The role of carboxyhemoglobin measured with CO-oximetry in the detection of hemolysis in newborns with ABO alloimmunization

Role of Cord Blood Carboxyhemoglobin in Detecting Significant Hyperbilirubinemia in Term Neonates with ABO Alloimmunization

OBJECTIVE

This study aimed to assess whether cord blood carboxyhemoglobin (COHb) levels in jaundiced term neonates with and without a positive direct Coombs test (DCT) and in healthy controls could be used as a predictor of severe hyperbilirubinemia. The percentage of cord blood COHb should be higher among neonates with Coombs-positive ABO hemolytic disease than among those with Coombs-negative ABO incompatibility and higher than that of ABO-compatible control neonates.

STUDY DESIGN

This cross-sectional descriptive study of 198 term neonates comprised three subgroups: group I featured 68 DCT-positive ABO-incompatible neonates (ABO + DCT), group II featured 60 DCT-negative ABO-incompatible neonates with hyperbilirubinemia (ABO-DCT), and group III featured 70 healthy controls. COHb was determined by an OSM3 hemoximeter.

RESULTS

Group I differed from groups II and III for cord blood bilirubin, cord blood hemoglobin, and cord blood hematocrit. Groups I and II had higher mean total serum bilirubin (TSB) levels than group III, while there was no difference in the mean TSB levels between groups I and II. There was no significant difference between the COHb group means for groups I, II, and III (p = 0.98). The area under the receiver operating characteristic curve calculated for group I/group III and group II/group III were found to be 0.62 and 0.54, respectively.

CONCLUSION

COHb levels did not prove to be superior to the DCT for predicting the risk of developing severe hyperbilirubinemia in term neonates.

KEY POINTS

· COHb levels do not predict the risk of developing severe hyperbilirubinemia in term neonates.. · COHb levels may predict that ABO incompatibility in early life.. · COHb levels did not prove to be superior to the direct coombs test..

Clinical Factors Influencing Endogenous Carbon Monoxide Production and Carboxyhemoglobin Levels in Neonates

Carboxyhemoglobin (COHb) is an index of endogenous carbon monoxide formation during the hem degradation process and could be used to confirm hemolysis in neonates. The influence of other clinical factors on COHb values in neonates has not been fully investigated. We aimed to evaluate the influence of hemolysis, sepsis, respiratory distress, and postnatal age on COHb values. We retrospectively analyzed COHb measurements determined with a carbon monoxide-oximeter in 4 groups of term neonates: A-sepsis, B-respiratory distress, C-hemolysis, and D-healthy neonates. The mean COHb values were 1.41% (SD: 0.26), 1.32% (SD: 0.27), 2.5% (SD: 0.69), and 1.27% (SD: 0.19) (P<0.001) in groups A (n=8), B (n=37), C (n=16), and D (n=76), respectively. COHb in group C was significantly higher than in the other groups. There was a negative correlation between postnatal age and COHb in healthy neonates. A cut-off level of 1.7% had 93% (95% confidence interval [CI]: 89%-97%) sensitivity and 94% (95% CI: 90%-98%) specificity for diagnosis of hemolysis. COHb values were higher during the first days of life. We found that COHb levels in neonates with hemolysis were significantly higher and that the influence of sepsis and respiratory distress on COHb values was insignificant.

Carboxyhaemoglobin levels and free-radical-related diseases in prematurely born infants

BACKGROUND

Carboxyhaemoglobin (COHb) levels may reflect the level of early oxidative stress which plays a role in mediating free-radical-related diseases in prematurely born infants.

AIM

To assess the relationship of COHb levels in the first seven days of after birth to the development of bronchopulmonary dysplasia (BPD) and other free-radical-related diseases.

STUDY DESIGN

Retrospective analysis of routinely performed COHb via blood gas samples of infants born at less than 30 weeks of gestation admitted to a tertiary neonatal intensive care unit was undertaken.

SUBJECTS

One hundred and four infants were included with a median (range) gestational age of 27.4 (22.4-29.9) weeks and a birthweight of 865 (395-1710) grams.

OUTCOMES

The maximum COHb per infant per day was recorded for the first 28 days and BPD and other free-radical-related diseases including intraventricular haemorrhage (IVH) were noted. The severity of BPD, requirement for home oxygen on discharge and survival to discharge were also recorded.

