Chemical Burn (Acid)

1. Executive Overview: Understanding Acid Chemical Burns

An acid chemical burn is a form of tissue injury occurring when skin or mucosal surfaces come into contact with an acidic substance, typically with a pH less than 2. Unlike thermal burns, which are caused by heat, chemical burns are the result of a molecular reaction where the acid induces protein denaturation and tissue necrosis.

In the field of Plastic and Reconstructive Surgery, these injuries are classified under ICD-10 code T54.91XA (Toxic effect of unspecified corrosive substance, accidental, initial encounter). These injuries are time-sensitive medical emergencies. The depth and severity of the burn depend on the concentration of the acid, the duration of contact, and the volume of the agent involved. Because acids cause "coagulation necrosis," they often create a protective eschar that can limit the depth of the burn; however, high-concentration acids can still cause full-thickness destruction of the dermis, subcutaneous fat, and underlying structures.

2. Pathophysiology, Etiology, and Risk Factors

The Mechanism of Injury

When an acid contacts the skin, it initiates a process known as coagulation necrosis. The hydrogen ions in the acid cause the denaturation and precipitation of proteins. This forms a coagulum—a hard, leathery eschar. This eschar serves as a biological barrier that, theoretically, prevents the acid from penetrating deeper into the tissue.

Etiology

Common acidic agents encountered in clinical practice include:
* Hydrofluoric Acid (HF): Extremely dangerous; causes deep tissue destruction and systemic hypocalcemia.
* Sulfuric Acid: Found in industrial drain cleaners and car batteries; causes severe exothermic reactions.
* Hydrochloric Acid: Used in pool maintenance and industrial cleaning.
* Nitric Acid: Causes yellow-staining of the skin (xanthoproteic reaction).

Risk Factors

3. Signs, Symptoms, and Clinical Presentation

Clinical presentation varies based on the chemical agent. Patients may present with a range of symptoms from mild erythema to charred, necrotic tissue.

• Pain: Often intense and immediate, though some acids (like HF) can cause delayed or deceptively mild pain while causing deep damage.
• Skin Discoloration: Acids often leave distinct marks (e.g., yellow for nitric acid, black/brown for sulfuric acid).
• Blistering: Bullae formation indicates a second-degree (partial-thickness) injury.
• Systemic Symptoms: If the burn covers a large surface area, patients may experience tachycardia, hypotension, or metabolic acidosis.

4. Standard Diagnostic Evaluation & Workup

The evaluation of a chemical burn requires a structured approach to ensure no systemic toxicity is missed.

Primary Assessment

1. Airway, Breathing, Circulation (ABCs): Stabilize the patient first. If the chemical was inhaled, early intubation may be required.
2. Decontamination: The most critical diagnostic and therapeutic step. Remove all clothing and irrigate with copious amounts of water or saline.

Diagnostic Workup

• Laboratory Assays:
  • Complete Blood Count (CBC): To assess for hemoconcentration.
  • Electrolytes: Specifically monitoring for hypocalcemia (if HF exposure is suspected) and metabolic acidosis.
  • Renal Function (BUN/Creatinine): To rule out acute kidney injury from systemic absorption.
• Imaging:
  • Chest X-ray: If inhalation is suspected.
  • CT Scans: Reserved for deep tissue burns where involvement of underlying bone or neurovascular structures is suspected.
• Biopsy: Rarely needed in the acute phase but may be utilized in chronic, non-healing wounds to rule out Marjolin’s ulcer (squamous cell carcinoma) in old burn scars.

5. Therapeutic Interventions

Immediate First Aid

The "Gold Standard" for chemical burns is immediate, copious irrigation. Irrigation should continue for at least 30–60 minutes, or until the patient reports the cessation of pain.

Pharmacological Management

• Analgesia: IV opioids are standard for pain management.
• Tetanus Prophylaxis: Mandatory for all full-thickness burns.
• Topical Agents: Silver sulfadiazine or mafenide acetate for infection prophylaxis.

Surgical Interventions

Plastic surgery consultation is required for any burn that is not superficial.
1. Debridement: Removal of necrotic eschar to prevent infection and promote healing.
2. Skin Grafting: For full-thickness injuries, split-thickness skin grafts (STSG) are the gold standard for reconstruction.
3. Flap Reconstruction: If the burn involves muscle, tendon, or bone, local or free tissue transfer flaps may be necessary to provide vascularized coverage.

Lifestyle and Rehabilitation

• Pressure Garments: Used to prevent hypertrophic scarring in the months following the burn.
• Physical Therapy: Crucial for burns over joints to prevent contractures and loss of range of motion.

6. Frequently Asked Questions (FAQ)

1. How long should I wash a chemical burn?
You should irrigate the area with tepid water for at least 30 to 60 minutes. Do not use chemical neutralizers, as they can cause an exothermic reaction that worsens the burn.

2. Is a chemical burn considered an emergency?
Yes. Any chemical burn that is not clearly superficial (redness only) should be evaluated in an emergency department to determine the depth and potential for systemic toxicity.

3. What is the difference between a thermal burn and an acid burn?
Thermal burns are caused by heat transfer. Acid burns are caused by chemical reactions that denature proteins and destroy tissue at a cellular level.

4. Will I have a scar after a chemical burn?
The potential for scarring depends on the depth of the burn. Superficial burns usually heal without scarring, while full-thickness burns typically require grafting and may leave permanent scars.

5. Should I apply toothpaste or butter to a chemical burn?
Never. These substances trap heat and chemicals against the skin, increasing the risk of infection and deepening the burn. Use only clean, running water.

6. What is the role of a plastic surgeon in treating acid burns?
Plastic surgeons specialize in complex wound closure, skin grafting, and reconstructive techniques to minimize functional impairment and cosmetic deformity.

7. Can an acid burn affect my internal organs?
Yes. If the acid is highly concentrated or covers a large enough area, it can be absorbed into the bloodstream, potentially causing kidney failure or metabolic derangement.

8. How do doctors determine the "depth" of a chemical burn?
Doctors use clinical examination to assess skin color, sensation, and capillary refill. In complex cases, laser Doppler imaging may be used to assess tissue perfusion.

9. What is "coagulation necrosis"?
It is the process where acid causes skin proteins to clump together, forming a hard, protective crust (eschar) that can sometimes slow further penetration of the chemical.

10. When should I seek a follow-up appointment?
You should follow up with a burn specialist or plastic surgeon if you notice signs of infection (pus, increased redness, fever), if the wound does not heal within two weeks, or if you experience restricted movement in a joint.

Prognosis and Long-term Outlook

The prognosis for acid chemical burns is generally favorable if treated promptly. However, deep burns often require long-term multidisciplinary care, including specialized wound care, physiotherapy, and potentially reconstructive surgery. Psychological support is also a critical component of the recovery process, as burn survivors often deal with body image concerns and PTSD.

Disclaimer: This guide is for informational purposes and does not replace professional medical advice, diagnosis, or treatment. If you suspect you have a chemical burn, seek immediate emergency medical care.