Fullerton D A, Kirson L E, St Cyr J A, Kinnard T, Whitman G J
Department of Surgery, University of Colorado Health Sciences Center, Denver 80262.
J Thorac Cardiovasc Surg. 1993 Sep;106(3):528-36.
Disturbances of respiratory acid-base status are common in patients supported with mechanical ventilation of the lungs after cardiac operations. This study was conducted with two protocols. The purpose was to determine whether respiratory acid-base status influences pulmonary vascular resistance in adults after cardiac operations and whether the influence is mediated by hydrogen ion concentration or carbon dioxide tension. Patients were studied while under general anesthesia immediately after aorta-coronary bypass. In the first protocol, with seven patients, arterial carbon dioxide tension was manipulated by the addition of 5% carbon dioxide to the breathing circuit. Pulmonary vascular resistance index was determined as arterial carbon dioxide tension rose from 30 mm Hg to 50 mm Hg and back to 30 mm Hg. In the second protocol, with 10 different patients, hydrogen ion concentration was manipulated by the addition of 0.2N hydrochloric acid, sodium bicarbonate, or both as arterial carbon dioxide tension was held constant. We used analysis of variance for statistical data. The results of the first protocol showed that pulmonary vascular resistance index rose by 44% (p < 0.05) as arterial carbon dioxide tension rose from 30 to 50 mm Hg. The results of the second protocol showed that changes in pulmonary vascular resistance index were parallel to changes in hydrogen ion concentration as arterial carbon dioxide tension was held constant (p < 0.05). These data demonstrate that respiratory acid-base status is an important determinant of pulmonary vascular resistance in the adult after cardiac operations. Furthermore, these data suggest the effect is mediated by hydrogen ion concentration, not carbon dioxide tension.
心脏手术后接受肺机械通气支持的患者中，呼吸性酸碱状态紊乱很常见。本研究采用了两种方案。目的是确定呼吸性酸碱状态是否会影响心脏手术后成人的肺血管阻力，以及这种影响是否由氢离子浓度或二氧化碳分压介导。在主动脉冠状动脉搭桥术后立即在全身麻醉下对患者进行研究。在第一个方案中，对7名患者，通过向呼吸回路中添加5%二氧化碳来控制动脉二氧化碳分压。随着动脉二氧化碳分压从30mmHg升至50mmHg再降至30mmHg，测定肺血管阻力指数。在第二个方案中，对10名不同的患者，在动脉二氧化碳分压保持恒定的情况下，通过添加0.2N盐酸、碳酸氢钠或两者来控制氢离子浓度。我们对统计数据使用方差分析。第一个方案的结果表明，随着动脉二氧化碳分压从30mmHg升至50mmHg，肺血管阻力指数上升了44%（p<0.05）。第二个方案的结果表明，在动脉二氧化碳分压保持恒定的情况下，肺血管阻力指数的变化与氢离子浓度的变化平行（p<0.05）。这些数据表明，呼吸性酸碱状态是心脏手术后成人肺血管阻力的重要决定因素。此外，这些数据表明这种作用是由氢离子浓度介导的，而不是二氧化碳分压。
