Noninvasive Hemoglobin Monitoring: A Rapid, Reliable, and Cost-Effective Method Following Total Joint Replacement

Prospective Noninvasive Hemoglobin Monitoring in the Outpatient Total Joint Arthroplasty Setting

BACKGROUND

Total joint arthroplasty (TJA) is increasingly being performed as an outpatient (i.e., same-day discharge) procedure. Postoperatively, orthostatic hypotension or pain-related tachycardia can lead to concerns regarding the hemoglobin (Hgb) level of the patient prior to discharge. The purpose of this study was to prospectively assess the reliability and accuracy of, and patient and nurse satisfaction with, postoperative noninvasive hemoglobin (nHgb) monitoring compared with an invasive serum hemoglobin (iHgb) laboratory draw in the outpatient TJA setting.

METHODS

We prospectively enrolled 200 patients undergoing outpatient unilateral TJA, of whom 157 were ultimately included in our analysis (94 hips, 63 knees). Postoperatively, both nHgb and iHgb values were obtained at a mean of 36 minutes apart. Surveys were completed by patients and nurses. The strength of the agreement between the 2 Hgb monitoring methods was evaluated with use of the Bland-Altman 95% limits of agreement, concordance correlation coefficient (CCC), and intraclass correlation coefficient (ICC). Receiver operating characteristic curve analyses were performed to investigate the ability of nHgb monitoring to predict an iHgb of <11.2 g/dL (the 5th-percentile iHgb value).

RESULTS

The mean preoperative iHgb was 14.2 ± 1.1 g/dL. The mean postoperative iHgb and nHgb values were 13.3 ± 1.5 and 13.3 ± 1.2 g/dL, respectively. The Bland-Altman 95% limits of agreement were -3.2 and +3.1 g/dL, indicating that 95% of patients' iHgb values are expected to fall between these limits relative to the nHgb value of the patient. The CCC and ICC were both 0.33. An nHgb cutoff value of <12.7 g/dL had 100% sensitivity and 67% specificity for detecting an iHgb of <11.2 g/dL. Patients reported less pain with the nHgb test than with the iHgb test (mean pain score, 0.0 versus 1.8; p < 0.001), and 97% of patients preferred the nHgb test. Following the nHgb test, 73% of responding patients and 83% of responding nurses were "somewhat more reassured" to "significantly more reassured" about same-day discharge.

CONCLUSIONS

Routine nHgb testing can rapidly screen patients undergoing outpatient TJA for acute anemia prior to discharge. With an nHgb of <12.7 g/dL, there was perfect sensitivity and 67% specificity for detecting an iHgb of <11.2 g/dL. Most patients and nurses felt more reassured about same-day discharge after nHgb monitoring.

LEVEL OF EVIDENCE

Diagnostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Evaluation of Non-Invasive Hemoglobin Monitoring in Perioperative Patients: A Retrospective Study of the Rad-67TM (Masimo)

Background: Hemoglobin (Hb) is a crucial parameter in perioperative care due to its essential role for oxygen transport and tissue oxygenation. Accurate Hb monitoring allows for timely interventions to address perioperative anemia and, thus, prevent morbidity and mortality. Traditional Hb measurements rely on invasive blood sampling, which significantly contributes to iatrogenic anemia and poses discomfort and increased infection risks. The advent of non-invasive devices like Masimo's Rad-67™, which measures Hb using pulse CO-oximetry (SpHb), offers a promising alternative. This study evaluates the accuracy of SpHb compared to clinical standard blood gas analysis (BGA) in perioperative patients. Methods: This retrospective study analyzed 335 paired Hb measurements with an interval <15 min between SpHb and BGA in the operating theater and post-anesthesia care unit of a university hospital. Patients experiencing hemodynamic instability, acute bleeding, or critical care were excluded. Statistical analysis included Bland-Altman plots and Pearson correlation coefficients (PCCs) to assess the agreement between SpHb and BGA. Potential confounders, e.g., patient age, skin temperature, sex, perfusion index (PI), and atrial fibrillation, were also analyzed. Results: The bias of the SpHb compared to BGA according to Bland-Altman was 0.00 g/dL, with limits of agreement ranging from -2.70 to 2.45 g/dL. A strong correlation was observed (r = 0.79). Overall, 57.6% of the paired measurements showed a deviation between the two methods of ≤±1 g/dL; however, this applied to only 33.3% of the anemic patients. Modified Clark's Error Grid analysis showed 85.4% of values fell within clinically acceptable limits. Sex was found to have a statistically significant, but not clinically relevant, effect on accuracy (p = 0.02). Conclusions: The Rad-67TM demonstrates reasonable accuracy for non-invasive SpHb, but exhibits significant discrepancies in anemic patients with overestimating low values. While it offers potential for reducing iatrogenic blood loss, SpHb so far should not replace BGA in critical clinical decision-making.

