Arterial carboxyhaemoglobin levels in children admitted to PICU: A retrospective observational study

Association of carboxyhemoglobin and methemoglobin levels with hemolysis during extracorporeal membrane oxygenation

INTRODUCTION

Hemolysis, characterized by increased carboxyhemoglobin (COHb) and methemoglobin (MetHb) levels, is a complication of extracorporeal membrane oxygenation (ECMO).

METHODS

This prospective single-center study aimed to investigate the correlation between COHb and MetHb levels and hemolysis during ECMO. This study included 32 patients requiring ECMO for circulatory or respiratory failure. Plasma-free hemoglobin (pfHb), COHb, and MetHb levels were measured simultaneously within 6 h of ECMO induction, daily during ECMO, within 6 h after decannulation, and 2 days after decannulation unless death occurred before. Patients were classified into hemolysis and non-hemolysis groups based on whether the maximum pfHb level during ECMO was ⩾50 mg/dL.

RESULTS

No significant difference in maximum COHb levels during ECMO (COHbECMO) was observed between the hemolysis and non-hemolysis groups (2.15% [interquartile range (IQR) = 1.83, 2.60] vs 1.65% [IQR = 1.40, 2.10], p = 0.159). However, maximum MetHb levels during ECMO (MetHbECMO) were significantly higher in the hemolysis group (1.35% [IQR = 1.12, 1.78] vs 1.10% [IQR = 0.90, 1.37], p = 0.045). The Spearman's correlation coefficients for COHbECMO and MetHbECMO were 0.39 (95% confidence interval [CI] = 0.456-0.649) and 0.66 (95% CI = 0.404-0.820), respectively.

CONCLUSION

Elevated MetHb levels in patients undergoing ECMO may be associated with hemolysis.

Carboxyhemoglobin predicts oxygenator performance and imminent oxygenator change in extracorporeal membrane oxygenation

BACKGROUND

The continuous exposure of blood to a non-biological surface during extracorporeal membrane oxygenation (ECMO) may lead to progressive thrombus formation in the oxygenator, hemolysis and consequently impaired gas exchange. In most centers oxygenator performance is monitored only on a once daily basis. Carboxyhemoglobin (COHb) is generated upon red cell lysis and is routinely measured with any co-oximetry performed to surveille gas exchange and acid-base homeostasis every couple of hours. This retrospective cohort study aims to evaluate COHb in the arterial blood gas as a novel marker of oxygenator dysfunction and its predictive value for imminent oxygenator change.

RESULTS

Out of the 484 screened patients on ECMO 89, cumulatively requiring 116 oxygenator changes within 1833 patient days, including 19,692 arterial COHb measurements were analyzed. Higher COHb levels were associated with lower post-oxygenator pO2 (estimate for log(COHb): - 2.176 [95% CI - 2.927, - 1.427], p < 0.0001) and with a shorter time to oxygenator change (estimate for log(COHb): - 67.895 [95% CI - 74.209, - 61.542] hours, p < 0.0001). COHb was predictive of oxygenator change within 6 h (estimate for log(COHb): 5.027 [95% CI 1.670, 15.126], p = 0.004).

CONCLUSION

COHb correlates with oxygenator performance and can be predictive of imminent oxygenator change. Therefore, longitudinal measurements of COHb in clinical routine might be a cheap and more granular candidate for ECMO surveillance that should be further analyzed in a controlled prospective trial design.

Carboxyhaemoglobin levels in infants with hypoxic ischaemic encephalopathy

OBJECTIVES

Hypoxic ischaemic encephalopathy (HIE) is associated with oxidative stress. A potential marker of oxidative damage is carboxyhaemoglobin (COHb) which is the product of the reaction between carbon monoxide and haemoglobin and is routinely assessed on blood gas analysis. Our objective was to test the hypothesis that higher COHb levels would be associated with worse outcomes in infants treated for HIE.

