Splenectomy Versus Sham Splenectomy in a Swine Model of Controlled Hemorrhagic Shock.

INTRODUCTION: Splenectomy is controversial in acute hemorrhagic shock models. OBJECTIVE: To compare splenectomized (SP) versus sham-splenectomized (SSP) swine during acute controlled hemorrhage. METHODS: Twenty-six male Landrace White swine (mean body weight ±â€Šstandard deviation, 33.8 ±â€Š2.9 kg) were used. Ethics approval was obtained. Landrace swine underwent splenectomy (n = 13) or sham-splenectomy (n = 13), were bled to mean arterial blood pressure (MAP) of 40 mm Hg, which was held for 60 min, given 125 mL IV RescueFlow, held for a further 60 min, given whole blood, and held for a final 60 min. Tissue oxygen saturation, thromboelastography, oncotic pressure, urine volume and specific gravity, complete blood count, serum chemistry, body temperature, hematocrit, total solids, arterial and mixed venous blood gas, bispectral index, SAP, MAP, DAP, cardiac index, total blood volume (TBV) removed and returned, rate of hemorrhage and transfusion, spleen weight, heart rate (HR), arterial pH, lactate, PaO2, PaCO2, respiratory rate, cranial mesenteric and renal artery blood flow were recorded. Groups were compared using two-way ANOVA with post hoc Bonferroni (P < 0.05) for repeated measures or t test for non-repeated measures. RESULTS: Compared with the SSP swine, SP swine had higher HR post-splenectomy for the duration of the experiment (P < 0.03), and higher hematocrits at 15 and 60 min post splenectomy (P < 0.01, P < 0.001, respectively). SSP swine had greater TBV removed during hemorrhage (P < 0.01); however, when blood loss based on splenic weight was considered, TBV removed was similar between groups. CONCLUSION: Splenectomy likely accounts for the transient increase in hematocrit and the higher HR in SP swine prior to hemorrhage, and the differences in TBV removed between the two groups during hemorrhage. With a fixed end point model using a moderate rate of acute hemorrhage and an MAP of 40 mm Hg, splenectomy is not necessary and may confound results.

Comparison of arterial and venous whole blood clot initiation, formation, and strength by thromboelastography in anesthetized swine.

Thromboelastography (TEG) analysis was used to determine if differences exist between venous and arterial samples in anesthetized swine, using identical sampling techniques for each of the samples. We hypothesized that TEG parameters would not differ between native whole blood venous and arterial samples. Thirty male Landrace swines were included in the study. Both the femoral artery and vein were catheterized using standard cut-down techniques and with identically sized catheters to rule out any catheter size effects on the results. Standard TEG parameters for native whole venous and arterial blood samples (r, K, α, MA, G, and coagulation index) were measured or calculated, and t-test or Mann-Whitney rank-sum test used for comparison when appropriate. Significant differences were detected for r (venous < arterial), K (venous < arterial), α (venous > arterial), and coagulation index (venous > arterial) TEG parameters. No significant differences were measured for MA or G. These differences are important, especially when temporal changes in TEG are utilized to monitor patient stability and fluid therapy protocols using trends in coagulation properties. Taken together, these results suggest that clots are more likely to form at a faster rate in venous samples compared to arterial samples, but the overall clot strength does not differ. Therefore, if TEG analysis is being used to monitor coagulation profiles in a patient, care should be taken to use the same site and technique if results are to be used for comparative purposes.