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At least 19 recordsLinked to original sources

Carboxyhemoglobin concentrations in flash fire victims: report of six simultaneous fire fatalities without elevated carboxyhemoglobin.

Eight people died in a traffic accident involving a tractor-trailer and ten autos. The accident caused a series of flash fires from ruptured gas tanks. Complete autopsies established that six of the victims died exclusively from thermal trauma; none showed an elevated blood carboxyhemoglobin concentration. Flash fire victims are exceptions to the axiom that elevation of blood carboxyhemoglobin is a sine qua non for concluding that a decedent recovered from the scene of a conflagration was alive in the fire.

Accidents, Traffic↗

Production of arrhythmias by elevated carboxyhemoglobin in patients with coronary artery disease.

OBJECTIVE: To assess the effects of exposure to 4% and 6% carboxyhemoglobin on ventricular arrhythmias in patients with coronary artery disease. DESIGN: Randomized, double-blind, crossover design. SETTING: Exercise laboratory with an environmentally controlled exposure. PATIENTS: Forty-one nonsmokers with documented coronary artery disease. INTERVENTION: On day 1, a training session with no exposure, the baseline carboxyhemoglobin level was measured, and a supine bicycle exercise test was done. On days 2 to 4, patients were exposed to room air, 100 ppm carbon monoxide (target, 4% carboxyhemoglobin) or 200 ppm carbon monoxide (target, 6% carboxyhemoglobin), and they then did supine bicycle exercise with radionuclide ventriculography. Ambulatory electrocardiogram recordings were made during the 4 consecutive days to determine the frequency of ventricular premature depolarization (VPD) at various intervals. MEASUREMENTS AND MAIN RESULTS: The frequency of single VPD/h was significantly greater on the 6% carboxyhemoglobin day than on the room air day during the exercise period (167.72 +/- 37.99 for 6% carboxyhemoglobin compared with 127.32 +/- 28.22 for room air, P = 0.03). During exercise, the frequency of multiple VPD/h was greater on the 6% carboxyhemoglobin day compared with room air (9.59 +/- 3.70 on the 6% carboxyhemoglobin compared with 3.18 +/- 1.67 on room air, P = 0.02). Patients who developed increased single VPD during exercise on the 6% carboxyhemoglobin day were significantly older than those who had no increased arrhythmia, whereas patients who developed complex arrhythmias were also older and, in addition, exercised longer and had a higher peak workload during exercise. CONCLUSION: The number and complexity of ventricular arrhythmias increases significantly during exercise after carbon monoxide exposure producing 6% carboxyhemoglobin compared with room air but not after exposure producing 4% carboxyhemoglobin.

Age Factors↗

A study on house fire victims: age, carboxyhemoglobin, hydrogen cyanide and hemolysis.

Correlation among age, concentrations of carboxyhemoglobin and hydrogen cyanide, oxygen density and hemolysis were studied in 120 house fire victims. Victims aged over 60 years comprised approximately 50% of the pooled subjects. Blood samples were mainly collected from the left ventricle, but sometimes from both the right and left ventricles. The concentration of carboxyhemoglobin ranged from 1-95%, of which 71 persons (59.7%) died with carboxyhemoglobin concentrations below 60%. Carboxyhemoglobin concentrations below 10% were found in 9 persons (7.5%). Most of these cases involved the elderly persons. In this paper, we report on the death of elderly victims as a result of low carboxyhemoglobin concentrations. A significant correlation of blood carboxyhemoglobin concentrations existed between the right and left ventricles. The concentration of carboxyhemoglobin in the left ventricle was significantly higher than that in the right. Two out of 31 victims whose hydrogen cyanide concentrations were determined, succumbed to hydrogen cyanide poisoning, having a high concentration of hydrogen cyanide and a low concentration of carboxyhemoglobin. On analysis, oxygen density was found to be low in 13 persons. A negative correlation was shown between carboxyhemoglobin concentration and hemolysis. Inasmuch as hemolysis may indicate the extent of heat dissociation, hemolysis should provide an index of carbon monoxide dissociation from carboxyhemoglobin. In the present study of victims, possible causes of death i.e., carbon monoxide gas poisoning, hydrogen cyanide poisoning, oxygen deprivation, burning, shock due to burns and others were estimated. The survival time for elderly victims was considered to be short.

Adolescent↗

Effects of 4 percent and 6 percent carboxyhemoglobin on arrhythmia production in patients with coronary artery disease.

