Effect of the Fraction of Inspired Oxygen on Intermittent Central Venous Oxygen Saturation Measurements (original) (raw)
Related papers
Central Venous and Mixed Venous Oxygen Saturation in Critically Ill Patients
Respiration, 2001
Although mixed venous O2 saturation (SvO2) accurately indicates the balance of O2 supply/demand and provides an index of tissue oxygenation, the use of a pulmonary artery (PA) catheter is associated with significant costs, risks and complications. Central venous O2 saturation (ScvO2), obtained in a less risky and costly manner, can be an attractive alternative to SvO2. To investigate whether the values of ScvO2 and SvO2 are well correlated and interchangeable in the evaluation of critically ill ICU patients and to create an equation that could estimate SvO2 from ScvO2. Sixty-one mechanically ventilated patients were catheterized upon admission and ScvO2 and SvO2 values were simultaneously measured in the lower part of the superior vena cava and PA respectively. SvO2 was 68.6 +/- 1.2% (mean +/- SEM) and ScvO2 was 69.4 +/- 1.1%. The difference is statistically significant (p < 0.03). The correlation coefficient r is 0.945 for the total population, 0.937 and 0.950 in surgical and medical patients, respectively. In 90.2% of patients the difference was <5%. When regression analysis was performed, among 11 models tested, power model [SvO2 = b0(ScvO2)b1] best described the relationship between the two parameters (R2 = 0.917). ScvO2 and SvO2 are closely related and are interchangeable for the initial evaluation of critically ill patients even if cardiac indices are different. SvO2 can be estimated with great accuracy by ScvO2 in 92% of the patients using a power model.
PLOS ONE
Background Central venous oxygen saturation (ScvO 2) is often used to help to guide resuscitation of critically ill patients. The standard gold technique for ScvO 2 measurement is the co-oximetry (Co-oximetry_ScvO 2), which is usually incorporated in most recent blood gas analyzers. However, in some hospitals, those machines are not available and only calculated ScvO 2 (Calc_ScvO 2) is provided. Therefore, we aimed to investigate the agreement between Co-oximetry_ScvO 2 and Calc_ScvO 2 in a general population of critically ill patients and septic shock patients. Methods A total of 100 patients with a central venous catheter were included in the study. One hundred central venous blood samples were collected and analyzed using the same point-ofcare blood gas analyzer, which provides both the calculated and measured ScvO 2 values. Bland and Altman plot, intra-class correlation coefficient (ICC), and Cohen's Kappa coefficient were used to assess the agreement between Co-oximetry_ScvO 2 and Calc_ScvO 2. Multiple linear regression analysis was performed to investigate the independent explanatory variables of the difference between Co-oximetry_ScvO 2 and Calc_ScvO 2. Results In all population, Bland and Altman's analysis showed poor agreement (+4.5 [-7.1, +16.1]%) between the two techniques. The ICC was 0.754 [(95% CI: 0.393-0.880), P< 0.001], and the Cohen's Kappa coefficient, after categorizing the two variables into two groups using a cutoff value of 70%, was 0.470 (P <0.001). In septic shock patients (49%), Bland and Altman's analysis also showed poor agreement (+5.6 [-6.7 to 17.8]%). The ICC was 0.720 [95% CI: 0.222-0.881], and the Cohen's Kappa coefficient was 0.501 (P <0.001). Four independent variables (PcvO 2 , Co-oximetry_ScvO 2 , venous pH, and Hb) were found to be associated with the difference between the measured and calculated ScvO 2 (adjusted R 2 = 0.8, P<0.001), with PcvO 2 being the main independent explanatory variable because of its
Journal of Cardiothoracic and Vascular Anesthesia, 2001
Objective: To examine the clinical applicability of substituting central venous oxygen saturation (ScvO 2) for mixed venous oxygen saturation (SmvO 2) in monitoring global tissue oxygenation. Design: Prospective clinical investigation. Setting: University hospital. Participants: Seventy-three adult patients. Interventions: Venous oxygen saturation was recorded, and oxygen saturation difference between SmvO 2 and ScvO 2 (⌬Smvcv) was calculated in 2 groups of patients (group I, sepsis patients [n ؍ 41], and group II, general anesthesia for cardiovascular surgery patients [n ؍ 32]) during initial placement of pulmonary artery catheters. Measurements and Main Results: Patients were classified as follows: class A, patients having a ⌬Smvcv >؊5%; class B, patients having a ⌬Smvcv between ؊5% and ؉5%; and class C, patients having a ⌬Smvcv >؉5 %. Statistically significant differences were observed in cardiac index, oxygen delivery index, and oxygen extraction ratio between class A and B in both groups. Class C of group II showed the worst correlation between SmvO 2 and ScvO 2 and had significantly lower arterial carbon dioxide tension values than class A and B. Conclusion: Pulmonary artery blood sampling should not be replaced with central venous blood. Hypocapnia and increased oxygen extraction ratio seem to be the major factors that worsen the relationship between ScvO 2 and SmvO 2 .
