Abstract: Study of Venous Congestion after Partial Limb Amputantion in Rats: Protective Effects of Tirofiban or Heparin in Secondary Ischemia

Venous thrombosis is the main complication of vascular microsurgery an early intervention is mandatory to rescue the flap, with a success rate of only 50% after surgical revision; microcirculation thrombosis, oxygen free radicals production and edema are the main elements of ischemia/reperfusion (I/R) injury, and protective therapies aim to mitigate these changes. Antiplatelets and anticoagulants are used in different organs to control this injury. In this study, in a partial hind limb amputation model submitted to global ischemia, it was tested the protective effect of Heparin or Tirofiban during secondary ischemia after venous congestion. Sixty rats divided in three groups of 20 animals each were operated; after global ischemia of 90 minutes each group was injected into the contra lateral femoral vein, one of the following solutions: 1 ml of saline solution NaCl 0,9% - control group (CG); 1ml of Heparin 200 UI/kg - experimental group 1 (G1); 1ml of Tirofiban 50 μg /ml - experimental group 2 (G2). Sixty minutes of limb reperfusion was performed, and a secondary period of limb ischemia started with the clamping of the femoral vein only (limb congestion) which lasted for 90 minutes (secondary ischemia). After that, the vein clamp was removed and a 60-minute reperfusion period was observed; at the end of the second reperfusion period, the right gastrocnemius muscle was removed and fixed in 10% formaldehyde, animals were euthanized with a lethal dose of Pentobarbital. Muscle fibers were scored as uninjured or injured based on the morphology of individual fibers; interstitial edema and bleeding were graded on a four-point scale. The control group had more damaged muscle cells 54.6 ± 10.6% when compared to heparin 24.7 ± 11.7% and tirofiban 24.6 ± 8.6, all reached statistical significance (p<0.001); These comparisons were analysed using ANOVA and post-hoc Tukey. The single use of Heparin or Tirofiban showed a protective effect on venous congestion after global ischemia. When evaluating the edema, none experimental group had statistically lower rates than the CG, whilst both drugs reduced the extravasation of red blood cells compared with the control group (p <0.001).

Abstract licence: CC BY-NC-ND

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