In this study, we assessed the effects of exposure to 4 percent and 6 percent carboxyhemoglobin on ventricular arrhythmias in 41 subjects (nonsmokers) with documented coronary artery disease. We used a randomized, double-blind, crossover design. On day 1, a training session with no exposure, the baseline carboxyhemoglobin level was measured, and a supine bicycle exercise test was done. On days 2 through 4, subjects were exposed to room air, 100 parts per million (ppm)2 carbon monoxide (target, 4 percent blood carboxyhemoglobin), or 200 ppm carbon monoxide (target, 6 percent blood carboxyhemoglobin), and they then did a supine bicycle exercise test. Radionuclide ventriculography was performed at rest and during exercise. Ambulatory electrocardiogram recordings were made during the four consecutive days to determine the frequency of premature ventricular contractions at various intervals. The frequency of single premature ventricular contractions per hour during exercise was significantly greater on the 6 percent carboxyhemoglobin day than on the room air day (167.72 +/- 37.99 for 6 percent carboxyhemoglobin compared with 127.32 +/- 28.22 for room air, p = 0.03). The frequency of multiple premature ventricular contractions per hour was also significantly greater during exercise on the 6 percent carboxyhemoglobin day compared with the room air day (9.59 +/- 3.70 for the 6 percent carboxyhemoglobin day compared with 3.18 +/- 1.67 for the room air day, p = 0.02). Patients who developed increased arrhythmias during exercise on the 6 percent carboxyhemoglobin day were significantly older than those who had no increased arrhythmia, and, in addition, exercised longer and had a higher peak workload during exercise. No effect of carbon monoxide exposure was seen on the 4 percent carboxyhemoglobin day.

Aged↗

Effect of carboxyhemoglobin on the accuracy of mixed venous oximetry monitors in dogs.

OBJECTIVE: To assess the accuracy of mixed venous hemoglobin oxygen saturation estimated, using in vivo pulmonary artery reflectance oximetry with ranging concentrations of carboxyhemoglobin. DESIGN: Criterion standard, a comparison of an alternative test to the "gold standard." SETTING: Laboratory animal facility of a large university. SUBJECTS: Five mongrel dogs. INTERVENTIONS: Anesthetized dogs were mechanically ventilated to normocarbia and instrumented with arterial catheters and pulmonary artery oximetry catheters. The dogs were ventilated with increasing inspired concentrations of carbon monoxide, and blood samples were analyzed for fractional concentrations of oxyhemoglobin and carboxyhemoglobin. Carboxyhemoglobin levels ranged from 0% to 70%. At each level of carboxyhemoglobin, FIO2 was varied from 0.21 to 0.09. Co-oximeter readings were compared with mixed venous oxygen saturation measurements of the pulmonary artery oximetry catheter. MEASUREMENTS AND MAIN RESULTS: Mixed venous oxygen saturation measurements from the pulmonary artery oximetry catheter system progressively overestimated fractional oxyhemoglobin in the presence of carboxyhemoglobin. This catheter's mixed venous oxygen saturation reading could be corrected for the presence of carboxyhemoglobin by a derived formula. Regression analysis for corrected mixed venous oxygen saturation (calculated) vs. fractional oxyhemoglobin yields a slope and intercept of 0.98 and -1.01, respectively, with a correlation coefficient of .98. The bias and precision values for fractional oxyhemoglobin vs. mixed venous oxygen saturation (calculated) are 1.9 and 2.2 (n = 66), with bias representing the degree of systematic error or deviation from the true measurement, and precision representing the confidence limits (or standard deviation) for individual variations from the true measurement. CONCLUSIONS: Mixed venous oxygen saturation monitoring does not detect the presence of carboxyhemoglobin and progressively overestimates fractional oxyhemoglobin as carboxyhemoglobin increases. Mixed venous oxygen saturation values of the standard pulmonary artery oximetry catheter approximately equal functional hemoglobin saturation. Bench co-oximeter blood analysis is required in patients suspected of having increased carboxyhemoglobin levels.

Algorithms↗

[Carboxyhemoglobin levels and risk factors of carbon monoxide poisoning in children;].

