Periadventitial delivery of heparin in the prevention of microvenous thrombosis

In Search of Optimal Practice: A Retrospective Comparative Study of Single- Versus Dual-Venous Anastomosis in Microvascular Flaps

Background In the current era of reconstructive surgery, microvascular free flap transfers are the most popular reconstructive procedures performed. The main reason for the failure of the flap and re-exploration is venous thrombosis. Traditionally, most surgeons prefer performing two-vein anastomoses. There is insufficient literature to support that dual-venous anastomosis is better than single-venous anastomosis. In this study, we compared the success rate of single-venous anastomosis with dual-venous anastomosis of different free flap reconstructions. Methodology The retrospective cohort study was conducted with a total of 101 patients. Eighty-three were in the one-vein group, and the remaining 18 were in the two-vein group. Outcomes were compared between the two groups regarding re-exploration and flap failure. Results The overall success rate of free flap reconstruction was 96%. Among the 101 free flaps, 16 flaps had signs of venous compromise and were re-explored. Out of the 16 flaps, 11 flaps (13.2%) were in the one-vein group, and 5 flaps (27.7%) were in the two-vein group. In the two-vein group, 100% of the flaps were salvaged, and in the one-vein group, only 63% of the flaps were salvaged after re-exploration. There was no statistically significant difference between the one-vein group and the two-vein group concerning re-exploration.  Conclusions The rate of re-exploration was lower in the one-vein group when compared to the two-vein group. However, this difference was not statistically significant. Hence, a single-vein anastomosis is sufficient for a successful microvascular free flap. However, the rate of flap salvage is better with two-vein anastomosis if there is venous congestion.

Improved microvessel repair: laser welding with an anti-thrombotic solder

BACKGROUND AND OBJECTIVES

Concentrated protein solutions can be used as thermally polymerized solders in laser welding. Solders supplemented with biologically active chemicals may provide in situ drug delivery for localized therapeutics. These studies characterize a serum albumin (SA) solder containing heparin, designed to reduce microvascular thrombosis rates.

STUDY DESIGN/MATERIALS AND METHODS

Samples of heparin added to 30% SA to obtain heparin-to-albumin molar ratios (HAMR) of 4:1 and 2:1 were thermally polymerized, and heparin release into saline was measured. Using a rat thrombosis model, patency was determined for suture, and 0 U/ml (control), 2.5 U/ml, 50 U/ml heparin solder repairs.

RESULTS

Heparin release was five times higher for 4:1 than 2:1 HAMR solder acutely, but was equivalent after 2 days. Animal patency rates were: 50% suture, 0% control, 50% low heparin, 66% high heparin (P < 0.05 vs. control).

CONCLUSIONS

Solders incorporating heparin should provide in situ anti-thrombotic therapy reducing the risk of microvascular thromboses.

Experimental prevention of free flap thrombosis. II: Normovolemic hemodilution for thrombosis prevention

A microvascular free flap failure model consisting of raising an epigastric groin flap on the femoral pedicle, while cutting the femoral artery, twisting it around the femoral vein and resuturing it, has been previously described. As it was being evaluated, normovolemic hemodilution as a means to prevent thrombosis was simultaneously assessed using an additional experimental group. Twenty percent of the blood mass of each rat was taken and replaced with a hydroxyethyl starch solution immediately before surgery. Only 14 out of 20 anastomoses presented with thrombosis (13 venous and one mixed), as opposed to 19 out of 20 animals operated on without hemodilution (P< 0.05). Normovolemic hemodilution appears to be an effective method of reducing microvascular free flap failure.