Alston R P, Murray L, McLaren A D
Department of Anaesthesia, University of Glasgow, Scotland.
J Thorac Cardiovasc Surg. 1990 Jul;100(1):134-44.
During hypothermic cardiopulmonary bypass, the effects on hemodynamic variables of alternating pump flow rate between 1.5 and 2.0 L.min-1.m-2, flow character between nonpulsatile and pulsatile perfusion, and acid-base management between pH- and alpha-stat control were studied in a crossover factorial experiment. Twenty-four patients who were undergoing elective coronary artery bypass grafting were studied during stable hypothermic (27 degrees to 29 degrees C) cardiopulmonary bypass. A minimum of two (when time allowed, three) consecutive 10-minute periods (period 1, 2, or 3) were investigated. Only stage of the study period during cardiopulmonary bypass, flow rate, and interaction between stage and acid-base management were found to have significant effects on mean arterial pressure. In all patients, there were average increases in mean arterial pressure from period 1 to period 2 of 9.4 (95% confidence interval 5.8, 13.0) mm Hg, from period 2 to period 3 of 6.3 (95% confidence interval 1.2, 11.4) mm Hg, and from period 1 to period 3 of 15.7 (95% confidence interval 10.6, 20.9) mm Hg. At 2.0 L.min-1.m-2, mean arterial pressure was 7.2 (95% confidence interval 1.6, 12.9) mm Hg higher than at 1.5 L.min-1.m-2. Peripheral vascular resistance was significantly affected only by stage and flow rate. There were, in all patients, mean increases in peripheral vascular resistance from period 1 to period 2 of 239 (95% confidence interval 135, 343) dynes.sec.cm-5, from period 2 to period 3 of 85 (-64, 234) dynes.sec.cm-5, and from period 1 to period 3 of 324 (95% confidence interval 175, 473) dynes.sec.cm-5. At 1.5 L.min-1.m-2, the peripheral vascular resistance was 316 (95% confidence interval 152, 480) dynes.sec.cm-5 higher than at 2.0 L.min-1.m-2. Alteration in flow rate, but not flow character or arterial pH, had a significant effect on peripheral vascular resistance. It is hypothesized that the increase in peripheral vascular resistance during the course of cardiopulmonary bypass results from an active capillary mechanism, whereas the increase that is associated with reduction in flow rate reflects a passive mechanism. The increase in peripheral vascular resistance with decrease in flow rate indicates impaired tissue perfusion, unlike that occurring with stage.
在低温体外循环期间，通过交叉析因实验研究了泵流量在1.5至2.0L·min⁻¹·m⁻²之间交替、非搏动性与搏动性灌注的血流特性以及pH值控制与α稳态控制之间的酸碱管理对血流动力学变量的影响。对24例接受择期冠状动脉搭桥术的患者在稳定的低温（27至29摄氏度）体外循环期间进行了研究。最少连续研究两个（时间允许时为三个）10分钟时段（时段1、2或3）。仅发现体外循环期间的研究阶段、流量以及阶段与酸碱管理之间的相互作用对平均动脉压有显著影响。在所有患者中，平均动脉压从时段1到时段2平均升高9.4（95%置信区间5.8，13.0）mmHg，从时段2到时段3升高6.3（95%置信区间1.2，11.4）mmHg，从时段1到时段3升高15.7（95%置信区间10.6，20.9）mmHg。在2.0L·min⁻¹·m⁻²时，平均动脉压比1.5L·min⁻¹·m⁻²时高7.2（95%置信区间1.6，12.9）mmHg。外周血管阻力仅受阶段和流量的显著影响。在所有患者中，外周血管阻力从时段1到时段2平均增加239（95%置信区间135，343）达因·秒·厘米⁻⁵，从时段2到时段3增加85（-64，234）达因·秒·厘米⁻⁵，从时段1到时段3增加324（95%置信区间175，473）达因·秒·厘米⁻⁵。在1.5L·min⁻¹·m⁻²时，外周血管阻力比2.0L·min⁻¹·m⁻²时高316（95%置信区间152，480）达因·秒·厘米⁻⁵。流量的改变而非血流特性或动脉pH值对外周血管阻力有显著影响。据推测，体外循环过程中外周血管阻力的增加源于一种主动的毛细血管机制，而与流量降低相关的增加反映了一种被动机制。与阶段不同，随着流量降低外周血管阻力增加表明组织灌注受损。
