The correlation of carboxyhemoglobin levels between venous and arterial blood gas samples

Abstract

Study objectives: In suspected carbon monoxide poisoning, carboxyhemoglobin levels are commonly obtained from arterial blood gas samplings. Arterial puncture is associated with increased risks (ie, hematoma, thrombosis, pseudoaneurysm) and is more painful compared with venipuncture. This study assesses the reliability of carboxyhemoglobin levels obtained by venous blood gas sampling compared with arterial blood gas samplings. Methods: A cross-sectional study of 98 patients in the emergency department of an urban, inner-city hospital was performed. Paired samples of arterial and venous blood were obtained within a 15-minute interval. Arteriovenous differences were analyzed for multiple variables (ie, Na, K, hemoglobin, glucose, and lactate), including carboxyhemoglobin. Statistical analysis was performed using a paired sample t test, and Pearson correlation coefficient was determined for confirmation. Results: Within the entire data set (n=98), the mean difference between arterial and venous carboxyhemoglobin levels was 0.40±0.44 ( P =.0001), with a Pearson correlation of r =0.97 ( P Conclusion: There is excellent correlation in the measurement of carboxyhemoglobin between venous and arterial blood gas samples. These data should lend support to the use of venous blood gas analysis for the determination of carboxyhemoglobin levels when arterial blood gas sampling is otherwise not required, is difficult, or is not desired by the patient. One limitation of this study, however, is the lack of carboxyhemoglobin levels in toxic ranges (ie, >20%); further prospective investigation in a population with suspected carbon monoxide poisoning is warranted.