Oximetry Catheter Research Articles

Association between regional oxygen saturation and central venous saturation in pediatric patients undergoing cardiac surgery: A prospective observational study.

We evaluated the correlation between regional oxygen saturation (rSO2 ) in the frontal and right renal dorsum (cerebral rSO2 and somatic rSO2 ) measured by near-infrared spectroscopy (INVOS™ 5100C, Medtronic) and central venous oxygen saturation (ScvO2 ) measured with a fiber-optic oximetry catheter (PediaSat™, Edwards Lifesciences) during surgery in order to determine whether noninvasive rSO2 could be used as an alternative to ScvO2 in pediatric cardiac surgery patients. We evaluated the correlation between regional tissue oxygen saturation (cerebral rSO2 and somatic rSO2 ) measured by near-infrared spectroscopy and other patient measures with central venous oxygen saturation (ScvO2 ) measured with a fiber-optic oximetry catheter to track global oxygen supply demand as a potential alternative or supplement to ScvO2 . This single-center prospective observational study enrolled 33 children (weight < 10 kg) who underwent cardiac surgery for congenital heart disease between February 2018 and November 2021. ScvO2 , cerebral rSO2 , and somatic rSO2 were recorded simultaneously after anesthesia induction and central venous catheter placement. Pearson's correlation coefficient and Bland-Altman analysis were used to determine the relationship between ScvO2 and rSO2 . We conducted correlation, Bland Altman, and multiple regression analyses to identify associations between rSO2 , patient measures, and ScvO2 values. The patients' median age was 11.0 (quartile 2.0-16.0) months. Their weight was 7.2 (quartile 4.5-9.2) kg. Cerebral rSO2 was significantly positively correlated with ScvO2 (r2 = 0.29, p = .002 in all patients; r2 = 0.61, p = .013 in the patients without mixing at the atrial level), whereas somatic rSO2 was not. The Bland-Altman analysis demonstrated biases [95% confidence interval; 95% CI] (lower and upper limits of agreement [95% CI]) of 0.27% [-4.26 to 4.80] (-24.79 [-32.61 to -16.96] to 25.33 [17.50 to 33.16]) between cerebral rSO2 and ScvO2 and 0.91% [-5.48 to 7.30] (-34.43 [-45.47 to -23.39] to 36.25 [25.21 to 47.29]) between somatic rSO2 and ScvO2 . Preoperative brain natriuretic peptide (BNP) and SpO2 were independent variables associated with ScvO2 and cerebral and somatic rSO2 . Cerebral rSO2 , SpO2 , and BNP were significantly correlated with ScvO2 , although the cerebral rSO2 correlation was greater for lesions without atrial mixing. rSO2 , BNP, and SpO2 might be used to track changes in ScvO2 but cerebral rSO2 is not sufficiently precise to replace it.

Abstract O-12: INTERMITTENT VERSUS CONTINUOUS SCVO2 MONITORING DURING EARLY GOAL DIRECTED THERAPY IN SEPTIC SHOCK: A RANDOMIZED TRIAL

Aims & Objectives: To compare the effect of ‘intermittent’ central venous oxygen saturation (ScvO2) monitoring with ‘continuous’ ScvO2 monitoring on shock resolution and mortality in children with septic shock. Methods We randomly assigned children <17 years’ age with septic shock to ‘intermittent ScvO2’ or ‘continuous ScvO2’ groups. All children were subjected to subclavian/internal jugular line insertion and managed as per the Surviving Sepsis Campaign Guidelines. ScvO2 – estimated at 1, 3, 6, 12, 24, 48 and 72 hours in the ‘intermittent’ group and continuously using the central venous oximetry catheter in the ‘continuous’ group – was used to guide resuscitation; other clinical and laboratory parameters were monitored similarly in the two groups. Major outcomes were achievement of therapeutic goals within first 6 hours and in-hospital mortality. Data were analysed using STATA 13. Results We enrolled 101 [62 boys; median (IQR) age: 6 (1.5 to 10) years] children: 50 and 51 in ‘intermittent’ and ‘continuous’ groups, respectively. Baseline characteristics including organ dysfunction and mortality risk scores were comparable between the groups. When compared to ‘intermittent’ group, more children in the ‘continuous’ group achieved therapeutic end points within first 6 hours (33% vs. 16%; RR 2.08, 95% CI 0.98 to 4.38) but there was no difference in mortality (43% vs. 46%; RR 1.06, 0.69 to1.64) between the groups. Conclusions Continuous ScvO2 monitoring resulted in higher proportion of children attaining therapeutic end points in the first 6 hours. However, this did not seem to affect the mortality. Larger studies are required to compare the effect on mortality.

