Background and Goal of Study: 
  Due to large fluid volume shift or blood loss may occur during liver transplantation surgery, rapid and accurate monitoring hemoglobin level and making decision of blood transfusion is important for anesthesiologist.       
  Masimo Radical-7TM(Rad-7TM) pulse co-oximeter is a noninvasive continuous hemoglobin(HbNi) monitoring device, which has been reported accurate in health adults, but might be less accurate in patient with shock, hypothermia or vasoconstriction. Current data of its  application in liver transplantation surgery are still limited. This study is to evaluate the accuracy of hemoglobin measurement by Masimo Rad-7TM in patient undergoing orthotopic liver transplantation.

Materials and Methods: 
  From 2013/12 to 2017/01, Thirty-five patients undergoing orthotopic liver transplantation were enrolled. Noninvasive Hb (HbNi), gas analyzer Hb (HbGas) and central laboratory Hb (HbLab) were measured every hour during the whole period of surgery. 
  The relationship between HbGas, HbNi and HbLab was assessed using a 4-quadrant plot, linear regression, and modified Bland-Altman analyses.

Results and Discussion: 
  232 and 284 paired measurements of HbNi/ HbLab and HbGas/ HbLab were obtained. The correlation coefficient between HbNi and HbLab was 0.616 (p< 0.0001), and between HbGas and HbLab was 0.847 (p< 0.0001). 
  Bland-Altman plots for HbNi and HbGas compared to HbLab are depicted in Figure 1. Compared to HbLab, the mean bias ± SD and 95% limits of agreement was 1.97 ± 1.59 g/dL and -1.1 to 5.1 for the noninvasive Hb, 0.39 ± 0.89 g/dL and -1.4 to 2.1 for the gas analyzer Hb. 
  Four-quadrant plots are depicted in Figure 2. The concordance rate (a measure of the number of data points in 1 of the 2 quadrants of agreement) of HbNi/HbLab and HbGas/ HbLab was 75% and 83.4% with a central exclusion zone of 0.5 g/dL. 

Conclusions: 
We found that hemoglobin noninvasively obtained by the Masimo Radical-7TM system overestimated the standard value by the central laboratory in patients undergoing orthotopic liver transplantation.   
    Hemoglobin level obtained from gas analyzer has less bias and better concordance rate than from Masimo Radical-7TM system. It is not clinically acceptable to make a decision of transfusion based on the noninvasive hemoglobin measurement. However, there is an acceptable reliability in tracking changes in intra-operative hemoglobin levels. Because the liver trans-plantation is a time-consuming procedure, the Masimo Radical-7TM system could still provide potential clinical values in continuous monitoring intraoperative changes of serum hemoglobin levels.

Non-invasive hemoglobin measurement by Masimo Radical-7TM pulse co-oximeter in patient undergoing orthotopic liver transplantation