Understanding Burn Injuries: Types, Assessment, and Complications

Exam Tip: A hallmark of full-thickness burns is that the patient may report a lack of pain at the site of the deepest injury because the nerve endings have been completely destroyed.

Mechanisms of Injury

The method by which the burn occurred provides critical information regarding the potential for internal injury and the required treatment protocol.

• Thermal Burns: These account for approximately 90% of all burn traumas. They result from exposure to fire, hot objects, or steam. A specific subtype is the scald burn, caused by hot liquids or grease. Scalds are particularly dangerous because hot liquids conduct heat more efficiently than air, and temperatures of $70^\circ\text{C}$ or higher can be fatal.
• Chemical Burns: Making up less than 10% of cases, these are often caused by industrial accidents or the ingestion of household chemicals, such as strong acids, alkalis, or corrosives. These agents induce protein coagulation. Immediate management involves removing clothing and irrigating the area to neutralize the chemical.
• Electrical Burns: These also account for less than 10% of burns. Injuries range from mild shocks (low voltage, $100$–$220\text{ V}$) to fatal high-voltage exposures ($>1000\text{ V}$). Clinicians should look for entrance and exit wounds and monitor for heart conduction issues, nerve damage, and muscle damage.
• Radiation Burns: These can be caused by external or internal radiation contamination and may even be a concern in bioterrorism scenarios. Symptoms may not become visible for several weeks. Radiation is measured in Rads (the absorbed dose to tissue) and Rems (the biological risk of exposure).

Assessment: The Rule of Nines

To determine the severity of a burn and guide fluid resuscitation, clinicians must estimate the Total Body Surface Area (TBSA) affected. The Rule of Nines is a rapid method used in emergent phases to divide the body into regions representing 9% or multiples of 9%.

Systemic Complications

A major burn injury is not just a skin problem; it is a systemic crisis that impacts multiple organ systems.

Circulatory and Musculoskeletal Complications

A significant risk arises from circumferential burns—burns that wrap entirely around a limb or the torso. These burns create a tough, inelastic layer of dead tissue known as eschar. As swelling (edema) increases underneath this inelastic layer, pressure builds, which can lead to:

1. Compartment Syndrome: In extremities, this pressure restricts blood flow, leading to ischemia and potential tissue death.
2. Airway Obstruction: If a circumferential burn occurs on the neck, it can restrict venous return and obstruct the airway.

Respiratory Complications

Patients often experience an increased respiratory rate and elevated minute ventilation. This is frequently a physiological response to intense pain or acute anxiety.

Gastrointestinal (GI) Complications

When burns exceed 35% TBSA, the body's sympathetic nervous system response and resulting hypovolemia (low blood volume) decrease blood flow to the GI tract. This can lead to:

• Decreased motility and paralytic ileus.
• Ischemia and sloughing of the gastric mucosa.
• Curling’s Ulcers: Severe physiological stress from the burn can trigger these acute gastric ulcers.

Genitourinary (GU) and Renal Complications

The kidneys are highly susceptible to the effects of a major burn.

• Renal Ischemia and Acute Kidney Injury (AKI): Hypovolemia triggers the renin-angiotensin-aldosterone system, which causes the body to retain sodium and water to compensate for fluid loss. If fluid resuscitation is inadequate, the resulting renal ischemia can lead to AKI.
• Myoglobinuria: In electrical burns, significant muscle breakdown occurs. This releases myoglobin into the bloodstream, which can obstruct renal tubules, leading to acute tubular necrosis and renal failure.

Summary Table for Renal Risk