Grant Daniel A, Franzini Carlo, Wild Jennene, Eede Kellie J, Walker Adrian M
Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash Medical Centre, 246 Clayton Road, Clayton, Melbourne, Victoria, 3168, Australia.
J Physiol. 2005 May 1;564(Pt 3):923-30. doi: 10.1113/jphysiol.2005.083352. Epub 2005 Mar 10.
Autoregulation is a vital protective mechanism that maintains stable cerebral blood flow as cerebral perfusion pressure changes. We contrasted cerebral autoregulation across sleep-wake states, as little is known about its effectiveness during sleep. Newborn lambs (n= 9) were instrumented to measure cerebral blood flow (flow probe on the superior sagittal sinus) and cerebral perfusion pressure, then studied during active sleep (AS), quiet sleep (QS) and quiet wakefulness (QW). We generated cerebral autoregulation curves by inflating an occluder cuff around the brachiocephalic artery thereby lowering cerebral perfusion pressure. Baseline cerebral blood flow was higher (P < 0.05) and cerebral vascular resistance lower (P < 0.05) in AS than in QW (76 +/- 8% and 133 +/- 15%, respectively, of the AS value, mean +/-s.d.) and in QS (66 +/- 11% and 158 +/- 30%). The autoregulation curve in AS differed from that in QS and QW in three key respects: firstly, the plateau was elevated relative to QS and QW (P < 0.05); secondly, the lower limit of the curve (breakpoint) was higher (P < 0.05) in AS (50 mmHg) than QS (45 mmHg); and thirdly, the slope of the descending limb below the breakpoint was greater (P < 0.05) in AS than QS (56% of AS) or QW (56% of AS). Although autoregulation functions in AS, the higher breakpoint and greater slope of the descending limb may place the brain at risk for vascular compromise should hypotension occur.
自动调节是一种重要的保护机制，可在脑灌注压变化时维持稳定的脑血流量。我们对比了睡眠-觉醒状态下的脑自动调节情况，因为目前对其在睡眠期间的有效性了解甚少。对9只新生羔羊进行仪器植入以测量脑血流量（上矢状窦上的血流探头）和脑灌注压，然后在主动睡眠（AS）、安静睡眠（QS）和安静觉醒（QW）期间进行研究。我们通过在头臂动脉周围充气阻塞袖带从而降低脑灌注压来生成脑自动调节曲线。与QW相比，AS时的基线脑血流量更高（P<0.05），脑血管阻力更低（P<0.05）（分别为AS值的76±8%和133±15%，平均值±标准差），与QS相比也是如此（分别为66±11%和158±30%）。AS时的自动调节曲线在三个关键方面与QS和QW时不同：首先，相对于QS和QW，其平台期升高（P<0.05）；其次，AS时曲线的下限（断点）更高（P<0.05）（50 mmHg），高于QS时（45 mmHg）；第三，AS时断点以下下降支的斜率大于QS时（AS的56%）或QW时（AS的56%）（P<0.05）。虽然自动调节在AS中起作用，但下降支较高的断点和更大的斜率可能使大脑在发生低血压时面临血管受损的风险。