BACKGROUND: To determine carboxyhemoglobin levels and to investigate carbon monoxide poisoning risk in children. PATIENTS AND METHODS: We determine carboxyhemoglobin blood levels by cooximetry in 65 children, between 15 days and 15 years attended in a pediatric emergency section. We analyze carbon monoxide risk factors (type of heating and smokers in the family). RESULTS: Mean carboxyhemoglobin levels in 59 children without acute intoxication was 0.5 +/- 0.87% (range 0-3.8%). There are no significant differences with respect to age and sex. Children with wood or coal heating (0.88 +/- 1.34%) and gas heating (0.58 +/- 0.97%) have carboxyhemoglobin levels higher than children with electric heating (0.28 +/- 0.4%) but differences were no statistically significant. Four patients have carboxyhemoglobin levels > 2%, two with coal or wood hating and two with gas heating. Children with smokers in the family have carboxyhemoglobin levels higher than the rest of children (0.65 +/- 1.05% versus 0.34 +/- 0.45%) without statistical significance. The four children with carboxyhemoglobin levels > 2% live with smokers. Six children suffered carbon monoxide poisoning with carboxyhemoglobin levels between 20.6 and 36.6%. CONCLUSIONS: Mean carboxyhemoglobin levels in children are low. There are carbon monoxide poisoning risk factors (wood, coal or gas heating at home, and smokers in the family) in a high percentage of the children, although they did not show statistical significance.

Adolescent↗

Observed versus predicted carboxyhemoglobin levels in cellulose triacetate workers exposed to methylene chloride.

BACKGROUND: Occupational exposure to methylene chloride, together with carboxyhemoglobin concentrations, has not been studied previously. METHODS: Carboxyhemoglobin levels were measured in non-smoking employees exposed to varying concentrations of methylene chloride during the manufacture of cellulose triacetate fibers. The observed carboxyhemoglobin levels were compared to predicted concentrations using a pharmacokinetic model. RESULTS: The presence of carboxyhemoglobin in non-smokers exposed to methylene chloride results primarily from the metabolism of methylene chloride in the liver and exhibits a linear dose-response relationship. The observed levels of carboxyhemoglobin in non-smokers at the end of an 8-hour shift depend upon exposures to methylene chloride that day but are independent of occupational exposures on previous days. The observed daily concentrations of carboxyhemoglobin are consistent with predicted concentrations using a pharmacokinetic model. While varying exposure patterns were shown to change the rate of metabolite formation at the end of shift, these same exposure patterns had almost no effect on the total amount of carbon monoxide in the blood. CONCLUSION: While the present study addresses the relationship between methylene chloride, carbon monoxide, carboxyhemoglobin and ischemic heart disease, it does not address the issue of tumorigenicity, which is also the basis for the current U.S. Occupational Health and Safety workplace exposure limit of 25 ppm. This study provides support for the conclusion that the current American Conference of Governmental Industrial Hygienists 8-hour Threshold Limit Value of 50 ppm adequately protects human health with regard to ischemic heart disease and carboxyhemoglobin formation among non-smokers.

Carbon Monoxide↗

Arterio-venous carboxyhemoglobin difference suggests carbon monoxide production by human lungs.

Carbon monoxide is hypothesized to be produced by the enzyme heme oxygenase predominantly in liver and spleen, bound to hemoglobin, and excreted by the lungs. Thus, venous carboxyhemoglobin is expected to be higher or equal to arterial carboxyhemoglobin. Unspecific inflammatory stimuli have been shown to induce heme oxygenase in lung tissue possibly leading to pulmonary carbon monoxide production. Arterial and central venous carboxyhemoglobin levels were measured in critically ill patients on the third day of ICU stay (n = 59) as well as in otherwise healthy humans prior to orthopedic surgery (n = 29). Arterial and central venous carboxyhemoglobin were higher in ICU patients than in healthy humans, respectively. In both groups, arterial carboxyhemoglobin was significantly higher than central venous carboxyhemoglobin. The arteriovenous carboxyhemoglobin differences were similar in both groups. The data suggest (a) increased CO-generation in critical illness and (b) pulmonary CO-production in healthy and critically ill humans.

Arteries↗

Effect of maternal heme degradation on fetal carboxyhemoglobin concentration in pregnancy-induced hypertension.

