Hospital readmissions are frequent, harmful and costly—18% of Medicare patients can expect to be readmitted within 30 days in the United States at a cost of more than $17 billion.¹ Recent changes in health care policy aimed at reducing readmission have substantially increased attention to this major health care issue.

Rationale: Although associated with adverse outcomes in other cardiopulmonary conditions, the prognostic value of hyponatremia, a marker of neurohormonal activation, in patients with acute pulmonary embolism (PE) is unknown. Objectives: To examine the associations between hyponatremia and mortality and hospital readmission rates for patients hospitalized with PE. Methods: We evaluated 13,728 patient discharges with a primary diagnosis of PE from 185 hospitals in Pennsylvania (January 2000 to November 2002). We used random-intercept logistic regression to assess the independent association between serum sodium levels at the time of presentation and mortality and hospital readmission within 30 days, adjusting for patient (race, insurance, severity of illness, use of thrombolytic therapy) and hospital factors (region, size, teaching status). Measurements and Main Results: Hyponatremia (sodium ≤135 mmol/L) was present in 2,907 patients (21.1%). Patients with a sodium level greater than 135, 130–135, and less than 130 mmol/L had a cumulative 30-day mortality of 8.0, 13.6, and 28.5% (P < 0.001), and a readmission rate of 11.8, 15.6, and 19.3% (P < 0.001), respectively. Compared with patients with a sodium greater than 135 mmol/L, the adjusted odds of dying were significantly greater for patients with a sodium 130–135 mmol/L (odds ratio [OR], 1.53; 95% confidence interval [CI], 1.33–1.76) and a sodium less than 130 mmol/L (OR, 3.26; 95% CI, 2.48–4.29). The adjusted odds of readmission were also increased for patients with a sodium of 130–135 mmol/L (OR, 1.28; 95% CI, 1.12–1.46) and a sodium less than 130 mmol/L (OR, 1.44; 95% CI, 1.02–2.02). Conclusions: Hyponatremia is common in patients presenting with PE, and is an independent predictor of short-term mortality and hospital readmission.

Summary: The Pulmonary Embolism Severity Index (PESI) is a validated clinical prognostic model for patients with pulmonary embolism (PE). Recently, a simplified version of the PESI was developed. We sought to compare the prognostic performance of the original and simplified PESI. Using data from 15,531 patients with PE, we compared the proportions of patients classified as low versus higher risk between the original and simplified PESI and estimated 30-day mortality within each risk group. To assess the models’ accuracy to predict mortality, we calculated sensitivity, specificity, and predictive values and likelihood ratios for low-versus higher-risk patients. We also compared the models’ discriminative power by calculating the area under the receiver-operating characteristic curve. The overall 30-day mortality was 9.3%. The original PESI classified a significantly greater proportion of patients as low-risk than the simplified PESI (40.9% vs. 36.8%; p<0.001). Low-risk patients based on the original and simplified PESI had a mortality of 2.3% and 2.7%, respectively. The original and simplified PESI had similar sensitivities (90% vs. 89%), negative predictive values (98% vs. 97%), and negative likelihood ratios (0.23 vs. 0.28) for predicting mortality. The original PESI had a significantly greater discriminatory power than the simplified PESI (area under the ROC curve 0.78 [95% CI: 0.77–0.79] vs. 0.72 [95% CI: 0.71–0.74]; p<0.001). In conclusion, even though the simplified PESI accurately identified patients at low-risk of adverse outcomes, the original PESI classified a higher proportion of patients as low-risk and had a greater discriminatory power than the simplified PESI.Institution where the work was carried out: Division of General Internal Medicine, Bern University Hospital, Bern, Switzerland.