title: Laser Doppler imaging for early detection of hemorrhage.
abstract: BACKGROUND
  Laser Doppler Imaging (LDI) is a noninvasive means to measure blood flow through the superficial skin capillary plexus using flux units. Our objective was to determine the ability of LDI of the skin to detect and quantify rapid, severe hemorrhage.
  
  
  METHODS
  Five Yucatan mini-pigs (25-35 kg) underwent controlled hemorrhage of 25 mL/kg blood for 20 minutes. Median flux of a 10 cm × 10 cm area of the lower abdomen was measured at 2-minute intervals from initiation of hemorrhage to resuscitation with concurrent measurement of heart rate (HR), systolic blood pressure (SBP), and mean arterial pressure (MAP).
  
  
  RESULTS
  Average time to a change of 5 U in flux following start of hemorrhage was 2.4 minutes. This was significantly faster than time to change in HR (19.2 minutes, p < 0.05) and showed a trend toward more rapid identification of hemorrhage relative to changes in SBP (3.2 minutes, p = 0.157) and MAP (3.6 minutes, p = 0.083). Flux changes occurred at smaller % total blood volume lost than HR (3.94% vs. 28.8%, p < 0.05) and trended toward smaller volume identification than SBP (4.88%, p = 0.180) and MAP (5.36%, p = 0.102). Average correlation (ρ) of blood volume lost to flux was -0.974; HR, 0.346; SBP, -0.978; and MAP, -0.975. A change of 5 flux units was significantly more sensitive for hemorrhage than a change of 5 beats per minute in HR or 5 mm Hg in SBP or MAP (0.596 vs. 0.169, 0.438, and 0.287 respectively, all p < 0.05).
  
  
  CONCLUSIONS
  LDI is a sensitive, specific, and early means to detect and quantify severe hemorrhage.
authors.affiliation: Division of Trauma, Burns and Critical Care and Acute Care Surgery, Department of Surgery, University of California, Irvine, California, USA.
authors.forename: Meghann Lee
authors.initials: ML
authors.lastname: Kaiser
authors.forename: Allen P
authors.initials: AP
authors.lastname: Kong
authors.forename: Earl
authors.initials: E
authors.lastname: Steward
authors.forename: Matthew
authors.initials: M
authors.lastname: Whealon
authors.forename: Madhukar
authors.initials: M
authors.lastname: Patel
authors.forename: David Butler
authors.initials: DB
authors.lastname: Hoyt
authors.forename: Marianne E
authors.initials: ME
authors.lastname: Cinat
mesh_terms: D000818:Animals; D001810:Blood Volume; D004195:Disease Models, Animal; D006470:Hemorrhage / Q000175:diagnosis*; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D008297:Male; D012771:Shock, Hemorrhagic / Q000175:diagnosis*; D012867:Skin / Q000098:blood supply*; D013552:Swine; D013556:Swine, Miniature