McCulloch Timothy J, Thompson Christopher L, Turner Martin J
Department of Anaesthetics, University of Sydney, Sydney, and Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia.
Anesthesiology. 2007 Jan;106(1):56-64. doi: 10.1097/00000542-200701000-00012.
Intravenous and inhalational anesthetic agents have differing effects on cerebral hemodynamics: Sevoflurane causes some vasodilation, whereas propofol does not. The authors hypothesized that these differences affect internal carotid artery pressure (ICAP) and the apparent zero flow pressure (critical closing pressure) during carotid endarterectomy. Vasodilation is expected to increase blood flow, reduce ICAP, and reduce apparent zero flow pressure.
In a randomized crossover study, the gradient between systemic arterial pressure and ICAP during carotid clamping was measured while changing between sevoflurane and propofol in 32 patients. Middle cerebral artery blood velocity, recorded by transcranial Doppler, and ICAP waveforms were analyzed to determine the apparent zero flow pressure.
ICAP increased when changing from sevoflurane to propofol, causing the mean gradient between arterial pressure and ICAP to decrease by 10 mmHg (95% confidence interval, 6-14 mmHg; P<0.0001). Changing from propofol to sevoflurane had the opposite effect: The pressure gradient increased by 5 mmHg (95% confidence interval, 2-7 mmHg; P=0.002). Ipsilateral middle cerebral artery blood velocity decreased when changing from sevoflurane to propofol. Cerebral steal was detected in one patient after changing from propofol to sevoflurane. The apparent zero flow pressure (mean+/-SD) was 22+/-10 mmHg with sevoflurane and 30+/-14 mmHg with propofol (P<0.01). There was incomplete drug crossover due to the limited duration of carotid clamping.
Compared with sevoflurane, ipsilateral ICAP and apparent zero flow pressure are both higher with propofol. Vasodilatation associated with sevoflurane can cause cerebral steal.
静脉麻醉药和吸入麻醉药对脑血流动力学有不同影响：七氟醚会引起一定程度的血管舒张，而丙泊酚则不会。作者推测这些差异会影响颈动脉内膜切除术期间的颈内动脉压力（ICAP）和表观零流量压力（临界关闭压力）。血管舒张预计会增加血流量、降低ICAP并降低表观零流量压力。
在一项随机交叉研究中，对32例患者在七氟醚和丙泊酚之间切换时夹闭颈动脉期间的体动脉压与ICAP之间的梯度进行了测量。通过经颅多普勒记录大脑中动脉血流速度，并分析ICAP波形以确定表观零流量压力。
从七氟醚改为丙泊酚时，ICAP升高，导致动脉压与ICAP之间的平均梯度降低10 mmHg（95%置信区间，6 - 14 mmHg；P<0.0001）。从丙泊酚改为七氟醚则产生相反的效果：压力梯度增加5 mmHg（95%置信区间，2 - 7 mmHg；P = 0.002）。从七氟醚改为丙泊酚时，同侧大脑中动脉血流速度降低。从丙泊酚改为七氟醚后，在一名患者中检测到脑盗血现象。七氟醚时的表观零流量压力（均值±标准差）为22±10 mmHg，丙泊酚时为30±14 mmHg（P<0.01）。由于颈动脉夹闭持续时间有限，药物交叉不完全。
与七氟醚相比，丙泊酚使同侧ICAP和表观零流量压力均更高。七氟醚相关的血管舒张可导致脑盗血。
