SpHb Measurements Research Articles

Is noninvasive hemoglobin measurement suitable for children undergoing preoperative anesthesia consultation?

Preoperative anemia in children is a significant clinical concern requiring precise diagnosis. Although traditional blood sample collection is effective, it poses challenges because of children's aversion and technical difficulties. Therefore, this study explores the suitability of noninvasive hemoglobin measurements in children during preoperative anesthesia consultation. Noninvasive hemoglobin measurement (SpHb®; Masimo) in children aged ≤ 17years was performed during preoperative anesthesia consultation and compared with laboratory hemoglobin (labHb) levels. SpHb was measured in 62 children (median age: 6years, standard deviation [SD] ± 5.3) without adverse effects but was unsuccessful in one child. The bias, limits of agreement, and root mean square error between SpHb and labHb were 0.3, -2.26-+2.8, and 1.3g/dl, respectively. LabHb demonstrated a significant regression relationship with R2 of 0.359. LabHb was associated with a negative effect on bias [- 0.443 (CI 95: - 0.591- - 0.153, P < 0.001)], i.e., SpHb tends to underestimate labHb for high labHb values. The retest reliability between two consecutive SpHb measurements was 0.727 (P < 0.001). Double measurement of SpHb, age, weight, sex, heart rate, and perfusion index had no significant effects on accuracy. Using SpHb, a specificity of 96.3% (95% confidence interval [CI 95]: 87.3%-99.5%) and a sensitivity of 57.1% (CI 95: 18.4%-90.1%) were observed. Based on adapted cut-off values for SpHb (age-dependent cut-off values plus 0.8g/dl), a sensitivity of 100% (CI 95: 64.6%-100%) was achieved for the investigated study collective. SpHb measurement in children is a quick procedure. The accuracy of hemoglobin measurement is insufficient for the diagnosis of anemia. Thus, whether the calculated cut-off SpHb values of this study collective can be considered for anemia screening in pediatric patients undergoing preoperative anesthesia consultation should be confirmed. Trial registration number and date of registration: This prospective study was registered at ClinicalTrials.gov (NCT03586141).

Comparing Non-Invasive Spectrophotometry to Hematology Analysis for Hemoglobin Measurements in Sickle Cell Disease Patients.

Patients with sickle cell disease (SCD) require repeated blood sampling for hemoglobin (Hb) concentration measurements. The primary aim of this study was to compare non-invasive spectrophotometric hemoglobin (SpHb, g/dL) measurements to those taken via an automated hematology analyzer (Hb, g/dL) in patients with SCD visiting outpatient clinics and to investigate the correlations and agreements between both measurement techniques. Secondarily, we aimed to identify the SpHb cut-off concentration for the diagnosis of anemia and to monitor the effects of the pleth variability index (PVI, %) and perfusion index (PI) on SpHb measurements. The results gained from the examination of one hundred and fifty-eight patients indicated that the SpHb measurements overestimated the lab Hb concentrations, with a mean (SpHb-Hb) bias of 0.82 g/dL (SD 1.29). The SpHb measurements were positively correlated with the Hb measurements (Kendall's tau correlation (τ), n = 158, τ = 0.68, p < 0.001), with an intra-class correlation (ICC) of 0.67 and a 95% CI from 0.57 to 0.74 (p = 0.000). The SpHb cut-off concentration to diagnose anemia was 11.4 and 11.7 g/dL for males and females, respectively. SpHb sensitivity was low for males and females at 64.4% and 57.1%; however, the specificity was higher at 90.9% and 75%, with positive predictive values (PPVs) of 95.6 and 85.7, respectively. No correlation existed between SpHb measurements and the PVI (%) in contrast with a moderate correlation with the PI (r = 0.049, p = 0.54, and r = 0.36, p < 0.001, respectively). The mean PI was low at 2.52 ± 1.7. In conclusion, the SpHb measurements were consistently higher than the lab Hb concentrations, with a positive correlation. The sensitivity and precision of the SpHb measurements were lower than expected. However, the SpHb specificity and its positive predictive values (PPVs) indicated that it is less likely for a patient with a positive SpHb test result for anemia to be non-anemic. These results will allow SpHb measurement to play a role in excluding the presence of anemia. In light of the low PI values determined, the SpHb measurements were challenging to take and, thus, require further technological improvements.

