Arterial blood gas analysis is the gold standard for the assessment of oxygenation, ventilation, and metabolic status in dogs; however, its execution is difficult and painful. Therefore, venous blood gas analysis is used in its replacement for the assessment of the metabolic status, but it is not clear whether it can be used to assess respiratory function, too. This study aimed at: 1) comparing jugular and saphenous pH and partial pressure of carbon dioxide (pCO2) with the correspondent arterial pH and pCO2 (paCO2) in healthy dogs during general anesthesia; 2) clarifying whether the arterial-venous relationship is better expressed in jugular or saphenous blood samples; 3) mathematically transforming venous pCO2 (pvCO2) and evaluating whether the calculated values more accurately agree with paCO2.
Ninety dogs were included and randomly divided into three groups: Group 1 - arterial vs jugular; Group 2 - arterial vs saphenous; Group 3 - arterial vs jugular vs saphenous blood gases. Each group counted 30 dogs. Pearson correlations were calculated. Bland-Altman plots were generated to describe the agreement between venous and arterial values; clinical limits for pH and pCO2 set by the authors were, respectively, ± 0.1 and ± 2.5 mmHg. Univariate linear regression was applied for predicting paCO2 from pvCO2.
Saphenous samples showed strong positive correlations with arterial samples for both pCO2 and pH. Pearson
In healthy, anesthetized, mechanically ventilated dogs, variations of pH between venous and arterial values are clinically acceptable. Venous and arterial blood gases cannot be interchanged for the evaluation of pCO2. Saphenous pvCO2 is to be preferable to jugular pvCO2 as predictor of paCO2. A formula for the estimation of predicted paCO2 from saphenous pvCO2 is proposed.