Fluid support worsens outcome and negates the benefit of protective antigen-directed monoclonal antibody in a lethal toxin-infused rat Bacillus anthracis shock model.
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.
Sherer
Kevin
K
Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD, USA.
Li
Yan
Y
Cui
Xizhong
X
Li
Xuemei
X
Subramanian
Mani
M
Laird
Michael W
MW
Moayeri
Mahtab
M
Leppla
Stephen H
SH
Fitz
Yvonne
Y
Su
Junwu
J
Eichacker
Peter Q
PQ
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
D000911:Antibodies, Monoclonal; D008070:Lipopolysaccharides; D012965:Sodium Chloride