Hydrofluoric acid (HF) is a uniquely dangerous chemical that causes progressive tissue destruction via fluoride ion penetration and can produce life-threatening systemic toxicity (hypocalcemia, hypomagnesemia, hyperkalemia, cardiac arrest) even from seemingly minor dermal exposures. [1-3] Unlike other acid burns, HF penetrates deeply through intact skin, and the clinical appearance often dramatically underestimates the severity of injury. [4-5]
1. History
- Exposure details: Concentration of HF, duration of contact, route (dermal, inhalation, ingestion, ocular), TBSA involved, and time elapsed since exposure
- Pain characterization: Intense, deep, burning pain — classically pain out of proportion to exam findings. With dilute solutions (<20%), pain onset may be delayed hours after exposure [4][6]
- Timing: High-concentration (>50%) HF causes immediate pain and visible tissue destruction; low-concentration exposures may present with delayed symptoms (1–24 hours) [5]
- Decontamination history: Was irrigation performed at the scene? Duration? Was calcium gluconate gel applied?
- Product identification: Obtain Safety Data Sheet (SDS) — common sources include rust removers, wheel cleaners, glass etching compounds, semiconductor chemicals, aluminum brighteners [1][7]
- Associated symptoms: Numbness, paresthesias, dyspnea (if inhalation), nausea/vomiting (if ingestion), visual changes (if ocular)
2. Alarm Features
- TBSA >2.5% with any concentration, or >1% TBSA with >50% HF concentration — high risk for systemic toxicity [1][8]
- Death reported with as little as 2.5% BSA burn from concentrated HF [3]
- Pain unresponsive to topical calcium gluconate — suggests deep tissue penetration requiring escalation [9-10]
- Cardiac symptoms: Palpitations, syncope, chest pain — may herald lethal dysrhythmia [11-12]
- Systemic signs: Hypotension, altered mental status, tetany, Chvostek/Trousseau signs (hypocalcemia)
- Inhalation exposure: Dyspnea, wheezing, stridor — risk of chemical pneumonitis, pulmonary edema, ARDS [13-14]
- Ingestion: Oropharyngeal burns, hematemesis, abdominal pain — extremely high mortality [12]
- Delayed presentation (up to 16+ hours post-exposure): Systemic toxicity including cardiac arrest has occurred even after seemingly mild burns with initial appropriate treatment [15]
3. Medications
- Calcium gluconate — the cornerstone antidote:
- Topical: 2.5% calcium gluconate gel applied liberally and continuously [1][16]
- Subcutaneous: 10% calcium gluconate, 0.5 mL/cm² of burn area (max 0.5 mL per digit to avoid compartment syndrome) [6][16]
- Intra-arterial: 10 mL of 10% calcium gluconate in 40 mL NS infused over 4 hours via radial/brachial artery — for digital/hand burns refractory to topical/subcutaneous treatment [9-10]
- Regional IV (Bier block): 10 mL of 10% calcium gluconate + 30–40 mL NS with tourniquet for 20–25 min [16-17]
- IV systemic: 10% calcium gluconate bolus (20 mL) followed by continuous infusion for systemic toxicity [18]
- Magnesium sulfate IV — for concurrent hypomagnesemia [11][19]
- Nebulized calcium gluconate (2.5–5% solution) — for inhalation injuries [20-21]
- Avoid: Do not use calcium chloride subcutaneously (causes tissue necrosis). Calcium chloride may be used IV in cardiac arrest situations
- Caution: Standard treatment of hyperkalemia with glucose/insulin/bicarbonate may be ineffective in fluoride-induced hyperkalemia [22]
4. Diet
- Not directly applicable in the acute setting
- Ensure adequate calcium and magnesium intake during recovery
- Hydration is critical to promote renal fluoride excretion [23]
5. Review of Systems
- Cardiac: Palpitations, chest pain, syncope, presyncope
- Respiratory: Cough, dyspnea, wheezing, stridor (inhalation exposure) [13][24]
- GI: Nausea, vomiting, abdominal pain, hematemesis (ingestion)
- Neurologic: Paresthesias, muscle cramps, tetany, seizures (hypocalcemia)
- Musculoskeletal: Muscle weakness, cramping (electrolyte derangements); consider rhabdomyolysis [3]
- Ophthalmologic: Eye pain, tearing, visual changes (ocular splash)
6. Collateral History and Family History
- Collateral: Coworkers or bystanders can clarify the product, concentration, duration of exposure, and decontamination measures taken at the scene
- Occupational safety officer/employer: Obtain SDS for exact HF concentration
- Poison Control Center: Contact early (1-800-222-1222 in the US) for real-time management guidance [25]
- Family history is generally not relevant unless evaluating for baseline electrolyte disorders (e.g., hypoparathyroidism)
7. Risk Factors
- Occupational exposure accounts for ~80% of cases: [26]
- Semiconductor/electronics manufacturing (61% in one series) [26]
- Car/truck washing and detailing (aluminum brighteners, wheel cleaners) [7]
- Glass etching, metal cleaning, electroplating [3]
- Chemical/petroleum industry