METHODS

A retrospective, observational study was performed of all infants who received whole body hypothermia for HIE at a tertiary neonatal intensive care unit between January 2018 and August 2021. For each participating infant, the highest COHb level per day was recorded for days one, three and five after birth.

RESULTS

During the study period, 67 infants with a median (IQR) gestational age of 40 (38-41) weeks underwent therapeutic hypothermia for HIE. The median (IQR) COHb level on day three was higher in infants without electroencephalographic seizures (1.4 [1.1-1.4] %) compared with infants with seizures (1.1 [0.9-1.3] %, p=0.024). The median (IQR) COHb on day five was higher in infants without MRI brain abnormalities (1.4 [1.2-1.7] %) compared with infants with MRI abnormalities (1.2 [1.0-1.4] %, p=0.032). The COHb level was not significantly different between the nine infants who died compared to the infants who survived.

CONCLUSIONS

COHb levels were higher in infants with HIE without seizures and in those with normal MRI brain examinations. We suggest that carbon monoxide has a potential protective role in HIE.

Carboxyhemoglobin as biomarker of late-onset sepsis in preterm infants

Carboxyhemoglobin (COHb) is considered a biomarker of oxidative stress and previous studies reported an increase in COHb levels in preterm infants who develop late-onset sepsis (LOS). Our aim was to assess the correlation between COHb levels and the risk for LOS development. We retrospectively studied 100 preterm infants, 50 in the LOS and 50 in the no LOS group. COHb levels were measured on the day of diagnosis of the first episode of LOS, 3, 2, and 1 days before and 1 and 4 days after the onset of LOS. Logistic regression analysis showed that a higher level of COHb 2 days before the diagnosis of LOS increases the risk for LOS development (OR 12.150, 95% Cl 1.311-12.605; P = 0.028). A COHb level of 1.55% measured 2 days before the diagnosis of LOS is the best predictive threshold for LOS with a sensitivity of 70% and a specificity of 70%.    Conclusion: Increased levels of COHb may predict the diagnosis of LOS in very preterm infants with a good accuracy. If further studies confirm our findings, this easy-to-measure biomarker could provide neonatologists with another tool for monitoring and early diagnosis of sepsis in high-risk patients. What is Known: • Carboxyhemoglobin (COHb) is a biomarker of oxidative stress. • Previous studies reported an increase in COHb levels in preterm infants who develop late-onset sepsis (LOS). What is New: • COHb levels increased two days before the diagnosis of LOS and this increase was associated with the risk for developing LOS. • ROC curve analysis for COHb measured two days before the diagnosis of LOS showed that 1.55% is the best predictive threshold for LOS with a sensitivity of 70% and a specificity of 70%.

Carboxyhemoglobin as biomarker of prematurity complications

BACKGROUND

Carboxyhemoglobin (COHb) is considered a biomarker of oxidative stress and previous studies suggest a correlation between its blood level and prematurity complications. Our aim in this study was to assess the correlation between COHb levels and the risk for bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH), and retinopathy of prematurity (ROP).

METHODS

We retrospectively studied 178 preterm infants with gestational age of 27.0 ± 1.5 weeks, among which 121 (68 %) had BPD, 43 (24 %) IVH, and 33 (19 %) ROP. COHb levels measured during the first seven days of life were recorded.

RESULTS

Logistic regression analysis showed that higher levels of COHb on the seventh day of life increases the risk for moderate-to-severe BPD (OR 4.552, 95 % Cl 1.220-16.997; P = 0.024), while higher levels of COHb on the fourth day of life increases the risk for grade 2-4 IVH (OR 5.537, 95 % Cl 1.602-19.134; P = 0.007).

CONCLUSIONS

COHb measured in the first week of life can contribute to predicting the risk for BPD and IVH, but not for ROP, in very preterm infants. Since COHb can be readily measured, its assessment can be useful in clinical practice for early identification of preterm infants at high risk for oxidative stress related complications.

