Monitoring of central venous oxygen saturation versus mixed venous oxygen saturation in critically ill patients

Abstract

Continuous monitoring of mixed venous (SvO2) and central venous (ScO2) oxygen saturation was compared in 7 critically-ill patients (Apache II score: 19 +/- 2.1) to determine whether or not information derived from ScO2 were reliable in clinical practice. Patients were catheterized with both a pulmonary artery (PA) and a central venous (CV) catheter, each of them mounted with fiberoptic sensors (Opticath PA Catheter P7110 and Opticath CV Catheter U440, Abbott). A total of 580 comparative measurements were obtained during periods without and with therapeutic interventions (drug-titration, bronchial suction, use of PEEP, changes in FiO2 ...). The systematic error between the 2 measurement techniques was 0.6% and 0.3% in periods with and without therapeutic interventions, respectively. The variability between the 2 techniques was 10% for both periods. Differences between the values were greater than or equal to 5% in 49% of values during periods of stability and in 50% of values during periods with therapeutic interventions. There were poor correlations between the values during periods without (r = 0.48) and with therapeutic interventions (r = 0.62). Better, but still less than ideal, correlations were obtained with changes in SvO2 and ScO2 during periods without (r = 0.70) and with therapeutic interventions (r = 0.77). Although there is a need to develop a simple technique to monitor mixed venous oxygen saturation, the present study indicates that ScO2 monitoring was not reliable in the study patients.

No agreement of mixed venous and central venous saturation in sepsis, independent of sepsis origin

“…On the basis of the present study, the net effect of these factors seems unpredictable. Our results seem concordant with earlier findings [6,8,16]. The first study described a small heterogeneous group of patients with septic shock.…”

Central Venous and Mixed Venous Oxygen Saturation in Critically Ill Patients

“…These results are supported by Lee et al [16], who found a good correlation in normal subjects (r = 0.88) but not in patients in shock (r = 0.73). Martin et al [17]studied 7 critically ill patients with 448 consecutive measurements of the two parameters and found that there is a poor correlation between them during periods with or without medical intervention (r = 0.48 and 0.62, respectively) and they concluded that the two parameters are not interchangeable. They also found that the difference between the two parameters was >5% in 50% of the measurement, that abrupt changes in SvO 2 were not detected by ScvO 2 in 18% of the measurements and that there is poor correlation between changes in the two parameters during periods without (r = 0.70) and with therapeutic interventions (r = 0.77).…”

“…However, he found a substantial improvement in correlation (r = 0.94) when he compared oxygen content to oxygen saturation (by multiplication of saturation by a common hemoglobin value) and he concluded that the results are mathematically coupled to a degree that precludes final conclusions and thus necessitates further prospective evaluation. Finally, Vincent [19], using the data of Martin et al [17]concluded that ScvO 2 should not be considered as a reliable substitute for SvO 2 . However, the very small number of patients of this study and thus the dependent nature of the measurements make these results inaccurate for final results and conclusions.…”

Cardiopulmonary monitoring of shock

“…Central venous oxygen saturation (ScvO 2 ) can be measured from a venous blood gas drawn from any central venous catheter (preferably in the upper extremities), so it is often used as a practical substitute. Multiple studies have questioned the reliability of ScvO 2 to predict SvO 2 (even allowing for + 10% error) (18–21). ScvO 2 is generally regarded as not necessarily equivalent to SvO 2 but potentially useful for trending changes with therapy.…”