SvO2 Values Research Articles

Investigation of a Novel Noninvasive Risk Analytics Algorithm With Laboratory Central Venous Oxygen Saturation Measurements in Critically Ill Pediatric Patients.

Accurate assessment of oxygen delivery relative to oxygen demand is crucial in the care of a critically ill patient. The central venous oxygen saturation (Svo2) enables an estimate of cardiac output yet obtaining these clinical data requires invasive procedures and repeated blood sampling. Interpretation remains subjective and vulnerable to error. Recognition of patient's evolving clinical status as well as the impact of therapeutic interventions may be delayed. The predictive analytics algorithm, inadequate delivery of oxygen (IDo2) index, was developed to noninvasively estimate the probability of a patient's Svo2 to fall below a preselected threshold. A retrospective multicenter cohort study was conducted using data temporally independent from the design and development phase of the IDo2 index. A total of 20,424 Svo2 measurements from 3,018 critically ill neonates, infants, and children were retrospectively analyzed. Collected data included vital signs, ventilator data, laboratory data, and demographics. The ability of the IDo2 index to predict Svo2 below a preselected threshold (30%, 40%, or 50%) was evaluated for discriminatory power, range utilization, and robustness. Area under the receiver operating characteristic curve (AUC) was calculated for each index threshold. Datasets with greater amounts of available data had larger AUC scores. This was observed across each configuration. For the majority of thresholds, Svo2 values were observed to be significantly lower as the IDo2 index increased. The IDo2 index may inform decision-making in pediatric cardiac critical care settings by providing a continuous, noninvasive assessment of oxygen delivery relative to oxygen demand in a specific patient. Leveraging predictive analytics to guide timely patient care, including support for escalation or de-escalation of treatments, may improve care delivery for patients and clinicians.

Discrepancy Between Pulmonary Artery Catheter and Co-Oximeter Value of Mixed Venous Oxygen Saturation After Graft Reperfusion During Living Donor Liver Transplantation

Monitoring tissue oxygenation is critical in liver recipients. The pulmonary artery catheter (PAC) provides continuous monitoring of mixed venous oxygen saturation (SvO2) using fiberoptic reflectance spectrophotometry. Despite the need for in vivo calibration during liver transplantation, recalibration guidelines are absent, and we frequently observed a significant discrepancy between PAC and reference co-oximeter SvO2 values after graft reperfusion. This study aimed to assess the incidence and risk factors of a significant discrepancy after reperfusion during living donor liver transplantation. This retrospective study included 54 recipients who underwent living donor liver transplantation at our institution between October 2021 and April 2022. A PAC was inserted, and in vivo calibration was conducted using the co-oximeter SvO2 value. We defined a significant discrepancy as a drift was ≥ 3% at 1 hour after reperfusion. Logistic regression analysis was performed to determine the association between perioperative variables and the risk of significant discrepancy. PAC SvO2 was higher than co-oximeter SvO2 in 51 recipients. A significant discrepancy was observed in 37 recipients (68.5%). The risk of significant discrepancy decreased with a high preoperative hemoglobin concentration (odds ratio [OR] = 0.65 [0.47-0.91], P = .011) and a high arterial oxygen partial pressure (PaO2) at 1 hour after reperfusion (OR = 0.96 [0.94-0.99], P = .004) but increased with a high baseline co-oximeter SvO2 value (OR = 1.29 [1.05-1.59], P = .015). PAC SvO2 significantly drifted from the reference co-oximeter value in over two-thirds of recipients after reperfusion. Therefore, in vivo recalibration is required for the reliable measurement of PAC SvO2 during living donor liver transplantation.

Comparison of Mixed Venous Oxygen Saturation and Premembranous Venous Oxygen Saturation in Patients on Peripheral Venous-Arterial Extracorporeal Membrane Oxygenation.

In patients on veno-arterial extracorporeal membrane oxygenation (ECMO) premembranous venous oxygen saturation (Spm-vO2) is continuously displayed on the ECMO console. However, the concordance between Spm-vO2 and mixed venous oxygen saturation (SvO2) remains largely unexplored. Our single-center retrospective study included adult patients who had paired SvO2 and Spm-vO2 readings within 15 minutes of each other, on peripherally cannulated Vf ivc-A ECMO and a pulmonary artery using catheter (PAC). The 82 pairs of observations showed a mean difference of 11.37% (95% limits of agreement -6.0 to 28.74, p < 0.001) between Spm-vO2 and SvO2. Although the two values correlated with each other (r = 0.51, p < 0.01), the difference between the paired measurements was larger at lower values of SvO2 (3.72 ± 6.38% when SvO2 >80%, 11.79±7.46% when SvO2 between 60% and 80%, and 18.81±12.09% when SvO2 <60%). The equation SvO2 = 1.2* Spm-vO2 - 28.03 was obtained by Passing Bablok regression. Cardiac index calculated by Spm-vO2 and SvO2 differed by 0.8L/minute/m2 (95% limits of agreement -0.52 to 2.17, p < 0.001). In peripheral VA-ECMO, Spm-vO2 is consistently higher than SvO2, with more discordance at lower saturation levels. Using Spm-vO2 to estimate cardiac output using Fick method yields inaccurate results.

