Clinical evaluation of a novel system for monitoring surgical hemoglobin loss

Abstract

Background: Accurate measurement of intraoperative blood loss is an important clinical variable in managing fluid resuscitation and avoiding unnecessary transfusion of blood products. In this study, blood lost onto laparotomy sponges during surgical cases was measured using a tablet computer programmed with a unique algorithm modeled after facial recognition technology. In this study, we assessed the accuracy and performance of the system in surgical cases.

Methods: In this prospective, multicenter study, 46 patients undergoing surgery with anticipated significant blood loss contributed laparotomy sponges for hemoglobin (Hb) loss measurement using the Triton System with Feature Extraction Technology (Gauss Surgical, Inc., Los Altos, CA). The Hb loss measured by the new system was compared with that measured by manual rinsing of the sponges. Accuracy was evaluated using linear regression and Bland-Altman analysis. In addition, the new system's calculation of blood volume loss was compared with the gravimetric method of estimating blood loss from intraoperative sponge weights.

Results: A significant positive linear correlation was noted between the new system's measurements and the rinsed Hb mass (r = 0.93, P < 0.0001). Bland-Altman analysis revealed a bias of 9.0 g and narrow limits of agreement (-7.5 to 25.5 g) between the new system's measures and the rinsed Hb mass. These limits were within the clinically relevant difference of ±30 g, which is approximately half of the Hb content of a unit of allogeneic whole blood. Bland-Altman analysis of the estimated blood loss on sponges using the gravimetric method demonstrated a bias of 466 mL (overestimation) with limits of agreement of -171 and 1103 mL, due to the presence of contaminants other than blood on the laparotomy sponges.

Conclusions: The novel mobile monitoring system provides an accurate measurement of Hb mass on surgical sponges as compared with that of manual rinsing measurements and is significantly more accurate than the gravimetric method. Further study is warranted to assess the clinical use of the technology.

Figures

Figure 1

Photograph demonstrating the sponge scanning and analysis process using the Triton System.

Figure 2

Plot of mHbTriton vs. the rinsed hemoglobin (Hb) mass demonstrates a strong positive linear association (r = 0.93 [95%CI 0.88–0.96], p < 0.0001).

Figure 3

Bland and Altman plot of the concordance between mHbTriton and the rinsed Hb mass per case (n = 46 measures). The solid blue lines represent the bias (mean difference) and the dashed lines represent the upper and the lower limits of agreement (bias +/−1.96 SD) for each plot.

Figure 4

Accuracy comparison of Triton system as compared with gravimetric method for all cases via plot of both (A) EBLTriton vs. EBLRinse (r = 0.94 [95%CI 0.89–0.97], p < 0.0001) and (B) EBLWeight vs. EBLRinse (r = 0.92 [95%CI 0.86–0.96], p < 0.0001). Blue line represents 100% correlation.

Figure 5

Bland and Altman plots of the concordance (A) between EBLTriton and EBLRinse, and (B) between EBLWeight and EBLRinse, per patient (n = 39 measures per method). The solid blue lines represent the bias (mean difference) and the dashed lines represent the upper and the lower limits of agreement (bias +/− 1.96 SD) for each plot.

Figure 6

Per-sponge accuracy comparison of Triton system as compared with gravimetric method for the 12 cases where sponges were measured individually. (A) Plot of EBLTriton vs. EBLRinse demonstrates a strong positive linear correlation on a per-sponge basis (r = 0.88 [95%CI 0.84–0.91], p < 0.0001), whereas (B) plot of EBLWeight vs. EBLRinse demonstrates a moderate positive linear correlation on a per-sponge basis (r = 0.60 [95%CI 0.49–0.69], p < 0.0001). Blue line represents 100% correlation.