Ameriso S F, Mohler J G, Suarez M, Fisher M
Department of Neurology, University of Southern California School of Medicine, Los Angeles 90033.
Neurology. 1994 Oct;44(10):1907-9. doi: 10.1212/wnl.44.10.1907.
We measured cerebral vasomotor reactivity during normoventilation, hyperventilation (hypocapnia), and breathing of 6% CO2 (hypercapnia) in 20 normal subjects during the hours of 6 to 8 AM, 1 to 3 PM, and 7 to 9 PM. Cerebral vasomotor reactivity was calculated, using transcranial Doppler, as percent change in the mean blood flow velocity of the middle cerebral artery per mm Hg change in end-tidal CO2 during hypocapnia and hypercapnia. Vasomotor reactivity during hypercapnia was lower in the morning (1.72 +/- 0.66 %/mm Hg) than in the afternoon (2.34 +/- 0.74 %/mm Hg, p < 0.01) and evening (2.31 +/- 0.56 %/mm Hg, p < 0.001). Vasomotor reactivity during hypocapnia did not vary significantly during the three periods (2.34 +/- 0.59 %/mm Hg in the morning, 2.43 +/- 0.51 %/mm Hg in the afternoon, and 2.26 +/- 0.52 %/mm Hg in the evening). This reduced morning response to hypercapnia suggests diminished vasodilator reserve during this period, and may be related to the increased stroke risk during the morning hours.
我们在上午6点至8点、下午1点至3点以及晚上7点至9点这几个时间段，对20名正常受试者在正常通气、过度通气（低碳酸血症）以及吸入6%二氧化碳（高碳酸血症）过程中的脑血管舒缩反应性进行了测量。使用经颅多普勒计算脑血管舒缩反应性，即低碳酸血症和高碳酸血症期间，每毫米汞柱终末潮气二氧化碳变化时大脑中动脉平均血流速度的百分比变化。高碳酸血症期间的舒缩反应性在早晨（1.72±0.66%/毫米汞柱）低于下午（2.34±0.74%/毫米汞柱，p<0.01）和晚上（2.31±0.56%/毫米汞柱，p<0.001）。低碳酸血症期间的舒缩反应性在这三个时间段内无显著差异（早晨为2.34±0.59%/毫米汞柱，下午为2.43±0.51%/毫米汞柱，晚上为2.26±0.52%/毫米汞柱）。早晨对高碳酸血症反应的降低表明在此期间血管舒张储备减少，这可能与早晨时段中风风险增加有关。