Results of long-term riociguat therapy, including a switching strategy from sildenafil, in patients with pulmonary hypertension of various genesis

Aim: to study the influence of riociguat on the functional and hemodynamic status, remodeling of the right heart, as well as the safety of therapy in both previously untreated patients with idiopathic pulmonary arterial hypertension (IPAH) and inoperable chronic thromboembolic PH (CTEPH), and those not achieved treatment goals with sildenafil therapy and switching to riociguat.Materials and methods. A total of 161 pts with precapillary PH were included in the study; 137 pts completed the three-year observation period. Of 55 IPAH pts riociguat was started after diagnosis verification in 39 pts (subgroup 1); 16 pts previously taking sildenafil who did not achieve treatment goals comprised subgroup 2 of switching to riociguat. Of 82 inoperable CTEPH pts riociguat was started in 45 naїve pts; a switching strategy riociguat was implemented in 37 pts after 24-hour withdrawal of sildenafil. The dose titration of riociguat was started from 1 mg TID according to the standard algorithm up to 7.5 mg/day. By month 36 92.4% and 94.8% of pts with IPAH and CTEPH, respectively, received 7.5 mg/day. At baseline, at month 12, 24 and 36 all pts underwent a 6-minute walking test (6MWT) with the assessment of the dyspnea index according to the Borg scale and SpO2, echocardiography (Echo), right heart catheterization (RHC), and the safety profile was assessed.Results. At baseline, the proportion of pts with FC III-IV in CTEPH group compared to IPAH group, was significantly higher (70.7% vs 41.8%)); the distance in T6MX (d6MWT) was 291 [232;385] m vs 379 [300;448] m (p&lt;0.001). CTEPH pts had lower values of sPAP, PVR, SaO2 and SvO2 assessed by RHC. In the switching subgroups 2 of pts with IPAH and CTEPH, achieved levels of sPAP (p=0.01), sRAP (p=0.001) and PVR (p=0.01) (RHC) were significantly lower than in subgroups 1. The baseline levels of CI and SV were significantly higher in subgroups 2 (p&lt;0.05). During riociguat treatment in both subgroups of IPAH, a significant increase in d6MWT was achieved by 6 months with FC I-II (WHO) in 75% and 70% of patients. In the subgroup 1 to 36 months the greatest increase by 97m was achieved; in the switching subgroup the increase in d6MWT was noticed by month 6, which was maintained by month 36. In CTEPH patients, there was a significant improvement in FC (p=0.001) with ∆dT6MX 48m (p=0.001). In subgroup 1 with CTEPH, the d6MWT increase was 68.2m (p = 0.001), reaching 82.6m by month 36. In subgroup 2 the significant change of d6MWT were noted by the 1st year of FU, reaching 136.6m by month 36. In IPAH and CTEPH pts by month 36 of riociguat therapy, a significant decrease of mPAP, SPAP were found by echo, which was confirmed by RHC; there was a decrease in the basal size of the right ventricle (RV) (p=0.04) and an increase in RV FAC (p=0.04 and p=0.03, respectively). In subgroups 1, ∆SvO2 in ts with IPAH and CTEPH were significantly higher compared to subgroups 2. During FU period the proportion of low-risk pts increased to 26.7% in IPAH group and 44.8% in CTEPH group at month 36. In subgroups 2 riociguat therapy resulted in maintenance of treatment regimens throughout the year. Only 6.2% of pts by month 24 and 36 required the prescription of a 3d specific drug. No serious adverse events (AEs) were observed during treatment. The most common AEs were nasopharyngitis, nasal congestion, and dyspnea.Conclusions: Riociguat therapy for 36 months demonstrated a persistent positive effect on the functional and hemodynamic status, remodeling of the right heart both in previously untreated patients with IPH and inoperable CTEPH, and in patients from the switching groups who did not achieve treatment goals with sildenafil therapy.

