Precision of noninvasive hemoglobin-level measurement by pulse co-oximetry in patients admitted to intensive care units for severe gastrointestinal bleeds*:

Feasibility and accuracy of noninvasive continuous hemoglobin monitoring using transesophageal photoplethysmography in porcine model

BACKGROUND

Continuous and noninvasive hemoglobin (Hb) monitoring during surgery is essential for anesthesiologists to make transfusions decisions. The aim of this study was to investigate the feasibility and accuracy of noninvasive and continuous Hb monitoring using transesophageal descending aortic photoplethysmography (dPPG) in porcine model.

METHODS

Nineteen landrace pigs, aged 3 to 5 months and weighing 30 to 50 kg, were enrolled in this study. A homemade oximetry sensor, including red (660 nm) and infrared (940 nm) lights, was placed in the esophagus for dPPG signal detection to pair with the corresponding reference Hb values (Hbi-STAT) measured by blood gas analysis. The decrease and increase changes in Hb concentration were achieved by hemodilution and transfusion. Metrics, including alternating current (AC), direct current (DC), and AC/DC for both red and infrared light were extracted from the dPPG signal. A receiver operating characteristic (ROC) curve was built to evaluate the performance of dPPG metrics in predicting the Hb "trigger threshold" of transfusion (Hb < 60 g/L and Hb > 100 g/L). Agreement and trending ability between Hb measured by dPPG (HbdPPG) and by blood gas analysis were analyzed by Bland-Altman method and polar plot graph. Error grid analysis was also performed to evaluate clinical significance of HbdPPG measurement.

RESULTS

The dPPG signal was successfully detected in all of the enrolled experimental pigs, without the occurrence of a continuous loss of dPPG signal for 2 min during the entire measurement. A total of 376 pairs of dPPG signal and Hbi-STAT were acquired. ACred/DCred and ACinf/DCinf had moderate correlations with Hbi-STAT, and the correlation coefficients were 0.790 and 0.782, respectively. The areas under the ROC curve for ACred/DCred and ACinf/DCinf in predicting Hbi-STAT < 60 g/L were 0.85 and 0.75, in predicting Hbi-STAT > 100 g/L were 0.90 and 0.83, respectively. Bland-Altman analysis and polar plot showed a small bias (1.69 g/L) but a wide limit of agreement (-26.02-29.40 g/L) and a poor trend ability between HbdPPG and Hbi-STAT. Clinical significance analysis showed that 82% of the data lay within the Zone A, 18% within the Zone B, and 0% within the Zone C.

CONCLUSION

It is feasible to establish a noninvasive and continuous Hb monitoring by transesophageal dPPG signal. The ACred/DCred extracted from the dPPG signal could provide a sensitive prediction of the Hb threshold for transfusion. The Hb concentration measured by dPPG signal has a moderate correlation with that measured by blood gas analysis. This animal study may provide an experimental basis for the development of bedside HbdPPG monitoring in the future.

Current Status of Measurement Accuracy for Total Hemoglobin Concentration in the Clinical Context

OBJECTIVE

The main objective of this investigation is to provide data about the accuracy of total hemoglobin concentration measurements with respect to clinical settings, and to devices within the categories of point-of-care and reference systems. In particular, tolerance of hemoglobin concentrations below 9 g/dL that have become common in clinical practice today determines the need to demonstrate the limits of measurement accuracy in patient care.

METHODS

Samples extracted from six units of heparinized human blood with total hemoglobin concentrations ranging from 3 to 18 g/dL were assigned to the test devices in a random order. The pool of test devices comprised blood gas analyzers, an automatic hematology analyzer, a laboratory reference method, and the point-of-care system HemoCue. To reduce the pre-analytic error, each sample was measured three times. Due to the characteristics of the tested devices and methods, we selected the mean values of the data from all these devices, measured at the corresponding total hemoglobin concentrations, as the reference.

