Monitoring Of Mixed Venous Oxygen Saturation Research Articles

Management of Sepsis and Septic Shock: What Have We Learned in the Last Two Decades?

Sepsis is a clinical syndrome encompassing physiologic and biological abnormalities caused by a dysregulated host response to infection. Sepsis progression into septic shock is associated with a dramatic increase in mortality, hence the importance of early identification and treatment. Over the last two decades, the definition of sepsis has evolved to improve early sepsis recognition and screening, standardize the terms used to describe sepsis and highlight its association with organ dysfunction and higher mortality. The early 2000s witnessed the birth of early goal-directed therapy (EGDT), which showed a dramatic reduction in mortality leading to its wide adoption, and the surviving sepsis campaign (SSC), which has been instrumental in developing and updating sepsis guidelines over the last 20 years. Outside of early fluid resuscitation and antibiotic therapy, sepsis management has transitioned to a less aggressive approach over the last few years, shying away from routine mixed venous oxygen saturation and central venous pressure monitoring and excessive fluids resuscitation, inotropes use, and red blood cell transfusions. Peripheral vasopressor use was deemed safe and is rising, and resuscitation with balanced crystalloids and a restrictive fluid strategy was explored. This review will address some of sepsis management's most important yet controversial components and summarize the available evidence from the last two decades.

Capnodynamics - noninvasive cardiac output and mixed venous oxygen saturation monitoring in children.

Hemodynamic monitoring in children is challenging for many reasons. Technical limitations in combination with insufficient validation against reference methods, makes reliable monitoring systems difficult to establish. Since recent studies have highlighted perioperative cardiovascular stability as an important factor for patient outcome in pediatrics, the need for accurate hemodynamic monitoring methods in children is obvious. The development of mathematical processing of fast response mainstream capnography signals, has allowed for the development of capnodynamic hemodynamic monitoring. By inducing small changes in ventilation in intubated and mechanically ventilated patients, fluctuations in alveolar carbon dioxide are created. The subsequent changes in carbon dioxide elimination can be used to calculate the blood flow participating in gas exchange, i.e., effective pulmonary blood flow which equals the non-shunted pulmonary blood flow. Cardiac output can then be estimated and continuously monitored in a breath-by-breath fashion without the need for additional equipment, training, or calibration. In addition, the method allows for mixed venous oxygen saturation (SvO2) monitoring, without pulmonary artery catheterization. The current review will discuss the capnodyamic method and its application and limitation as well as future potential development and functions in pediatric patients.

Con: Continuous Cardiac Output and SvO2 Monitoring Are Not Routine In Off-Pump Coronary Artery Bypass Grafting

THE DEBATE REGARDING the routine use of continuous cardiac output (CCO) and mixed venous oxygen saturation (SvO2) monitoring for off-pump coronary artery bypass graft (OPCAB) surgeries relates to the question of whether increasing the degree and complexity of invasive monitoring will lead to improved outcomes. Many of the recent advances in cardiac output (CO) and SvO2 monitoring have shown promise, but their routine use in OPCAB surgery is limited mainly because of their inability to provide immediate and reliable hemodynamic data during periods of sudden hemodynamic instability.

Near-infrared spectroscopy cerebral and somatic (renal) oxygen saturation correlation to continuous venous oxygen saturation via intravenous oximetry catheter

