What is a key laboratory finding associated with subarachnoid hemorrhage?

Subarachnoid hemorrhage (SAH) is characterized by bleeding into the subarachnoid space, often resulting from the rupture of an aneurysm. One of the key laboratory findings associated with SAH is an increase in antidiuretic hormone (ADH), also known as vasopressin.

When a person experiences SAH, there is a neuroendocrine response that leads to the release of ADH. This response is thought to be due to the stress and trauma on the brain, as well as alterations in cerebral blood flow and osmolarity. Increased levels of ADH can lead to delayed renal excretion of water, causing dilutional hyponatremia in the affected individual.

Other laboratory findings typically do not correspond with SAH. For instance, elevated glucose levels are not characteristic of SAH; instead, in cases of hemorrhagic stroke, the glucose levels may remain normal or only mildly elevated. Similarly, decreased levels of BNP (B-type natriuretic peptide) and decreased protein levels would not be expected in this context, as these findings are more associated with other conditions like heart failure or certain renal issues, rather than with subarachnoid hemorrhage.

The increase in ADH