Graham J M, Gibbs N M, Weightman W M, Sheminant M R
Department of Anaesthesia, Sir Charles Gairdner Hospital, Nedlands, Perth, Western Australia.
Anaesth Intensive Care. 2005 Aug;33(4):457-61. doi: 10.1177/0310057X0503300406.
During cardiopulmonary bypass the partial pressure of carbon dioxide in oxygenator arterial blood (P(a)CO2) can be estimated from the partial pressure of gas exhausting from the oxygenator (P(E)CO2). Our hypothesis is that P(E)CO2 may be used to estimate P(a)CO2 with limits of agreement within 7 mmHg above and below the bias. (This is the reported relationship between arterial and end-tidal carbon dioxide during positive pressure ventilation in supine patients.) During hypothermic (28-32 degrees C) cardiopulmonary bypass using a Terumo Capiox SX membrane oxygenator, 80 oxygenator arterial blood samples were collected from 32 patients during cooling, stable hypothermia, and rewarming as per our usual clinical care. The P(a)CO2 of oxygenator arterial blood at actual patient blood temperature was estimated by temperature correction of the oxygenator arterial blood sample measured in the laboratory at 37 degrees C. P(E)CO2 was measured by connecting a capnograph end-to-side to the oxygenator exhaust outlet. We used an alpha-stat approach to cardiopulmonary bypass management. The mean difference between P(E)CO2 and P(a)CO2 was 0.6 mmHg, with limits of agreement (+/-2 SD) between -5 to +6 mmHg. P(E)CO2 tended to underestimate P(a)CO2 at low arterial temperatures, and overestimate at high arterial temperatures. We have demonstrated that P(E)CO2 can be used to estimate P(a)CO2 during hypothermic cardiopulmonary bypass using a Terumo Capiox SX oxygenator with a degree of accuracy similar to that associated with the use of end-tidal carbon dioxide measurement during positive pressure ventilation in anaesthetized, supine patients.
在体外循环期间，氧合器动脉血中的二氧化碳分压（P(a)CO2）可根据氧合器排出气体的分压（P(E)CO2）来估算。我们的假设是，P(E)CO2可用于估算P(a)CO2，其一致性界限在偏差值上下7 mmHg范围内。（这是仰卧位患者在正压通气期间动脉血与呼气末二氧化碳之间报道的关系。）在使用Terumo Capiox SX膜式氧合器进行低温（28 - 32摄氏度）体外循环期间，按照我们常规的临床护理，在32例患者的降温、稳定低温和复温过程中采集了80份氧合器动脉血样本。通过对在实验室37摄氏度下测量的氧合器动脉血样本进行温度校正，估算实际患者体温下氧合器动脉血的P(a)CO2。通过将二氧化碳分析仪端对端连接到氧合器排气口来测量P(E)CO2。我们采用α稳态方法进行体外循环管理。P(E)CO2与P(a)CO2之间的平均差值为0.6 mmHg，一致性界限（±2 SD）为 - 5至 + 6 mmHg。在低动脉温度时，P(E)CO2往往低估P(a)CO2，而在高动脉温度时则高估。我们已经证明，在使用Terumo Capiox SX氧合器进行低温体外循环期间，P(E)CO2可用于估算P(a)CO2，其准确度类似于在麻醉仰卧位患者正压通气期间使用呼气末二氧化碳测量的准确度。
