End tidal carbon monoxide concentration in childhood haemolytic disorders

Neonatal hemolysis and risk of bilirubin-induced neurologic dysfunction

The pathologic phenotype of severe hyperbilirubinemia in the newborn infant is primarily due to excessive bilirubin production and/or impaired conjugation, resulting in an increased bilirubin load. This may, in turn, increase an infant's risk for the development of bilirubin-induced neurologic dysfunction (BIND). The highest-risk infants are those with increased bilirubin production rates due to hemolysis. Several immune and non-immune conditions have been found to cause severe hemolysis, and these are often exacerbated in those infants with perinatal sepsis and genetic predispositions. Therefore, identification of these infants, with novel technologies, is paramount in reducing the incidence of BIND and the long-term neurologic sequelae for these at-risk infants.

Elevated exhaled carbon monoxide concentration in hemoglobinopathies and its relation to red blood cell transfusion therapy

In this study, the authors examined a possible role of measurements of end-tidal carbon monoxide (CO), corrected for inhaled CO (ETCOc), as a noninvasive screening tool for hemoglobinopathies and as an indicator for when transfusions would be required in patients receiving chronic transfusions. ETCOc measurements were obtained in subjects with sickle cell disease (n = 18), thalassemia (n = 21), and healthy controls (n = 62). ETCOc values less than 3 parts per million (ppm) yielded a positive predictive value of 93% and negative predictive value of 94% in identifying hemoglobinopathies. Subsequently, 7 subjects with thalassemia had laboratory parameters and ETCOc measured over 2 transfusion cycles. ETCOc values were 4.90 +/- 0.32 ppm (mean +/- SD), with 89% of values being above normal (>or=3 ppm). Pretransfusion ETCOc levels significantly correlated with pretransfusion reticulocyte count (r = .96, P <.001), but not with pretransfusion hemoglobin (r = .44, P = .16) or pretransfusion soluble transferrin receptors (sTfR, r = .52, P = .10). In conclusion, we found that patients with hemoglobinopathies have ETCOc values above the range for healthy controls and ETCOc measurements can be used as an adjunct to hemoglobin measurements to determine the proper timing of transfusions.

Myocardial cytochrome oxidase activity is decreased following carbon monoxide exposure

Carbon monoxide (CO) inhalation often leads to cardiac dysfunction, dysrhythmias, ischemia, infarction, and death. However, the underlying mechanism of CO toxicity is poorly understood. We hypothesize that inhaled CO interrupts myocardial oxidative phosphorylation by decreasing the activity of myocardial cytochrome oxidase (CcOX), the terminal oxidase of the electron transport chain. Male C57Bl6 mice were exposed to either 1000 ppm (0.1%) CO or air for 3 h. Cardiac ventricles were harvested and mitochondria were isolated. CcOX kinetics and heme aa(3) content were measured. V(max), K(m), and turnover number were determined. Levels of CcOX subunit I message and protein were evaluated. Carboxyhemoglobin (COHb) levels were measured and tissue hypoxia was assessed with immunohistochemistry for pimonidazole hydrochloride. CO significantly decreased myocardial CcOX activity and V(max) without altering K(m). Heme aa(3) content and CcOX I protein levels significantly decreased following CO exposure while enzyme turnover number and CcOX I mRNA levels remained unchanged. CO exposure increased COHb levels without evidence of tissue hypoxia as compared to sham and hypoxic controls. Decreased CcOX activity following CO inhalation was likely due to decreased heme aa(3) and CcOX subunit I content. Importantly, myocardial CcOX impairment could underlie CO induced cardiac dysfunction.

Exhaled carbon monoxide levels in children with sickle cell disease

It is important to measure the rate of haemolysis in patients with sickle cell disease (SCD) to identify aplastic crises and indirectly assess the rate of vaso-occlusion and sequestration. The aim of this study was to assess whether end-tidal carbon monoxide (ETCOc) levels in children with sickle cell disease (SCD) could be measured reproducibly, reflected haemolysis and whether they were elevated compared to those of similarly aged, ethnic matched children without SCD (controls). ETCOc levels were measured non-invasively in 87 SCD children (age range 2.3-17.6 years) and 26 age and ethnic origin matched healthy controls using an electro-chemical sensor. The within- and between- occasion reproducibilities were assessed in ten and 15 SCD children respectively. ETCOc levels of 15 SCD children undergoing regular transfusions were related to carboxyhaemoglobin, haemoglobin and bilirubin levels. The within and between occasions' mean intrasubject coefficients of reproducibility were 5% and 18% respectively. Positive correlations were found between the ETCOc and carboxyhaemoglobin ( P =0.007) and bilirubin ( P =0.02) levels, and a significant negative correlation between the ETCOc and haemoglobin ( P =0.0002) levels. The mean and SD ETCOc levels of the SCD children (4.9 ppm; SD 1.7 ppm) were significantly higher than that of the controls (mean 1.3 ppm; SD 0.4 ppm) (difference between means 3.60; 95% C.I. 2.93-4.28; P <0.0001).

CONCLUSION

These results suggest that measurement of end-tidal carbon monoxide levels is a reliable and useful method to monitor haemolysis in children with sickle cell disease.

End tidal carbon monoxide levels are lower in women with gestational hypertension and pre-eclampsia

BACKGROUND

The possible role of heme oxygenase and its byproduct carbon monoxide (CO) in the regulation of blood pressure is under investigation. The aim of this study was to compare end tidal breath CO (ETCO) levels in women with gestational hypertension (GH) or pre-eclampsia to the levels in healthy pregnant and nonpregnant women.

MATERIALS AND METHODS

We prospectively performed ETCO measurements corrected for ambient CO (ETCOc) in two medical centers (Stanford, CA and Cleveland, OH). A Natus CO-Stat End Tidal Breath Analyzer (Natus Medical Inc., San Carlos, CA) was used. The study group included a convenience sample of 31 women with GH/pre-eclampsia (PE). Control groups included 46 nonpregnant healthy women, 44 first-trimester and 48 third-trimester pregnant healthy women.

RESULTS

Mean+/-SD ETCOc measurements were significantly lower in the GH/PE group compared to first-trimester (p=0.004) and third-trimester (p=0.001) normotensive pregnant and nonpregnant women (p=0.002) (1.36+/-0.30 vs 1.76+/-0.47, 1.72+/-0.42 and 1.78+/-0.54 ppm, respectively). The ETCOc values were < or =1.6 ppm in 89% of GH/PE women compared with, respectively, only 45, 54, and 46% of nonpregnant, first- and third-trimester normotensive pregnant women (p<0.05). ETCO measurements were not influenced by maternal age, parity, ethnicity, body mass index, gestational age or presence of household smokers. In the two centers, the controls had a similar mean ETCOc and the differences found remained significant when results for each center were analyzed separately.

CONCLUSIONS

ETCOc levels were found to be significantly lower in women with GH/PE. Further investigation is required to determine if the lower CO levels reflect a deficient compensatory response to the increase in blood pressure or whether these are primary changes of significance to our understanding of the pathogenesis of GH/PE.