Chemical Burns

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• Alkali Burns (Liquefaction Necrosis): Alkali agents aggressively interact with lipids in epithelial membranes (saponification), resulting in liquefaction necrosis. This mechanism breaks down tissue barriers, allowing the chemical to penetrate deeply and rapidly into the stroma or deeper tissue layers, causing severe, progressive damage. For example, anhydrous ammonia can penetrate the anterior chamber of the eye in less than 1 minute.
• Hydrofluoric Acid (HF) Systemic Toxicity: HF acts uniquely as a penetrating systemic toxin rather than just a surface corrosive. The fluoride ion rapidly penetrates tissues and avidly binds to endogenous tissue cations (calcium and magnesium), causing profound, life-threatening hypocalcemia and hypomagnesemia. The resulting cellular destruction also releases intracellular potassium, leading to systemic hyperkalemia and lethal cardiac dysrhythmias.
• Caustic Ingestions: Ingestion of caustic substances causes direct mucosal burns, leading to rapid and progressive edema of the oropharynx, upper airway, and gastrointestinal tract.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Decontamination: Ensure provider safety with appropriate PPE (gowns, gloves, eye protection). Immediately disrobe the patient, remove all jewelry and contact lenses, and brush off any dry powdered chemicals before wetting.
• Copious Irrigation: The universal primary treatment is continuous, high-volume irrigation with water or normal saline at low pressures.
• Ocular Management: For eye exposures, continuously irrigate the affected eye(s) until the ocular pH reaches a physiologic level of approximately 7.4. Treat significant ocular burns with a long-acting cycloplegic and mydriatic agent.
• Targeted Antidotal Pharmacotherapy:
• Hydrofluoric Acid (HF): Apply 2.5% topical calcium gluconate gel to the burn and secure it with an occlusive cover (e.g., a latex glove). If unavailable, mix 3.5 g of calcium gluconate powder in 150 mL of water-soluble lubricant. For severe cases, consider 10% calcium gluconate via intradermal or intra-arterial injection.
• Oxalic Acid: Monitor electrolytes closely; IV calcium may be required to counteract binding.
• Airway Control: Maintain a remarkably low threshold for definitive airway management. Early endotracheal intubation is indicated for any signs of airway compromise, such as dysphonia, stridor, hoarseness, throat pain, or drooling.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• Critical "Can't-Miss" Mimics:
• Thermal Burns: May present identically or concomitantly, especially if a chemical exploded or ignited.
• Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN): Can mimic diffuse chemical desquamation.
• Neuropathy or Shingles: Must be considered if the patient presents with severe, burning pain out of proportion to physical skin findings, which is a classic early presentation of HF acid exposure.
• Prioritized Diagnostic Workup:
• Agent Identification: Ideally, obtain the Material Safety Data Sheet (MSDS) or a clear photo of the chemical container to confirm pH and concentration.
• Severe Exposure Lab Panel: For burns >5-10% TBSA, suspected ingestion, or HF exposure, order: comprehensive metabolic profile (specifically K+, Mg2+, and ionized Ca2+), renal function, CPK, CBC, coagulation profile, and a blood gas with lactate.
• Imaging: Obtain a chest radiograph if inhalation is suspected, and abdominal/chest films to assess for free air (perforation) in caustic ingestions.
• Endoscopy: The gold standard for evaluating intentional caustic ingestions, performed 12 to 24 hours post-ingestion after the airway is fully secured.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• The Clinical Exam (Pattern Recognition):
• Dribble Burns: Look for downward-flowing streaks of chemical burns on the face, neck, or anterior chest, which are pathognomonic for caustic ingestion or assault.
• Oropharyngeal Assessment: Explicitly look for mucosal burns, edema, or soot in the oropharynx.
• Non-Accidental Trauma: Always consider intentional self-injury or abuse in chemical burns.
• Ocular Assessment: Use litmus paper to check ocular pH. Perform a slit-lamp examination with fluorescein staining to assess for epithelial defects, corneal haze, or perilimbal ischemia.
• Electrocardiogram (ECG): Mandatory in systemic HF or oxalic acid exposures. Explicitly look for a prolonged QTc interval (indicative of profound hypocalcemia) or widened QRS/peaked T waves (indicative of hyperkalemia).

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• American Burn Association (ABA) Burn Center Transfer Criteria (2022): You must consult and transfer patients to a specialized Burn Center if they meet any of the following definitive criteria:
• Partial thickness burns > 10% of the total body surface area.
• Full thickness burns of any size.
• Any deep partial or full thickness burns involving the face, hands, feet, genitalia, perineum, or over any joints.
• Patients with significant pre-existing medical comorbidities or concomitant traumatic injuries.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Pitfall (Delayed Airway Management): Waiting for stridor or severe hypoxia to develop before intubating a caustic ingestion patient. Edema and secretions increase rapidly, making delayed intubation difficult or impossible.
• Pitfall (Blind Dilution): Administering oral diluents (like water or milk) to a patient with a caustic ingestion who is exhibiting difficulty swallowing, drooling, or airway compromise.
• Pitfall (Corticosteroid Administration): Administering systemic corticosteroids to prevent esophageal stricture formation after a caustic ingestion; evidence for their benefit is lacking, and serious side effects can occur.
• CRITICAL ACTION: You must continuously irrigate ocular chemical injuries until a physiologic pH of ~7.4 is confirmed in the conjunctival fornix. Do not postpone irrigation to wait for agent identification.
• CRITICAL ACTION: Recognize the extreme danger of Hydrofluoric acid. You must aggressively monitor and replete calcium and magnesium; failure to do so will result in lethal ventricular dysrhythmias.

7. MCQ MASTERCLASS (Written Exam Tips)

• Buzzwords: "Rust remover," "glass etching," or "severe pain out of proportion to visual skin injury" $\rightarrow$ Hydrofluoric acid (HF) burn. The answer is always topical calcium gluconate gel.
• Buzzwords: "Wet cement in work boot" $\rightarrow$ Unnoticed alkali burn causing deep tissue necrosis over hours.
• Common Distractor: A question stem will describe a patient with a caustic liquid splashed in their eye and ask for the "first" or "best" step. Distractors will include "identify the agent," "check visual acuity," or "perform a slit-lamp exam." The correct answer is always immediate, copious irrigation with water or normal saline.
• Common Distractor: A patient intentionally swallows an unknown acid and complains of throat pain and drooling. The options will include "administer oral neutralizing agent," "administer activated charcoal," or "early endotracheal intubation." The correct answer is endotracheal intubation; neutralizing agents cause exothermic reactions that worsen the burn, and charcoal is contraindicated as it obscures endoscopy.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• High-Stress Articulation: "This patient presents with a chemical exposure carrying a high risk of deep tissue necrosis and systemic toxicity. My immediate priorities are ensuring provider PPE, completely disrobing the patient, brushing off any dry powders, and initiating copious, low-pressure water irrigation to the affected areas before continuing the primary survey."
• Mandatory Physical Exam Maneuvers: "I will evaluate the airway meticulously for hoarseness, stridor, or drooling. I will then perform a thorough ocular exam, explicitly checking the pH of the eyes to guide continuous irrigation until we achieve a pH of 7.4, followed by a slit-lamp exam with fluorescein."
• Communication Pearl (HF Acid Suspected): "Nurse, please place the patient on a continuous cardiac monitor and obtain a stat 12-lead ECG and basic metabolic panel. I am specifically looking for prolonged QTc or arrhythmias indicating hypocalcemia or hyperkalemia from hydrofluoric acid toxicity. Please prepare 2.5% topical calcium gluconate gel immediately."