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Spontaneous neutrophil activation and the outcome of hemorrhagic shock in rabbits
J Barroso-Aranda1, R H Chavez-Chavez, G W Schmid-Schönbein
1Department of AMES-Bioengineering, University of California, San Diego, La Jolla 92093-0412.
Abstract:
Recent evidence suggests that an increase in the number of activated circulating polymorphonuclear neutrophils (PMNs), as measured by nitroblue tetrazolium reduction (NBT-positive PMNs), was closely associated with irreversibility in a rat modified Wiggers hemorrhagic shock model. The objective of this study was to utilize a similar model, but in a species with a different hematological profile, the rabbit, to investigate the correlation between the appearance of activated circulating PMNs and survival rate. Rabbits (n = 21) were maintained at 40 mm Hg arterial pressure for 3 hr and observed for 24 hr for survival. This protocol resulted in 33% mortality. There were no significant differences in the number of circulating PMNs before bleeding and during the hypotensive period for survivors and nonsurvivors. During the hypotensive period, fewer circulating NBT-positive PMNs were detected in survivors than in nonsurvivors (P less than 0.01). Since PMN activation was low in most of the rabbits before bleeding, the fatal outcome in this shock protocol was associated consistently with spontaneous PMN activation during the hypotensive period.
Insights
Activated polymorphonuclear neutrophils (PMNs) indicate poor outcomes in hemorrhagic shock. In rabbits, increased NBT-positive PMNs during hypotension correlated with non-survival, suggesting PMN activation as a key factor in shock fatality.
Area of Science:
- Immunology
- Physiology
- Critical Care Medicine
Background:
- Activated polymorphonuclear neutrophils (PMNs) are linked to irreversible shock.
- Nitroblue tetrazolium (NBT) reduction quantifies PMN activation.
Purpose of the Study:
- To investigate the correlation between activated PMNs and survival rate in a rabbit hemorrhagic shock model.
- To determine if PMN activation predicts outcomes in a different species.
Main Methods:
- Rabbits (n=21) underwent induced hypotension (40 mm Hg for 3 hours).
- Circulating PMN and NBT-positive PMN levels were monitored.
- Survival was observed for 24 hours post-hypotension.
Main Results:
- Overall mortality was 33%.
- No significant difference in total PMNs between survivors and non-survivors.
- Fewer NBT-positive PMNs were observed in survivors during hypotension (P < 0.01).
Conclusions:
- Spontaneous PMN activation during hypotension is associated with fatal outcomes in rabbits.
- Activated PMNs, indicated by NBT positivity, are a potential biomarker for shock irreversibility.
- Findings support the role of PMN activation in shock-related mortality across species.