Intensive care unit-acquired hyponatremia in critically ill medical patients

Jae Kyeom Sim,Soo Jin Na,Kyeongman Jeon,Ryoung-Eun Ko,Gee Young Suh

doi:10.1186/s12967-020-02443-4

Abstract

BackgroundPrevious research has focused on intensive care unit (ICU)-acquired hypernatremia; however, ICU-acquired hyponatremia has frequently been overlooked and has rarely been studied in surgical or mixed ICUs. The aim of this study is to investigate the incidence of ICU-acquired hyponatremia, the risk factors associated with its development, and its impact on outcomes in critically ill medical patients.MethodsWe conducted a retrospective cohort study based on the prospective registry of all critically ill patients admitted to the medical ICU from January 2015 to December 2018. Baseline characteristics and management variables were compared between ICU-acquired hyponatremia and normonatremia patients.ResultsOf 1342 patients with initial normonatremia, ICU-acquired hyponatremia developed in 217 (16.2%) patients and ICU-acquired hypernatremia developed in 117 (8.7%) patients. The Sequential Organ Failure Assessment (8.0 vs 7.0, P = 0.009) and Simplified Acute Physiology Score 3 scores (55.0 vs 51.0, P = 0.005) were higher in ICU-acquired hyponatremia patients compared with normonatremia patients. Baseline sodium (137.0 mmol/L vs 139.0 mmol/L, P < 0.001), potassium (4.2 mmol/L vs 4.0 mmol/L, P = 0.001), and creatinine (0.98 mg/dL vs 0.88 mg/dL, P = 0.034) levels were different between the two groups. Net volume balance over first 3 days was higher in ICU-acquired hyponatremia patients (19.4 mL/kg vs 11.5 mL/kg, P = 0.004) and was associated with the development of ICU-acquired hyponatremia (adjusted odds ratio, 1.004; 95% confidence interval, 1.002–1.007; P = 0.001). ICU mortality was similar in both groups (15.2% vs. 14.4%, P = 0.751), but renal replacement therapy was more commonly required in ICU-acquired hyponatremia patients (13.4% vs 7.4%, P = 0.007).ConclusionsICU-acquired hyponatremia is not uncommon in critically ill medical patients. Increased volume balance is associated with its development. ICU-acquired hyponatremia is related to increased use of renal replacement therapy but not to mortality.

Highlights

Previous research has focused on intensive care unit (ICU)-acquired hypernatremia; ICUacquired hyponatremia has frequently been overlooked and has rarely been studied in surgical or mixed ICUs
Patients who met the following criteria were excluded: (1) admission for postoperative care or neurological disorders with the exception of meningitis and metabolic coma, (2) hypo- or hypernatremia ([Na+] < 135 mmol/L or [Na+] > 145 mmol/L) at the time of ICU admission, (3) dependency on renal replacement therapy (RRT) at the time of ICU admission, or (4) refusal to be registered in our database
To address the primary research objective of determining the factors associated with the development of ICU-acquired hyponatremia and clinical outcomes, patients with ICU-acquired hypernatremia were excluded from the final analysis

Summary

Introduction

Previous research has focused on intensive care unit (ICU)-acquired hypernatremia; ICUacquired hyponatremia has frequently been overlooked and has rarely been studied in surgical or mixed ICUs. The aim of this study is to investigate the incidence of ICU-acquired hyponatremia, the risk factors associated with its develop‐ ment, and its impact on outcomes in critically ill medical patients. A few studies have revealed that ICU-acquired hyponatremia is not uncommon and has been observed to affect critically ill patients at a rate of 1 in 9 or higher. It is associated with increased hospital mortality [4, 9,10,11]. We investigated the incidence of ICU-acquired hyponatremia, the risk factors associated with its development, and its impact on patient outcomes in medical ICU

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