Non-invasive hemoglobin estimation for preoperative anemia screening.

Preoperative anemia is common and associated with adverse postoperative outcomes. Assessment of hemoglobin concentrations may facilitate optimization prior to surgery. However, phlebotomy-based hemoglobin measurement may contribute to patient discomfort and iatrogenic blood loss, which makes non-invasive hemoglobin estimation attractive in this setting. This is a prospective study of adult patients presenting for preoperative evaluation before elective surgery at a tertiary care medical center. The Masimo Pronto Pulse CO-Oximeter was utilized to estimate blood hemoglobin concentrations (SpHb), which were then compared with hemoglobin concentrations obtained via complete blood count. Receiver operating curves were used to identify SpHb values maximizing specificity for anemia detection while meeting a minimum sensitivity of 80%. A total of 122 patients were recruited with a median (interquartile range) age of 66 (58, 72) years. SpHb measurements were obtained in 112 patients (92%). SpHb generally overestimated hemoglobin with a mean (± 1.96 × standard deviation) difference of 0.8 (-2.2, 3.9) g/dL. Preoperative anemia, defined by hemoglobin <12.0g/dL in accordance with institutional protocol, was present in 22 patients (20%). The optimal SpHb cut-point to identify anemia was 13.5g/dL: sensitivity 86%, specificity 81%, negative predictive value 96%, and positive predictive value 53%. Utilizing this cut-point, 60% (73/122) of patients could have avoided phlebotomy-based hemoglobin assessment, while an anemia diagnosis would have been missed in <3% (3/122). The use of SpHb devices for anemia screening in surgical patients is feasible with the potential to reliably rule-out anemia despite limited accuracy.

Targeted Bleeding Management Guided by Non-Invasive Haemoglobin Measurement in Surgical Patients.

To assess blood transfusion decisions in blood losses using a continuous total haemoglobin (SpHb) and non-invasive haemoglobin (Hb) device. Double-blinded randomised controlled trial. Marmara University Hospital, Istanbul, Turkey, from March 2018 to December 2019. One hundred and twenty adult patients scheduled for elective major surgery and expected to experience a blood loss greater than 20% of their total blood volume were divided into two groups. These groups were compared for bleeding management with conventional blood gas sampling (Group Hb, the control group) according to Hb monitoring versus SpHb measurement (Group SpHb, the study group). In the postoperative measurement, there were fewer red blood cells (RBC) in the SpHb group than in the Hb group (p=0.020). There was a greater change in the amount of RBC from the perioperative to the postoperative period in the SpHb group compared to the Hb group (p<0.001). Postoperative Hb levels of patients in the intensive care unit (ICU) were higher in the SpHb group than in the Hb group (p<0.05). SpHb can provide effective patient blood management in cases of major surgery. It does not cause a delay in the decision of blood transfusion during surgery. Haemorrhage, Anaemia, Blood transfusion, General surgery.

Non-invasive Hemoglobin Measurement Predictive Analytics with Missing Data and Accuracy Improvement Using Gaussian Process and Functional Regression Model.

Recent use of noninvasive and continuous hemoglobin (SpHb) concentration monitor has emerged as an alternative to invasive laboratory-based hematological analysis. Unlike delayed laboratory based measures of hemoglobin (HgB), SpHb monitors can provide real-time information about the HgB levels. Real-time SpHb measurements will offer healthcare providers with warnings and early detections of abnormal health status, e.g., hemorrhagic shock, anemia, and thus support therapeutic decision-making, as well as help save lives. However, the finger-worn CO-Oximeter sensors used in SpHb monitors often get detached or have to be removed, which causes missing data in the continuous SpHb measurements. Missing data among SpHb measurements reduce the trust in the accuracy of the device, influence the effectiveness of hemorrhage interventions and future HgB predictions. A model with imputation and prediction method is investigated to deal with missing values and improve prediction accuracy. The Gaussian process and functional regression methods are proposed to impute missing SpHb data and make predictions on laboratory-based HgB measurements. Within the proposed method, multiple choices of sub-models are considered. The proposed method shows a significant improvement in accuracy based on a real-data study. Proposed method shows superior performance with the real data, within the proposed framework, different choices of sub-models are discussed and the usage recommendation is provided accordingly. The modeling framework can be extended to other application scenarios with missing values.