Unresponsive Low Mixed Venous Oxygen Saturation During Early Intensive Care Unit Stay is Associated With Increased Risk of Organ Dysfunction After Cardiac Surgery: A Single-Center Retrospective Study

The aim of the study was to determine if unresponsive mixed venous oxygen saturation (SvO2) values during early postoperative hours are associated with postoperative organ dysfunction. A single-center retrospective observational study. A university hospital. A total of 6,282 adult patients requiring cardiac surgery who underwent surgery in a University Hospital from 2007 to 2020. A pulmonary artery catheter was used to gather SvO2 samples after surgery at admission to the intensive care unit (ICU) and 4 hours later. For the analysis, patients were divided into 4 groups according to their SvO2 values. The rate of organ dysfunctions categorized according to the SOFA score was then studied among these subgroups. The crude mortality rate for the cohort at 1 year was 4.3%. Multiple organ dysfunction syndrome (MODS) was present in 33.0% of patients in the early postoperative phase. During the 4-hour initial treatment period, 43% of the 931 patients with low SvO2 on admission responded to goal-directed therapy to increase SvO2 >60%; whereas, in 57% of the 931 patients, the low SvO2 was sustained. According to the adjusted logistic regression analyses, the odds ratio for MODS (4.23 [95% CI 3.41-5.25]), renal- replacement therapy (4.97 [95% CI 3.28-7.52]), time on a ventilator (2.34 [95% CI 2.17-2.52]), and vasoactive-inotropic score >30 (3.62 [95% CI 2.96-4.43]) were the highest in the group with sustained low SvO2. Patients with SvO2 <60% at ICU admission and 4 hours later had the greatest risk of postoperative MODS. Responsiveness to a goal-directed therapy protocol targeting maintaining or increasing SvO2 ≥60% at and after ICU admission may be beneficial.

Serial assessments of cardiac output and mixed venous oxygen saturation in comatose patients after out-of-hospital cardiac arrest

AimTo assess the association with outcomes of cardiac index (CI) and mixed venous oxygen saturation (SvO2) in comatose patients resuscitated from out-of-hospital cardiac arrest (OHCA).MethodsIn the cohort study of 789 patients included in the “BOX”-trial, 565 (77%) patients were included in this hemodynamic substudy (age 62 ± 13 years, male sex 81%). Pulmonary artery catheters were inserted shortly after ICU admission. CI and SvO2 were measured as soon as possible in the ICU and until awakening or death. The endpoints were all-cause mortality at 1 year and renal failure defined as need for renal replacement therapy.ResultsFirst measured CI was median 1.7 (1.4–2.1) l/min/m2, and first measured SvO2 was median 67 (61–73) %. CI < median with SvO2 > median was present in 222 (39%), and low SvO2 with CI < median was present in 59 (11%). Spline analysis indicated that SvO2 value < 55% was associated with poor outcome. Low CI at admission was not significantly associated with mortality in multivariable analysis (p = 0.14). SvO2 was significantly inversely associated with mortality (hazard ratioadjusted: 0.91 (0.84–0.98) per 5% increase in SvO2, p = 0.01). SvO2 was significantly inversely associated with renal failure after adjusting for confounders (ORadjusted: 0.73 [0.62–0.86] per 5% increase in SvO2, p = 0.001). The combination of lower CI and lower SvO2 was associated with higher risk of mortality (hazard ratioadjusted: 1.54 (1.06–2.23) and renal failure (ORadjusted: 5.87 [2.34–14.73].ConclusionFirst measured SvO2 after resuscitation from OHCA was inversely associated with mortality and renal failure. If SvO2 and CI were below median, the risk of poor outcomes increased significantly.RegistrationThe BOX-trial is registered at clinicaltrials.gov (NCT03141099, date 2017–30–04, retrospectively registered).Graphical abstract

Association of low mixed venous oxygen saturations during early ICU stay with increased 30-day and 1-year mortality after cardiac surgery: a single-center retrospective study

