Ratio of Mixed Venous Oxygen Saturation-to-Pulmonary Capillary Wedge Pressure: Insights From the Veterans Affairs Clinical Assessment, Reporting, and Tracking Program

Background: Hemodynamic values from right heart catheterization aid diagnosis and clinical decision-making but may not predict outcomes. Mixed venous oxygen saturation percentage and pulmonary capillary wedge pressure relate to cardiac output and congestion, respectively. We theorized that a novel, simple ratio of these measurements could estimate cardiovascular prognosis. Methods: We queried Veterans Affairs’ databases for clinical, hemodynamic, and outcome data. Using the index right heart catheterization between 2010 and 2016, we calculated the ratio of mixed venous oxygen saturation-to-pulmonary capillary wedge pressure, termed ratio of saturation-to-wedge (RSW). The primary outcome was time to all-cause mortality; secondary outcome was 1-year urgent heart failure presentation. Patients were stratified into quartiles of RSW, Fick cardiac index (CI), thermodilution CI, and pulmonary capillary wedge pressure alone. Kaplan-Meier curves and Cox proportional hazards models related comparators with outcomes. Results: Of 12 019 patients meeting inclusion criteria, 9826 had values to calculate RSW (median 4.00, interquartile range, 2.67–6.05). Kaplan-Meier curves showed early, sustained separation by RSW strata. Cox modeling estimated that increasing RSW by 50% decreases mortality hazard by 19% (estimated hazard ratio, 0.81 [95% CI, 0.79–0.83], P <0.001) and secondary outcome hazard by 28% (hazard ratio, 0.72 [95% CI, 0.70–0.74], P <0.001). Among the 3793 patients with data for all comparators, Cox models showed RSW best associated with outcomes (by both C statistics and Bayes factors). Furthermore, pulmonary capillary wedge pressure was superior to thermodilution CI and Fick CI. Multivariable adjustment attenuated without eliminating the association of RSW with outcomes. Conclusions: In a large national database, RSW was superior to conventional right heart catheterization indices at assessing risk of mortality and urgent heart failure presentation. This simple calculation with routine data may contribute to clinical decision-making in this population.

Non-invasive capnodynamic mixed venous oxygen saturation during major changes in oxygen delivery

Mixed venous oxygen saturation (SvO2) is an important variable in anesthesia and intensive care but currently requires pulmonary artery catheterization. Recently, non-invasive determination of SvO2 (Capno-SvO2) using capnodynamics has shown good agreement against CO-oximetry in an animal model of modest hemodynamic changes. The purpose of the current study was to validate Capno-SvO2 against CO-oximetry during major alterations in oxygen delivery. Furthermore, evaluating fiberoptic SvO2 for its response to the same challenges. Eleven mechanically ventilated pigs were exposed to oxygen delivery changes: increased inhaled oxygen concentration, hemorrhage, crystalloid and blood transfusion, preload reduction and dobutamine infusion. Capno-SvO2 and fiberoptic SvO2 recordings were made in parallel with CO-oximetry. Respiratory quotient, needed for capnodynamic SvO2, was measured by analysis of mixed expired gases. Agreement of absolute values between CO-oximetry and Capno-SvO2 and fiberoptic SvO2 respectively, was assessed using Bland–Altman plots. Ability of Capno- SvO2 and fiberoptic SvO2 to detect change compared to CO-oximetry was assessed using concordance analysis. The interventions caused significant hemodynamic variations. Bias between Capno-SvO2 and CO-oximetry was + 3% points (95% limits of agreements – 7 to + 13). Bias between fiberoptic SvO2 and CO-oximetry was + 1% point, (95% limits of agreements − 7 to + 9). Concordance rate for Capno-SvO2 and fiberoptic SvO2 vs. CO-oximetry was 98% and 93%, respectively. Capno-SvO2 generates absolute values close to CO-oximetry. The performance of Capno-SvO2 vs. CO-oximetry was comparable to the performance of fiberoptic SvO2 vs. CO-oximetry. Capno-SvO2 appears to be a promising tool for non-invasive SvO2 monitoring.

Ứng dụng phương pháp đo lường bão hòa oxy máu tĩnh mạch trộn SVO2 trong hồi sức huyết động bệnh nhân phẫu thuật tim

Quá trình oxy hóa mô cơ quan đầy đủ có vai trò bảo đảm chức năng sống của cơ thể người. Tuy nhiên, người thầy thuốc thường gặp nhiều khó khăn trong việc đánh giá quá trình này ở những bệnh nhân hồi sức. Nhờ sự phát triển kỹ thuật công nghệ đo lường huyết động và bão hòa oxy máu tĩnh mạch trộn SvO2 (mixed venous oxygen saturation) , mà các bác sĩ lâm sàng có thêm phương tiện để đánh giá sự oxy hóa mô trên những bệnh nhân này. Nếu việc theo dõi cung lượng tim và khí máu động mạch giúp đánh giá khả năng cung cấp oxy của cơ thể, thì việc theo dõi bão hòa oxy máu tĩnh mạch trộn SvO2 phản ánh cân bằng cung - cầu oxy của cơ thể. Nó phản ánh tình trạng sinh lý bệnh của hệ thống phổi và tuần hoàn, vì SvO2 phản ánh lượng oxy dự trữ của cơ thể sau khi đã qua quá trình phân tách oxy tại hệ thống mao mạch cho mô cơ quan.

Novel noninvasive estimation of mixed venous oxygen saturation by echocardiography and expired gas analysis

Clinical use of mixed venous oxygen saturation ([Formula: see text]) is limited for the required invasive procedure. With Fick’s equation, expired gas analysis, echocardiography, simple blood tests, and percutaneous oxygen saturation, [Formula: see text] can be calculated noninvasively. We hypothesized that noninvasively calculated [Formula: see text] shows a significant correlation and agrees well with invasively measured [Formula: see text]. The present study examined the relationship between measured [Formula: see text] and calculated [Formula: see text] in patients who underwent right heart catheterization and demonstrated acceptable agreement. This novel method can expand the indication of evaluating [Formula: see text].

Oxygen Consumption and Delivery in Critical Illness

This chapter evaluates the importance of identifying the oxygen delivery and oxygen consumption balance in critically ill patients. Mixed venous oxygen saturation is a valuable marker of oxygen consumption and delivery in an intensive care unit patient. Organ perfusion can be improved by optimizing all components of the oxygen delivery calculation and decreasing oxygen consumption, if indicated. Several tools that aid in this assessment include pulmonary artery catheter–derived mixed venous oxygen saturation, central venous line–derived central venous saturation, cardiac ultrasonography, and laboratory values such as the arterial blood gas and lactate levels. The chapter also discusses hyperlactatemia. Hyperlactatemia can be due to anaerobic metabolism (type A lactic acidosis) or aerobic metabolism (type B lactic acidosis).