Comparison of arterial and capillary blood gas values in poisoning department assessment

Abstract

The aim of this study was to compare simultaneously obtained arterial and capillary blood gas (CBG) values in comatose-poisoned patients presented with stable vital signs. Forty-five adult patients with a diagnosis of coma because of poisoning and stable vital signs were included in this prospective study. With respect to pH, the arterial blood gas (ABG) and CBG values correlated satisfactorily (r² = .91) and had an acceptable limit of agreements (LOAs; —0.04 to 0.06). With respect to base excess (BE), the ABG and CBG values correlated well (r² = .85), but their 95% LOAs seem too wide to allow substitution (—4.4 to 2.7). PCO₂ (r² = .61), HCO₃ (r² = .71) and PO₂ (r² = .53) correlated less reliably. A capillary PCO₂ of 51.7 mm Hg had a sensitivity of 100% and a specificity of 95.12% for detecting hypercarbia (area under the curve, 0.99; 95% Confidence Interval, 0.90-0.99; p < .0001). In conclusion, CBG analysis for pH may be a reliable substitute for ABG analysis in the initial evaluation of patients presenting with coma and stable vital signs to the poisoning emergency department (PED). Subsequent ABG may be required in patients with capillary PCO₂ > 51.7 mm Hg.