Ide K, Pott F, Van Lieshout J J, Secher N H
Copenhagen Muscle Research Centre, Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Denmark.
Acta Physiol Scand. 1998 Jan;162(1):13-20. doi: 10.1046/j.1365-201X.1998.0280f.x.
We tested the hypothesis that pharmacological reduction of the increase in cardiac output during dynamic exercise with a large muscle mass would influence the cerebral blood velocity/perfusion. We studied the relationship between changes in cerebral blood velocity (transcranial Doppler), rectus femoris blood oxygenation (near-infrared spectroscopy) and systemic blood flow (cardiac output from model flow analysis of the arterial pressure wave) as induced by dynamic exercise of large (cycling) vs. small muscle groups (rhythmic handgrip) before and after cardioselective beta 1 adrenergic blockade (0.15 mg kg-1 metoprolol i.v.). During rhythmic handgrip, the increments in systemic haemodynamic variables as in middle cerebral artery mean blood velocity were not influenced significantly by metoprolol. In contrast, during cycling (e.g. 113 W), metoprolol reduced the increase in cardiac output (222 +/- 13 vs. 260 +/- 16%), heart rate (114 +/- 3 vs. 135 +/- 7 beats min-1) and mean arterial pressure (103 +/- 3 vs. 112 +/- 4 mmHg), and the increase in cerebral artery mean blood velocity also became lower (from 59 +/- 3 to 66 +/- 3 vs. 60 +/- 2 to 72 +/- 3 cm s-1; P < 0.05). Likewise, during cycling with metoprolol, oxyhaemoglobin in the rectus femoris muscle became reduced (compared to rest: -4.8 +/- 1.8 vs. 1.2 +/- 1.7 mumol L-1, P < 0.05). Neither during rhythmic handgrip nor during cycling was the arterial carbon dioxide tension affected significantly by metoprolol. The results suggest that as for the muscle blood flow, the cerebral circulation is also affected by a reduced cardiac output during exercise with a large muscle mass.
通过药物降低大肌肉群动态运动期间心输出量的增加会影响脑血流速度/灌注。我们研究了在心脏选择性β1肾上腺素能阻滞剂（0.15 mg kg-1美托洛尔静脉注射）前后，大肌肉群（骑自行车）与小肌肉群（有节奏的握力运动）动态运动所诱导的脑血流速度变化（经颅多普勒）、股直肌血氧饱和度（近红外光谱）和全身血流（根据动脉压力波的模型流量分析得出的心输出量）之间的关系。在有节奏的握力运动期间，美托洛尔对全身血流动力学变量（如大脑中动脉平均血流速度）的增加没有显著影响。相比之下，在骑自行车运动时（如113 W），美托洛尔降低了心输出量的增加（222±13%对260±16%）、心率（114±3次/分钟对135±7次/分钟）和平均动脉压（103±3 mmHg对112±4 mmHg），大脑动脉平均血流速度的增加也降低了（从59±3到66±3 cm/s对60±2到72±3 cm/s；P<0.05）。同样，在服用美托洛尔进行骑自行车运动时，股直肌中的氧合血红蛋白减少（与静息状态相比：-4.8±1.8 μmol/L对1.2±1.7 μmol/L，P<0.05）。无论是在有节奏的握力运动期间还是在骑自行车运动期间，美托洛尔对动脉二氧化碳分压均无显著影响。结果表明，对于肌肉血流而言，大肌肉群运动期间心输出量的减少也会影响脑循环。
