Yundt K D, Grubb R L, Diringer M N, Powers W J
Department of Neurology and Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.
Neurosurgery. 1997 Mar;40(3):442-50; discussion 450-1. doi: 10.1097/00006123-199703000-00003.
The cerebral hemodynamic and metabolic effects of aneurysmal subarachnoid hemorrhage are complex. To investigate the impact of surgical retraction, we analyzed position emission tomography (PET) studies that measured the regional cerebral metabolic rate for oxygen, regional oxygen extraction fraction, and regional cerebral blood flow in four patients before and after right frontotemporal craniotomies for clipping of ruptured anterior circulation aneurysms.
Preoperative studies were conducted 1 day before surgery and postoperative studies 6 to 17 days after surgery. No patient had hydrocephalus or intracerebral hematoma. At the time of the second PET study, none of the patients had signs of clinical vasospasm. Regional measurements were obtained from the right ventrolateral frontal and anterior temporal regions corresponding to the area of retraction and compared to the same regions in the opposite hemisphere. To establish a quantitative means to differentiate between hemodynamic and metabolic changes related to arterial vasospasm and those caused by brain retraction, we studied a second group of preoperative patients, who had undergone PET during angiographic and clinical vasospasm.
There was a 45% reduction in regional cerebral metabolic rate for oxygen (1.87 +/- 0.22 to 1.04 +/- 0.28 ml 100 g-1 min-1) and 32% reduction in regional oxygen extraction fraction (0.41 +/- 0.04 to 0.28 +/- 0.03) in the region of retraction but no change in the opposite hemisphere (paired t test; P = 0.042 and 0.003, respectively). There was no change in regional cerebral blood flow in any region. Brain retraction produced a focal area of tissue injury at the site of retractor blade placement, as compared to more diffuse vascular territory changes produced by vasospasm.
This reduction in the cerebral metabolic rate of oxygen and the oxygen extraction fraction indicates a primary reduction in metabolism and uncoupling of flow and metabolism (luxury perfusion). Similar findings of luxury perfusion have been reported after ischemic stroke and traumatic brain injury. Further studies will be necessary to fully understand the clinical and pathophysiological significance of these observations.
动脉瘤性蛛网膜下腔出血对脑血流动力学和代谢的影响较为复杂。为研究手术牵拉的影响，我们分析了正电子发射断层扫描（PET）研究，该研究测量了4例因破裂的前循环动脉瘤行右额颞开颅夹闭术患者术前和术后的局部脑氧代谢率、局部氧摄取分数和局部脑血流量。
术前研究在手术前1天进行，术后研究在术后6至17天进行。所有患者均无脑积水或脑内血肿。在第二次PET研究时，所有患者均无临床血管痉挛迹象。从与牵拉区域相对应的右侧腹外侧额叶和颞前区域获取局部测量值，并与对侧半球的相同区域进行比较。为建立一种定量方法来区分与动脉血管痉挛相关的血流动力学和代谢变化以及由脑牵拉引起的变化，我们研究了另一组术前患者，这些患者在血管造影和临床血管痉挛期间接受了PET检查。
牵拉区域的局部脑氧代谢率降低了45%（从1.87±0.22降至1.04±0.28 ml·100 g-1·min-1），局部氧摄取分数降低了32%（从0.41±0.04降至0.28±0.03），而对侧半球无变化（配对t检验；P分别为0.042和0.003）。任何区域的局部脑血流量均无变化。与血管痉挛引起的更弥漫的血管区域变化相比，脑牵拉在牵开器叶片放置部位产生了局部组织损伤区域。
脑氧代谢率和氧摄取分数的降低表明代谢的原发性降低以及血流与代谢的解偶联（奢侈灌注）。缺血性卒中和创伤性脑损伤后也报道了类似的奢侈灌注发现。需要进一步研究以充分了解这些观察结果的临床和病理生理意义。