MAIN RESULTS

The measurement results of the test devices overlap within strict limits (R2 = 0.999). Only the detailed analysis provides information about minor but systematic deviations. In the group of clinically relevant devices, which are involved in patient blood management decisions, the relative differences were within the limit of +/- 5 % for values down to 3 g/dL.

CONCLUSIONS

A clinically relevant change of +/- 0.5 g/dL of total hemoglobin concentration can be detected with all selected devices and methods. Compliance with more stringent definitions-these are the relative differences of 5 % in relation to the corresponding reference values and the clinically adapted thresholds in the format of a tolerance level analysis-was achieved by the clinical devices assessed here.

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 ± 74.8 mL, P = 0.015), less postoperative drainage (125.3 ± 47.7 vs. 185.8 ± 97.6 mL, P = 0.013), and shorter ICU stay (37.1 ± 12.0 vs. 64.8 ± 24.9 h, 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.

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

INTRODUCTION

The 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/METHODS

LabHb 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.

RESULTS

108 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.

DISCUSSION

There 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.

Invasive and non-invasive point-of-care testing and point-of-care monitoring of the hemoglobin concentration in human blood – how accurate are the data?

In this review, scientific investigations of point-of-care testing (POCT) and point-of-care monitoring (POCM) devices are summarized with regard to the measurement accuracy of the hemoglobin concentration. As a common basis, information according to the Bland and Altman principle [bias, limits of agreement (LOA)] as well as the measurement accuracy and precision are considered, so that the comparability can be mapped. These collected data are subdivided according to the manufacturers, devices and procedures (invasive and non-invasive). A total of 31 devices were identified. A comparability of the scientific investigations in particular was given for 23 devices (18 invasive and five non-invasive measuring devices). In terms of measurement accuracy, there is a clear leap between invasive and non-invasive procedures, while no discernible improvement can be derived in the considered time frame from 2010 to 2018. According to the intended use, strict specifications result from the clinical standards, which are insufficiently met by the systems. More stringent requirements can be derived both in the area of blood donation and in the treatment of patients.

Comparison of invasive and noninvasive blood hemoglobin measurement in the operating room: a systematic review and meta-analysis

Noninvasive hemoglobin (Hb)-monitoring devices are new inventions in pulse oximeter systems that show hemoglobin levels continuously. The aim of this systematic review and meta-analysis was to evaluate the accuracy and precision of noninvasive versus standard central laboratory Hb measurements in the operating room. We systematically searched multiple databases. Then, for the quality assessment of studies, we modified QUADAS-2 in the Revman 5.3 software. The GRADE approach was used to measure the quality of evidence (Grading of Recommendations Assessment, Development, and Evaluation). Data were analyzed using the meta-analysis method (random effect model) using STATA 11 software. A total of 28 studies on 2000 participants were included in the meta-analysis. Meta-analysis results of mean differences between noninvasive and the central laboratory Hb measurements in overall pooled random effects were - 0.27 (95% LoA (0.44, - 0.10); P value < 0.05). According to this meta-analysis, noninvasive hemoglobin measurement has acceptable accuracy in comparison with the standard invasive method.

Evaluation of Noninvasive Hemoglobin Monitoring in Surgical Critical Care Patients

OBJECTIVE

To assess the clinical utility of noninvasive hemoglobin monitoring based on pulse cooximetry in the ICU setting.

DESIGN AND SETTING

A total of 358 surgical patients from a large urban, academic hospital had the noninvasive hemoglobin monitoring pulse cooximeter placed at admission to the ICU. Core and stat laboratory hemoglobin measurements were taken at the discretion of the clinicians, who were blinded to noninvasive hemoglobin monitoring values.

