Abstract：
OBJECTIVE: Central venous-arterial PCO2 to arterial-central venous O2 content ratio (Pcv-aCO2/Ca-cvO2) is commonly used as a surrogate for respiratory quotient (RQ) and tissue oxygenation. Although Pcv-aCO2/Ca-cvO2 might be associated with hyperlactatemia and outcome, neither the interchangeability with RQ nor the correlation with conclusive variables of anaerobic metabolism has never been demonstrated in septic shock. Our goal was to compare Pcv-aCO2/Ca-cvO2 and RQ in patients with septic shock.
METHODS: Prospective, observational study.
METHODS: Two adult ICUs.
METHODS: Forty-seven patients with septic shock on mechanical ventilation with stable respiratory settings and vasopressor dose after initial resuscitation.
METHODS: None.
METHODS: We measured arterial and central venous gases, Hb, and O2Hb. Pcv-aCO2/Ca-cvO2 and the ratio of central venous-arterial CO2 content to arterial-central venous O2 content (Ccv-aCO2/Ca-cvO2) were calculated. RQ was determined by indirect calorimetry.
RESULTS: Pcv-aCO2/Ca-cvO2 and Ccv-aCO2/Ca-cvO2 were not correlated with RQ (R2 = 0.01, P = 0.50 and R2 = 0.01, P = 0.58, respectively), showing large bias and wide 95 % limits of agreement with RQ (1.09, -1.10-3.27 and 0.42, -1.53-2.37). A multiple linear regression model showed Hb, and central venous PCO2 and O2Hb, but not RQ, as Pcv-aCO2/Ca-cvO2 determinants (R2 = 0.36, P = 0.0007).
CONCLUSIONS: In patients with septic shock, Pcv-aCO2/Ca-cvO2 did not correlate with RQ and was mainly determined by factors that modify the dissociation of CO2 from Hb. Pcv-aCO2/Ca-cvO2 seems to be a poor surrogate for RQ; therefore, its values should be interpreted with caution.
METHODS: Prospective, observational study.
METHODS: Two adult ICUs.
METHODS: Forty-seven patients with septic shock on mechanical ventilation with stable respiratory settings and vasopressor dose after initial resuscitation.
METHODS: None.
METHODS: We measured arterial and central venous gases, Hb, and O2Hb. Pcv-aCO2/Ca-cvO2 and the ratio of central venous-arterial CO2 content to arterial-central venous O2 content (Ccv-aCO2/Ca-cvO2) were calculated. RQ was determined by indirect calorimetry.
RESULTS: Pcv-aCO2/Ca-cvO2 and Ccv-aCO2/Ca-cvO2 were not correlated with RQ (R2 = 0.01, P = 0.50 and R2 = 0.01, P = 0.58, respectively), showing large bias and wide 95 % limits of agreement with RQ (1.09, -1.10-3.27 and 0.42, -1.53-2.37). A multiple linear regression model showed Hb, and central venous PCO2 and O2Hb, but not RQ, as Pcv-aCO2/Ca-cvO2 determinants (R2 = 0.36, P = 0.0007).
CONCLUSIONS: In patients with septic shock, Pcv-aCO2/Ca-cvO2 did not correlate with RQ and was mainly determined by factors that modify the dissociation of CO2 from Hb. Pcv-aCO2/Ca-cvO2 seems to be a poor surrogate for RQ; therefore, its values should be interpreted with caution.
摘要：
目的：中心静脉-动脉PCO2与动脉-中心静脉O2含量之比（Pcv-aCO2/Ca-cvO2）通常用作呼吸商（RQ）和组织氧合的替代指标。虽然Pcv-aCO2/Ca-cvO2可能与高乳酸盐血症和结果相关，在脓毒性休克中，从未证明与RQ的互换性或与厌氧代谢的决定性变量的相关性。我们的目标是比较感染性休克患者的Pcv-aCO2/Ca-cvO2和RQ。
方法：前瞻性，观察性研究。
方法：两个成人ICU。
方法：47例脓毒性休克患者在初次复苏后接受机械通气，呼吸设置稳定，血管加压药剂量。
方法：无。
方法：我们测量了动脉和中心静脉气体，Hb,O2Hb计算Pcv-aCO2/Ca-cvO2以及中心静脉-动脉CO2含量与动脉-中心静脉O2含量之比（Ccv-aCO2/Ca-cvO2）。通过间接量热法测定RQ。
结果:Pcv-aCO2/Ca-cvO2和Ccv-aCO2/Ca-cvO2与RQ无相关性(R2=0.01,P=0.50,R2=0.01,P=0.58),与RQ（1.09，-1.10-3.27和0.42，-1.53-2.37）显示出较大的偏差和95%的一致性界限。多元线性回归模型显示Hb,和中心静脉PCO2和O2Hb，但不是RQ,作为Pcv-aCO2/Ca-cvO2的决定因素(R2=0.36,P=0.0007)。
结论：在感染性休克患者中，Pcv-aCO2/Ca-cvO2与RQ无关，主要由改变Hb中CO2解离的因素决定。Pcv-aCO2/Ca-cvO2似乎是RQ的不良替代品；因此，它的价值应该谨慎解释。
方法：前瞻性，观察性研究。
方法：两个成人ICU。
方法：47例脓毒性休克患者在初次复苏后接受机械通气，呼吸设置稳定，血管加压药剂量。
方法：无。
方法：我们测量了动脉和中心静脉气体，Hb,O2Hb计算Pcv-aCO2/Ca-cvO2以及中心静脉-动脉CO2含量与动脉-中心静脉O2含量之比（Ccv-aCO2/Ca-cvO2）。通过间接量热法测定RQ。
结果:Pcv-aCO2/Ca-cvO2和Ccv-aCO2/Ca-cvO2与RQ无相关性(R2=0.01,P=0.50,R2=0.01,P=0.58),与RQ（1.09，-1.10-3.27和0.42，-1.53-2.37）显示出较大的偏差和95%的一致性界限。多元线性回归模型显示Hb,和中心静脉PCO2和O2Hb，但不是RQ,作为Pcv-aCO2/Ca-cvO2的决定因素(R2=0.36,P=0.0007)。
结论：在感染性休克患者中，Pcv-aCO2/Ca-cvO2与RQ无关，主要由改变Hb中CO2解离的因素决定。Pcv-aCO2/Ca-cvO2似乎是RQ的不良替代品；因此，它的价值应该谨慎解释。
