Moderate smoke inhalation produces decreased oxygen delivery, increased oxygen demands, and systemic but not lung parenchymal lipid peroxidation

We studied the first 24-hour lung and systemic physiologic response to a moderate smoke inhalation injury. In addition, we monitored oxidant-induced lipid peroxidation (LP), using malondialdehyde and conjugated dienes. Sixteen adult sheep with lung and soft tissue lymph fistulas were given 20 breaths of smoke while under anesthesia. Eight sheep were given a tidal volume of 5 ml/kg smoke, confining the inflammatory injury to airways only. Eight sheep were given 10 ml/kg smoke after which focal alveolar collapse and a carboxyhemoglobin level of 28% +/- 5% were noted in addition to airways injury. No significant lung or systemic physiologic changes were noted in the 5 ml/kg smoke exposure. However, plasma levels of malondialdehyde increased significantly, indicating that LP had occurred. With the 10 ml/kg smoke exposure, a 50% early decrease in oxygen consumption was noted. At 12 hours, oxygen consumption was then significantly increased by 30% over baseline. Fluid requirements to maintain filling pressures were also significantly increased, comparable to that seen after a 20% total body surface burn. A change in soft tissue permeability was noted with a twofold increase in systemic lymph, which could in part explain the fluid requirements. Lung lymph flow increased by only twofold, and lung water was not increased, whereas arterial partial oxygen pressure decreased from a baseline of 95 +/- 4 mm Hg to 60 +/- 5 mm Hg. Systemic LP was evident when both plasma malondialdehyde and conjugated dienes increased significantly. Liver tissue malondialdehyde at postmortem examination was double the normal level. However, lung parenchymal malondialdehyde was not increased.(ABSTRACT TRUNCATED AT 250 WORDS)