title: Rapid (0.5 degrees C/min) minimally invasive induction of hypothermia using cold perfluorochemical lung lavage in dogs.
abstract: OBJECTIVE
  Demonstrate minimally invasive rapid body core and brain cooling in a large animal model.
  
  
  METHODS
  Prospective controlled animal trial.
  
  
  METHODS
  Private research laboratory.
  
  
  METHODS
  Adult dogs, anesthetized, mechanically ventilated.
  
  
  METHODS
  Cyclic lung lavage with FC-75 perfluorochemical (PFC) was administered through a dual-lumen endotracheal system in the new technique of 'gas/liquid ventilation' (GLV). In Trial-I, lavage volume (V-lav) was 19 ml/kg, infused and withdrawn over a cycle period (tc) of 37 s. (effective lavage rate V'-lav=31 ml/kg/min.) Five dogs received cold (approximately 4 degrees C) PFC; two controls received isothermic PFC. In Trial-II, five dogs received GLV at V-lav=8.8 ml/kg, tc=16 s, V'-lav=36 ml/kg/min.
  
  
  RESULTS
  Trial-I tympanic temperature change was -3.7+/-0.6 degrees C (SD) at 7.5 min, reaching -7.3+/-0.6 degrees C at 18 min. Heat transfer efficiency was 60%. In Trial-II, efficiency fell to 40%, but heat-exchange dead space (VDtherm) remained constant. Lung/blood thermal equilibration half-time was <8 s. Isothermic GLV caused hypercapnia unless gas ventilation was increased. At necropsy after euthanasia (24 h), modest lung injury was seen.
  
  
  CONCLUSIONS
  GLV cooling times are comparable to those for cardiopulmonary bypass. Heat and CO(2) removal can be independently controlled by changing the mix of lavage and gas ventilation. Due to VDtherm of approximately 6 ml/kg in dogs, efficient V-lav is >18 ml/kg. GLV cooling power appears more limited by PFC flows than lavage residence times. Concurrent gas ventilation may mitigate heat-diffusion limitations in liquid breathing, perhaps via bubble-induced turbulence.
authors.affiliation: Critical Care Research, Inc. 10743 Civic Center Drive, Rancho Cucamonga, CA 91730-3806, USA. sbharris@ix.netcom.com
authors.forename: S B
authors.initials: SB
authors.lastname: Harris
authors.forename: M G
authors.initials: MG
authors.lastname: Darwin
authors.forename: S R
authors.initials: SR
authors.lastname: Russell
authors.forename: J M
authors.initials: JM
authors.lastname: O'Farrell
authors.forename: M
authors.initials: M
authors.lastname: Fletcher
authors.forename: B
authors.initials: B
authors.lastname: Wowk
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology; D001930:Brain Injuries / Q000628:therapy; D018893:Bronchoalveolar Lavage / Q000009:adverse effects; D004285:Dogs; D005466:Fluorocarbons / Q000008:administration & dosage*; D007036:Hypothermia, Induced / Q000379:methods*; D007260:Infusion Pumps; D021061:Liquid Ventilation / Q000295:instrumentation / Q000379:methods*; D008168:Lung / Q000473:pathology*; D055370:Lung Injury; D023421:Models, Animal; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D013119:Spinal Cord Injuries / Q000628:therapy; D013997:Time Factors
chemical_list: D005466:Fluorocarbons