Effect of hyperbilirubinemia on the accuracy of continuous non-invasive hemoglobin measurements in liver transplantation recipients

This study evaluated the effect of hyperbilirubinemia on the accuracy of continuous non-invasive hemoglobin (SpHb) measurements in liver transplantation recipients. Overall, 1465 SpHb and laboratory hemoglobin (Hb) measurement pairs (n = 296 patients) were analyzed. Patients were grouped into normal (< 1.2 mg/dL), mild-to-moderate (1.2-3.0 mg/dL), and severe (> 3.0 mg/dL) hyperbilirubinemia groups based on the preoperative serum total bilirubin levels. Bland-Altman analysis showed a bias of 0.20 (95% limit of agreement, LoA: - 2.59 to 3.00) g/dL, 0.98 (95% LoA: - 1.38 to 3.35) g/dL, and 1.23 (95% LoA: - 1.16 to 3.63) g/dL for the normal, mild-to-moderate, and severe groups, respectively. The four-quadrant plot showed reliable trending ability in all groups (concordance rate > 92%). The rates of possible missed transfusion (SpHb > 7.0 g/dL for Hb < 7.0 g/dL) were higher in the hyperbilirubinemia groups (2%, 7%, and 12% for the normal, mild-to-moderate, and severe group, respectively. all P < 0.001). The possible over-transfusion rate was less than 1% in all groups. In conclusion, the use of SpHb in liver transplantation recipients with preoperative hyperbilirubinemia requires caution due to the positive bias and high risk of missed transfusion. However, the reliable trending ability indicated its potential use in clinical settings.

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.

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.

Can Non-Invasive Spectrophotometric Hemoglobin Replace Laboratory Hemoglobin Concentrations for Preoperative Anemia Screening? A Diagnostic Test Accuracy Study

Preoperative assessment of hemoglobin concentration in blood is important to diagnose anemia. The primary aim of this prospective diagnostic test accuracy study was to monitor non-invasive spectrophotometric hemoglobin (SpHb, g/dL) concentrations among adults prior to elective surgery and to investigate the correlation and agreement of SpHb with laboratory hemoglobin (Hb, g/dl). A secondary aim was to identify the anemia cut-off values for SpHb based on the World Health Organization (WHO) definitions for anemia. This study included 151 consecutive patients (age ≥ 18 year) presenting for preoperative evaluation prior to scheduled elective general or orthopedic surgery. Results identified the mean ± SD of SpHb at 11.43 ± 2.01 g/dL, which underestimated the mean laboratory Hb (12.64 ± 2.29 g/dL, p < 0.001). A bias mean difference (SpHb-Hb) of -1.21 g/dL, with a SD of 1.76, was reported. This bias (SpHb-Hb) was inversely correlated with the mean Hb concentrations. A positive correlation existed between SpHb and Hb, with a good degree of reliability and a significant Intra Class Correlation (ICC). SpHb diagnosed anemia in 32.3% and 60.3% of males and females, respectively. The SpHb cut-off values to identify anemia were 11.3 and 10.2 g/dL for males and females, respectively, with a sensitivity of 83.3% for males and only 62.9% for females. The specificity for males and females were 81% and 91.3%, respectively. SpHb sensitivity allows for anemia diagnosis among males, but not females. However, the specificity allows SpHb to rule out anemia for both.

Progressive evaluation in spectroscopic sensors for non-invasive blood haemoglobin analysis - a review

Frequent monitoring of haemoglobin concentration is highly recommended by physicians to diagnose anaemia and polycythemia Vera. Moreover, Some other conditions also demand assessment of haemoglobin, and these conditions are blood loss, before blood donation, during pregnancy, preoperative, perioperative and postoperative conditions. Cyanmethaemoglobin/haemiglobincyanide method, portable haemoglobinometers and haematology analyzers are few standard methods to diagnose mentioned ailments. However, discomfort, delay and risk of infection are typical limitations of traditional measuring solutions. These limitations create the necessity to develop a non-invasive haemoglobin monitoring technique for a better lifestyle. Various methods and products are already developed and popular due to their non-invasiveness; however, invasive solutions are still considered as the reference standard method. Therefore, this review summarizes the attributes of existing non-invasive solutions. These attributes are finalized as brief details, accuracy, optimal benefits, and research challenges for exploring potential gaps, advancements and possibilities to consider as futuristic alternative methodologies. Non-invasive total haemoglobin assessing techniques are mainly based on optical spectroscopy (reflectance/transmittance) or digital photography or spectroscopic imaging in spot check/continuous monitoring mode. In all these techniques, we have noticed that there is a need to consider different light conditions, motion artefacts, melanocytes, other blood constituents, smoking and precise fixing of the sensor from the sensing spot for exact formulation. Moreover, based on careful and critical analysis of outcomes, none of these techniques or products is used independently or intended to replace invasive laboratory testing. Therefore there is a requirement for a more accurate technique that can eliminate the requirement of blood samples and likely end up as a reference standard method.

