Greene Stephen A
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-6610, USA.
Top Companion Anim Med. 2010 May;25(2):83-6. doi: 10.1053/j.tcam.2009.12.001.
Cerebral blood flow may be altered in anesthetized patients, and this could be detrimental to patients with intracranial disease. Cerebral blood flow is autoregulated and held constant over a mean arterial pressure range of 50 to 150 mm Hg. Changes in cerebral blood volume are reflected by cerebral blood flow, whereas intracranial pressure varies directly with cerebral blood volume. Cerebral blood flow is also under chemical regulation and varies directly with arterial carbon dioxide tension over the range of 25 to 70 mm Hg. A reduction in arterial oxygen tension to below 60 mm Hg also dramatically increases cerebral blood flow. Changes in both arterial carbon dioxide and oxygen tensions are common in anesthetized patients. Furthermore, anesthetic drugs can alter cerebral blood flow. Injectable anesthetics, except ketamine, tend to preserve cerebral blood flow. Inhalant anesthetics may be associated with cerebral vasodilation, increased cerebral blood flow, and raised intracranial pressure. However, low concentrations of inhalant anesthetics combined with controlled ventilation are effective in preventing exacerbation of raised intracranial pressure. Factors affecting cerebral blood flow should be considered before anesthetizing patients with intracranial disease.
在麻醉患者中，脑血流量可能会发生改变，这对患有颅内疾病的患者可能是有害的。脑血流量受到自动调节，在平均动脉压50至150毫米汞柱的范围内保持恒定。脑血容量的变化由脑血流量反映，而颅内压则与脑血容量直接相关。脑血流量也受化学调节，在25至70毫米汞柱的范围内与动脉二氧化碳分压直接相关。动脉血氧分压降至60毫米汞柱以下也会显著增加脑血流量。在麻醉患者中，动脉二氧化碳和氧分压的变化都很常见。此外，麻醉药物会改变脑血流量。除氯胺酮外，注射用麻醉剂往往能维持脑血流量。吸入性麻醉剂可能与脑血管扩张、脑血流量增加和颅内压升高有关。然而，低浓度的吸入性麻醉剂与控制通气相结合可有效预防颅内压升高的加重。在对患有颅内疾病的患者进行麻醉之前，应考虑影响脑血流量的因素。