Decreases in Mixed Venous Blood O2 Saturation in Cardiac Surgery Patients Following Extubation.

Decreases in mixed venous O2 saturation (SvO2) have been reported to occur in postcardiac surgery patients during weaning from mechanical ventilation. Our aim was to establish whether the physiological mechanism responsible for this phenomenon was a decrease in systemic O2 delivery (DO2) or an increase in global O2 consumption ( O 2). We studied 21 mechanically ventilated, postoperative cardiac patients for 30 minutes before and 60 minutes after extubation. We monitored continuously arterial O2 saturation by pulse oximetry (SaO2) and central venous O2 saturation (ScvO2) with an oximetry catheter. Mixed venous O2 saturation (SvO2) and cardiac output were also measured continuously with an oximetry pulmonary artery catheter. Systemic O2 delivery and O 2 were calculated according to accepted formulae. Immediately following extubation, ScvO2 and SvO2 decreased rapidly (P < .01). Systemic O2 consumption increased from 65 (57) mL·min-1 to 194 (66) mL·min-1 (P < .05) with no changes in DO2. Consequently, systemic O2 extraction rose from 38% (8%) to 45% (9%; P < .01). Preoperative left ventricular ejection fraction correlated with the decline in SvO2 postextubation. All patients weaned successfully. Decreases in SvO2 after discontinuation of ventilatory support in postcardiac surgery patients occur as O 2 increases in response to greater energy requirements by muscles of ventilation that are not initially matched by increases in DO2.

Head-up tilt rapidly compromises hemodynamics in healthy anesthetized swine.

The aims were to explore the effect of head-up tilt (HUT) to 30 and 60 degrees on hemodynamics and tissue oxygenation in anesthetized healthy swine. The data serve as a reference for a study of resuscitation efficacy at HUT such as during transport. Nine healthy swine (49+/-4 kg) were anesthetized and multiple sensors including myocardial pressure-volume loops catheter, carotid flow probe, blood pressure catheters, near infrared spectroscopy (NIRS) tissue oximetry and mixed venous oximetry (SVO2) catheter were introduced and parameters continuously recorded. Experimental protocol consisted of baseline in supine position (15 min), 30 degrees HUT (15 min), recovery at supine position (15 min) and 60 degrees HUT (5 min). Vacuum mattress was used for body fixation during tilts. We found that 30 and 60 degrees inclination led to significant immediate reduction in hemodynamic and oximetry parameters. Mean arterial pressure (mm Hg) decreased from 98 at baseline to 53 and 39, respectively. Carotid blood flow dropped to 47 % and 22 % of baseline values, end diastolic volume to 49 % and 53 % and stroke volume to 47 % and 45 % of baseline. SVO2 and tissue oximetry decreased by 17 and 21 percentage points. The values are means. In conclusions, within minutes, both 30 and 60 degrees head-up tilting is poorly tolerated in anesthetized swine. Significant differences among individual animals exist.

Wireless monitoring of liver hemodynamics in vivo.

Liver transplants have their highest technical failure rate in the first two weeks following surgery. Currently, there are limited devices for continuous, real-time monitoring of the graft. In this work, a three wavelengths system is presented that combines near-infrared spectroscopy and photoplethysmography with a processing method that can uniquely measure and separate the venous and arterial oxygen contributions. This strategy allows for the quantification of tissue oxygen consumption used to study hepatic metabolic activity and to relate it to tissue stress. The sensor is battery operated and communicates wirelessly with a data acquisition computer which provides the possibility of implantation provided sufficient miniaturization. In two in vivo porcine studies, the sensor tracked perfusion changes in hepatic tissue during vascular occlusions with a root mean square error (RMSE) of 0.135 mL/min/g of tissue. We show the possibility of using the pulsatile wave to measure the arterial oxygen saturation similar to pulse oximetry. The signal is also used to extract the venous oxygen saturation from the direct current (DC) levels. Arterial and venous oxygen saturation changes were measured with an RMSE of 2.19% and 1.39% respectively when no vascular occlusions were induced. This error increased to 2.82% and 3.83% when vascular occlusions were induced during hypoxia. These errors are similar to the resolution of a commercial oximetry catheter used as a reference. This work is the first realization of a wireless optical sensor for continuous monitoring of hepatic hemodynamics.

