Jones S C, Williams J L, Shea M, Easley K A, Wei D
Department of Neurosciences, Cleveland Clinic Foundation, Ohio 44195.
Am J Physiol. 1995 Feb;268(2 Pt 2):H569-75. doi: 10.1152/ajpheart.1995.268.2.H569.
Cycling of various cerebral metabolic substances, arterial vascular diameter, and flow has been noted by many workers at a frequency near 0.1 Hz. Suspicion that this phenomenon is dependent on the type of anesthesia led us to investigate the occurrence of cerebral blood flow (CBF) cycling with different anesthetics. Fifteen Sprague-Dawley rats were anesthetized with either pentobarbital (n = 5, 40-50 mg/kg), alpha-chloralose (n = 5, 60 mg/kg), or halothane (n = 5, 1-0.5%). Body temperature was maintained at 37 degrees C. Femoral arterial and venous catheters were placed, and a tracheotomy was performed, permitting artificial ventilation with 30% O2-70% N2. A closed cranial window was formed over a 3-mm diameter craniotomy. Mean arterial pressure (MABP), arterial partial pressures of CO2 and O2 (PaCO2 and PaO2), and pH were controlled and stabilized at normal values. CBF was determined using laser Doppler flowmetry. To induce cycling, MABP was transiently and repeatedly lowered by exsanguination. Fast Fourier analysis of selected 64-s flow recordings (n = 38) was performed. CBF cycling was observed, independent of the type of anesthesia, in all animals. In 36 epochs, cycling was induced when MABP was reduced to a mean pressure of 65 +/- 1.5 mmHg. The mean frequency and amplitude were 0.094 +/- 0.003 Hz and 6.6 +/- 0.5%, respectively. Cycling occurred without blood withdrawal in two epochs. With the use of the blood-withdrawal epochs (n = 36), all three anesthetics shared a common linear slope between amplitude and blood pressure (P < 0.02) and blood pressure change (P < 0.01). Pentobarbital differed from alpha-chloralose and halothane in the relation between cycling frequency and blood pressure. Only pentobarbital exhibited correlation between frequency and blood pressure (P < 0.02) and blood pressure change (P < 0.001). The occurrence of these oscillations is not related to the type of anesthesia, and they usually occur at MABP values that are near or just above the lower limit of autoregulation. At this pressure level, CBF oscillations would suggest that vasoconstrictive and dilatory forces are no longer in balance, but alternatively vying for control.
许多研究人员已注意到，多种脑代谢物质、动脉血管直径和血流量以接近0.1赫兹的频率循环变化。鉴于怀疑这种现象取决于麻醉类型，我们开展研究以探究不同麻醉剂作用下脑血流量（CBF）循环变化的情况。15只Sprague-Dawley大鼠分别用戊巴比妥（n = 5，40 - 50毫克/千克）、α-氯醛糖（n = 5，60毫克/千克）或氟烷（n = 5，1 - 0.5%）麻醉。体温维持在37摄氏度。插入股动脉和静脉导管，并实施气管切开术，以便用30%氧气 - 70%氮气进行人工通气。在直径3毫米的颅骨切开术上方形成一个封闭的颅骨视窗。平均动脉压（MABP）、动脉血二氧化碳和氧气分压（PaCO2和PaO2）以及pH值均控制并稳定在正常值。使用激光多普勒血流仪测定CBF。为诱导循环变化，通过放血使MABP短暂且反复降低。对选定的64秒血流记录（n = 38）进行快速傅里叶分析。在所有动物中均观察到CBF循环变化，且与麻醉类型无关。在36个时间段中，当MABP降至平均压力65±1.5毫米汞柱时诱导出循环变化。平均频率和幅度分别为0.094±0.003赫兹和6.6±0.5%。在两个时间段中未通过放血诱导出循环变化。在使用放血的时间段（n = 36）中，所有三种麻醉剂在幅度与血压（P < 0.02）以及血压变化（P < 0.01）之间均呈现共同的线性斜率。戊巴比妥在循环频率与血压的关系上与α-氯醛糖和氟烷不同。只有戊巴比妥在频率与血压（P < 0.02）以及血压变化（P < 0.001）之间呈现相关性。这些振荡的发生与麻醉类型无关，且通常发生在接近或刚好高于自动调节下限的MABP值时。在此压力水平下，CBF振荡表明血管收缩力和扩张力不再平衡，而是相互竞争以进行控制。
