Outcome and frequency of sodium disturbances in neurocritically ill patients

Abstract

Sodium disturbances are frequent and serious complications in neurocritically ill patients. Hyponatremia is more common than hypernatremia, which is, however, prognostically worse. The aim of this study was to analyse outcome and frequency of sodium disturbances in relation to measured serum osmolality in neurologic-neurosurgical critically ill patients. A 5-year retrospective collection of patients (pts) and laboratory data were made from the Laboratory Information System database in the Clinical Biochemistry Department. The criteria for patients' inclusion was acute brain disease and serum sodium (SNa(+)) <135 mmol/l (hyponatremia) or SNa(+) >150 mmol/l (hypernatremia). Hypoosmolality was defined as measured serum osmolality (SOsm) <275 mmol/kg, hyperosmolality as SOsm >295 mmol/kg. We performed analysis of differences between hyponatremia and hypernatremia and subanalysis of differences between hypoosmolal hyponatremia and hypernatremia. From 1,440 pts with acute brain diseases there were 251 (17 %) pts with hyponatremia (mean SNa(+) 131.78 ± 2.89 mmol/l, SOsm 279.46 ± 11.84 mmol/kg) and 75 (5 %) pts with hypernatremia (mean SNa(+) 154.38 ± 3.76 mmol/l, SOsm 326.07 ± 15.93 mmol/kg). Hypoosmolal hyponatremia occurred in 50 (20 % of hyponatremic patients) pts (mean SNa(+) 129.62 ± 4.15 mmol/l; mean SOsm 267.35 ± 6.28 mmol/kg). Multiple logistic regression analysis showed that hypernatremia is a significant predictor of mortality during neurologic-neurosurgical intensive care unit (NNICU) stay (OR 5.3, p = 0.002) but not a predictor of bad outcome upon discharge from NNICU, defined as Glasgow Coma Scale 1-3. These results showed that hypernatremia occurred less frequently than all hyponatremias, but more often than hypoosmolal hyponatremia. Hypernatremia was shown to be a significant predictor of NNICU mortality compared to hyponatremia.

Incidence and Mortality Prognosis of Dysnatremias in Neurologic Critically Ill Patients

“…We also showed that hypernatremia is an independent risk factor for ICU mortality in neurocritically ill patients. Our study provided three important contributions to the epidemiology of sodium disturbances exclusively in neurologically and critically ill patients in addition to the previously published works on neurologic/neurosurgical ICU [1,11] and TBI patients [8,16]. …”

“…In our clinical setting, the hypernatremia rate (34.1%) was much higher than those in general medical/surgical ICU (4.3-9%) [1,10,11,13,17,18], NICU (24.3% in patients with mannitol treatment) [1], and TBI patients (28.8%) [1,16], possibly because of our definition of hypernatremia (>145 mEq/l) is lower than reported (>150 mEq/l). Even so, our criteria could not account fully for such a high incidence of hypernatremia in NICU.…”

“…All subjects received standard 0.9% saline according to current guidelines at admission [11,12]. Serum sodium routinely measured by ion-selective electrodes in a Hitachi 7600 clinical analyzer (Hitachi High-Technologies Corporation, Tokyo, Japan) was used for the analysis.…”

“…Both hyponatremia and hypernatremia cause brain injury, primary in patients without brain damage and secondary in patients with various primary brain injuries. As a result of hypothalamic dysfunction or secondary to treatment with hypertonic saline in patients with brain edema [8], hypernatremia [9] is more a significant predictor of neurologic intensive care unit (NICU) mortality accompanied by metabolic alkalosis and an increase in pH [10] as compared to hyponatremia [11]. …”

“…Recently it was reported that hypernatremia (serum sodium Na + 150 mEq/l) was seen in 7.9% patients and was more common in patients with mannitol treatment (24.3%) [1]. In patients with acute brain diseases, there were 17% with hyponatremia and 5% with hypernatremia [11]. Nevertheless, serum sodium values did not correlate well with lower intracranial pressure in patients with traumatic brain injury (TBI) [14], except that severe hypernatremia was still an independent risk factor for death in NICU patients with TBI [8,15,16].…”