title: Assisted venous drainage presents the risk of undetected air microembolism.
abstract: OBJECTIVE
  The proliferation of minimally invasive cardiac surgery has increased dependence on augmented venous return techniques for cardiopulmonary bypass. Such augmented techniques have the potential to introduce venous air emboli, which can pass to the patient. We examined the potential for the transmission of air emboli with different augmented venous return techniques.
  
  
  METHODS
  In vitro bypass systems with augmented venous drainage were created with either kinetically augmented or vacuum-augmented venous return. Roller or centrifugal pumps were used for arterial perfusion in combination with a hollow fiber oxygenator and a 40-micrometer arterial filter. Air was introduced into the venous line via an open 25-gauge needle. Test conditions involved varying the amount of negative venous pressure, the augmented venous return technique, and the arterial pump type. Measurements were recorded at the following sites: pre-arterial pump, post-arterial pump, post-oxygenator, and patient side.
  
  
  RESULTS
  Kinetically augmented venous return quickly filled the centrifugal venous pump with macrobubbles requiring continuous manual clearing; a steady state to test for air embolism could not be achieved. Vacuum-augmented venous return handled the air leakage satisfactorily and microbubbles per minute were measured. Higher vacuum pressures resulted in delivery of significantly more microbubbles to the "patient" (P <.001). The use of an arterial centrifugal pump was associated with fewer microbubbles (P =.02).
  
  
  CONCLUSIONS
  Some augmented venous return configurations permit a significant quantity of microbubbles to reach the patient despite filtration. A centrifugal pump has air-handling disadvantages when used for kinetic venous drainage, but when used as an arterial pump in combination with vacuum-assisted venous drainage it aids in clearing air emboli.
authors.affiliation: Department of Surgery, Division of Cardiothoracic Surgery, New York University School of Medicine, New York, NY, USA.
authors.forename: A
authors.initials: A
authors.lastname: Lapietra
authors.forename: E A
authors.initials: EA
authors.lastname: Grossi
authors.forename: B B
authors.initials: BB
authors.lastname: Pua
authors.forename: R A
authors.initials: RA
authors.lastname: Esposito
authors.forename: A C
authors.initials: AC
authors.lastname: Galloway
authors.forename: C C
authors.initials: CC
authors.lastname: Derivaux
authors.forename: L R
authors.initials: LR
authors.lastname: Glassman
authors.forename: A T
authors.initials: AT
authors.lastname: Culliford
authors.forename: G H
authors.initials: GH
authors.lastname: Ribakove
authors.forename: S B
authors.initials: SB
authors.lastname: Colvin
mesh_terms: D000704:Analysis of Variance; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass / Q000009:adverse effects* / Q000295:instrumentation*; D004618:Embolism, Air / Q000209:etiology* / Q000517:prevention & control; D004867:Equipment Design; D006801:Humans; D007431:Intraoperative Complications / Q000209:etiology* / Q000517:prevention & control; D016014:Linear Models; D019060:Minimally Invasive Surgical Procedures; D014618:Vacuum