Analysis of the Impact of the Rate of Severe Hyponatremia Correction on Clinical Outcomes

Background: Hyponatremia correction is well known associated with a extremely rare, albeit severe event, osmotic demyelination. Guidelines therefore strongly recommend a rate of correction no faster than 6 mEq/L/24h. Here, we sought to investigate whether faster correction of severe hyponatremia is associated with longer length of hospital stay (LOS) and mortality. Methods: We reviewed medical records for hospitalized patient who had severe hiponatremia (Na< 125 mEq/L) during a year. Variables related to hyponatremia diagnosis and other clinical characteristics were assessed. Then we analyzed through regression analysis whether the rate of Na correction within 24h above 6 mEq/L was independently associated with either prolonged LOS (defined as above the median duration time) or mortality. Results: We evaluated N=304 hyponatremic (Na<125 mEq/L) patients. Overall, age was 60 IQR 47-69; 86% had chronic (>48h) hyponatremia, 37% were admitted in the ICU, and 18% were under dialysis. Out of 304, 129 patients (42.5%) had Na correction rate higher than 6 mEq/L/d (rapid correction, RC). RC group had lower baseline Na levels (122 IQR 116-124 vs 123 IQR 120-125 mEq/L, P=0.001), but compared to controls had similar age, baseline sCr, heart failure, cirrhosis, cancer, AKI and CKD diagnosis, but less hypertension and diabetes cases. The hospital LOS was significantly higher for RC group (23 IQR 11-52 vs 19 IQR 10-33 days, p=0.012), but after regression analysis the model found other variables associated with prolonged LOS (> 20d): admission in the ward, type of hyponatremia and ICU admission. Overall mortality was 20% and did not differ between groups. Besides the Na correction rate cutoff of 6 mEq/L/d, sensitivity analysis showed that neither 10 mEq/L/d nor the rate of Na correction (as a continuous variable) remained as predictor of hospital LOS or mortality. Lactate, vasopressor use and heart failure were independent variables associated with mortality in this cohort. Conclusion: Our study strongly suggest that the rate of correction of a severe hyponatremia above the limits defined by current guidelines does not impact on LOS and mortality, and appears to be safe regarding these outcomes.