Fiberoptic monitoring of central venous oxygen saturation (PediaSat) in small children undergoing cardiac surgery: continuous is not continuous.

Monitoring of superior vena cava saturation (ScvO 2) has become routine in the management of pediatric patients undergoing cardiac surgery. The objective of our study was to evaluate the correlation between continuous ScvO 2by the application of a fiber-optic oximetry catheter (PediaSat) and intermittent ScvO 2by using standard blood gas measurements. These results were compared to those obtained by cerebral near infrared spectroscopy (cNIRS). Tertiary pediatric cardiac intensive care unit (PCICU). A retrospective study was conducted in consecutive patients who were monitored with a 4.5 or 5.5 F PediaSat catheter into the right internal jugular vein. An in vivocalibration was performed once the patient was transferred to the PCICU and re-calibration took place every 24 hours thereafter. Each patient had a NIRS placed on the forehead. Saturations were collected every 4 hours until extubation. Ten patients with a median age of 2.2 (0.13-8.5) years and a weight of 12.4 (3.9-24) kg were enrolled. Median sampling time was 32 (19-44) hours: 64 pairs of PediaSat and ScVO2 saturations showed a poor correlation (r=0.62, 95% CI 44-75; p<0.0001) and Bland Altman analysis for repeated measures showed an average difference of 0.34 with a standard deviation of 7,9 and 95% limits of agreement from -15 to 16. Thirty-six pairs of cNIRS and ScVO2 saturations showed a fair correlation (r=0.79, 95% CI 0.60-0.89; p<0.0001) an average difference of -1.4 with a standard deviation of 6 and 95% limits of agreement from -13 to 10. Analysis of median percentage differences between PediaSat and ScvO2 saturation over time revealed that, although not statistically significant, the change in percentage saturation differences was clinically relevant after the 8th hour from calibration (from -100 to +100%). PediaSat catheters showed unreliable performance in our cohort. It should be further investigated whether repeating calibrations every 8 hours may improve the accuracy of this system. CNIRS may provide similar results with a lower invasiveness.

Fiberoptic monitoring of central venous oxygen saturation (PediaSat) in small children undergoing cardiac surgery: continuous is not continuous

Background: &nbsp;Monitoring of superior vena cava saturation (ScvO 2 ) has become routine in the management of pediatric patients undergoing cardiac surgery. The objective of our study was to evaluate the correlation between continuous ScvO 2 &nbsp;by the application of a fiber-optic oximetry catheter (PediaSat) and intermittent ScvO 2 &nbsp;by using standard blood gas measurements. These results were compared to those obtained by cerebral near infrared spectroscopy (cNIRS). Setting: &nbsp;Tertiary pediatric cardiac intensive care unit (PCICU). Methods and main results: &nbsp;A retrospective study was conducted in consecutive patients who were monitored with a 4.5 or 5.5 F PediaSat catheter into the right internal jugular vein. An&nbsp; in vivo &nbsp;calibration was performed once the patient was transferred to the PCICU and re-calibration took place every 24 hours thereafter. Each patient had a NIRS placed on the forehead. Saturations were collected every 4 hours until extubation. Ten patients with a median age of 2.2 (0.13-8.5) years and a weight of 12.4 (3.9-24) kg were enrolled. Median sampling time was 32 (19-44) hours: 64 pairs of PediaSat and ScVO2 saturations showed a poor correlation (r=0.62, 95% CI 44-75; p&lt;0.0001) and Bland Altman analysis for repeated measures showed an average difference of 0.34 with a standard deviation of 7,9 and 95% limits of agreement from -15 to 16. Thirty-six pairs of cNIRS and ScVO2 saturations showed a fair correlation (r=0.79, 95% CI 0.60-0.89; p&lt;0.0001) an average difference of -1.4 with a standard deviation of 6 and 95% limits of agreement from -13 to 10. Analysis of median percentage differences between PediaSat and ScvO2 saturation over time revealed that, although not statistically significant, the change in percentage saturation differences was clinically relevant after the 8th hour from calibration (from -100 to +100%). Conclusion: &nbsp;PediaSat catheters showed unreliable performance in our cohort. It should be further investigated whether repeating calibrations every 8 hours may improve the accuracy of this system. CNIRS may provide similar results with a lower invasiveness.

