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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 9  |  Issue : 1  |  Page : 57-62

Efficacy of noninvasive hemoglobin measurement by pulse co-oximetry in neonates


1 Department of Pediatrics, INHS Kalyani, Vishakapatnam, Andhra Pradesh, India
2 Department of Pediatrics, Armed Forces Medical College, Pune, Maharashtra, India

Date of Submission19-Aug-2019
Date of Decision14-Nov-2019
Date of Acceptance21-Nov-2019
Date of Web Publication29-Jan-2020

Correspondence Address:
Dr. Biju M John
Department of Pediatrics, Armed Forces Medical College, Pune, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcn.JCN_89_19

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  Abstract 


Background: Hemoglobin (Hb) measurement is one of the most commonly performed laboratory tests in neonates. The advent of new technologies enables us to carry out noninvasive Hb measurement, without having to prick the neonate, whereby reducing iatrogenic blood loss. There have been only few studies trying to ascertain the relationship between noninvasive Hb and conventional Hb in neonates. Against this background, this study was undertaken to evaluate the efficacy of noninvasive spectrophotometric Hb (SpHb) measurement by the pulse co-oximetry in neonates in comparison to laboratory Hb (Lab-Hb) and to study the influence of factors such as level of Hb and serum bilirubin on same. Materials and Methods: A cross-sectional study was carried out in the postnatal ward and neonatal intensive care unit of a tertiary hospital in Southern India. Hemodynamically stable admitted neonates (n = 100) had their SpHb estimation done using the Masimo Radical-7 Pulse Co-oximeter at the time they were being sampled for Hb. The paired data was then analyzed for the relationship between SpHb and Lab-Hb. Results: The mean ± standard deviation g/dL for Lab-Hb and SpHb was 16.21 ± 1.92 and 15.45 ± 1.28, respectively. There was a reasonable positive correlation between Lab-Hb and SpHb. (Pearson correlation: R = 0.714; P < 0.001). Bland–Altman analysis between Lab-Hb and SpHb revealed a bias (precision) to be 0.763 (1.349). The best agreement with respect to Hb levels was noticed in the Lab-Hb range of 12–18 g/dl and there was no significant influence of hyperbilirubinemia on the results. Conclusion: SpHb by the pulse co-oximetry is an efficacious method of assessing Hb trend among neonates.

Keywords: Neonates, Noninvasive hemoglobin, pulse co-oximetry, SpHb


How to cite this article:
Jamal AZ, John BM. Efficacy of noninvasive hemoglobin measurement by pulse co-oximetry in neonates. J Clin Neonatol 2020;9:57-62

How to cite this URL:
Jamal AZ, John BM. Efficacy of noninvasive hemoglobin measurement by pulse co-oximetry in neonates. J Clin Neonatol [serial online] 2020 [cited 2020 Jul 14];9:57-62. Available from: http://www.jcnonweb.com/text.asp?2020/9/1/57/277233




  Introduction Top


Hemoglobin (Hb) is measured very commonly in both healthy and sick neonates admitted to the hospital. It forms an integral part of investigations performed for various reasons such as anemia, polycythemia, sepsis, hemolytic jaundice, and blood loss. Conventional laboratory Hb (Lab-Hb) measurement is invasive, painful, and time-consuming. It also exposes the neonates to infections. Repeated phlebotomies performed for monitoring Hb in sick neonates can itself lead to significant anemia due to blood loss.[1],[2],[3],[4],[5]

The modality of noninvasive or minimally invasive Hb measurement has been around for the past 15 years. Over the past few years, numerous advancements have been made, pertaining to the technology, resulting in the availability of various ways of measuring noninvasive Hb. These include devices using occlusion spectrophotometry such as NBM-200 MP™ (OrSense, Ness Ziona, Israel) and pulse co-oximetry such as Masimo Radical-7 and Pronto-7. There have been studies using the point of care minimally invasive bedside blood analyzers and blood gas analyzers using methodologies such as azide-methemoglobin reaction, photometry absorbance, and co-oximetry.[6],[7],[8]

The Masimo Rainbow pulse co-oximeter uses spectrophotometry to noninvasively measure the various types of Hb in blood. The equipment emits pulsatile light of different wavelengths in both red and infrared spectrum and ascertains the absorbance by the different types of Hb and then calculates its levels.[3],[8],[9]

There have been multiple studies performed in adults, validating the relationship between Lab-Hb and SpHb, majority of which have shown a clinically acceptable correlation between the two, including in patients of trauma, during neurosurgeries, cardiovascular surgeries, and hysterectomies.[10],[11],[12],[13],[14],[15],[16],[17],[18],[19] However, only few studies have been performed in the pediatric and newborn population.[5],[20],[21],[22],[23]

The studies performed in neonates so far have indicated a variable correlation between Lab-Hb and SpHb, largely depending on the level of Hb. A contentious issue with respect to neonatal SpHb has also been related to the absorption coefficient of fetal Hb, which could putatively alter the reading in this population.[1],[2],[3],[4],[5],[20]

With this background, we performed this study on 100 neonates admitted to our hospital to assess the efficacy of SpHb as measured by Masimo Radical-7 with respect to Lab-Hb.


