Aspiration pneumonitis and pulmonary phospholipids.

Peptic aspiration pneumonitis (Mendelson's syndrome) results when gastric acid is aspirated into the lung, as may occur during anesthesia. In the present study, 0.1 N HCl was insufflated via the endotracheal tube into pentobarbital-anesthetized dogs in an amount sufficient to cause severe pulmonary damage. At death, the thorax was opened, the lungs grossly examined, and either weighed and desiccated for determination of wet/dry lung weight ratios, rinsed with saline for removal of alveolar surface phospholipids, or homogenized for whole lung phospholipid determination. Gross appearance and wet/dry lung weight ratios indicated severe pulmonary edema. The surface tension values of the lung wash were elevated over control values. Lysophophatidyl-choline (LPC) showed a striking increase over control values. Because LPC is a potent hemolytic agent which builds up in the lung following this pulmonary insult, and because increased hemorrhaging gradually develops following experimental acid insufflation, it is concluded that LPC is most probably causally related to the hemorrhagic pneumonia of Mendelson's syndrome.