RELATIONSHIP BETWEEN VENOUS AND ARTERIAL CARBOXYHEMOGLOBIN LEVELS IN PATIENTS WITH SUSPECTED CARBON-MONOXIDE POISONING

Study objective: To test the hypothesis that venous carboxyhemoglobin (V-COHb) levels accurately predict arterial (A-COHb) levels. Design: P rospective comparison of A-COHb and V-COHb levels in patients with sus pected carbon monoxide (GO) poisoning. Setting: Municipal hospital eme rgency department with contiguous multiplace hyperbaric chamber staffe d 24 hours a day. Participants: Unselected convenience sample of 61 ad ults with suspected CO toxicity. Intervention: Simultaneous sampling o f arterial and venous blood. Results: Correlation between V-COHb and A -COHb showed an r value of .99 (95%Cl, .99 to .99), and an r(2) 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 me asurements. The mean arteriovenous difference was .15% COHb (95%Cl, .1 3% 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 p uncture.