  Materials and Methods Top


We carried out a cross-sectional single-center study at a tertiary hospital in Southern India. All hemodynamically stable neonates admitted to the postnatal ward and neonatal intensive care unit (NICU) had their SpHb estimation done using the Masimo radical-7 pulse co-oximeter at the time they were being sampled for Hb for the different indications as per the unit policy. Based on similar previous studies, taking the predicted correlation as 0.7 with an α error of 0.05 and power as 90%, a sample of 100 was deemed appropriate. We thus enrolled 100 neonates for this study over an 18-month period. All hemodynamically unstable neonates were excluded from the study. After obtaining informed consent from their parents, patient details were recorded in a preset pro forma, which included gestational age, birth weight, antenatal risk factors, and reason for blood sampling. Venous blood samples were used for Lab-Hb measurement. These were performed based on treating doctor's instructions. Hb measurements in the laboratory were performed using a Sysmex XT-2000i hematology analyzer (TOA Medical Electronics Co. Ltd, Kobe, Japan). SpHb measurement was taken with a Radical-7 Pulse Co-oximetry (Masimo Radical-7 running board software version 7211; Masimo Corp.) immediately before blood sampling. A Rainbow R1 20 L adhesive sensor (Rev C; Masimo Corp.) connected to Radical-7 Pulse Co-oximetry was placed on the wrist of the neonate's right hand and covered with an opaque probe to eliminate the interference from ambient light. The analysis was carried out using both descriptive and inferential statistics. Pearson correlation between study variables was performed to find the degree of relationship between Lab-Hb and SpHb. Agreement between the Lab-Hb and SpHb was evaluated by Bland–Altman analysis. The study was approved by the Ethics Committee of the Institute.


  Results Top


A total of 100 patients were included in the final analysis. The demographic data with respect to our study participants including sex ratio, gestational age, birth weight, and postnatal age are described in [Table 1].
Table 1: Demographic and clinical data of the study population

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Neonatal jaundice was the most common reason for blood sampling in our study. There were 18 neonates born at <37 weeks and 82 born at term. Twenty-two neonates weighed <2.5 kg, 71 were between 2.5 and 3.5 kg, and seven were ≥3.5 kg. The correlation of Lab-Hb values with SpHb values was calculated for the entire population [Figure 1]. The correlation was also separately calculated for certain parameters such as level of Hb, birth weight, gestational age, and serum bilirubin, which could influence the results. Based on the Lab-Hb, three ranges of Hb values were defined for studying the correlation with SpHb [Table 2]. The correlation was positive and statistically significant for Hb range between 12 and 18 g/dl. The correlation was poor for Hb values >18 g/dl.
Figure 1: Correlation between laboratory hemoglobin and SpHb among the study population (n = 100)

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Table 2: Correlation at different ranges of laboratory hemoglobin

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Bland–Altman analysis of differences between the Hb values measured by two methods (Lab-Hb vs. SpHb) showed a good visual agreement [Figure 2].
Figure 2: Bland–Altman analysis of the two types of hemoglobin measurement

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Among the preterm neonates, there was a strong positive correlation between Lab-Hb and SpHb (r = 0.793, P < 0.001). Among the term neonates, there was a moderately positive correlation between Lab-Hb and SpHb (r = 0.677; P < 0.001). Among the low-birth-weight group, there was a strong positive correlation between Lab-Hb and SpHb (r = 0.819, P < 0.001). Among the normal birth weight group, there was a moderately positive correlation between Lab-Hb and SpHb (r = 0.650; P < 0.001).

As per the Masimo Radical-7 Pulse Co-oximeter operator manual, the SpHb values may be affected by intravascular dyes, low perfusion, low arterial oxygen saturation, and hyperbilirubinemia. In our study, we also looked at Lab-Hb and SpHb values based on total serum bilirubin (TSB) levels. However, the relationship seemed to be unaffected as both neonates with and without jaundice showed a positive correlation (r = 0.677, P < 0.001 for neonates with TSB >15 mg/dL and r = 0.722, P < 0.001 at total bilirubin <15 mg/dL).


