Does a digital regional nerve block improve the accuracy of noninvasive hemoglobin monitoring?
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Blood hemoglobin (Hb) can be continuously monitored utilizing noninvasive spectrophotometric finger sensors (Masimo SpHb). SpHb is not a consistently accurate guide to transfusion decisions when compared with laboratory Co-Oximetry (tHb). We evaluated whether a finger digital nerve block (DNB) would increase perfusion and, thereby, improve the accuracy of SpHb.
Twenty adult patients undergoing spinal surgery received a DNB with lidocaine to the finger used for the monitoring of SpHb. SpHb–tHb differences were determined immediately following the DNB and approximately every hour thereafter. These differences were compared with those in our previously reported patients (N = 20) with no DNB. The SpHb–tHb difference was defined as “very accurate” if <0.5 g/dL and “inaccurate” if >2.0 g/dL. Perfusion index (PI) values at the time of each SpHb–tHb measurement were compared.
There were 57 and 78 data points in this and our previous study, respectively. The presence of a DNB resulted in 37 % of measurements having SpHb values in the “very accurate group” versus 12 % in patients without a DNB. When the PI value was >2.0, only 1 of 57 DNB values was in the “inaccurate” group. The PI values were both higher and less variable in the patients who received a DNB.
A DNB significantly increased the number of “very accurate” SpHb values and decreased the number of “inaccurate” values. We conclude that a DNB may facilitate the use of SpHb as a guide to transfusion decisions, particularly when the PI is >2.0.
KeywordsAnesthesia techniques regional Blood-flow-peripheral Blood-hemoglobin Blood-transfusion Measurement techniques
The authors thank Barbara A. Grimes, PhD (Department of Biostatistics and Epidemiology, University of California, San Francisco, San Francisco, CA) for her statistical consultation, and James E. Caldwell, MB, ChB, Professor, and Judith Hellman, MD, Associate Professor (Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, CA) for their scholarly review of our manuscript. The authors also thank the Masimo Corporation. This work was supported by the Department of Anesthesia and Perioperative Care at the University of California, San Francisco. The Masimo Corporation provided the Radical 7 Pulse Co-Oximeter with SpHb™, sensors, and software for the study.
Conflict of interest
Ronald D. Miller received honoraria from Masimo. Dr. Miller is a paid member of the Masimo Scientific Advisory Board, the manufacturer of the SpHb, and has received travel reimbursement in the past. The Masimo Corporation provided the Radical 7 Pulse Co-Oximeter with SpHb™, sensors, and software for the study. The other study investigators report no conflict of interest.
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