PurposeNear-infrared spectroscopy (NIRS) and continuous central venous oxygen saturation (ScvO2) via oximetry catheter are 2 modalities available to estimate adequacy of oxygen delivery in postoperative pediatric cardiac patients. Near-infrared spectroscopy measures regional tissue oxygenation and is routinely used in pediatric cardiac surgery patients. By not requiring an invasive catheter, NIRS has the advantage over mixed venous oxygen saturation (SvO2) monitoring. An alternative marker of global tissue oxygenation is central venous oxygen saturation (ScvO2). A recently developed pediatric-sized oximetric catheter (PediaSat; Edwards Lifesciences, Irvine, CA, USA) functions as a central venous catheter and provides a continuous ScvO2 reading, an accepted surrogate to SvO2. To date, the correlation between NIRS and ScvO2 has not been quantified. The aim of this study was to examine the strength of the bivariate correlation between NIRS and ScvO2 measurements. Design/methodsTwenty pediatric patients undergoing cardiac surgery had the PediaSat catheter placed with the tip in the superior vena cava and NIRS sensors (cerebral and renal) placed in the operating room per routine protocol. Hourly measurements of NIRS-cerebral (NIRS-C), NIRS-renal, and ScvO2 readings were recorded for each patient for up to 48 hours postoperatively. ResultsA cumulative total of 630 hours of data were collected. Spearman correlation coefficients for NIRS-renal vs ScvO2 and NIRS-C vs ScvO2 measurements were r = 0.38 (P = .09) and r = 0.58 (P < .008), respectively. ConclusionsIn this small cohort of pediatric patients undergoing heart surgery, there was a moderate but statistically significant correlation between the ScvO2-catheter and the NIRS-C values. Further studies are required to determine which oxymetric modality of monitoring cardiac output most aids in the postoperative management of these patients.

Continuous mixed venous and central venous oxygen saturation in cardiac surgery with cardiopulmonary bypass

Replacing mixed venous oxygen saturation (SvO2) monitoring by central venous oxygen saturation (ScvO2) monitoring in order to avoid the use of a pulmonary artery catheter and its related complications is still controversial in the setting of cardiac surgery. The influence of surgery, cardiopulmonary bypass and anaesthesia drugs on the relationship between SvO2 and ScvO2 has never been studied. Fifteen patients scheduled for cardiac surgery with cardiopulmonary bypass were included in the study. SvO2 (from the pulmonary artery) and ScvO2 (from the superior vena cava) were continuously measured with fibre-optic catheters from induction of anaesthesia to 24 h postoperatively. A total of 9267 pairs of measurements were recorded. Mean bias between SvO2 and ScvO2 was 4.4% with limits of agreement of -13.6 and +22.5%, respectively. Trends of SvO2 and ScvO2 values followed very different patterns for some patients. Surgery, cardiopulmonary bypass and anaesthesia drugs did not influence the relationship between the two methods. Because of the large interindividual variability in the difference between SvO2 and ScvO2, the measure of ScvO2 should not replace the measure of SvO2 with a pulmonary artery catheter for the management of patients undergoing cardiac surgery with cardiopulmonary bypass.

Prehospital monitoring in resuscitation : today and the future

There is growing evidence that early detection and response to physiological deterioration can improve outcome for patients. Working out-of-hospital, we often find ourselves in diagnostic dilemmas, thus more reliable data could change our actions as well as give better assessment of patient's condition. Therefore, we are always exploring new perspectives that could be transferred from experimental laboratory settings to our primary working area in the field to help us improve decision-making leading to better outcome. In the following sections, we represent our previous studies about the utility of continuous capnometry and the importance of point-of-care ultrasound in cardiopulmonary resuscitation (CPR), and dis-cuss about the possible future use of transthoracic and transesophageal ultrasound, point-of-care biochemical monitoring, tissue oxygen saturation, pupillometry, and mixed and central venous oxygen saturation monitoring in the prehospital setting.

Mixed venous oxygen saturation monitoring in calcium channel blocker poisoning: tissue hypoxia avoidance despite hypotension

Mixed venous oxygen saturation monitoring in calcium channel blocker poisoning: tissue hypoxia avoidance despite hypotension

The Pulmonary Artery Catheter: Gold Standard or Redundant Relic

Pulmonary artery catheter (PAC) technology has changed significantly and use has decreased over the last 20 years. Barriers to use include: (a) increased patient risk with placement; (b) ability to measure similar variables via less invasive measures; (c) increased cost; (d) inaccurate measurement leading to misuse of PAC-derived variables; (e) incorrect interpretation and clinical application; and (f) lack of proven benefit for patient management. Advances in technology have allowed for continuous trending of hemodynamic parameters measured via the PAC. Patient risk is similar to that of central line placement; however risks associated with pulmonary artery infarction and rupture are inherent to the PAC. Less invasive assessment of cardiac output equals that of the PAC, whereas pulmonary capillary wedge pressure and mixed venous oxygen saturation monitoring are unique features of the PAC. Effective use of PAC data will require ongoing standardized education. More studies are needed on the cost-effectiveness of PAC monitoring as well as outcome benefits. Much of the data available from the PAC can be obtained via less invasive methods. However, the PAC continues to be useful in specific situations and remains the gold standard for comparison of new technologies. This paper discusses use of the PAC during the past 2 decades and reviews studies affecting its use in clinical practice.

