Tran-Dinh A, Depret F, Vigué B
Département d'anesthésie-réanimation, CHU de Bicêtre, AP-HP, 94275 Le Kremlin-Bicêtre, France.
Ann Fr Anesth Reanim. 2012 Jun;31(6):e137-43. doi: 10.1016/j.annfar.2012.04.018. Epub 2012 Jun 13.
The main purpose of neurointensive care is to fight against cerebral ischaemia. Ischaemia is the cell energy failure following inadequacy between supply of glucose and oxygen and demand. Ischemia monitoring starts with a global approach, especially with cerebral perfusion pressure (CPP) determined by mean arterial pressure and intracranial pressure (ICP). However, global monitoring is insufficient to detect "regional" ischaemia, leading to development of local monitoring such as brain oxygen partial pressure (PtiO(2)). PtiO(2) is measured on a volume of a few mm(3) from a probe implanted in the cerebral tissue. The normal value is classically included between 25 and 35 mmHg and critical ischemic threshold is 10 mmHg. Understanding what exactly is PtiO(2) is still a matter of debate. PtiO(2) is more an indicator of oxygen diffusion depending of oxygen arterial pressure (PaO(2)) and local cerebral blood flow (CBF). Increase PaO(2) to treat PtiO(2) would hide information about local CBF. PtiO(2) is useful for the detection of low local CBF even when ICP is low as in hypocapnia-induced vasoconstriction. PtiO(2)-guided management could lead to a continuous optimization of arterial oxygen transport for an optimal cerebral tissue oxygenation. Finally, PtiO(2) has probably a global prognostic value because studies showed that hypoxic values for a long period of time lead to an unfavourable neurologic outcome. In conclusion, PtiO(2) provides additional information for regional monitoring of cerebral ischaemia and deserves more intensive use to better understand it and probably improve neurointensive care management.
神经重症监护的主要目的是对抗脑缺血。缺血是指葡萄糖和氧气供应与需求之间失衡后导致的细胞能量衰竭。缺血监测始于整体评估方法，尤其是通过平均动脉压和颅内压（ICP）来确定脑灌注压（CPP）。然而，整体监测不足以检测到“局部”缺血，因此催生了局部监测手段，如脑氧分压（PtiO₂）监测。PtiO₂通过植入脑组织中的探头在几立方毫米的体积内进行测量。其正常值通常在25至35mmHg之间，临界缺血阈值为10mmHg。关于PtiO₂究竟是什么仍存在争议。PtiO₂更多地是一种取决于动脉血氧分压（PaO₂）和局部脑血流量（CBF）的氧扩散指标。通过提高PaO₂来治疗PtiO₂会掩盖有关局部CBF的信息。即使在ICP较低的情况下，如在低碳酸血症引起的血管收缩时，PtiO₂对于检测局部低CBF也很有用。以PtiO₂为指导的管理可实现动脉氧输送的持续优化，以达到最佳的脑组织氧合。最后，PtiO₂可能具有整体预后价值，因为研究表明，长时间的低氧值会导致不良的神经学预后。总之，PtiO₂为脑缺血的局部监测提供了额外信息，值得更深入地利用，以便更好地理解它，并可能改善神经重症监护管理。
