Venoarterial carbon dioxide tension gradient in acute heart failure

The venoarterial carbon dioxide tension gradient (P[v-a]CO2) was studied in patients with acute myocardial infarction. Seven patients with congestive heart failure (CHF group) and 10 patients without heart failure (control) were enrolled in this study. In all patients, hemodynamics were continuously monitored. Simultaneously, arterial and mixed venous blood were sampled, and blood gases and lactate concentration were analyzed. At the initial measurement before therapy, arterial and mixed venous pH and bicarbonate values were within the normal range, and there was no significant difference between the CHF group and controls. There was also no difference in arterial oxygen tension under the differential conditions of oxygen inhalation. However, cardiac index and mixed venous oxygen saturation (SvO2) were significantly lower, while the oxygen extraction ratio (OER) and arterial lactate were significantly higher in the CHF group than in the controls. On the other hand, P[v-a]CO2 was significantly higher in the CHF group (7.8 +/- 2.6 vs. 3.5 +/- 2.2 mm Hg, p < 0.01). This finding was due to the elevated mixed venous carbon dioxide tension in the CHF group, since arterial carbon dioxide tension was the same in both groups. Analysis of a total of 42 measurements obtained during the therapeutic course in the CHF group revealed a correlation of P[v-a]CO2 with cardiac index (r = -0.3, p < 0.05), OER (r = 0.57, p < 0.001), SvO2 (r = -0.56, p < 0.001) and lactate (r = 0.62, p < 0.001). The increase in P[v-a]CO2 observed in acute heart failure suggests the evidence of intracellular acidosis despite the absence of acidemia.(ABSTRACT TRUNCATED AT 250 WORDS)