Muscle oxygen tension, hemodynamics, and oxygen transport after extracorporeal circulation

In eight patients who underwent elective coronary bypass operation, skeletal muscle PO2 was measured with a polarographic needle electrode as an index of peripheral tissue perfusion to study recovery after extracorporeal circulation. Measurements of skeletal muscle PO2 and O2 supply to the tissues were obtained immediately after ICU admission and after 2, 4, 8, and 16 h. During the first 2 h, mean arterial BP was high, mixed venous PO2 decreased, the arteriovenous O2 difference increased, and skeletal muscle PO2 decreased. The P50 of the O2 dissociation curve on ICU admission was decreased and thereafter increased to a maximal value at 8 h, and normalized again after 16 h. After the initial decrease, the median of the skeletal muscle PO2 returned to normal values, but decreased again after 16 h. The results showed that, during the first 4 h postoperatively, microcirculatory changes occurred despite normal cardiovascular and respiratory variables.