Neutrophil oxidative burst evaluation during acute normovolemic hemodilution

Introduction

In recent years there has been increasing evidence that resuscitation strategies with different fluids can have widely divergent impacts on the immune response and neutrophil activation. This study was undertaken to determine the neutrophil's oxidative burst in a swine model during the acute normovolemic hemodilution (ANH) procedure with hydroxyethyl starch (HES), normal saline solution (NSS) or gelatin (GEL).

Methods

Twenty-four pigs were anesthetized, instrumented and randomized into four groups: Control, ANH + HES, ANH + NSS and ANH + GEL. Animals in the ANH group were submitted to acute normovolemic hemodilution to a target hematocrit of 15% with volume replacement performed with HES 130/0.4 and GEL at a 1:1 ratio and NSS at a 3:1 ratio. The withdrawn blood was returned to the animals 120 minutes after the end of hemodilution. Neutrophil oxidative burst was performed with blood samples collected from the femoral vein at the following time points: before ANH (baseline), after instrumentation (INST), immediately after ANH (H), 60 minutes after ANH (60H), 120 minutes after ANH (120H), 60 minutes after blood infusion (60BI) and 120 minutes after blood infusion (120BI) and determined with a flow cytometer. A t test was performed to evaluate differences between groups. P < 0.05 was considered statistically significant.

Results

Between groups there were significant differences at time point H between Control (25.75 ± 8.45) and HES (60.61 ± 10.49; P < 0.01), between Control and NSS (55.94 ± 10.38; P < 0.05), and between Control and GEL (68.42 ± 27.83; P < 0.01). At time point 60H, the differences were between Control (34.48 ± 8.11) and HES (54.15 ± 12.49; P < 0.01). In 120H, Control (29.05 ± 9.39) and HES (45.20 ± 5.80; P < 0.05) and NSS (46.18 ± 9.42; P < 0.05) showed significant differences. Sixty minutes after blood infusion, only HES (38.57 ± 7.89; P < 0.05) was different from Control (26.46 ± 7.54).

Conclusion

Fluid replacement immediately after induced ANH increased inflammation expressed by oxidative burst activity without significant differences among them.