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

Background: 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.

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

Methods: 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.

Results: 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.

Conclusions: 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.