Accuracy of Continuous and Noninvasive Hemoglobin Monitoring in the Presence of CO2 Insufflation: An Observational Pilot Study

Background

Laparoscopic surgery has several benefits, but it requires prolonged carbon dioxide (CO₂) insufflation. Several factors affect the accuracy of continuous and noninvasive hemoglobin (SpHb) monitoring, but the effects of CO₂ insufflation are undetermined. This study investigated the effect of CO₂ insufflation on SpHb monitoring in laparoscopic surgery.

Material/Methods

Twenty patients undergoing laparoscopic gastrectomy were enrolled. Anesthesia was maintained using sevoflurane and remifentanil within an end-tidal CO₂ of 30–45 mmHg. The CO₂ insufflation was maintained at 12 mmHg using CO₂. SpHb was monitored with a Radical-7 Pulse CO-Oximeter, and laboratory hemoglobin (tHb) was analyzed using a satellite blood analyzer.

Results

Forty paired measurements were analyzed. The mean perfusion index, SpHb, and tHb were 3.10±1.77%, 10.92±1.48 g/dL, and 11.51±0.88 g/dL, respectively. SpHb underestimated tHb with a bias (precision) of −0.59 (1.28 g/dL), and the 95% limit of agreement was wide (−3.11 to 1.92 g/dL). SpHb was moderately correlated with tHb (r=0.50, 95% CI: 0.23 to 0.70). The concordance rate was 67%. ΔSpHb was not correlated with ΔtHb (r=0.29, 95% CI: −0.18 to −0.65). A similar bias, wider limits of agreement, a higher |SpHb-tHb|, but more significant correlation between SpHb and tHb were observed for the “PaCO₂ <40 mmHg” range compared with the “40 mmHg ≤PaCO₂” range.

Conclusions

SpHb may have an acceptable accuracy but has a weak trending ability in the presence of CO₂ insufflation, and it can be affected by PaCO₂. Further research on the effects of CO₂ insufflation on SpHb is needed.

Accuracy of non-invasive haemoglobin measurements in patients undergoing transurethral resection of prostate surgery

Background and Aims:

The aim of this study was to evaluate the accuracy of non-invasive haemoglobin (SpHb) compared to laboratory venous haemoglobin (tHb) measurements among patients undergoing elective transurethral resection of prostate (TURP) surgery under spinal anaesthesia.

Methods:

In a prospective, observational, outcome-assessor blinded, cohort trial, we enroled 50 American Society of Anesthesiologists physical status (ASA-PS) I-II patients with benign prostatic hyperplasia. The primary outcome included SpHb and tHb measurements performed at four perioperative time-points: just before initiating the fluid preload (T1), and at 30 min (T2), 1 h (T3), and 2 h (T4) after starting the prostate resection, respectively. Statistical tool included intra-class correlation (ICC), Bland-Altman plots, and linear regression analysis.

Results:

We collected 200 SpHb/tHb data sets from 50 patients. The SpHb had a non-significant negative bias of –0.83 g/dL, –0.43 g/dL, –0.81 g/dL, and –0.46 g/dL, with limits of agreement of 2.6 g/dL to –4.2 g/dL, 2.4 g/dL to –3.3 g/dL, 1.3 g/dL to –2.8 g/dL, and 1.4 g/dL to –2.3 g/dL, for T1 to T4, respectively. The SpHb/tHb pairs correlated significantly (time-dependent increase in ICC from T1 to T4). The SpHb-tHb difference correlated significantly with corresponding serum sodium (T1 to T3), but not with perfusion index. No correlation existed between % change in SpHb-tHb difference (T1 to T4), and intraoperative blood loss or perioperative weight gain.

Conclusion:

The SpHb exhibited a clinically acceptable negative bias compared to tHb during TURP surgery. Although a wide limit of agreement between the SpHb/tHb pairs is a limitation, the real-time SpHb trends can still serve in clinical judgement.

