Background
Hydrofluoric (HF) acid, one of the strongest inorganic acids, is used mainly for industrial purposes (eg, glass etching, metal cleaning, electronics manufacturing). Hydrofluoric acid also may be found in home rust removers. Exposure usually is unintentional and often is due to inadequate use of protective measures.
Hydrofluoric acid burns are a unique clinical entity. Dilute solutions deeply penetrate before dissociating, thus causing delayed injury and symptoms. Burns to the fingers and nail beds may leave the overlying nails intact, and pain may be severe with little surface abnormality.
Severe burns occur after exposure of concentrated (ie, 50% or stronger solution) hydrofluoric acid to 1% or more body surface area (BSA), exposure to hydrofluoric acid of any concentration to 5% or more BSA, or inhalation of hydrofluoric acid fumes from a 60% or stronger solution. The vast majority of cases involve only small areas of exposure, usually on the digits.
A unique feature of hydrofluoric acid exposure is its ability to cause significant systemic toxicity due to fluoride poisoning.
Pathophysiology
The two mechanisms that cause tissue damage are corrosive burn from the free hydrogen ions and chemical burn from tissue penetration of the fluoride ions.
Fluoride ions penetrate and form insoluble salts with calcium and magnesium. Soluble salts also are formed with other cations but dissociate rapidly. Consequently, fluoride ions release, and further tissue destruction occurs.
Systemic toxicity occurs secondary to depletion of total body stores of calcium and magnesium, resulting in enzymatic and cellular dysfunction, and ultimately in cell death. Majority of deaths are resulting from cardiac arrhythmias that were precipitated by hypocalcaemia and consequent hyperkalemia. [1, 2, 3]
Epidemiology
US frequency
More than 1000 cases of hydrofluoric acid exposure are reported annually. Actual incidence rate is unknown.
In a review of 15 years' experience with hydrofluoric acid burns at one center, hydrofluoric acid burns accounted for 35 (17%) patients out of 205 who were admitted for chemical burns; all of these patients were men. [4]
Sex
Males are affected more commonly by hydrofluoric acid burns, which reflects occupational patterns.
Age
The majority of hydrofluoric acid exposures occurs in adults.
Prognosis
Prognosis varies depending on burn severity and site. Poor prognosis follows fluoride inhalation.
Local effects of hydrofluoric acid burns include tissue destruction and necrosis. Burns may involve underlying bone. Systemic fluoride ion poisoning from severe burns may be associated with hypocalcemia, hyperkalemia, hypomagnesemia, and sudden death. Urinary fluoride levels have been correlated with severity of burns. [5] Deaths have been reported from concentrated acid burns to as little as 2.5% BSA.
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Grade 1 hydrofluoric (HF) acid burns of the fingertips. The patient has severe pain (maximum middle digit) with only minimal redness of the nail beds.
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Grade 3 hydrofluoric (HF) acid burns of the fingertips. Note how the nailbed and tip of the fingers have severely been injured, but the nails show no damage.
