Measurement Of Mixed Venous Oxygen Saturation Research Articles

Abstract 10557: A Case of Cardiogenic Shock in a Woman With a Mitochondrial Cardiomyopathy

Case Presentation: A 35-year-old woman with nonischemic cardiomyopathy, with a left ventricular ejection fraction <20% on home dobutamine, and chronic weakness was referred to our institution for heart transplantation evaluation. She was directly admitted to the hospital for suspected cardiogenic shock after her labs revealed a lactate level of 5.4 mmol/L. Her hospital course was complicated by persistently undulating lactate levels (0.2 - 8.6 mmol/L) that increased with exertion, despite normal mixed venous oxygen saturation measurements obtained from a pulmonary artery catheter. Serologic genetic testing was negative, and electromyography revealed the presence of a proximal and axial myopathy. A deltoid muscle biopsy was obtained, and genetic testing of the specimen revealed two mitochondrial deoxyribonucleic acid deletions, and electron microscopy revealed mitochondrial paracrystalline inclusions. She subsequently underwent left ventricular assist device placement and was started on carnitine, arginine, creatine, thiamine, and coenzyme Q10 supplementation. Despite left ventricular assist device placement, the patient has continued to decline due to progressive right heart failure and is currently being considered for cardiac transplantation. Discussion: Mitochondrial cardiomyopathy (MCM) is an alteration in cardiac structure and function caused by genetic defects of the mitochondrial respiratory chain, in the absence of other causes of heart failure. The true prevalence of MCM is unknown. Clinical manifestations in those with MCM present on a spectrum, ranging from asymptomatic cases to those with signs and symptoms typical of heart failure. Extra-cardiac features commonly include chronic weakness and fatigue. Diagnosis is made with prompt genetic testing and microscopic evaluation of a skeletal muscle biopsy specimen. Outcomes in patients who receive a left ventricular assist device are unknown and warrant further investigation.

Use of Central Venous Oxygen Saturation to Guide Therapy

The use of pulmonary artery catheters has diminished, so that other technologies are emerging. Central venous oxygen saturation measurement (ScvO₂) as a surrogate for mixed venous oxygen saturation measurement (SvO₂) is simple and clinically accessible. To maximize the clinical utility of ScvO₂ (or SvO₂) measurement, it is useful to review what the measurement means in a physiologic context,how the measurement is made, important limitations, and how this measurement may be helpful in common clinical scenarios. Compared with cardiac output measurement, SvO₂ is more directly related to tissue oxygenation. Furthermore,when tissue oxygenation is a clinical concern, SvO₂ is less prone to error compared with cardiac output, where small measurement errors may lead to larger errors in interpreting adequacy of oxygen delivery. ScvO₂ should be measured from the tip of a central venous catheter placed close to, or within, the right atrium to reduce measurement error. Correct clinical interpretation of SvO₂, or its properly measured ScvO₂ surrogate, can be used to (1) estimate cardiac output using the Fick equation, (2) better understand whether a patient's oxygen delivery is adequate to meet their oxygen demands, (3) help guide clinical practice, particularly when resuscitating patients using validated early goal directed therapy treatment protocols, (4) understand and treat arterial hypoxemia, and (5) rapidly estimate shunt fraction (venous admixture).

Role of Central and Mixed Venous Oxygen Saturation Measurement in Perioperative Care

Role of Central and Mixed Venous Oxygen Saturation Measurement in Perioperative Care

Role of Central and Mixed Venous Oxygen Saturation Measurement in Perioperative Care

Complications after major surgery are a leading cause of morbidity and mortality. The etiology of postoperative complications is complex, but poor cardiorespiratory reserve appears to be a key factor. There is increasing interest in the use of central and mixed venous oxygen saturation to guide therapeutic interventions during the perioperative period. However, a detailed understanding of the physiologic principles of venous oximetry is essential for safe and effective use in clinical practice. Venous oxygen saturation reflects the balance between global oxygen delivery and oxygen consumption, which may be affected by a wide range of factors during the perioperative period. The purpose of this article is to describe the physiology and measurement of mixed and central venous oxygen saturation and to explore the findings of clinical investigations of their use in perioperative care.

A Comparison of Central and Mixed Venous Oxygen Saturation in Circulatory Failure

The purpose of this study was to evaluate whether central venous oxygen saturation can be used as an alternative to mixed venous oxygen saturation in patients with cardiogenic and septic shock. Prospective clinical study. A tertiary intensive care unit in a university hospital. Twenty patients with cardiogenic or septic shock requiring a pulmonary artery catheter and inotropic support. None. The central venous oxygen saturation overestimated the mixed venous oxygen saturation by a mean bias (or an absolute difference) of 6.9%, and the 95% limits of agreement were large (-5.0% to 18.8%). The difference between central and mixed venous oxygen saturation appeared to be more significant when mixed venous oxygen saturation was <70%. The changes in central and mixed venous oxygen saturation did not follow the line of perfect agreement closely in different clinical conditions. The central or mixed venous oxygen saturation had a significant ability to predict the status of cardiac output state, but this ability was reduced when the effect of hyperoxia was not considered. Central and mixed venous oxygen saturation measurements are not interchangeable numerically.