Reliability of a spot check non-invasive hemoglobin monitoring (SpHb) of the Masimo RAD-67™ and the HemoCue® for anemia screening

Background : To test the reliability of the spot check Masimo Rad-67 (Masimo Corp., Irvine, CA, USA) as part of a preoperative anemia screening, hemoglobin measurements were compared to those of the HemoCue® Hb 201+ System (HemoCue AB, Ängelholm, Sweden) and the standard laboratory measurement. Methods : During preoperative evaluation of patients scheduled for elective orthopedic surgery hemoglobin concentration was simultaneously determined by standard laboratory analysis (HbLab), the HemoCue® Hb 201+ System (HbHemocue) and by Pulse Co-Oximetry using the Masimo Rad-67 (SpHb) with the rainbow® DCI®-mini Sensor (Masimo Corp., Irvine, CA, USA). Linear correlation, agreement (Bland-Altman analysis), sensitivity/specificity and positive/negative prediction values (PPV/NPV) for anemic hemoglobin values were determined. P-values less than 0.05 were considered statistically significant. Results : 303 patients were analyzed. Twenty-one patients (12 male and 9 female) had mild or moderate anemia, detected by HbLab. In 20 patients, the HbHemocue, and in 34 patients, the SpHb detected anemia. Linear correlation and mean bias (limits of agreement, LOA) for HbHemocue and HbLab were r = 0.969 and -1.08 (+6.44/-8.60) g/L, and for SpHb and HbLab r = 0.61 and +1.76 (+26.92/-23.4) g/L. Sensitivity/specificity of the HbHemocue to detect anemia in all, male and female patients were 85.0/99.3%, 75.0/100/% and 88.9/98.9/% with a PPV/NPV of 89.5/98.9%, 100/98.0% and 80.0/99.3%, respectively. Sensitivity/specificity of SpHb to detect anemia for all, male and female patients were 71.4%, 93.3%, 75.0/95.2/% and 66.7/91.1%, with a PPV/NPV for all, male and female patients of 44.1/97.8%, 56.3/97.9% and 33.3/97.7%, respectively. Conclusions : HbHemocue and HbLab show a strong linear correlation and a good agreement, while linear correlation of SpHb and HbLab is moderate and agreement poor. For both devices, anemia detection is moderate, but the positive prediction value for anemia is much better with the HbHemocue. Both devices reliably detected non-anemic patients. Glossary : CO = carbon monoxide ; PPV = positive predicted value ; NPV = negative predicted value ; HbLab = hemoglobin determined by the laboratory ; HbHemocue = hemoglobin determined by the HemoCue device ; SpHb = hemoglobin determined by the Masimo-RAD67 device ; LOA = limits of agreement ; LOS = length of stay ; POC = point of care ; SpO2 = arterial hemoglobin ; PR = pulse rate ; PI = perfusion index ; PVI = plethysmography variability index ; SpCO = carboxyhemoglobin ; SpMet = methemoglobin ; LED = Light Emitting Diodes ; HiCN = hemiglobincyanide ; SLS = Sodium Lauryl Sulphate ; BMI = body mass index ; BT = body temperature ; WHO = World Health Organization ; IQR = interquartile range ; MAP = mean arterial pressure ; HF = heart frequency ; SD = standard deviation Key point Summary : – Question : Is Hb measurement of the Masimo Rad-67 and of the HemoCue reliable? – Findings : Non-anemic patients are reliably detected with the Masimo Rad-67. Of the 303 patients examined, HbLab detected twenty-one patients (12 male and 9 female) with mild or moderate anemia. The Hbhemocue showed anemia in 20 patients, while the SpHb identified 34 patients as anemic. HbHemocue and HbLab showed a strong linear correlation and a good agreement, while linear correlation of SpHb and HbLab was moderate and agreement poor. For both devices, anemia detection is moderate, but the positive prediction value for anemia is much better with the HbHemocue. Both devices reliably detected non-anemic patients. – Meaning : With both devices, non-anemic patients are reliably recognized, while anemia detection is moderate. However, the prediction for the presence of anemia is much better with the Hbhemocue.

Noninvasive hemoglobin monitoring in clinical trials: a systematic review and meta-analysis

Background and objectives

The measurement of hemoglobin concentration (Hb) by co-oximetry is an innovative technique that offers efficiency and agility in the processing of information regarding the measurement of Hb obtained through continuous, non-invasive and rapid monitoring. Because of this attribute, it avoids unnecessary exposures of the patient to invasive procedures by allowing a reduction in the number of blood samples for evaluation and other unnecessary therapies. It also helps to make decisions about the need for transfusion and how to handle it. The objective of this study is to compare the performance offered to obtain Hb values between the Masimo Corporation (Irvine, CA, USA) instrument and the standard gold tool (laboratory examination).

Contents

The study corresponds to a systematic review followed by meta-analysis, which included fully registered full-text clinical trials published from 1990 to 2018. PubMed, Cochrane, Medline, Embase and Web of Science databases were investigated. The mean overall difference found between the non-invasive and invasive methods of hemoglobin monitoring was 0.23 (95% CI −0.16, 0.62), that is, it did not present statistical significance (p = 0.250). The results of the analysis of heterogeneity within and between the studies indicated high levels of inconsistency (Q = 461.63, p < 0.0001, I² = 98%), method for Hb values.

Conclusions

Although the mean difference between noninvasive measurements of Hb and the gold standard method is small, the co-oximeter can be used as a non-invasive “trend” monitor in detecting unexpected responses at Hb levels.

