Comparison of the accuracy of noninvasive hemoglobin monitoring for preoperative evaluation between adult and pediatric patients: a retrospective study

We measured noninvasive hemoglobin (SpHb) levels during the pre-anesthesia visit in patients planning elective surgery. Differences between SpHb and laboratory-measured hemoglobin (Hblab) were compared between adult and pediatric patients. In the pre-anesthesia visiting office, we routinely monitor noninvasive Hb levels with oxygen saturation and heart rate using Masimo Radical-7® Pulse CO-Oximetry (Masimo Corp., Irvine, CA, USA). We attached the R1 20 (body weight, 10–50 kg) or R1 25 (body weight > 30 kg) probe on the index finger. After signal stabilization, SpHb and perfusion index (PI) were recorded. We retrospectively reviewed the recorded data and included patients who visited the anesthesiologist within 24 h after venous sampling. Bias was calculated by subtracting Hblab from SpHb. We compared the biases of adult and pediatric patients (< 18 years) and evaluated correlation coefficients between the bias and Hblab. Records of 105 patients were reviewed and 100 data points of 50 patients in each group were analyzed. The median ± interquartile range bias was − 2.6 ± 2.2 and − 1.2 ± 1.5 g/dL in adult and pediatric patients, respectively (P < 0.001); the corresponding mean ± standard deviation PIs were 4.4 ± 3.1 and 5.9 ± 2.7, respectively (P = 0.19). Bias was inversely proportional to Hblab irrespective of age. The correlation coefficient between the bias and Hblab was − 0.81 in adults and − 0.54 in pediatric patients (P < 0.001). SpHb and Hblab measured during pre-anesthesia visits showed a smaller difference in pediatric than in adult patients. Lower Hblab corresponded to higher accuracy.