Background and Goal of Study: Serum brain natriuretic peptide (BNP) is elevated after subarachnoid haemorrhage (SAH). This rise could be related to the occurrence of hyponatraemia, or delayed ischaemic neurological deficit (DIND), or indeed both. There are two mechanisms that have been proposed as possible causes of this correlation, cerebral salt wasting syndrome (CSWS) or the syndrome of inappropriate antidiuretic hormone secretion (SIADH).
This study aimed to correlate changes in serum BNP with hyponatraemia and DIND after SAH.
Materials and Methods: A prospective study was carried out on 30 adult patients presenting with aneurysmal SAH, who were admitted to the Neurosurgical Intensive Care Unit at Alexandria University Hospital. Serum NT-proBNP and serum sodium (Na) levels were measured over the 14 days post SAH onset. The 14 days were subdivided into 4 observational periods. DIND onset was plotted against both NT-proBNP and Na. Statistical analysis was performed using Spearmann's rank correlation and the Mann Whitney U test.
Results and Discussion: NT-proBNP median levels dropped from the first observational period until the fourth. Serum Na showed no significant difference among the 4 observational periods.
In the second observational period 10 patients (34.5%) developed a more marked hyponatraemia than those recorded in other periods. A significant correlation between serum Na and NT-proBNP was observed only in the 4th observational period (r=-0.43, p=0.03). This correlation was not significant for any other observational period. 
DIND occurrence was 40%. The median serum Na levels among DIND cases was lower than that for cases without DIND. (134.6 (133.6-135.8), 137.7 (137.2-139.7) respectively. These differences were statistically significant (Z=-3.28, p=0.001). Regarding serum NT-proBNP, DIND cases had a median of 841.6 pg/ml while the cases without DIND showed a median of 406.5 pg/ml. There was no statistical difference (Z=-1.61, p=0.11).
Conclusions: This study showed a positive correlation between serum Na levels and DIND status (r=0.67, p<0.001). There was not significant correlation between DIND status and serum NT-proBNP levels (r=0.33, p=0.11).
 


01 / Correlation between B-type natriuretic peptide with hyponatraemia and delayed ischaemic neurological deficit after subarachnoid haemorrhage