Fiberoptic monitoring of central venous oxygen saturation (PediaSat) in small children undergoing cardiac surgery: continuous is not continuous

Background: Monitoring of superior vena cava saturation (ScvO 2) has become routine in the management of pediatric patients undergoing cardiac surgery. The objective of our study was to evaluate the correlation between continuous ScvO 2 by the application of a fiber-optic oximetry catheter (PediaSat) and intermittent ScvO 2 by using standard blood gas measurements. These results were compared to those obtained by cerebral near infrared spectroscopy (cNIRS). Setting: Tertiary pediatric cardiac intensive care unit (PCICU). Methods and main results: A retrospective study was conducted in consecutive patients who were monitored with a 4.5 or 5.5 F PediaSat catheter into the right internal jugular vein. An in vivo calibration was performed once the patient was transferred to the PCICU and re-calibration took place every 24 hours thereafter. Each patient had a NIRS placed on the forehead. Saturations were collected every 4 hours until extubation. Ten patients with a median age of 2.2 (0.13-8.5) years and a weight of 12.4 (3.9-24) kg were enrolled. Median sampling time was 32 (19-44) hours: 64 pairs of PediaSat and ScVO2 saturations showed a poor correlation (r=0.62, 95% CI 44-75; p<0.0001) and Bland Altman analysis for repeated measures showed an average difference of 0.34 with a standard deviation of 7,9 and 95% limits of agreement from -15 to 16. Thirty-six pairs of cNIRS and ScVO2 saturations showed a fair correlation (r=0.79, 95% CI 0.60-0.89; p<0.0001) an average difference of -1.4 with a standard deviation of 6 and 95% limits of agreement from -13 to 10. Analysis of median percentage differences between PediaSat and ScvO2 saturation over time revealed that, although not statistically significant, the change in percentage saturation differences was clinically relevant after the 8th hour from calibration (from -100 to +100%). Conclusion: PediaSat catheters showed unreliable performance in our cohort. It should be further investigated whether repeating calibrations every 8 hours may improve the accuracy of this system. CNIRS may provide similar results with a lower invasiveness.

Usefulness of central venous oxygen saturation monitoring during bidirectional Glenn shunt

A PediaSat™ oximetry catheter (PediaSat: Edwards Lifesciences Co., Ltd., Irvine, CA, U. S. A.), which facilitates continuous measurement of central venous oxygen saturation (ScvO2), may be useful for surgery for pediatric congenital heart disease. We used PediaSat during a bidirectional Glenn shunt. The patient was a 13-month-old boy. Under a diagnosis of left single ventricle (pulmonary atresia, right ventricular hypoplasia, atrial septal defect) and residual left aortic arch/left superior vena cava, a modified right Blalock-Taussig shunt was performed. Cyanosis deteriorated, so a bidirectional Glenn shunt was scheduled. After anesthesia induction, a 4.5 Fr double-lumen (8 cm) PediaSat was inserted through the right internal jugular vein for continuous ScvO2 monitoring. Furthermore, the probe of a near-infrared, mixed blood oxygen saturation-measuring monitor was attached to the forehead for continuous monitoring of the regional brain tissue mixed blood oxygen saturation (rSO2) (INVOS™ 5100C, Covidien; Boulder, CO, U. S. A.). Blockage of the right pulmonary artery and right superior vena cava decreased the oxygen saturation, ScvO2, and rSO2, but increased the central venous pressure. Although changes in ScvO2 were parallel to those in rSO2, the former showed more marked changes. A combination of ScvO2 and rSO2 for monitoring during Glenn shunt may be safer.