Accuracy of Non-Invasive Hemoglobin (nHgb) Monitoring in an AIS Population

Local Problem: Needle phobia and fear of blood draws are very common in children and adolescents. Noninvasive hemoglobin (nHgb) monitoring in children was first introduced in the Intensive Care Unit (ICU) setting. Later, our total joint arthroplasty colleagues demonstrated that nHgB monitoring was more efficient, less expensive, and preferred by patients compared to invasive hemoglobin (iHgb) monitoring. Specific Aims: The goal of this Quality Initiative (QI) project is to compare the accuracy and reliability when comparing nHgb monitoring and iHgb (blood draw) in an Adolescent Idiopathic Scoliosis (AIS) population. The purpose was to evaluate the correlation between nHgb and iHgb monitoring and develop a nHgb threshold above which a patient would no longer require a blood draw, thus minimizing resource utilization as well as blood draw-related anxiety and pain during the postoperative period. Intervention: We enrolled 60 consecutive patients undergoing posterior spine fusion/instrumentation (PSFI) for AIS. Average estimated blood loss (EBL) was 415cc, and 189 cc was returned via cell saver. 2/60 (3.3%) patients required an allogenic blood transfusion perioperatively. nHgb and iHgb values were obtained within 60 minutes of each other at three separate time points (preoperative, in Post-Anesthesia Care Unit (PACU), and postoperative day (POD 1) at 0700) iHgb and nHgb values were recorded. The results were retrospectively reviewed and analyzed. Paired t tests were utilized to compare mean (n/i) Hgb values. Pearson correlation coefficients were calculated at all three time points. Receiver Operating Characteristic (ROC) curve analysis was performed on the postoperative values to determine a threshold. Results: There was a moderate positive correlation at all three time points (0.4, 0.59, 0.6) (p= 0.005, <0.001, <0.001). At all three time points, the mean nHgb value was 1-2 g/dL higher than the mean iHgb value, and this was statistically significant. Guidelines for an Allogenic Blood Transfusion (ABT) at our institution were developed through consensus between the surgical and anesthesia teams. Indications for a postoperative ABT include iHgb 7.0 - 8.0 g/dL along with clinical signs of anemia such as persistent hypotension, tachycardia, dyspnea, lethargy, confusion, postural dizziness not responsive to a fluid challenge, or iHgb <7.0 g/dL, regardless of signs/symptoms of anemia. There were not enough data points to correlate nHgb measurements with a patient's need to receive an ABT due to the low occurrence rate (3.3%). Therefore, we focused on a nHgb threshold at which a postoperative venous blood draw would not be necessary. 54/60 patients had a lab value of iHgb ≥ 9.0g/dL at 0700 on POD 1 and only 6 of the 60 patients had an iHgb ≤ 8.0 g/dL. Thus, we chose iHgb ≥ 9.0g/dL as the threshold. Based on data from the ROC curve analysis, a patient with a nHgb value of ≥10.8 g/dL had an iHgb value of ≥9.0 g/dL with 87% sensitivity. Based on the ABT guidelines stated above, no patient with a nHgb ≥ 10.8 g/dl would require an ABT, therefore a venipuncture would be unnecessary. Conclusions: Noninvasive Hgb monitoring was found to correlate with iHgb in pediatric AIS patients undergoing PSFI. Surgeons could consider screening AIS patients postoperatively with nHgb monitoring and only order iHgb measurement if the nHgb value is <10.8 g/dL resulting in improvement in the patient experience.

