Hydrofluoric Acid

Hydrofluoric acid is a relatively weak acid (p Ka = 3.8) used in industry for glass etching, metal cleaning, and petroleum processing. It may also be found in household products such as chrome wheel cleaner and rust remover. Despite being a relatively weak acid, hydrofluoric acid has great potential for causing morbidity and death. The major mechanism of injury with hydrofluoric acid is not coagulation necrosis; rather, the free fluoride ion complexes with body calcium and magnesium, resulting in cellular death. Most injuries are to the upper extremities. Patients often present with benign-appearing wounds but complain of a tremendous amount of pain. These wounds often have a slight white discoloration but may become black and necrotic as cellular damage results. Severe injuries may result in hypocalcemia, hypomagnesemia, hyperkalemia, acidosis, and ventricular dysrhythmias. Ventricular fibrillation and death have been reported with dermal exposure of between 2.5 and 22 percent of body surface area.

Treatment of minor hydrofluoric acid injuries consists of first thoroughly irrigating the affected area with water and then placing the area in a paste of calcium gluconate or benzalkonium chloride solution. Paste can be made with surgical lubrication and calcium gluconate powder (2.5 percent wt/vol) or alternately with a commercial preparation of benzalkonium chloride (Zephiran) is available. The affected area is soaked in the gel, with pain relief being used as end point for therapy. Other effective treatments include intradermal injections of 5% calcium gluconate or magnesium sulfate around the affected area (not to exceed 0.5 mL/cm 2). For distal upper extremity injuries that do not respond to the aforementioned treatments, intraarterial infusion of calcium gluconate has been used. It is recommended that 10 mL of 10% calcium gluconate diluted in 40 mL of normal saline be infused over 4 h or until pain resolves. The use of calcium chloride should be avoided for fear of skin necrosis if extravasation occurs. The use of calcium gluconate with a Bier block has been advocated for treating serious hydrofluoric injuries. 21

Oral ingestion of hydrofluoric acid has a high mortality rate. NG tube placement and gastric lavage with normal saline are recommended. Oral magnesium or calcium should be given in hydrofluoric ingestions on a milliequivalent-for-milliequivalent basis. If the amount of hydrofluoric acid ingested is not known, then 300 mL of magnesium citrate or calcium salts should be given. In serious exposures of any type, attention should be focused on hemodynamic monitoring for dysrhythmias. Serum calcium and magnesium levels should also be followed closely. Intravenous supplementation with large amounts of calcium and magnesium may be required.

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