes cyanide
  toxicity
• Toxic levels correlate with lactate levels gt 10
  mmol/L independent of CO level
• in smoke inhalation

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Differential Diagnosis

• Consider in a poisoned pt with normal Pao2 and
  high anion gap metabolic acidosis

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Cyanide Tanks in Brooklyn Mines, CA
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Treatment

• Antidote kit
• Amyl nitrate ampule (for inhalation)
• Sodium nitrite 3
• 10mL (300mg)
• Sodium thiosulfate 25
• 50mL (12.5g)

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Nitrites

• Methemoglobin-formation ability may not be the
  key to their effectiveness
• Side effects include hypotension
  methemoglobinemia
• Adjust pediatric dose according to hemoglobin
  level

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Sodium Thiosulfate

• Given after nitrite
• Enhances enzymatic thiocyanate formation
• Form of cyanide excreted by kidneys
• Limited toxicity makes it safe empirically
• Helpful as sole inhalation therapy where
  subsequent CO exposure is of concern

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Oxygen

• Enhances therapeutic efficacy of antidotes
• Hyperbaric oxygen works only with concomittant CO
  poisoning

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Other Therapies

• Dicobalt edetate (Kelocyanor)
• First line in UK
• Toxicity great if cyanide not present
• DMAP
• German alternative
• Hydroxocobalamin (Vit B12a)
• Choice in France
• Used in combination with sodium thiosulfate

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Supportive Care

• 100 oxygen by mask
• Cardiac monitoring
• IV line placement
• Treat hypotension with IVF and pressors
• Treat seizures with benzodiazepines

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Decontamination

• Gastric lavage/charcoal AFTER resuscitation
• Topical exposures require copious water irrigation

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Cyanide Carboxyhemoglobin

• Hypotension in a bradycardic, comatose patient is
  not a contraindication for sodium nitrite
• Empiric nitrite administration to patients with
  elevated carboxyhemoglobin, however, is
  relatively contraindicated
• Potential for methemoglobinemia which further
  decreases oxygen-carrying capacity

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Laboratory Evaluation
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Laboratory Evaluation

• ABG (confirm gap metabolic acidosis)
• Check for carboxyhemoglobin
• Cant wait for other tests before treating
• Whole-blood cyanide can be tested for later
  review
• Fatal at gt 2.5 mcg/mL
• Serum lactate gt 10 mmol/L in smoke inhalation
  correlates with cyanide toxicity

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Disposition

• ADMIT if treated with antidote
• ADMIT if chance for delayed presentation
• ADMIT for cardiac monitoring
• ADMIT for risk of cardiac arrest
• ADMIT you slept through this lecture

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