DESCRIPTION

Hydrogen fluoride (HF), ammonium fluoride (NH₄F), and ammonium bifluoride (NH₄HF₂) are chemicals used in household and industrial products.

FORMS AND USES

Hydrogen Fluoride

• HF is available as a concentrated solution (for glass etching) or in more dilute household products (rust remover and automotive cleaning products).
• Concentration ranges from 6% or 8% to 90%.

Ammonium Bifluoride and Ammonium Fluoride

• Ammonium bifluoride is found in products used to clean wheels, in dairy equipment, and in beer-processing equipment.
• It is used in the manufacture of magnesium and its alloys, in the porcelain and glass industries, and in aluminum production.
• Effects of ammonium bifluoride or fluoride ingestion are similar to those of HF ingestion.

TOXIC DOSE

• Ingestion of more than 30 ml of low-concentration rust remover by an adult has been fatal.
• Dermal exposure to HF at more than 50% concentration over 1% body surface area may cause rapid deterioration and death.

PATHOPHYSIOLOGY

• Fluoride-containing compounds cause toxicity primarily by the binding and precipitation of calcium ions.
• This produces local tissue injury as well as systemic hypocalcemia.
• The direct skin injury is not as rapid and severe as caustics such as lye, unless the concentration is greater than 50%.

EPIDEMIOLOGY

• Poisoning is uncommon.
• Toxic effects following exposure are typically mild.
• Death occurs following exposure to high concentrations, large dermal exposure, or ingestion.

CAUSES

• Poisoning usually occurs by accidental skin exposure or ingestion.
• The possibility of child neglect should be considered in patients under 1 year of age; suicide attempt in patients over 6 years of age.

RISK FACTORS

Children have a larger surface area-to-volume ratio, which may increase the risk of systemic symptoms from dermal exposure.

Section Outline:

• DESCRIPTION
• FORMS AND USES
  • Hydrogen Fluoride
  • Ammonium Bifluoride and Ammonium Fluoride
• TOXIC DOSE
• PATHOPHYSIOLOGY
• EPIDEMIOLOGY
• CAUSES
• RISK FACTORS

DIFFERENTIAL DIAGNOSIS

Toxic causes of skin burns include acid or alkali burns and phenol.

SIGNS AND SYMPTOMS

• Skin exposure is initially asymptomatic (unless a concentrated solution is involved), followed by severe unremitting burning pain hours later.
• Following ingestion, sudden cardiac dysrhythmia and death may occur within the first few hours after ingestion.

Vital Signs

Pain may cause tachycardia and hypertension.

HEENT

• Unless a high-concentration product has been ingested, patients usually do not have clinically significant oral burns.
• Eye exposure may cause severe corneal injury.

Dermatologic

• Over time, erythema and burns may develop; time to onset is inversely related to the concentration of product.
• Exposure to HF at 6% to 8% concentration may not produce injury for several hours.
• Exposure to HF at more than 50% concentration produces injury quickly.

Cardiovascular

Ventricular dysrhythmia may develop in severe dermal exposure or following ingestion.

Pulmonary

Inhalation may cause bronchospasm, hypoxia, and pulmonary edema; upper airway burns may develop in severe exposure.

Gastrointestinal

• Ingestion of HF or ammonium bifluoride at low concentrations (<10%-20%) causes minor gastrointestinal symptoms.
• Ingestion of HF at high concentration may result in esophageal or gastric burns.

Fluids and Electrolytes

Hypocalcemia and hypomagnesemia can result from either dermal exposure or ingestion; rapidity of onset appears to be directly related to amount and concentration.

Neurologic

Tetany can develop from hypocalcemia.

PROCEDURES AND LABORATORY TESTS

Essential Tests

No tests may be needed for small dermal burns from HF at 6% to 8% concentration.

