Après circulation extra-corporelle, la mesure continue de la Svo2 et la co-oxymétrie du sang mêlé ne sont pas interchangeables

Accuracy, Precision, and Trending Ability of Perioperative Central Venous Oxygen Saturation Compared to Mixed Venous Oxygen Saturation in Unselected Cardiac Surgical Patients

OBJECTIVE

To determine whether central venous oxygen saturation (ScvO₂) measurements could be used interchangeably with mixed venous oxygen saturation (SvO₂) measurements in adult cardiac surgery patients.

DESIGN

A single-center prospective observational study.

SETTING

A university hospital.

PARTICIPANTS

Eighty-five adult patients undergoing cardiac surgery.

INTERVENTIONS

The study authors compared the oxygen saturations in 590 pairs of venous blood samples drawn from the pulmonary artery catheter (PAC) at three different time points during surgery and four different time points in the intensive care unit. They compared samples obtained from the distal pulmonary artery line (SvO₂) to those drawn from the proximal central venous line of the PAC (ScvO₂) with the Bland-Altman test and the four-quadrant method.

MEASUREMENTS AND MAIN RESULTS

The mean bias between SvO₂ and ScvO₂ was -1.9 (95% confidence interval [CI], -2.3 to -1.5) and the limits of agreement (LOA) were -11.5 to 7.6 (95% CI, -12.5 to -10.7 and 6.8-8.5, respectively). The percentage error (PE) was 13.2%. Based on the four-quadrant plot, only 50% of the measurement pairs were in agreement, indicating deficient trending ability.

CONCLUSION

ScvO₂ values showed acceptable accuracy as the mean bias was low. The precision was inadequate; although the PE was acceptable, the LOA were wide. Trending ability was inadequate. The authors cannot recommend the use of ScvO₂ values interchangeably with SvO₂ measurements in the management of adult cardiac surgery patients.

Comparison of mixed venous oxygen saturation after in vitro calibration of pulmonary artery catheter with that of pulmonary arterial blood in patients undergoing living donor liver transplantation

INTRODUCTION

Mixed venous saturation (SvO2) reflects the balance between oxygen delivery and consumption throughout the body. A multifunction pulmonary artery catheter (PAC) can monitor continuous SvO2 after in vitro calibration (CSvO2), obviating the need for in vivo calibration with pulmonary arterial blood. In critically ill patients CSvO2 has shown a good correlation with measured SvO2 of pulmonary arterial blood using co-oximetry (MSvO2). The aim of this study was to compare CSvO2 and MSvO2 in liver transplantation (OLT) recipients.

METHODS

We enrolled 44 OLT recipients for comparison with 24 coronary artery bypass graft (CABG) controls free of end-stage liver disease. After anesthetic induction, the PAC was inserted after in vitro calibration and CSvO2 and MSvO2 simultaneously measured. In OLT recipients, additional measurements of CSvO2 and MSvO2 were performed at anhepatic and postreperfusion phases. Pearson's correlation analysis was used to evaluate the correlation between the 2 measurements. A Bland-Altman analysis was used to determine precision of and bias between the 2 measurements. With ±3% regarded to be interchangeable.

RESULTS

Cardiac output and intrapulmonary shunt in CABG patients were lower than among OLT recipients. OLT recipients, showed a significant correlation between CSvO2 and MSvO2, but the coefficients were different during the three phases of OLT (r = 0.597, 0.753, and 0.756). In addition, bias values between the two measurements were 6.0%, 6.4%, and 2.9% for the preanhepatic, anhepatic, and postreperfusion phases, respectively, with 29.5%, 31.8%, and 50% of them being interchangeable. In contrast CABG patients showed bias in -0.17% with 75% of measurements interchangeable.

CONCLUSION

While in vitro calibration of the PAC can be used in CABG patients, MSvO2 is higher than CSvO2 in OLT recipients. Therefore, in vivo calibration with pulmonary arterial blood is necessary for accurate monitoring of SvO2 in OLT recipients.

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

BACKGROUND AND OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

The changing pattern of anesthesia, 1954-2004: a review based on the content of theCanadian Journal of Anesthesia in its first half-century

PURPOSE

In order to review changes and progress in anesthesiology in the second half of the 20th century, and to recognize the first half-century of the Journal's existence.

SOURCE

The content of the Journal from its inauguration in 1954 through 2004 was reviewed.

RESULTS

Although the data base is that of the Canadian Journal, many of the contributions were from other countries, and for this reason the findings will have relevance both in Canada and elsewhere. The review suggests that anesthesiology evolved in two phases in this period: from 1954 to 1978 and from 1979 to 2004. The first was characterized by the introduction of new drugs and adaptation to new surgical techniques; the second, by a greater emphasis on clinical excellence, outcome, quality patient care both in the operating room and elsewhere in the hospital, and research.

CONCLUSIONS

Although profound advances in knowledge, techniques, and relationships, have shaped the pattern and practice of anesthesiology in this half-century, the basic concerns of anesthesiologists relating to the practice of anesthesia and to their patients remained unchanged. At the same time, the many advances that have shaped anesthesiology in this half-century have extended the understanding of the phenomenon of anesthesia and enhanced the quality of patient care, which gives rise to the hope that anesthesiologists will continue to fully achieve these twin goals in the next half-century.

Diagnostic measures to evaluate oxygenation in critically ill adults: implications and limitations

Accurate assessment and treatment of disturbances in oxygenation are crucial to optimal outcomes in critically ill patients. Oxygenation is dependent upon adequate pulmonary gas exchange, oxygen delivery, and oxygen consumption. Each of these physiologic processes may vary independently in response to pathophysiologic conditions and therapeutic interventions. The author reviews diagnostic measures available to evaluate pulmonary gas exchange, oxygen delivery, and oxygen consumption in critically ill patients. Currently available tools and their potential value as well as key methodological limitations are addressed. Failure on behalf of clinicians to fully appreciate these limitations can lead to misdiagnoses and inappropriate treatment. The aim of this article is to help advanced practice nurses more fully understand the implications and limitations of these diagnostic measures to ensure accurate assessment and treatment of disturbances in oxygenation.