title: Putting life on hold-for how long? Profound hypothermic cardiopulmonary bypass in a Swine model of complex vascular injuries.
abstract: BACKGROUND
  Rapid induction of profound hypothermia for emergency preservation and resuscitation can improve survival from uncontrolled lethal hemorrhage in large animal models. We have previously demonstrated that profound hypothermia (10 degrees C) must be induced rapidly (2 degrees C/min) and reversed gradually (0.5 degrees C/min) for best results. However, the maximum duration of hypothermic arrest in a clinically relevant trauma model remains unknown.
  
  
  METHODS
  Uncontrolled lethal hemorrhage was induced in 22 swine by creating an iliac artery and vein injury, followed 30 minutes later (simulating transport time) by laceration of the descending thoracic aorta. Through a thoracotomy approach, a catheter was placed in the aorta, and cold organ preservation solution was infused using a roller pump to rapidly induce profound hypothermia (10 degrees C) which was maintained with low-flow cardiopulmonary bypass. Vascular injuries were repaired during the asanguinous hypothermic low flow period. Profound hypothermia was maintained (n = 10-12 per group) for either 60 minutes or 120 minutes. After repair of injuries, animals were rewarmed (0.5 degrees C/min) and resuscitated on cardiopulmonary bypass, and whole blood was infused during this period. Animals were monitored for 4 weeks for neurologic deficits, organ dysfunction, and postoperative complications.
  
  
  RESULTS
  The 4-week survival rates in 60- and 120-minute groups were 92% and 50%, respectively (p < 0.05). The surviving animals were neurologically intact and had no long-term organ dysfunction, except for one animal in the 120-minute group. The animals subjected to 120 minutes of hypothermia had significantly worse lactic acidosis, displayed markedly slower recovery, and had significantly higher rates of postoperative complications, including late deaths because of infections.
  
  
  CONCLUSIONS
  In a model of lethal injuries, rapid induction of profound hypothermia can prevent death. Profound hypothermia decreases but does not abolish metabolism. With current methods, the upper limit of hypothermic arrest in the setting of uncontrolled hemorrhage is 60 minutes.
authors.affiliation: Division of Trauma, Emergency Surgery and Surgical Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Hasan B
authors.initials: HB
authors.lastname: Alam
authors.forename: Michael
authors.initials: M
authors.lastname: Duggan
authors.forename: Yongqing
authors.initials: Y
authors.lastname: Li
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Spaniolas
authors.forename: Baoling
authors.initials: B
authors.lastname: Liu
authors.forename: Malek
authors.initials: M
authors.lastname: Tabbara
authors.forename: Marc
authors.initials: M
authors.lastname: Demoya
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Sailhamer
authors.forename: Christian
authors.initials: C
authors.lastname: Shults
authors.forename: George C
authors.initials: GC
authors.lastname: Velmahos
mesh_terms: D000818:Animals; D001831:Body Temperature; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D002315:Cardiopulmonary Bypass / Q000379:methods / Q000401:mortality*; D050792:Circulatory Arrest, Deep Hypothermia Induced; D003071:Cognition / Q000502:physiology; D004195:Disease Models, Animal; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D009483:Neuropsychological Tests; D011336:Probability; D011897:Random Allocation; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012771:Shock, Hemorrhagic / Q000401:mortality* / Q000628:therapy*; D016019:Survival Analysis; D013552:Swine; D013997:Time Factors; D014950:Wounds, Penetrating / Q000401:mortality / Q000628:therapy