title: Rapid assessment of shock in a nonhuman primate model of uncontrolled hemorrhage: Association of traditional and nontraditional vital signs to mortality risk.
abstract: BACKGROUND
  Heart rate (HR), systolic blood pressure (SBP) and mean arterial pressure (MAP) are traditionally used to guide patient triage and resuscitation; however, they correlate poorly to shock severity. Therefore, improved acute diagnostic capabilities are needed. Here, we correlated acute alterations in tissue oxygen saturation (StO2) and end-tidal carbon dioxide (ETCO2) to mortality in a rhesus macaque model of uncontrolled hemorrhage.
  
  
  METHODS
  Uncontrolled hemorrhage was induced in anesthetized rhesus macaques by a laparoscopic 60% left-lobe hepatectomy (T = 0 minute). StO2, ETCO2, HR, as well as invasive SBP and MAP were continuously monitored through T = 480 minutes. At T = 120 minutes, bleeding was surgically controlled, and blood loss was quantified. Data analyses compared nonsurvivors (expired before T = 480 minutes, n = 5) with survivors (survived to T = 480 minutes, n = 11) using repeated-measures analysis of variance with Bonferroni correction. All p < 0.05 was considered statistically significant. Results were reported as mean ± SEM.
  
  
  RESULTS
  Baseline values were equivalent between groups for each parameter. In nonsurvivors versus survivors at T = 5 minutes, StO2 (55% ± 10% vs. 78% ± 3%, p = 0.02) and ETCO2 (15 ± 2 vs. 25 ± 2 mm Hg, p = 0.0005) were lower, while MAP (18 ± 1 vs. 23 ± 2 mm Hg, p = 0.2), SBP (26 ± 2 vs. 34 ± 3 mm Hg, p = 0.4), and HR (104 ± 13 vs. 105 ± 6 beats/min, p = 0.3) were similar. Association of values over T = 5-30 minutes to mortality demonstrated StO2 and ETCO2 equivalency with a significant group effect (p ≤ 0.009 for each parameter; R(2) = 0.92 and R(2) = 0.90, respectively). MAP and SBP associated with mortality later into the shock period (p < 0.04 for each parameter; R(2) = 0.91 and R(2) = 0.89, respectively), while HR yielded the lowest association (p = 0.8, R(2) = 0.83).
  
  
  CONCLUSIONS
  Acute alterations in StO2 and ETCO2 strongly associated with mortality and preceded those of traditional vital signs. The continuous, noninvasive aspects of Food and Drug Administration-approved StO2 and ETCO2 monitoring devices provide logistical benefits over other methodologies and thus warrant further investigation.
authors.affiliation: From the Naval Medical Research Unit-San Antonio (R.F.C., A.M., A.R.M., J.E.C., F.R.S.); US Army Institute of Surgical Research (J.K.A.), JBSA-Fort Sam Houston, San Antonio, Texas.
authors.forename: Randy F
authors.initials: RF
authors.lastname: Crossland
authors.forename: Alex
authors.initials: A
authors.lastname: Mitchell
authors.forename: Antoni R
authors.initials: AR
authors.lastname: Macko
authors.forename: James K
authors.initials: JK
authors.lastname: Aden
authors.forename: James E
authors.initials: JE
authors.lastname: Campbell
authors.forename: Forest R
authors.initials: FR
authors.lastname: Sheppard
mesh_terms: D000818:Animals; D062186:Arterial Pressure / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism; D004195:Disease Models, Animal; D006339:Heart Rate / Q000502:physiology; D008253:Macaca mulatta; D008297:Male; D008991:Monitoring, Physiologic; D010100:Oxygen / Q000097:blood; D012151:Resuscitation; D012771:Shock, Hemorrhagic / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy; D055986:Vital Signs
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen