Background: To investigate blood lactate levels during and after peripherally established cardiopulmonary bypass (CPB).Methods: In 86 patients (41 males, mean age 13.8 ± 7.2), CPB was established via femoral vein and artery cannulation for thoracoscopic closure of atrial (n = 54) or ventricular septal defect (n = 32). Arterial and venous blood lactate levels were measured from the cannulated limb during CPB, and from systemic circulation after CPB.Results: The mean duration of CPB and cannulation of a lower extremity were 50.0 ± 10.5 min and 76.0 ± 18.5 min, respectively. The mean arterial lactate level measured from the systemic circulation remained unchanged during CPB

0.05). In patients with CPB for 3 h or more, mean arterial lactate in the cannulated limb were higher than the baseline values (3.3 ±0.5 vs 0.8 ± 0.2 mmol/L, P<0.05). In patients with more than 2h of CPB, mean venous lactate levels in the cannulated limb were also higher than the baseline values (3.4 ± 0.2 vs 1.1 ± 0.3 mmol/L, P< 0.05). Within 6 h after CPB, systemic arterial (3.0 ±0.2 vs 0.8 ± 0.1 mmol/L, P<0.01) and venous lactate levels (6.5 ±0.2 vs 1.0 ± 0.1 mmol/L, F<0.01) were higher than the pre-CPB values.Conclusions: Peripherally established CPB was associated with an arterial and venous lactate elevation in local and systemic circulation. The duration of CPB and lower limb cannulation appears to be related to the lactate elevation.