BackgroundLow postoperative mixed venous oxygen saturation (SvO2) values have been linked to poor outcomes after cardiac surgery. The present study was designed to assess whether SvO2 values of < 60% at intensive care unit (ICU) admission and 4 h after admission are associated with increased mortality after cardiac surgery.MethodsDuring the years 2007–2020, 7046 patients (74.4% male; median age, 68 years [interquartile range, 60–74]) underwent cardiac surgery at an academic medical center in Finland. All patients were monitored with a pulmonary artery catheter. SvO2 values were obtained at ICU admission and 4 h later. Patients were divided into four groups for analyses: SvO2 ≥ 60% at ICU admission and 4 h later; SvO2 ≥ 60% at admission but < 60% at 4 h; SvO2 < 60% at admission but ≥ 60% at 4 h; and SvO2 < 60% at both ICU admission and 4 h later. Kaplan–Meier survival curves, Cox regression models, and receiver operating characteristic curve analysis were used to assess differences among groups in 30-day and 1-year mortality.ResultsIn the overall cohort, 52.9% underwent coronary artery bypass grafting (CABG), 29.1% valvular surgery, 12.1% combined CABG and valvular procedures, 3.5% surgery of the ascending aorta or aortic dissection, and 2.4% other cardiac surgery. The 1-year crude mortality was 4.3%. The best outcomes were associated with SvO2 ≥ 60% at both ICU admission and 4 h later. Hazard ratios for 1-year mortality were highest among patients with SvO2 < 60% at both ICU admission and 4 h later, regardless of surgical subgroup.ConclusionSvO2 values < 60% at ICU admission and 4 h after admission are associated with increased 30-day and 1-year mortality after cardiac surgery. Goal-directed therapy protocols targeting SvO2 ≥ 60% may be beneficial. Prospective studies are needed to confirm these observational findings.

Spectrum Medical Quantum or Terumo CDI 500: Which Device Measures Hemoglobin and Oxygen Saturation Most Accurately When Compared to a Benchtop Blood Analyzer?

To examine the accuracy between analyzers, the Terumo CDI 500 and the Spectrum Medical Quantum were compared to each other and to the ABL90 FLEX benchtop blood analyzer. Patients were retrospectively identified who underwent cardiac surgery requiring cardiopulmonary bypass between August 1, 2018 and November 1, 2019. Hemoglobin and venous saturation (SvO2) values from all three analyzers were collected. Measurements from the Quantum and the CDI 500 were averaged over 1 minute to provide a single value for the minute for the given device. Blood analysis on the ABL90 benchtop device was performed at a minimum of every hour during congenital cardiopulmonary bypass (CPB). There were 519 patients included in the analysis. Data points numbering 69,404 and 70,598 were analyzed when comparing the CDI 500 to the Quantum for hemoglobin and SvO2, respectively. Comparison of hemoglobin and SvO2 for the CDI 500 and Quantum versus ABL90 used 2283 and 1414 data points respectively, in each group. The CDI 500 and Quantum reported hemoglobin within 1 g/dL of the ABL90 86.9% and 87.5% of the time, respectively. The CDI 500 and Quantum reported SvO2 within 3% of the ABL90 61.0% and 57.9% of the time, respectively. The mean difference between the CDI 500 and Quantum hemoglobin and SvO2 measurements equaled .194 g/dL (p < .001) and .861% (p < .001), respectively and were both significantly different from zero. All device comparisons were statistically significantly different when compared to zero difference, likely due to the large data set as the magnitudes of these differences are all quite small and may not be clinically significant. However, while the reader should judge for themselves based upon their specific practice, in our opinion, the 95% Limit of Agreement was too large for either the CDI 500 or Quantum hemoglobin and SvO2 values to be substituted for ABL90 values. As recommended by the manufacturers, the CDI 500 and Quantum should only be used as a trending device.

Estimating cerebral venous oxygenation in human fetuses with ventriculomegaly using quantitative susceptibility mapping

Rationale and objectivesThe goal of this study was to estimate venous blood oxygen saturation (SvO2) in the superior sagittal sinus (SSS) in fetal brains with ventriculomegaly (VM) using quantitative susceptibility mapping (QSM). Materials and methodsA radiofrequency spoiled gradient echo sequence was used to evaluate data on 19 fetuses with VM (gestational age(GA): median = 29.9 weeks (range 23 to 37.3 weeks)) and 20 healthy fetuses (GA: median = 30.9 (range 22.7 to 38.7 weeks)) at 1.5 T. Susceptibility weighted images encompassing the entire fetal brain were acquired within 1 min. An iterative, geometry constraint-based thresholded k-space division algorithm was used for generating QSM data of the fetal brain. The venous oxygen saturation was calculated using the magnetic susceptibility of the SSS obtained from the QSM data. Mixed-model analysis of variance and interobserver variability assessment were used to analyze the results. ResultsThe median SvO2 values in the entire VM cohort as well as for second and third trimester fetuses (with interquartile range) were: 67.8% (63.2%, 73.6%), 73.1% (69.1%, 77.3%) and 63.8% (59.4%, 68.1%), respectively. The corresponding median SvO2 value in the healthy control group was: 65.3% (58.3%, 68.2%), 67.5% (61.7%, 69.2%) and 60.8% (53.6%, 68.2%), respectively. However, the difference of SvO2 between VM and control groups was not significant at the p = 0.05 level (p = 0.076). The SvO2 was found decreasing significantly with GA in the healthy control group (p < 0.05). ConclusionsWe report for the first time the estimation of cerebral SvO2 in human fetuses with VM using QSM. This measure of oxygen saturation might be beneficial in assessing and monitoring the metabolic status of the fetus in various clinical conditions.

