How To: Diagnosing and addressing Moderate Hypothermia in swimmers

In a world of short attention spans, why write one post when I can write two three?  🙂

I had intended the previous post on Moderate and Severe Hypothermia to include diagnosing hypo in swimmers, and what to do when it happens. In fact that was how I started writing this series originally. And I’m not writing anything particularly original here. There are articles on hypothermia all over the web. What’s different here, I’d suggest, is that I’m aiming it at swimmers and swim support staff, and I’ve experienced mild and moderate hypothermia myself, like most North Atlantic open water swimmers. The things I do for you!

As we’ve seen, the effects of Moderate Hypothermia are exaggerated and extreme versions of those suffered during Mild Hypothermia. Violent shaking and shivering, great difficulty or even inability to speak, impaired cognitive function and greatly reduced dexterity.

Diagnosing hypothermia in swimmers

It’s best to assume you are acting as safety officer, crew or observer for this, rather than as a swimmer.

  • If you are watching a swimmer for a while keep a check from early on of their stroke count. Give them time to settle into their regular stroke for five or ten minutes after the start and then do a simple count over one minute. Repeat the count at a regular interval. Once you have an idea of this you have the vital baseline for seeing moderate to sever hypothermia develop. With the onset of hypothermia, the stroke rate starts to drop. If the swimmers rate drops toward 10%, tell them they have to increase their rate or they are out of the water. It is not fair to the swimmer to pull them if they can recover, and it is often possible to recover for some period of time. Crew and swimmer are a partnership. More than a 10% drop is probably irrecoverable and the swimmer should probably be removed from the water at this stage.
  • For those of you thinking this is a very marginal percentage, note that experienced swimmers have consistent stroke rates. (My stoke rate for the entire English Channel was 70 spm plus or minus 2). For  less experienced swimmers you will need to act more quickly.
  • Look at the swimmer’s position in the water. Though not conclusive, hypothermic swimmers will lose the ability to kick and may slip into a more vertical position in the water. This is probably also irrecoverable as the vertical aspect will slow them further, reducing efficiency and speed significantly.
  • The simplest diagnosis tool is verbal questioning. Get the swimmer to talk by asking them questions. If you have no idea whether they are hypothermic, require a verbal response to see if they can speak. Are they mentally alert? If you are unsure, ask them some moderately complex question, the day and date or the days of the week in reverse, or counting backward. Don’t spend a long time at this or you further exacerbate the possibility of hypothermia, a few seconds should be sufficient. Don’t worry about very complex questions or that you think the swimmer needs to be counting backwards in prime numbers. When someone is genuinely hypothermic, simple questions become complex as oxygen supply to the brain is slowed. Listen also obviously of the swimmer complains of cold. OR, and this one is from personal experience and some friend’s swim reports, if the swimmer is indicating pains or cramps in the thighs or groin. These are good indicators of hypothermia.
  • At feeds, watch the swimmer’s ability to handle feed bottles. Can they open a simple bottle cap? Inability to so do indicates a loss of manual dexterity.

Remedial actions for Moderate Hypothermia:

A swimmer who is experiencing violent shivering should be immediately removed from the water.

Reduce further heat loss. This is the most important immediate step.

  • Get the person out of the water AND out of the wind. Wind is your enemy.
  • Remove wet swimsuit/wetsuit. Get the person dry as quickly is possible, WITHOUT vigorous rubbing. Watch for the Afterdrop effect. They will get colder AFTER they are removed from the water. However it’s is more important to get them covered and removed from wind exposure than dry. So just get them covered in blankets or a sleeping bag. As much as possible of the person should be covered, creating a hypothermic wrap, for most swimmers this will mean multiple layers, including hat and gloves. Moderately hypothermic swimmers may be unable to dress themselves. Help them. Carefully. They may not be able to stand or balance, their hands may have little to no strength or ability to grasp or pull. Use whatever is available to protect the swimmer, even newspaper. You may remember I suggested a heat blanket in your first aid kit on my article on first aid kits? This should go around the swimmer AFTER they have been otherwise covered, NOT next to the skin (as it will conduct heat away).
  • If further heat loss is stopped, a person will rewarm themselves at a rate of about two degrees Celsius per hour.
  • Encourage urination. You’ll recall that hypothermia suppresses ADH, the hormone that controls urination. Along with that is cold diuresis, where the contraction of surface blood vessels puts additional pressure on the bladder. If the person urinates the bladder will fill and protect/conserve heat within the body. Do NOT tell the person to urinate on themselves for the heat. It will evaporate and add to further cooling. It is because of these impulses that the weeds grow particularly high at the back of the parking spots in Sandycove, being quite well fertilized. By the men. I feel sorry for the women.

Add fuel through food.

  • Do NOT give alcohol or caffeine. Alcohol is a vasodilator. It expands the veins so cold blood from the exterior will flow into the core quicker. Caffeine is a vasoconstrictor so will slow the flow of warm blood from the core. Let the body operate to attain balance.
  • Give the swimmer some food and/or hot drink (hot chocolate, hot Maxim, again, not caffeine or alcohol). Something that is an energy source. Make SURE you do not scald them as their mouth will be cold also, and they will burn easily.

Initiate activity.

  • For a mildly hypothermic person who is shivering, physical activity will increase  rewarming.
  • For a Moderately hypothermic person, who may be shivering violently, they may not be able to move much more. The violent shivering and shaking is the bodies attempt to rewarm. It is a good (if uncomfortable) thing. DON’T try to suppress shivering. DON’T force someone to move who can’t. DON’T start rubbing them.

Add heat (but only carefully, slowly and after time has passed).

  • Heat should NOT be applied immediately after the person exits the water as this will accelerate Afterdrop.
  • No heat source should be placed directly on the skin.
  • When applying a direct heat source after getting the person covered (like a hot water bottle or gel pack), remember to first cover it, and only place it on locations where major arteries are near the surface, inside the upper thighs and under the armpits. Placing heat on arms, legs  or torso ACCELERATES Afterdrop.

On a good note: to date, only three Sandycove swimmers have been hospitalized after marathon swims over the years, and only one of those was hypothermia-related and he recovered within a few hours.

Hypothermia treatment

Maybe you’d like print off this chart (not mine) and put it in your swim gear for reference.

Severe or profound hypothermia is not a subject I will be covering. People with profound hypothermia should not be moved and need immediate Emergency Medical Treatment.


3 thoughts on “How To: Diagnosing and addressing Moderate Hypothermia in swimmers

  1. Pingback: Best practices for exit, rewarming and recovery | wildbigswim

  2. Pingback: The Worst Three Minutes | LoneSwimmer

  3. Pingback: Joining the South End Rowing Club

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