The effects of body weight and pneumoperitoneum on pleth variability index and total haemoglobin in patients undergoing laparoscopic cholecystectomy: A prospective observational study

It is not clear if there is an inaccurate effect of obesity and pneumoperitoneum on non-invasive monitoring parameters. The aim of this study is to determine the effects of CO2 pneumoperitoneum and desufflation on non-invasive monitoring variables between obese and non-obese patients undergoing laparoscopic surgery. Sixty patients were included in the study that underwent laparoscopic cholecystectomy between February 2019 and November 2019. After induction of anaesthesia, systolic and diastolic blood pressures, heart rate, duration of operation and pneumoperitoneum, pleth variability index (PVI) and total hemoglobin (SpHb) data were recorded. The patients were divided into two groups. There was no significant difference between the groups in terms of chronic diseases and duration of operation and pneumoperitoneum. No significant difference was found between the groups in PVI and SpHb values. In comparison of PVI measurement values with T0, a significant difference was found in T3, T4 and T5 in Group 2 (p = 0.010, 0.012 and 0.041, respectively). In comparison of SpHb measurement values with T0, a significant difference was found in T1, T2 and T3 in Group 2 (p = 0.008, 0.010 and 0.037, respectively). In comparison with T5, a significant difference was found in T1, T2 and T3 in Group 2 (p = 0.023, 0.005 and 0.006, respectively). In obese people, pneumoperitoneum can lead to errors in PVI and SpHb monitoring. Although these two parameters are very valuable in intraoperative follow-up, they should be used carefully during laparoscopic procedures in obese patients. If these parameters (PVI and SpHb) are considered to be used in bariatric surgeries, this information should be considered.

Continuous hemoglobin measurement during frontal advancement operations can improve patient outcomes.

Massive hemorrhage in pediatric cranioplasty operations may necessitate blood transfusion, which may cause many complications. Radical-7 Pulse CO-Oximeter (Massimo Corporation, Irvine, CA) can provide continuous hemoglobin concentration (SpHb) measurements noninvasively. In this study, we aimed to evaluate the effects of SpHb measurement on perioperative transfusion management and postoperative patient outcomes. For this retrospective case-control study, we collected the data of pediatric patients undergoing fronto-orbital advancement surgery for plagiocephaly and trigonocephaly between 2018 and 2021. Perioperative SpHb monitoring was performed for patients in the SpHb Group. Other patients that were managed conventionally were considered as the control group (C Group). The data on patients' demographic and clinical characteristics, intraoperative hemodynamic and laboratory variables such as blood gases, intraoperative blood losses, the amount of the transfused blood products, the length of postoperative intensive care unit (ICU) stay, and the duration of hospital stay were collected. The data of 42 patients were collected, and 29 of these patients were males (69%). In 16 of the patients, SpHb monitoring was performed. The demographic, clinical, and perioperative hemodynamic characteristics of the patients were comparable between the groups. Compared to the C Group, the SpHb Group had significantly lower perioperative packed red blood cell (PRBC) transfusion (136.3 ± 40.1 vs. 181.5 ± 74.8mL, P = 0.015), less postoperative drainage (125.3 ± 47.7 vs. 185.8 ± 97.6mL, P = 0.013), and shorter ICU stay (37.1 ± 12.0 vs. 64.8 ± 24.9h, P < 0.001). There was a positive correlation between the amount of PRBC transfusion and the length of ICU stay (r = 0.459, P = 0.003). Patients with perioperative continuous SpHb measurement have lower intraoperative PRBC transfusion, less postoperative bleeding, and shorter ICU stay. When necessary, SpHb, together with clinical judgment and laboratory confirmation, can be used in decision-making for perioperative PRBC transfusion.

