Several factors affect the outcome in burned patients. These include the depth of burn involvement, the extent of the burn, the source of the burn, the age of the patient, and the presence of inhalation injury.
Parameters:
(1) age in years
(2) percent of body surface area wth second and third degree burns
(3) percent of body surface area with third degree burns
(4) prior bronchopulmonary disease
(5) PaO2 in mm Hg
(6) airway edema
Z =
= (0.036 * (age of patient in years)) + (0.037 * (total %BSA with 2nd & 3rd degree burns)) + (0.028 * (%BSA with 3rd degree burns)) + (0.40 if prior bronchopulmonary disease) + (0.52 if PaO2 < 70 mm Hg on 20-40% oxygen) + (0.56 if airway edema)
where:
• Prior bronchopulmonary disease includes: hospitalization for bronchitis or pneumonia within past 3 years, asthma, emphysema, COPD, pulmonary tuberculosis or deep fungal infection, lung cancer.
An equation approximating the curve in Figure 1 (Zawacki, 1979) which maps Z to probability of fatal outcome is:
probability of fatal outcome =
= (0.0031128 * Z^5) - (0.06103 * Z^4) + (0.4293724 * Z^3) - (1.29905 * Z^2) + (1.80694 * Z) - 0.95089
Limitations:
• While a historically useful formula, advances in burn management have significantly reduced morbidity and mortality, so that the probability of fatal outcome derived is no longer accurate. However, it can be used to give an idea of what the mortality might have been before current treatment was available.
