Fluid support worsens outcome and negates the benefit of protective antigen-directed monoclonal antibody in a lethal toxin-infused rat Bacillus anthracis shock model

Kevin Sherer, Yan Li, Xizhong Cui, Xuemei Li, Mani Subramanian, Michael W. Laird, Mahtab Moayeri, Stephen H. Leppla, Yvonne Fitz, Junwu Su, Peter Q. Eichacker

Research output: Contribution to journalArticle


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. DESIGN: Prospective controlled animal study. SETTING: Animal research laboratory. SUBJECTS: Sprague-Dawley rats (n = 539). INTERVENTIONS: 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. MEASUREMENTS AND MAIN 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 ≤ .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.

Original languageEnglish (US)
Pages (from-to)1560-1567
Number of pages8
JournalCritical Care Medicine
Issue number6
Publication statusPublished - Jun 2007
Externally publishedYes



  • Bacillus anthracis
  • Fluids
  • Lethal toxin
  • Rodent
  • Sepsis
  • Treatment

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine

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