This study will establish the feasibility and preliminary validity of real-time oxygen delivery index (DO₂i) monitoring using noninvasive hemoglobin (SpHb, Masimo) and minimally invasive cardiac output (FloTrac, Edwards) in cardiac surgery patients.
Study Type
OBSERVATIONAL
Enrollment
150
The SpHb monitor is an FDA approved device being used according to its approved indications. No additional invasive procedures, blood draws, or interventions are performed for research purposes.
University of Minnesota
Minneapolis, Minnesota, United States
Agreement Between SpHb-Based and Pulmonary Artery Catheter Oxygen Delivery Index
Bias and 95% limits of agreement between monitor-derived DO₂i (calculated from continuous SpHb and FloTrac cardiac index) and pulmonary artery catheter DO₂i (calculated from arterial blood gas hemoglobin and Swan-Ganz cardiac index), analyzed using Bland-Altman method with mixed-effects modeling to account for repeated measures. Agreement is considered acceptable if percentage error is \<30%.
Time frame: Three intraoperative timepoints during cardiac surgery: baseline, post-heparin, and post-protamine
Directional Agreement for Changes in Oxygen Delivery Index
Four-quadrant concordance rate (with 15% exclusion zone) for directional changes in DO₂i between consecutive timepoints. Concordance is defined as agreement in direction of change (increase vs decrease) between monitor-derived and gold-standard DO₂i measurements. Scores range from 0- 100%, with higher percentages indicating better directional agreement.
Time frame: Changes between consecutive intraoperative timepoints (baseline to post-heparin, post- heparin to post-protamine) during cardiac surgery
Correlation Between Oxygen Delivery Index and Arterial Lactate
Pearson or Spearman correlation coefficient between DO₂i (both monitor-derived and gold- standard) and simultaneously measured arterial lactate concentration. Correlation coefficients range from -1 to +1, with negative values indicating inverse relationship between DO₂i and lactate.
Time frame: Three intraoperative timepoints during cardiac surgery: baseline, post-heparin, and post- protamine
Agreement Between FloTrac and Swan-Ganz Cardiac Index
Percentage error between FloTrac arterial pressure-based cardiac index and Swan-Ganz thermodilution continuous cardiac index. Percentage error is calculated as (1.96 × SD of differences) / mean cardiac index × 100%. Agreement is considered acceptable if percentage error is \<30%.
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Time frame: Three intraoperative timepoints during cardiac surgery: baseline, post-heparin, and post- protamine
Impact of Baseline SpHb Calibration on Agreement
Comparison of limits of agreement before and after in vivo SpHb calibration (baseline- adjusted SpHb using first arterial blood gas hemoglobin value as reference). Measured as change in bias and 95% limits of agreement between uncalibrated and baseline-calibrated SpHb-based DO₂i compared to gold standard.
Time frame: Three intraoperative timepoints during cardiac surgery: baseline, post-heparin, and post- protamine
SpHb Signal Usability Rate
Percentage of planned timepoints with valid SpHb signal defined by perfusion index (PI) ≥ 0.5. Scores range from 0-100%, with 100% indicating valid signal at all timepoints.
Time frame: Three intraoperative timepoints during cardiac surgery: baseline, post-heparin, and post- protamine
Perfusion Index Threshold for Acceptable SpHb Accuracy
Minimum perfusion index value associated with acceptable SpHb accuracy, defined as SpHb bias within ±1 g/dL of arterial blood gas hemoglobin. Perfusion index values range from 0-20%, with higher values indicating better peripheral perfusion.
Time frame: Three intraoperative timepoints during cardiac surgery: baseline, post-heparin, and post- protamine