Cold Realities: How Science and Speed Save Lives in Frostbite Emergencies

Headshot photo of internationally recognized researcher, Rachel Nygaard, PhD, who specializes in frostbite, burn, and violent injury prevention.

Living in Minnesota is not for the faint of heart, with temperatures frequently plummeting to 20 degrees below zero F, and with wind chills, it can drop as low as 50 degrees below zero F. With extreme temperatures such as these, it’s no wonder that frostbite becomes a problem during the winter months. However, with the help of internationally recognized researcher Rachel Nygaard, PhD, who specializes in frostbite, burn, and violent injury prevention, she hopes to mitigate the severity of frostbite seen in Hennepin Healthcare’s patients.

Frostbite is not the same as a burn. “Minor frostbite may involve only the upper layers of skin, but in severe frostbite, the damage occurs deep in the tissue. This is due to blood clots [forming] in the tissue, cutting off blood supply to the fingers, toes, and/or limbs impacted, causing the tissue to die due to lack of oxygen,” explained Dr. Nygaard.

Source: National Oceanic and Atmospheric Administration (NOAA) and National Weather Service (NWS), Wind Chill Chart. Public domain.

According to the National Institutes of Health (NIH), National Library of Medicine, “Frostbite, also known as freezing cold injury (FCI), is tissue damage as a result to cold exposure, occurring at temperatures below zero degrees C (32 degrees F). Prolonged duration and lower temperatures increase the likelihood and extent of the injury. Frostbite tends to occur when the body is exposed to intense cold, resulting in vasoconstriction. The resulting decrease in blood flow fails to deliver heat to the tissues and eventually leads to ice crystal formation. Body parts most prone to frostbite include the feet, hand[s], ears, lips, and nose.”

Frostbite impacts certain populations more than others, such as:

• People experiencing homelessness
• People experiencing an altered mental state
• Winter sports enthusiasts
• Young children
• Senior citizens
• People with comorbidities
• Young adults experimenting with alcohol or drugs

The number of cases seen by Hennepin Healthcare’s Emergency Department each year varies by the intensity of Minnesota’s winters; some winters can be mild, and some can be brutally cold. For example, data from electronic patient records in recent years revealed that 2019-2020 had 317 first through fourth degree frostbite and frostnip encounters. In contrast, 2021-2022 almost tripled the number of first through fourth degree encounters of frostbite and frostnip at 928 total.

Chilling Facts, Warm Solutions: Advancing Frostbite Care

To better measure the impact of frostbite interventions on outcomes, Dr. Nygaard and colleagues developed an evaluative tool called the Hennepin Frostbite Score that is used widely.

Hennepin Healthcare Frostbite Score: Quantification tool to assess severe frostbite injury outcomes.

“It is a tool to assess outcomes – it isn’t a clinical grading system. Essentially, it is a standard measure of how much tissue is impacted by frostbite, and then you assess how much is amputation, creating a percent salvage,” said Dr. Nygaard.

Since developing the Hennepin Frostbite Score, this tool has helped doctors discover that each hour delay in treatment results in a reduction of limb salvage by 28%.

When a person is warming up from frostbite, doctors call this warm ischemia (not enough blood flow to a part of the body), a critical time when thawed tissue still lacks proper blood flow. Blood clots in the microvasculature (the smallest blood vessels in the body) can prevent blood from reaching the damaged tissue, creating what’s called ischemic tissue. The longer blood flow is interrupted, the lower the chance of saving the tissue.

“Ultimately, what is translated on the clinical side is the acknowledgement that this is an emergency, the tissue is at risk for amputation, so essentially complete loss if you don’t urgently manage these patients with the pharmacological interventions we have. And so, since that paper [in the Journal of Burn Care & Research], a lot more centers have been treating this more urgently and have seen better outcomes because of that,” explained Dr. Nygaard.

Inside the Fight Against Frostbite: Treatments That Work

According to Hennepin Healthcare’s Burn Center and Acute Burn Clinic, first aid for frostbite is as follows:

• Avoid rubbing the area, especially with snow, which will worsen the injury.
• Avoid thawing an area if you are far from help or if there is a chance of refreezing, as this will cause more damage.
• Don’t walk on frostbitten feet or use a frostbitten area. If you must walk, the feet will suffer less damage if left frozen or padded. If feet are thawed, have someone carry you, if possible.
• If you are in a permanent shelter and can thaw a frostbitten area:
  • Immerse the area for 20-45 minutes in tepid (98° - 104°) water. Avoid using hot water, which may burn the area, causing more damage. As the area thaws, it will turn pink or bright red, and sensation may return.
  • Do not put salves or creams on the frostbite.
  • Protect the frostbite area from refreezing and seek medical attention.

Pharmacological treatments for frostbite

The four medical stages of frostbite.

The main pharmacological intervention that Hennepin Healthcare uses in treating severe frostbite injuries is systemic thrombolytic therapy. Systemic thrombolytic therapy is typically used for severe frostbite injuries by administering an intravenous (IV) clot-dissolving medication to restore blood flow to prevent tissue loss or amputation.

Hennepin Healthcare was among the first U.S. medical providers to use thrombolytic therapy for frostbite in 2007, building off the work of former Hennepin County Medical Center (HCMC) Burn Director John Twomey, MD. Dr. Twomey repurposed a medication originally used in stroke care for brain clots to treat blood clots in frostbitten hands and feet. Using this treatment for frostbite, he created a thrombolytic protocol that’s still in use today.

Frostbite is an emergency

Dr. Nygaard has a few hopes for the future of frostbite research. “The real gaps are trying to get treatments to patients early. Educating providers at smaller centers and people in general that frostbite is an emergency, and you could lose fingers, toes, or entire limbs. [Frostbite] is an emergency—if you have the injury, have warmed up, and still can’t feel in that finger or toe, or it looks like there isn’t blood flow, seek emergency care.”

Further Reading: Learn More about Frostbite Research

• What is Frostbite? - https://hennepinhealthcare.org/services/burn-center-and-acute-burn-clinic/what-frostbite
• Frostbite Interventions – THOR Conference 2024
• “Time Matters in Severe Frostbite: Assessment of Limb/Digit Salvage on the Individual Patient Level” – Journal of Burn Care & Research
• Frostbite: From Napoleonic era treatments to the first FDA approved frostbite drug - American Chemical Society – Tiny Matters podcast
• Rachel Nygaard's Research Portfolio
• Hennepin Trauma Surgery Research
• Hennepin Healthcare Burn Center and Acute Burn Clinic - https://hennepinhealthcare.org/services/burn-center-and-acute-burn-clinic