RESULTS

Infants who developed BPD (n = 76) had significantly higher COHb levels in the first seven days [1.7% (0.3-6.8)] compared to those that did not develop BPD [1.6% (0.9-3.8); p = 0.001]. Higher COHb levels in the first seven days after birth were also observed in infants with grade three/four IVH [n = 20; 1.9% (1.0-6.8)] compared to those without [1.6% (0.3-5.6); p < 0.001]. COHb levels, however, were not associated with the duration of ventilation, BPD severity or survival to discharge.

CONCLUSION

Higher COHb levels in prematurely born infants were associated with the development of BPD and IVH.

Neonatal hyperbilirubinemia management: Clinical assessment of bilirubin production

The predominant cause of elevated total/plasma bilirubin (TB) levels is from an increase in bilirubin production primarily because of ongoing hemolysis. If undiagnosed or untreated, the risk for developing extreme neonatal hyperbilirubinemia and possibly bilirubin-induced neurological dysfunction (BIND) is increased. Since carbon monoxide (CO) and bilirubin are produced in equimolar amounts during the heme catabolic process, measurements of end-tidal CO levels, corrected for ambient CO (ETCOc) can be used as a direct indicator of ongoing hemolysis. A newly developed point-of-care ETCOc device has been shown to be a useful for identifying hemolysis-associated hyperbilirubinemia in newborns. This review summarizes the biology of bilirubin production, the clinical utility of a novel device to identify neonates undergoing hemolysis, and a brief introduction on the use of ETCOc measurements in a cohort of neonates in China.

A Neglected and Promising Predictor of Severe Hyperbilirubinemia Due to Hemolysis: Carboxyhemoglobin

Aims: We investigated the relationship between total serum bilirubin (TSB) and carboxyhemoglobin (COHb) in term neonates with detected and treated hemolysis within a particular time frame with the aim of augmenting the case for early diagnosis and prevention of morbidity in hemolysis. Materials and Methods: The study group comprised term newborns who were above the 95th percentile for TSB, underwent intravenous immunoglobulin (IVIG) or applied total exchange transfusion due to hemolysis. Newborns without hemolysis who were above the 95th TSB percentile and required phototherapy comprised the control group. Results: At a cutoff COHb value of 2.2%, 80.8% sensitivity, 95.5% specificity, 18.1 likelihood ratio, positive predictive value of 94.7%, and negative predictive value of 83.2% were identified. Conclusion: We found that COHb is a sensitive and specific method for detecting hemolysis, and it can be used in the early diagnosis of hemolytic diseases causing early and severe hyperbilirubinemia.

Elevated blood carboxyhemoglobin levels as an early predictor of phototherapy requirement in moderate and late preterm infants

Objective: Preterm infants are prone to increased bilirubin burden and display adverse outcomes if left unmonitored; therefore, predicting an increased bilirubin production is of paramount importance.Methods: We aimed to evaluate carboxyhemoglobin (COHb) levels in moderate (GA: 32^0/7-33^6/7) and late preterm (GA: 34^0/7-36^6/7) infants to assess whether this molecule could be used as an early predictor of phototherapy requirement.Results: A total of 221 infants were enrolled in the study. On admission, carboxyhemoglobin levels of infants who received phototherapy were significantly higher than that of infants who did not require this treatment, and this difference persisted in the consecutive hours (median (min-max): 1.2% (0.3-1.7) versus 0.8% (0.4-1.1); p < .001). The initial and consecutive COHb levels showed positive correlation (r = 0.77, p < .001). In the post-hoc analysis, direct antiglobulin test positivity significantly affected phototherapy requirement (p < .001). Receiver operating characteristics analysis showed that a COHb level of ≥0.95% was found to have a sensitivity of 90% and a specificity of 88%. Multinomial logistic regression analysis demonstrated that high COHb levels on admission significantly increased the likelihood of phototherapy requirement when adjusted for covariants (adjusted odds ratio: 2.2; 95% confidence interval: 1.4-3.5; p < .001).Conclusion: Carboxyhemoglobin measurement can be simply used to predict preterm infants who will require phototherapy.