Recommended Tests

• Skin exposure. Serum electrolytes, BUN, creatinine, calcium, and magnesium levels are needed only following exposure to HF or ammonium fluoride at more than 10% concentration that involves at least 1% of body surface area, or 6% to 8% concentration that involves more than 5% body surface area.
• Ingestion
  • Serum electrolytes, BUN, creatinine, calcium and magnesium levels should be measured if the patient has ingested a concentration of more than 10% or has taken more than a sip (approximately 2-5 ml) of solution at less than 10% concentration.
  • Serum calcium and magnesium should be repeated hourly; decreasing or mildly decreased calcium levels should be treated immediately because the patient may deteriorate abruptly.
  • ECG should be obtained at arrival and every 15 to 30 minutes for at least 2 hours for significant exposures; QT interval prolongation is a sign of cardiac toxicity.

Section Outline:

• DIFFERENTIAL DIAGNOSIS
• SIGNS AND SYMPTOMS
  • Vital Signs
  • HEENT
  • Dermatologic
  • Cardiovascular
  • Pulmonary
  • Gastrointestinal
  • Fluids and Electrolytes
  • Neurologic
• PROCEDURES AND LABORATORY TESTS
  • Essential Tests
  • Recommended Tests

• Treatment should focus on decontamination, close monitoring, and prompt treatment of hypocalcemia.
• Dose and time of exposure should be determined for substances involved.

DIRECTING PATIENT COURSE

The health-care provider should call the poison control center when:

• Hypocalcemia, dysrhythmia, significant burns, or other severe effects are present.
• The patient has ingested a concentration of more than 10% or has taken more than a sip (approximately 2-5 ml) of solution at less than 10% concentration.
• Toxic effects not consistent with hydrogen fluoride poisoning are present.
• Coingestant, drug interaction, or underlying disease presents unusual problems.

The patient should be referred to a health-care facility when:

• Attempted suicide or homicide is possible.
• Patient or caregiver seems unreliable.
• History of ingestion of any fluoride-containing product is obtained.
• Coingestant, drug interaction, or underlying disease presents unusual problems.

Admission Considerations

Inpatient treatment in the ICU is warranted when:

• Patient with skin exposure has hypocalcemia or burns of large surface area.
• Patient with ingestion shows any clinical effect during several hours of observation.
• Large or complicated burns (e.g., of the face or perineum) are present, which should be evaluated at a burn facility.

DECONTAMINATION

Out of Hospital

• Skin should be washed copiously with water for 20 to 30 minutes.
• Following ingestion, 30 cc of a magnesium antacid (e.g., milk of magnesia) or calcium carbonate (e.g., Tums) should be administered.

In Hospital

• Skin should be washed copiously with water for 20 to 30 minutes.
• Following ingestion, stomach contents should be aspirated if patient arrives within 30 minutes.
• Following ingestion, 30 cc of a magnesium antacid (e.g., milk of magnesia) or calcium carbonate (e.g., Tums) should be administered.

ANTIDOTES

Skin Burns

• Small burns (e.g., on a finger) can be treated with a topical paste or subcutaneous injection of calcium gluconate.
• Calcium chloride is caustic and should be used only intravenously, not topically or by infiltration.

Calcium Gluconate Paste

• Indication. Pain after any HF exposure indicates use.
• Contraindications. There are none.
• Method of administration
  • Paste should be applied liberally to the affected area (for hand injury, placement of paste in latex glove allows convenient application).
  • To make the paste, 3.5 g of calcium gluconate powder is mixed with 5 ounces of a water-soluble lubricant (e.g., K-Y jelly) or ten 10-grain tablets (6.5 g) of calcium carbonate (e.g., Os-Cal) are crushed in a minimum of 20 ml of water-soluble lubricant.

Calcium Gluconate 10% Solution for Injection

• Indication. Pain not responding to topical calcium indicates use.
• Method of administration
  • Local infiltration of digit involved or 1 ml for each 2 cm² of burned area using a 30-gauge needle.
  • Intravenous infusion using a Bier block technique; intraarterial infusion has been used for difficult cases; consultation with a poison center or medical toxicologist is advised.
• Adverse reactions
  • Infiltration of large amounts of fluid may result in local tissue injury.
  • Calcium chloride should not be used for infiltration.