  Discussion Top


Noninvasive Hb monitoring is a new technology that requires validation for its accuracy in different population subsets, as well as different perfusion states. Multiple studies have been conducted in adults, correlating the Lab-Hb and SpHb values, as an aid to decision-making for blood transfusion, during neurosurgeries, cardiovascular surgeries, and obstetric procedures.[6], 7, [10],[11],[12],[13],[14],[15],[16],[17],[18],[19] However, limited literature is available on the accuracy of noninvasive Hb monitoring in neonates.[1],[2],[3],[4],[5],[20] Various point of care devices are used in the hospital because they are portable and allow bedside results using small volume blood samples from the skin punctures. These devices have been found to be efficacious in various studies enabling their use in clinical practice. Whereas both Hb measured with a pulse co-oximeter and that with a point of care device significantly correlated with Lab-Hb, the point of care devices still have the disadvantage of requiring an invasive sampling.[8],[11] Thus, SpHb monitoring can be a potential addition to the noninvasive monitoring in NICU which could give continuous Hb trends, thus allowing suitable interventions, especially in sick neonates who are susceptible to hemodynamic changes.

We wanted to ascertain the utility of SpHb monitoring in hemodynamically stable neonates. In our study, 100 neonates admitted to our postnatal ward and NICU who underwent blood investigations for various reasons such as neonatal jaundice, sepsis screen, polycythemia, intrauterine growth restriction, and various other reasons were chosen as the study participants, for ascertaining the correlation between Lab-Hb and SpHb.

The mean ± standard deviation for Lab-Hb was 16.21 ± 1.92 and SpHb is 15.45 ± 1.28. Bland–Altman analysis revealed a good visual agreement between the Lab-Hb and SpHb values. The bias ± precision was 0.763 ± 1.349. We obtained a positive correlation between Lab-Hb and SpHb, as shown by the Pearson correlation coefficient (r = 0.714) which was statistically significant (P < 0.001). The linear regression analysis revealed y = 7.743 + 0.475x, where SpHb was depicted on the y-axis and Lab-Hb on the x-axis, revealing a positive univariate linear relationship between Lab-Hb and SpHb. The coefficient of determination (r2) was calculated as 0.51.

The influence of various parameters such as level of Hb, gestational age, birth weight, and serum bilirubin levels, on the correlation between Lab-Hb and SpHb was studied. There was a positive correlation for Hb values between 12 and 18 g/dl (r = 0.733 and P < 0.001), making it statistically significant. However, the correlation was poor for Lab-Hb values >18 g/dl. Inference regarding the correlation between Lab-Hb and SpHb for values <12 g/dl cannot be commented on, as the number of neonates with such values were very few in our study. Moreover, we also obtained a good correlation with statistical significance for both preterm (r = 0.793, P < 0.001) and term neonates (r = 0.677, P < 0.001). The correlation between Lab-Hb and SpHb values also seemed to be unaffected by birth weight of the study participants. The correlation coefficient for low birth weight and normal birth weight neonates was 0.819 and 0.650, respectively, with P < 0.001.

As per the operator's manual of Masimo Radical-7,[9] high-serum bilirubin levels may affect the SpHb values. However, in our study, the serum bilirubin levels were not found to affect the correlation between Lab-Hb and SpHb, as the neonates with jaundice (TSB >15 mg/dl) also showed a good correlation (r = 0.677 with a P < 0.001).