MEASUREMENT AND MAIN RESULTS

There was a poor correlation between the 2,465 time-matched noninvasive hemoglobin monitoring and laboratory hemoglobin measurements (r = 0.29). Bland-Altman analysis showed a positive bias of 1.0 g/dL and limits of agreement of -2.5 to 4.6 g/dL. Accuracy was best at laboratory values of 10.5-14.5 g/dL and least at laboratory values of 6.5-8 g/dL. At hemoglobin values that would ordinarily identify a patient as requiring a transfusion (< 8 g/dL), noninvasive hemoglobin monitoring consistently overestimated the patient's true hemoglobin. When sequential laboratory values declined below 8 g/dL (n = 102) and 7 g/dL (n = 13), the sensitivity and specificity of noninvasive hemoglobin monitoring at identifying these events were 27% and 7%, respectively. At a threshold of 8 g/dL, continuous noninvasive hemoglobin monitoring values reached the threshold before the labs in 45 of 102 instances (44%) and at 7 g/dL, noninvasive hemoglobin monitoring did so in three of 13 instances (23%). Noninvasive hemoglobin monitoring minus laboratory hemoglobin differences showed an intraclass correlation coefficient of 0.47 within individual patients. Longer length of stay and higher All Patient Refined Diagnostic-Related Groups severity of illness were associated with poor noninvasive hemoglobin monitoring accuracy.

CONCLUSIONS

Although noninvasive hemoglobin monitoring technology holds promise, it is not yet an acceptable substitute for laboratory hemoglobin measurements. Noninvasive hemoglobin monitoring performs most poorly in the lower hemoglobin ranges that include commonly used transfusion trigger thresholds and is not consistent within individual patients. Further refinement of the signal acquisition and analysis algorithms and clinical reevaluation are needed.

Trending, Accuracy, and Precision of Noninvasive Hemoglobin Monitoring During Human Hemorrhage and Fixed Crystalloid Bolus

Automated critical care systems for en route care will rely heavily on noninvasive continuous monitoring. It has been reported that noninvasive assessment of blood hemoglobin via CO-oximetry (SpHb) assessed by spot measurements lacks sufficient accuracy for clinical decision making in trauma patients. However, the precision and utility of trending of continuous hemoglobin have not been evaluated in hemorrhaging humans. This study measured the trending and concordance of SpHb changes during dynamic variations resulting from controlled hemorrhage with concomitant fluid infusion. With institutional review board approval and informed consent, 12 healthy volunteers under general anesthesia were subjected to hemorrhage (10 mL/kg for 15 min) accompanied by Ringer's lactate solution infusion (30 mL/kg for 20 min). The SpHb was measured continuously by the Masimo Radical-7, whereas total blood hemoglobin was measured by arterial blood sampling. Trend analysis, assessed by plots of SpHb against time of 12 subjects, shows consistent falls in SpHb during hemodilution without exception. Four-quadrant concordance analysis was 95.4% with an exclusion zone of 1 g/dL. Spot comparisons of 106 data pairs (SpHb and total blood hemoglobin) showed that 50% exhibited an error of more than 1 g/dL with bias of 1.08 ± 0.82 g/dL and 95% limits of agreement of -0.5 to 2.6. Both trend analysis and concordance analysis suggest high precision of pulse CO-oximetry during hemodilution by hemorrhage and fluid bolus in human volunteers. However, accuracy was similar to other studies and therefore the use of pulse CO-oximetry alone is likely insufficient to make transfusion decisions.

Trends of Hemoglobin Oximetry: Do They Help Predict Blood Transfusion During Trauma Patient Resuscitation?

BACKGROUND

A noninvasive decision support tool for emergency transfusion would benefit triage and resuscitation. We tested whether 15 minutes of continuous pulse oximetry-derived hemoglobin measurements (SpHb) predict emergency blood transfusion better than conventional oximetry, vital signs, and invasive point-of-admission (POA) laboratory testing. We hypothesized that the trends in noninvasive SpHb features monitored for 15 minutes predict emergency transfusion better than pulse oximetry, shock index (SI = heart rate/systolic blood pressure), or routine POA laboratory measures.

