title: Ultrasound destruction of air microemboli as a novel approach to brain protection in cardiac surgery.
abstract: OBJECTIVE
  Evaluation of a novel approach to eliminate air microemboli from extracorporeal circulation via ultrasonic destruction.
  
  
  METHODS
  In vitro proof-of-concept study.
  
  
  METHODS
  Research laboratory.
  
  
  METHODS
  None.
  
  
  METHODS
  None.
  
  
  RESULTS
  An extracorporeal circulation device was filled with human blood circulating at 3 L/min. Air bubbles were injected into the system. For bubble destruction, the blood in the tubing system was repeatedly insonated for 3 minutes using a therapeutic 60-kHz device, with variation of intensity and duty cycle settings, ranging from 0.2 W/cm² to 1.0 W/cm² and from duty cycle 60% to continuous wave (CW). Number and diameter of air microemboli were counted upstream and downstream of the ultrasound device by a 2-channel microemboli Doppler detector. For safety assessment, circulating blood was insonated continuously for 2 hours at 0.8 W/cm² CW and compared with circulation without insonation; and standard blood parameters were analyzed. Without treatment, 1,313 to 1,580 emboli were detected upstream, diameter ranging between 10 and 130 μm. Ultrasound treatment eliminated up to 87% of all detected bubbles in cw application (p<0.01) and showed comparable effects at intensities from 0.4 W/cm² to 1.0 W/cm² cw. Bubbles sized>15 μm almost were eliminated completely (p<0.001). Pulsed wave application rendered inferior results (p>0.05). No relevant changes of blood parameters were observed compared with control circulation.
  
  
  CONCLUSIONS
  Ultrasound destruction of air emboli is a very efficient method to reduce number and size of emboli. Within the limits of safety assessment, the authors could not detect relevant side effects on standard blood parameters.
authors.affiliation: Department of Neurology, Justus-Liebig-University, Giessen, Germany; Heart and Brain Research Group, Justus-Liebig-University, Giessen and Kerckhoff Clinic, Bad Nauheim, Germany. Electronic address: max.nedelmann@neuro.med.uni-giessen.de.
authors.forename: Max
authors.initials: M
authors.lastname: Nedelmann
authors.forename: Nadine
authors.initials: N
authors.lastname: Schleicher
authors.forename: Simone
authors.initials: S
authors.lastname: Doenges
authors.forename: Peter
authors.initials: P
authors.lastname: Reuter
authors.forename: Manfred
authors.initials: M
authors.lastname: Kaps
authors.forename: Simon
authors.initials: S
authors.lastname: Urbanek
authors.forename: Niko
authors.initials: N
authors.lastname: Schwarz
authors.forename: Katharina
authors.initials: K
authors.lastname: Madlener
authors.forename: Markus
authors.initials: M
authors.lastname: Schoenburg
authors.forename: Petr
authors.initials: P
authors.lastname: Urbanek
authors.forename: Tibo
authors.initials: T
authors.lastname: Gerriets
mesh_terms: D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D004618:Embolism, Air / Q000517:prevention & control*; D005112:Extracorporeal Circulation / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D020766:Intracranial Embolism / Q000097:blood / Q000517:prevention & control*; D018084:Ultrasonography, Interventional / Q000295:instrumentation / Q000379:methods*
keywords: CNS protection; air emboli; brain; cardiopulmonary bypass; complications; embolism; microemboli; stroke; ultrasound