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

OBJECTIVE: 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.

DESIGN: Observational study.

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

PARTICIPANTS: The study comprised 29 adult patients.

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

MEASUREMENTS AND MAIN RESULTS: 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.

CONCLUSION: 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.