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Relationship between venous and arterial carboxyhemoglobin levels in patients with suspected carbon monoxide
M Touger1, E J Gallagher, J Tyrell
1Department of Medicine, Bronx Municipal Hospital, Albert Einstein College of Medicine.
Study Objective:
To test the hypothesis that venous carboxyhemoglobin (V-COHb) levels accurately predict arterial (A-COHb) levels.
Design:
Prospective comparison of A-COHb and V-COHb levels in patients with suspected carbon monoxide (CO) poisoning.
Setting:
Municipal hospital emergency department with contiguous multiplace hyperbaric chamber staffed 24 hours a day.
Participants:
Unselected convenience sample of 61 adults with suspected CO toxicity.
Intervention:
Simultaneous sampling of arterial and venous blood.
Results:
Correlation between V-COHb and A-COHb showed an r value of .99 (95%CI, .99 to .99), and an r2 value of .98. Agreement between V-COHb and A-COHb levels was examined by use of a plot of arteriovenous differences against the mean of the two measurements. The mean arteriovenous difference was .15% COHb (95%CI, .13% to .45%), with 95% of the differences ranging from 2.4% COHb to -2.1% COHb.
Conclusion:
Venous COHb levels predict arterial levels with a high degree of accuracy. Patients with suspected CO poisoning can be screened with the use of venous blood, without the need for arterial puncture.