Academic Neurosurgical Unit, Department of Clinical Neuroscience, University of Cambridge, Cambridge CB2 2QQ, UK.
Anesth Analg. 2010 Jan 1;110(1):165-73. doi: 10.1213/ANE.0b013e3181c0722f. Epub 2009 Nov 21.
The relative merits of the mechanisms for the maintenance of brain tissue oxygenation (PbtO(2)) have been much debated. There is a wealth of studies regarding various factors that may determine the absolute value and changes in PbtO(2). However, only a few of them analyzed fast (few minutes) and transient behavior of PbtO(2) in response to variations (waves) of intracranial pressure (ICP) and cerebral perfusion pressure (CPP).
This was a retrospective analysis and observational study. PbtO(2), arterial blood pressure (ABP), and ICP waveforms were digitally monitored in 23 head-injured patients, admitted to the Neuroscience Critical Care Unit, who were sedated, paralyzed, and ventilated. Computer recordings were retrospectively reviewed. The dynamic changes in PbtO(2) in response to transient changes in ABP and ICP were investigated.
Several patterns of response to short-lasting arterial hypotension and hypertension, intracranial hypertension, cerebral vasocycling, and cerebral hyperemia were observed and characterized. During the majority of the transient events, PbtO(2) generally followed the direction of changes in CPP. Only during episodes of hyperemia, CPP and PbtO(2) changed in the opposite direction. Changes in PbtO(2) were delayed after dynamic changes in ABP, CPP, and ICP. The CPP-PbtO(2) delay during changes provoked by variations in ABP was 35.0 s (range: maximum 827.0 s; minimum 0.0 s) compared with changes induced by variations in ICP of 0.0 s (range: maximum 265.0 s; minimum 0.0 s); the difference was significant at P < 0.0001.
PbtO(2) is more than a number; it is rather a waveform following rapid changes in ICP and ABP. We show that PbtO(2) generally tracks the direction of CPP irrespective of the state of cerebral autoregulation.
关于维持脑组织氧合（PbtO2）的机制的相对优点，已经进行了广泛的讨论。有大量关于各种因素的研究，这些因素可能决定 PbtO2 的绝对值和变化。然而，只有少数研究分析了 PbtO2 对颅内压（ICP）和脑灌注压（CPP）变化（波）的快速（几分钟内）和瞬态反应。
这是一项回顾性分析和观察性研究。对 23 例入住神经重症监护病房的颅脑损伤患者的 PbtO2、动脉血压（ABP）和 ICP 波形进行数字监测，这些患者接受镇静、麻痹和通气。回顾性审查计算机记录。研究了 PbtO2 对 ABP 和 ICP 短暂变化的动态反应。
观察并描述了对短暂性动脉低血压和高血压、颅内高压、脑血管循环和脑充血的几种反应模式。在大多数短暂性事件中，PbtO2 通常遵循 CPP 变化的方向。只有在充血期，CPP 和 PbtO2 才会朝相反的方向变化。PbtO2 的变化滞后于 ABP、CPP 和 ICP 的动态变化。在由 ABP 变化引起的变化中，CPP-PbtO2 延迟为 35.0 秒（范围：最大值 827.0 秒；最小值 0.0 秒），而由 ICP 变化引起的变化延迟为 0.0 秒（范围：最大值 265.0 秒；最小值 0.0 秒）；差异有统计学意义（P < 0.0001）。
PbtO2 不仅仅是一个数字，它还是一个跟随 ICP 和 ABP 快速变化的波形。我们表明，PbtO2 通常跟踪 CPP 的方向，而与脑自动调节的状态无关。