Continuous Noninvasive Hemoglobin Monitoring Reflects the Development of Acute Hemodilution After Consecutive Fluid Challenges

BACKGROUND

Consecutive fluid challenges (FCs) are frequently administered to maximize the stroke volume (SV) as part of a goal-directed therapy (GDT) strategy. However, fluid administration may also cause acute hemodilution that might lead to an actual paradoxical decrease in oxygen delivery (DO2). The aim of this study was to examine whether continuous noninvasive hemoglobin (SpHb) monitoring can be used to detect the development of acute hemodilution after graded fluid administration.

METHODS

In 40 patients who underwent major vascular or gastrointestinal surgery, an FC, consisting of 250 mL colloid solution, was administered. When the SV increased by ≥10%, the FC was repeated up to a maximum of 3 times. Laboratory-measured hemoglobin concentrations (BHb), SpHb, SV, cardiac output (CO), and DO2 values were recorded after each FC.

RESULTS

All 40 patients received the first FC, 32 patients received the second FC, and 20 patients received the third FC (total of 750 mL). Out of the 92 administered FCs, only 55 (60%) caused an increase in SV ≥10% ("responders"). The first and the second FCs were associated with a significant increase in the mean CO and DO2, while the mean SpHb and BHb decreased significantly. However, the third and last FC was associated with no statistical difference in CO and SV, a further significant decrease in mean SpHb and BHb, and a significant decrease in DO2 in these patients. Compared to their baseline values (T0), BHb and SpHb decreased by a mean of 5.3% ± 4.9% and 4.4% ± 5.2%, respectively, after the first FC (T1; n = 40), by 9.7% ± 8.4% and 7.9% ± 6.9% after the second FC (T2; n = 32), and by 14.5% ± 6.2% and 14.6% ± 5.7% after the third FC (T3; n = 20). Concordance rates between the changes in SpHb and in BHb after the administration of 250, 500, and 750 mL colloids were 83%, 90%, and 100%, respectively.

CONCLUSIONS

Fluid loading aimed at increasing the SV and the DO2 as part of GDT strategy is associated with acute significant decreases in both BHb and SpHb concentrations. When the administration of an FC is not followed by a significant increase (≥10%) in the SV, the DO2 decreases significantly due to the development of acute hemodilution. Continuous noninvasive monitoring of SpHb does not reflect accurately absolute BHb values, but may be reliably used to detect the development of acute hemodilution especially after the administration of at least 500 mL of colloids.

Development and Validation of a Photoplethysmography System for Noninvasive Monitoring of Hemoglobin Concentration

Background. Traditional invasive hemoglobin (Hb) detection led to delayed diagnosis, operational inefficiency, incorrect critical decision making, and uncomfortable patient experience. To facilitate real-time total hemoglobin (tHb) monitoring, a portable prototype of a noninvasive Hb detection system was developed, and the accuracy of Hb predicted based on partial least squares (PLS) as well as backpropagation artificial neural network (BP-ANN) models was validated. Results. The prototype was combined with a signal processing circuit and a spectrophotometric probe containing 8 wavelength LEDs light source and photodiode array. Laboratory invasive Hb (Lab_tHb) and spot check Hb measurements with PLS (SpHb_PLS) and BP (SpHb_BP) methods were obtained simultaneously by hematology analyzer and the designed system. The invasive and noninvasive estimates of the Hb levels were analyzed using Spearman correlation as well as Bland–Altman plot and receiver operating characteristic (ROC) curve analysis. A total of 238 volunteers had attempted laboratory invasive and noninvasive spot check Hb measurements. Mean Lab_tHb, SpHb_PLS, and SpHb_BP were 13.6 ± 1.80 g/dL, 13.5 ± 1.07 g/dL, and 13.6 ± 1.06 g/dL, respectively. Noninvasive SpHb_PLS (r = 0.61, p<0.001) and SpHb_BP (r = 0.62, p<0.001) had a strong correlation with invasive tHb values. The Bland–Altman plot showed excellent consistency between the proposed noninvasive methods and laboratory invasive reference. In ROC analysis, PLS and BP models were good at predicting Hb ≥ 12 g/dL with area under the curve of 0.828 and 0.824, respectively. Observed differences between invasive and noninvasive Hb measurements displayed no significant correlation with perfusion index values. Conclusions. The result confirmed that noninvasive Hb monitoring had an excellent correlation with traditional invasive Hb measurement. Furthermore, it is suggested that the developed prototype has the potential for the noninvasive detection of Hb concentration with the methods of PLS and BP-ANN.

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.

