Objective
Cerebral artery vasospasm is a major
cause of death and disability in
patients experiencing
subarachnoid hemorrhage (SAH). Vasospasm typically has been evaluated using
angiography to examine narrowing of large diameter (>1 mm)
cerebral arteries. Currently, little is known regarding the impact of SAH on small diameter (100~200 μm)
cerebral arteries, which
play an important
role in the
autoregulation of
cerebral blood flow. The
goal of the current study was to examine the influence of SAH on the
pressure-diameter relationship of these small diameter
blood vessels.
Methods Small diameter
cerebral arteries were obtained from a
rabbit SAH model. Isolated
artery segments were canulated and placed in a myograph chamber superfused with warmed, oxygenated, physiological
saline solution. Diameter measurements were then recorded to step-wise increases in intravascular
pressure. Results
Cerebral arteries from SAH
animals exhibited a significant increase in
pressure-induced
constrictions (myogenic tone) at intravascular
pressures between 40 mmHg and 120 mmHg. At intravascular
pressures above 120 mmHg, myogenic tone began to decrease and was abolished at
pressures above 180 mmHg. Conclusion These data suggest that in the days following SAH, myogenic tone is enhanced in small diameter
cerebral arteries subjected to physiological levels of intravascular
pressure. However, supra-physiological intravascular
pressures causes
vasodilation, suggesting small diameter
cerebral arteries may act as
therapeutic targets of hypervolemia,
hemodilution, and
hypertension "Triple H
therapy" used in the
treatment of
cerebral artery vasospasm.