Hyponatremia and hypernatremia are associated with increased 30-day mortality in hip fracture patients

Using data from the Danish national registries on 7317 patients, this study shows that abnormal plasma sodium levels, in the form of hyponatremia and hypernatremia, are prevalent and associated with increased 30-day mortality in hip fracture patients.

INTRODUCTION

The aim of this study was to examine the prevalence of hyponatremia and hypernatremia in patients admitted with a fractured hip as well as the association with 30-day in mortality in these patients.

METHODS

A total of 7317 hip fracture patients (aged 60 years or above) with admission plasma sodium measurements were included. Data on comorbidity, medication, and death was retrieved from Danish national registries. The association between plasma sodium and mortality was examined using Cox proportional hazard models.

RESULTS

The prevalence of hyponatremia and hypernatremia on admission was 19.0 and 1.7 %, respectively. Thirty-day mortality was increased for patients with hyponatremia (12.2 %, p = 0.005) and hypernatremia (15.5 %, p = 0.03) compared to normonatremic patients (9.6 %). After adjustment for possible confounding factors, hyponatremia (1.38 [1.16-1.64], p = 0.0003) and hypernatremia (1.71 [1.08-2.70], p = 0.02) were still associated with increased risk of death by 30 days. Looking at the association between changes in plasma sodium during admission and mortality, there was no difference between patients with normalized and persistent hyponatremia (10.4 vs 11.3 %, p = 0.6) while a lower mortality was found for normalized hypernatremia compared to persistent hypernatremia (12.4 vs 33.3 %, p = 0.03).

CONCLUSIONS

This study shows that abnormal plasma sodium levels are prevalent in patients admitted with a fractured hip and that both hyponatremia and hypernatremia are associated with increased risk of death within 30 days of admission.

Large-amplitude internal waves benefit corals during thermal stress

Tropical scleractinian corals are particularly vulnerable to global warming as elevated sea surface temperatures (SSTs) disrupt the delicate balance between the coral host and their algal endosymbionts, leading to symbiont expulsion, mass bleaching and mortality. While satellite sensing of SST has proved a reliable predictor of coral bleaching at the regional scale, there are large deviations in bleaching severity and mortality on the local scale that are poorly understood. Here, we show that internal waves play a major role in explaining local coral bleaching and mortality patterns in the Andaman Sea. Despite a severe region-wide SST anomaly in May 2010, frequent upslope intrusions of cold sub-pycnocline waters due to breaking large-amplitude internal waves (LAIW) mitigated coral bleaching and mortality in shallow waters. In LAIW-sheltered waters, by contrast, bleaching-susceptible species suffered severe bleaching and total mortality. These findings suggest that LAIW benefit coral reefs during thermal stress and provide local refugia for bleaching-susceptible corals. LAIW are ubiquitous in tropical stratified waters and their swash zones may thus be important conservation areas for the maintenance of coral diversity in a warming climate. Taking LAIW into account can significantly improve coral bleaching predictions and provide a valuable tool for coral reef conservation and management.