Development of acute burn shock in unresuscitated guinea pigs.

Conscious guinea pigs were used to study the development of burn shock as a function of the size of thermal injury to the body surface. Scale burns equivalent to 0 (control, n = 18), 15.7 +/- 0.8% (n = 11), 24.6 +/- 0.5% (n = 10), and 43.4 +/- 1.5% (n = 10) of total body surface area were obtained by use of a template device, while the animals were deeply anesthetized with methoxyflurane. Circulatory function was assessed without further anesthetic restraint before and at 1, 2, 4, 6, 8, and 24 hr after burn. Values from control guinea pigs varied little during the observation period. Hemodynamic functions of burned guinea pigs were abnormal, and both the magnitude and duration of dysfunction generally depended upon the size of injury. Burn shock was characterized by hemo-concentration, hypothermia, tachycardia (bradycardia in the 43.4% group), minimal adjustments in systemic blood pressure, hyperkalemia, normonatremia (hyponatremia in the 43.4% group) arterial acidemia, and decreased respiratory rate. Circulatory functions of the 15.7% and 24.6% groups returned toward control levels during 8 hr after burn. Severe shock persisted in the 43.4% group, which experienced 70% mortality by 24 hr. These experiments characterize the guinea pig as a reproducible small animal model for studying different severities of burn shock unencumbered by secondary influences associated with general anesthesia.