Noninvasive Hemoglobin Measurement Reduce Invasive Procedures in Thalassemia Patients

This study was conducted to investigate the agreement between laboratory hemoglobin (LabHb) measured in venous blood and noninvasive, spectrophotometric hemoglobin (SpHb) measurement and the usability of SpHb measurement in the transfusion decision-making in patients with thalassemia whose hemoglobin (Hb) was monitored by taking blood samples at frequent intervals and who were transfused. Cardiac pulse, oxygen saturation, Pleth variability index (PVI), and SpHb values were measured in patients who came to the hematology outpatient clinic for a control visit and whose Hb levels were planned to be measured. Venous blood samples were taken for LabHb measurement, which we accept as the gold standard. Cohen’s kappa value was calculated for the agreement between SpHb measurements and LabHb values. The relationship and predictability between both measurement methods were evaluated by Pearson correlation analysis, a modified Bland-Altman plot and the linear regression model. In the study conducted with a total of 110 children with thalassemia, a moderate level of agreement between the two measurement methods (kappa = 0.370, p < 0.0001) and a significantly high correlation between the two tests (r = 0.675) were found. The mean bias between the differences was found to be 0.3 g/dL (–1.27 to 1.86 g/dL). The sensitivity and the specificity of SpHb in identifying patients who needed transfusions (Hb <10.0 g/dL) were calculated as 92.2 and 57.1%, respectively. Our results suggest SpHb measurement may be used to screen anemia in hemodynamically stable hemoglobinopathy patients and even for transfusion decision-making with combination clinical findings.

Improving non-invasive hemoglobin measurement accuracy using nonparametric models

Uncontrolled hemorrhage is a leading cause of preventable death among patients with trauma. Early recognition of hemorrhage can aid in the decision to administer blood transfusion and improve patient outcomes. To provide real-time measurement and continuous monitoring of hemoglobin concentration, the non-invasive and continuous hemoglobin (SpHb) measurement device has drawn extensive attention in clinical practice. However, the accuracy of such a device varies in different scenarios, so the use is not yet widely accepted. This article focuses on using statistical nonparametric models to improve the accuracy of SpHb measurement device by considering measurement bias among instantaneous measurements and individual evolution trends. In the proposed method, the robust locally estimated scatterplot smoothing (LOESS) method and the Kernel regression model are considered to address those issues. Overall performance of the proposed method was evaluated by cross-validation, which showed a substantial improvement in accuracy with an 11.3% reduction of standard deviation, 23.7% reduction of mean absolute error, and 28% reduction of mean absolute percentage error compared to the original measurements. The effects of patient demographics and initial medical condition were analyzed and deemed to not have a significant effect on accuracy. Because of its high accuracy, the proposed method is highly promising to be considered to support transfusion decision-making and continuous monitoring of hemoglobin concentration. The method also has promise for similar advancement of other diagnostic devices in healthcare.

Blood transfusion decisions cannot be based on percutaneous haemoglobin measurements.

Percutaneous measurement of haemoglobin (SpHb) has been an emerging technique in the past decades. It has been suggested that SpHb measurement could be used as atrend monitor and as asupportive tool for easier and faster transfusion decision-making. The aim of this study was to investigate whether SpHb monitoring is auseful instrument in transfusion decision-making. Patients scheduled for surgery with expected blood loss over 800 mL were included in the study. SpHb was measured using aMasimo Rainbow probe. Blood samples were drawn before and after surgery and, if clinically indicated, during surgery. Moreover, perfusion parameters were analysed, as well as transfusion triggers. Based on transfusion triggers 27.1% of patients would not have been transfused according to National Guidelines (14.5% transfused in error, 12.5% not transfused when indicated). Invasive haemoglobin (invasive Hb) and SpHb were obtained 266 times in 75 patients. The mean invasive Hb was 7.37 ± 1.34 mmol L-1 and SpHb was 6.47 ± 0.81 mmol L-1 (P < 0.001). Bland-Altman analysis corrected for multiple measurements revealed proportional bias of -4.05 + 0.72 Hb (least bias at Hb 5.62). The precision of the SpHb measurement exceeded the acceptable range of error. We concluded that SpHb measurement using the Rainbow device is too unreliable to be an acceptable alternative to invasive Hb measurement, or even as atrend monitor or decision support tool.

The Comparison of Hemoglobin Values Measured by Blood and Continuous Non-Invasive Monitoring (SpHb) in Newborn Infants.

