Venous admixture in human septic shock: comparative effects of blood volume expansion, dopamine infusion and isoproterenol infusion on mismatching of ventilation and pulmonary blood flow in peritonitis.

A hemodynamic study with blood gas analysis was performed so we could observe changes induced by blood volume expansion, dopamine infusion and isoproterenol infusion in 20 adult patients suffering from peritonitis complicated with septic shock and acute respiratory failure. Blood volume expansion increased cardiac index (from 2.6 +/- 1.21/min/m2 to 3.4 +/- 1.31/min/m2; p less than 0.001), but also enhanced venous admixture (QS/QT) from 27 +/- 14% to 36 +/- 13%; p less than 0.01). Dopamine infusion increased cardiac index (from 2.6 +/- 0.9 1/min/m2 to 3.4 +/- 1 l/min/m2; p less than 0.001), but also enhanced venous admixture (from 25 +/- 11% to 31 +/- 12%, p less than 0.001). Isoproterenol infusion increased cardiac index (from 2.6 +/- 0.9 l/min/m2 to 3.6 +/- 1.1 l/min/m2; p less than 0.001), but also enhanced venous admixture (from 27 +/- 12% to 33 +/- 11%; p less than 0.001). This worsening in mismatching of ventilation and blood flow is correlated with the enhancement in pulmonary blood flow obtained by these three therapeutic procedures.