Effect of isovolemic hemodilution with 3% albumin on thrombus formation at venous microanastomosis in rats

Leech Therapy Protects Free Flaps against Venous Congestion, Thrombus Formation, and Ischemia/Reperfusion Injury: Benefits, Complications, and Contradictions

The use of free cutaneous or myocutaneous flaps in some surgeries, especially in reconstructive surgeries, is routine and imperative; nevertheless, it is controversial because of fear of flap loss due to tissue congestion and partial or complete necrosis. Different mechanisms are discussed in this process, and based on the involved mechanisms, various agents and approaches are suggested for flap salvage. Among these agents and strategies, leech therapy (hirudotherapy) can be a valuable complementary treatment; however, in this way, full attention should be given to all beneficial and harmful aspects to reach the best results. This study included a literature review of the essential complications following free tissue transfer and explained the effects of leech therapy for the respective complications. Based on the review of the literature, the essential complications following free tissue transfer were (I) venous obstruction and congestion, (II) delay in blood flow reestablishment, (III) ischemia/reperfusion injuries, and (IV) thrombus formation. Leech therapy can protect free flaps against the mentioned complications as a complementary treatment. Leech therapy is an appropriate complement, however, not a definite approach for flap salvage. Therefore, in some patients, other alternative methods or even flap removal may be a better option.

The effect of hemodilution on free flap survival: A systematic review of clinical and experimental studies

BACKGROUND

Acute normovolemic hemodilution (ANH) has been proposed as a microsurgical technique to improve blood flow in free flaps.

OBJECTIVE

Here, we present the first systematic review of clinical and experimental studies on the effect of ANH.

METHODS

We performed a systematic literature search of PubMed, Medline, the Cochrane Library, Google Scholar, and ClinicalTrials.gov using search strategies and a review process in agreement with the PRISMA statement and the Cochrane Handbook for systematic reviews of interventions. PICO criteria were defined before bibliometric processing of the retrieved articles, which were analyzed with the SYRCLE RoB tool for risk of bias and the GRADE scale for level of evidence.

RESULTS

We retrieved 74 articles from the literature search, and after processing according to PICO criteria, only four articles remained, all of which were experimental. The rating for risk of bias was uncertain according to SYRCLE RoB results, and the level of evidence was low according to GRADE evaluation.

CONCLUSIONS

There is no clinical evidence for the effect of ANH on microcirculation in free flaps, and experimental studies provide weak evidence supporting the use of hemodilution in reconstructive microsurgery.

Effect of Previous Irradiation on Vascular Thrombosis of Microsurgical Anastomosis: A Preclinical Study in Rats

BACKGROUND

The objective of the present investigation was to compare the effect of neoadjuvant irradiation on the microvascular anastomosis in cervical bundle using an experimental model in rats.

METHODS

One hundred forty male Sprague-Dawley rats were allocated into 4 groups: group I, control, arterial microanastomosis; group II, control, venous microanastomosis; group III, arterial microanastomosis with previous irradiation (20 Gy); and group IV, venous microanastomosis with previous irradiation (20 Gy). Clinical parameters, technical values of anastomosis, patency, and histopathological parameters were evaluated.

RESULTS

Irradiated groups (III and IV) and vein anastomosis groups (II and IV) showed significantly increased technical difficulties. Group IV showed significantly reduced patency rates (7/35) when compared with the control group (0/35). Radiotherapy significantly decreased the patency rates of the vein (7/35) when compared with the artery (1/35). Groups III and IV showed significantly reduced number of endothelial cells and also showed the presence of intimal thickening and adventitial fibrosis as compared with the control group.

CONCLUSION

Neoadjuvant radiotherapy reduces the viability of the venous anastomosis in a preclinical rat model with a significant increase in the incidence of vein thrombosis.

Animal model of rapid crystalloid infusion in rats

PURPOSE

To describe an animal model of rapid intravenous infusion with different volumes of crystalloid and discuss the clinical findings.

METHODS

Fifty six male Wistar rats were used, divided randomly in seven groups (n = 8). The rats of groups 1 to 6 received lactated Ringer's solution intravenously, in the rate of 25 ml/min, with different volumes proportional to blood volume (BV). The rats of group 0 were submitted to the same procedure, but did not receive the fluid (control group). The data included respiratory rate, heart rate, saturation of peripheral oxygen (SpO(2)) in two times (before and after the infusion), and upshots (respiratory arrest and death). Dunnett's test and ANOVA were used.

RESULTS

The clinical signs significantly changed in the 2, 2.5 and 3 fold BV groups. The respiratory arrest was observed in the 1.5, 2, 2.5 and 3 fold BV groups, but death was present only in 2.5 and 3 fold BV groups.

CONCLUSIONS

The infusion of crystalloid in the same volume of blood volume did not cause significant variation in respiratory and heart rate, saturation of peripheral oxygen and did not induce respiratory arrest. The infusion of a volume of 3 fold blood volume was lethal to all animals.

Comparative study of isovolemic hemodilution with 3% albumin, dextran-40, and prophylactic enoxaparin (LMWH) on thrombus formation at venous microanastomosis in rats

The objective of the present investigation was to compare the effect of isovolemic hemodilution with 3% albumin, dextran-40, and enoxaparin on the prevention of thrombosis in femoral vein microanastomosis using an experimental model in rats. Forty male Wistar rats were allocated into four groups: group 1, control, thrombogenic model without previous treatment; group 2, hemodiluted, thrombogenic model with previous hemodilution; group 3, dextran-40, thrombogenic model with dextran infusion (10 ml/kg), and group 4, enoxaparin, thrombogenic model with administration of enoxaparin (0.5 mg/kg/day). Hemostatic parameters, hematologic examinations, patency of anastomosis, and histopathological examination were evaluated. The hemostatic parameters were similar in the four groups studied. Group hemodiluted, dextran-40, and enoxaparin showed significantly reduced number of red blood cells and platelets as compared with the control group. The hemodilution significantly increased the patency rates of the vein at 20 min and 48 h. Dextran-40 and enoxaparin improved the patency of the vein only at 20 min, but failed to show a significant increase in the final patency at 48 h. After 48 h, the rate of venous thrombosis, as evaluated microscopically, was significantly decreased in hemodiluted animals (1/8) as compared with controls (10/10); in rats treated with dextran-40 (7/10) and enoxaparin (5/10) the rate of venous thrombosis was significantly higher as compared with rats of the group hemodiluted. Based on these observations, it can be concluded that hemodilution with albumin 3% was a safe and more adequate procedure than the use of the schemes of administration of dextran-40 and enoxaparin used in this study to prevent thrombus formation at femoral vein microanastomosis in rats. Since hemodilution promotes reduction in blood viscosity and in erythrocyte and platelet aggregation as well as dilution of the coagulation factors themselves, its use could provide better microcirculatory blood perfusion, decreasing the risk of thrombosis, and making possible safer microsurgical procedures.