A Pilot Study of Continuous Transtracheal Mixed Venous Oxygen Saturation Monitoring

In this study, we investigated the feasibility and the accuracy of transtracheal mixed venous oxygen saturation (Svo(2)) monitoring. Ten patients undergoing thoracic surgery were included in this study. A single-use pediatric pulse oximetry sensor was attached to the double-lumen tube between the tracheal and bronchial cuff. After anesthesia was induced, the double-lumen tube was inserted into the trachea and adjusted to the proper position. During surgery, the pulmonary arterial blood was sampled every 3 min for 15 min to measure the Svo(2). The measurements made by the transtracheal pulmonary pulse oximeter (Sto(2)) were recorded at the same time that blood was sampled from the pulmonary artery for Svo(2) measurements. The levels of measurement agreement between the Sto(2) and the Svo(2) were analyzed using the Bland and Altman method. The mean +/- sd (range) oxygen saturation values during the data collecting period were 82.0% +/- 4.9% (72%-91%) for the Sto(2) and 82.2% +/- 5.5% (71%-91%) for the Svo(2), respectively. The linear correlation coefficient of the regression analysis between the Sto(2) and the Svo(2) was 0.934 (P < 0.05). A 95% confidence interval for absolute difference between the Sto(2) and the Svo(2) was 1.58%-2.09%. The mean +/- 2 sd difference between the Sto(2) and the Svo(2) was 0.12% +/- 3.97% on the Bland and Altman graph. We conclude that it is feasible to monitor the pulmonary artery oxygen saturation continuously by a transtracheal pulse oximetry technique and that it can be done so accurately. Mixed venous oxygen saturation (Svo2) is a measure of the balance between oxygen supply and consumption throughout the whole body. Svo2 can be measured invasively by inserting a pulmonary artery catheter with the associated disadvantages of cost and potential for patient injury. In this study, we investigated the feasibility of noninvasive Svo2 measurement using a transtracheal pulse oximetry technique.

Postoperative management: The role of mixed venous oxygen saturation monitoring

The results of the Norwood operation have improved considerably over the last decade, due in part to improvement in postoperative care. Mixed venous oxygen saturation (MvO2) monitoring has been an important addition to postoperative management. Our use of MvO2 monitoring in Norwood patients has included 96 infants operated from 1996 to the present. This strategy has proven to be technically straightforward and adds information not provided by monitoring systemic saturation alone. MvO2 has a nadir at 6-12 hours after surgery and below a value of 30% is associated with anaerobic metabolism. It identifies patients at risk for early mortality. It also allows evaluation of management of treatment strategies that evolve over time and of specific interventions in individual patients. Optimizing MvO2 constitutes an important goal of postoperative management after the Norwood procedure.

The Hemodynamic Effects of MgSO4 during Coronary Artery Bypass Surgery with Cardiopulmonary Bypass

Background: Reperfusion injury often develops after cardiopulmonary bypass (CPB) during coronary artery bypass grafting (CABG), and is known to be related to such injury. The goal of this study was to determine the hemodynamic and oxygen metabolic effects of administering after cessating cardiopulmonary bypass during coronary bypass surgery in control and nicardipine infusion groups. Methods: After obtaining hospital ethics committee clearance, we studied 29 patients with coronary artery disease scheduled for CABG, who were randomly assigned to receive nicardipine (0.5/kg/min, n = 11) or placebo (n = 18). All patients were administered TEX>$MgSO_4$ (60 mg/kg) after the cessation of CPB. The hemodynamic variables and oxygen parameters were recorded and calculated by continuous cardiac output and mixed venous oxygen saturation monitoring, through a thermodilution Swan-Ganz catheter before and 20 minutes after administration. Results: Heart rate was reduced after administering in both groups, and the mean arterial pressure was also reduced in the nicardipine group. The cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, right and left stroke work indices were well-maintained after administering . Mixed venous oxygen saturation and other oxygen parameters were maintained without change after administration. Conclusions: The present study shows that can be used without inducing any significant oxygen metabolism or hemodynamic derangements during CABG. But further work is needed to elucidate the myocardial protective effects of .