- Household exposure: Rust removers, bathroom cleaners containing HF (concentrations typically 5–12%) [7][14][24]
- Lack of PPE: Inadequate gloves, no respiratory protection
- Delayed decontamination: Prompt irrigation within minutes is the single most important factor in limiting injury [27-28]
- Higher HF concentration and larger TBSA are the strongest predictors of systemic toxicity [8]
8. Differential Diagnosis
- Other chemical burns: Alkali burns (liquefaction necrosis), other acid burns (sulfuric, nitric) — distinguished by exposure history and SDS
- Thermal burn: Lacks the progressive, delayed tissue destruction pattern
- Contact dermatitis: Lacks the deep pain and progressive necrosis
- Compartment syndrome: May coexist with HF digital burns; consider if tense swelling and pain with passive stretch
- Frostbite: Can mimic appearance; history differentiates
- Necrotizing fasciitis: Progressive tissue destruction, but infectious etiology with systemic sepsis signs
- Phytophotodermatitis or caustic plant exposure: Milder, lacks systemic toxicity
9. Past Medical History
- Pre-existing hypocalcemia or hypoparathyroidism: Increases vulnerability to systemic toxicity
- Renal disease: Impairs fluoride excretion, prolongs systemic exposure [29]
- Cardiac disease: Lower threshold for dysrhythmia from electrolyte derangements
- Prior HF exposure: May indicate chronic occupational risk
- Medications: Calcium channel blockers, digoxin, or other QT-prolonging drugs may compound cardiac risk
10. Physical Exam
- Vital signs: Tachycardia or bradycardia, hypotension (systemic toxicity); tachypnea (inhalation)
- Skin: Initially may appear deceptively benign — erythema only, progressing to gray-white discoloration, blistering, and deep liquefactive necrosis over hours to days [4][6]
- Hands/digits: Most commonly affected site (74% upper limb in one series). Assess subungual involvement — may require nail removal [16]
- Neuromuscular: Chvostek sign, Trousseau sign (hypocalcemia), muscle fasciculations, tetany
- Respiratory: Wheezing, crackles, stridor if inhalation exposure [21]
- Vascular: Assess distal perfusion — HF can cause vasospasm [10]
- Pain assessment: Severity of pain is a more reliable indicator of injury depth than visual appearance
11. Lab Studies
- Stat electrolytes: Ionized calcium (most critical), magnesium, potassium, phosphorus — repeat serially (q1–2h in significant exposures) [1][19]
- BMP/CMP: Renal function, glucose
- Serum fluoride level: If available (not universally available; may take time to result)
- ABG/VBG: Assess for metabolic acidosis
- CBC: Baseline
- Coagulation studies: Fluoride can inhibit coagulation [23]
- CK/myoglobin: Consider rhabdomyolysis in significant exposures [3]
- Urinary fluoride: Can confirm exposure and guide duration of monitoring [21]
- Expected abnormalities: Hypocalcemia, hypomagnesemia, hyperkalemia (or hypokalemia in severe cases), metabolic acidosis [2][19][26][30]
12. Imaging
- Chest X-ray: For any inhalation exposure — assess for pulmonary edema, chemical pneumonitis [21]
- CT chest: If severe inhalation injury suspected — may show diffuse ground-glass opacities, consolidation, "white lung" pattern [13]
- Hand/digit X-rays: In digital burns — assess for bony erosion, which is a hallmark of deep HF penetration [6][31]
- Imaging is unnecessary for minor, isolated cutaneous burns that respond promptly to topical treatment
The following figure demonstrates the dramatic radiological findings of severe HF inhalation injury with chemical pneumonitis and ARDS, and the improvement after aggressive treatment including ECMO:
13. Special Tests
- Poison Control Center consultation — recommended for all HF exposures [25]
- TBSA estimation: Critical for risk stratification — TBSA >2.38% is the optimal cutoff predicting systemic toxicity (sensitivity 87.5%, specificity 95.9%) [8]
- Continuous cardiac monitoring: Mandatory for any significant exposure
- Point-of-care ionized calcium: Rapid bedside assessment; repeat frequently
- Wound fluorescence under Wood's lamp: Not standard but may help delineate extent in some cases
- Compartment pressure measurement: If digital/hand swelling raises concern for compartment syndrome
14. ECG
- Obtain immediately on all HF burn patients and place on continuous telemetry [1][6]
- Hypocalcemia findings: Prolonged QTc (specifically prolonged ST segment), may progress to torsades de pointes [33]
- Hyperkalemia findings: Peaked T waves, widened QRS, sine wave pattern — may herald refractory VF [22][34]
- Combined pattern: QRS widening + QT prolongation is a characteristic "electrocardiographic toxidrome" of HF poisoning [33]
- Ventricular dysrhythmias: VT, VF — may be recurrent and refractory to defibrillation; may persist even after electrolyte correction due to direct myocardial toxicity [12][35]
15. Assessment
Severity stratification based on HF concentration, TBSA, and route:
