Frostbite

We’ve hinted about this topic for a while. Let’s get down to brass tacks and talk about frostbite. Remember I’m not a doctor, but I play one on TV. Nothing in this blog should take the place of adequate medical care.

As usual, we’ll start with a story. I was 13. It was a Sunday morning in January, about 5 AM. The temperature was about -15 F (-26 C) with a 20 mph wind (windchill about -40). [While we didn’t know about windchill in those days, and I’ve been known to pooh-pooh it, it is a real factor when it comes to freezing flesh.] I was heavily laden with newspapers and stopping at the first house. The bike was too heavy to make it up the steep driveway, so I parked at the foot of the hill and jogged up with the paper. At the front door I heard a crash. I turned and looked down the hill to see my bike tipped over and newspapers flying about. I ran down and hastened to pick up papers, trying to stuff them back together. With heavy mittens I didn’t have the needed dexterity so I tossed the mittens aside and worked frantically against time and the wind. I’d gotten all 109 remaining papers back together (not all had blown apart) and reloaded on the bike. No more pages were flying around. I noticed my fingers weren’t cold, but they were stiff. I bit one and didn’t feel anything. Under the streetlight they looked white (and I don’t mean Caucasian, I mean really white).

With a couple of hours of outdoor work ahead of me I knew I had to do something or lose my fingers. I found a house with lights on and rang the bell. They knew me as their paperboy, but they also knew my older brothers from when we lived in this neighborhood (as tenants of the person whose house I’d been delivering to when this happened).

They invited me in and let me call my parents for a ride, then I went into the bathroom to thaw my fingers under running water. The pain was excruciating as blood returned to my fingertips – but I kept all my fingers and I delivered all of the papers on time – the next 100 or so from the back of a car. Fast-forward 35 years and I found myself working in a burn unit, treating people with frostbite.

Windchill is definitely a factor with exposed skin. Wednesday it was -12 degrees F (-24 C). It was calm so there was no windchill. I rode to work at 15 mph so, relative to me, there was a 15 mph headwind and therefore a windchill of -35 degrees. If you ride in winter, remember it is always windy.

What do you do for frostbite? The most important step is prevention. When it is really cold, cover all skin. The Cleveland Clinic says 10 minutes at -10 F is long enough to get frostbite. Wear mittens, not gloves. Your fingers help to keep each other warm. If they still get cold, you can make a fist inside of the mitten. A bit of anatomy will help that make sense.

Image from the Journal of Personalized Medicine.

The main takeaways from the picture are: 1) the blood supply to your hand (like your brain) is redundant. Notice that the radial and ulnar arteries join to form an arch and the blood supply to your fingers comes off of that arch. Thus, even if one artery is injured, your fingers get blood; 2) there are two arches – a superficial and deep arch. (Okay, three in this image, including the unlabeled one – I’ve never seen that third arch depicted and I haven’t dissected a palm lately to look for it. If I do, I’ll post an update.) This gives further redundancy; 3) the arteries to your fingers run up the sides. If your fingers are separated in gloves, more surface area is exposed to allow more heat to escape. Conversely, if your fingers are touching, they keep each other warm. Also, the pads at the tip are the last place to get blood – the vessels are pretty small by that point; 4) due to the multiple vessels running through your palm, if you tuck your fingers into a fist, the tips are warmed by the palmar blood.

As an experiment this week, I wore my big mitten from Empire Wool and Canvas Co on one hand. On the other I wore various liners under the mitten: 1) a thin polyester biking liner glove; 2) a full-fingered insulated biking glove [a spring and fall glove]; 3) a nitrile exam glove. While a glove was handy when I had to work locks and keys and mount a pannier, the mitten alone was warmer while riding. When my fingers got cold I had enough space inside to make a fist and warm them up. They warmed quickly due to direct skin-to-skin contact.

[An aside here: Clearly, the brain and the hand are important structures in humans. With the Circle of Willis in the brain and the palmar arches in the hand providing redundant blood supplies, our bodies have gone to great lengths to protect these structures. Think about that. Discuss among yourselves.]

Toes are also subject to frostbite. I could argue that they are easier to live without, but instead I’ll argue that you should protect them. Wool socks, liner socks if it’s really cold (I use silk for less bulk), and warm boots are essential. The longer you are out, the greater your chances of losing parts. Consider hand and foot warmers (battery-powered, or chemical pads that release heat when exposed to air).

You’re out in the cold. You notice your fingertips are getting cold. DO something! Get inside if possible. Move (your body in general, your hands and feet in particular). Get your hands out of the wind. Make fists. Stick your hands in your pockets (with mittens on if possible) or in your armpits (without mittens). (Zip your jacket back up to preserve core heat.)

Did you fail to do any of those and your fingers stopped feeling cold? Did they stop feeling anything? If you squeeze your fingertip, is it hard and you don’t feel it? Are your fingers stiff? Warm them up!

Do NOT rub snow on them. Do NOT run hot or cold water on them. You are trying to rewarm them to body temperature. Use water about that temperature. Feel it with an unfrozen body part (like an elbow or another person’s hand), because your frozen fingers can’t tell how warm it is and you don’t want to burn them on top of the frostbite.

When the skin has turned white and the tissue has frozen, there is no blood supply. The tissue will die if not rewarmed. As it rewarms, it will hurt. Deep frostbite can cause lasting damage. If in doubt, get to a doctor, preferably a regional burn center.

Deep frostbite will blister. The skin will turn purple. It will look like a bad bruise. That is essentially what you have – damaged and leaky capillaries that allow blood to flow into the interstitial spaces and cause the skin to look purple; clots that prevent flow into and out of small vessels. From there, one of two things happens: either it slowly returns to normal color, or it turns black, mummifies, and eventually falls off (which is known as auto-amputation). I am not going to include pictures of any of this. If you really want to see that, Dr Google will show you pictures of what happens when you get deep frostbite. Suffice to say that I have worked with people with fingers that were amputated at the first joint, leaving nubs (which can be surprisingly functional, but I don’t recommend you try it), and with people who lost their fingers (and legs, for that matter) entirely. I’ve seen it so you don’t have to.

Deep frostbite requires a doctor’s care – in a hospital. For the first 72 hours we encourage the patient to move their fingers actively but, unlike burns, we don’t move them passively – that could cause further damage to deep tissues. After initial warming, the fingers will have to rewarm from the inside out. Medications can improve circulation and re-establish blood supply before tissue dies (like the treatment to cerebral arteries after a stroke, or in the lungs after a pulmonary embolism). The body will scavenge dead tissue. That process can cause further complications that you can’t manage by yourself.

Your fingers may stay purple for a while. The doctor will wait for them to “declare themselves”. It is not always clear what tissue will survive and what is dead.

Doctors do not want to amputate fingers that are only “mostly dead”. They don’t want to amputate dead fingers but leave some dead parts behind. They also don’t want to amputate too far and take parts that will heal. Once the fingers have “declared themselves” they will take the dead part and cut back to healthy, bleeding tissue so the residual limb will heal. Then the therapist will work with you to help regain function with partial fingers, help you learn to compensate for what is lost, and help reshape the residual fingers.

Obviously, you don’t want to have first-hand knowledge of most of this. That’s what I’m here for – to convince you to care for your body and keep all the parts.