Episode 53- An expert talks: Hydrofluoric acid exposures
Episode Summary:
This week we discuss hydrofluoric acid exposures with Dr. KC Lee, a clinical pharmacist with training in toxicology/ emergency medicine
Show Notes:
Key Points:
“An expert talks: Hydrofluoric acid exposures”:
– Hydrofluoric acid (HF) is a dermal/ respiratory irritant and a weak acid (dissociation constant is ~1,000 times less than HCl). Toxicity is caused by the the highly reactive F- ion
– HF penetrates tissues deeply, where the F- ion is released and destroys cells. Unlike other acids which are rapidly neutralized, HF may continue its destruction for days if left untreated
– F- precipitates with divalent cations- causing hypocalcemia and hypomagnesemia, as well as hyperkalemia due to extracellular shifting. Caution using succinylcholine for rapid sequence intubation in these patients given this risk of hyperkalemia
– One of the most toxic effects of the F- ion is its reaction with calcium (Ca). The basis for treatment of exposures is Ca, given by numerous different methods/routes to precipitate the F- ion:
– Systemic: use your institution’s electrolyte replacement protocol to aggressively replace Ca (consider also replacing magnesium)
– Ophthalmic: irrigate the eyes thoroughly with normal saline (NS) or lactated ringer’s (useful as it contains Ca). This is one scenario where it is not recommended to directly apply Ca salts, as they can cause corrosive injury to the eye
– Inhalation: use nebulized calcium gluconate (CaGluc) at a 2.5-5% concentration. A 2.5% solution can be made by mixing 1 part 10% CaGluc solution : 3 parts sterile water (SW)/NS. For example, take 1 mL of CaGluc + 3 mL of NS/SW and place this into the neb chamber
– Subcutaneous: although rarely used, consider using a 5-10 % CaGluc solution and injecting with a 27-30 gauge needle around the affected area. Use a maximum of 0.5 mL per digit or 1 mL/ cm^2
– Intra-arterial: may be useful for burns involving several digits or subungual areas, or if topical therapy fails. Dilute 10 mL of 10% CaGluc (avoid calcium chloride) with 50 mL D5W and infuse over 4 hours through brachial or radial artery catheter
– Topical: the most common route of administration. If hand or fingers are affected, place the Ca solutions in a surgical glove over the hand with continuous massaging and frequent gel application. If you do not have the commercially-available gel (Calgonate), compound a 2.5% gel by mixing 1 g 10% CaGluc + 40 mL Surgilube/KY Jelly. Another method is to crush 20 calcium carbonate (TUMS) tablets (200 mg elemental Ca per tab) and adding to 5 oz of Surgilube/KY Jelly
– With the topical route, local anesthetics should not be used since they mask pain, which is an important sign of treatment adequacy