Report from SIR: Lytic therapy saves limbs from severe frostbite

March 19, 2008

A mix of thrombolytics and antispasmodic drugs is safely taking the chill out of frostbite for Minnesotans caught outside in the state’s infamously frigid winter. Preliminary results with moderate success suggest the treatment could help avoid amputations as its application spreads to more icebox states.

A mix of thrombolytics and antispasmodic drugs is safely taking the chill out of frostbite for Minnesotans caught outside in the state's infamously frigid winter. Preliminary results with moderate success suggest the treatment could help avoid amputations as its application spreads to more icebox states.

The findings are relevant to hikers, mountaineers, soldiers, adventurers, homeless people, and nearly everyone who takes pleasure in or has the misfortune of experiencing long exposure to the cold. Frostbite is treated by immersing the affected area in warm water when there is no risk of refreezing the tissue. Thawing, however, can lead to arterial spasm, blood clotting, gangrene, and amputation.

Using a combination of intra-arterial thrombolysis and vasodilator infusion, physicians can reopen blocked arteries, even the smallest ones, saving patients' fingers and toes, said principal investigator Dr. George R. Edmonson, an interventional radiologist at St. Paul Radiology.

Over three consecutive winters, Edmonson and colleagues prospectively enrolled six frostbite patients aged 18 to 65. All subjects received intra-arterial infusions of tenectaplase with papverine and intravenous heparin. Their results were compared with a retrospective review of 11 patients treated with intra-arterial retaplase in previous years. Edmonson and colleagues found the combination treatment significantly improved outcomes in approximately 80% of patients.

On average, and compared with the group of 11 patients treated with RPA, intra-arterial thrombolysis with vasodilator provided almost 50% successful limb salvage. The treatment improved patient outcomes in about 80% of the cases, with significant improvement within one to three days of treatment, according to Edmonson.

"For half our patients who received the clot-busting drug, the technique worked quite beautifully, saving all fingers, hands, toes, and feet that otherwise would have been lost," he said.

Three of six patients treated with tenectaplase for 16 frostbitten toes or fingers did not require amputation. Two patients in this group with 20 affected digits underwent one great toe and three transmetatarsal amputations.

One patient did not complete treatment because of intubation. Eight fingers were amputated, but both thumbs were saved.

Tenectaplase dilutes better in the bloodstream and reaches microvasculature faster than other drugs, but it is also prone to more complications. More work is needed to understand the causes of failures observed during the preliminary study and to optimize the treatment protocol, Edmonson said.