Journal of clinical monitoring and computing end of year summary 2018: hemodynamic monitoring and management

Hemodynamic management is a mainstay of patient care in the operating room and intensive care unit (ICU). In order to optimize patient treatment, researchers investigate monitoring technologies, cardiovascular (patho-) physiology, and hemodynamic treatment strategies. The Journal of Clinical Monitoring and Computing (JCMC) is a well-established and recognized platform for publishing research in this field. In this review, we highlight recent advancements and summarize selected papers published in the JCMC in 2018 related to hemodynamic monitoring and management.

The effect of fluid resuscitation on the effective circulating volume in patients undergoing liver surgery: a post-hoc analysis of a randomized controlled trial

To assess the significance of an analogue of the mean systemic filling pressure (Pmsa) and its derived variables, in providing a physiology based discrimination between responders and non-responders to fluid resuscitation during liver surgery. A post-hoc analysis of data from 30 patients undergoing major hepatic surgery was performed. Patients received 15 ml kg-1 fluid in 30 min. Fluid responsiveness (FR) was defined as an increase of 20% or greater in cardiac index, measured by FloTrac-Vigileo®. Dynamic preload variables (pulse pressure variation and stroke volume variation: PPV, SVV) were recorded additionally. Pvr, the driving pressure for venous return (=Pmsa-central venous pressure) and heart performance (EH; Pvr/Pmsa) were calculated according to standard formula. Pmsa increased following fluid administration in responders (n = 18; from 13 ± 3 to 17 ± 4 mmHg, p < 0.01) and in non-responders (n = 12; from 14 ± 4 to 17 ± 4 mmHg, p < 0.01). Pvr, which was lower in responders before fluid administration (6 ± 1 vs. 7 ± 1 mmHg; p = 0.02), increased after fluid administration only in responders (from 6 ± 1 to 8 ± 1 mmHg; p < 0.01). EH only decreased in non-responders (from 0.56 ± 0.17 to 0.45 ± 0.12; p < 0.05). The area under the receiver operating characteristics curve of Pvr, PPV and SVV for predicting FR was 0.75, 0.73 and 0.72, respectively. Changes in Pmsa, Pvr and EH reflect changes in effective circulating volume and heart performance following fluid resuscitation, providing a physiologic discrimination between responders and non-responders. Also, Pvr predicts FR equivalently compared to PPV and SVV, and might therefore aid in predicting FR in case dynamic preload variables cannot be used.

Noninvasive Continuous Hemoglobin Monitoring in Combat Casualties: A Pilot Study

OBJECTIVE

To describe the accuracy and precision of noninvasive hemoglobin measurement (SpHb) compared with laboratory or point-of-care Hb, and SpHb ability to trend in seriously injured casualties.

METHODS

Observational study in a convenience sample of combat casualties undergoing resuscitation at two US military trauma hospitals in Afghanistan. SpHb was obtained using the Masimo Rainbow SET (Probe Rev E/Radical-7 Pulse CO-Oximeter v 7.6.2.1). Clinically indicated Hb was analyzed with a Coulter or iStat and compared with simultaneous SpHb values.

RESULTS

Twenty-three patients were studied (ISS 20 ± 9.8; age 29 ± 9 years; male 97%; 100% intubated). Primary injury cause: improvised explosive device (67%) or gunshot (17%). There were 49 SpHb-Hb pairs (median 2 per subject). Bias: 0.3 ± 1.6 g/dL (95% LOA -2.4, 3.4 g/dL). The SpHb-Hb difference < ± 1 g/dL in 37% of pairs. Eighty-six percent of pairs changed in a similar direction. Using an absolute change in Hb of >1 g/dL, a concurrent absolute change in SpHb of >1 g/dL had a sensitivity: 61%, specificity 85%, positive predictive value: 80%, and a negative predictive value: 69%. The SpHb signal was present in 4643 of 6137 min monitored (76%).

CONCLUSIONS

This was the first study to describe continuous SpHb in seriously injured combat casualties. Using a threshold of 1 g/dL previously specified in the literature, continuous SpHb is not precise enough to serve as sole transfusion trigger in trauma patients. Further research is needed to determine if it is useful for trending Hb changes or as an early indicator of deterioration in combat casualties.

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

PURPOSE

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.

METHODS

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 0.5 µg/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.

RESULTS

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 ± 0.70 g/dl, p < 0.05). Changes in SpHb-tHb are correlated with changes in PI (r = 0.46, p < 0.05).

CONCLUSIONS

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.

Accuracy and Trending of Continuous Noninvasive Hemoglobin Monitoring in Patients Undergoing Liver Transplantation

BACKGROUND

Shift in large fluid volumes and massive blood loss during liver transplantation frequently leads to rapid changes in hemoglobin (Hb) concentration; thus, to ensure adequate tissue oxygenation, accurate and rapid determination of Hb concentration is essential in transplant recipients. The Radical-7 Pulse CO-Oximeter provides a noninvasive and continuous way to monitor Hb concentration (SpHb) in real time and is an ideal candidate for use during liver transplantation. In this study, we assessed the relationship between SpHb and total Hb (tHb) obtained from arterial blood samples during surgery.

