Blood return into the cardiotomy reservoir is usually reduced when a cardiopulmonary bypass (CPB) is initiated through a peripheral access, even if the tip of the venous cannula is pushed into the right atrium. A centrifugal pump can be placed on the venous line to increase the negative pressure. Surgery involving the right atrium requires selective cannulation of both vena cavae. Because of the small diameter of the vena cava as compared to the right atrium, the benefit of the centrifugal pump may have limitations. We analyze the factors influencing the active venous return when the cannula is maintained into the vena cava. In 4 calves (83.0+/-14.9 Kg) a CPB was initiated through carotid and jugular access, with the tip of the venous cannula placed into the superior vena cava, before ventricular fibrillation was provoked. Venous drainage was progressively increased thanks to the centrifugal pump. Considering the negative pressure induced on the venous line, we analyzed the performance expressed in l/min of blood drained, of four one stage cannulae ("lighthouse" tip 24F, 28F or 32F, and percutaneous 28F). The performance of all cannulae were highly dependent on the central venous pressure (CVP) with better drainage for higher CVP. The size and type of cannula also significantly affected blood drainage. Active drainage was best with the percutaneous 28F cannula. This cannula was specially attractive at low CVP conditions.