Recent Less-invasive Circulatory Monitoring during Renal Transplantation

For anesthetic management during renal transplantation, it is necessary to maintain the blood flow and function of the transplanted kidney by performing massive fluid management and stabilizing blood pressure. We report anesthetic management for renal transplantation with a less-invasive circulatory monitoring system (Edwards Life Sciences Co., Ltd., Irvine, California, U.S.A.). In November 2010, renal transplantation was started in our hospital, and performed in 6 patients. In the first patient, fluid/circulatory management was conducted by connecting a standard arterial line and a standard central venous (CV) line. In the second patient, a FloTrac(TM) system and a standard CV line were used. In the third patient, a standard arterial line and a PreSep(TM) CV Oximetry Catheter were used. In the fourth and fifth patients, a FloTrac(TM) and a PreSep(TM) were used. In the latest patient, FloTrac(TM) and PreSep(TM) were connected to an EV1000(TM) Clinical Platform for fluid/circulatory management. The establishment of high-visibility monitors was useful for evaluating the condition and confirming the effects. As there are marked changes in hemodynamics, the CV pressure, which has been used as a parameter of fluid management, is not reliable in renal failure patients with a high incidence of cardiovascular complications. Advances in noninvasive circulatory monitoring with dynamic indices may improve the safety of anesthetic management during renal transplantation.

Prolonged Central Venous Desaturation Measured by Continuous Oximetry is Associated With Adverse Outcomes in Pediatric Cardiac Surgery

BACKGROUND The role of continuous central venous oxygen saturation (ScvO₂) oximetry during pediatric cardiac surgery for predicting adverse outcomes is not known. Using a recently available continuous ScvO₂ oximetry catheter, we examined the association between venous oxygen desaturations and patient outcomes. We hypothesized that central venous oxygen desaturations are associated with adverse clinical outcomes. METHODS Fifty-four pediatric patients undergoing cardiac surgery were prospectively enrolled in an unblinded observational study. ScvO₂ was measured continuously in the operating room and for up to 24 h post-Intensive Care Unit admission. The relationships between ScvO₂ desaturations, clinical outcomes, and major adverse events were determined. RESULTS More than 18 min of venous saturations less than 40% were associated with major adverse events with 100% sensitivity and 97.6% specificity. Significant correlations resulted between the ScvO₂ area under the curve less than 40% and creatinine clearance at 12 h in the Intensive Care Unit (r = -0.58), Intensive Care Unit length of stay (r = 0.56), max inotrope use (r = 0.52), inotrope use at 24 h (r = 0.40), inotrope index score (r = 0.39), hospital length of stay (r = 0.36), and length of intubation (r = 0.32). CONCLUSIONS We demonstrate that ScvO₂ desaturations by continuous oximetry are associated with major adverse events in pediatric patients undergoing cardiac surgery. The most significant associations with major adverse events are seen in patients with greater than 18 min of central venous saturations less than 40%. Our results support the further investigation of ScvO₂ as a potential target parameter in high-risk pediatric patients to minimize the risk of major adverse events.

Hemodynamic changes during robotic radical prostatectomy

Background:Effect on hemodynamic changes and experience of robot-assisted laparoscopic radical prostatectomy (RALRP) in steep Trendelenburg position (45°) with high-pressure CO2 pneumoperitoneum is very limited. Therefore, we planned this prospective clinical trial to study the effect of steep Tredelenburg position with high-pressure CO2 pneumoperitoneum on hemodynamic parameters in a patient undergoing RALRP using FloTrac/Vigileo™1.10.Methods:After ethical approval and informed consent, 15 patients scheduled for RALRP were included in the study. In the operation room, after attaching standard monitors, the radial artery was cannulated. Anesthesia was induced with fentanyl (2 μg/kg) and thiopentone (4–7 mg/kg), and tracheal intubation was facilitated by vecuronium bromide (0.1 mg/kg). The patient's right internal jugular vein was cannulated and the Pre Sep™ central venous oximetry catheter was connected to it. Anesthesia was maintained with isoflurane in oxygen and nitrous oxide and intermittent boluses of vecuronium. Intermittent positive-pressure ventilation was provided to maintain normocapnea. After CO2 pneumoperitoneum, position of the patient was gradually changed to 45° Trendelenburg over 5 min. The robot was then docked and the robot-assisted surgery started. Intraoperative monitoring included central venous pressure (CVP), stroke volume (SV), stroke volume variation (SVV), cardiac output (CO), cardiac index (CI) and central venous oxygen saturation (ScvO2).Results:After induction of anesthesia, heart rate (HR), SV, CO and CI were decreased significantly from the baseline value (P>0.05). SV, CO and CI further decreased significantly after creating pneumoperitoneum (P>0.05). At the 45° Trendelenburg position, HR, SV, CO and CI were significantly decreased compared with baseline. Thereafter, CO and CI were persistently low throughout the 45° Trendelenburg position (P=0.001). HR at 20 min and 1 h, SV and mean arterial blood pressure after 2 h decreased significantly from the baseline value (P>0.05) during the 45° Trendelenburg position. CVP increased significantly after creating pneumoperitoneum and at the 45° Trendelenburg position (after 5 and 20 min) compared with the baseline postinduction value (P>0.05). All these parameters returned to baseline after deflation of CO2 pneumoperitoneum in the supine position. There were no significant changes in SVV and ScvO2 throughout the study period.Conclusions:The steep Trendelenburg position and CO2 pneumoperitoneum, during RALRP, leads to significant decrease in stroke volume and cardiac output.