METHODS

We enrolled direct trauma patient admissions ≥18 years with prehospital SI ≥0.62, collected vital signs (continuous SpHb and conventional pulse oximetry, heart rate, and blood pressure) for 15 minutes after admission, and recorded transfusion (packed red blood cells [pRBCs]) within 1 to 3, 1 to 6, and 1 to 12 hours of admission. One blood sample was drawn during the first 15 minutes. The laboratory Hb was compared with its corresponding SpHb reading for numerical, clinical, and prediction difference. Ten prediction models for transfusion, including combinations of prehospital vital signs, SpHb, conventional oximetry, and routine POA, were selected by stepwise logistic regression. Predictions were compared via area under the receiver operating characteristic curve by the DeLong method.

RESULTS

A total of 677 trauma patients were enrolled in the study. The prediction performance of the models, including POA laboratory values and SI (and the need for blood pressure), was better than those without POA values or SI. In predicting pRBC 1- to 3-hour transfusion, adding SpHb features (receiver operating characteristic curve [ROC] = 0.65; 95% confidence interval [CI], 0.53-0.77) does not improve ROC from the base model (ROC = 0.64; 95% CI, 0.52-0.76) with P = 0.48. Adding POA laboratory Hb features (ROC = 0.72; 95% CI, 0.60-0.84) also does not improve prediction performance (P = 0.18). Other POA laboratory testing predicted emergency blood use with ROC of 0.88 (95% CI, 0.81-0.96), significantly better than the use of SpHb (P = 0.00084) and laboratory Hb (P = 0.0068).

CONCLUSIONS

SpHb added no benefit over conventional oximetry to predict urgent pRBC transfusion for trauma patients. Both models containing POA laboratory test features performed better at predicting pRBC use than prehospital SI, the current best noninvasive vital signs transfusion predictor.

Continuous noninvasive hemoglobin monitoring: ready for prime time?

PURPOSE OF REVIEW

Determination of hemoglobin (Hb) concentration is essential for the detection of anemia and hemorrhage and is widely used to evaluate a patient for a possible blood transfusion. Although commonly accepted as intrinsic to the process, traditional laboratory measurements of Hb are invasive, intermittent, and time-consuming. Noninvasive Hb (NIHb)-monitoring devices have recently become available and promise the potential for detecting sudden changes in a patient's Hb level. In addition to reduced delays in clinical intervention, these devices also allow for a reduction in patient discomfort, infection risk, required personnel, and long-term costs. Unfortunately, it has been shown that many clinical factors can influence their accuracy.

RECENT FINDINGS

Many studies have been published on the accuracy and precision of NIHb-monitoring devices in various clinical settings. A recent meta-analysis has shown a small mean difference but wide limits of agreement between NIHb and laboratory measurements, indicating that caution should be used by physicians when making clinical decisions based on this device.

SUMMARY

NIHb measurements may currently be considered to be a supplemental tool for monitoring trends in Hb concentration, but are not currently developed enough to replace an invasive approach. Moreover, further studies are still required before implementing NIHb in the clinical decision-making process. Specifically, no studies have demonstrated that this technology improves clinical outcomes or patient safety.

Comparison of the gold standard of hemoglobin measurement with the clinical standard (BGA) and noninvasive hemoglobin measurement (SpHb) in small children: a prospective diagnostic observational study

INTRODUCTION

Collecting a blood sample is usually necessary to measure hemoglobin levels in children. Especially in small children, noninvasively measuring the hemoglobin level could be extraordinarily helpful, but its precision and accuracy in the clinical environment remain unclear. In this study, noninvasive hemoglobin measurement and blood gas analysis were compared to hemoglobin measurement in a clinical laboratory.

