Effect of granulocytopenia on extravascular lung water content after microembolization

We studied granulocyte entrapment in the lung after pulmonary microembolization to see if it contributes to the increase in extravascular water content. The lungs were embolized by intravenous injection of nonsiliconized glass beads (100 micrometers in diameter) in normal dogs and dogs made granulocytopenic by daily injections of hydroxyurea. Hydroxyurea did not significantly alter the platelet and fibrinogen concentrations. Control and treated dogs were embolized to the same degree, which resulted in similar increases in pulmonary arterial pressure and pulmonary vascular resistance. The extravascular lung water content/bloodless dry lung weight (W/D) ratios in the control and treated groups after embolization were compared with the W/D ratios in the control and treated nonembolized groups, respectively. The W/D ratio increased from the value of 2.84 +/- 0.22 ml/g in the control group to 4.54 +/- 0.19 ml/g at 75 min after embolization (60% increase) (p < 0.05). However, the W/D ratio in the control-granulocytopenic group of 3.54 +/- 0.19 ml/g was not significantly different from the value of 4.09 +/- 0.27 ml/g in the granulocytopenic group after embolization. Because embolization after granulocytopenia produced only a 16% increase in the extravascular lung water content, compared with a 60% increase in the treated group after the same degree of embolization, the results suggested that granulocyte entrapment in the lung after microembolization contributes to the development of pulmonary edema.