不同类型心脏患者心内直视手术期间呼气末CO2分压与动脉血CO2分压及其差值的变化

Change of P（a-ET） CO2 in patients undergoing cardiopulmonary bypass

目的探讨不同类型心脏患者心内直视手术期间呼气末二氧化碳分压（PETCO2）与动脉血二氧化碳分压（PaCO2）的相关性及二者差值[P（a-ET）、CO2]的临床意义。方法45例患者分成3组，每组15例。A组：左向右分流组；B组：无分流组；C组：右向左分流组。3组分别于术前（T0）、插管后15min（T1）、手术开始时（T2）、转流前（T3）、转流停止后15min（T4）、术毕时（T5）共6个时点，用旁气流法监测PETCO2，同时抽动脉血测定PaCO2，应用直线回归分析3组各时点PETCO2与PaCO2的相关性，同时计算并分析各组不同时点的P（a-ET）CO2。结果（1）A组、B组各时点PETCO2与PaCO2呈正相关，A组r为0．70—0．85（P〈0．01），B组r为0．71—0．79（P〈0．01）；C组麻醉开始至转停后PETCO2与PaCO2均无相关（0．46—0．54，P〉0．05），而到术毕时则呈正相关（r=0．66，P〈0．05）。（2）3组患者转流前的P（a-ET）CO2变化不大，停转流后A组、B组P[a-ET）CO2增加，其中以A组增加较明显（P〈0．01），而C组P（a-ET）CO2显著减少（P〈0．05）。结论无分流或左向右分流心脏患者在体外循环转流前后PETCO2与PaCO2的相关性较好；右向左分流心脏患者转流前的相关性较差，心内畸形纠正后其相关性可发生变化。P（a-ET）CO2在不同的心脏患者之间差异较大，必须与PaCO2相结合，才能正确指导临床。

Objective To investigate the relationship between PET CO2 and PaCO2, amd dinilal significance of Pa-ET Co2in patients undergoing cardiopulmonary bypass. Methods Forty-five patients scheduled for cardiac surgery were divided into three groups ： left-to-right shunt group（ group A, n = 15 ） ; no shunt group （ group B, n = 15 ） ; right-to-left shunt group （ group C, n = 15 ）. PET CO2, PaCO2 and P（a-ET） CO2 were detected before operation （ T0 ）, 15 min after intuhation （ Tl ）, at operation onset （ T2 ）, before by-pass （T3） ,15 min after by-pass shutdown （T4）and at the end of operation （T5） respectively. Results PerCO2 and PaCO2 were positively correlated at every time point in the group A and B. The correlation coefficient was 0.70 to 0.85 in group A（ P 〈0.01 ） and 0.71to 0.79 in group B（ P 〈0.01 ） ;hut they were only correlated at the end of operation in the group C （ P 〈 0.05） . At T3, no evident change was detected in three groups. In group A and B, P（a-ET） CO2 was significantly increased after ceasing cardiopulmonary bypass, while it was significantly decreased in group C. Conclusions PET CO2 and PaCO2 are positively correlated before and after cardiopulmonary bypass in no shunt and left-to-right shunt patients. While they are not correlated before cardiopulmonary bypass but may change their correlation after cardiopulmonary bypass in right-to-left shunt patients. Significant difference of P（a-ET） CO2 may be detected among different cardiac disease patients. Therefore it must be combined with PaCO2 for correct guidance of clinical practice.