Ingestion

Calcium Chloride 10% Solution

• Indications
  • Indications are systemic hypocalcemia, prolonged QTc, or other evidence of hypocalcemia (e.g., paresthesias or hyperactive reflexes).
  • Prophylactic use should be considered for high-risk situations (large surface area exposure, large or suicidal ingestion).
• Method of administration
  • The dose is 5 to 10 cc infused intravenously over 10 minutes.
  • The pediatric dose is 10 to 25 mg/kg, up to one ampule per dose.
  • Dose is repeated based on narrowing of QTc interval to normal (<0.47 seconds in adults).
• Adverse reactions
  • Calcium chloride is caustic to tissue and should not be given by local injection or topically.
  • Hypotension and dysrhythmias may occur with rapid injection.

Magnesium Sulfate

• Indications
  • Indication is systemic hypomagnesemia.
  • Prophylactic use should be considered for high-risk situations (e.g., large surface area, large or suicidal ingestion).
• Method of administration
  • The dose is 2 to 4 g infused intravenously over 10 minutes.
  • Pediatric dose is 25 mg/kg, up to 2 g.
  • Dose is repeated hourly as needed.
• Adverse reactions
  • Rapid infusion may cause vasodilatation and hypotension.
  • Hypermagnesemia may cause CNS and respiratory depression.

ADJUNCTIVE TREATMENT

Patients with digital burns may need to have fingernails removed to allow treatment of the nailbed.

Section Outline:

• DIRECTING PATIENT COURSE
  • Admission Considerations
• DECONTAMINATION
  • Out of Hospital
  • In Hospital
• ANTIDOTES
  • Skin Burns
  • Ingestion
• ADJUNCTIVE TREATMENT

PATIENT MONITORING

Patients with ingestion of any amount, high-concentration skin exposure, or large surface area skin exposure should have close cardiac monitoring because rapid cardiovascular collapse may develop.

EXPECTED COURSE AND PROGNOSIS

• Patients with low-concentration skin burns generally respond well to topical calcium, and symptoms resolve completely over several days.
• Patients with high-concentration burns usually develop immediate symptoms and may have extensive tissue injury despite rapid treatment.
• Patients with hypocalcemia may have rapid cardiovascular collapse and not respond to even high-dose calcium and magnesium.
• Local burns may require skin grafting.

DISCHARGE CRITERIA/INSTRUCTIONS

• From the emergency department. Patients with small dermal burns that improve with treatment may be discharged following 6 hours of observation and provision of follow-up for burn care.
• From the hospital. Patients may be discharged following recovery of normal cardiac function, with adequate pain control and good burn care follow-up.

Section Outline:

• PATIENT MONITORING
• EXPECTED COURSE AND PROGNOSIS
• DISCHARGE CRITERIA/INSTRUCTIONS

DIAGNOSIS

• Ingestion may not produce the typical signs of corrosive ingestion.
• Sudden cardiac arrest may occur following ingestion of more than an ounce.

TREATMENT

• Even mildly depressed calcium or prolongation of the QTc interval may portend rapid deterioration.
• Very high doses of calcium and magnesium may be required.

Section Outline:

• DIAGNOSIS
• TREATMENT

Toxic effect of corrosive aromatics, acids, and caustic alkalis.

See Also: SECTION III, Calcium Gluconate and Chloride, and Magnesium Sulfate chapters.

RECOMMENDED READING

Caravati EM. Acute hydrofluoric acid exposure. Am J Emerg Med 1988;6:143-250.

Stremski ES, Grande GA, Ling LJ. Survival following hydrofluoric acid ingestion. Ann Emerg Med 1992;21:1396-1399.

Authors: Lada Kokan and Kennon Heard

Reviewer: Katherine M. Hurlbut