Predictive markers related to local and systemic inflammation in severe COVID-19-associated ARDS: a prospective single-center analysis

BACKGROUND

As the COVID-19 pandemic strains healthcare systems worldwide, finding predictive markers of severe courses remains urgent. Most research so far was limited to selective questions hindering general assumptions for short- and long-term outcome.

METHODS

In this prospective single-center biomarker study, 47 blood- and 21 bronchoalveolar lavage (BAL) samples were collected from 47 COVID-19 intensive care unit (ICU) patients upon admission. Expression of inflammatory markers toll-like receptor 3 (TLR3), heme oxygenase-1 (HO-1), interleukin (IL)-6, IL-8, leukocyte counts, procalcitonin (PCT) and carboxyhemoglobin (CO-Hb) was compared to clinical course. Clinical assessment comprised acute local organ damage, acute systemic damage, mortality and outcome after 6 months.

RESULTS

PCT correlated with acute systemic damage and was the best predictor for quality of life (QoL) after 6 months (r = - 0.4647, p = 0.0338). Systemic TLR3 negatively correlated with impaired lung function (ECMO/ECLS: r = - 0.3810, p = 0.0107) and neurological short- (RASS mean: r = 0.4474, p = 0.0023) and long-term outcome (mRS after 6 m: r = - 0.3184, p = 0.0352). Systemic IL-8 correlated with impaired lung function (ECMO/ECLS: r = 0.3784, p = 0.0161) and neurological involvement (RASS mean: r = - 0.5132, p = 0.0007). IL-6 in BAL correlated better to the clinical course than systemic IL-6. Using three multivariate regression models, we describe prediction models for local and systemic damage as well as QoL. CO-Hb mean and max were associated with higher mortality.

CONCLUSIONS

Our predictive models using the combination of Charlson Comorbidity Index, sex, procalcitonin, systemic TLR3 expression and IL-6 and IL-8 in BAL were able to describe a broad range of clinically relevant outcomes in patients with severe COVID-19-associated ARDS. Using these models might proof useful in risk stratification and predicting disease course in the future. Trial registration The trial was registered with the German Clinical Trials Register (Trial-ID DRKS00021522, registered 22/04/2020).

Carboxyhemoglobin (CO-Hb) Correlates with Hemolysis and Hospital Mortality in Extracorporeal Membrane Oxygenation: A Retrospective Registry

Background: Patients supported with extracorporeal membrane oxygenation (ECMO) may develop elevated carboxyhemoglobin (CO-Hb), a finding described in the context of hemolysis. Clinical relevance of elevated CO-Hb in ECMO is unclear. We therefore investigated the prognostic relevance of CO-Hb during ECMO support. Methods: Data derives from a retrospective single-center registry study. All ECMO patients in a medical ICU from October 2010 through December 2019 were considered. Peak arterial CO-Hb value during ECMO support and median CO-Hb values determined by point-of-care testing for distinct time intervals were determined. Groups were divided by CO-Hb (<2% or ≥2%). The primary endpoint was hospital survival. Results: A total of 729 patients with 59,694 CO-Hb values met the inclusion criteria. Median age (IQR) was 59 (48−68) years, 221/729 (30.3%) were female, and 278/729 (38.1%) survived until hospital discharge. Initial ECMO configuration was veno-arterial in 431/729 (59.1%) patients and veno-venous in 298/729 (40.9%) patients. Markers for hemolysis (lactate dehydrogenase, bilirubin, hemolysis index, and haptoglobin) all correlated significantly with higher CO-Hb (p < 0.001, respectively). Hospital survival was significantly higher in patients with CO-Hb < 2% compared to CO-Hb ≥ 2%, evaluating time periods 24−48 h (48.6% vs. 35.2%, p = 0.003), 48−72 h (51.5% vs. 36.8%, p = 0.003), or >72 h (56.9% vs. 31.1%, p < 0.001) after ECMO cannulation. Peak CO-Hb was independently associated with lower hospital survival after adjustment for confounders. Conclusions: In ECMO, CO-Hb correlates with hemolysis and hospital survival. If high CO-Hb measured should trigger a therapeutic intervention in order to reduce hemolysis has to be investigated in prospective trials.

