Endocrine Abstracts (2005) 9 P117

The incidence and pathophysiology of hyponatraemia after subarachnoid haemorrhage

M Sherlock1, E O'Sullivan1, A Agha1, LA Behan1, D Rawluk2, P Brennan3 & CJ Thompson1

1Academic Department of Endocrinology, Beaumont Hospital, Dublin, Ireland; 2Department of Neurosurgery, Beaumont Hospital, Dublin, Ireland; 3Department of Neuroradiology, Beaumont Hospital, Dublin, Ireland.

Hyponatraemia occurs in 25-40% of patients with subarachnoid haemorrhage (SAH) but the pathogenesis is unclear.

Objective: We aimed to establish the incidence, pathophysiology and consequences of hyponatraemia following SAH.

Methods: A retrospective case note analysis of all patients with radiologically-proven SAH admitted to Beaumont Hospital between Jan 2002 and September 2003. Of 580 patients coded as SAH on HIPE records, 316 were substantiated by CT scan and angiogram findings. Hyponatraemia was defined as plasma sodium < 135 milli-mol per litre. SIADH was defined by the criteria of Verbalis (1996) and cerebral salt wasting(CSW) by the criteria of Smith et al (1999).

Results: 179 patients (56.6%) developed hyponatraemia and 62 (19.6%) developed significant hyponatraemia (plasma sodium < 130 milli-mol per litre). Hyponatraemia was commoner in patients with identified aneurysms (anterior circulation 102/168, 60.7%, posterior circulation 56/95, 60.8%) than in those with no radiological aneurysm (21/54, 38.8%, p < 0.001). Hyponatraemia was also commoner after aneurysmal clipping (68/103, 66%) or coiling (82/132, 62%) than in those treated conservatively (29/81, 36%, p < 0.001). The aetiology of significant hyponatraemia was SIADH 39/62 (69.2%), CSW 4/62 (6.5%), hypovolaemic hyponatraemia 13/62 (21%) and hypervolaemic hyponatraemia 3/62 (4.8%), mixed CSW/SIADH 3/62 (4.8%). Hyponatraemia was associated with longer hospital stay (Mean (SD) 24.0 (2.6) vs 11.8 (0.8) days, p < 0.001) but did not affect mortality (p = 0.07).

Conclusions: Hyponatraemia is common following SAH and predicts longer hospital stay. Clipping and coiling are associated with higher rates of hyponatraemia. SIADH is the commonest cause of hyponatraemia after SAH.

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