METHODS

Forty patients undergoing liver transplantation were enrolled in this study. tHb and time-matched SpHb were measured at 5 different phases throughout surgery. Paired SpHb and tHb levels were assessed using linear regression, Bland-Altman analysis, and the Critchley polar plot method.

RESULTS

A total of 161 paired measurements with sufficient signal quality were analyzed. The correlation between SpHb and tHb was 0.59 (P < .001). Bland-Altman analysis revealed that a bias between SpHb and tHb was 2.28 g/dL, and limits of agreement (LoA) were from -0.78 to 5.34 g/dL. Trending analysis showed that 87% of data were located within the acceptable trending area, indicating that the trending ability was not satisfied.

CONCLUSIONS

The Radical-7 Pulse CO-Oximeter was not sufficient to monitor Hb levels and trends during liver transplantation surgery in our cohort. In particular, in critical patients and in those with low Hb levels, invasive Hb measurement should be used for assessment.

Utility of non-invasive haemoglobin monitoring in oncosurgery patients

BACKGROUND AND AIMS

Oncosurgeries may incur massive blood loss demanding frequent blood sampling to assess blood loss and the need for intraoperative blood transfusions. Accuracy of non-invasive spectrophotometric haemoglobin (hereafter to be referred as SpHb) monitoring has been studied in various perioperative settings. The intraoperative use of Radical-7^®, Masimo Corp., (Radical-7^®) for SpHb monitoring may be useful during cancer surgery. The aim of this study is to evaluate the intraoperative utility of SpHb monitoring by the Radical-7^® to guide intraoperative transfusion in oncosurgeries.

METHODS

Fifty adult patients, undergoing oncosurgery with anticipated blood loss of more than 20% of blood volume, were selected. Continuous SpHb monitoring was performed intraoperatively and blood transfusion was based on SpHb values. Simultaneous laboratory haemoglobin (LabHb) samples were taken for validation. The accuracy of intraoperative blood transfusions based on SpHb was analysed using Error Grid Analysis. Paired measurements of SpHb and LabHb were compared using Bland-Altman plot analysis.

RESULTS

There were 66 paired data points for blood transfusion from fifty patients with a correlation of 73% (P < 0.001) between SpHb and LabHb. In the Bland-Altman analysis, the bias was - 0.313 g/dl with ~ 95% of values within the limits of agreement of 1.81 g/dl to -2.44 g/dl. In the Error Grid Analysis, most data points were in the least error zone (Zone A).

CONCLUSION

The Radical-7^® has the advantage of providing SpHb value continuously to take prompt decision regarding blood transfusion intraoperatively.

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.

Noninvasively Measured Hemoglobin Concentration Reflects Arterial Hemoglobin Concentration Before but Not After Cardiopulmonary Bypass in Patients Undergoing Coronary Artery or Valve Surgery

OBJECTIVE

This study compared noninvasively measured hemoglobin and arterial hemoglobin before and after cardiopulmonary bypass in patients undergoing coronary artery or valve surgery.

DESIGN

Observational study with retrospective data analysis.

SETTING

Veterans Affairs hospital.

PARTICIPANTS

Thirty-five men.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Hemoglobin values were measured noninvasively by co-oximetry to corresponding arterial hemoglobin concentrations taken at clinically relevant time points chosen at the discretion of the cardiac anesthesiologist. Thirty-five and 27 pooled pairs of data were obtained before and after cardiopulmonary bypass, respectively. Arterial hemoglobin concentration was analyzed using i-STAT CG8+test cartridges routinely used in the authors' operating rooms and those of other institutions. Linear regression and Bland-Altman analysis revealed a significant positive bias, wide limits of agreement, and low correlation coefficients between the noninvasive and arterial hemoglobin measurements. These findings were especially notable after compared with before cardiopulmonary bypass.

CONCLUSIONS

The results suggested that noninvasive measurement of hemoglobin overestimates arterial hemoglobin by almost 1 g/dL when compared to iSTAT. A lack of precision also was observed with noninvasive measurement of hemoglobin, especially after cardiopulmonary bypass. These findings supported the contention that sole reliance on noninvasive measurement of hemoglobin for transfusion decisions in cardiac surgery patients may be inappropriate.

Meta-analytic estimation of measurement variability and assessment of its impact on decision-making: the case of perioperative haemoglobin concentration monitoring

Background

As a part of a larger Health Technology Assessment (HTA), the measurement error of a device used to monitor the hemoglobin concentration of a patient undergoing surgery, as well as its decision consequences, were to be estimated from published data.

