Diagnosis of hyponatraemia in neurointensive care: the role of renal function parameters

Czech version

Authors: V. Špatenková ¹; A. Kazda ²; P. Barsa ¹; V. .beneš ¹; P. Škrabálek ³; D. Králová ⁴; P. Suchomel ¹
Authors‘ workplace: Neurocentrum, Krajská nemocnice Liberec, a. s. ¹; Katedra klinické biochemie IPVZ, Praha ²; Oddělení klinické biochemie, Krajská nemocnice Liberec, a. s. ³; Institut biostatistiky a analýz, LF a PřF MU, Brno ⁴
Published in: Cesk Slov Neurol N 2008; 71/104(2): 156-162
Category: Original Paper

Overview

Introduction:
Hyponatraemia with hypoosmolality in acute brain diseases can be associated with two syndromes: the cerebral salt wasting syndrome (CSW) and the syndrome of inappropriate secretion of the antidiuretic hormone (CSW). Distinguishing between the two is essential as each of the syndromes requires a different therapy and is done with the use of renal function parameters. The objective of the study was to evaluate hyponatraemia after introducing the above parameters in clinical practice at our neurologic-neurosurgical care unit (NNICU).

Methods:
We retrospectively analysed all hyponatraemia (S_Na+ < 135 mmol/l) in patients (pts) with acute brain diseases admitted to our NNICU over a period of five years. First we divided them according to measured serum osmolality, and then we diagnosed the group with hypoosmolality (S_Osm < 275 mmol/kg) using renal function parameters (p-value related to normal levels).

Results:
There were 251 pts with a total of 736 days of hyponatraemia over the period under observation. The majority of pts had normal serum osmolality (155 pts, 297 days), some had hyperosmolality (38 pts, 41 days), and only 50 pts (169 days) had low plasma osmolality. Serum osmolality was not measured for the rest of hyponatraemias. In the hypoosmolal group renal function parameters were examined in 31 patients (62%). 25 patients of the above patients were diagnosed for the CSW syndrome (dU_Na+ 546.6 + 383.7 mmol/day, p < 0,001; C_El 0.065 ± 0.036 ml/s, p < 0.001; C_Na+ 0.061 ± 0.036 ml/s, p < 0.001; EWC -0.015 ± 0.032 ml/s, p = 0.030; FE_Na+ 0.029 ± 0.016, p < 0.001), 6 patients had other causes of hyponatraemia. None of the patients had SIADH.

Conclusion:
Renal function parameters represent a very easy and available method of differential diagnosis of hyponatraemias in patients receiving neurointensive care.

Key words:
hyponatraemia – hypoosmolality – CSW – SIADH – renal function parameters

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