title: Fluid support worsens outcome and negates the benefit of protective antigen-directed monoclonal antibody in a lethal toxin-infused rat Bacillus anthracis shock model.
abstract: OBJECTIVE
  The aim of this study was to test the effects of normal saline treatment either alone or in combination with protective antigen-directed monoclonal antibody in a lethal toxin-infused rat model of anthrax sepsis.
  
  
  METHODS
  Prospective controlled animal study.
  
  
  METHODS
  Animal research laboratory.
  
  
  METHODS
  Sprague-Dawley rats (n = 539).
  
  
  METHODS
  We initially tested the efficacy of three normal saline doses (5, 10, or 20 mL/kg/hr intravenously for 24 hrs) or none (controls) started when rats were treated with either lethal toxin (24-hr infusion) or, for comparison, lipopolysaccharide (24-hr infusion) or Escherichia coli (intravenous bolus). We then investigated delaying normal saline for 6 hrs or combining it with protective antigen-directed monoclonal antibody following lethal toxin challenge.
  
  
  RESULTS
  Dose did not alter the effects of normal saline with any challenge (p not significant for all) or when combined with protective antigen-directed monoclonal antibody, so this variable was averaged in analysis. In initial studies, normal saline decreased mortality (mean hazards ratio of survival +/- SE) significantly with E. coli challenge (-0.66 +/- 0.25, p = .009 averaged over normal saline dose) but not lipopolysaccharide (-0.17 +/- 0.20). In contrast, normal saline increased mortality significantly with lethal toxin (0.69 +/- 0.20, p = .001) in a pattern different from E. coli and lipopolysaccharide (p <or= .002 for each). In subsequent studies, normal saline alone once again increased mortality (0.8 +/- 0.3, p = .006), protective antigen-directed monoclonal antibody alone reduced it (-1.7 +/- 0.8, p = .03), and the combination had intermediate effects that were not significant (0.04 +/- 0.3).
  
  
  CONCLUSIONS
  These findings raise the possibility that normal saline treatment may actually worsen outcome with anthrax lethal toxin. Furthermore, lethal toxin-directed therapies may not be as beneficial when used in combination with this type of fluid support.
authors: Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD, USA.
authors: Kevin
authors: K
authors: Sherer
authors: Yan
authors: Y
authors: Li
authors: Xizhong
authors: X
authors: Cui
authors: Xuemei
authors: X
authors: Li
authors: Mani
authors: M
authors: Subramanian
authors: Michael W
authors: MW
authors: Laird
authors: Mahtab
authors: M
authors: Moayeri
authors: Stephen H
authors: SH
authors: Leppla
authors: Yvonne
authors: Y
authors: Fitz
authors: Junwu
authors: J
authors: Su
authors: Peter Q
authors: PQ
authors: Eichacker
mesh_terms: D000818:Animals; D000881:Anthrax / Q000150:complications*; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D001408:Bacillus anthracis; D003131:Combined Modality Therapy; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli; D005440:Fluid Therapy / Q000379:methods*; D008070:Lipopolysaccharides; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012772:Shock, Septic / Q000209:etiology / Q000401:mortality / Q000628:therapy*; D012965:Sodium Chloride / Q000627:therapeutic use
chemical_list: D000911:Antibodies, Monoclonal; D008070:Lipopolysaccharides; D012965:Sodium Chloride