title: Behavior of gaseous microemboli in extracorporeal circuits: air versus CO2.
abstract: BACKGROUND
  Open heart surgery is associated with serious risk of cerebral and peripheral organ dysfunction, attributed in part to air microbubbles generated in or not eliminated from the extracorporeal circuit (ECC). Venous air leakage leads to increased arterial bubble load. CO2 replacing air in cardiac chambers show faster resorption times, reducing possible cerebral or peripheral organ damage after heart valve interventions. In two models of ECC the effect of air entering closed circuits was demonstrated and compared to the effect of CO2 entry.
  
  
  METHODS
  Fragmentation and dissolution of gas (0.5 mL) was evaluated in an in vitro model of ECC, using ultrasonic bubble detection. Air leakage (10 mL) in the venous line of the ECC was simulated and compared to the effect of the same quantity of CO2 entering the circuit. Both models used whole blood priming and physiological conditions, verified with blood gas analyses.
  
  
  RESULTS
  Fragmentation and dissolution of gas bubbles injected into a closed ECC could be demonstrated, complete resorption of CO2 bubbles was observed earlier than complete resorption of room air (5.0+/-0.6 vs. 14.4+/-5.9 min, p=0.0009). CO2 entering the venous line lead to 40% less arterial bubble load as compared to the same amount of room air entering the circuit (2099+/-991 vs. 3555+/-632, p=0.005).
  
  
  CONCLUSIONS
  Current ECC systems fail to eliminate gas entering the circuit, leading rather to microbubble dispersion. CO2 is much faster resorbed within the circuit than room air. In open heart surgery as valvular operations, CO2 insufflation into the operative field is protective, as we have demonstrated in our models.
authors.affiliation: Department for Thoracic and Cardiovascular Surgery, University Hospital J.W. Goethe, Frankfurt am Main - Germany. martens.herz@gmx.de
authors.forename: S
authors.initials: S
authors.lastname: Martens
authors.forename: M
authors.initials: M
authors.lastname: Dietrich
authors.forename: M
authors.initials: M
authors.lastname: Doss
authors.forename: M
authors.initials: M
authors.lastname: Deschka
authors.forename: H
authors.initials: H
authors.lastname: Keller
authors.forename: A
authors.initials: A
authors.lastname: Moritz
mesh_terms: D000388:Air; D002245:Carbon Dioxide; D004618:Embolism, Air / Q000209:etiology*; D005112:Extracorporeal Circulation / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D066298:In Vitro Techniques
chemical_list: D002245:Carbon Dioxide