Abstract

Background Recent studies have challenged assumptions about slow correction of severe hyponatremia and have shown that rapid correction is associated with shorter hospital length of stay. However, the confounding effect of admission diagnosis has not been fully explored. The objective of this study was to determine whether rapid correction is still associated with shorter length of stay when controlling for admission diagnosis.

Methods This retrospective cohort study is based on the Medical Information Mart for Intensive Care, including data from both MIMIC-III (2001-2012) and MIMIC-IV (2008-2019). Patients were identified who presented to the hospital with initial sodium <120 mEq/L and were categorized according to total sodium correction achieved in the first day (<6 mEq/L; 6-10 mEq/L; >10 mEq/L). Linear regression was used to assess for an association between correction rate and hospital length of stay, and to determine if this association was significant when controlling for admission diagnosis classifications based on diagnosis related groups (DRGs).

Results There were 636 patients included in this study. Median [IQR] hospital length of stay was 7 [4, 11] days. Patients had a median [IQR] initial sodium value of 117 [114, 118] mEq/L and final sodium value of 124 [119, 128] mEq/L. In a univariate linear regression, the highest rate of correction (>10 mEq/L) was associated with a shorter length of stay than a moderate rate of correction (coef. −2.363, 95% CI [−4.710, −0.017], p=0.048), but the association was not significant when controlling for admission diagnosis group (coef. −1.685, 95% CI [−3.836, 0.467], p=0.125).

Conclusions Faster sodium correction was not associated with shorter length of stay when controlling for admission diagnosis categories, suggesting that the disease state confounds this association. While some patients may be discharged earlier if sodium is corrected more rapidly, others may not benefit or may be harmed by this strategy.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

LAC was supported by the National Institutes of Health NIBIB R01 (EB017205).

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The Medical Information Mart for Intensive Care (MIMIC-III/IV): https://mimic.mit.edu/. This is available to all researchers with an appropriate research plan and human subjects training (e.g. CITI).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

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Yes

AbbreviationsCPMCentral Pontine MyelinolysisDRGDiagnosis Related GroupICDInternational Classification of DiseasesICUIntensive Care UnitMIMICMedical Information Mart for Intensive CareODSOsmotic Demyelination Syndrome