Does a digital regional nerve block improve the accuracy of noninvasive hemoglobin monitoring?

Department of Anesthesia and Perioperative Care, University of California, San Francisco, 521 Parnassus Avenue, C317, San Francisco, CA, 94143-0648, USA, .
Journal of Anesthesia (Impact Factor: 1.12). 08/2012; DOI: 10.1007/s00540-012-1452-0
Source: PubMed

ABSTRACT BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

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    ABSTRACT: The purpose of this prospective study was to evaluate the accuracy and trending ability of a four-wavelength pulse-total hemoglobinometer that continuously and noninvasively measures hemoglobin in surgical patients. With IRB approval and informed consent, spectrophotometric hemoglobin (SpHb) was measured with a pulse-total hemoglobinometer manufactured by Nihon Kohden Corp (Tokyo, Japan) and compared to the CO-oximeter equipped with blood gas analyzer. Two hundred twenty-five samples from 56 subjects underwent analysis. Bland-Altman analysis revealed that the bias ± precision of the current technology was 0.0 ± 1.4 g/dl and -0.2 ± 1.3 g/dl for total samples and samples with 8 < Hb < 11 g/dl, respectively. The percentages of samples with intermediate risk of therapeutic error in error grid analysis and the concordance rate of 4-quadrant trending assay was 17 % and 77 %, respectively. The Cohen kappa statistic for Hb < 10 g/dl was 0.38, suggesting that the agreement between SpHb and CO-oximeter-derived Hb was fair. Collectively, wide limits of agreement, especially at the critical level of hemoglobin, and less than moderate agreement against CO-oximeter-derived hemoglobin preclude the use of the pulse-total hemoglobinometer as a decision-making tool for transfusion.
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