METHODS

In 60 healthy preoperative children (0.2-7.6 years old), hemoglobin was measured using a noninvasive method (SpHb; Radical-7 Pulse Co-Oximeter), a blood gas analyzer (clinical standard, BGAHb; ABL 800 Flex), and a laboratory hematology analyzer (reference method, labHb; Siemens Advia). Agreement between the results was assessed by Bland-Altman analysis and by determining the percentage of outliers.

RESULTS

Sixty SpHb measurements, 60 labHb measurements, and 59 BGAHb measurements were evaluated. In 38% of the children, the location of the SpHb sensor had to be changed more than twice for the signal quality to be sufficient. The bias/limits of agreement between SpHb and labHb were -0.65/-3.4 to 2.1 g·dl(-1) . Forty-four percent of the SpHb values differed from the reference value by more than 1 g·dl(-1) . Age, difficulty of measurement, and the perfusion index (PI) had no influence on the accuracy of SpHb. The bias/limits of agreement between BGAHb and labHb were 1.14/-1.6 to 3.9 g·dl(-1) . Furthermore, 66% of the BGAHb values differed from the reference values by more than 1 g·dl(-1) . The absolute mean difference between SpHb and labHb (1.1 g·dl(-1) ) was smaller than the absolute mean difference between BGAHb and labHb (1.5 g·dl(-1) /P = 0.024).

CONCLUSION

Noninvasive measurement of hemoglobin agrees more with the reference method than the measurement of hemoglobin using a blood gas analyzer. However, both methods can show clinically relevant differences from the reference method (ClinicalTrials.gov: NCT01693016).

The changes of non-invasive hemoglobin and perfusion index of Pulse CO-Oximetry during induction of general anesthesia

BACKGROUND

We hypothesized that induction of general anesthesia using sevoflurane improves the accuracy of non-invasive hemoglobin (SpHb) measurement of Masimo Radical-7® Pulse CO-Oximetry by inducing peripheral vasodilation and increasing the perfusion index (PI). The aim of this study is to investigate the change in the SpHb and the PI measured by Rad7 during induction of general anesthesia using sevoflurane.

METHODS

The laboratory hemoglobin (Hblab) was measured before surgery by venous blood sampling. The SpHb and the PI was measured twice; before and after the induction of general anesthesia using sevoflurane. The changes of SpHb, Hbbias (Hbbias = SpHb - Hblab), and PI before and after the induction of general anesthesia were analyzed using a paired t-test. Also, a Pearson correlation coefficient analysis was used to analyze the correlation between the Hbbias and the PI.

RESULTS

The SpHb and the PI were increased after the induction of general anesthesia using sevoflurane. There was a statistically significant change in the Hbbias from -2.8 to -0.7 after the induction of general anesthesia. However, the limit of agreement (2 SD) of the Hbbias did not change after the induction of general anesthesia. The Pearson correlation coefficient between the Hbbias and the PI was not statistically significant.

CONCLUSIONS

During induction of general anesthesia using sevoflurane, the accuracy of SpHb measurement was improved and precision was not changed. The correlation between Hbbias and PI was not significant.

Systematic Review and Meta-Analysis of Method Comparison Studies of Masimo Pulse Co-Oximeters (Radical-7™ or Pronto-7™) and HemoCue® Absorption Spectrometers (B-Hemoglobin or 201+) with Laboratory Haemoglobin Estimation

We assessed agreement in haemoglobin measurement between Masimo pulse co-oximeters (Rad-7™ and Pronto-7™) and HemoCue® photometers (201+ or B-Hemoglobin) with laboratory-based determination and identified 39 relevant studies (2915 patients in Masimo group and 3084 patients in HemoCue group). In the Masimo group, the overall mean difference was -0.03 g/dl (95% prediction interval -0.30 to 0.23) and 95% limits of agreement -3.0 to 2.9 g/dl compared to 0.08 g/dl (95% prediction interval -0.04 to 0.20) and 95% limits of agreement -1.3 to 1.4 g/dl in the HemoCue group. Only B-Hemoglobin exhibited bias (0.53, 95% prediction interval 0.27 to 0.78). The overall standard deviation of difference was larger (1.42 g/dl versus 0.64 g/dl) for Masimo pulse co-oximeters compared to HemoCue photometers. Masimo devices and HemoCue 201+ both provide an unbiased, pooled estimate of laboratory haemoglobin. However, Masimo devices have lower precision and wider 95% limits of agreement than HemoCue devices. Clinicians should carefully consider these limits of agreement before basing transfusion or other clinical decisions on these point-of-care measurements alone.