Clinical review: use of venous oxygen saturations as a goal - a yet unfinished puzzle
Critical Care, 2011
Shock is defi ned as global tissue hypoxia secondary to an imbalance between systemic oxygen delivery (DO 2 ) and systemic oxygen demand (VO 2 ). Unrecognised and untreated global tissue hypoxia increases morbidity and mortality. Accurate detection of global tissue hypoxia is therefore of vital importance. Physical fi ndings, vital signs, measuring central venous pressure and urinary output are important but insuffi cient for accurate detec tion of global tissue hypoxia . Measurement of mixed venous oxygen saturation (SvO 2 ) from the pulmo nary artery has been advocated as an indirect index of tissue oxygenation . As a result of an extensive debate in the literature , however, use of the pulmonary artery catheter has become somewhat unpopular. In contrast, insertion of a central venous catheter in the superior vena cava via the jugular of the subclavian vein is considered standard care in critically ill patients. Just like SvO 2 , the measurement of central venous oxygen saturation (ScvO 2 ) has been advocated in order to detect global tissue hypoxia.
CHEST Journal, 1989
Because central venous O saturation (superior vena cava, Scvo,) can be monitored with less patient risk than mixed venous O saturation (pulmonary artery, S O), we exammed the correlations between S O and ScvO2 over a broad range of cardiorespiratory conditions, including hypoxia, hemorrhage, and resuscitation in anesthetized dogs. The correlation coefficient (r) between Si O2 and ScvO, in 179 simultaneously drawn blood samples from 22 dogs was 0.97. !n another nine dogs, the two sites were continuously and simultaneously monitored with fiberoptic catheters; r was
Critical Care, 2009
Introduction Central venous oxygen saturation (ScvO2) has emerged as an important resuscitation goal for critically ill patients. Nevertheless, growing concerns about its limitations as a perfusion parameter have been expressed recently, including the uncommon finding of low ScvO2 values in patients in the intensive care unit (ICU). Emergency intubation may induce strong and eventually divergent effects on the physiologic determinants of oxygen transport (DO2) and oxygen consumption (VO2) and, thus, on ScvO2. Therefore, we conducted a study to determine the impact of emergency intubation on ScvO2. Methods In this prospective multicenter observational study, we included 103 septic and non-septic patients with a central venous catheter in place and in whom emergency intubation was required. A common intubation protocol was used and we evaluated several parameters including ScvO2 before and 15 minutes after emergency intubation. Statistical analysis included chi-square test and t test. Results ScvO2 increased from 61.8 ± 12.6% to 68.9 ± 12.2%, with no difference between septic and non-septic patients. ScvO2 increased in 84 patients (81.6%) without correlation to changes in arterial oxygen saturation (SaO2). Seventy eight (75.7%) patients were intubated with ScvO2 less than 70% and 21 (26.9%) normalized the parameter after the intervention. Only patients with pre-intubation ScvO2 more than 70% failed to increase the parameter after intubation. Conclusions ScvO2 increases significantly in response to emergency intubation in the majority of septic and non-septic patients. When interpreting ScvO2 during early resuscitation, it is crucial to consider whether the patient has been recently intubated or is spontaneously breathing.
Central venous oxygenation: when physiology explains apparent discrepancies
Critical care (London, England), 2014
Central venous oxygen saturation (ScvO2) >70% or mixed venous oxygen saturation (SvO2) >65% is recommended for both septic and non-septic patients. Although it is the task of experts to suggest clear and simple guidelines, there is a risk of reducing critical care to these simple recommendations. This article reviews the basic physiological and pathological features as well as the metrological issues that provide clear evidence that SvO2 and ScvO2 are adaptative variables with large inter-patient variability. This variability is exemplified in a modeled population of 1,000 standard ICU patients and in a real population of 100 patients including 15,860 measurements. In these populations, it can be seen how optimizing one to three of the four S(c)vO2 components homogenized the patients and yields a clear dependency with the fourth one. This explains the discordant results observed in large studies where cardiac output was increased up to predetermined S(c)vO2 thresholds followin...
Oxygenation equilibration time after alteration of inspired oxygen in critically ill patients
Heart & Lung: The Journal of Acute and Critical Care, 2010
To determine the time required for arterial oxygen partial pressure (PaO 2 ) equilibration after a change in fractional inspired oxygen (FIO 2 ) in intensive care unit (ICU) patients, a prospective study in a 7-bed university ICU was performed. Forty adult patients were examined using sequential arterial blood gas measurements after a .3 alteration in FIO 2 . The PaO 2 value measured at 30 minutes after a step change in FIO 2 in both periods was accepted as representative of the equilibrium value for PaO 2 . The mean equilibration time was 8.26 AE 5.6 minutes and 4.5 AE 2.65 minutes for increases and decreases in PaO 2 , respectively (P = .003). The constant k values were .44 AE .31 minutes and .72 AE .7 minutes for increases and decreases in PaO 2 , respectively. There was no significant difference between the increase and the decrease of 90% oxygenation times in the 2 groups (P = .150 and P = .446, respectively). The study confirms that a period of less than 10 minutes is adequate for 90% of the equilibration of PaO 2 to occur after an FIO 2 change in ICU patients. (Heart LungÒ 2010;39:147-152.)
Mixed venous oxygen saturation monitoring revisited: Thoughts for critical care nursing practice
Australian Critical Care, 2012
Background: Less invasive methods of determining cardiac output are now readily available. Using indicator dilution technique, for example has made it easier to continuously measure cardiac output because it uses the existing intra-arterial line. Therefore gone is the need for a pulmonary artery floatation catheter and with it the ability to measure left atrial and left ventricular work indices as well the ability to monitor and measure a mixed venous saturation (SvO 2). Purpose: The aim of this paper is to put forward the notion that SvO 2 provides valuable information about oxygen consumption and venous reserve; important measures in the critically ill to ensure oxygen supply meets cellular demand. In an attempt to portray this, a simplified example of the septic patient is offered to highlight the changing pathophysiological sequelae of the inflammatory process and its importance for monitoring SvO 2. Relevance to clinical practice: SvO 2 monitoring, it could be argued, provides the gold standard for assessing arterial and venous oxygen indices in the critically ill. For the bedside ICU nurse the plethora of information inherent in SvO 2 monitoring could provide them with important data that will assist in averting potential problems with oxygen delivery and consumption. However, it has been suggested that central venous saturation (ScvO 2) might be an attractive alternative to SvO 2 because of its less invasiveness and ease of obtaining a sample for analysis. There are problems with this approach and these are to do with where the catheter tip is sited and the nature of the venous admixture at this site. Studies have shown that ScvO 2 is less accurate than SvO 2 and should not be used as a sole guiding variable for decisionmaking. These studies have demonstrated that there is an unacceptably wide range in variance between ScvO 2 and SvO 2 and this is dependent on the presenting disease, in some cases SvO 2 will be significantly lower than ScvO 2 .
Paradigms of Oxygen Therapy in Critically Ill Patients
Journal of Intensive and Critical Care, 2017
Oxygen administration to patients has potential advantages and some evident drawbacks. Several clinical settings, mainly critical scenarios, demand high oxygen inspired fractions (FiO 2) in order to assure safe reserve margins for an eventual arterial desaturation (for example before tracheal intubation in operating room). On the other end some evidence shows that maintain high FiO 2 during surgical procedures and/or controlled ventilation in the intensive care units might be more harmful than beneficial. The aim of this revision was to show what type of decision clinicians may make, regarding the amount of oxygen that should be given to patients, with a special focus on the pros and cons of its liberal utilization.