title: "Permissive hypoventilation" in a swine model of hemorrhagic shock.
abstract: BACKGROUND
  Many penetrating trauma patients in severe hemorrhagic shock receive positive pressure ventilation (PPV) upon transport to definitive care, either by intubation (INT) or bag-valve mask (BVM). Using a swine hemorrhagic shock model that simulates penetrating trauma, we proposed that severely injured patients may have better outcomes with "permissive hypoventilation," where manual breaths are not given and oxygen is administrated passively via face mask (FM). We hypothesized that PPV has harmful physiologic effects in severe low-flow states and that permissive hypoventilation would result in better outcomes.
  
  
  METHODS
  The carotid arteries of Yorkshire pigs were cannulated with a 14-gauge catheter. One group of animals (n = 6) was intubated and manually ventilated, a second received PPV via BVM (n = 7), and a third group received 100% oxygen via FM (n = 6). After placement of a Swan-Ganz catheter, the carotid catheters were opened, and the animals were exsanguinated. The primary end point was time until death. Secondary end points included central venous pressure, cardiac output, lactate levels, serum creatinine, CO2 levels, and pH measured in 10-minute intervals.
  
  
  RESULTS
  Average survival time in the FM group (50.0 minutes) was not different from the INT (51.1 minutes) and BVM groups (48.5 minutes) (p = 0.84). Central venous pressure was higher in the FM group as compared with the INT 10 minutes into the shock phase (8.3 mm Hg vs. 5.2 mm Hg, p = 0.04). Drop in cardiac output (p < 0.001) and increase in lactate (p < 0.05) was worse in both PPV groups throughout the shock phase. Creatinine levels were higher in both PPV groups (p = 0.04). The FM group was more hypercarbic and acidotic than the two PPV groups during the shock phase (p < 0.001).
  
  
  CONCLUSIONS
  Although permissive hypoventilation leads to respiratory acidosis, it results in less hemodynamic suppression and better perfusion of vital organs. In severely injured penetrating trauma patients, consideration should be given to immediate transportation without PPV.
authors: From the Department of Surgery (S.T., S.N.J., L.M.F., R.E.M., J.D., L.O.S., A.P., J.F.R., T.A.S., A.J.G.), Biostatistics Consulting Center (J.P.G.), and Cardiovascular Research Center (S.T., S.R.H.), School of Medicine (H.V., C.M.), Temple University, Philadelphia, Pennsylvania.
authors: Sharven
authors: S
authors: Taghavi
authors: Senthil N
authors: SN
authors: Jayarajan
authors: Lucas M
authors: LM
authors: Ferrer
authors: Halley
authors: H
authors: Vora
authors: Conor
authors: C
authors: McKee
authors: Richard E
authors: RE
authors: Milner
authors: John P
authors: JP
authors: Gaughan
authors: Jay
authors: J
authors: Dujon
authors: Lars O
authors: LO
authors: Sjoholm
authors: Abhijit
authors: A
authors: Pathak
authors: Joseph F
authors: JF
authors: Rappold
authors: Thomas A
authors: TA
authors: Santora
authors: Steven R
authors: SR
authors: Houser
authors: Amy J
authors: AJ
authors: Goldberg
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output; D003404:Creatinine / Q000097:blood; D004195:Disease Models, Animal; D004632:Emergency Medical Services; D006439:Hemodynamics; D007442:Intubation, Intratracheal; D053208:Kaplan-Meier Estimate; D010100:Oxygen / Q000097:blood; D011175:Positive-Pressure Respiration; D011659:Pulmonary Gas Exchange; D012771:Shock, Hemorrhagic / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D013552:Swine; D014950:Wounds, Penetrating / Q000628:therapy
chemical_list: D002245:Carbon Dioxide; D003404:Creatinine; D010100:Oxygen