Methods

A Bayesian hierarchical model of measurement error, allowing the meta-analytic estimation of both central and dispersion parameters (under the assumption of normality of measurement errors) is proposed and applied to published data; the resulting potential decision errors are deduced from this estimation. The same method is used to assess the impact of an initial calibration.

Results

The posterior distributions are summarized as mean ± sd (credible interval). The fitted model exhibits a modest mean expected error (0.24 ± 0.73 (−1.23 1.59) g/dL) and a large variability (mean absolute expected error 1.18 ± 0.92 (0.05 3.36) g/dL). The initial calibration modifies the bias (−0.20 ± 0.87 (−1.99 1.49) g/dL), but the variability remains almost as large (mean absolute expected error 1.05 ± 0.87 (0.04 3.21) g/dL). This entails a potential decision error (“false positive” or “false negative”) for about one patient out of seven.

Conclusions

The proposed hierarchical model allows the estimation of the variability from published aggregates, and allows the modeling of the consequences of this variability in terms of decision errors. For the device under assessment, these potential decision errors are clinically problematic.

Electronic supplementary material

The online version of this article (doi:10.1186/s12874-016-0107-5) contains supplementary material, which is available to authorized users.

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).

Accuracy of pleth variability index to predict fluid responsiveness in mechanically ventilated patients: a systematic review and meta-analysis

To systemically evaluate the accuracy of pleth variability index to predict fluid responsiveness in mechanically ventilated patients. A literature search of PUBMED, OVID, CBM, CNKI and Wanfang Data for clinical studies in which the accuracy of pleth variability index to predict fluid responsiveness was performed (last update 5 April 2015). Related journals were also searched manually. Two reviewers independently assessed trial quality according to the modified QUADAS items. Heterogeneous studies and meta-analysis were conducted by Meta-Disc 1.4 software. A subgroup analysis in the operating room (OR) and in intensive care unit (ICU) was also performed. Differences between subgroups were analyzed using the interaction test. A total of 18 studies involving 665 subjects were included. The pooled area under the receiver operating characteristic curve (AUC) to predict fluid responsiveness in mechanically ventilated patients was 0.88 [95 % confidence interval (CI) 0.84-0.91]. The pooled sensitivity and specificity were 0.73 (95 % CI 0.68-0.78) and 0.82 (95 % CI 0.77-0.86), respectively. No heterogeneity was found within studies nor between studies. And there was no significant heterogeneity within each subgroup. No statistical differences were found between OR subgroup and ICU subgroup in the AUC [0.89 (95 % CI 0.85-0.92) versus 0.90 (95 % CI 0.82-0.94); P = 0.97], and in the specificity [0.84 (95 % CI 0.75-0.86) vs. 0.84 (95 % CI 0.75-0.91); P = 1.00]. Sensitivity was higher in the OR subgroup than the ICU subgroup [0.84 (95 % CI 0.78-0.88) vs. 0.56 (95 % CI 0.47-0.64); P = 0.00004]. The pleth variability index has a reasonable ability to predict fluid responsiveness.

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.

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.

The accuracy of non-invasively continuous total hemoglobin measurement by pulse CO-Oximetry undergoing acute normovolemic hemodilution and reinfusion of autologous blood

BACKGROUND

Non-invasively continuous total hemoglobin (SpHb) measurement has not been assessed adequately in acute bleeding and rapid blood transfusion during surgery. Thus, we have assessed the efficacy of SpHb during both acute normovolemic hemodilution (ANH) and autologous blood transfusion (ABT).

METHODS

Twenty-four patients undergoing urological and gynecological surgery were enrolled. ANH was induced by withdrawing blood of 800 g with simultaneous fluid administration. When surgical hemostasis was completed, collected blood was reinfused. Measurement of SpHb, perfusion index (PI) and real total Hb (tHb) were done before and after each 400 ml blood removal (-0, -400, -800 ml) and reinfusion (+0, +400, +800 ml).

RESULTS

A Bland-Altman analysis for repeated measurements showed a bias (precision) g/dl of 1.12 (1.25), 1.43 (1.24) and 1.10 (1.23) for all data, during ANH and during ABT, respectively. Additionally, a bias (precision) increased with a reduction in tHb (g/dl): ≥10.0; 0.74 (1.30), 8.0-10.0; 1.15 (1.12) and <8.0; 1.60 (1.28). Although the difference between SpHb and tHb was almost zero before anesthesia induction, it became significant just before ANH and did not change further by ANH and ABT. Significant correlations between SpHb and tHb for all data (r = 0.75, n = 228, p < 0.001) were observed. PI slightly correlated with the difference between SpHb and tHb (r = 0.38, n = 216, p < 0.001). Furthermore, before and after induction of anesthesia, PI also correlated with the difference between SpHb and tHb (r = 0.42, n = 23, p = 0.048 and r = 0.51, n = 22, p = 0.016, respectively).

