Continuous Noninvasive Hemoglobin Monitoring: A Measured Response to a Critical Review

Abstract

Supplemental Digital Content is available in the text.

Published ahead of print March 5, 2015

Figure 1.

Changes in hemoglobin from a hematology analyzer compared with changes in SpHb, CO-Oximeter, and HemoCue (N = 471 measurements in 62 surgical intensive care subjects). Adapted from Frasca et al. 2011.

Figure 2.

Trend plot of a surgical case in which blinded SpHb values (red line) are shown with lab-Hb measurements from both a CO-Oximeter (blue circles) and hematology analyzer (purple triangles). Note in (A) the larger-than-expected difference between lab-Hb values from 2 different devices. B and C, How differences between lab-Hb and single SpHb values during a time of rapidly changing hemoglobin can be misleading. D, The variation between 2 lab-Hb devices can change. Actual patient trend plot courtesy of Masimo.

Figure 3.

Revision “K” SpHb sensors (shown in red) have less variability than earlier revision SpHb sensors (shown in dark blue) during side perfusion variation and fewer dropouts during low perfusion (0.3%–1% Perfusion Index, shown in cyan), demonstrating improved trending accuracy compared with lab-Hb (shown in blue diamonds). Actual patient trend plot courtesy of Masimo.

Figure 4.

Trend plot of a liver transplant surgery in which visible SpHb values (red line) are shown with lab-Hb measurements (purple triangles). The last lab-Hb value before the time marked as 7:57 was >8 g/dL. As the surgeon was closing and with no significant change in vital signs, SpHb values began to drop while pleth variability index (PVI) began to rise, which is associated with reduced intravascular volume status. Due to the changing SpHb values, another blood sample was taken, later revealing a lab-Hb <5 g/dL. The dropping SpHb values caused the surgeon to stop wound closure and re-explore the abdomen. A large volume of blood was found behind the liver and bleeding vessel repaired. The SpHb values decreased <3 g/dL, and RBC transfusion was initiated as hemodynamic instability occurred. The aggressive transfusion that followed resulted in an over transfusion as the SpHb reached 14 g/dL. Actual patient trend plot courtesy of Masimo.