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.

Prolonged Central Venous Desaturation Measured by Continuous Oximetry Is Associated with Adverse Outcomes in Pediatric Cardiac Surgery

The role of continuous central venous oxygen saturation (ScvO₂) oximetry during pediatric cardiac surgery for predicting adverse outcomes is not known. Using a recently available continuous ScvO₂ oximetry catheter, we examined the association between venous oxygen desaturations and patient outcomes. We hypothesized that central venous oxygen desaturations are associated with adverse clinical outcomes. Fifty-four pediatric patients undergoing cardiac surgery were prospectively enrolled in an unblinded observational study. ScvO₂ was measured continuously in the operating room and for up to 24 h post-Intensive Care Unit admission. The relationships between ScvO₂ desaturations, clinical outcomes, and major adverse events were determined. More than 18 min of venous saturations less than 40% were associated with major adverse events with 100% sensitivity and 97.6% specificity. Significant correlations resulted between the ScvO₂ area under the curve less than 40% and creatinine clearance at 12 h in the Intensive Care Unit (r = -0.58), Intensive Care Unit length of stay (r = 0.56), max inotrope use (r = 0.52), inotrope use at 24 h (r = 0.40), inotrope index score (r = 0.39), hospital length of stay (r = 0.36), and length of intubation (r = 0.32). We demonstrate that ScvO₂ desaturations by continuous oximetry are associated with major adverse events in pediatric patients undergoing cardiac surgery. The most significant associations with major adverse events are seen in patients with greater than 18 min of central venous saturations less than 40%. Our results support the further investigation of ScvO₂ as a potential target parameter in high-risk pediatric patients to minimize the risk of major adverse events.

Evaluation of a new pediatric continuous oximetry catheter

To evaluate the accuracy of central venous oxygen saturation recordings from a new in-line pediatric oximetry catheter. Prospective, observational study. Eighteen pediatric patients who needed central venous access for monitoring and/or treatment between January 2006 and June 2006 in the pediatric intensive care unit of the Hospital for Sick Children in Toronto, Canada. Measurements were done at the baseline and then every 4-8 hrs. The monitor was calibrated in vivo at the baseline and then daily. In vitro calibration of the monitor was also performed in the last five patients. The hemoglobin value was updated when there was a significant change. The maximum duration of sampling was 72 hrs (if indicated). There were 131 measurements in 17 patients; each subject had a different number of paired measurements (median 5). Three patients were excluded due to violation of the protocol, and 113 measurements were left in analysis. The mean difference of catheter value from the laboratory value was -1.01 (median 0). The interquartile range was 5. The difference of both methods was evenly distributed as per a Bland-Altman plot, with one patient's data lying outside of the comparable limits of ± 1.96 sd from the mean differences. The relationship of the difference between the catheter data and the lab data to the independent variables (age, weight, gender, catheter tip, diagnosis, and signal quality index) was estimated by using the multiple regression analysis (version 9.1, SAS Institute, Cary, NC). All variables were eliminated. The Pearson correlation coefficient between lab-mixed venous oxygen saturation and oximetry catheter readings for measurements was 0.88. In this limited number of patients, use of the PediaSat venous oximetry catheter was safe and had good agreement with co-oximetry-measured values.