Increased red cell destruction with consequent heme catabolism results in accumulation in carboxyhemoglobin in women with pregnancy-induced hypertension. Temporally associated with this is a significant shift in the oxyhemoglobin dissociation curve to the left. In this study we assessed the relationship between carboxyhemoglobin concentration and oxyhemoglobin dissociation curve in simultaneously obtained maternal and fetal venous blood in which patients with pregnancy-induced hypertension were compared with normotensive patients. Maternal and fetal carboxyhemoglobins were significantly higher in patients with pregnancy-induced hypertension than in control subjects. Fetal carboxyhemoglobin was significantly higher than maternal carboxyhemoglobin in both clinical groups. Furthermore, maternal and fetal oxyhemoglobin dissociation curves were significantly shifted to the left in patients with pregnancy-induced hypertension compared with controls. The fetal-maternal gradient of carboxyhemoglobin was similar in both groups. The maternal-fetal gradient of oxyhemoglobin dissociation curve position was significantly reduced in pregnancy-induced hypertension. The concentrations of carboxyhemoglobin measured do not fully explain the magnitude of the shift in oxyhemoglobin dissociation curve, but the data suggest a potential impact on fetal oxygenation in pregnancy-induced hypertension.

Carboxyhemoglobin↗

Carboxyhemoglobin levels in banked blood.

To determine the prevalence of carboxyhemoglobin levels in banked blood exceeding Air Quality Standards (level of carboxyhemoglobin greater than 1.5 percent), we analyzed banked blood for the level of carboxyhemoglobin from 101 randomly selected samples. Of 101 units of banked blood, 49 (49 percent) had carboxyhemoglobin levels greater than 1.5 percent, and 36 (36 percent) had levels of 2.0 percent or more. We suggest that it may be undesirable to use blood with increased carboxyhemoglobin content when multiple transfusions are necessary, particularly in patients with cardiac or pulmonary disease. Labeling banked blood for carboxyhemoglobin content would be useful in order to help avoid multiple or consecutive transfusions of blood with high levels of carboxyhemoglobin.

Blood Banks↗

Determination of carboxyhemoglobin in the presence of other blood hemoglobin pigments by visible spectrophotometry.

The convenience of the spectrophotometric method for the determination of carboxyhemoglobin has been tempered by the observation that the analysis of postmortem bloods is often biased by the presence of pigments other than oxyhemoglobin, carboxyhemoglobin, and reduced hemoglobin. These other pigments include most prominently methemoglobin and sulfhemoglobin. Using a microprocessor-controlled spectrophotometer, a method was developed depending on absorbance difference measurements at isosbestic points for oxyhemoglobin, carboxyhemoglobin, and reduced hemoglobin that is accurate down to 2% carboxyhemoglobin in fresh blood. A correction for the error caused by methemoglobin is part of the method. Qualitative confirmation of carboxyhemoglobin by examination of spectra details, sodium dithionite reduction, and first derivative spectra is described. The analysis of denatured and autolyzed bloods is examined in the context of postmortem case reports. A number of spectra are shown in detail, including methemoglobin, sulfhemoglobin, alkaline hematin, acid hematin, and mixtures of blood pigments containing varying concentrations of carboxyhemoglobin. The method has been shown to be precise, accurate, and reliable for fresh bloods. While accuracy for denatured bloods is diminished, reliability of carboxyhemoglobin identification is maintained. The analysis time is about 5 min for routine blood samples and the method is easily implemented with a precise microprocessor-controlled spectrophotometer.

Carboxyhemoglobin↗

Additivity of protein deficiency and carbon monoxide on placental carboxyhemoglobin in mice.

OBJECTIVES: The purpose of the study was to estimate maternal and placental carboxyhemoglobin in protein-deficient and carbon monoxide-exposed mice. STUDY DESIGN: Pregnant CD-1 mice were placed on diets containing 27% (control), 16%, 8%, or 4% protein on gestation day 1. The dams were exposed to carbon monoxide concentrations of 0 (control), 65, 125, 250, or 500 ppm from gestation days 8 to 18. The dams were killed on gestation day 18, and blood samples were collected from the maternal hearts and placentas for carboxyhemoglobin determination. RESULTS: Maternal carboxyhemoglobin levels were related to the carbon monoxide exposure levels and were not affected by protein deficiency. Placental carboxyhemoglobin levels were higher than maternal carboxyhemoglobin levels, were related to carbon monoxide exposure levels, and were inversely related to dietary protein levels. CONCLUSION: The data suggest that maternal protein deficiency enhances the placental carboxyhemoglobin levels resulting from carbon monoxide exposure and exacerbates hypoxic conditions for the developing fetus. Special groups at risk may include drug abusers and cigarette or marijuana smokers.

Animals↗

Carboxyhemoglobin levels in patients with flu-like symptoms.