Hemolysis during and after 21 days of head-down-tilt bed rest

Hemoconcentration is observed in bed rest studies, descent from altitude, and exposure to microgravity. Hemoconcentration triggers erythrocyte losses to subsequently normalize erythrocyte concentration. The mechanisms of erythrocyte loss may involve enhanced hemolysis, but has never been measured directly in bed rest studies. Steady‐state hemolysis was evaluated by measuring two heme degradation products, endogenous carbon monoxide concentration [CO] and urobilinogen in feces, in 10 healthy men, before, during, and after two campaigns of 21 days of 6° head‐down‐tilt (HDT) bed rest. The subjects were hemoconcentrated at 10 and 21 days of bed rest: mean concentrations of hemoglobin (15.0 ± 0.2 g/L and 14.6 ± 0.1 g/L, respectively) and erythrocytes (5.18 ± 0.06E6/μL and 5.02 ± 0.06E6/μL, respectively) were increased compared to baseline (all Ps < 0.05). In contrast, mean hemoglobin mass (743 ± 19 g) and number of erythrocytes (2.56 ± 0.07E13) were decreased at 21 days of bed rest (both Ps < 0.05). Indicators of hemolysis mean [CO] (1660 ± 49 ppb and 1624 ± 48 ppb, respectively) and fecal urobilinogen concentration (180 ± 23 mg/day and 199 ± 22 mg/day, respectively) were unchanged at 10 and 21 days of bed rest compared to baseline (both Ps > 0.05). A significant decrease in [CO] (−505 ppb) was measured at day 28 after bed rest. HDT bed rest caused hemoconcentration in parallel with lower hemoglobin mass. Circulating indicators of hemolysis remained unchanged throughout bed rest supporting that enhanced hemolysis did not contribute significantly to erythrocyte loss during the hemoconcentration of bed rest. At day 28 after bed rest, decreased hemolysis accompanied the recovery of erythrocytes, a novel finding.

ABO hemolytic disease of the fetus and newborn: thirteen years of data after implementing a universal bilirubin screening and management program

OBJECTIVE

ABO hemolytic disease occurs among neonates with blood groups A or B delivered to group O women. Extreme neonatal hyperbilirubinemia due to ABO disease has been reported, but its frequency is not well known. We sought to determine the odds of developing severe ABO hemolytic disease in the 13 years since adopting universal bilirubin screening/management in the Intermountain Healthcare system.

STUDY DESIGN

We conducted a retrospective analysis of neonates born between 2004 and 2016, defining "severe hemolytic disease" as; (1) total serum bilirubin (TSB) >25 mg/dL, or (2) hospital readmission for jaundice, or (3) bilirubin encephalopathy. Neonates born to group O (+) mothers were included and considered either; (1) Controls (not at risk for ABO disease because they were group O), (2) Study subjects (at risk for ABO disease because they were group A or B).

RESULTS

Of 400,531 live births, 47% were to group O women; 86% of whom were group O (+). Overall, 42,529 (27%) neonates born to group O (+) women had their blood group determined; 29,729 (68%) were O, 10,682 (25%) A, and 3109 (7%) B. Peak TSBs during the first 10 days were higher in group A (11.0 ± 4.2 mg/dL) and B (11.5 ± 4.3) than group O neonates (10.3 ± 4.1). However the relative risks of a TSB ≥25 mg/dL, readmission for jaundice, or kernicterus, were the same in the control vs. study groups.

CONCLUSIONS

In our health system, severe hemolytic disease in neonates born to group O (+) woman is not more likely in group A or B neonates than in controls (group O). We recognize that in other practices, particularly those who do not have a universal bilirubin screening/management program, ABO hemolytic disease severity might be different than in our system.

Determinants of Carboxyhemoglobin Levels and Relationship with Sepsis in a Retrospective Cohort of Preterm Neonates

Carboxyhemoglobin levels in blood reflect endogenous carbon monoxide production and are often measured during routine blood gas analysis. Endogenous carbon monoxide production has been reported to be increased during sepsis, but carboxyhemoglobin levels have not been thoroughly evaluated as a biomarker of sepsis. We sought to determine whether carboxyhemoglobin levels were elevated during sepsis in a high risk population of premature neonates. We conducted a retrospective cohort study of 30 infants in two neonatal intensive care units using electronic medical and laboratory records. The majority of infants were extremely premature and extremely low birth weight, and 25 had at least one episode of sepsis. We collected all carboxyhemoglobin measurements during their in-patient stay and examined the relationship between carboxyhemoglobin and a variety of clinical and laboratory parameters, in addition to the presence or absence of sepsis, using linear mixed-effect models. We found that postnatal age had the most significant effect on carboxyhemoglobin levels, and other significant associations were identified with gestational age, hemoglobin concentration, oxyhemoglobin saturation, and blood pH. Accounting for these covariates, there was no significant relationship between the onset of sepsis and carboxyhemoglobin levels. Our results show that carboxyhemoglobin is unlikely to be a clinically useful biomarker of sepsis in premature infants, and raise a note of caution about factors which may confound the use of carbon monoxide as a clinical biomarker for other disease processes such as hemolysis.