Hydrofluoric acid

Background

• Used in both commercial and home setting
  • Rust remover (most common home use)
  • Glass etching, chrome and other metal cleaning, 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

Hydrofluoric acid (HF) burns, which were not evident until a day after exposure.

Hydrofluoric acid burn

• Skin exposure
  • Burns
  • Pain out of proportion to extent of burn
• Ophthalmic exposure
  • Eye pain
  • Erythema
• Ingestion
  • Nausea and vomiting
  • Abdominal pain
• Inhalation
  • Shortness of breath
  • Throat pain/burning
• Signs/symptoms of hypocalcemia and hypomagnesemia
  • Can lead to QTc interval prolongation and cardiac arrhythmias, the primary cause of death in HF burns

Differential Diagnosis

Caustic Burns

• Caustic ingestion
• Caustic eye exposure (Caustic keratoconjunctivitis)
• Caustic dermal burn
• Airbag-related burns
• Hydrofluoric acid
• Tar burn
• Cement burn

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 (KY-Jelly) OR
    • Mix 25mL 10% calcium gluconate solution with 75mL water-soluble lubricant (KY-Jelly)
  • 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

Medication Dosing

Calcium gluconate Topical gel (3.5g powder in 150mL lubricant or 25mL 10% soln in 75mL lubricant) Topical — Rub into affected area 10-15min; pain relief is treatment endpoint Calcium gluconate 5% intradermal injection (max 0.5mL/cm2) Intradermal — Dilute 10% calcium gluconate 1:1 with sterile NS Calcium gluconate 10mL of 10% in 40mL NS via Bier block (20min dwell time) IV regional (Bier block)

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

See Also

• Caustics
• Burn