FUNCTIONAL-CHANGES IN HUMAN PIAL-ARTERIES (300 TO 900 MU-M ID) WITHIN48 HOURS OF ANEURYSMAL SUBARACHNOID HEMORRHAGE

Background and Purpose-Animal studies of cerebral arteries 2 to 3 days after experimental subarachnoid hemorrhage (SAH) provide evidence of arterial change such as hyperresponsiveness to contractile agonists. T here is evidence that small arteries, as well as those large enough to be seen on angiography, may be involved. To directly test these possi bilities, the contractile and dilator responses of pial artery segment s taken from patients up to 48 hours after SAH were compared with thos e from patients having elective surgery for an aneurysm (Clip) and wit h those from normal brain vessels overlying tumors (controls). Methods -Segments were mounted on a resistance artery myograph for measurement s of wall force changes. Results-There were no differences in maximum contractility (E-max) of the 3 groups of segments. The responses of th e SAH segments to K+ (30 mmol/L) were 60.7+/-4.6% of E-max (n [number of vessels] = 18), which was significantly greater than those of contr ols (29.9+/-5% E-max) (n=20). Clip responses were the same as control. Contractions of SAH segments to norepinephrine (1 mu mol/L) were 54.3 +/-7.9% E-max (n= 12), and these were significantly greater than thos e of controls (15.1 +/- 6.2% E-max) (n= 25). All SAH segments showed s pontaneous contractile activity of varying patterns. Spontaneous activ ity did not occur in the Clip group and occurred in only 50% of contro l segments. Dilation to acetylcholine was numerically less in SAH and Clip segments than in controls, but differences were not statistically significant. The change in agonist responsiveness could result from e xposure to agents that damage the blood vessel wall, resulting in part ial depolarization of endothelial and smooth muscle cells. Conclusions -Small human pial arteries are hyperresponsive to contractile agents a nd show spontaneous contractile activity within 48 hours of SAH. Such effects could result in narrowed resistance arteries and reduction in cerebral blood flow. These effects emphasize the wisdom of early thera peutic intervention.