Pulmonary surfactant abnormalities have consistently been documented in patients with acute lung injury (ALI), however, there is little evidence directly correlating them to altered respiratory mechanics. To explore this further, surfactant composition was measured in lung aspirate fluid collected on 15 occasions from 10 patients with ALI. The composition was compared with lung aspirate fluid from 11 intubated patients prior to elective cardiac surgery (CS), and bronchoalveolar lavage fluid from 16 normal subjects. In both the ALI and cardiac groups the proportion of disaturated phospholipids (DSP) and phosphatidylcholine was reduced. Plasma levels of surfactant proteins-A and -B (SP-A and -B) were elevated, but were unrelated to alveolar surfactant levels. In the ALI group, and the ALI + CS group, DSP, normalized to the total phospholipid content, sphingomyelin (SPH), and urea, showed strong direct correlations with arterial oxygen tension/inspiratory oxygen fraction (all p < or = 0.01). In the ALI group, normalized DSP was also directly related to the elastance of the positive end-expiratory pressure-induced increase in the end-expiratory lung volume (all p < or = 0.02), and indirect correlations were found with a measure of lung overinflation (%E2; all p < or = 0.01). We conclude that surfactant composition correlates with lung function abnormalities in acute lung injury and cardiac patients, and that both groups had elevated plasma surfactant proteins-A and -B levels, consistent with a concurrent increase in alveolocapillary permeability.

1. Although abnormalities in pulmonary surfactant were initially implicated in the pathogenesis of the acute respiratory distress syndrome (ARDS) 30 years ago, most subsequent research has focused on mediators of the parenchymal acute lung injury (ALI) and the associated increase in alveolocapillary permeability. 2. Surfactant is essential for normal breathing and the severity of ALI correlates with surfactant dysfunction and abnormalities in surfactant composition; however, no relationship has been shown with respiratory system compliance. In neonates and most animal models, respiratory system compliance will directly reflect the elastic properties of the lung. However, the greater vertical height of the chest wall in adults, in combination with the increase in lung density due to ALI, results in dependent collapse of alveoli. Because simple, global measurement of compliance is strongly influenced by the volume of aerated lung, alternative measures of respiratory mechanics may reflect surfactant dysfunction. 3. Using a dynamic, volume-dependent model of respiratory mechanics to indirectly reflect this heterogeneous inflation, we have found direct relationships with surfactant composition in patients with ARDS. A failure of surfactant to increase surface tension in large alveoli may also explain why lung overdistension occurs at relatively low pressures. Furthermore, surfactant dysfunction will exaggerate heterogeneous lung inflation, augmenting regional overinflation, and is essential for ALI secondary to repetitive opening and closing of alveoli during tidal ventilation. 4. Ventilation-induced ALI has also been shown to result in massive increases in pro-inflammatory cytokines within the lung. Because ALI itself fails to compartmentalize cytokines, with spillover into the systemic circulation resulting in distant organ dysfunction, surfactant dysfunction may have widespread implications.

Background/Objective: Alteplase may elevate international normalized ratio (INR) results, although the exact rate of elevation occurrence is not firmly established in the literature. The purpose of this study is to determine the occurrence rate of INR elevation following alteplase administration. We also aimed to determine what factors are independently associated with the development of elevated INR following alteplase administration for ischemic stroke. Methods: We conducted a multicenter, retrospective, cohort study of patients who received alteplase for acute ischemic stroke. Patients were screened for baseline INR measurement and a repeat value within 24 hours of alteplase administration. The primary outcome was the percent of patients who experienced ≥0.4-point increase in INR. Secondary outcomes included the rate of adverse bleeding events and identification of factors independently associated with elevated INR following alteplase administration. Results and Conclusions: Two hundred and sixty-one patients were included, with 44 (16.9%) patients having an INR increase of 0.4 or more. Patients with an INR increase ≥0.4 experienced a nonstatistically significant increase in bleeding episodes (8.8% vs 18.2%; P = .10). We identified African American race (odds ratio, 3.48, 95% confidence interval, 1.5-7.6; P = .002) as an independent predictor of INR increase ≥0.04. An INR elevation is common following receipt of alteplase for ischemic stroke. Those of African American race were at increased risk of INR elevation; however, more studies are needed to determine whether these patients are at a higher bleeding risk as a result of INR elevation.

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