One Pill Can Kill: Hydrofluoric Acid

The Case:

You are called to a residence for a 5-year-old boy who spilled “poison” on himself.

On arrival, a man greets you at the front door and explains that he is an amateur glass etcher; he carves intricate patterns on glass panes. As you look around, you see evidence of his craft: nearly every window has a beautiful pattern etched into it, and every possible surface has a glass statute with designs. He leads you to the garage, where you see a bunch of glass Chess set pieces in various stages of being etched. You’re fascinated by the art of it all, but your curiosity quickly evaporates as you see an ill child sitting cross-legged in a work sink with running water.

“He grabbed a dish off the table, and acid spilled all over him,” says the man.

While your partner grabs vitals and applies oxygen to the screaming child (airway: check!) you inspect the “acid” bottle. It reads:

HYDROFLUORIC ACID 40%

The Poison of Glass-Etchers, Farmers, Train Yards

Used in glass etching and phosphate-based pesticides and insecticides, and transported by rail, hydrogen fluoride (HF) isn’t something we think about every day. But the extreme toxicity that can be caused by just a small exposure makes it of grave concern. Further, unlike many poisons, patients can survive if treated appropriately.

When I say extreme toxicity, I’m serious. Hydrofluoric acid is remarkably deadly. Just dipping your toes into HF can lead to life-threatening hypocalcemia.  Fluoride is an aggressive ion capable of penetrating tissues in a destructive manner. Once in the bloodstream, fluoride binds to intracellular calcium and magnesium and causes excess potassium.

Hypocalcemia can be identified by tetany, where the muscles of the hands tighten. Patients often feel perioral numbness or tingling, and you can elicit Chvostek’s sign by tapping on the facial muscles along the TMJ in front of the ear: you’ll see the muscles around the eyes, mouth, and nose twitch. Trousseau’s sign refers to carpopedal spasm and wrist contracture induced by the inflation of a blood pressure cuff on the arm.

Hypocalcemia causes cardiogenic shock through decreased inotropy, weakening the muscles of the heart. It can also cause arrhythmia. Hyperkalemia also causes arrhythmias, with a typical pattern of bradycardia, widened QRS, and eventual pre-terminal sine wave, before the onset of ventricular fibrillation or PEA.

The skin is often severely burned and eyes can often be extremely sensitive. You can imagine all of this is remarkably painful.

HF gas is colorless with a strong, irritating odor. HF fluid is indistinguishable from water.  Presentations can be slightly delayed.

Treatment of Hydrofluoric Acid Toxicity: An EMS Prerogative

Secondary contamination is a risk to professional rescuers, contaminated clothing can be a direct or off-gassing risk to first responders. Only trained personnel should work in hot zones. Patients should be decontaminated with copious water irrigation and clothes should be discarded to prevent off-gassing.

Medical treatment involves aggressive intravenous, nebulized and/or topical calcium gluconate. Topical calcium is a slurry or gel; mix 10% calcium gluconate with lubricating jelly to make a 2.5% topical treatment. Most EMS agencies that have HF protocols carry calcium gluconate. Some EMS agencies that don’t have an HF protocol may still have calcium for other conditions like renal failure. Bronchodilators may help with wheezing and nebulized epi may help with stridor when inhalation has occurred, but both can irritate the myocardium (which is sensitive to beta-adrenergic due to the electrolyte disturbances. Balance these risks based on patient presentation. And please, don’t forget to treat pain! HF causes severe burns and eye irritation.

If you work in an area that freight trains pass through, you ought to have an HF protocol and carry the antidote, intravenous calcium (chloride or gluconate). Many EMS agencies have offline medical direction for such care. They tend to look like this:

• Indication: exposure to HF liquid or vapor AND exhibit signs of HF toxicity. 
• Conditions: none (no age limits, vital sign parameters, etc) 
• Contraindications: allergy or sensitivity to calcium gluconate/chloride 
• Treatment: Inhalation: nebulized calcium. Skin exposure: topical gel and IV calcium.

If you carry calcium gluconate for other indications, such as hyperkalemia from renal failure, consider contacting online medical directions.

Back to the Case:

The child is already stripped of clothing and soaking wet from the water irrigation, thanks to a very smart parent! You load the child into the ambulance and establish an IV, pushing morphine while your partner mixes a 2.5% calcium gluconate slurry. You apply it liberally to the burned skin on his arms, face and chest. En route, you start to notice ectopy on the monitor; you call online medical control, who orders 5mL (500mg) of Calcium chloride 10% to be administered intravenously. Remarkably, you see the ECG return to sinus rhythm right before your eyes! However, as you pull into the hospital, you notice ectopy return; the triage nurse immediately directs you to a resuscitation bay, where a physician is waiting.

A word on Fluoride:

Fluoride is everywhere; it’s naturally in the earth as salt, in groundwater, and in vegetation.

Toothpaste contains fluoride; either sodium fluoride, sodium monofluorophosphate, or stannous fluoride. A few mouthfuls of toothpaste aren’t harmful, but in large amounts, toothpaste can cause poisoning. Upset stomach, nausea, vomiting, and diarrhea and the most common symptoms; altered consciousness and weakness can be seen in more serious cases. Symptoms usually begin within minutes.

Each year, poison control centers get dozens of calls for fluoride poisoning after toothpaste ingestion. The largest review of this was published in 1991 and reviewed an entire year (1986) at a poison control center in Denver, Colorado. That year, 87 calls for fluoride poisoning in children were made; 26 had symptoms, and six had calcium levels drawn which were all normal (1). There was one death; a 13-month-old who ingested insecticide that contained sodium fluoride. An infamous case from 1979 demonstrates fatal toxicity: a 3-year-old boy died after fluoride gel placed on his teeth by a dental hygienist was ingested. He rinsed his mouth with water and swallowed it, rather than spitting it out (2).

Citation: 

1. Augenstein WL, Spoerke DG, Kulig KW, Hall AH, Hall PK, Riggs BS, el Saadi M, Rumack BH. Fluoride ingestion in children: a review of 87 cases. Pediatrics. 1991 Nov;88(5):907-12. PMID: 1945630. 

2. https://www.nytimes.com/1979/01/20/archives/750000-given-in-childs-death-in-fluoride-case-boy-3-was-in-city.html 

Blair Bigham worked for a decade as a flight paramedic on four continents, a job he misses every day. He is now an ER and ICU physician at the University of Toronto and a public health researcher at the Dalla Lana School of Public Health. @BlairBigham blairbigham.com