, Volume 26, Issue 6, pp 845-850
Date: 01 Aug 2012

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

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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.