Most of the studies evaluating the efficacy of noninvasive Hb measurements have been conducted in adults. In one such study conducted by Macknet et al.,[10] 19 patients undergoing surgery were enrolled for SpHb continuous recording during the entire procedure. They concluded that there is a good correlation between the Lab-Hb and SpHb values. Similar results were obtained by Vos et al.,[14] who measured noninvasive Hb continuously in patients undergoing hepatic resection. Although they reported that the SpHb values were slightly underestimated, but the overall correlation with Hb (invasive satellite-Lab-Hb monitoring) was good. Kapoor et al.[15] enrolled 30 patients, undergoing pituitary surgery for Hb measurement through various modalities, such as conventional laboratory measurement, Hb measured by arterial blood gas analyzer, and SpHb noninvasively. They utilized the Spot Check (Pronto-7) Pulse Co-oximeter to record the SpHb values. They also got a positive correlation between Lab-Hb and SpHb. However, in a study conducted by Coquin et al.,[17] carried out in 33 patients admitted to a critical care unit with severe gastrointestinal bleeds, a poor correlation between Lab-Hb and SpHb was obtained, attributing the poor correlation to poor perfusion in such patients. Among a few studies conducted in neonates, a study conducted by Jung et al.[1] among 56 neonates showed a significant clinical and statistical correlation between SpHb and Lab-Hb. The correlation was much better with Hb values <18 g/dl as compared to values >18 g/dl. Moreover, they also mentioned that the bias was more with sick neonates. Even in our study, the correlation between Lab-Hb and SpHb was poor for Lab-Hb values >18 g/dl. In another study conducted by Nicholas et al.,[3] in 61 term and preterm neonates, a moderately positive correlation was reported between Lab-Hb and SpHb. In our study, the mean gestational age and birth weight of the study participants were higher, but the correlation between Lab-Hb and SpHb continued to be good in the low-birth-weight and preterm neonates. Similar to our study, they also recorded SpHb as a spot check rather than a continuous measurement. Bhat et al.[5] carried out a study in neonates and young children but included both healthy as well as sick patients. They reported that correlation for the sick patients was poor as compared to the healthy neonates, suggesting a poor perfusion as one of the major determinants for confirming the efficacy of noninvasive Hb monitoring. In our study, a major criterion for exclusion from the study was hemodynamic instability among the neonates, and therefore, no comments can be made regarding the validity of SpHb in neonates with shock. They reported a device failure of two out of 150 enrolled. The bias recorded in neonates in their study was higher compared to young children. However, the bias obtained in healthy neonates in their study was −0.98 ± 0.71 g/dl, which was comparable to our study (0.763 ± 1.349). In a recent study conducted by Lingaldinna et al.,[4] 158 newborns were enrolled, the bias between transcutaneous and venous Hb was reported as 1.66 ± 2.26 g/dl. It was 2.69 ± 1.87 g/dl at Hb <13 g/dl and 3.29 ± 1.86 at Hb ≤10 g/dl. They reported a device failure rate of 12.5%. On regression analysis, only the level of Hb was found to influence bias and device failure rate. Shock did not seem to influence the bias in their study. However, contrary to their study, the bias in our study was much higher for Lab-Hb >18 g/dl, whereas they reported a higher bias with low Hb values (<10 g/dl). In another study conducted by Panda and Sen,[20] a study on accuracy of noninvasive Hb measurement by the pulse co-oximetry was conducted in neonates, young children, and adults. Seventy-five patients were enrolled in each group, with the neonatal group reporting marginally higher SpHb values as compared to invasive Hb values. In our study, Lab-Hb values were higher than the SpHb values. They accepted Lab-Hb values measured within 2 days of recording SpHb values but we measured SpHb on the same day of collecting the blood sample for Lab-Hb.

It was observed that the difference in Lab-Hb and SpHb values among studies was not always consistent. For instance, the studies conducted by Bhat et al.,[5] Vos et al.,[14] and Coquin et al.,[17] and our study showed Lab-Hb values to be higher than the SpHb values, whereas in studies conducted by Nicholas et al.,[3] Jung et al.,[1] and Park et al.,[13] SpHb values were found to be higher than the Lab-Hb values.

Our study shows that noninvasive SpHb measurement is likely to be a useful adjunct in the management of neonates. The utility is perhaps more toward assessing the Hb trend noninvasively than as a substitute for Lab-Hb. There were a few limitations to our study. The population subset we chose were relatively stable neonates which included only few preterms with low-Hb levels. Our study involved intermittent noninvasive Hb monitoring, whereas it is believed that continuous SpHb monitoring, especially in sick preterm neonates would prove to be more clinically useful. Another limitation noticed during the study was the high cost of measuring Hb noninvasively by Masimo Radical-7 using the R1 20 L SpHb probe, which could limit its clinical utility in resource-limited settings.

Although our study has revealed a reasonable correlation between Lab-Hb and SpHb in a population subset of stable neonates, studies designed with a greater number of neonates, with a more diverse demographic and clinical profile including poor perfusion, acute blood loss, and lower Hb, will have to be conducted, to further validate our findings.


  Conclusion Top


SpHb, as measured by the pulse co-oximetry, has a reasonable positive correlation with Lab-Hb and is potentially useful for noninvasively assessing Hb trend among neonates.

Acknowledgment

We would like to acknowledge the Armed Forces Medical Research Committee, India.

Financial support and sponsorship

This study was financially supported by the Armed Forces Medical Research Committee, India.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Jung YH, Lee J, Kim HS, Shin SH, Sohn JA, Kim EK, et al. The efficacy of noninvasive hemoglobin measurement by pulse CO-oximetry in neonates. Pediatr Crit Care Med 2013;14:70-3.  Back to cited text no. 1
    
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Bhat A, Upadhyay A, Jaiswal V, Chawla D, Singh D, Kumar M, et al. Validity of non-invasive point-of-care hemoglobin estimation in healthy and sick children – A method comparison study. Eur J Pediatrics 2015;175:171-9.  Back to cited text no. 5
    
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