A Descriptive Study of Perioperative Hemodynamics in Open Cardiac Surgery Patients

The purpose of the present study was to describe how the perioperative hemodynamic profile before and after cardiopulmonary bypass during cardiac surgery is influenced by age and to describe the association between postoperative hemodynamics and one-year mortality. A retrospective registry-based study. University Hospital of Aarhus, Denmark. The study comprised 6,595 patients undergoing elective on-pump cardiac surgery from 2006 to 2016. Perioperative hemodynamic values were derived from computerized anesthesia and intensive care reports, including mean arterial pressure, cardiac index, and oxygenation saturation from mixed venous blood in the pulmonary artery, during the perioperative period. Perioperative hemodynamic values were stratified according to age. Logistic regression was applied to predict the crude probability of death within one year from surgery according to hemodynamic values at six hours after surgery, stratified by age and use of inotropic agents, respectively. Lower values for cardiac index and mixed venous blood in the pulmonary artery with increasing age, across all points in time in the perioperative course, were observed. Higher probability of death was associated with lower hemodynamic values in the postoperative phase, and the probability of death was modified by age and the need for inotropic agents. This is a large registry based study describing the perioperative hemodynamic profile of patients undergoing cardiac surgery and the results enhance our understanding of age-differentiated values of CI and SvO2 in this specific population.

A Continuous Noninvasive Method to Assess Mixed Venous Oxygen Saturation: A Proof-of-Concept Study in Pigs.

Mixed venous oxygen saturation (Svo2) is important when evaluating the balance between oxygen delivery and whole-body oxygen consumption. Monitoring Svo2 has so far required blood samples from a pulmonary artery catheter. By combining volumetric capnography, for measurement of effective pulmonary blood flow, with the Fick principle for oxygen consumption, we have developed a continuous noninvasive method, capnodynamic Svo2, for assessment of Svo2. The objective of this study was to validate this new technique against the gold standard cardiac output (CO)-oximetry Svo2 measurement of blood samples obtained from a pulmonary artery catheter and to assess the potential influence of intrapulmonary shunting. Eight anesthetized mechanically ventilated domestic-breed piglets of both sexes (median weight 23.9 kg) were exposed to a series of interventions intended to reduce as well as increase Svo2. Simultaneous recordings of capnodynamic and CO-oximetry Svo2 as well as shunt fraction, using the Berggren formula, were performed throughout the protocol. Agreement of absolute values for capnodynamic and CO-oximetry Svo2 and the ability for capnodynamic Svo2 to detect change were assessed using Bland-Altman plot and concordance analysis. Overall bias for capnodynamic versus CO-oximetry Svo2 was -1 percentage point (limits of agreement -13 to +11 percentage points), a mean percentage error of 22%, and a concordance rate of 100%. Shunt fraction varied between 13% at baseline and 22% at the end of the study and was associated with only minor alterations in agreement between the tested methods. In the current experimental setting, capnodynamic assessment of Svo2 generates absolute values very close to the reference method CO-oximetry and is associated with 100% trending ability.

Measurements of venous oxygen saturation in the superior sagittal sinus using conventional 3D multiple gradient-echo MRI: Effects of flow velocity and acceleration.

This work investigates the effects of flow acceleration in the superior sagittal sinus on slice-dependent variations in venous oxygen saturation (SvO2 ) estimations using susceptibility-based MR oximetry. Three-dimensional multiple gradient-echo images, with first-order flow compensation along the anterior-posterior readout direction for the first echo, were acquired twice from 15 healthy volunteers. For all slices, phases within the superior sagittal sinus were fitted using linear regression across four TEs to obtain the Pearson's correlation coefficients (PCCs), the largest of which corresponded to minimum acceleration influence. SvO2 derived from odd echoes on this slice was used to assess interscan difference, and compared with the central 15th slice for slice-dependent difference, both using Bland-Altman analysis. Within-scan interslice SvO2 consistency was examined versus PCC. Multislice-averaged SvO2 values were then computed from slices with PCCs above a certain threshold. Slice-dependent difference in SvO2 varied from -16.2% to 21.5% at two SDs, in agreement with a recent report, and about twice larger than interscan differences for the automatically selected slice (-7.5% to 10.3%) and for the central 15th slice (-8.0% to 8.8%). For slices with PCCs higher than -0.98, interslice SvO2 deviations were all found to be less than 5.0%. Multislice-averaged SvO2 with PCCs higher than -0.98 further reduced interscan difference to -4.7% to 8.2%. Slice-dependent variations in SvO2 may partly be explained by the effects of flow acceleration. Our method may enable conventional 3D multiple gradient echo to be used for SvO2 estimations in the presence of pulsatile flow.