Follow-up article needed on ABG analysis

I read with great interest the article, “Assessing Tissue Oxygenation,” in the June 2002 issue (June 2002:22–40). This article provided an excellent review of acid-base physiology and arterial blood gas interpretation.I would love to see a follow-up article that addresses the critical physiological concepts that form the interface of clinical shock states and dysregulation of gas and nutrient exchange at the tissue level. A review of the utilization of additional technologies such as mixed venous oxygen saturation monitoring, serum lactate assays, and therapeutic modalities to correct hypoperfusion would be most helpful.

A Study on the Monitoring of Bupivacaine-induced Cardiac Depression in Dogs: A Comparison between Continuous Mixed Venous Oxygen Saturation and Mean Arterial Blood Pressure

Background: Bupivacaine induces cardiac depression, which is resistant to treatment. Therefore early recognition of its development is important so that the injection of bupivacaine can be discontinued promptly. We compared the efficacy of continuous mixed venous oxygen saturation (cSvO2) monitoring with that of the mean arterial blood pressure (MBP) monitoring in terms of the prediction of cardiac output (CO) changes in anesthetized dogs with bupivacaine-induced cardiovascular depression. Methods: Bupivacaine was infused to pentobarbital-anesthetized mongrel dogs (n = 8) at a rate of 0.5 mg/kg/min until the MBP decreased to 40 mmHg or less (end of bupivacaine infusion; BIE). We defined the early period as the interval from baseline till 30 minutes after the bupivacaine infusion and the late period as that after the 30 minutes till BIE. We monitored cSv with a fiberoptic pulmonary artery catheter. The MBP and CO were measured every ten minutes after the initiation of the bupivacaine infusion. Arterial blood gas analysis, mixed venous gas analysis, measurement of serum electrolyte concentrations and serum bupivacaine concentrations were performed simultaneously. The relationship between CO versus cSvO2 or versus MBP was compared retrospectively by regression analysis. Results: The Pearson's correlation coefficients between CO and cSvO2 were 0.782 ( = 0.6111, P 0.01) in the early period and 0.824 ( = 0.6790, P 0.01) in the late period. The correlation coefficients between CO and MBP were 0.019 (r2 = 0.0003, P 0.05) in the early period and 0.799 ( 0.01) = 0.6381, P 0.01) in the late period. Conclusions: cSvO2 is superior to MBP for the prediction of CO changes in bupivacaine-induced cardiac depression in dogs, especially in the early period. We might expect a profound reduction of CO when MBP begins to decrease in the late period.

Continuous cardiac output and mixed venous oxygen saturation monitoring

Continuous assessment of cardiac output and Svo 2 in the critically ill may be helpful in both the monitoring variations in the patient's cardiovascular state and in determining the efficacy of therapy. Commercially available continuous cardiac output (CCO) monitoring systems are based on the pulsed warm thermodilution technique. In vitro validation studies have demonstrated that this method provides higher accuracy and greater resistance to thermal noise than standard bolus thermodilution techniques. Numerous clinical studies comparing bolus with continuous thermodilution techniques have shown this technique similarly accurate to track each other and to have negligible bias between them. The comparison between continuous thermal and other cardiac output methods also demonstrates good precision of the continuous thermal technique. Accuracy of continuous oximetry monitoring using reflectance oximetry via fiberoptics has been assessed both in vitro and in vivo. Most of the studies testing agreement between continuous Svo 2 measurements and pulmonary arterial blood samples measured by standard oximetry have shown good correlation. Continuous Svo 2 monitoring is often used in the management of critically ill patients. The most recently designed pulmonary artery catheters are now able to simultaneously measure either Svo 2 and CCO or Svo 2 and right ventricular ejection fraction. This ability to view simultaneous trends of Svo 2 and right ventricular performance parameters will probably allow the clinician to graphically see the impact of volume loading or inotropic therapy over time, as well as the influence of multiple factors, including right ventricular dysfunction, on Svo 2. However, the cost-effectiveness of new pulmonary artery catheters application remains still questionable because no established utility or therapeutic guidelines are available.

