title: Effect of blood pressure on hemorrhage volume and survival in a near-fatal hemorrhage model incorporating a vascular injury.
abstract: OBJECTIVE
  In a model of near-fatal hemorrhage that incorporates a vascular injury, stepwise increases in blood pressure associated with aggressive crystalloid resuscitation will result in increased hemorrhage volume and mortality.
  
  
  METHODS
  This study used a swine model of potentially lethal hemorrhage in the presence of a vascular lesion to compare the effects of resuscitation with mean arterial pressures of 40, 60, and 80 mm Hg. Twenty-seven fully instrumented immature swine (14.8 to 20 kg), each with a surgical-steel aortotomy wire in place, were bled continuously from a femoral artery catheter to a mean arterial pressure of 30 mm Hg. At that point the aortotomy wire was pulled, producing a 4-mm aortic tear and uncontrolled intraperitoneal hemorrhage. When the animal's pulse pressure reached 5 mm Hg, the femoral artery hemorrhage was discontinued and resuscitation was begun.
  
  
  METHODS
  Saline infusion was begun at 6 mL/kg/min and continued as needed to maintain the following desired endpoints: group 1 (nine) to a mean arterial pressure of 40 mm Hg, group 2 (nine) to a mean arterial pressure of 60 mm Hg, and group 3 (nine) to a mean arterial pressure of 80 mm Hg. After 30 minutes or a total saline infusion of 90 mL/kg, the resuscitation fluid was changed to shed blood infused at 2 mL/kg/min as needed to maintain the desired mean arterial pressure or to a maximum volume of 24 mL/kg. Animals were observed for 60 minutes or until death.
  
  
  RESULTS
  Data were compared using repeated-measures analysis of variance with a post hoc Tukey-Kramer, Fisher's exact test, and Kruskal-Wallis. Mortality was significantly greater in group 3 (78%) compared with either group 1 (11%; P = .008) or group 2 (22%; P = .028). Mean survival times were significantly shorter in group 3 (44 +/- 12 minutes) compared with either group 1 (58 +/- 6 minutes; P = .007) or group 2 (59 +/- 3 minutes; P = .006). The average intraperitoneal hemorrhage volumes were 13 +/- 14 mL/kg, 20 +/- 25 mL/kg, and 46 +/- 11 mL/kg for groups 1, 2, and 3, respectively (group 1 versus 2, P = .425; group 1 versus 3, P < .001; group 2 versus 3, P = .014). Group 2 animals demonstrated significantly greater oxygen deliveries compared with groups 1 and 3.
  
  
  CONCLUSIONS
  In a model of near-fatal hemorrhage with a vascular injury, attempts to restore blood pressure with crystalloid result in increased hemorrhage volume and markedly higher mortality.
authors.affiliation: Department of Emergency Medicine, University of Cincinnati College of Medicine, Ohio.
authors.forename: S A
authors.initials: SA
authors.lastname: Stern
authors.forename: S C
authors.initials: SC
authors.lastname: Dronen
authors.forename: P
authors.initials: P
authors.lastname: Birrer
authors.forename: X
authors.initials: X
authors.lastname: Wang
mesh_terms: D000818:Animals; D001011:Aorta / Q000293:injuries*; D001794:Blood Pressure; D001810:Blood Volume; D000077324:Crystalloid Solutions; D005440:Fluid Therapy / Q000009:adverse effects*; D006470:Hemorrhage / Q000503:physiopathology; D007552:Isotonic Solutions; D008954:Models, Biological; D010952:Plasma Substitutes / Q000627:therapeutic use; D012771:Shock, Hemorrhagic / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy; D015996:Survival Rate; D013552:Swine
chemical_list: D000077324:Crystalloid Solutions; D007552:Isotonic Solutions; D010952:Plasma Substitutes