CONCLUSIONS

The present data suggest that SpHb may overestimate tHb during ANH and ABT. In addition, PI and tHb levels had an impact on the accuracy of SpHb measurements.

A comparison of lidocaine and bupivacaine digital nerve blocks on noninvasive continuous hemoglobin monitoring in a randomized trial in volunteers

BACKGROUND

Blood hemoglobin can be monitored continuously and noninvasively with a noninvasive spectrophotometric sensor (Masimo SpHb). The perfusion index (PI) of the finger is directly related to the clinical accuracy of SpHb. We evaluated those variables that influence PI without the influences of surgery and anesthesia.

METHODS

Based on our past studies, 12 awake adult volunteers were studied. A SpHb sensor was attached to the same finger of each hand. The temperature of each finger was measured via a skin surface probe. A digital nerve block (DNB) was performed with 1% lidocaine on one finger and 0.25% bupivacaine on the other finger of the opposite hand. SpHb, PI, and finger temperature were monitored continuously 30 minutes before and 3 to 4 hours after placement of the DNB. A random effects spline regression was used to flexibly model the outcomes before and after the DNB and to compare the effects of lidocaine and bupivacaine.

RESULTS

The DNBs increased the PI for both lidocaine and bupivacaine (P < 0.0001) and finger temperature from both lidocaine (P < 0.0001) and bupivacaine (P = 0.02). The duration of action of bupivacaine was markedly longer than that of lidocaine (P < 0.0001). Between 45 and 75 minutes after insertion of the DNB, the PI with bupivacaine was substantially higher than that of lidocaine. The PI was directly related to changes in finger temperature and SpHb. During this time interval, 11 of the 12 volunteers receiving bupivacaine descriptively had increases in finger temperature ranging from no change to 6.1°C. In contrast, only 6 of the 12 lidocaine volunteers had increases in finger temperature ranging from no change to 4°C. Changes in PI were directly correlated with SpHb values (correlation coefficient = 0.7).

CONCLUSIONS

A DNB increases PI and finger temperature. These increases lasted 2 to 3 hours longer with bupivacaine than lidocaine. The increases in PI were associated with slightly higher SpHb values. We conclude that the DNB induces increases in PI and temperature of the finger. Because of the close relationship between finger temperature, PI, and SpHb, consistently increasing finger temperature and PI could increase the accuracy of SpHb.

Microwaving blood as a non-destructive technique for haemoglobin measurements on microlitre samples

The non-destructive ex vivo determination of haemoglobin (Hgb) concentration offers the capability to conduct multiple red blood cell haematological measurements on a single sample, an advantage that current optical techniques are unable to offer. Here, a microwave method and device for the accurate and non-destructive determination of Hgb concentration in microlitre blood samples are described. Using broadband microwave spectroscopy, a relationship is established between the dielectric properties of murine blood and Hgb concentration that is utilized to create a technique for the determination of Hgb concentration. Subsequently, a microwave dielectric resonator-microfluidic system is implemented in the analysis of 52 murine samples with microlitre volumes and Hgb concentrations ranging from 0 to 17 g dL(-1) . Using the characterized relationship, independent and minimally invasive Hgb measurements are made on nine healthy mice as well as seven with mutations in the Adenomatous polyposis coli (APC) gene that leads to colorectal cancer and consequently anaemia.

Evaluation of multiwave pulse total-hemoglobinometer during general anesthesia

The purpose of this prospective study was to evaluate the accuracy and trending ability of a four-wavelength pulse-total hemoglobinometer that continuously and noninvasively measures hemoglobin in surgical patients. With IRB approval and informed consent, spectrophotometric hemoglobin (SpHb) was measured with a pulse-total hemoglobinometer manufactured by Nihon Kohden Corp (Tokyo, Japan) and compared to the CO-oximeter equipped with blood gas analyzer. Two hundred twenty-five samples from 56 subjects underwent analysis. Bland-Altman analysis revealed that the bias ± precision of the current technology was 0.0 ± 1.4 g/dl and -0.2 ± 1.3 g/dl for total samples and samples with 8 < Hb < 11 g/dl, respectively. The percentages of samples with intermediate risk of therapeutic error in error grid analysis and the concordance rate of 4-quadrant trending assay was 17 % and 77 %, respectively. The Cohen kappa statistic for Hb < 10 g/dl was 0.38, suggesting that the agreement between SpHb and CO-oximeter-derived Hb was fair. Collectively, wide limits of agreement, especially at the critical level of hemoglobin, and less than moderate agreement against CO-oximeter-derived hemoglobin preclude the use of the pulse-total hemoglobinometer as a decision-making tool for transfusion.