P(cv-a)CO_2/C(a-cv)O_2对成人脓毒性休克患者液体复苏后氧代谢变化的预测价值

The Predictive value of P(cv-a)CO_2/C(a-cv)O_2 Ratio for Oxygen Metabolism after Fluid Resuscitation in Adult Septic Shock Patients

目的评价中心静脉-动脉二氧化碳分压差/动脉-中心静脉氧含量差比值[P(cv-a)CO_2/C(a-cv)O_2]对脓毒性休克患者液体复苏后氧代谢变化的预测价值。方法采用前瞻性观察研究方法,纳入2013年11月至2014年4月南京大学医学院附属鼓楼医院重症医学科收治的脓毒性休克患者。所有患者均给予容量负荷试验(生理盐水300 ml于20 min内经静脉快速滴注)。根据液体复苏前后心排指数的变化(ΔCI),分为液体有反应组(ΔCI≥10%)和无反应组(ΔCI<10%)。在液体有反应组,根据液体复苏前后氧耗的变化(ΔVO_2)分为ΔVO_2≥10%和ΔVO_2<10%两个亚组。采用脉搏指示连续心排出量(PICCO)监测患者的心排指数(CI),并通过血气分析测定患者血红蛋白水平、动脉血二氧化碳(Pa CO_2)、动脉血氧分压(Pa O_2)、动脉血氧饱和度(Sa O_2)、动脉血乳酸、中心静脉血二氧化碳(Pcv CO_2)、中心静脉血氧分压(Pcv O_2)、中心静脉血氧饱和度(Scv O_2),并计算P(cv-a)CO_2/C(a-cv)O_2和氧耗(VO_2)。比较两组患者液体复苏前后的P(cv-a)CO_2/C(a-cv)O_2指标差异。结果纳入18例脓毒性休克患者,共实施液体复苏23次,其中液体有反应性17例次,无反应性6例次。液体有反应组和无反应组比较,复苏前P(cv-a)CO_2/C(a-cv)O_2、动脉血乳酸、Scv O_2均无显著差异[P(cv-a)CO_2/C(a-cv)O_2(mm Hg/ml):2.05±0.75 vs.1.58±0.67;乳酸(mmol/L):3.78±2.50 vs.3.26±2.42;Scv O_2(%):73.71±9.64 vs.70.30±12.01,均P>0.05)。液体有反应组中,有10例次ΔVO_2≥10%,7例次ΔVO_2<10%,ΔVO_2≥10%亚组复苏前P(cv-a)CO_2/C(a-cv)O_2(mm Hg/ml)显著高于ΔVO_2<10%亚组(2.43±0.73 vs.1.51±0.37,P<0.01),动脉血乳酸(mmol/L)亦显著高于ΔVO_2<10%亚组(4.53±2.52 vs.1.46±0.82,P<0.01),Scv O_2(%)无显著变化(70.79±9.15 vs.72.13±13.42,P>0.05)。P(cv-a)CO_2/C(a-cv)O_2、乳酸和Scv O_2预测复苏后ΔVO_2≥10%的受试者工作特征曲线下面积(AUC)分别为0.843、0.921、0.529。以P(cv-a)CO_2/C(a-cv)O_2≥1.885 mm Hg/ml预测液体复苏后ΔVO_2≥10%的敏感性为70%,特异性为86%。结论对于有液体反应性的脓毒性休克患者,P(cv-a)CO_2/C(a-cv)O_2可用于预测液体复苏后氧代谢的变化,是一项指导液体复苏的有效指标。

Objective To investigate the value of central venous-to-arterial carbon dioxide difference/arterial-tovenous oxygen difference ratio [P（cv-a）CO2/C（a-cv）O2] in predicting oxygen metabolism after fluid resuscitation inpatients with septic shock. Methods A prospective observational study was carried out on septic shock patients admitted in the intensive care unit of Nanjng Drum Tower Hospital from November 2013 to April 2014. All patients underwent fluid challenge （300 ml saline for 20 min, rapid intravenous infusion）. The patients were divided into a fluid responded group （△CI≥ 10%） and a fluid unresponded group （△CI 〈 10%）, according to the change of cardiac output index （△CI） after fluid challenge. Then the patients were divided into two subgroups in the fluid responded group, namely a△VO≥ 10% group and a △VO2 〈 10% group, according to the change ofVO2 （△VO）. Cardiac output index （CI） weredetermined by pulse indicator continuous cardiac output （PICCO）. Hemoglobin, arteril carbon dioxide （PaCO）, arterial oxygen （PaO2）, arterial oxygen saturation （SaO2）, arterial blood lactate, central venous carbon dioxide （PcvCO2）, centralvenous oxygen （PcvO2） and central venous oxygen saturation （ScvO2） were measured by blood gas analysis. P（cv-a）CO2/C（a-cv）O2 and oxygen consumption （VO2） were calculated. P（cv-a）CO2/C（a-cv）O2 before and after fluid challenge was compared between two subgroups. Results Fluid challenges were performed in 23 instances in 18 patients, among which 17 instances were defined as the fluid responded group. Compared with the fluid unresponded group, P（cv-a）CO2/C（a-cv）O2, arterial lactate and ScvO： had no significant difference [P（cv-a）CO2/C（a-cv）O2] （mm Hg/ml）： 2.05±0.75 vs.1.58±0.67; arterial lactate （mmol/1）： 3.78±2.50 vs. 3.26±2.42; ScvO2（%）： 73.71±9.64 vs. 70.30±12.01, P 〉 0.05] in the fluid responded group before resuscitation. In the fluid responded group, there were 10 instances in the △VO≥ 10% group and 7 instances in the △VO2 〈 10% group. P（cv-a）CO2/C（a-cv）O2 （mm Hg/ml） was significantly higher in the △VO≥ 10% group before resuscitation compared with the △VO2 〈 10% group （2.43±0.73 vs. 1.51±0.37, P〈 0.01）. Lactate （mmol/1） was also higher in the △VO2≥ 10% group before resuscitation （4.53±2.52 vs. 1.46±0.82, P 〈 0.01）. ScvO2 （%） had no significant difference between two groups （70.79±9.15 vs. 72.13±13.42, P 〉 0.05）. The areas under ROC curve （AUCs） of P（cv-a）CO2/C（a-cv）O2, lactate and ScvO2 for predicting △VO2≥10% were 0.843, 0.921, and 0.529, respectively. The sensitivity and specificity of P（cv-a）CO2/C（a-cv）O2≥ 1.885 mm Hg/ml for predicting △VO2≥10% after fluid resuscitation were 70% and 86%, respectively. Conclusion For septic shock patients with fluid responsiveness, P（cv-a）CO2/C（a-cv）O2 can predict oxygen metabolism after fluid resuscitation and can be used as a reliable parameter to guide fluid resuscitation.