- Mild: Small area (<1% TBSA), low concentration (<20%), dermal only, pain controlled with topical calcium gluconate, normal electrolytes and ECG
- Moderate: Larger area or higher concentration, requiring subcutaneous/regional calcium, or any electrolyte abnormality
- Severe/Critical: TBSA >2.5%, concentration >50%, any ingestion or significant inhalation, systemic electrolyte derangements, dysrhythmia, hemodynamic instability [1][8]
Key clinical pearls:
- Burns may appear deceptively mild initially and progress over hours to days [4]
- Pain is the best early indicator of ongoing tissue injury — pain relief with calcium gluconate is both therapeutic and diagnostic
- Systemic toxicity can occur with delayed onset (up to 16+ hours) even after initial treatment [15]
- Direct myocardial toxicity from fluoride may cause dysrhythmias independent of electrolyte correction [12][35]
16. Treatment Plan
Immediate stabilization
- Remove all contaminated clothing and jewelry
- Copious water irrigation for a minimum of 15–30 minutes — begin immediately at the scene [1][25][27]
- If available, Hexafluorine or Diphoterine may be more effective than water alone for initial decontamination [28]
Topical therapy
- Apply 2.5% calcium gluconate gel continuously; reapply every 15–30 minutes until pain resolves [1][16]
- Alternative: DMSO 50% + calcium gluconate 10% in surgical jelly [16]
Escalation for refractory pain or larger burns
- Subcutaneous injection: 5–10% calcium gluconate, 0.5 mL/cm² (limit 0.5 mL per digit) [6][16]
- Regional IV (Bier block): 10 mL of 10% calcium gluconate + 30–40 mL NS, tourniquet 20–25 min [16-17]
- Intra-arterial infusion: 10 mL of 10% calcium gluconate in 40 mL NS over 4 hours — preferred for digital burns refractory to other modalities [9-10]
- Nail removal: May be necessary for subungual burns to allow direct treatment of the nail bed [9][16]
Systemic treatment (for electrolyte derangements or large burns):
- IV calcium gluconate: 20 mL of 10% bolus, then continuous infusion titrated to ionized calcium [18]
- IV magnesium sulfate: 2–4 g bolus, then infusion as needed [11][19]
- Potassium repletion or management as indicated by levels
- Cardiac arrest: Aggressive IV calcium, magnesium, defibrillation; consider hemodialysis for refractory dysrhythmias [36]
- CRRT/hemodialysis: For refractory electrolyte derangements or massive exposure to remove fluoride ions [18][23]
- ECMO: For refractory respiratory failure from inhalation injury [18]
Inhalation injury
- Nebulized 2.5–5% calcium gluconate solution [20-21]
- Supplemental oxygen, bronchodilators
- Monitor for delayed pulmonary edema/ARDS
Surgical
- Fasciotomy for digital compartment syndrome [31]
- Debridement of necrotic tissue — wait at least 7 days for demarcation before aggressive debridement [31]
- Wound excision may be necessary for hypocalcemia unresponsive to calcium therapy [1]
- Skin grafting or flap reconstruction for deep tissue loss [31][37]
17. Disposition
Admit (ICU) if
- TBSA >5% (any concentration) or >1% TBSA with >50% HF [1]
- TBSA >2.38% (evidence-based cutoff for systemic toxicity risk) [8]
- Any electrolyte abnormality (hypocalcemia, hypomagnesemia, hyperkalemia)
- ECG abnormalities or dysrhythmia
- Ingestion of HF (any amount)
- Significant inhalation exposure with respiratory symptoms
- Pain refractory to topical and subcutaneous calcium gluconate
- Hemodynamic instability
Transfer to burn center if
- Large TBSA, high-concentration exposure, or systemic toxicity [4]
- Burns requiring intra-arterial calcium or surgical intervention
Discharge criteria
- Small, isolated burn (<1% TBSA) with low-concentration HF
- Pain completely resolved with topical calcium gluconate
- Normal electrolytes (ionized calcium, magnesium, potassium) on serial checks (minimum 6–8 hours observation)
- Normal ECG and no dysrhythmia on monitoring
- Reliable patient with clear return precautions
18. Follow Up / Return Precautions
- Follow-up: Wound check within 24–48 hours — burns may progress despite initial treatment [4]
- Serial wound evaluation: Weekly for several weeks; tissue demarcation may take 7+ days [31]
- Return immediately for: Increasing pain, spreading discoloration, numbness/tingling, palpitations, muscle cramps, weakness, nausea/vomiting, shortness of breath
- Patient counseling:
- HF burns are deceptive — the wound may worsen before it improves
- Continue topical calcium gluconate gel application at home if prescribed
- Avoid re-exposure; ensure proper PPE education for occupational cases
- Expected recovery: Minor burns with prompt treatment typically heal well; deep burns may require weeks to months and surgical reconstruction [31][37]
- Occupational health referral: For workplace exposures — ensure SDS availability, PPE compliance, and employer notification [7]
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