Noninvasive Hemoglobin Monitoring for Postoperative Pediatric Orthopaedic Patients: A Preliminary Study

BACKGROUND

Hemoglobin (Hgb) levels are frequently checked through venipuncture [invasive hemoglobin (iHgb)] in pediatric orthopaedic patients after high blood loss procedures. This needlestick may causes further anxiety and fear in hospitalized children. Noninvasive hemoglobin (nHgb) monitoring has been effectively utilized in the adult intensive care and postoperative total joint arthroplasty setting. nHgb monitoring has not yet been validated in children for routine postoperative Hgb assessment in pediatric orthopaedics.

METHODS

In this prospective study, 46 pediatric orthopaedic patients were enrolled who were undergoing surgery and postoperative standard of care iHgb testing. On postoperative day 1, Hgb levels were obtained through venipuncture and nHgb monitor (Pronto-7; Masimo) within a 2-hour period. Patient preferences, iHgb and nHgb values, time to result, and provider preferences were recorded. Cost data were estimated based on the standard Medicare payment rates for lab services versus the cost of nHgb probe.

RESULTS

nHgb results were obtained after 1 attempt in 38 patients (83%), after multiple attempts in 7 patients (15%), and could not be obtained in 1 patient. The mean time to obtain nHgb value was significantly shorter than that to obtain iHgb results (1.3±1.5 vs. 40±18.1 min; P <0.0001). The mean nHgb value was significantly higher than the mean iHgb value (11.7±1.5 vs. 10.6±1.1 g/dL, P <0.0001). nHgb exceeded iHgb by 2 g/dL or more in 12 (26%) patients (2.64±0.9 vs. 0.54±0.84 g/dL; P <0.0001). The concordance correlation coefficient between the 2 Hgb methods was 0.59, indicating moderate agreement. Forty-three (93%) of our patients and 34 (74%) of the care providers preferred nHgb over iHgb if results were equivalent. At our institution, the cost per iHgb monitoring is approximately $28 per blood draw as compared with $5 for nHgb monitoring. Interestingly, no patients required postoperative transfusion during the study period, as asymptomatic patients with no cardiac disease are typically observed unless the Hgb is <6.

CONCLUSIONS

nHgb monitoring in postoperative pediatric patients overestimated Hgb levels compared with the standard of care methods; however, nHgb had high patient and provider satisfaction and had moderate agreement with iHgb. As no patients required transfusion, postoperative Hgb checks could likely be discontinued in some portion of our population.

LEVEL OF EVIDENCE

Level Ib-Diagnostic study.

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

OBJECTIVE

Hemoglobin (Hb) measurement is one of the most commonly used laboratory tests in medical practice. Unnecessary blood sampling, especially in neonatal intensive care units (NICUs), contributes to iatrogenic anemia. Continuous non-invasive monitoring of total Hb (SpHb) was compared with invasive venous blood samples (tHb) in NICU patients.

METHODS

Three hundred and ten patients were identified in NICU. Non-invasive Hb measurement was performed immediately before venous blood sampling and comparison of invasive with non-invasive values was undertaken.

RESULTS

There was a strongly positive correlation between SpHb and tHb (r = 0.965, p < 0.001). Bland-Altman analysis was performed in 95% limits of agreement for Hb values measured by both methods. The mean bias between tHb and SpHb measurements was 0.05 g/dl (-1.85 to 1.96). In Passing-Bablok regression analysis, the CUSUM test p value was found to be 0.98 for Hb levels measured by SpHb and tHb; and the difference between the methods was not significant.

