Severe burn injury, burn shock, and smoke inhalation injury in small animals. Part 1: Burn classification and pathophysiology

Objective - To review the literature related to severe burn injury (SBI), burn shock, and smoke inhalation injury in domestic animals. Current animal-and human-based research and literature were evaluated to provide an overview of thermal burn classification and the pathophysiology of burn shock and smoke inhalation injury. Etiology - Severe burn injury, burn shock, and smoke inhalation injury may be encountered as a result of thermal injury, radiation injury, chemical injury, or electrical injury. Diagnosis - Burns can be subdivided based on the amount of total body surface area (TBSA) involved and the depth of the burn. Local burn injuries involve <20% of the TBSA whereas SBI involves >20-30% of the TBSA. The modern burn classification system classifies burns by increasing depth: superficial, superficial partial-thickness, deep partial-thickness, and full-thickness. Summary - Local burn injury rarely leads to systemic illness whereas SBI leads to significant metabolic derangements that require immediate and intensive management. SBI results in a unique derangement of cardiovascular dysfunction known as burn shock. The physiologic changes that occur with SBI can be divided into 2 distinct phases; the resuscitation phase and the hyperdynamic hypermetabolic phase. The resuscitation phase occurs immediately following SBI and lasts for approximately 24-72 hours. This period of hemodynamic instability is characterized by the release of inflammatory mediators, increased vascular permeability, reduced cardiac output, and edema formation. The hyperdynamic hypermetabolic phase begins approximately 3-5 days after injury. This phase is characterized by hyperdynamic circulation and an increased metabolic rate that can persist up to 24 months post burn injury in people.