Hemoglobin (Hb) measurement is one of the most commonly used laboratory tests in medical practice. Unnecessary blood sampling, especially in neonatal intensive care units (NICUs), contributes to iatrogenic anemia. Continuous non-invasive monitoring of total Hb (SpHb) was compared with invasive venous blood samples (tHb) in NICU patients. Three hundred and ten patients were identified in NICU. Non-invasive Hb measurement was performed immediately before venous blood sampling and comparison of invasive with non-invasive values was undertaken. There was a strongly positive correlation between SpHb and tHb (r = 0.965, p < 0.001). Bland-Altman analysis was performed in 95% limits of agreement for Hb values measured by both methods. The mean bias between tHb and SpHb measurements was 0.05 g/dl (-1.85 to 1.96). In Passing-Bablok regression analysis, the CUSUM test p value was found to be 0.98 for Hb levels measured by SpHb and tHb; and the difference between the methods was not significant. In newborns, SpHb method offers reliable Hb values, which are comparable with the more traditional tHb method. Continuous non-invasive monitoring of total Hb may help prevent unnecessary blood sampling and iatrogenic anemia. Further clinical studies are required for the effectiveness of the method in critically ill patients with circulatory disorders.

Clinical implications of using non-invasive haemoglobin monitoring for red blood cell transfusion decision in hip arthroplasty

IntroductionThe decision to transfuse red blood cells requires accurate haemoglobin concentration values. In this study, we evaluated if continuous non-invasive haemoglobin (SpHb) measurement could substitute laboratory determined haemoglobin (LabHb) in patients undergoing elective hip replacement. As secondary objective, we analyzed the trend of the difference between techniques. Materials/methodsLabHb measurements were done using an automated analyser and SpHb measurements were acquired using Radical-7®. In randomly selected patients undergoing hip replacement, whenever blood was collected for LabHb, concomitant SpHb was recorded. Correlation, bias and accuracy of SpHb were calculated in comparison with LabHb. Results108 paired measurements were obtained from 43 patients. The Pearson R of the correlation between SpHb and LabHb was 0.7 (p < 0.001). Bland-Altman test revealed a bias of 1 ± 1.4 g dL−1, meaning Lab Hb was recurrently higher than SpHb. Limits of agreement were [−1.7; 3.8]. Considering RBC transfusion threshold of 8 g dL−1, we found that in two situations transfusion decision would differ based on the measurement considered. Trending ability of SpHb study showed a significant difference between preoperative and postoperative LabHb-SpHb. DiscussionThere was a good correlation between SpHb and LabHb, while bias and limits of agreement were higher than those in literature. There was a limited trending ability of SpHb during the perioperative period. Despite this, using SpHb instead of LabHb for decision making regarding transfusion would only change the decision in 1.9 % of our cases. Our findings suggest that this device could be used as a reference but cannot replace venous puncture as gold standard.

Evaluation of noninvasive hemoglobin monitoring in children with congenital heart diseases.

Noninvasive measurement of blood hemoglobin could save time and decrease the risk of anemia and infection. The accuracy of CO-oximetry-derived noninvasive hemoglobin (Sp-Hb) had been evaluated in pediatric population; however, its accuracy in children with congenital heart disease has not been studied till date. We evaluated the accuracy of Sp-Hb in relation to laboratory-measured hemoglobin (Lab-Hb) in children with congenital heart disease. This prospective observational study included children with congenital heart disease undergoing procedural intervention. Sp-Hb measurements were obtained using Radical-7 Masimo pulse CO-oximeter and were compared against simultaneous Lab-Hb measurements obtained from the arterial line. Children were divided in cyanotic and acyanotic, and separate analysis was performed for each group. The values of both measurements were analyzed using Spearman's correlation coefficient and Bland-Altman analysis. Correlation was performed between Sp-Hb and Lab-Hb bias and each of arterial oxygen saturation and perfusion index. One-hundred and eleven pairs of readings were obtained from 65 children. The median (quartiles) age and weight of the children were 1 (1.2-4)years and 11 (8-17)kg, respectively. There was moderate correlation between Lab-Hb and Sp-Hb with a correlation coefficient (95% confidence interval [CI]) of 0.75 (0.63-0.83) in acyanotic children and 0.62 (0.37-0.79) in cyanotic children. The mean bias (95% limits of agreements) was -0.4g/dL (-2.4 to1.6g/dL) and 1g/dL (-2.7to4.6g/dL) in acyanotic and cyanotic children, respectively. The mean bias between Sp-Hb and Lab-Hb showed a weak negative correlation with oxygen saturation (r [95% CI]): (-0.36 [-0.51--0.18]), and a weak positive correlation with the perfusion index (r [95% CI]): (0.19 [0.01-0.37]). The large bias and the wide limits of agreement between Sp-Hb and Lab-Hb denote that Masimo-derived Sp-Hb is not accurate in children with congenital heart disease especially in the cyanotic group; the error in Sp-Hb increases when oxygen saturation decreases.

