Vacuum-assisted venous drainage, angel or demon: PRO?

Vacuum-assisted venous drainage (VAVD) was proposed to optimize venous drainage during bypass through femoral venous cannulation. It is currently used in both adult and pediatric surgery when siphon gravity venous drainage is suboptimal. In pediatric surgery, the major advantages of VAVD are a significant decrease in cardiopulmonary bypass prime volume and an improved drainage with all collateral benefits. To limit gravity drainage, we use a two-level heart-lung machine dedicated to pediatric perfusion. The top level of the cardiotomy reservoir is positioned at the patient atrial level, making it possible to downsize the length and diameter of venous and arterial lines. Since 2008, a negative pressure of approximately -30 mmHg has been used for all patients. Initiation of bypass is performed in a classical way with a cardiotomy reservoir open; vacuum is added as soon as the maximal gravity drainage is reached. During bypass, when the blood level in the reservoir decreases to the safety limit level, a small increase in negative pressure is used to improve venous drainage. For weaning from bypass, the negative pressure is gradually decreased to zero, then the reservoir is opened and the venous line progressively closed. Prime volumes were significantly reduced to 100 mL for small neonates, 125 mL for infants, and 175 mL for older children with flow up to 1.5 L/min(-1). A low prime volume is expected to improve blood conservation and decrease donor exposure, prevent drawbacks of transfusion (immunomodulation, infection), increase the incidence of blood-free surgery in smaller babies, and decrease whole body systemic inflammation by decreasing surface of foreign material in contact with blood and inflammation associated with blood transfusion. The main drawbacks described have been retrograde flow in the venous line with cerebral air embolus and an increased incidence of gaseous microemboli. These drawbacks are avoidable through appropriate training of perfusionists. When negative pressure is "reasonable," complications are more theoretical than significant in clinical practice. A technique with a benefit/drawback ratio of 1:0 is utopian, but the advantages of VAVD far outweigh any potential drawbacks when applied properly.