Clinical usefulness of continuous central venous oxygen saturation measurement for postoperative management of patients following transthoracic esophagectomy for carcinoma

Monitoring of central venous blood oxygen saturation (ScvO2) has recently become easier and safer to perform, but its clinical usefulness following esophagectomy has yet to be established. This study evaluated the use of continuous monitoring of ScvO2 in this setting, focusing on its relationship with hemoglobin (Hb) concentrations, and reconsideration about an appropriate indication of red blood cell transfusion from the aspect of tissue oxygen balance. A total of 40 patients were assessed following transthoracic esophagectomy for carcinoma. ScvO2 was measured via a fiberoptic central venous oximetry catheter, postoperatively until discharge from the ICU. Hb was also measured preoperatively and every 8 h postoperatively. In correlation between ScvO2 and Hb values, ScvO2 could still be greater than 70% in patients with a Hb around 7 g/dl who did not have a bleeding event and maintained a stable circulation. Even when Hb dilution ratio (sampling Hb/preoperative Hb) decreased to around 60% of the preoperative value, ScvO2 could remain above 65%. Patients who had severe bleeding exhibited a marked decrease of the ScvO2 value before blood transfusion, but the trend was clearly seen to be a gradual increase of ScvO2 during transfusions. Hb supply is essentially unnecessary if the balance of oxygen supply/demand in tissues is well maintained. ScvO2 may be a better indicator of a physiological need for blood than Hb in postesophagectomy patients. ScvO2 is not influenced by hemodilution and lowering of Hb to around 60% of the preoperative value. As well as being a useful start indicator for blood transfusions, ScvO2 could also become a stop indicator.

Continuous Central Venous Oxygen Saturation Monitoring under Varying Physiological Conditions in an Animal Model

We compared saturations from a paediatric central venous oximetry catheter with co-oximetry values with changes in drug infusions, intravascular blood volume and hypoxia in an animal model. Piglets (large white) were anaesthetised, intubated and mechanically ventilated. PediaSat oximetry catheters were placed in the superior vena cava via jugular vein cut-down and in the inferior vena cava percutaneously via the femoral vein. A carotid arterial catheter was placed via cut-down for blood sampling and pressure monitoring. Anaesthesia was maintained with continuous thiopentone and supplemental morphine. Haemodynamics (heart rate, mean arterial blood, central venous pressure), fibreoptic ScvO2 (ScvO2-inferior) from inferior vena cava, fibreoptic ScvO2 (ScvO2-superior) from superior vena cava and blood gas oximetry (ScvO2-co-ox) were measured simultaneously at predetermined intervals during increasing adrenaline and sodium nitroprusside infusions and during increasing hypoxia and hypovolaemia. There was good agreement of both superior vena cava and inferior vena cava ScvO2 catheters with co-oximetry during adrenaline and sodium nitroprusside infusions. During the hypoxia study there was good agreement between the co-oximeter to ScvO2-superior catheter but poor agreement with to the inferior vena cava catheter samples. In the hypovolaemic phase of the experiment there was good agreement between the measured co-oximetry value and ScvO2-superior catheter until the mean blood pressure reached 43 mmHg. The oximetry catheter is capable of identifying changes in ScvO2 under physiological conditions usually encountered in clinical medicine but was less accurate at the extremes of physiology and when placed in the inferior vena cava catheter especially during hypovolaemia and hypoxia.

The PediaSat continuous central SvO2 monitoring system does not reliably indicate state or course of central venous oxygenation

