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| |  Limb Salvage in Severe Frostbite Possible Through Intra-Arterial Thrombolysis After Vasodilator Infusion: Presented at SIR By Crina Frincu-Mallos, PhD WASHINGTON, DC -- March 25, 2008 -- Limb amputation due to frostbite can be prevented by using angiography to visualize loss of blood flow in the limbs affected, followed by intra-arterial thrombolysis and vasodilator infusion to dissolve the blood clots and relax the arterial muscular walls, researchers reported here at the Society of Interventional Radiology (SIR) 33rd Annual Scientific Meeting. Severe frostbite injuries result in ischaemia and severe blistering, with damage occurring deep in the muscles, nerves, and blood vessels. The blockage of blood flow leads in severe cases to gangrene and loss of limbs. The standard treatment for frostbite -- rewarming of the affected area and, in some cases, amputation -- has not changed in decades. In this prospective trial presented on March 16, George R. Edmonson, MD, Interventional Radiologist, St. Paul Radiology, Regions Hospital, St. Paul, Minnesota, and colleagues compared the benefit of using tenectaplase (TNK) versus retaplase (RPA) to improve limb salvage rates. "The drugs are infused through catheters in the upper arms or legs," explained Dr. Edmonson. "TNK is degraded more slowly in the bloodstream and affects the normal clotting proteins less than similar agents; therefore, bleeding risk may be lower." The trial was designed to see if the greater plasma stability of TNK compared with RPA would produce better results. Twelve patients, aged 18 to 65 years, received TNK infusions over a 48-month period, while another 12 patients received RPA infusions over a 24-month period. The Institutional Review Board limited access to patient records to a 24-month period in the case of the RPA-treated patients. Dr. Edmonson, who has been treating an average of 6 to 10 frostbite patients each winter for the past 10 years, said the predictive arterial sign of digit salvage is the presence of distal tuft blush. Using diagnostic arteriography, "we can assess for small-vessel occlusion and loss of distal tuft blush at the tips of digits," he explained. Patients received intra-arterial TNK at 0.25 mg/hr/limb for up to 72 hours. In addition, they also received papaverine at a dose of 30 mg/hr/limb and heparin at 500 mcL/hr. For the first 24 +- 6 hours, all 6 patients were monitored with arteriography during TNK infusion. The angiographic endpoint was defined as thrombolysis and restoration of blood flow through at least 1 digital artery, to re-establish the distal tuft blush. The clinical endpoint was loss of damaged digits at 45-days follow-up, said Dr. Edmonson. Eight of the 12 patients treated with TNK had a complete response, with 16 digits responding to treatment and saved from amputations. Two patients, with a total of 20 digits affected, underwent 1 great toe and 3 transmetatarsal amputations. One patient could not receive treatment immediately due to acute alcohol withdrawal requiring intubation, and lost 8 fingers, saving both thumbs. One patient did not respond to treatment. "To date, 8 of 12 TNK-treated patients (68%) were saved from amputation," noted Dr. Edmonson. Among the 12 patients treated with RPA who were evaluated, 2 patients had to be excluded from the comparison. The remaining 10 patients, aged 14 to 77 years, had 16 limbs treated with various doses of RPA and papaverine. Six patients recovered with no amputations, 4 patients lost 31 digits at 45 days of follow-up, while 2 patients had more distal amputation than anticipated. None of the patients treated with either TNK or RPA experience any bleeding, according to the researchers. "With both groups, the patients' affected limbs, fingers, and toes, responded [to the treatment] with significant improvement," said Dr. Edmonson in a press conference. "TNK offers a modest improvement over RPA, and both are much better than traditional treatment," he said. Intra-arterial thrombolysis and vasodilator infusion was demonstrated to be safe and beneficial for limb salvage in patients with severe frostbite. "More work is needed to understand the causes of [treatment] failures and to optimise the treatment protocol," concluded Dr. Edmonson. For instance, the researchers are considering increasing the dose of heparin in order to reduce rethrombosis, and to add antiplatelet drugs to reduce clot formation. In the future, the team is considering a randomised trial between intravenous and intra-arterial administration of drugs in this patient population.
[Presentation title: Intra-Arterial Thrombolytic Therapy for Limb Salvage in Severe Frostbite. Abstract 52]
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