Deaths from dermal, gastrointestinal, and pulmonary hydrofluoric acid (HF) exposures are well documented in the literature.13,23,68 In these cases, hypocalcemia is invariably present. Any body contact with HF (Chap. 107) can result in severe burns and death, depending on concentration, area exposed, and duration of exposure. The toxicity results from (a) release of free hydrogen ions; (b) complexation of fluoride with calcium and magnesium to form insoluble salts, which cause cellular necrosis; (c) liberation of potassium ions; and (d) cellular dehydration.12,19,42,44 Soluble salts of fluoride and bifluoride (eg, sodium, potassium, and ammonium) have all the toxicity associated with HF and should be managed accordingly. Following HF exposure, the gluconate salt of calcium is used topically and subcutaneously to manage minor to moderate cutaneous burns, intravenously to treat systemic hypocalcemia, and intraarterially to manage significant burns.2,12, 13, and 14,16,19,23,42,44,47,51,55,58,66,67,72 Experimental studies demonstrate that when concentrated HF burns are immediately flushed with water and then treated with topical calcium, burn size is significantly reduced.8 Management of HF burns with a topical dimethyl sulfoxide (DMSO)–calcium gluconate combination seems promising, but a randomized clinical trial has yet to be published.27 Although a DMSO preparation is not commercially available, a 2.5% calcium gluconate topical gel is marketed. In the event that the commercial preparation is inaccessible, a topical calcium gel can be prepared from calcium carbonate tablets, calcium gluconate powder or solution, and a water-soluble jelly such as K-Y Jelly (mix 3.5 g calcium gluconate powder or 35 mL of a 10% calcium gluconate solution or 10 g of calcium carbonate tablets or seven 500 mg crushed calcium gluconate tablets with 5 ounces of K-Y Jelly). An experimental study in rats demonstrated that iontophoretic delivery of calcium chloride appeared to enhance the delivery of calcium and to significantly reduce the burn area if applied within 30 minutes, and this may be a promising modality in the future.56,71
The chloride salt is also acceptable for topical therapy. However, calcium chloride should never be injected into tissues (subcutaneously, intramuscularly), since severe tissue necrosis can result.
In patients with severe topical HF exposures, aggressive administration of regional IV calcium using a Bier block technique (10 mL of 10% calcium gluconate in a total volume of 40 mL) or intraarterial calcium (10 mL of 10% calcium gluconate in 50 mL (total volume) of 5% dextrose solution over 4 hours) may be required, along with frequent serum calcium determinations to titrate the dose.27,64 One patient who was massively exposed to HF required a total of 267 mEq of calcium infused over a 24 hour period.23
In patients with life-threatening poisoning and particularly HF inhalation, simultaneous administration of IV, oral, and nebulized 2.5% calcium gluconate can be given to facilitate the availability of the maximum amount of calcium. To prepare nebulized calcium gluconate, mix 1.5 mL of 10% calcium gluconate solution with 4.5 mL of sterile water or 0.9% sodium chloride to make a 2.5% solution. For moderate to severe burns (generally from HF concentrations >10%) of the fingers and hands, an intraarterial calcium infusion may be more effective than local or IV therapy, although it is more invasive51,58,64,66,67 and more hazardous.58 A calcium gluconate solution (10 mL of 10%) mixed in 40 to 50 mL of 5% dextrose solution can be infused intraarterially over 4 hours followed by subsequent 40 to 50 mL intraarterial infusions after 4 hours when pain persists.66 Serum calcium, potassium, and magnesium concentrations should be carefully monitored in all severely poisoned patients.
Hypocalcemia from the ingestion of household fluoride-containing dental products (eg, dental fluoride rinses, sodium fluoride tablets) rarely occurs and is dose dependent. Hypocalcemia and significant morbidity and mortality occur with ingestion of industrial strength fluoride cleaners or fluoride releasers (eg, ammonium bifluoride used for cleaning white wall tires). Patients with these exposures should be treated with calcium in a manner similar to the hypocalcemia from other causes.