Cytokine levels evaluation during acute isovolemic anemia

Introduction

To date there is poor evidence that documents the benefit of red blood cell transfusion on clinical outcome. Acceptance of a lower transfusion trigger in the perioperative period requires detailed information regarding the effects of volume replacement in different organs and systems. Since fluids can have a widely divergent impact on the immune response, this study was undertaken to determine the cytokine levels in a model of acute isovolemic anemia (AIA) with hydroxyethyl starch (HES) and gelatin (GEL).

Methods

Twenty-one pigs were anesthetized, instrumented and randomized into three groups: Control, HES and GEL. Animals in the HES and GEL groups were submitted to acute isovolemic anemia to a target hematocrit of 15% with volume replacement performed with HES 130/0.4 and GEL at a 1:1 ratio. The withdrawn blood was returned to the animals 120 minutes after the end of AIA. TNF, IL-1, IL-6 and IL-10 measurements were performed with blood samples collected at the femoral vein at the following time points: Baseline, after instrumentation (INST), immediately after AIA (AIA), 60 minutes after AIA (60AIA), 120 minutes after AIA (120AIA), 60 minutes after blood infusion (60BI) and 120 minutes after blood infusion (120BI). The cytokines were measured in serum by a commercially available ELISA with specific monoclonal antibodies. Two-way analyses of variance (ANOVA) and a Tukey test were used to assess its significance (P < 0.05).

Results

TNF varied significantly among the groups in different time points (AIA: Control, 91 ± 16 and GEL, 221 ± 61; P < 0.05; 60AIA: Control, 76 ± 15; HES, 172 ± 42; P < 0.05 and GEL, 323 ± 77; P < 0.001; 120AIA: Control, 98 ± 6 and GEL, 304 ± 66; P < 0.01; 120BI: Control, 71 ± 7 and GEL, 211 ± 71; P < 0.05). In relation to IL-1, only in the GEL group (224 ± 56) was verified a statistical significant at time point 60AIA when compared with Control (84 ± 17; P < 0.05). When IL-6 levels were studied, GEL presented a statistically significant at 60AIA (GEL, 331 ± 65) when compared with Control (146 ± 19; P < 0.05). Serum IL-10 levels in GEL-treated animals were statistically significantly elevated at 60AIA (Control, 17 ± 3 and GEL, 46 ± 12; P < 0.01) and 120BI (Control, 21 ± 5 and GEL, 59 ± 11; P < 0.05).

Conclusions

Fluid replacement influences the cytokine measurements during acute isovolemic anemia expressed by serum TNF, IL-1, IL-6 and IL-10 increases, especially in GEL group.