Assessment of acid-base status and plasma lactate concentrations in arterial, mixed venous, and portal blood from dogs during experimental hepatic blood inflow occlusion

To determine the effects of extended experimental hepatic blood flow occlusion (ie, portal triad clamping [PTC]) in dogs by measuring acid-base status and plasma lactate concentrations in arterial, mixed venous, and portal blood and evaluating the relationship between metabolic and concurrent hemodynamic changes. 6 healthy Beagles. During anesthesia with isoflurane, cardiac output and arterial blood pressure were measured. Arterial, mixed venous, and portal blood samples were collected simultaneously for blood gas analyses and plasma lactate measurements before PTC and at 8-minute intervals thereafter. PTC resulted in severe hemodynamic and metabolic alterations. Eight minutes after PTC, significant decreases in cardiac index from a baseline value of 3.40 +/- 0.27 to 1.54 +/- 0.26 L/min/m2 and in mean arterial blood pressure from a baseline value of 74 +/- 6 to 43 +/- 6 mm Hg were recorded. After PTC, results indicative of lactic acidosis were found in portal blood at 16 minutes, in mixed venous at 32 minutes, and in arterial blood at 48 minutes. Significant differences in measured variables were also found between arterial and portal blood samples, between mixed venous and portal blood samples, and between arterial and mixed venous blood samples after PTC, compared with differences at baseline. Analysis of mixed venous blood is preferable to analysis of arterial blood in the assessment of metabolic derangement. In a clinical setting, occluded portal blood is released to the systemic circulation, and the degree of reperfusion injury may depend on the metabolic status of pooled portal blood.