Continuous and noninvasive hemoglobin monitoring reduces red blood cell transfusion during neurosurgery: a prospective cohort study

Continuous, noninvasive hemoglobin (SpHb) monitoring provides clinicians with the trending of changes in hemoglobin, which has the potential to alter red blood cell transfusion decision making. The objective of this study was to evaluate the impact of SpHb monitoring on blood transfusions in high blood loss surgery. In this prospective cohort study, eligible patients scheduled for neurosurgery were enrolled into either a Control Group or an intervention group (SpHb Group). The Control Group received intraoperative hemoglobin monitoring by intermittent blood sampling when there was an estimated 15% blood loss. If the laboratory value indicated a hemoglobin level of ≤10 g/dL, a red blood cell transfusion was started and continued until the estimated blood loss was replaced and a laboratory hemoglobin value was >l0 g/dL. In the SpHb Group patients were monitored with a Radical-7 Pulse CO-Oximeter for continuous noninvasive hemoglobin values. Transfusion was started when the SpHb value fell to ≤l0 g/dL and was continued until the SpHb was ≥l0 g/dL. Blood samples were taken pre and post transfusion. Percent of patients transfused, average amount of blood transfused in those who received transfusions and the delay time from the hemoglobin reading of <10 g/dL to the start of transfusion (transfusion delay) were compared between groups. The trending ability of SpHb, and the bias and precision of SpHb compared to the laboratory hemoglobin were calculated. Compared to the Control Group, the SpHb Group had fewer units of blood transfused (1.0 vs 1.9 units for all patients; p ≤ 0.001, and 2.3 vs 3.9 units in patients receiving transfusions; p ≤ 0.0 l), fewer patients receiving >3 units (32 vs 73%; p ≤ 0.01) and a shorter time to transfusion after the need was established (9.2 ± 1.7 vs 50.2 ± 7.9 min; p ≤ 0.00 l). The absolute accuracy of SpHb was 0.0 ± 0.8 g/dL and trend accuracy yielded a coefficient of determination of 0.93. Adding SpHb monitoring to standard of care blood management resulted in decreased blood utilization in high blood loss neurosurgery, while facilitating earlier transfusions.

Does a non-invasive hemoglobin monitor correlate with a venous blood sample in the acutely ill?

Non-invasive hemoglobin measuring technology has potential for rapid, portable, and accurate way of providing identification of blood loss or anemia. Our objective is to determine if this technology is reliable in critically ill patients presenting to the Emergency Department. Prospective cross-sectional observational study was done at an urban level-one trauma center, 135 subjects were conveniently sampled, suspected of having active bleeding, sepsis, or other critically ill condition. Non-invasive measurements with Masimo (Irvine, CA, USA) Radical-7 and Rad-57 hemoglobin monitors were compared with the Beckman-Coulter LH-550 (Brea, CA, USA) clinical laboratory blood cell analyzer. The primary outcome was the relationship of the non-invasive device to the clinical laboratory results. Secondary evaluations included the effect of pulse rate, systolic BP, respiratory rate, temperature, capillary refill, skin color, nail condition, extremity movement. The Radical-7 was able to capture reading in 78% (88/113) of subjects, and the Rad-57 in 65% (71/110) of subjects. The correlation (R(2)) of the device Hb was 0.69 and 0.67 (p < 00.01) for the Radical-7 and Rad-57, respectively. The coefficient of variation for the Radical-7 was 18%, and for the Rad57 it was 13%. Univariate analysis shows none of the observed factors is associated with the difference values between the device Hb and laboratory Hb. Our results show that Radical-7 and Rad-57 devices do not report readings in 29% of patients and accuracy is significantly lower than reported by the manufacturer with over 50% of readings falling outside of ± 1 g/dL. We determined that none of the several potential factors examined are associated with the degree of device accuracy.