CONCLUSION

In newborns, SpHb method offers reliable Hb values, which are comparable with the more traditional tHb method. Continuous non-invasive monitoring of total Hb may help prevent unnecessary blood sampling and iatrogenic anemia. Further clinical studies are required for the effectiveness of the method in critically ill patients with circulatory disorders.

Can an outpatient risk assessment tool predict who needs postoperative haemoglobin monitoring?

AIMS

Recent improvements in surgical technique and perioperative blood management after total joint replacement (TJR) have decreased rates of transfusion. However, as many surgeons transition to outpatient TJR, obtaining routine postoperative blood tests becomes more challenging. Therefore, we sought to determine if a preoperative outpatient assessment tool that stratifies patients based on numerous medical comorbidities could predict who required postoperative haemoglobin (Hb) measurement.

METHODS

We performed a prospective study of consecutive unilateral primary total knee arthroplasties (TKAs) and total hip arthroplasties (THAs) performed at a single institution. Prospectively collected data included preoperative and postoperative Hb levels, need for blood transfusion, length of hospital stay, and Outpatient Arthroplasty Risk Assessment (OARA) score.

RESULTS

A total of 504 patients met inclusion criteria. Mean age at time of arthroplasty was 65.3 years (SD 10.2). Of the patients, 216 (42.9%) were THAs and 288 (57.1%) were TKAs. Six patients required a blood transfusion postoperatively (1.19%). Transfusion after surgery was associated with lower postoperative day 1 Hb (median of 8.5 (interquartile range (IQR) 7.9 to 8.6) vs 11.3 (IQR 10.4 to 12.2); p < 0.001), longer length of stay (1 day (IQR 1 to 1) vs 2 days (IQR 2 to 3); p < 0.001), higher OARA score (median of 60.0 (IQR 40 to 75) vs 5.0 (IQR 0-35); p = 0.001), and total hip arthroplasty (p < 0.001). All patients who received a transfusion had an OARA score > 34; however, this did not reach statistical significance as a screening threshold.

CONCLUSION

Risk of blood transfusion after primary TJR was uncommon in our series, with an incidence of 1.19%. Transfusion was associated with OARA scores > 60. The OARA score, not American Society of Anesthesiologists grade, reliably identified patients at risk for postoperative blood transfusion. Selective Hb monitoring may result in substantial cost savings in the era of cost containment. Cite this article: Bone Joint J 2021;103-B(1):65-70.

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.

Transcutaneous Hemoglobin Screening in an Adult Orthopaedic Trauma Population

OBJECTIVES

To evaluate a noninvasive hemoglobin measurement device in an orthopaedic trauma population.

DESIGN

Prospective.

SETTING

Level 1 trauma center.

PATIENTS/PARTICIPANTS

One hundred five patients consecutively admitted to the orthopaedic trauma service after surgical treatment of fracture.

INTERVENTION

Transcutaneous hemoglobin (TcHgb) monitoring using the Masimo Pronto Pulse CO-Oximeter model with Rainbow SET Technology for spot TcHgb measurement.

MAIN OUTCOME MEASUREMENTS

TcHgb measurements and standard venipuncture hemoglobin (vHgb) were obtained. Patient preferences for each were recorded.

RESULTS

TcHgb measurements were obtained in 100 patients and compared with their corresponding vHgb measurements. The mean vHgb and TcHgb were 10.2 ± 1.9 g/dL and 11.2 ± 2.1 g/dL, respectively, and the mean difference was 1.1 ± 1.6 g/dL, which was statistically different from 0 (P < 0.001). In 76% of cases, the TcHgb device overestimated vHgb. In a subgroup of patients undergoing procedures with minimal expected blood loss (external fixators of knee or ankle, irrigation and debridement, or open reduction and internal fixation of ankle or calcaneal fractures), the mean difference between vHgb and TcHgb was 0.68 ± 1.6 g/dL (P = 0.06).

