title: Fluid resuscitation therapy in endotoxemic hamsters improves survival and attenuates capillary perfusion deficits and inflammatory responses by a mechanism related to nitric oxide.
abstract: BACKGROUND
  Relative hypovolemia is frequently found in early stages of severe sepsis and septic shock and prompt and aggressive fluid therapy has become standard of care improving tissue perfusion and patient outcome. This paper investigates the role of the nitric oxide pathway on beneficial microcirculatory effects of fluid resuscitation.
  
  
  METHODS
  After skinfold chamber implantation procedures and endotoxemia induction by intravenous Escherichia coli lipopolysaccharide administration (2 mg x kg(-1)), male golden Syrian hamsters were fluid resuscitated and then sequentially treated with L-Nω-Nitroarginine and L-Arginine hydrochloride (LPS/FR/LNNA group). Intravital microscopy of skinfold chamber preparations allowed quantitative analysis of microvascular variables including venular leukocyte rolling and adhesion. Macro-hemodynamic, biochemical and hematological parameters as well as survival rate were also evaluated. Endotoxemic hamsters treated with fluid therapy alone (LPS/FR group) and non-treated animals (LPS group) served as controls.
  
  
  RESULTS
  Fluid resuscitation was effective in reducing lipopolysaccharide-induced microcirculatory changes. After 3 hours of lipopolysaccharide administration, non-fluid resuscitated animals (LPS group) had the lowest functional capillary density (1% from baseline for LPS group vs. 19% for LPS/FR one; p <0.05). At the same time point, arteriolar mean internal diameter was significantly wider in LPS/FR group than in LPS one (100% vs. 50% from baseline). Fluid resuscitation also reduced leukocyte-endothelium interactions and sequestration (p <0.05 for LPS vs. LPS/FR group) and increased survival (median survival time: 2 and 5.5 days for LPS and LPS/FR groups, respectively; p <0.05). Nitric oxide synthase inhibition prevented these protective effects, while L-Arginine administration markedly restored many of them.
  
  
  CONCLUSIONS
  Our results suggest that the underlying mechanism of fluid therapy is the restoration of nitric oxide bioavailability, because inhibition of NOS prevented many of its beneficial effects. Nevertheless, further investigations are required in experimental models closer to conditions of human sepsis to confirm these results.
authors.affiliation: Department of Surgery, Division of Anesthesiology, Faculty of Medical Sciences, Rio de Janeiro State University, Boulevard 28 de Setembro, Rio de Janeiro, 77 - Vila Isabel, 20,551-030, RJ, Brazil. nivaldovillela@terra.com.br.
authors.forename: Nivaldo Ribeiro
authors.initials: NR
authors.lastname: Villela
authors.forename: Ana Olimpia Maia Teixeira
authors.initials: AO
authors.lastname: dos Santos
authors.forename: Marcos Lopes
authors.initials: ML
authors.lastname: de Miranda
authors.forename: Eliete
authors.initials: E
authors.lastname: Bouskela
mesh_terms: D000818:Animals; D002196:Capillaries / Q000503:physiopathology*; D006224:Cricetinae; D004195:Disease Models, Animal; D019446:Endotoxemia / Q000378:metabolism / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D004927:Escherichia coli Infections / Q000378:metabolism / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D005440:Fluid Therapy / Q000379:methods*; D018836:Inflammation Mediators / Q000378:metabolism*; D008070:Lipopolysaccharides; D008297:Male; D008647:Mesocricetus; D008833:Microcirculation; D009569:Nitric Oxide / Q000494:pharmacology / Q000502:physiology*; D012151:Resuscitation / Q000379:methods*; D012772:Shock, Septic / Q000378:metabolism / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D009569:Nitric Oxide