Impaired lung oxygenation in acute aortic dissection

In the early phase after the onset of acute aortic dissection, oxygenation impairment often occurs. However, the etiology and clinical course of this phenomenon have not been established. We examined the serial changes of oxygenation, inflammatory reaction and laboratory data in patients with acute aortic dissection.

Nine patients (DeBakey type I; 4, type II; 3 and type IIIb; 2), aged 46 to 82 years were included in this study. All patients were managed in the intensive care unit, and systolic arterial pressure was maintained at around 110 to 120 mm Hg. Oxygenation was impaired in all patients, three (33%) of whom required mechanical ventilatory support.

Pleural effusion was observed in eight (89%) of nine patients. Respiratory index was 0.98+/-0.19 (mean +/-SEM) at the time of admission, and elevated to 1.59+/-0.35, 1.58+/-0.21, 1.60+/-0.28 respectively, at day 1, 2 and 3. Oxygenation index was 318+/-34 at the time of admission, and decreased to 271+/-34, 255+/-19, 263+/-26, respectively, at day 1, 2 and 3. These values recovered to normal after day 4. The increase of white blood cells and high fever (>38 degrees C) continued until day 3. Platelet counts recovered after day 4. The serum bilirubin level was highest (2.0+/-0.5 mg/dl) at day 3, and decreased gradually after day 4. In two recent patients whose serum interleukin-8 (IL-8) was measured, IL-8 levels increased according to the impaired oxygenation or aneurysmal enlargement. Impaired oxygenation, inflammatory changes, platelet consumption and bilirubin elevation continued until day 3 and resumed normal levels after day 4.

These changes may be due to hemolysis, consumption coagulopathy or inflammation associated with acute aortic dissection. IL-8 elevation may be associated with aneurysmal enlargement and these phenomena.