Evaluation of pulse co-oximetry to determine haemoglobin saturation with oxygen and haemoglobin concentration in anaesthetized horses: a retrospective study

ObjectiveThis study compared the values of variables measured by pulse co-oximetry (Masimo Radical 7; Masimo Europe Limited, UK) with those measured by a co-oximeter-enabled blood gas analyser (Siemens Rapid-point 500; Siemens Healthcare Limited, UK) in anaesthetized horses. Study designRetrospective study. AnimalsA total of 30 anaesthetized horses. MethodsIn total, 47 heparinized arterial blood samples were collected for blood gas analysis to determine haemoglobin concentration (tHb, g L–1) and percentage of haemoglobin saturation with oxygen (SaO2). Arterial haemoglobin saturation with oxygen was determined noninvasively by pulse co-oximetry (Masimo SpO2). Pulse co-oximetry also provided arterial haemoglobin concentration (SpHb) and arterial oxygen content (SpCaO2). Arterial oxygen content was calculated (CaO2) in 39 samples using SaO2 and the value of Hüfner’s constant used by Masimo Radical 7 (1.3 mL g–1). Data were compared using Bland–Altman analysis, correlation tests, accuracy root mean square (ARMS) statistics and total allowable error, where available. ResultsLow bias but wide limits of agreement (LoA) were found between Masimo SpO2 and SaO2 (bias = –1.4%, LoA = –4.0 to 1.3%), with an ARMS of 3%. Compared with tHb, SpHb showed low bias (6.2 g L–1) but wide LoA (–39.6 to 52.6 g L–1); its % bias (5.2%) was still within the 7% limits recommended by the Clinical Laboratory Improvement Amendments (CLIA) for humans. When comparing SpCaO2 and CaO2, the bias and LoA were –0.2 mL dL–1 and –6.7 to 6.2 mL dL–1, respectively. Conclusions and clinical relevanceMasimo SpO2 was acceptable for current ARMS standards, and SpHb measurements also met CLIA limits. The wide LoA in this study, however, suggest that the Masimo Radical 7 cannot be recommended as a substitute for direct measurements. As blood gas machines, pulse oximeters and co-oximeters use algorithms based on human haemoglobin, no true gold standard exists for horses.

Improving Accuracy of Noninvasive Hemoglobin Monitors: A Functional Regression Model for Streaming SpHb Data.

The purpose of this paper is to develop a method for improving the accuracy of SpHb monitors, which are noninvasive hemoglobin monitoring tools, leading to better critical care protocols in trauma care. The proposed method is based on fitting smooth spline functions to SpHb measurements collected over a time window and then using a functional regression model to predict the true HgB value for the end of the time window. The accuracy of the proposed method is compared to traditional methods. The mean absolute error between the raw SpHb measurements and the gold standard hemoglobin measurements was 1.26g/Dl. The proposed method reduced the mean absolute error to 1.08g/Dl. [1] Conclusion: Fitting a smooth function to SpHb measurements improves the accuracy of Hgb predictions. Accurate prediction of current and future HgB levels can lead to sophisticated decision models that determine the optimal timing and amount of blood product transfusions.