Technology utilization in the cardiac surgical patient: SvO2 and capnography monitoring.

Technology utilization in the cardiac surgical patient has proliferated, despite a lack of evidence that the technology has a positive impact on patient outcomes. Hospitals are left to their own efforts in deciding how and what technology to use. The result is an inconsistent use of technology. The use of structured guidelines can help hospitals improve the use of technology. Two controversial technologies, capnography and mixed venous oxygen saturation monitoring, are analyzed using this approach. It is essential for hospitals to support clinicians as they use methods in the evaluation and implementation of technology. Technology alone will not improve patient outcome or control costs.

Evaluation of a continuous cardiac output and mixed venous oxygen saturation catheter in critically ill surgical patients

To evaluate the agreement of continuous cardiac output and mixed venous oxygen saturation measurements, obtained with a modified pulmonary artery catheter, with those values obtained by standard intermittent bolus thermodilution and cooximetry. Prospective, clinical investigation. A surgical intensive care unit in a tertiary referral center. Twenty-one adult critically ill surgical patients, requiring pulmonary artery catheter monitoring. None. A modified pulmonary artery catheter capable of continuous monitoring of cardiac output and mixed venous oxygen saturation was used with either an 8.5-Fr or a 9-Fr introducer. At random intervals, the continuous cardiac output measurement was compared with the cardiac output obtained using standard intermittent bolus thermodilution. The system was calibrated every 24 hrs for mixed venous oxygen saturation monitoring. Each saturation obtained by the laboratory cooximeter was compared with that value recorded using the catheter. Data points for 202 pairs of cardiac output (21 patients, 31 catheters) and 65 pairs of mixed venous oxygen saturation (20 patients, 28 catheters) were obtained. The bias and precision of the cardiac output data were 0.49 and 1.01 L/min, respectively. The agreement between the continuous and bolus values decreased as the cardiac output increased. Heart rate did not affect the agreement between the continuous and bolus techniques. The bias and precision of the mixed venous oxygen saturation data were -0.57% and 3.76%, respectively. The hematocrit did not affect the bias or precision of the venous saturation data over the hematocrit range observed (23.2% to 44.6%). Fewer catheter malfunctions were observed when the catheter was used with a 9-Fr introducer than with an 8.5-Fr introducer. The test catheter adequately measures continuous cardiac output and mixed venous oxygen saturation in the clinical setting. Because intermittent bolus thermodilution is not a true "gold standard" for cardiac output determination, new techniques compared with bolus thermodilution may fail to achieve accuracy expectations. A 9-Fr introducer is recommended, as fiberoptic damage may have occurred when the 8.5-Fr introducer was used.

Evaluating Cardiopulmonary Instability with Continuous Monitoring of Mixed Venous Oxygen Saturation

This article presents three cases that demonstrate the clinical application of mixed venous oxygen saturation monitoring. These case studies reflect how the critical care nurse integrates the physiology of oxygen delivery and consumption as well as critical thinking in making decisions regarding the care of patients with cardiopulmonary instability. This information gives the clinician immediate data from which therapeutic decisions are made to achieve positive patient outcomes.

