Impact of Pleural Effusion on Clinical Outcomes in Patients with Pulmonary Embolism: Insights from the National Inpatient Sample

Background: The incidence of hospital admissions for pulmonary embolism (PE) and associated pleural effusion, and the impact of these effusions on outcomes on a national level is unknown. Methods: Data from the National Inpatient Sample between 2016 to 2019 was used to conduct a retrospective nationwide cohort study of hospital admissions for PE with and without pleural effusion. Multiple logistic regressions and linear regression analyses were used to determine the independent impact of effusions on in-hospital mortality, length of stay, and cost. Results: There were 937,744 hospital admissions with PE included in our analysis (median age 64 [interquartile range 50-76] years; 52.5% females). The in-hospital mortality rate overall was 3.7% which was 5.5% for patients with pleural effusion and 3.6% for patients without pleural effusion (p<0.001). The median length of stay was longer in the group with pleural effusion (6 [3-12] days vs 4 [2-6] days, p<0.001) and the median healthcare cost was higher among patients with pleural effusion (13,689 [7,279-30,915] vs 8,855 [5,472-16,531], p<0.001). The factors most associated with pleural effusion were atrial fibrillation (OR 1.89 95%CI 1.78-2.00, p<0.001) and arterial thrombosis (OR 1.48 95%CI 1.19-1.84, p<0.001). Pleural effusion was associated with increased odds of mortality in patients with PE (OR 1.30 95%CI 1.18-1.45, p<0.001). Pleural effusion was associated with increased length of stay (Coefficient 4.15 95%CI 3.99 to 4.32, p<0.001), and healthcare costs (Coefficient 12,164; 95%CI:11,639 to 12,688, p<0.001)). Conclusion: Concomitant pleural effusion is not uncommon among PE patients which is more common in patients with atrial fibrillation and previous arterial thrombosis. Pleural effusions in patients with PE are associated with higher in-hospital mortality, length of stay and cost.