Galvin S D, Celi L A, Thomas K N, Clendon T R, Galvin I F, Bunton R W, Ainslie P N
Department of Cardiothoracic Surgery, Section of Surgery, University of Otago and Dunedin Hospital, New Zealand.
Anaesth Intensive Care. 2010 Jul;38(4):710-7. doi: 10.1177/0310057X1003800415.
Alterations in cerebrovascular reactivity to CO2, an index of cerebrovascular function, have been associated with increased risk of stroke. We hypothesised that cerebrovascular reactivity is impaired with increasing age and in patients with symptomatic coronary artery disease (CAD). Cerebrovascular and cardiovascular reactivity to CO2 was assessed at rest and during hypercapnia (5% CO2) and hypocapnia (hyperventilation) in subjects with symptomatic CAD (n=13) and age-matched old (n=9) and young (n=20) controls without CAD. Independent of CAD, reductions in middle cerebral artery blood velocity (transcranial Doppler) and cerebral oxygenation (near-infrared spectroscopy) were correlated with increasing age (r = -0.68, r = -0.51, respectively, P < 0.01). In CAD patients, at rest and during hypercapnia, cerebral oxygenation was lower (P < 0.05 vs. young). Although middle cerebral artery blood velocity reactivity was unaltered in the hypercapnic range, middle cerebral artery blood velocity reactivity to hypocapnia was elevated in the CAD and age-matched controls (P < 0.01 vs. young), and was associated with age (r = 0.62, P < 0.01). Transient drops in arterial PCO2 occur in a range of physiological and pathophysiological situations, therefore, the elevated middle cerebral artery blood velocity reactivity to hypocapnia combined with reductions in middle cerebral artery blood velocity may be important mechanisms underlying neurological risk with aging. In CAD patients, additional reductions in cerebral oxygenation may place them at additional risk of cerebral ischaemia.
脑血管对二氧化碳的反应性改变是脑血管功能的一个指标，与中风风险增加有关。我们假设，随着年龄增长以及在有症状的冠状动脉疾病（CAD）患者中，脑血管反应性会受损。在静息状态以及高碳酸血症（5%二氧化碳）和低碳酸血症（过度通气）期间，对有症状CAD患者（n = 13）以及年龄匹配的老年（n = 9）和年轻（n = 20）无CAD对照者的脑血管和心血管对二氧化碳的反应性进行了评估。与CAD无关，大脑中动脉血流速度（经颅多普勒）和脑氧合（近红外光谱）的降低与年龄增长相关（分别为r = -0.68，r = -0.51，P < 0.01）。在CAD患者中，静息时和高碳酸血症期间，脑氧合较低（与年轻组相比P < 0.05）。尽管大脑中动脉血流速度在高碳酸血症范围内的反应性未改变，但大脑中动脉血流速度对低碳酸血症的反应性在CAD患者和年龄匹配的对照者中升高（与年轻组相比P < 0.01），并且与年龄相关（r = 0.62，P < 0.01）。在一系列生理和病理生理情况下会出现动脉PCO2的短暂下降，因此，大脑中动脉血流速度对低碳酸血症的反应性升高以及大脑中动脉血流速度降低可能是衰老导致神经风险的重要机制。在CAD患者中，脑氧合的进一步降低可能使他们面临脑缺血的额外风险。
