RESUMO
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.
RESUMO
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.
RESUMO
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.