Further investigation of secondary venous obstruction

Abstract

The first ischemic insult a tissue suffers is primary (1 degree). A second ischemic episode, such as thrombosis after free tissue transfer may be regarded as secondary (2 degrees) ischemia. The current study investigated 2 degrees ischemia in rodent epigastric flaps. Flaps were elevated in 50 Sprague-Dawley rats: group 1 had 5 hours 1 degree venous ischemia induced by placement of microvascular clamps; group 2 was like group 1, except venous continuity was re-established by venous anastomosis after resection of the venous segment previously microclamped; group 3 had 15 minutes of 1 degree ischemia, 24 hr later 5 hr of 2 degrees venous ischemia was induced by placement of microvascular clamps; group 4 was like group 3, except the venous segment was excised. Necrosis was evaluated on postoperative day 7. Both secondary ischemic groups had significantly less flap survival than the corresponding primary ischemic groups (P less than 0.001 for both). Resection of a portion of the vein and subsequent microanastomosis did not reduce flap survival (NS). Secondary venous ischemia of 5-hr duration is poorly tolerated by rodent skin flaps. There was no difference in flap survival in those flaps whose veins were clamped for 5 hr compared to those flaps whose clamped venous segments were resected and re-anastomosed.

Effect of the Delay Phenomenon on Survival of Rat Island Skin Flaps with Total Venous Occlusion

“…The time between primary and secondary venous ischemia is important, and flap survival is directly proportional to the duration of this period. 15,16 The rate of necrosis is reported as 100 percent in flaps with total venous occlusion, 17,18 as our study also demonstrated. After the delay, we achieved a partial survival rate (60±15 percent), which might be clinically important.…”

Ischemia/reperfusion injury in microvascular surgery

“…25 In experimental animals undergoing myocutaneous flaps, a period of secondary ischemia produced significant changes not seen in flaps that underwent a similar period of primary ischemia only. For various reasons (thrombosis, vasospasm, ischemia/ reperfusion injury), perfusion to the flap may be interrupted after the anastomoses have been completed and the flap reperfused.…”

Ex Vivo Machine Thrombolysis Reduces Rethrombosis Rates in Salvaged Thrombosed Myocutaneous Flaps in Swine

“…Previous research has discovered that this second period of ischemia is the most damaging to the flap, leading to partial or even complete flap loss. 32 Increased rethrombosis rates might be the result of inadequate lytic effect of solely a manual injection. Previous case series reported that intraarterial and intravenous thrombolysis is potentiated by directed local administration of the thrombolytics, increasing their bioavailability at the site of the thrombus.…”