Extracorporeal Life Support Organization (ELSO): Guidelines for Neonatal Respiratory Failure.

Extracorporeal Life Support Organization (ELSO): Guidelines for Neonatal Respiratory Failure.

Retinal oxygen saturation in 1461 healthy children aged 7-19 and its associated factors.

PurposeThe aim of the present study was to investigate age‐specific normative retinal oxygen saturation values and explore the associated factors in healthy Chinese school‐aged children with different refractive statuses.DesignPopulation‐based observational cross‐sectional study.MethodsChildren aged 7–19 years were enrolled. Each participant underwent a series of comprehensive ocular examinations, including axial length (AL), cycloplegic refraction and Oxymap T1 imagery following cycloplegia. The acquired oximetry images were measured, and the values of the retinal oxygen saturation parameters were calculated. The independent factors of the retinal oxygen saturation were analysed using multiple linear regression. The oxygen saturation of retinal arteries (SaO2) and veins (SvO2) as well as the differences between the arteries and veins (AVD) were measured as the main outcomes.ResultsIn total, 1461 participants were included in the study. The mean age of the participants was 12.1 ± 3.2 years, and 53.0% were boys. The mean SaO2, SvO2 and AVD values were 83.7 ± 6.4%, 50.1 ± 5.4% and 33.6 ± 5.4%, respectively, and the values increased with age. Girls had higher SvO2 and lower AVD than boys (p < 0.05). The Pearson correlation coefficients among spherical equivalent (SE) and SaO2, SvO2 and AVD were −0.372, −0.203 and −0.240, respectively (all p < 0.001), while the correlations between AL and SaO2, SvO2 and AVD were 0.276, 0.106 and 0.221, respectively (all p < 0.001). The myopia group had significantly higher SaO2, SvO2 and AVD than the emmetropia and hyperopia groups (p < 0.001), but the high myopia group had lower SaO2 and SvO2 than the moderate myopia group. When age, gender, body mass index (BMI), intraocular pressure (IOP) and axial length (AL) were included as factors in the multiple regression, older age was associated with higher SaO2, SvO2 and AVD, while longer AL was associated with higher SaO2 and AVD. Gender was an independent factor predicting SvO2, while gender and BMI were the independent factors predicting AVD. Age explained more variance than AL in SaO2, SvO2 and AVD.ConclusionsOur population‐based study provides age‐specific profiles of retinal oxygen saturation in Chinese children and adolescents. Older age and longer AL were important independent factors of increased retinal oxygen saturation.

Mixed Venous Oxygen Saturation during the Transcatheter Aortic Valve Replacement—A Prospective Cohort Study

Purpose: Patients scheduled to undergo the transcatheter aortic valve replacement (TAVR) are usually octogenarians with severe co-morbidities and an increased risk of surgery-associated complications. The aim of this study was to determine the incidence of insufficient oxygen delivery as measured by mixed venous oxygen saturation (SvO2) via invasive continuous cardiopulmonary monitoring and the low cardiac output syndrome (LCOS) in patients undergoing the TAVR procedure. The second objective was to examine how these hemodynamic measurements would change during critical events, such as rapid ventricular pacing (RVP) during this procedure. Methods: This prospective, observational study, examined twenty patients undergoing TAVR under general anesthesia. Hemodynamic variables, SvO2 and the continuous cardiac output (CO) were assessed using pulmonary artery catheter (PAC) and a Vigilance® monitor. Insufficient oxygen delivery was defined as a SvO2 value under 58% and LCOS as a cardiac index (CI) under 2 L/min/m2. Total intravenous anesthesia and hemodynamic management protocol were standardized. RVP was induced twice during the procedure at a frequency of 180 - 200/min. Predefined clinical endpoints were assessed during the procedure and hemodynamic values were analyzed before and after twelve critical events. Results: The data of twenty patients with a mean age of 80 ± 4 years and EuroSCORE 18 ± 10 were analyzed. Fourteen (70%) of the TAVR procedures were performed transapically, the other six (30%) transfemorally. The SvO2 value under 58% (mean 54 ± 6) and the CI under 2 L/min/m2 (mean 1.6 ± 0.2) were detected in 60% of patients (n = 12) before the use of RVP. All of these patients received perioperative inotropic medication and required norepinephrine infusion for maintenance of adequate blood pressure. The SvO2, CO and CI were significantly decreased after the use of RVP (P 2 reverted rapidly to the same level as before the application of RVP (1 min), CO, and CI 10 min later. At the end of the operation SvO2 values were at same level as before RVP and CO and CI were higher than before RVP. Conclusion: A high incidence of insufficient oxygen delivery and low cardiac output syndrome were detected in patients undergoing TAVR procedures. Nonetheless, all hemodynamic values returned rather rapidly to the same level as before the use of the RVP and were at the optimal level at the end of the procedure. According to the current study, the most hemodynamically hazardous steps during TAVR are the use of RVP sequences, the induction of anesthesia and the initiation of surgery.

Measurement and correction of the bulk magnetic susceptibility effects of fat: application in venous oxygen saturation imaging.

To develop a correction method for the effects of the magnetic susceptibility of fat (χFat ) on the calculation of venous oxygen saturation (SvO2 ). The magnetic field shifts associated with the magnetic susceptibility of deoxyhemoglobin can be used to estimate SvO2 , a measure of oxygen extraction and metabolism. However, the distinct magnetic susceptibility of fat surrounding targeted veins will give rise to magnetic field perturbations that will extend into the vein and surrounding tissues, potentially confounding the calculation of SvO2 . Multi-echo modified Dixon fat-water separated imaging was used to quantify fat-water distributions around the superficial femoral vein (venous return from the lower leg). Fat fraction images were used to generate χFat images, to calculate and remove the associated fat-susceptibility-induced magnetic field shifts before the estimation of SvO2 . This approach was evaluated at rest and with plantar flexion exercise to evaluate calf muscle oxygen extraction in 10 healthy subjects. The presence of fat around the vein resulted in complex magnetic field shifts and errors in estimated SvO2 . Corrected resting SvO2 values were significantly larger than those measured with conventional methods, at rest (72.6 ± 11.0% vs. 65.2 ± 12.2%, P < 0.05) and post-exercise (37.4 ± 12.3% vs. 31.7 ± 12.7%, P < 0.05), with larger errors in individuals and/or regions with increased fat volumes. Estimation and removal of the field-effects from χFat enabled the use of fat tissues for the measurement and removal of the background magnetic field. The magnetic susceptibility effects of fat can confound SvO2 estimation, but the susceptibility field effects can estimated and removed with the use of modified Dixon fat-water separated imaging.

In vivo whole‐blood T2 versus HbO2 calibration by modulating blood oxygenation level in the femoral vein through intermittent cuff occlusion

To investigate the feasibility of estimating calibration constants (K and T2o ) in vivo for converting whole-blood T2 to blood hemoglobin oxygen saturation (HbO2 ) according to the Luz-Meiboom model, 1/T2=1/T2o+K(1-HbO2)2, where K and T2o are relaxivity and transverse relaxation time of fully saturated blood, respectively. A range of HbO2 values was achieved in the superficial femoral vein with intermittent cuff occlusion in seven healthy adults (four males) to establish a calibration curve between blood T2 and HbO2 at 1.5T. HbO2 was derived via MR susceptometry, a technique previously validated, and the transverse relaxation time was quantified with an optimized T2 -prepared balanced steady-state free precession pulse sequence. To evaluate the accuracy of the in vivo calibration method, T2 and HbO2 were quantified in the superior sagittal sinus in six additional subjects and compared with susceptometry. Two sets of gender-specific calibration constants were derived, one for each gender corresponding to hematocrits of 0.47 ± 0.02 for males and 0.38 ± 0.01 for females, yielding K/T2o = 41 Hz/260 ms and 26 Hz/280 ms, respectively. The in vivo calibration returned physiologically plausible superior sagittal sinus SvO2 values (65 ± 5% HbO2 ), and there was no significant difference between the results from the two methods (average difference -0.3% HbO2 ). The results show feasibility of performing in vivo calibration for converting whole-blood T2 to HbO2 . The proposed approach bypasses the involved and cumbersome processes associated with in vitro calibration. Magn Reson Med 79:2290-2296, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Proof of concept non-invasive estimation of peripheral venous oxygen saturation

