Evaluation of the accuracy of the masimo pronto compared to laboratory spectrophotometric method of intraoperative haemoglobin measurement

Background: Transfusion decisions intra-operatively are generally guided by accurate blood loss estimation and intermittent invasive haemoglobin measurement. We investigated the accuracy of non- invasive intraoperative haemoglobin measurement using the Masimo Pronto (SpHb) as compared to laboratory spectrophotometry (tHb). Methods and Materials: This was a cross sectional study of 110 adult patients undergoing surgery with a potential for blood loss of 500 ml and over under general anaesthesia. Haemoglobin level was determined simultaneously postinduction, pre-transfusion and postoperatively using (SpHb) readings from Masimo Pronto® Pulse CO-Oximeter (Rainbow® SET® Technology Masimo Corporation, Irvine, CA) and haemoglobin analyzer with laboratory spectrophotometry (tHb). Results: A total of 244 sample pairs were analysed; 110 postinduction, 24 pre-transfusion and 110 post-operatively. There was a significant difference in mean haemoglobin between SpHb and tHb during the study at all time periods, p<0.0001. The overall mean haemoglobin was SpHb 12.02 ±1.86 g/dl, and tHb10.49 ±1.92 g/dl, p<0.0001, bias (1.5 ±1.76 g/dl), and limits of agreement-1.9 to 5.0 g/dl. There was moderate Pearson correlation (0.57) between SpHb and tHb measurements. The mean pre-transfusion haemoglobin was SpHb 10.25 ±1.96 g/dl, and tHb 8.26 ±1.27 g/dl, p<0.0001, bias, 2.0 ±1.89 g/dl and limits of agreement, -1.7 to 5.7 g/dl. Conclusion: It is concluded that SpHb overestimated haemoglobin measurement as compared with tHb. Hence the Masimo Pronto was found to be inaccurate as compared with laboratory spectrophotometry in intraoperative haemoglobin measurement. The bias was too large and limits of agreement too wide between SpHb and tHb to make appropriate transfusion decisions. Keywords: Haemoglobin, invasive, non-invasive, transfusion, intraoperative