Tominaga R, Smith W A, Massiello A, Harasaki H, Golding L A
Department of Biomedical Engineering, Cleveland Clinic Foundation, Ohio.
J Thorac Cardiovasc Surg. 1994 Nov;108(5):907-12.
To investigate the response of the carotid blood flow and general circulation to hypercapnia in chronic nonpulsatile blood flow, we performed 18 carbon dioxide gas inhalation studies on three calves undergoing a centrifugal biventricular bypass with ventricular fibrillation. An ultrasonic flow probe was put on the carotid artery during biventricular bypass pump implantation, and pump flows were maintained at 90, 100, and 120 ml/kg per minute for 1 week each. The carbon dioxide inhalation studies were performed twice a week. Hypercapnia was induced by administering pure carbon dioxide gas through a nasal tube at flow rates of 0, 5, 7.5, 10, 12.5, and 15 L/min for 5 minutes each at three different nominal pump flow rates, and the resultant arterial blood gas and hemodynamic changes were recorded. No significant correlation existed between the carotid blood flow and mean aortic pressure, which varied from 70 to 140 mm Hg, but the carotid blood flow correlated significantly (p < 0.01) with the systemic pump flow rate. A significant (p < 0.01) linear relationship was found between the carotid blood flow and arterial carbon dioxide tension. For each 1 mm Hg change in arterial carbon dioxide tension, there was a 2.8 % change in the carotid blood flow. The percent changes in the carotid blood flow in response to arterial carbon dioxide tension were calculated as 2.9%, 3.7%, and 2.5% for each 1 mm Hg change in arterial carbon dioxide tension at pump flows of 90, 100 and 120 ml/kg per minute. No significant differences in the carotid blood flow response to hypercapnia were detected among the three systemic pump flow rates. These results thus suggested that chronic nonpulsatile blood flow had no detrimental effects on cerebral autoregulation.
为研究慢性非搏动性血流状态下颈动脉血流及全身循环对高碳酸血症的反应，我们对三头接受离心式双心室旁路并伴有心室颤动的小牛进行了18次二氧化碳气体吸入研究。在植入双心室旁路泵期间，将超声血流探头置于颈动脉上，泵流量分别维持在每分钟90、100和120 ml/kg，各维持1周。每周进行两次二氧化碳吸入研究。通过鼻管以0、5、7.5、10、12.5和15 L/min的流速给予纯二氧化碳气体5分钟，在三种不同的名义泵流量下诱发高碳酸血症，并记录由此产生的动脉血气和血流动力学变化。颈动脉血流与平均主动脉压之间无显著相关性，平均主动脉压在70至140 mmHg之间变化，但颈动脉血流与全身泵流量显著相关（p < 0.01）。发现颈动脉血流与动脉二氧化碳分压之间存在显著的（p < 0.01）线性关系。动脉二氧化碳分压每变化1 mmHg，颈动脉血流变化2.8%。在泵流量为每分钟90、100和120 ml/kg时，动脉二氧化碳分压每变化1 mmHg，颈动脉血流的变化百分比分别计算为2.9%、3.7%和2.5%。在三种全身泵流量之间，未检测到对高碳酸血症的颈动脉血流反应有显著差异。因此，这些结果表明慢性非搏动性血流对脑自动调节无有害影响。