Validity of Arterial and Mixed Venous Oxygen Saturation Measurements in a Canine Hemorrhage Model After Resuscitation with Varying Concentrations of Hemoglobin-Based Oxygen Carrier

Validity of Arterial and Mixed Venous Oxygen Saturation Measurements in a Canine Hemorrhage Model After Resuscitation with Varying Concentrations of Hemoglobin-Based Oxygen Carrier

Validity of arterial and mixed venous oxygen saturation measurements in a canine hemorrhage model after resuscitation with varying concentrations of hemoglobin-based oxygen carrier.

In this study, we evaluated the validity of saturation measurements in mixed venous and arterial blood during posthemorrhagic anemia and resuscitation with varying levels of hemoglobin-based oxygen carrier (Hemoglobin glutamer-200 [bovine]; Oxyglobin [Hb-200]). Nineteen anesthetized, splenectomized, mixed-breed dogs were anesthetized (two were excluded from the data because they did not survive the exsanguination, supporting the validity of the model). Their pulmonary arteries were cannulated with the Abbott QVUE Oximetrix 3 catheter. An 18-gauge catheter was placed in the femoral artery, and a reusable Nellcor probe was applied to the tongue. Mixed venous and arterial samples were drawn at baseline, after 40% hemorrhage (to keep arterial pressure at 50 mm Hg), and postresuscitation with 30 mL/kg of 6% hetastarch in lactated Ringer's solution (n = 4), 10 mL/kg of Hb-200, 20 mL/kg of hetastarch (n = 6), 20 mL/kg of Hb-200, and 10 mL/kg of hetastarch (n = 7). Samples were compared with oxygen content from the LEXO2CON-K oxygen analyzer, and oxygen content was calculated for all values from the monitors. Results were compared by using analysis of variance. There was good correlation (0.97 > or = r > or = 0.92) for the measured versus calculated hemoglobin oxygen saturation values at baseline. After resuscitation, the correlation between calculated and measured values of oxygen content was significantly smaller for all tested instruments. The values of oxygen content calculated from the oxygen saturation monitor and from the oximetric pulmonary artery can deviate by as much as 20% from directly measured values. We conclude that the administration of this oxygen therapeutic may interfere with the values of some monitors. This study evaluated oxygen saturation monitors in a canine model of acute blood loss and resuscitation with a blood substitute and found that these may interfere with the monitors' results in a dose-dependent way.

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.

Partial liquid ventilation combined with inhaled nitric oxide in acute respiratory failure with pulmonary hypertension in piglets.

This study was a prospective, randomized, controlled design to evaluate gas exchange, lung mechanics, and pulmonary hemodynamics during partial liquid ventilation (PLV) combined with inhaled nitric oxide (NO) in acute respiratory failure (ARF) with pulmonary hypertension (PH). ARF with PH was induced in 12 piglets weighing 9.7-13.7 kg by repeated lung lavages and the continuous infusion of the stable endoperoxane analog of thromboxane. Thereafter the animals were randomly assigned either for PLV or conventional mechanical ventilation (CMV) at a fractional concentration of inspired O2 (Fio2) of 1.0. Perfluorocarbon (PFC) liquid (30 mL kg-1) was instilled into the endotracheal tube over 5 min followed by 5 mL kg-1h-1. All animals were treated with different concentrations of NO (1-10-20 ppm) inhaled in random order. Continuous monitoring included ECG, right atrial (Pra), mean pulmonary artery (Ppa), pulmonary capillary (Ppc'), and mean arterial (Pa) pressures, arteria oxygen saturation, and mixed venous oxygen saturation measurements. During PLV Pao2/Fio2 increased significantly from 8.2 +/- 0.4 kPa to 34.8 +/- 5.1 kPa (p < 0.01), whereas Pao2/FiO2 remained constant at 9.5 +/- 0.4 kPa during CMV. The infusion of the endoperoxane analog resulted in a sudden decrease of Pao2/Fio2 from 34.8 +/- 5.1 kPa to 14.1 +/- 0.4 kPa (p < 0.01) in the PLV group and from 9.5 +/- 0.4 kPa to 6.9 +/- 0.2 kPa (p < 0.05) in the control group. Inhaled NO significantly improved oxygenation in both groups (Pao2/Fio2: 45.7 +/- 5.3 kPa during PLV and 25.9 +/- 4.7 kPa during CMV). During inhalation of NO mean Ppa decreased significantly from 7.8 +/- 0.26 kPa to 4.2 +/- 0.26 kPa (p < 0.01) in the PLV group and from 7.4 +/- 0.26 kPa to 5.1 +/- 0.13 kPa (p < 0.01) in the control group. As documented in the literature PLV significantly improves oxygenation and lung mechanics in severe ARF. In addition, when ARF is associated with severe PH, the combined treatment of PLV and inhaled NO improves pulmonary hemodynamics resulting in better oxygenation.

Hemodynamic effects of different modes of mechanical ventilation in acute cardiac and pulmonary failure: An experimental study

Objective: To determine the hemodynamic effects of four different modes of mechanical ventilation in an animal model of acute cardiac and pulmonary failure. Design: Prospective, randomized, crossover design. Setting: University research laboratory. Subjects: Twelve piglets weighing 10 to 16 kg. Interventions: The experimental protocol consisted of three stable 30-min periods: when ventricular and pulmonary functions were normal (control), after the induction of acute cardiac failure by the administration of a β-adrenergic receptor blocker, and after pulmonary failure induced by repeated lung lavage. Modes of mechanical ventilation included controlled mechanical ventilation, high-frequency oscillation, synchronized high-frequency jet ventilation, and external negative pressure oscillation combined with pressure support ventilation. Each mode of respiratory support was randomly and sequentially applied to each animal with the assessment of cardiopulmonary function at the end of each period. Measurements and Main Results: Continuous monitoring included electrocardiogram, right atrial, left ventricular end-diastolic, pulmonary arterial, intrathoracic aortic, arterial, esophageal, and transpulmonary pressures and arterial and mixed venous oxygen saturation measurements. In addition, cardiac output using the thermodilution technique was measured intermittently. Whereas in the control period cardiac index was significantly (p< .05) higher during synchronized high-frequency jet ventilation (193 ± 19.3 mL/kg/min) than during controlled mechanical ventilation (151 ± 12.1 mL/kg/min) and high-frequency oscillation (151 ± 18.1 mL/kg/min), there was no significant hemodynamic difference between the four modes of mechanical ventilation in the cardiac and pulmonary failure periods. In the pulmonary failure period, transpulmonary pressure was significantly higher during high-frequency oscillation (7.1 ± 1.6 mm Hg) than during controlled mechanical ventilation (5.6 ± 0.6 mm Hg), high-frequency ventilation (4.1 ± 0.4 mm Hg), and external negative pressure oscillation combined with pressure support ventilation (5.3 ± 0.5 mm Hg). Conclusions: Synchronized high-frequency ventilation improves cardiac performance in control conditions. No hemodynamic difference is present between the four modes of mechanical ventilation in the cardiac and pulmonary failure periods. External negative pressure oscillation combined with pressure support ventilation has moderate hemodynamic advantages over controlled mechanical ventilation and high-frequency oscillation in different clinical settings, but it also results in a deterioration of pulmonary gas exchange during the pulmonary failure period. (Crit Care Med 1994; 22:1624–1630)

Hemodynamic effects of different modes of mechanical ventilation in acute cardiac and pulmonary failure: An experimental study

To determine the hemodynamic effects of four different modes of mechanical ventilation in an animal model of acute cardiac and pulmonary failure. Prospective, randomized, crossover design. University research laboratory. Twelve piglets weighing 10 to 16 kg. The experimental protocol consisted of three stable 30-min periods: when ventricular and pulmonary functions were normal (control), after the induction of acute cardiac failure by the administration of a beta-adrenergic receptor blocker, and after pulmonary failure induced by repeated lung lavage. Modes of mechanical ventilation included controlled mechanical ventilation, high-frequency oscillation, synchronized high-frequency jet ventilation, and external negative pressure oscillation combined with pressure support ventilation. Each mode of respiratory support was randomly and sequentially applied to each animal with the assessment of cardiopulmonary function at the end of each period. Continuous monitoring included electrocardiogram, right atrial, left ventricular end-diastolic, pulmonary arterial, intrathoracic aortic, arterial, esophageal, and transpulmonary pressures and arterial and mixed venous oxygen saturation measurements. In addition, cardiac output using the thermodilution technique was measured intermittently. Whereas in the control period cardiac index was significantly (p < .05) higher during synchronized high-frequency jet ventilation (193 +/- 19.3 mL/kg/min) than during controlled mechanical ventilation (151 +/- 12.1 mL/kg/min) and high-frequency oscillation (151 +/- 18.1 mL/kg/min), there was no significant hemodynamic difference between the four modes of mechanical ventilation in the cardiac and pulmonary failure periods. In the pulmonary failure period, transpulmonary pressure was significantly higher during high-frequency oscillation (7.1 +/- 1.6 mm Hg) than during controlled mechanical ventilation (5.6 +/- 0.6 mm Hg), high-frequency ventilation (4.1 +/- 0.4 mm Hg), and external negative pressure oscillation combined with pressure support ventilation (5.3 +/- 0.5 mm Hg). Synchronized high-frequency ventilation improves cardiac performance in control conditions. No hemodynamic difference is present between the four modes of mechanical ventilation in the cardiac and pulmonary failure periods. External negative pressure oscillation combined with pressure support ventilation has moderate hemodynamic advantages over controlled mechanical ventilation and high-frequency oscillation in different clinical settings, but it also results in a deterioration of pulmonary gas exchange during the pulmonary failure period.

Critical care and emergency nursing 2nd editionCritical care and emergency nursing 2nd edition S Smith Huddleston S Ferguson Springhouse Corporation 262pp £11.50 0-87434-617-7

Critical Care and Emergency Nursing is a second edition of one of the books in the Springhouse Notes Series. It is a welcome addition to any nurse working in the areas of critical or intensive care. As with most critical care texts, it is arranged by body systems, but includes clear and well- explained sections on nursing skills and procedures that are common in these areas, that is, mechanical ventilation, arterial pressure monitoring and mixed venous oxygen saturation measurement.

Critical Care and Emergency Nursing, 2nd edition S Smith Huddleston and SFerguson Critical Care and Emergency Nursing, 2nd editionSpringhouse Corporation262pp£11.500-87434-617-7

Critical Care and Emergency Nursing is a second edition of one of the books in the Springhouse Notes Series. It is a welcome addition to any nurse working in the areas of intensive or critical care. As with most critical care texts, it is arranged by body systems, but includes clear and well-explained sections on nursing skills and procedures that are common in these clinical areas, that is, mechanical ventilation, arterial pressure monitoring, pulmonary artery pressure monitoring, cardiac output determination, mixed venous oxygen saturation measurements and intracranial pressure monitoring.

Continuous mixed venous oxygen saturation measurement: a significant advance in hemodynamic monitoring?

Development of the flow-directed pulmonary artery catheter in combination with reflective fiberoptic oximetry techniques allows the clinician to continuously measure mixed venous oxygen saturation (SvO2). A brief review of the determinants of oxygen balance, the Fick principle, and the technology of continuous SvO2 monitoring is preliminary to a debate between two clinicians on the usefulness of SvO2 monitoring. One clinician highly recommends use of the flow-directed pulmonary artery catheter in patients who require pulmonary artery catheterization. Monitoring of SvO2 is described as a safe, convenient, and reliable option that is cost-effective. Continuous availability of this dynamic physiologic monitor is of great value in improving understanding of serious disturbances in oxygen balance, providing information for rapid diagnosis, and guiding therapeutic interventions. Another clinician suggests a less enthusiastic approach to SvO2 monitoring and argues that SvO2 is a nonspecific index of the matching of oxygen delivery with supply. Although it is a useful adjunct in specific clinical situations, it provides uncertain information in the presence of a number of diseases. Major mistakes in patient management could follow from overreliance upon either absolute SvO2 measurements or analysis of trends over time. Use of the SvO2 monitor has not been proven cost-effective and may actually increase monitoring costs. Both clinicians agree that continuous SvO2 monitoring is valuable in many clinical circumstances, provided the limitations of the measurement are understood.

Continuous S-vO2 measurement and oxygen transport patterns in cardiac surgery patients.

Twenty adult cardiac surgery patients with impaired ventricular function by contrast ventriculography at cardiac catheterization were monitored from before anesthesia until the time of extubation up to 12 h postoperatively. A thermodilution pulmonary artery catheter with fiberoptic channels for continuous measurement of mixed-venous oxygen saturation (S-vO2) by reflection oximetry was substituted for the usual catheter. The S-vO2 was recorded continuously along with blood pressure, cardiac filling pressures, and heart rate. Thermodilution cardiac output determinations were used to derive hemodynamic and oxygen transport indices. There was a consistently high and significant negative correlation (r = -.84) between S-vO2 and the percentage of oxygen extracted from blood. Thus, S-vO2 reflects oxygen extraction and continuous S-vO2 provides continuous quantification of global oxygen extraction. None of the other oxygen transport variables including cardiac index showed significant correlation with S-vO2. The oximetry system provides a continuous and reliable indication of mixed-venous blood oxygenation which is a continuous reflection of oxygen extraction.

Effect of temperature on solubility of O2 in human plasma.

(See PDF) Page 58: in table 2, agr Blood values ascribed to Handbook of Raspiration should read 28 C 0.0285; 18 C No value.