Relationship between arterial, mixed venous, and internal jugular carboxyhemoglobin concentrations at low, medium, and high concentrations in a piglet model of carbon monoxide toxicity

Objective: This study tested the hypothesis that mixed venous carboxyhemoglobin concentrations (V-COHb) and internal jugular carboxyhemoglobin concentrations (I-COHb) accurately predict arterial carboxyhemoglobin concentrations (A-COHb). In addition, this study tested the hypothesis that there is a high correlation at low (COHb, 0% to 10%), moderate (COHb, >10% to 40%), and high (COHb, >40%) concentrations between V- COHb, I-COHb, and A-COHb. Design: The study was a prospective comparison of A-COHb, V-COHb, and I-COHb concentrations in piglets exposed to increasing concentrations of carbon monoxide over 6 hrs to achieve a concentration of ≥60% COHb. Carboxyhemoglobin measurements were evaluated by analysis of variance and correlation analysis. Agreement between V-COHb and A-COHb concentrations was examined by using a plot of arteriovenous differences against the mean of the two measurements. Intervention: We simultaneously sampled arterial, mixed venous, and internal jugular blood every 30 mins over the 6-hr study period. Results: Two hundred fifty arterial and mixed venous COHb concentrations were obtained, and 214 internal jugular COHb concentrations were obtained. One hundred additional arterial, mixed venous, internal jugular, and peripheral COHb concentrations were obtained. Correlation between samples at each concentration revealed r² ≥ .94. Conclusion: Venous COHb concentrations predict arterial COHb concentrations with a high degree of accuracy and are correlated at low, moderate, and high concentrations of carbon monoxide exposure. Arterial or venous samples can be used to accurately measure COHb concentrations.