The present study compares the accuracy of a new continuous venous oxygenation monitoring system (PediaSat Oximetry Catheter) with laboratory blood oximetry in paediatric surgical patients. Children and adolescents undergoing cardiac, orthopaedic or craniofacial surgery with major blood loss were included. A 4.5 Fr two-lumen or 5.5 Fr three-lumen central venous oximetry catheter (SPediaSatcvO2) was inserted preoperatively into the superior vena cava. After in-vivo calibration of the PediaSat system, repeated blood samples were obtained from the distal port of the venous catheter and oximetrically analysed for haemoglobin and central venous oxygen saturation (SCO-OXcvO2). Central venous oxygen saturation values measured by the PediaSat (SPediaSatcvO2) were compared with co-oximetry (SCO-OXcvO2) values from the simultaneously taken blood samples by Bland-Altman and simple regression analyses. Overall, 142 data pairs from 27 patients, aged from 0.6 to 19.0 years (median 5.3 years) were analysed. SPediaSatcvO2 and SCO-OXcvO2 values ranged from 57 to 98% and from 57.1 to 95.8%, respectively. Correlation between SPediaSatcvO2 and SCO-OXcvO2 was poor with r equal to 0.28 (P < 0.0001). SPediaSatcvO2 overestimated SCO-OXcvO2 (mean bias +2.6%), but limits of agreement (+/-2 SD of bias) were unacceptably high (-14.4/+19.6%). Sensitivity and specificity of SPediaSatcvO2 to indicate a fall or rise of SCO-OXcvO2 between two subsequent measurements were only 0.42 and 0.24, respectively. In paediatric and adolescent patients undergoing major surgery, the PediaSat system did not reliably reflect SCO-OXcvO2 values and cannot replace repeated invasive ScvO2 assessments in the clinically relevant range of ScvO2.

Tissue Oxygenation Does Not Predict Central Venous Oxygenation in Emergency Department Patients With Severe Sepsis and Septic Shock

This study sought to determine whether tissue oxygenation (StO(2)) could be used as a surrogate for central venous oxygenation (ScVO(2)) in early goal-directed therapy (EGDT). The study enrolled a prospective convenience sample of patients aged > or =18 years with sepsis and systolic blood pressure <90 mm Hg after 2 L of normal saline or lactate >4 mmol, who received a continuous central venous oximetry catheter. StO(2) and ScVO(2) were measured at 15-minute intervals. Data were analyzed using a random coefficients model, correlations, and Bland-Altman plots. There were 284 measurements in 40 patients. While a statistically significant relationship existed between StO(2) and ScVO(2) (F(1,37) = 10.23, p = 0.002), StO(2) appears to systematically overestimate at lower ScVO(2) and underestimate at higher ScVO(2). This was reflected in the fixed effect slope of 0.49 (95% confidence interval [CI] = 0.266 to 0.720) and intercept of 34 (95% CI = 14.681 to 50.830), which were significantly different from 1 and 0, respectively. The initial point correlation (r = 0.5) was fair, but there was poor overall agreement (bias = 4.3, limits of agreement = -20.8 to 29.4). Correlation between StO(2) and ScVO(2) was fair. The two measures trend in the same direction, but clinical use of StO(2) in lieu of ScVO(2) is unsubstantiated due to large and systematic biases. However, these biases may reflect real physiologic states. Further research may investigate if these measures could be used in concert as prognostic indicators.

In-vitro evaluation of the PediaSat continuous central venous oxygenation monitoring system

In-vitro performance of the PediaSat system for continuous monitoring of central venous oxygen saturation by spectrophotometry has been evaluated. PediaSat continuous fibre-optic oximetry catheters were inserted in a black testing chamber, connected with an extracorporeal circuit and filled with human whole blood. Oxygen inflow into the cardiopulmonary bypass system was varied, and the testing chamber was perfused with blood flow of 1000 ml min(-1). Oxygen saturation values measured by PediaSat (S PediaSat O2) were compared with cooximetry (S CO-OX O2) values from simultaneously taken blood samples by Bland-Altman and simple regression analyses. Fifty data pairs were obtained. S PediaSat O2 and S CO-OX O2 values ranged between 28-98 and 24.9-99.5%, respectively. Correlation between S PediSat O2 and S CO-OX O2 was high with an r2 value equal to 0.96 (P < 0.0001). Overall, S PediaSat O2 only slightly overestimated S CO-OX O2 (mean bias +2.9%), and limits of agreement (+/-2 SD of bias) were acceptable (-6.8/+12.6%). Sensitivity and specificity of the first differences of S PediaSat O2 and S CO-OX O2 were 1.0 and 0.92, respectively. Subgroup analysis of S CO-OX O2 values below 70% resulted in an overestimation by S PediaSat O2, with a mean bias of +5.2% and limits of agreement of -4.7 and +15.1%. The current version of the PediaSat system does not reliably reflect S CO-OX O2 values below 70%, but it seems to be a useful tool providing an accurate trend of continuous central venous oxygen saturation.