McLaughlin M R, Marion D W
Department of Neurological Surgery, Preshyterian University Hospital, University of Pittsburgh Medical Center, Pennsylvania, USA.
J Neurosurg. 1996 Nov;85(5):871-6. doi: 10.3171/jns.1996.85.5.0871.
There is increasing evidence that regional ischemia plays a major role in secondary brain injury. Although the cortex underlying subdural hematomas seems particularly vulnerable to ischemia, little is known about the adequacy of cerebral blood flow (CBF) or the vasoresponsivity within the vascular bed of contusions. The authors used the xenon-enhanced computerized tomography (CT) CBF technique to define the CBF and vasoresponsivity of contusions, pericontusional parenchyma, and the remainder of the brain 24 to 48 hours after severe closed head injury in 10 patients: six patients with one contusion and four with two contusions, defined as mixed or high-density lesions on CT scanning. The CBF within the contusions (29.3 +/- 16.4 ml/100 g/minute, mean +/- standard deviation) was significantly lower than both that found in the adjacent 1-cm perimeter of normal-appearing tissue (42.5 +/- 15.8 ml/100 g/minute) and the mean global CBF (52.5 +/- 17.5 ml/100 g/minute) (p < 0.004, repeated-measures analysis of variance). A subset of seven patients (10 contusions) also underwent a second Xe-CT CBF study during mild hyperventilation (a PaCO2 of 24-32 mm Hg). In only two of these 10 contusions was vasoresponsivity less than 1% (range 0%-7.6%); in the rim of normal-appearing pericontusional tissue, it was 0.4% to 9.1%. The authors conclude that CBF within intracerebral contusions is highly variable and is often above 18 ml/100 g/minute, the reported threshold for irreversible ischemia. Intracontusional CBF is significantly reduced relative to surrounding brain parenchyma, and CO2 vasoresponsivity is usually present. In the contusion and the surrounding parenchyma, vasoresponsivity may be nearly three times normal, suggesting hypersensitivity to hyperventilation therapy. Given this possible hypersensitivity and relative hypoperfusion within and around cerebral contusions, these lesions are particularly vulnerable to secondary injury such as that which may be caused by hypotension or aggressive hyperventilation.
越来越多的证据表明，局部缺血在继发性脑损伤中起主要作用。虽然硬膜下血肿下方的皮质似乎特别容易发生缺血，但对于脑挫裂伤血管床内的脑血流量（CBF）充足性或血管反应性却知之甚少。作者使用氙增强计算机断层扫描（CT）CBF技术，对10例严重闭合性颅脑损伤后24至48小时的脑挫裂伤、挫伤周围实质和脑的其余部分的CBF和血管反应性进行了测定：6例有一处脑挫裂伤，4例有两处脑挫裂伤，在CT扫描上表现为混合性或高密度病变。脑挫裂伤内的CBF（29.3±16.4ml/100g/分钟，平均值±标准差）显著低于正常外观组织相邻1cm范围内的CBF（42.5±15.8ml/100g/分钟）和平均全脑CBF（52.5±17.5ml/100g/分钟）（p<0.004，重复测量方差分析）。7例患者（10处脑挫裂伤）的一个亚组在轻度过度通气（动脉血二氧化碳分压为24 - 32mmHg）期间还进行了第二次氙CT CBF研究。在这10处脑挫裂伤中，只有2处的血管反应性小于1%（范围为0% - 7.6%）；在正常外观的挫伤周围组织边缘，血管反应性为0.4%至9.1%。作者得出结论，脑内挫裂伤内的CBF变化很大，且通常高于18ml/100g/分钟，即报道的不可逆缺血阈值。与周围脑实质相比，挫裂伤内的CBF显著降低，且通常存在二氧化碳血管反应性。在挫裂伤及其周围实质中，血管反应性可能接近正常的三倍，提示对过度通气治疗过敏。鉴于脑挫裂伤内及其周围可能存在这种过敏反应和相对灌注不足，这些病变特别容易受到继发性损伤，如低血压或积极过度通气可能导致的损伤。