CONCLUSIONS

A preliminary study of TcHgb monitoring with the tested device as a potential screening mechanism to limit unnecessary blood draws showed statistical difference from vHgb; however, the mean bias 1.1 g/dL of hemoglobin was notably small. In a subgroup of patients undergoing procedures with minimal expected blood loss, the device may have merit. Larger studies are required to determine the clinical relevance of differences in measurements between the 2 methods.

LEVEL OF EVIDENCE

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Intraoperative continuous noninvasive hemoglobin monitoring in patients with placenta previa undergoing cesarean section: a prospective observational study

Background

Obstetric patients with placenta previa are at risk for sever peripartum hemorrhage. Early detection of anemia and proper transfusion strategy are important for the management of obstetric hemorrhage. In this study, we assessed the utility and accuracy of noninvasive hemoglobin (SpHb) monitoring in patients with placenta previa during cesarean section.

Methods

Parturients diagnosed with placenta previa and scheduled for cesarean section under spinal anesthesia were enrolled. SpHb and laboratory Hb (Lab-Hb) were measured during surgery as primary outcomes.

Results

Seventy-four pairs of SpHb and Lab-Hb were collected from 39 patients. The correlation coefficient was 0.877 between SpHb and Lab-Hb (P < 0.001). The Bland–Altman plot showed a mean difference ± SD of 0.3 ± 0.8 g/dl between noninvasive Hb and Lab-Hb, and the limits of agreement were −1.2 to 1.8 g/dl. The magnitude of the difference between SpHb and Lab-Hb was < 0.5 g/dl in 64.9%; however, it was > 1.5 g/dl in 10.8%.

Conclusions

SpHb monitoring had a good correlation with Lab-Hb. A small mean difference between SpHb and lab-Hb might not be clinically significant; however, the limits of agreements were not narrow. In particular, SpHb could be overestimated in the anemic population. Based on our results, further studies investigating the accuracy and precision of SpHb monitoring should be performed in parturients presenting Hb below 10 g/dl.

Preoperative Hemoglobin Predicts Postoperative Transfusion Despite Antifibrinolytics During Total Knee Arthroplasty

Current antifibrinolytics have decreased perioperative blood loss; however, some patients still require transfusions postoperatively. The authors sought to determine the risk factors associated with postoperative transfusions and to establish a "cutoff" preoperative hemoglobin threshold value specific to total knee arthroplasty (TKA) that would identify patients who would benefit from blood conservation programs. The institutional database was queried for primary TKA patients. Preoperative patient demographics and hemoglobin values were determined in addition to intraoperative and postoperative variables, including transfusion rate. Patients were stratified by whether they received a transfusion perioperatively, and risk factors were identified through univariable and multivariable analysis. Optimal cutoff values for hemoglobin were identified by concurrently maximizing the sensitivity and specificity for predicting the risk of a postoperative transfusion event. Men and women were analyzed independently. A total of 532 primary TKAs were included for analysis, and 33 patients (6.2%) required a transfusion. Advanced age (P=.019), low pre-operative hemoglobin value (P<.001), and failure to receive tranexamic acid (P<.001) were associated with increased risk of postoperative transfusion. A preoperative hemoglobin value of 12.5 g/dL was identified as the optimal cutoff for predicting postoperative transfusion requirements across all patients, with a sensitivity of 84.8% and a specificity of 76.4%. Preoperative anemia remains predictive of transfusion following TKA despite current antifibrinolytics. Patients with a preoperative hemoglobin value of less than 12.5 g/dL who are not receiving intravenous tranexamic acid are particularly at risk and should be considered for blood conservation programs. [Orthopedics. 2019; 42(2):103-109.].