Hydrogen fluoride toxicity

Background

• Hydrogen fluoride (HF) is a byproduct of standard fire suppression systems. It is also used as rust remover and in glass etching, metal cleaning, and petroleum processing.
• Oral ingestion has very high mortality rate
• Onset and severity of symptoms correlated with concentration
  • Dilute solutions (<20%) may have delayed onset up to 24hr post-exposure
  • Moderate solutions (20-50%) develop symptoms within 1-8hr
  • Concentrated solutions (>50%) develop symptoms immediately
    • These patients are at highest risk for systemic toxicity/death
    • Pain immediately (even if wound appears minor) implies severe injury
• Burn itself may appear relatively minor
• Toxicity caused by binding of calcium and magnesium leading to electrolyte derangement and myocardial dysfunction

Clinical Features

• Exposure to HF may result in rapidly progressive or fatal respiratory failure despite minimal external evidence of injury.
• Symptoms include shortness of breath, cough, or hypoxia; there must be a high level of suspicion for HF inhalation.

Differential Diagnosis

Burns

• Smoke inhalation injury (airway compromise)
• Chemical injury
  • Acrolein
  • Hydrochloric acid
  • Tuolene diisocyanate
  • Nitrogen dioxide
• Systemic chemical injury
  • Carbon monoxide toxicity
  • Cyanide toxicity
• Specific types of burns
  • Caustic burns
    • Airbag-related burns
    • Tar burn
    • Cement burn
  • Electrical injuries
    • Lightning Injuries
• Associated toxicities
  • Carbon monoxide toxicity
  • Cyanide toxicity
  • Hydrogen fluoride toxicity

Evaluation

• Clinical diagnosis
• Trend calcium, magnesium, and potassium levels
  • Hydrofluoric acid chelates calcium and poisons the Na+/K+ pump
  • Expect hypocalcemia, hypomagnesemia, and hyperkalemia
• Monitor EKG for signs of electrolyte abnormality
  • QTc prolongation
  • Ventricular tachycardia

Management

• Decontamination: remove soiled clothing and irrigate thoroughly.
• Mainstay of treatment is application of calcium to affected area.

Cutaneous Burns

Minor injuries (<50 cm2 from dilute solutions <20%)

• Application of gel paste of Ca gluconate or benzalkonium Cl
  • Rub into affected area for 10-15min with pain relief being used as end-point of treatment
  • Calcium gel is commercially available (found in industrial first-aid kits)
  • Calcium gel can be made:
    • Mix calcium gluconate powder 3.5gm with 150mL water-soluble lubricant OR
    • Mix 25mL 10% calcium gluconate solution with 75mL water-soluble lubricant
  • Benzalkonium Cl is commercially available
  • If calcium gluconate is not available calcium chloride can be used

Severe injuries

• Treat with intradermal injections of 5% calcium gluconate
  • Prepare by diluting conventional 10% Ca gluconate with sterile NS in 1:1 ratio
  • Inject in and around the burned area in amount not to exceed 0.5mL per cm2

Refractory injuries

• Treat with intravenous infusion of calcium gluconate using Bier block
  • Place tourniquet proximal to exposure site on affected extremity and inject though IV distal to tourniquet
  • Inject 10 mL of 10% Ca gluconate diluted in 40 mL of saline and remove tourniquet after 20 min of dwell time
• In severe refractory cases may also infuse intra-arterial calcium gluconate
  • Deliver via arterial line placed proximal to injury in the same limb
  • Infuse 10 mL of 10% Ca gluconate diluted in 40mL of saline over 4 hr

Ocular burns

• Irrigate with saline for at least 5 min
• If persistent pain administer 1% calcium gluconate to eye (dilute 10% calcium gluconate with normal saline)
  • Consult ophthalmology due to irritation effect of calcium salts to eye

Ingestion

• If <1hr of ingestion, may consider NG tube for suction and gastric lavage
  • Follow lavage by 300mL 10% Ca gluconate down NGT
• Consider intubation for airway protection

Inhalation

• Consider in any patient with facial burns or exposure to HF in confined space
• Oxygen via NRB
• Nebulized 2.5% calcium gluconate
• Intubation may be required in severe cases

Systemic toxicity

• Administer calcium gluconate 100mg IV (10 mL of a 10% solution) over 2-3 minutes
• May also need to replete magnesium (4g IV over 20 minutes)
• May see QTc prolongation, cardiac arrhythmia, or obvious systemic illness
• Treat hyperkalemia as needed

Disposition

• Consultation with poison center and burn center transfer per Burn center criteria
• Admission for all patients with arrhythmia on ECG or severe electrolyte disturbance

Complications

• Bronchopneumonia can develop within a week.

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See Also

• Burns
• Caustics