title: Counteracting negative venous line pressures to avoid arterial air bubbles: an experimental study comparing two different types of miniaturized extracorporeal perfusion systems.
abstract: BACKGROUND
  Because of its low rate of clinical complications, miniaturized extracorporeal perfusion systems (MEPS) are frequently used in heart centers worldwide. However, many recent studies refer to the higher probability of gaseous microemboli formation by MEPS, caused by subzero pressure values. This is the main reason why various de-airing devices were developed for today's perfusion systems. In the present study, we investigated the potential benefits of a simple one-way-valve connected to a volume replacement reservoir (OVR) for volume and pressure compensation.
  
  
  METHODS
  In an experimental study on 26 pigs, we compared MEPS (n = 13) with MEPS plus OVR (n = 13). Except OVR, perfusion equipment was identical in both groups. Primary endpoints were pressure values in the venous line and the right atrium as well as the number and volume of air bubbles. Secondary endpoints were biochemical parameters of systemic inflammatory response, ischemia, hemodilution and hemolysis.
  
  
  RESULTS
  One animal was lost in the MEPS + OVR group. In the MEPS + OVR group no pressure values below -150 mmHg in the venous line and no values under -100 mmHg in right atrium were noticed. On the contrary, nearly 20% of venous pressure values in the MEPS group were below -150 and approximately 10% of right atrial pressure values were below -100 mmHg. Compared with the MEPS group, the bubble counter device showed lower numbers of arterial air bubbles in the MEPS + OVR group (mean ± SD: 13444 ± 5709 vs. 1 ± 2, respectively; p < 0.001). In addition, bubble volume was significantly lower in the MEPS + OVR group than in the MEPS group (mean ± SD: 1522 ± 654 μl vs. 4 ± 6 μl, respectively; p < 0.001). The proinflammatory cytokine interleukin-6 and biochemical indices of cardiac ischemia (creatine kinase, and troponin I) were comparable between both groups.
  
  
  CONCLUSIONS
  The use of a miniaturized perfusion system with a volume replacement reservoir is able to counteract excessive negative venous line pressures and to reduce the number and volume of arterial air bubbles. This approach may lead to a lower rate of neurological complications.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstrasse 11, 32545, Bad Oeynhausen, Germany. aaboud@hdz-nrw.de.
authors.forename: Anas
authors.initials: A
authors.lastname: Aboud
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstrasse 11, 32545, Bad Oeynhausen, Germany. hmederos-dahms@hdz-nrw.de.
authors.forename: Hendrikje
authors.initials: H
authors.lastname: Mederos-Dahms
authors.affiliation: Department of Medical Technology, Friedrich Schiller University, Jena, Germany. kai.liebing@med.uni-jena.de.
authors.forename: Kai
authors.initials: K
authors.lastname: Liebing
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstrasse 11, 32545, Bad Oeynhausen, Germany. azittermann@hdz-nrw.de.
authors.forename: Armin
authors.initials: A
authors.lastname: Zittermann
authors.affiliation: Institute of Laboratory Animal Science and Welfare, Friedrich Schiller University, Jena, Germany. harald.schubert@med.uni-jena.de.
authors.forename: Harald
authors.initials: H
authors.lastname: Schubert
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstrasse 11, 32545, Bad Oeynhausen, Germany. emurray@hdz-nrw.de.
authors.forename: Edward
authors.initials: E
authors.lastname: Murray
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstrasse 11, 32545, Bad Oeynhausen, Germany. arenner@hdz-nrw.de.
authors.forename: Andre
authors.initials: A
authors.lastname: Renner
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstrasse 11, 32545, Bad Oeynhausen, Germany. jgummert@hdz-nrw.de.
authors.forename: Jan
authors.initials: J
authors.lastname: Gummert
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstrasse 11, 32545, Bad Oeynhausen, Germany. jboergermann@hdz-nrw.de.
authors.forename: Jochen
authors.initials: J
authors.lastname: Börgermann
mesh_terms: D000818:Animals; D004618:Embolism, Air / Q000517:prevention & control*; D004867:Equipment Design; D005112:Extracorporeal Circulation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D006461:Hemolysis / Q000502:physiology; D007249:Inflammation / Q000209:etiology; D015850:Interleukin-6 / Q000378:metabolism; D008904:Miniaturization; D017202:Myocardial Ischemia / Q000209:etiology; D013552:Swine; D014690:Venous Pressure / Q000502:physiology*
chemical_list: D015850:Interleukin-6