[Anesthetic management of severe or worsening postpartum hemorrhage]

INTRODUCTION

Risk factors of maternal morbidity and mortality during postpartum hemorrhage (PPH) include non-optimal anesthetic management. As the anesthetic management of the initial phase is addressed elsewhere, the current chapter is dedicated to the management of severe PPH.

METHODS

A literature search was performed using PubMed and Medline databases, and the Cochrane Library, for articles published from 2003 up to and including 2013. Several keywords related to anesthetic and critical care practice, and obstetrical management were used, in various combinations. Guidelines from several societies and organisations were also read.

RESULTS

When PPH worsens, one should ask for additional team personnel (professional consensus). Patients should be monitored for heart rate, blood pressure, skin and mucosal pallor, bleeding at skin puncture sites, diuresis and the volume of genital bleeding (grade B). Because of the possible rapid worsening of coagulapathy, patients should undergo regular evaluation of coagulation status (professional consensus). Prevention and management of hypothermia should be considered (professional consensus), by warming intravenous fluids and blood products, and by active body warming (grade C). Antibiotics should be given, if not already administered at the initial phase (professional consensus). Vascular fluids must be given (grade B), the choice being left at the physician discretion. Blood products transfusion should be decided based on the clinical severity of PPH (professional consensus). Priority is given to red blood cells (RBC) transfusion, with the aim to maintain Hb concentration>8g/dL. The first round of products could include 3 units of RBC (professional consensus), and the following round 3 units of RBC, and 3 units of fresh frozen plasma (FFP). The FFP:RBC ratio should be kept between 1:2 and 1:1 (professional consensus). Depending on the etiology of PPH, the early administration of FFP is left at the discretion of the physician (professional consensus). Platelet count should be maintained at>50 G/L (professional consensus). During massive PPH, fibrinogen concentration should be maintained at>2g/L (professional consensus). Fibrinogen can be given without prior fibrinogen measurement in case of massive bleeding (professional consensus). General anesthesia should be considered in case of hemodynamic instability, even when an epidural catheter is in place (professional consensus).

CONCLUSION

The anesthetic management aims to restore and maintain optimal respiratory state and circulation, to treat coagulation disorders, and to allow invasive obstetrical and radiologic procedures. Clinical and instrumental monitoring are needed to evaluate the severity of PPH, to guide the choice of therapeutic options, and to assess treatments efficacy.

Utility of noninvasive transcutaneous measurement of postoperative hemoglobin in total joint arthroplasty patients

This study prospectively evaluated the clinical utility of a noninvasive transcutaneous device for postoperative hemoglobin measurement in 100 total hip and knee arthroplasty patients. A protocol to measure hemoglobin noninvasively, prior to venipuncture, successfully avoided venipuncture in 73% of patients. In the remaining 27 patients, there were a total of 48 venipunctures performed during the postoperative hospitalization period due to reasons including transcutaneous hemoglobin measurement less than or equal to 9 g/dL (19), inability to obtain a transcutaneous hemoglobin measurement (8), clinical signs of anemia (3), and noncompliance with the study protocol (18). Such screening protocols may provide a convenient and cost-effective alternative to routine venipuncture for identifying patients at risk for blood transfusion after elective joint arthroplasty.

