Cerebral Blood Flow Responses to Autonomic Dysreflexia in Humans with Spinal Cord Injury.

Autonomic dysreflexia (AD) is a life-threatening episode of transient hypertension affecting up to 90% of those with high-level spinal cord injury (SCI), and can lead to cerebral hemorrhage. Due to the nature of this medical emergency, cerebral blood flow (CBF) has not been recorded during AD. Beat-by-beat blood pressure (BP) and CBF velocity of the middle cerebral artery were measured during spontaneous AD episodes in four motor complete cervical SCI patients. Mean arterial BP increased during AD (66 ± 11 vs. 83 ± 10 mm Hg; p = 0.004), whereas CBF (76 ± 4 vs. 74 ± 4 cm · sec(-1)) and end-tidal partial pressure of carbon dioxide (PETCO2) (35 ± 1 vs. 34 ± 3 mm Hg) were maintained. These preliminary data indicate that the brain may effectively buffer moderate episodes of AD.