Non-Invasive Hemoglobin Monitoring: A Method of Measuring Blood Loss in Cesarean Delivery? [22R

INTRODUCTION: Obstetrical hemorrhage is a leading cause of maternal morbidity and mortality worldwide. Prompt and accurate estimation of blood loss (EBL) is necessary to expedite the diagnosis and treatment of postpartum hemorrhage. The aim of this study is to investigate the ability of the non-invasive hemoglobin measurement to measure blood loss during a cesarean delivery (CD). METHODS: Term, singleton patients undergoing scheduled CD were consented for this prospective, non-blinded, observational study. The Masimo Radical-7 Pulse CO-oximeter recorded non-invasive hemoglobin (SpHb) values at baseline, continuously during the CD, and for 8 hours postoperatively. Values were then compared with hemoglobin (Hb) measurements obtained preoperatively and on postoperative day 1. RESULTS: Data were obtained from 13 women. Mean maternal age was 32 (25-41) and mean gestational age was 38.9 (37.6-39.6). Indications were elective repeat (n=5), repeat for &gt; 1 prior (n=6), primary elective (n=2), and prior myomectomy (n=1). Average EBL was 938 (800-1500) and average decrease in Hb was 2.2 (0.6-3.0). EBL was not correlated to calculated blood loss (p=0.37). Average preoperative SpHb was 10.6 (9.2-12.2) and there was no difference in average postoperative SpHb measurements at 0, 1, 4, and 8 hours postoperatively (p-0.9). There was no correlation between SpHb values and blood loss. CONCLUSION: This study demonstrates the inability of non-invasive techniques to measure blood loss during CD. SpHb showed poor accuracy and no trending ability compared to laboratory values. These findings are supported by prior studies showing poor performance in conditions involving large changes in intravascular volume, especially during hemorrhage.

Impact of acute changes in perfusion index and blood pressure on the accuracy of non-invasive continuous hemoglobin concentration measurements during induction of anesthesia.

Several factors affect the accuracy of non-invasive continuous hemoglobin concentration (SpHb) measurements. We had previously shown an increase in the perfusion index (PI) following induction of anesthesia which was associated with an increase in the difference between SpHb and total hemoglobin (tHb) (SpHb-tHb). We hypothesized that blunting the increase in PI by maintaining blood pressure during induction of anesthesia would improve the agreement between SpHb and tHb measurements. Twenty-nine adult patients were enrolled. Patients were randomly assigned by use of sequentially numbered, opaque sealed envelopes to a control (group C) or a phenylephrine group (group P). Anesthesia was induced and maintained with propofol, remifentanil, and ketamine. In group P, phenylephrine was infused at 0.5µg/kg/min during induction of anesthesia. SpHb and PI were monitored with a Radical-7 Pulse CO-Oximeter. tHb and hematocrit were measured with the ABL800 blood gas analyzer. Following induction of anesthesia, PI increased significantly in both groups (p<0.001 and p<0.05 in groups C and P, respectively). However, the increase in PI was significantly smaller in group P than in group C (2.6±1.3 vs 0.8±1.4%, p<0.001). Similarly, the change in SpHb-tHb was significantly smaller in group P than in group C (0.40±0.78 vs 0.97±0.70g/dl, p<0.05). Changes in SpHb-tHb are correlated with changes in PI (r=0.46, p<0.05). The findings suggest that blunting the increase in PI by maintaining arterial pressure during induction of anesthesia improves the agreement between SpHb and tHb values.

Validation of Spectrophotometric Hemoglobin Measurement with a Pulse Co-Oximeter in Cases of Massive Hemorrhage