[Evaluation of non-invasive hemoglobin measurements using the Masimo Rainbow Radical-7® device in a patient with extracorporeal membrane oxygenation]

Circulatory assist devices such as extracorporeal membrane oxygenation are indicated in cases of cardiogenic shock refractory to optimal conventional treatment. Bleeding is a serious complication of such systems, mainly due to coagulation disorders caused by continuous administration of heparin, as well as platelet dysfunction. Serial coagulation and hemoglobin (Hb) measurements are essential. Hb measurements can be performed through repeated arterial blood gasometry, and more recently with a new spectrophotometric sensor, Masimo Rainbow Radical-7® device, which gives Hb values continuously and non-invasively. We report a case of a patient undergoing cardiac surgery who required extracorporeal membrane oxygenation for severe cardiogenic shock immediately after surgery. We compare the correlation and the level of agreement with Hb levels measured by 2 existing systems in clinical practice. Our results indicate that the Masimo® spectrophotometric monitor showed statistically comparable Hb values, in the correlation (r=.85; P<.01) and in agreement with those obtained by serial blood gas analyzer, ABL800 FLEX® (wavelength). In view of these results we consider the Masimo® device as a valid alternative for the continuous follow-up of the Hb and control of bleeding in these patients.

Savoring every drop - vampire or mosquito?

Blood safety with respect to infectious complications has reached very high standards. Nevertheless, reports on transfusion-associated morbidity and mortality gain momentum. Multidisciplinary patient blood management programs can minimize unnecessary exposure to allogeneic blood products by strengthening and conserving patients' own resources. This article outlines concepts designed to maintain hemoglobin concentration, to optimize hemostasis, and to minimize blood loss in ICUs. These measures prevent or at least alleviate hospital-acquired anemia, reduce the need for blood transfusions, and therefore have great potential to improve patient safety and medical outcome.

Accuracy of the Masimo Pronto-7® system in patients with left ventricular assist device

Background

The Masimo Pronto-7^® calculates hemoglobin (Hb) values using the pulsoximetry technique and a variety of mathematical algorithms analyzing the pulse waveform. Although this system has demonstrated a high level of accuracy in average patients, the performance might be altered in special patient populations. Regarding patients with left ventricular cardiac failure, a rotary blood pump generates a constant, continuous, non-pulsatile flow to improve effective cardiac output. Due to this alteration in both, blood flow and arterial blood pressure we hypothesized a reduced accuracy of the Masimo Pronto-7^® to detect Hb in patients with left ventricular cardiac failure. To test our hypothesis, we evaluated the Pronto-7^®SpHb system in outpatients after continuous-flow-left ventricular assist device (cf-LVAD) implantation (HeartMate II, Thoratec).

Methods

21 cf-LVAD outpatients from the Clinic for Cardiac, Thoracic and Vascular Surgery were investigated during routine follow up examinations. After venous blood samples were drawn, the Pronto-7^® sensor was attached to one randomly selected finger of one hand. The collected SpHb data were compared with Hb values measured by our central laboratory. The difference between the methods was determined using Bland – Altman analysis. The study was registered in the DRKS (DRKS00004415).

Results

In all cf-LVAD patients evaluated, the Pronto-7^® successfully detected SpHb values. Using Bland – Altman analysis, a bias of 0.14 g/dl (95% upper and lower limits of agreement ± 2.76 g/dl) was calculated.

Conclusion

The Pronto-7^® overestimated the actual Hb value in cf-LVAD outpatients with the HeartMate II. Due to this, we conclude that the system is suitable for screening in routine examinations and further analysis can be performed if needed. However, its use as an emergency tool is questionable because of the increased inaccuracy when Hb values are critically low.

Factors affecting hemoglobin measurement

A review of the literature shows that current "standard" laboratory measurements for hemoglobin are subject to numerous factors that affect both accuracy and reliability. In addition, total hemoglobin concentration measurements are subject to numerous factors that affect the "true" hemoglobin value. This article discusses both the physiologic factors that influence hemoglobin levels and the technical aspects and variability among the different measurement methodologies currently available.