What Causes the Acute Blood Pressure Elevation After Stroke? * Response:

What Causes the Acute Blood Pressure Elevation After Stroke? To the Editor: In an insightful editorial1 to a recently published paper by Mattle et al,2 Lindsberg raises a central question as to why blood pressure increases in the acute phase of stroke. The Cushing reflex is suggested as a possible mechanism because it results in sympathetic nervous system activation; however, this reflex is typically described as occurring in the face of raised intracranial tension.3 The purpose of this letter is to suggest that the central nervous system (CNS) ischemic response may be responsible for the marked sympathoexcitation leading to marked blood pressure elevation in acute stroke. This reflex leads to marked activation of the sympathetic nervous system and serves to eventually optimize cerebral perfusion.3 Fundamentally, the Cushing reflex and the CNS ischemic response are the same in that they are both triggered by cerebral ischemia. Cushing reflex is a variant of the CNS ischemic response because raised intracranial tension diminishes blood flow to brain cells.3 Hypoxia has been demonstrated to excite vasomotor neurons raising sympathetic outflow to blood vessels.4 Although chemoreceptors typically are described as being located in the carotid and aortic bodies and in the brain stem, there is increasing evidence that all cells are capable of metering oxygen tension and eliciting appropriate responses to optimize the supply-demand relationship that is inextricably linked to homeostasis.5