Which Risk Factors Are Linked to Hyponatremia in Patients With AECOPD?

In patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD), smoking status, community-acquired pneumonia (CAP), anion gap (AG), erythrocyte sedimentation rate (ESR), and serum magnesium (Mg²⁺) all were independently associated with the development of hyponatremia, according to findings from a multicenter, cross-sectional study published in the journal BMC Pulmonary Medicine.

Hyponatremia, a common electrolyte disorder that is defined as a low blood sodium level, is often seen in the general population and among hospitalized patients. In patients with COPD, hyponatremia is an independent predictor of poor prognosis, including increased morbidity and rehospitalization. Researchers therefore sought to evaluate the risk factors for and underlying etiologies of hyponatremia in patients with AECOPD.

The study involved inpatients with COPD at 2 Chinese hospitals, Respiratory Medicine and Critical Care Medicine of Suining Central Hospital and at Second Affiliated Hospital of Chongqing Medical University, between January 2019 and December 2021. The final cohort that was analyzed included 413 patients — 323 with normonatremia (ie, serum sodium of 135 to 140 mmol/L) and 90 with hyponatremia (ie, serum sodium of <135 mmol/L). Researchers collected comprehensive data on patient demographics, comorbidities, underlying diseases, symptoms, and lung function. Chest high-resolution computed tomography scans and laboratory data were obtained from all participants.

Based on the data collected, the researchers used LASSO regression to select 9 potential hyponatremia-associated variables: nonsmoking, IPPV, CAP, pleural effusion, AG, procalcitonin (PCT), ESR, serum calcium ions, and serum Mg²⁺. Next, the researchers developed a binary regression model using the 9 variables to identify factors that were independently associated with hyponatremia patients with AECOPD, which were smoking status, CAP, AG, ESR, and serum Mg²⁺.

The investigators also constructed a nomogram to visualize and validate the binary logistics regression model. For the receiver operating characteristics (ROC) curve, the area under the curve (AUC) was 0.756 (95% CI, 0.699-0.813). The decision curve analysis (DCA) showed that when the threshold ranged between 10% and 52% with use of the nomogram to predict the likelihood of hyponatremia, it was associated with more net clinical benefits, thus indicating the clinical applicability of the nomogram.

Several limitations to the current study warrant mention. Because of its cross-sectional design, the associations between hyponatremia and prognosis and outcomes were not evaluated in patients with AECOPD. The etiologies of acute exacerbation, which are potentially linked to hyponatremia, were not explored. In addition, the study was conducted among Chinese patients only, which decreased confounders in the analysis. Further, the information and data regarding treatments in stable phases of COPD were not included in this analysis.

“Collectively, our data suggest that pneumonia, metabolic acidosis, and hypomagnesemia are the underlying etiologies and risk factors for hyponatremia in patients with AECOPD,” the study authors concluded, noting that the connections between these factors require further exploration.  “Additionally, magnesium was essential for serum sodium metabolism in AECOPD patients, implying hyponatremia and hypomagnesemia should be treated concurrently,” said the study authors.