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

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Pa-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。

Change of P_((a-ET)) CO_2 in patients undergoing cardiopulmonary bypass

Objective To investigate the relationship between PETCO_2 and PaCO_2,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).PETCO_2,PaCO_2 and P(a-ET)CO_2 were detected before operation(T0),15 min after intubation(T1),at operation onset(T2),before by-pass(T3),15 min after by-pass shutdown(T4)and at the end of operation(T5)respectively.Results PETCO_2 and PaCO_2 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);but 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)CO_2 was significantly increased after ceasing cardiopulmonary bypass,while it was significantly decreased in group C.Conclusions PETCO_2 and PaCO_2 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)CO_2 may be detected among different cardiac disease patients.Therefore it must be combined with PaCO_2 for correct guidance of clinical practice.