ACMT Toxicology Visual Pearls: Painful Foot

Answer: 2

Hydrofluoric Acid

What is Hydrofluoric Acid

Hydrofluoric Acid (HF) is widely used in industrial settings as well as in household cleaning products such as rust removers. Dermal exposure can cause significant delayed effects, and life- threatening systemic effects can occur through any route of exposure. [1,2] Fatal exposures to HF share features of hypocalcemia, hypomagnesemia, and often hyperkalemia. Fatalities occur as a result of sudden onset myocardial conduction failure or ventricular fibrillation [1-4].

Clinical Presentation – Dermal [1, 5]

• Severity of pain and tissue injury are directly related to the HF concentration.
• Household products with low HF concentrations < 20% typically have a delay of hours before pain develops; products with HF concentrations > 20% cause pain and tissue damage within minutes of the exposure.
• Tissue may initially appear “normal” but can progress to develop hyperemia and white discoloration.
• Fluoride ions bind avidly to extracellular and intracellular stores of calcium and magnesium leading to local cellular dysfunction and necrosis.
• Deposition of calcium fluoride in tissues may explain systemic effects as well as severity of pain.
• With high concentrations and/or high body surface area burns, systemic effects include hypocalcemia, hypomagnesemia, hyperkalemia, and cardiac dysrhythmias.

Treatment [1, 3-12]

• For dermal exposure, remove clothing and copiously irrigate with water or saline
• Be careful to avoid secondary exposure to health care providers
• Apply topical calcium gel directly to the affected area(s)
• Hand burns can be placed in a glove containing calcium slurry
• Local injection of dilute calcium gluconate and intravascular administration of calcium have also been described, however extreme caution should be exercised if considering these therapies [1,5-8].
• For potentially life-threatening ingestions, a nasogastric tube can be inserted to both aspirate GI contents and administer of calcium or magnesium salts [3,4,9,11,12].
• Obtain EKG and institute cardiac monitoring
• Aggressively replace hypocalcemia and hypomagnesemia

Disposition

• Patients with intentional ingestions, extensive burns, or signs of systemic toxicity should be admitted to an intensive care setting,
• Only asymptomatic patients with mild dermal exposure controlled with analgesics, and no additional symptoms, are candidates for discharge.
• Consult your regional poison control center or medical toxicologist for patients with pain not responding to topical treatment, patients with significant inhalation exposure, or any patients ingesting HF.

Clinical Pearls

• Hydrofluoric acid is considered a weak acid and causes local and systemic toxicity secondary to the interaction of fluoride ions with calcium (Ca2+) and magnesium (Mg2+).
• Dermal exposure to HF causes severe pain often before any physical manifestations are evident.
• Therapy for local dermal toxicity includes topical calcium and, in some cases, intradermal/intravascular administration of calcium.
• Patients with greater than 2.5% body surface area HF burns should have an ECG along with serum calcium, magnesium, and potassium levels checked and closely monitored.
• In oral ingestions, NG decontamination and oral administration of calcium and magnesium salts should be strongly considered due to the high mortality with this route of ingestion.