Hyper- and hyponatremia linked to adverse COVID-19 outcomes
In the study, 5.3% of the 488 patients had hypernatremia at hospital presentation, and 24.6% had hyponatremia. Of note, only 19% of those with hyponatremia underwent laboratory workup to determine the etiology. Of those, three quarters had hypovolemic hyponatremia, determined on the basis of a urinary sodium cutoff of 30 mmol/L.
The total in-hospital mortality rate was 31.1%. There was a strong, although nonsignificant, trend toward higher mortality in association with sodium status at admission. Death rates were 28.4%, 30.8%, and 46.1% for those who were normonatremic, hyponatremic, and hypernatremic, respectively (P = .07). Baseline serum sodium levels didn’t differ between survivors (137 mmol/L) and nonsurvivors (138 mmol/L).
In multivariable analysis, the occurrence of hypernatremia at any point during the first 5 days in the hospital was among three independent risk factors for higher in-hospital mortality (adjusted hazard ratio, 2.74; P = .02). The other risk factors were older age and higher CRP level.
Overall, hyponatremia was not associated with death (P = .41).
During hospitalization, 37.9% of patients remained normonatremic; 36.9% experienced hyponatremia; 10.9% had hypernatremia; and 14.3% had both conditions at some point during their stay.
In-hospital mortality was 21% among those with normonatremia, compared with 56.6% for those with hypernatremia (odds ratio, 3.05; P = .0038) and 45.7% for those with both (OR, 2.25; P < .0001).
The 28.3% mortality rate in the overall group that experienced hyponatremia didn’t differ significantly from the 21.1% in the normonatremic group (OR, 1.34; P = .16). However, the death rate was 40.9% among the subgroup that developed hypovolemic hyponatremia, significantly higher than the normonatremic group (OR, 2.59, P = .0017).
The incidence of hyponatremia decreased from 24.6% at admission to 14.1% 5 days later, whereas the frequency of hypernatremia rose from 5.3% to 13.8%.
Key finding: Link between hospital-acquired hypernatremia and death
“The key novel finding of our study was that hospital-acquired hypernatremia, rather than hypernatremia at admission, was a predictor for in-hospital mortality, with the worst prognosis being reported in patients with the largest increase in serum sodium in the first 5 days of hospitalization,” noted Dr. Tzoulis and colleagues.
Hypernatremia was present in 29.6% of nonsurvivors, compared with 5.2% in survivors.
Among 120 patients with hyponatremia at admission, 31.7% received advanced respiratory support, compared with 17.5% and 7.7% of those with normonatremia or hypernatremia, respectively (OR, 2.18; P = .0011).
In contrast, there was no difference in the proportions needing ventilatory support between those with hypernatremia and those with normonatremia (16.7% vs. 12.4%; OR, 1.44; P = .39).
Acute kidney injury occurred in 181 patients (37.1%). It was not related to serum sodium concentration at any time point.
Dr. Tzoulis and Dr. Simpson disclosed no relevant financial relationships.
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