Hypernatraemia worsens disease severity in ICU polytrauma patients

In patients hospitalized for polytrauma, hypernatraemia acquired in the intensive care unit (ICU) seems to worsen injury severity, and may be preceded by lowered renal sodium and chloride excretion, a new study has found.

Researchers retrospectively evaluated 101 polytrauma patients (median age 45 years, 81 percent men) requiring ICU treatment. Hypernatraemia was determined based on whole-blood sodium levels, as assessed by blood-gas analyses. Injury severity was evaluated using the abbreviated injury scale (AIS); in-hospital mortality and length of ICU stay were also documented.

Overall, 47.5 percent (n=48) of the patients developed hypernatraemia during their stay in the ICU. Compared with the nonhypernatraemic group, no significant differences were reported in terms of age, sex distribution, comorbidities, and mortality.

On the other hand, the median injury severity score (ISS) was significantly higher in patients with hypernatraemia (32 vs 24; p=0.011), as was AIS in the head or neck (2.5 vs 2.0; p=0.032). Length of stay in the ICU was also significantly longer in hypernatraemic patients (12 vs 8 days; p=0.021).

In terms of fluid balance, patients with hypernatraemia showed significantly elevated levels of sodium throughout the observation period, though concentrations were within normal ranges upon admission.

Notably, on the first day of admission, the fractional excretion of sodium was significantly reduced in hypernatraemic patients (0.41 percent vs 1.11 percent; p=0.007). This remained lower, although nonsignificantly so, until day 4.

Similarly, urinary sodium and chloride concentrations were likewise lower in hypernatraemic patients during the early days of admission. When looking only at the time period prior to the onset of hypernatraemia, median urine sodium and chloride levels were decreased as compared with nonhypernatramic patients.