Subacute carbon monoxide poisoning is commonly misdiagnosed as an influenza-like viral illness. All patients presenting to the triage nurse at University Hospital with flu-like symptoms during February 1985 were asked to give blood samples for carboxyhemoglobin determination. Fifty-five patients (10% of those eligible) with headache, dizziness, nausea, vomiting, diarrhea, weakness, general malaise, or shortness of breath were enrolled in the study. Carboxyhemoglobin levels ranged from 0 to 21%. Thirteen patients (23.6%) of this self-selected subgroup had carboxyhemoglobin levels greater than or equal to 10%. There was no statistically significant difference in carboxyhemoglobin levels between smokers and nonsmokers. More patients using wood heat had elevated carboxyhemoglobin levels than patients using any other form of heating (P less than .05). No patient with a carboxyhemoglobin level greater than or equal to 10% was diagnosed as having subacute CO poisoning by emergency physicians. Physicians must seek out the possibility of CO toxicity in patients with flu-like illness, particularly in inner-city populations during the heating months. Fundoscopy and COHb levels may be useful in selected cases to correctly diagnose patients and avoid a return to a hazardous environment with potentially fatal consequences.

Adolescent↗

High carboxyhemoglobin concentrations occur in swine during desflurane anesthesia in the presence of partially dried carbon dioxide absorbents.

BACKGROUND: Increased carboxyhemoglobin concentrations in patients receiving inhalation anesthetics (desflurane, enflurane, and isoflurane) have been reported. Recent in vitro studies suggest that dry carbon dioxide absorbents may allow the production of carbon monoxide. METHODS: The authors used high fresh oxygen flow (5 or 10 l/min) through a conventional circle breathing system of an anesthesia machine for 24 or 48 h to produce absorbent drying. Initial studies used 10 l/min oxygen flow with the reservoir bag removed or with the reservoir bag left in place during absorbent drying (this increases resistance to gas flow through the canister). A third investigation evaluated a lower flow rate (5 l/min) for absorbent drying. Water content of the absorbent and temperature were measured. Pigs received a 1.0 (human) minimum alveolar concentration desflurane anesthetic (7.5%) for 240 min using a 1 l/min oxygen flow rate with dried absorbent. Carbon monoxide concentrations in the circuit and carboxyhemoglobin concentrations in the pigs were measured. RESULTS: Pigs anesthetized with desflurane using Baralyme exposed to 48 h of 10 l/min oxygen flow (reservoir bag removed) had extremely high carboxyhemoglobin concentrations (more than 80%). Circuit carbon monoxide concentrations during desflurane anesthesia using absorbents exposed to 10 l/min oxygen flow (reservoir bag removed, 24 h) reached peak values of 8,800 to 13,600 ppm, depending on the absorbent used. Carboxyhemoglobin concentrations reached peak values of 73% (Baralyme) and 53% (soda lime). The water content of Baralyme decreased from 12.1 +/- 0.3% (mean +/- SEM) to as low as 1.9 +/- 0.4% at the bottom of the lower canister (oxygen flow direction during drying was from bottom to top). Absorbent temperatures in the bottom canister increased to temperatures as high as 50 degrees C. With the reservoir bag in place during drying (10 l/min oxygen flow), water removal from Baralyme was insufficient to produce carbon monoxide (lowest water content = 5.5%). Use of 5 l/min oxygen flow (reservoir bag removed) for 24 h did not reduce water content sufficiently to produce carbon dioxide with desflurane. CONCLUSIONS: An oxygen flow rate of 10 l/min for 24 h in a conventional anesthesia circuit can dry carbon dioxide absorbents sufficiently to produce extremely high levels of carbon monoxide with high carboxyhemoglobin concentrations in desflurane-anesthetized pigs. When the reservoir bag is in place on the anesthesia machine or when a lower oxygen flow rate (5 l/min) is used, carbon dioxide absorbent drying still occurs, but 24-48-h exposure time is insufficient to allow for carbon monoxide production with desflurane.

Adsorption↗

Human carboxyhemoglobin at 2.2 A resolution: structure and solvent comparisons of R-state, R2-state and T-state hemoglobins.

