颈动脉内膜剥脱术中患者呼气末二氧化碳分压对局部脑氧饱和度的影响

The Influence of End-expiratory Carbon Dioxide Partial Pressure on Regional Cerebral Oxygen Saturation in Patients Undergoing Carotid Endarterectomy

目的探讨不同呼气末二氧化碳分压(P_(ET)CO_2)对行颈动脉内膜斑块剥脱术(CEA)患者术中局部脑氧饱和度(rScO_2的影响。方法选择择期行单侧CEA的患者60例作为研究对象,随机分为A、B、C三组,各20例。手术过程中,通过调节呼吸参数,3组患者维持不同的既定P_(ET)CO_2值,P_(ET)CO_2值设定为A组(P_(ET)CO_2值为25～30 mmHg)、B组(P_(ET)CO_2值为35～40 mmHg)、C组(P_(ET)CO_2值为45～50 mmHg)。记录3组患者阻断前(T0)、阻断即刻(T1)、阻断颈动脉后5 min(T2)、阻断颈动脉后10 min(T3)、阻断颈动脉后15 min(T4)时的动静脉血氧含量差(Da-jvO_2)、脑氧摄取率(CERO_2)及rScO_2。结果与T0时刻比较,3组患者T1～4时刻的Da-jvO_2和CERO_2数值均明显低于T0时刻,差异均有统计学意义(均P<0.05);T1时,3组患者的Da-jvO_2和CERO_2数值比较差异均无统计学意义(均P>0.05);T2～4时,B组、C组患者的Da-jvO_2和CERO_2数值均明显高于A组,差异均有统计学意义(均P<0.05);T3、T4时,C组患者的Da-jvO_2和CERO_2数值均明显高于B组,差异均有统计学意义(均P<0.05)。3组患者T1～4时刻术侧rScO_2数值均明显低于非术侧,差异均有统计学意义(均P<0.05);3组患者T1～4时刻术侧rScO_2数值均明显低于T0时刻,差异均有统计学意义(均P<0.05);T1时刻,3组患者术侧rScO_2数值比较差异无统计学意义(P>0.05);T2～4时刻,B组、C组患者术侧rScO_2数值均明显高于A组,差异均有统计学意义(均P<0.05);T3～4时刻,C组患者术侧rScO_2数值均明显高于B组,差异均有统计学意义(均P<0.05)。结论 rScO_2与P_(ET)CO_2变化成正相关,适当增高P_(ET)CO_2后,可使二氧化碳浓度相对性增高,颅内血管扩张增加,脑血流量增大,血p H值相对性降低,氧解离曲线右移,氧气与血红蛋白的结合度降低,脑组织的氧气利用度增加,脑氧的供需平衡得以维持。

Objective To explore the influence of different end-expiratory carbon dioxide partial pressure(PETCO2) on regional cerebral oxygen saturation(rScO2) in patients undergoing carotid endarterectomy(CEA). Methods A total of 60 patients scheduled for unilateral CEA, were selected as the study objects and were randomly divided into groups A, B and C, with 20 cases in each group.During the operation, by adjusting the respiratory parameters, the three groups maintained different established PETCO2 values. The values of PETCO2 were set as group A [25~30 mmHg for PETCO2], group B(35~40 mmHg for PETCO2) and group C(45~50 mmHg for PETCO2). The arteriovenous oxygen content difference(Da-jvO2), cerebral oxygen uptake rate(CERO2)and rScO2 were recorded before(T0), immediately(T1), 5 minutes(T2), 10 minutes(T3) and 15 minutes(T4) of carotid artery occlusion in three groups. Results Compared with the time of T0, the values of da-jvO2 and CERO2 at T1~4 in the three groups were significantly lower than those at T0;and there was statistical significance(P<0.05);at T1, there was no staticstical diffenrencce in the value difference of da-jvO2 and CERO2 in the three groups(P>0.05);at T2~4, the value of da-jvO2 and ERO2 in group B and group C was significantly higher than those in group A(P<0.05). At T3 and T4, the value of da-jvO2 and CERO2 in group C was significantly higher than those in group B, with statistical significance(P<0.05). At T1~4, the rScO2 value of the operative side was significantly lower than that of the non-operative side, with statistical significance(P<0.05);at T1~4, the rScO2 value of the operative side was significantly lower than that of the T0, with statistical significance(P<0.05);at T1, the rScO2 value of the operative side of the three groups had no significant difference(P>0.05);The value of rScO2 in group C was significantly higher than that in group B at T3~4(P<0.05), and the difference was statistically significan t(P<0.05). Conclusion rScO2 is positively correlated with the change of PETCO2. Appropriate increase of PETCO2 can relatively increase carbon dioxide concentration, increase intracranial vasodilation, increase cerebral blood flow, decrease the relativity of blood pH value, shift the oxygen dissociation curve to the right, decrease the binding degree of oxygen and hemoglobin, increase the oxygen utilization of brain tissue, and maintain the balance of brain oxygen supply and demand.