Accuracy and precision of ScvO2 measured with the CeVOX-device: A prospective study in patients with a wide variation of ScvO2-values

Abstract

IntroductionCentral-venous oxygen saturation (ScvO2) is a key parameter of hemodynamic monitoring and has been suggested as therapeutic goal for resuscitation. Several devices offer continuous monitoring features. The CeVOX-device (Pulsion Medical Systems) uses a fibre-optic probe inserted through a conventional central-venous catheter (CVC) to obtain continuous ScvO2.ObjectivesSince there is a lack of studies validating the CeVOX, we prospectively analyzed data from 24 patients with CeVOX-monitoring. To increase the yield of lower ScvO2-values, 12 patients were equipped with a femoral CVC.MethodsDuring the 8h study period ScvO2_CeVOX was documented immediately before withdrawal of blood to measure ScvO2 by blood gas analysis (ScvO2_BGA) 6min, 1h, 4h, 5h and 8h after the initial calibration. No further calibrations were performed.ResultsIn patients with jugular CVC (primary endpoint; 60 measurements), bias, lower and upper limits of agreement (LLOA; ULOA) and percentage error (PE) of the estimate of ScvO2 (ScvO2_CeVOX_jug) were acceptable with 0.45%, -13.0%, 13.9% and 16.6%, respectively.As supposed, ScvO2 was lower in the femoral compared to the jugular measurements (69.5±10.7 vs. 79.4±5.8%; p<0.001). While the bias (0.64%) was still acceptable, LLOA (-23.8%), ULOA (25.0%) and PE (34.5%) were substantially higher for femoral assessment of ScvO2 by the CeVOX (ScvO2_CeVOX_fem).Analysis of the entire data-pool with jugular as well as femoral CVCs allowed for a multivariate analysis which demonstrated that the position of the CVC per se was not independently associated with the bias ScvO2_CeVOX—ScvO2_BGA. The amount of the bias |ScvO2_CeVOX–ScvO2_BGA| was independently associated with the amount of the change of ScvO2_CeVOX compared to the initial calibration to ScvO2_BGA_baseline (|ScvO2_CeVOX—ScvO2_BGA_baseline|) as well as with low values of ScvO2_BGA_baseline. Furthermore, increasing time to the initial calibration was associated to the amount of the bias with borderline significance.A statistical model based on |ScvO2_CeVOX—ScvO2_BGA_baseline| and “time to last calibration” derived from an evaluation dataset (80 of 120 datasets, 16 of 24) provided a ROC-AUC of 0.903 to predict an amount of the bias |ScvO2_CeVOX–ScvO2_BGA| ≥5% in an independent validation group (40 datasets of 8 patients).ConclusionThese findings suggest that the CeVOX device is capable to detect stability or instability of ScvO2_BGA. ScvO2_CeVOX accurately estimates ScvO2_BGA in case of stable values. However, intermittent measurement of ScvO2_BGA and re-calibration should be performed in case of substantial changes in ScvO2_CeVOX compared to baseline. Therefore, continuous measurement of ScvO2 with the CeVOX cannot replace ScvO2_BGA in instable patients. On the other hand, CeVOX might be useful for the monitoring of stable patients as a pre-test tool for more differentiated monitoring in case of changes in ScvO2_CeVOX.

The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation

“…Mixed venous oxygen saturation in the pulmonary artery can be obtained by introducing a Swan–Ganz catheter into the pulmonary artery and measuring the oxygen saturation in an extracted sample of mixed venous blood via blood gases analysis. Pulmonary artery catheters are introduced through a central vein, the right atrium and ventricle, and because their use has been limited, measurement of oxygen saturation in central veins—superior and inferior vena cava—has been suggested as a surrogate for mixed venous oxygen saturation measurement [ 27 , 28 , 29 ].…”

“…The oximetric probe consisted of two optical fibers with a small gap between their tips ( Figure 2 ), which was introduced into the vein. One of the fibers transmits two-wavelengths of light into the blood in the gap between the optical fibers and the second fiber guides the transmitted light to the detector [ 17 , 29 , 30 ].…”

“…Like the Millikan’s oximeter, the intravenous oximeter needs calibration in a blood sample before each continuous examination , according to the manufacturer’s instructions, using blood gases analysis. Limits of agreement of 7–16% were found between the optical measurement and blood gases analysis on blood samples extracted from the same vein [ 28 , 29 ].…”

Central hemodynamic monitoring in patients with cardiogenic shock

“…Подавляющее большинство авторов считают, что методика не работает, как заявлено. Часть придерживаются мнения о том, что простое измерение газов крови более информативно, что данная система не работает у нестабильных пациентов [28]. ), LIDCOplus может быть в некоторой степени заменой инвазивному мониторингу в части точности измерений [29].…”

Assessment of Regional Perfusion and Organ Function: Less and Non-invasive Techniques

“…A major advantage of guiding therapy by lactate levels is the easiness of measurement which does not require central-venous access. Similar as for S v O 2 by S cv O 2 devices providing continuous measurement are available (7, 17).…”