By Ted Paisley, MD
Winter is my favorite season in Utah. Snowstorms, skiing, and outdoor adventures abound. This weekend was a great example. My family managed to fit in a giant slalom race at Park City, a cross-country skate race at Soldier Hollow, and a day of powder skiing at Alta. We have been doing this for many years, and so far, have escaped with only minor injuries, a few cold toes and some wet clothes. As a ski area physician, however, I have seen many more less fortunate adventurers. I wanted to share a few thoughts about wind chill and frostbite.
You can learn to gauge to prepare for the cold by balancing layers to match with elements and the level of activity you are going to be doing. However, it is hard to tell when it’s going to be dangerously cold without understanding the wind chill. Essentially, it is what temperature it feels like on exposed skin based on temperature and wind.
I think of a 20 degrees below zero (F) wind chill as the big cut off point for risk of frostbite because skin can freeze in only 30 minutes in these conditions. When you think about how long it takes for a wait in a lift line, a chairlift ride to the top, and a ski run down, you can be getting close to 30 minutes. So, you are at reasonable risk of developing frostbite in only one or two runs when it is bitterly cold out. The chart below helps put things in perspective. Fortunately, there are very few days in Utah when we have 0-5 degrees with 15-30 MPH winds.
Most of what I see is frost nip, and grade 1 or grade 2 frostbite. These go from superficial freezing to full thickness skin freezing with clear blisters, but few patients have long-term problems. Key things to remember are to prevent freezing in the first place, but rapidly re-warm (without rubbing) injured sites and prevent re-freezing.
Grade 3 and Grade 4 frostbite can be considered deep freezing, and are identified after re-warming as having dark blood filled blisters, woody feeling skin, and can lead to loss of digits or limbs. These are the Mt. Everest kinds of frostbite.
At the University of Utah, deep frostbite cases are seen in both our homeless population, as well as outdoor adventurers. These are complicated cases and are managed by our burn unit teams. In addition to cellular damage from freezing, lack of oxygen and inflammation leads to small blood clots in the once frozen tissue. The blood clots prevent oxygen and nutrients from getting to the fingers, toes and limbs, and contribute to death of the tissue.
Frostbite is now managed in a similar way that heart attacks are treated. Angiography is used to visualize the blood vessels and identify if blockages are present. Then, if appropriate, the clot buster drug tPA can be given. This approach has led to improved salvage of frozen digits. Key things to remember are that you need ICU level care and this must be done within the first 24 hours after thawing.
So, keep your skin covered, let others know if you see their nose or cheeks turning grey or red while skiing, and keep in mind that there are new advances in diagnosis and management that can help preserve previously frozen digits.
Enjoy the winter and think snow!
Ted Paisley, MD is an assistant Professor in the Department of Family & Preventive Medicine at the University of Utah School of Medicine. He specializes in Sports Medicine.