Chovanes George I, Richards Rafael M
Division of Neurosurgery, Paoli Hospital, 15 Industrial Blvd., Paoli, PA 19301, USA.
Surg Neurol Int. 2012;3:12. doi: 10.4103/2152-7806.92185. Epub 2012 Jan 21.
The influence of cerebral perfusion pressure (CPP) on real-time focal cerebral blood flow (fCBF) is not fully understood, in either intact or injured brain. We wanted to evaluate that relationship, and by implication investigate the relative importance of perfusion pressure versus metabolism in the regulation and control of cerebral blood flow. Our hypothesis was that metabolic needs dominated over a physiologic range of blood pressure.
This was an observational study of 23 patients, most of them with closed head injury, three with subarachnoid hemorrhage, one with a gunshot wound to the brain, and one monitored after craniotomy for unruptured aneurysm. Arterial lines, ventriculostomies, and fCBF monitors were placed. CPP (mean arterial pressure - intracranial pressure) and fCBF were measured and recorded to a computer database every minute. The relationship between CPP and fCBF was graphed and correlation coefficients were compared between survivors and non-survivors.
Graphs of CPP versus fCBF did not show any linearity over a range of 50-150 mm Hg in patients who survived. In those who died, four of seven showed some indication of linearity. The difference in the correlation coefficients between survivors and non-survivors was statistically significant (P < 0.05), with survivors having essentially no correlation, as expected with autoregulation intact, and non-survivors having a mean correlation of 0.311.
In the functioning and viable brain, metabolic regulation of cerebral blood flow (CBF) predominates, leading to the lack of an obvious relationship between perfusion pressure and flow. This predominance of metabolic regulation is robust and preserved over a wide range of brain injury, with pressure autoregulation necessary but not clinically apparent in the metabolically active brain. This robust and constantly varying relationship of pressure and flow shown by our real-time measurements of fCBF has important implications for interpreting clinical measurements of autoregulation. Perhaps most importantly, the development of a correlation between pressure and flow may indicate and be an early warning of deterioration.
无论是在完整的还是受损的大脑中，脑灌注压（CPP）对实时局部脑血流量（fCBF）的影响尚未完全明确。我们希望评估这种关系，并由此探究灌注压与代谢在脑血流量调节与控制中的相对重要性。我们的假设是，在生理血压范围内，代谢需求起主导作用。
这是一项对23例患者的观察性研究，其中大多数为闭合性颅脑损伤患者，3例为蛛网膜下腔出血患者，1例为脑枪伤患者，1例为未破裂动脉瘤开颅术后监测患者。放置了动脉导管、脑室造瘘管和fCBF监测仪。每分钟测量CPP（平均动脉压 - 颅内压）和fCBF，并记录到计算机数据库中。绘制CPP与fCBF之间的关系图，并比较幸存者和非幸存者之间的相关系数。
存活患者的CPP与fCBF关系图在50 - 150 mmHg范围内未显示出任何线性关系。在死亡患者中，7例中有4例显示出一定的线性迹象。幸存者和非幸存者之间的相关系数差异具有统计学意义（P < 0.05），幸存者基本无相关性，这与自动调节功能完好时预期的情况一致，而非幸存者的平均相关系数为0.311。
在功能正常且存活的大脑中，脑血流量（CBF）的代谢调节占主导地位，导致灌注压与血流量之间缺乏明显关系。这种代谢调节的主导地位在广泛的脑损伤范围内都很稳固且得以保留，压力自动调节虽有必要，但在代谢活跃的大脑中临床上并不明显。我们通过fCBF实时测量所显示的压力与血流量之间这种稳固且不断变化的关系，对于解释自动调节的临床测量结果具有重要意义。也许最重要的是，压力与血流量之间相关性的出现可能预示并是病情恶化的早期预警。
