Severe intensive care unit-acquired hypernatraemia: Prevalence, risk factors, trajectory, management, and outcome

Severe intensive care unit-acquired hypernatraemia (ICU-AH) is a serious complication of critical illness. However, there is no detailed information on how this condition develops.

The objective of this study was to study the prevalence, risk factors, trajectory, management, and outcome of severe ICU-AH (≥155 mmol·L^-1).

A retrospective study was conducted in a 40-bed ICU in a university-affiliated hospital. Assessment of sodium levels, factors associated with severe ICU-AH, urinary electrolyte measurements, water therapy, fluid balance, correction rate, and delirium was made.

We screened 11,642 ICU admissions and identified 109 patients with severe ICU-AH. The median age was 57 years, 63% were male, and the median Acute Physiology and Chronic Health Evaluation III score was 64 (52; 80). On the day of ICU admission, 64% of patients were ventilated; 71% received vasopressors, and 22% had acute kidney injury. The median peak sodium level was 158 (156; 161) mmolL^-1 at a median of 4 (1; 11) days after ICU admission. Only eight patients (7%) had urine sodium measurement (median concentration: 17 mmol·L^-1). On the day of peak hypernatraemia, 80% of patients were unable to drink due to invasive ventilation; 34% were on diuretics; 25% had fever, and 50% did not receive hypotonic fluids. When available, the median electrolyte-free water clearance was -1.1 L (-1.7; -0.5), representing half of the urine output. After peak hypernatraemia, the correction rate was -2.8 mmol·L^-1 per day (95% confidence interval: [-2.9 to -2.6]) during the first 3 d.

Severe hypernatraemia occurred in the setting of inability to drink, near-absent measurement of urinary free water losses, diuretic therapy, fever, renal impairment, and near-absent or limited or delayed water administration. Correction was slow.