Purpose: The accuracy of spectrophotometric hemoglobin (SpHb) measurement with a pulse co-oximeter was analyzed in cases of intraoperative massive hemorrhage and compared with Hb levels determined through blood gas analysis (LabHb) as a reference. We aimed to determine the extent to which in vivo adjustment (ADJ) for results of initial blood gas analysis would improve the accuracy of SpHb measurement. Methods: Data on LabHb and SpHb levels were collected from cases with hemorrhage of 1000 g or more. Correlations and Bland-Altman analyses were used to determine the associations between data before and after ADJ. Results: ADJ slightly improved the correlation coefficient (Pearson r) between SpHb and LabHb levels from 0.65 to 0.72. In Bland-Altman analysis, ADJ reduced the bias from 1.76 ± 1.47 g/dL to 0.64 ± 1.43 g/dL, while the 95% limits of agreement of -1.12 to 4.64 g/dL (range: 5.77 g/dL) without ADJ improved to -2.16 to 3.44 g/dL (range: 5.59 g/dL) with ADJ. In four-quadrant analysis, other than samples in the exclusion zone, the total number analyzed was 326, and the concordance rate was 82%. Conclusion: Although the accuracy of SpHb measurement improves on ADJ, SpHb measurement cannot substitute for LabHb levels, and it is necessary to determine Hb levels with blood gas analysis in the laboratory. It remains unclear which measurement is superior for determining when to initiate blood transfusion to achieve better outcomes. To comply with conventional methods, LabHb measurements may be necessary.

Pressure-dependent changes in haematocrit and plasma volume during anaesthesia, a randomised clinical trial.

Induction of general anaesthesia has been shown to cause haemodilution and an increase in plasma volume. The aim of this study was to evaluate whether prevention of hypotension during anaesthesia induction could avoid haemodilution. Twenty-four cardiac surgery patients, 66 ± 10 years, were randomised to receive either norepinephrine in a dose needed to maintain mean arterial blood pressure (MAP) at pre-anaesthesia levels after induction or to a control group that received vasopressor if MAP decreased below 60 mmHg. No fluids were infused. Changes in plasma volume were calculated with standard formula: 100 × (Hct(pre)/Hct(post) - 1)/(1 - Hct(pre)). Arterial blood gas was analysed every 10 minutes and non-invasive continuous haemoglobin (SpHb) was continuously measured. Pre-anaesthesia MAP was 98 ± 7 mmHg. Ten minutes after anaesthesia induction, the haematocrit decreased by 5.0 ± 2.5% in the control group compared with 1.2 ± 1.4% in the intervention group, which corresponds to increases in plasma volume by 310 ml and 85 ml respectively. MAP decreased to 69 ± 15 mmHg compared to 92 ± 10 mmHg in the intervention group. The difference maintained throughout the 70 min intervention period. The change in haemoglobin level measured by blood gas analysis could not be detected by SpHb measurement. The mean bias between the SpHb and blood gas haemoglobin was 15 g/l. During anaesthesia induction, haematocrit decreases and plasma volume increases early and parallel to a decrease in blood pressure. This autotransfusion is blunted when blood pressure is maintained at pre-induction levels with norepinephrine.

The Accuracy and Reliability of Non-Invasive Haemoglobin Measurements in the Emergency Room: a Small Prospective Observational Quality Control Study from a Swiss University Hospital ED

Background: The accuracy and reliability of non-invasive oximetry for haemoglobin measurements were reported in operating rooms and intensive care units, though few studies evaluated this technology in emergency departments. The purpose of this study was to evaluate the accuracy and reliability of non-invasive SpHb readings from a portable device, in emergency department patients, compared to synchronous LabHb measurements. The authors sought to minimise external variables that could influence device performance, including learning curves and patient conditions, thus performed measurements by one trained user on stable adults only. Methods: The authors enrolled 24 consecutive adults admitted to the emergency department suspected or manifest active bleeding, and excluded cases of incarceration, pregnancy and burns. Haemoglobin concentrations were synchronously measured by phlebotomy laboratory analysis (LabHb) and using non-invasive readings (SpHb) from a portable Pronto-7 Pulse CO-Oximeter. Results: The non-invasive SpHb concentrations were recorded in 24 patients (100%), but the device it aborted during one or more measurement in 8 patients (33.3%) due to tremor and shivering. Paired comparison of SpHb and LabHb revealed a mean absolute error of 1.2 ± 1.3 g/dL (median 0.7, range 0.1 to 0.5), which equates to relative error of 9% ± 14% (median 5%, range 1% to 59%). Conclusions: Non-invasive SpHb measurements deviate from the ‘gold standard’ LabHb by an average of 1.2 g/dL (10%), but that outliers could be up to 5.2 g/dL (59%), which could lead to conflicting clinical decisions. Furthermore, the device functioned correctly in only 16 of 24 patients (66.6%), which should be reviewed in the light of difficult emergency department settings.