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

Abstract

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.

Keywords: cardiac surgery; oxygen consumption; oxygen delivery; pulmonary artery catheter.