CeVOX for continuous central venous oxygenation measurement in patients undergoing off-pump coronary artery bypass grafting

Objective

The aim of this study was to compare central venous O₂ saturation (ScvO₂) [1] measured continuously by the CeVOX (Pulsion Medical System, Munich, Germany) device (CScvO₂) with ScvO₂ determined by blood gas co-oximetry (BScvO₂)^.

Methods

Twenty-five patients undergoing elective off-pump coronary artery bypass grafting were studied during operation (OP) and during their ICU stay (ICU). OP/ICU measurement started after in vivo calibration of CeVOX. BScvO₂ and CScvO₂ readings were recorded at intervals of 30 minutes during OP and 120 minutes during ICU. Bland–Altman analysis and Pearson correlation was performed for overall OP, overall ICU, consecutive measurements during OP ≤ 1 hour, 1–2 hours and 2–3 hours after initial calibration (OP1–OP3, respectively) as well as during ICU ≤ 4 hours, 4–8 hours, 8–12 hours and 12–16 hours after recalibration (ICU1–ICU4, respectively).

Results

Five hundred and nine matched sets of data were obtained; the BScvO₂/CScvO₂ range was 36–98.9%/46.5–99.0%, respectively. Overall mean bias ± 2SD was -1.2 ± 13.8% for CScvO₂–BScvO₂ during OP and -2.6 ± 16.2% during ICU. The correlation coefficient (r²) for CScvO₂ vs BScvO₂ was 0.614 (OP) and 0.174 (ICU). Statistics for OP1–OP3 were comparable, whereas mean bias ± 2SD increased and r² decreased during ICU1–ICU4 (Table 1).

Table 1.

	OP1	OP2	OP3	ICU1	ICU2	ICU3	ICU4
Mean bias ± 2SD (%)	-0.2 ± 13.9	+1.3 ± 9.6	+1.8 ± 16.6	-0.1 ± 12.0	-0.6 ± 15.4	-0.5 ± 13.8	-4.6 ± 16.9
r2 (P value)	0.580 (<0.001)	0.616 (<0.001)	0.513 (<0.001)	0.416 (<0.001)	0.514 (<0.001)	0.310 (0.001)	0.030 (0.247)

Conclusion

The results indicate that ScvO₂ can be reliably assessed by CeVOX. In order to maintain accurate measurements, scheduled re-calibrations at intervals <12 hours are mandatory.