Effects of burns on inhalation injury in sheep: A 5-day study

Background: We have previously reported that infliction of thermal injury immediately after smoke exposure did not accentuate pulmonary dysfunction during the subsequent 48 h. The purpose of this study was to determine whether thermal injury would aggravate pulmonary dysfunction during a longer postinjury period of 5 days. Methods: Six sheep (G1) received 12 units of smoke inhalation injury (SII) alone; seven sheep (G2) received a 40% full-thickness scald burn immediately after SII. All sheep were resuscitated with lactated Ringer's solution for the first 48 h. After 48 h, animals were fed food and water ad libitum. Cardiopulmonary variables and blood gases were measured serially. At the end of the 5-day experimental period, VA/Q distribution was analyzed using the multiple inert gas elimination technique (MIGET). Lung wet to dry (W/D) weight ratios and malondialdehyde (MDA) concentrations were determined. Results: Cardiac index in G2 significantly increased and remained higher compared with G1. There was no difference in A-aDo(2) between the two groups. There was also no difference between the two groups by MIGET study, or in terms of lung MDA and W/D weight ratios. None of the animals manifested symptoms of infection. Conclusion: Despite the difference in the hemodynamic changes induced by the addition of a 40% burn to smoke inhalation injury, pulmonary dysfunction was not accentuated during the 5-day study period in the absence of infection.