title: Superimposed traumatic brain injury modulates vasomotor responses in third-order vessels after hemorrhagic shock.
abstract: BACKGROUND
  Traumatic brain injury (TBI) and hemorrhagic shock (HS) are the leading causes of death in trauma. Recent studies suggest that TBI may influence physiological responses to acute blood loss. This study was designed to assess to what extent superimposed TBI may modulate physiologic vasomotor responses in third-order blood vessels in the context of HS.
  
  
  METHODS
  We have combined two established experimental models of pressure-controlled hemorrhagic shock (HS; MAP 50 mmHg/60 min) and TBI (lateral fluid percussion (LFP)) to assess vasomotor responses and microcirculatory changes in third-order vessels by intravital microscopy in a spinotrapezius muscle preparation. 23 male Sprague-Dawley rats (260-320 g) were randomly assigned to experimental groups: i) Sham, ii) HS, iii) TBI + HS, subjected to impact or sham operation, and assessed.
  
  
  RESULTS
  HS led to a significant decrease in arteriolar diameters by 20% to baseline (p < 0.01). In TBI + HS this vasoconstriction was less pronounced (5%, non-significant). At completed and at 60 minutes of resuscitation arteriolar diameters had recovered to pre-injury baseline values. Assessment of venular diameters revealed similar results. Arteriolar and venular RBC velocity and blood flow decreased sharply to < 20% of baseline in HS and TBI + HS (p < 0.01). Immediately after and at 60 minutes of resuscitation, an overshoot in arterial RBC velocity (140% of baseline) and blood flow (134.2%) was observed in TBI + HS.
  
  
  CONCLUSIONS
  Superimposed TBI modulated arteriolar and venular responses to HS in third-order vessels in a spinotrapezius muscle preparation. Further research is necessary to precisely define the role of TBI on the microcirculation in tissues vulnerable to HS.
authors.forename: Bo
authors.initials: B
authors.lastname: Chen
authors.forename: Manuel
authors.initials: M
authors.lastname: Mutschler
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Yuan
authors.forename: Edmund
authors.initials: E
authors.lastname: Neugebauer
authors.affiliation: Department of Pathophysiology, Key Laboratory for Shock and Microcirculation Research, Southern Medical University (SMU), Tong He, 510515 Guangzhou, People's Republic of China. bing@smu.edu.cn.
authors.forename: Qiaobing
authors.initials: Q
authors.lastname: Huang
authors.forename: Marc
authors.initials: M
authors.lastname: Maegele
mesh_terms: D000818:Animals; D001160:Arterioles / Q000503:physiopathology*; D001930:Brain Injuries / Q000150:complications* / Q000503:physiopathology; D004195:Disease Models, Animal; D005440:Fluid Therapy / Q000379:methods; D008297:Male; D008833:Microcirculation / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000502:physiology*; D012151:Resuscitation / Q000379:methods; D012462:Saline Solution, Hypertonic / Q000627:therapeutic use; D012771:Shock, Hemorrhagic / Q000150:complications* / Q000503:physiopathology / Q000628:therapy; D014664:Vasodilation / Q000502:physiology*; D014699:Venules / Q000503:physiopathology*
chemical_list: D012462:Saline Solution, Hypertonic