Tissue oxygenation during liver transplantation.

a) To assess perioperative changes in tissue oxygenation parameters during liver transplantation; b) to evaluate the need for venovenous bypass as hemodynamic support; and c) to assess the efficacy of mixed venous oxygen saturation monitoring and the importance of lactate determinations in the management of patients following liver transplantation. Prospective case series. Liver transplant unit in a university hospital. A total of 68 consecutive patients undergoing liver transplantation. The entire population was analyzed before and after transplantation, dividing the patients into two groups, based on whether their initial cardiac index was higher (n = 37) or lower (n = 31) than 4.5 L/min/m2. Hemodynamic measurements and blood gas analyses were made before incision, before vascular clamping (including hepatic artery, portal vein and inferior vena cava), during the anhepatic phase, and at 5, 30, 60, and 120 mins following unclamping. Oxygen transport and oxygen consumption values were calculated. Serum lactate concentrations were measured by enzymatic technique. Mixed venous oxygen saturation was correlated with oxygen transport (Do2) in the whole population in which an abnormal oxygen consumption (Vo2)-Do2-dependent relationship occurred from the beginning of operation until 30 mins following unclamping. The comparison between hyperdynamic patients (initial cardiac index greater than 4.5 L/min/m2) with impaired tissue oxygenation and normodynamic patients showed that mixed venous oxygen saturation failed to correlate with Do2 when the cardiac index was greater than 4.5 L/min/m2 and that the Vo2-Do2 dependency was only noted in these patients. The serum lactate concentrations were similar in both groups. The Vo2-Do2-dependent relationship and mixed venous oxygen saturation-Do2 correlation noted in the 68 studied patients suggest the need for venovenous bypass and the reliability of mixed venous oxygen saturation monitoring in all patients scheduled for liver transplantation. However, a sharper comparison between hyperdynamic and normodynamic patients demonstrated the lack of efficacy of mixed venous oxygen saturation monitoring in predicting adequate tissue oxygenation in the first group and the mandatory need for venous shunting to limit tissue hypoxia which occurred despite its use only in these patients. Lactic acidosis appeared similarly in both groups and could not be linked to tissue hypoxia.

Oxygen consumption and mixed venous oxygen saturation monitoring during orthotopic liver transplantation.

Mixed venous oxygen saturation (SvO2) monitoring has been advocated for some critically ill patients. Patients with end-stage hepatic failure have oxygen consumption rates that are lower than normal. Using the Fick equation, oxygen consumption may be calculated if mixed venous and arterial oxygen tensions (and saturations), hemoglobin, and cardiac output are determined simultaneously. This report describes a unique pattern of changes in SvO2 and oxygen consumption in 7 patients undergoing liver transplantation. A previous study correlated plasma carbohydrate (glucose) levels with early hepatic graft survival. After induction, the 7 patients reported here had low oxygen consumption and high SvO2 values. The oxygen consumption rates decreased to the lowest point during the anhepatic phase and rose above baseline by the end of the case. The SvO2 and oxygen consumption data reported here follow the presence of presumed hepatic metabolic activity (increased CO2 and ionized calcium). Further research must be completed to determine whether these measurements indicate early hepatic nonfunction.

Relation between Mixed Venous Oxygen Saturation and Cardiac Index: Nonlinearity and Normalization for Oxygen Uptake and Hemoglobin

The ability of mixed venous oxygen saturation (SvO₂) monitoring to reflect changes in cardiac index (CI) with therapy in critically ill patients is unclear. To this end, SvO₂and CI were measured before and during an infusion of enoximone and/or dobutamine in 30 patients with advanced heart failure. A nonlinear relationship was observed between SvO₂ and CI with the nonlinear correlation coefficient being 0.52. On normalizing for individual differences in hemoglobin and oxygen consumption, this correlation coefficient became 0.90. Further analysis of individual data was performed using linear regression, and the slopes and correlation coefficients were found to span a wide range (slope: −10.0 to 30.9 min-mVL, r: −0.27 to 0.99). However, the mean slope and correlation coefficient for patients with baseline CI and SvO₂ <21/min/m* and <55 percent were 18.3 min-m²/L and 0.87, respectively, while those for the remainder of patients were only 3.1 min-m²/L and 0.42, respectively. Thus, the nonlinear correlation coefficient of the SvO₂-CI relationship in a group of patients is dependent on the homogeneity of their oxygen consumption and hemoglobin concentration. Furthermore, the ability of SvO₂to serve as a therapeutic indicator in any given patient is dependent on baseline SvO₂ and CI.