The three-dimensional structure and associated solvent of human carboxyhemoglobin at 2.2 A resolution are compared with other R-state and T-state human hemoglobin structures. The crystal form is isomorphous with that of the 2.7 A structure of carboxyhemoglobin reported earlier [Baldwin (1980). J. Mol. Biol. 136, 103-128], whose coordinates were used as a starting model, and with the 2.2 A structure described in an earlier report [Derewenda et al. (1990). J. Mol. Biol. 211, 515-519]. During the course of the refinement, a natural mutation of the alpha-subunit, A53S, was discovered that forms a new crystal contact through a bridging water molecule. The protein structure shows a significant difference between the alpha and beta heme geometries, with Fe-C-O angles of 125 and 162 degrees, respectively. The carboxyhemoglobin is compared with other fully ligated R-state human hemoglobins [Baldwin (1980). J. Mol. Biol. 136, 103-128; Shaanan (1983). J. Mol. Biol. 195, 419-422] with the R2-state hemoglobin [Silva et al. (1992). J. Biol. Chem. 267, 17248-17256] and with T-state deoxyhemoglobin [Fronticelli et al. (1994). J. Biol. Chem. 269, 23965-23969]. The structure is similar to the earlier reported R-state structures, but there are differences in many side-chain conformations, the associated water structure and the presence and the position of a phosphate ion. The quaternary changes between the R-state carboxyhemoglobin and the R2-state and T-state structures are in general consistent with those reported in the earlier structures. The location of 238 water molecules and a phosphate ion in the carboxyhemoglobin structure allows the first comparison of the solvent structures of the R-state and T-state structures. Distinctive hydration patterns for each of the quaternary structures are observed, but a number of conserved water molecule binding sites are found that are independent of the conformational state of the protein.

Carboxyhemoglobin↗

Carboxyhemoglobin levels in primary and secondary cigar and pipe smokers.

This study of 130 subjects was performed to obtain more data about the smoking habits and levels of carboxyhemoglobin in various types of pipe and cigar smokers. These smokers may be divided by history into primary or secondary smokers and also into current inhalers and noninhalers. Prior studies of carboxyhemoglobin levels have yielded conflicting results, presumably due to differences in current habits of inhalation, which were often not taken into account. Cigarette, primary pipe, and secondary pipe inhalers had similar carboxyhemoglobin levels that were significantly higher than nonsmokers (5.6, 5.0, 5.4, and 1.0 percent, respectively). Cigar inhalers had markedly elevated concentrations of carboxyhemoglobin (13.8 and 11.8 percent in primary and secondary inhalers, respectively). Most secondary cigar and pipe smokers inhaled, whereas most primary smokers did not. Intentional inhalation, rather than past smoking history, is the most important factor in determining the carboxyhemoglobin level for each type of smoke.

Blood Gas Analysis↗

Discrepancies between self-reported smoking and carboxyhemoglobin: an analysis of the second national health and nutrition survey.

Environmental, self-report, and demographic factors mediated the relationship between self-reported cigarette smoking and carboxyhemoglobin among 2114 smokers and 3918 nonsmokers. Self-reported nonsmokers with carboxyhemoglobin levels between 2% and 3% were more likely to be self-reported ex-smokers, to live in a larger community, and to be younger, less educated, and male than were self-reported nonsmokers with carboxyhemoglobin levels of less than 2%. Self-reported nonsmokers with strong evidence of cigarette consumption (carboxyhemoglobin level greater than 3%) were more likely to be self-reported ex-smokers, younger, less educated, and non-White than were nonsmokers with carboxyhemoglobin levels of less than 2%.

Adolescent↗

Increased levels of carboxyhemoglobin and serum iron as an indicator of increased red cell turnover in preeclampsia.

Patients with severe preeclampsia are reported to have microangiopathic hemolytic anemia. This study demonstrates that increased red cell turnover with heme catabolism is also common in mild preeclampsia. Heme catabolism results in equimolar production of carboxyhemoglobin, iron, and bilirubin. A concomitant rise in these constituents of venous blood would support this hypothesis. Patients with antepartum preeclampsia had mean carboxyhemoglobin concentrations (2.72% total hemoglobin) greater than those of control patients (0.65%) (p less than 0.001) and serum iron concentrations (98.5 micrograms/dl) greater than those of control patients (66.1 micrograms/dl) (p less than 0.01). Bilirubin concentrations were not different. Post partum, carboxyhemoglobin and iron concentrations returned toward normal (1.38% and 50.2 micrograms/dl, respectively). Disparity in the magnitude of increase of heme catabolites produced in equimolar proportion is explained by differences in the kinetics of clearance. The data are most consistent with increased destruction of maternal red cells, even in mild preeclampsia. Potential implications of elevated carboxyhemoglobin on maternal and fetal oxygenation are discussed.

Carboxyhemoglobin↗