Retrospective evaluation of carboxyhemoglobin and methemoglobin levels in dogs and cats with respiratory disease

OBJECTIVE

To evaluate carboxyhemoglobin (COHb) and methemoglobin (MetHb) levels in dogs and cats with respiratory disease in the ICU.

DESIGN

Retrospective study.

SETTING

University veterinary teaching hospital.

ANIMALS

The ICU census was searched for dogs (n = 466) and cats (n = 97) hospitalized within the ICU between January 2016 and January 2019 in whom blood gas with co-oximetry was performed. Dogs and cats were stratified into those with primary respiratory and nonrespiratory categories; the underlying cause of the disease was also noted. Venous blood gas, co-oximeter, PaO₂ /FiO₂ (PF ratio), physical examination findings, and outcome were recorded.

MEASUREMENTS AND MAIN RESULTS

The median COHb and MetHb in dogs hospitalized in the ICU were 2.6% (0.1%-5.6%) and 1.1% (0.1%-2.9%), respectively. The median COHb and MetHb in cats hospitalized in the ICU were 2.2% (0.1%-5.4%) and 1.0% (0%-2.1%), respectively. Dogs with respiratory disease had a higher COHb than dogs without respiratory disease (median, 2.7% [range, 0.3%-5.0%] vs. 2.5% [0.1%-5.6%]; P = 0.0148). COHb was positively associated with survival in cats (median, 2.2% [range, 0.1%-5.4%] vs. 1.9% [0.1%-3.9%]; P = 0.0433). Both COHb and MetHb were higher in septic dogs than in nonseptic dogs (median COHb, 2.8% [range 0.3%-4.5%] vs. 2.6% [0.1%-5.6%]; P = 0.02 and median MetHb, 1.1% [0.1%-2.9%] vs. 1.1% [0.1%-2.4%]; P = 0.01, respectively).

CONCLUSIONS

There may be a positive association between COHb and respiratory disease in dogs; prospective studies are needed to evaluate this further. No association between COHb and respiratory disease in cats or MetHb and respiratory disease in either species was detected. Additional prospective studies are needed to determine whether COHb and MetHb are biomarkers for sepsis in dogs and whether COHb is an indicator of mortality in cats.

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.

Carboxyhemoglobin levels in children during extracorporeal membrane oxygenation support: a retrospective study

INTRODUCTION

Hemolysis is a common complication of extracorporeal membrane oxygenation (ECMO). There are few data on whether carboxyhemoglobin (COHb), a potential marker of hemolysis, are elevated during ECMO support.

METHODS

We conducted a single-center, retrospective study comparing peak COHb levels of children pre-, during, and post-ECMO from January 2017 to August 2020.

RESULTS

There were 154 ECMO runs in 147 children (154 PICU admissions) included in the study. The median age was 3.5 (IQR 0.2, 39.2) months. Veno-arterial ECMO was the predominant mode: 146/154 (94.8%). Eighty-seven children (56.5%) underwent cardiac surgery. Peak COHb levels during ECMO were statistically significantly higher compared to pre ECMO (COHb 1.8% (IQR 1.4, 2.6) vs COHb 1.2% (IQR 0.7, 1.7), p < 0.001) and post ECMO (COHb 1.6% (IQR 1.3, 2.2), p = 0.009). Children with COHb ⩾2% were younger and had longer duration of ECMO support. Plasma hemoglobin weakly correlated with COHb level (r = 0.14; p = 0.04).

CONCLUSIONS

Carboxyhemoglobin levels increased during ECMO support compared to the pre and post ECMO period. Younger age and longer ECMO duration were associated with COHb levels ⩾2%. Plasma hemoglobin weakly correlated with COHb level.