BackgroundPulse oximeters continuously monitor arterial oxygen saturation. Continuous monitoring of venous oxygen saturation (SvO2) would enable real-time assessment of tissue oxygen extraction (O2E) and perfusion changes leading to improved diagnosis of clinical conditions, such as sepsis.MethodsThis study presents the proof of concept of a novel pulse oximeter method that utilises the compliance difference between arteries and veins to induce artificial respiration-like modulations to the peripheral vasculature. These modulations make the venous blood pulsatile, which are then detected by a pulse oximeter sensor. The resulting photoplethysmograph (PPG) signals from the pulse oximeter are processed and analysed to develop a calibration model to estimate regional venous oxygen saturation (SpvO2), in parallel to arterial oxygen saturation estimation (SpaO2). A clinical study with healthy adult volunteers (n = 8) was conducted to assess peripheral SvO2 using this pulse oximeter method. A range of physiologically realistic SvO2 values were induced using arm lift and vascular occlusion tests. Gold standard, arterial and venous blood gas measurements were used as reference measurements. Modulation ratios related to arterial and venous systems were determined using a frequency domain analysis of the PPG signals.ResultsA strong, linear correlation (r2 = 0.95) was found between estimated venous modulation ratio (RVen) and measured SvO2, providing a calibration curve relating measured RVen to venous oxygen saturation. There is a significant difference in gradient between the SpvO2 estimation model (SpvO2 = 111 − 40.6*R) and the empirical SpaO2 estimation model (SpaO2 = 110 − 25*R), which yields the expected arterial-venous differences. Median venous and arterial oxygen saturation accuracies of paired measurements between pulse oximeter estimated and gold standard measurements were 0.29 and 0.65%, respectively, showing good accuracy of the pulse oximeter system.ConclusionsThe main outcome of this study is the proof of concept validation of a novel pulse oximeter sensor and calibration model to assess peripheral SvO2, and thus O2E, using the method used in this study. Further validation, improvement, and application of this model can aid in clinical diagnosis of microcirculation failures due to alterations in oxygen extraction.

Accuracy of the Spectrum Medical M4 and Terumo CDI 500 compared to the Radiometer ABL90 FLEX benchtop blood analyzer.

The benchtop blood analyzer is the gold standard for blood oxygen saturation (SO2) and hemoglobin (Hb) analysis. However, the benchtop analyzer only provides values at a given point in time. In the field of cardiovascular perfusion and the practice of cardiopulmonary bypass (CPB), continuous measurement of SvO2 and hemoglobin values have become commonplace. Two devices currently available which monitor these values are the Terumo CDI 500 and Spectrum Medical M4. A retrospective study was conducted to examine the accuracy of the M4 technology and the CDI 500 as they compare to each other and the ABL90 FLEX, a benchtop blood gas analyzer. The data revealed the magnitude of mean differences were small, even when significant. However, the 95% Limits of Agreement were too large for either device to allow substitution of the CDI 500 and M4 hemoglobin or SvO2 values for ABL90 values. As recommended by the manufacturers, the CDI 500 and M4 should only be used as a trending device.

A new method for noninvasive venous blood oxygen detection.

BackgroundBlood oxygen saturation of vein (SvO2) is an important clinical parameter for patient monitoring. However, the existing clinical methods are invasive, expensive, which are also painful for patients.MethodsBased on light-absorption, this study describes a new noninvasive SvO2 measurement method by using external stimulation signal to generate cyclical fluctuation signal in the vein, which overcomes the low signal-to-noise ratio problem in the measurement process. In this way, the value of SvO2 can be obtained continuously in real time.ResultsThe experimental results demonstrate that the method can successfully measure venous oxygen saturation by artificial addition of stimulation. Under hypoxic conditions, the system can reflect the overall decline of venous oxygen saturation better. When the results measured by the new method are compared with those measured by the invasive method, the root mean square error of the difference is 5.31 and the correlation coefficient of the difference is 0.72. The new method can be used to measure SvO2 and evaluate body oxygen consumption, and its accuracy needs improvement.ConclusionsReal-time and continuous monitoring can be achieved by replacing invasive method with noninvasive method, which provides more comprehensive clinical information in a timely manner and better meet the needs of clinical treatment. However, the accuracy of the new noninvasive SvO2 measurement based on light-absorption has to be further improved.Electronic supplementary materialThe online version of this article (doi:10.1186/s12938-016-0208-8) contains supplementary material, which is available to authorized users.