The effect of subarachnoid epinephrine and phenylephrine on spinal cord blood flow.

Eighteen mongrel dogs were divided into three equal groups. Spinal cord and spinal dural blood flow in the cervical, thoracic and lumbosacral regions were measured using the radioactive microsphere technique. Measurements were taken before and 10 and 40 minutes after lumbar subarachnoid injection of one of the following: physiologic saline; epinephrine 200 micrograms or phenylephrine 5 mg. No significant change in spinal cord blood flow occurred in any of the groups, nor was there any difference between the groups. Dogs receiving subarachnoid phenylephrine did demonstrate a significant reduction of thoracic dural blood flow at ten minutes. Dogs receiving intrathecal epinephrine or phenylephrine demonstrated a significant reduction in lumbo-sacral dural blood flow at ten minutes after injection. The reduction in dural blood flow was still evident at 40 minutes in dogs receiving phenylephrine. Subarachnoid epinephrine (200 micrograms) and phenylephrine (5 mg) do not effect spinal cord blood flow but do produce regional dural vasoconstriction.