Minimally Invasive Determinations of Oxygen Delivery and Consumption in Cardiac Surgery: An Observational Study

Evaluate minimally invasive assessment of oxygen delivery (DO₂) and oxygen consumption (VO₂) and determine its level of agreement with the gold standard approach of those measurements in patients undergoing cardiac surgery.

Observational study.

Single center, VU University Medical Center (Amsterdam, The Netherlands).

The study comprised 29 adult patients.

Parallel measurements of invasive and minimally invasive parameters required for the calculation of DO₂ and VO₂.

Measurements were performed after anesthesia induction (T1) and before sternal closure (T2) in adult cardiac surgery. The invasive approach included arterial and pulmonary artery catheter-derived blood sampling and cardiac output measurements. The minimally invasive approach included pulse oximetry, point-of-care hemoglobin, Nexfin-based cardiac output, and central venous catheter-derived blood sampling. Level of agreement was determined using Bland-Altman analysis and percentage error. DO₂ and VO₂ levels were determined in patients 71 ± 8 years old. DO₂ measurements showed a level of agreement of -17 ± 57 L/min/m² and -18 ± 72 L/min/m² with percentage errors of 35% and 38% at T1 and T2, respectively. VO₂ assessment showed a level of agreement of -5 ± 18 L/min/m² and -12 ± 22 L/min/m², with percentage errors of 47% at T1 and T2. The highest percentage errors were for cardiac output measurements, 33% and 28% at T1 and T2, respectively.

Agreement between minimally invasive and invasive DO₂ and VO₂ determinations is, moderate and poor, respectively. These findings may be explained by the poor agreement between minimally invasive and invasive cardiac output measurements.