Inadvertent sodium loading in critically ill patients

Abstract

Background: Recommended daily intake of sodium is 1- 2mmol/kg. Sodium administration is rarely separated from fluid administration in critically ill patients.

Objective: To estimate the amount of sodium administered to patients who were invasively ventilated, and to investigate whether sodium administration affected oxygenation, length of stay in ICU and serum sodium level.

Design, participants and setting: Retrospective audit of adult patients who received invasive mechanical ventilation for ≥ 5 days in a tertiary-level intensive care unit.

Main outcome measures: Total sodium administered from resuscitation and maintenance fluids, infusions, flushes, medicines, transfusions, enteral feeds and total parenteral nutrition; oxygenation, length of ICU stay and serum sodium level.

Results: 13 men and 7 women were included. Their median age was 71.9 years (range, 19.8-89.2 years). Median duration of mechanical ventilation was 9 days (range, 6-20 days) and median ICU stay 11.6 days (range, 6-21 days). Median APACHE II score was 29 (range, 18-41). Daily sodium administration was 225.5mmol (151-355mmol). The median daily net fluid balance was 351mL (range, - 759 to +1125mL) and median daily fluid intake was 2352mL (range, 1437- 3798mL). Daily sodium administered correlated with net fluid balance (P<0.001; r=0.35). Of total sodium administered, infusions contributed 22.2% (1.2%-39.9%); drugs 21.6% (0.0-35.5%); flushes 17.4% (9.3%-24.5%); enteral feeds 17% (0.0-39.5%); resuscitation 16.0% (2.5%-36.9%); maintenance fluids 5.8% (0.0-24.0%); transfusions 3.9% (0.0-9.5%) and parenteral nutrition 0.1% (0.0-2.6%).

Conclusion: Sodium administration to this cohort of critically ill patients requiring prolonged mechanical ventilation was high. Further studies should examine ways of limiting the amount of sodium administered to such patients and to examine if this influences patient outcomes.