ARKANSAS CANOE CLUB

Hypothermia Teaching Notes for Paddling Courses

 

Hypothermia is a lowering of body temperature that causes the brain and body to begin to fail. Few paddlers die of hypothermia, but it is very often a contributing factor in drowning. As the body cools there is a significant loss of strength, coordination, alertness, and in the ability to make sound decisions.

The combination of cold water and ill-prepared boaters can kill.

Causes

Cold water robs the body's heat 25 to 30 times faster than cold air. A 5 MPH current flowing past the body may cool it up to 250 times faster than still air of the same temperature.

In 70 degree still water, an unprotected body loses more heat than it can produce. In 50 degree still water the estimated survival time is less than three hours for the average person. In 50 degree swift water with other typical river hazards, a person without adequate protection may survive only a very few minutes.

Hypothermia does not always occur in cold weather. Storms anytime may soak an unprepared boater, wind can steal heat from his body. A long swim or multiple swims on a cool overcast day may make rewarming difficult. An Injured person may experience hypothermia as shock sets in.

Symptoms

Sudden Immersion in Cold Water causes several dangerous responses

• Heart dysfunction
  • Rapid rise in blood pressure and heart rate
  • Those with weak heart and circulatory system may develop lethal cardiac abnormalites.
  • Even, young healthy persons occasionally develop abnormalities of heart beat which may cause sudden death.
• Breathing Abnormalities
  • Hyperventilation or an increase in rate and depth of breathing
  • Huge, involuntary gasps in the first few seconds of immersion
  • Followed by a minute or more of rapid, deep breaths making aspirating water and drowning more likely especially if underwater or in turbulent water or high waves.
  • Complication of hyperventilation is alkalosis, which results in dizziness, fainting, and increased probability of drowning.
  • Cold water also limits ability to hold breath to about one third of normal time.
• Muscle Dysfunction
  • Blood Vessels in the skin and skeletal muscles constrict strongly, which hastens cooling of outer shell.
  • Cooling of muscles and nerves results in slower, weaker, poorly coordinated movements.
  • Even good swimmers drown more quickly unless wearing pfd or holding floating object.
  • Inability to continue swimming commonly occurs within ten to fifteen minutes after immersion colder than 50 degrees.
  • After just five minutes in icy water, victim probably can't climb out alone or even catch and put on PFD.
• Precautions for sudden immersion are:
  • Don't dive in cold water, enter gradually with head well clear of turbulence and waves.
  • Breathing should be consciously controlled during entry and next two minutes until feeling of unable to catch breath is gone.
  • The more clothing and insulation worn, the less hyperventilatory response.
  • PFD is a vital precaution.
  • Don't chew gum or anything else when paddling on cold water.
  • Know your limits for air and water temperature and use good judgement.

Long Term Immersion in cold water

• Usually 15 to 20 minutes elaspe before the body core begins to cool consistently
• Shivering becomes conspicuous and continuous
• Victim feels miserable and may believe end is near, although--
• In 50 degree still water the estimated average survival time is two and one half to three hours.
• Body build, body fat, and body size influence rate that core cools.
• In cold swiftwater, an unprotected swimmer may not survive long enough for core cooling to matter.
• When out of the water, but still wet and in cold air, cooling may continue if not treated.

Recognizing Hypothermia:

• Paddlers usually must determine victim level of hypothermia from signs presented by the victim as they probably will not have a way to accurately measure body temperature.
• Mild Hypothermia
  • Begins with sensation of chilliness, skin numbness, shivering, impaired muscle performance particularly with the hands. Develops into more obvious incoordination and weakness, stumbling, slow pace, mild confusion and apathy.
  • Advances to gross incoordination with frequent stumbling, falling, and inability to use hands, mental sluggishness with slow thought and speech, retrograde amnesia.
  • These signs are known as "umbles". The person fumbles, mumble and grumbles, stumbles and tumbles.
  • Failure to take corrective measures can result in progression to severe hypothermia.
• Severe Hypothermia
  • Shivering ceases, severe incoorination with stiffness and inability to walk or stand, incoherence, confusion, and irrationality
  • Advances to severe muscular rigidity, semiconsciousness, dilatation of pupils, inapparent heart beat or respirations. Further cooling brings unconsciousness and eventually death due to cessation of heart action.
  • A common and important sign of severe hypothermia is neglect or carelessness about protection from the cold. A paddler may be unconcerned of taking another swim or attempting runs above his impaired ability.

Treatment of Mild Hypothermia

• Treatment is simple, Early Recognition is more critical.
• Get out of the water and get shelter from the cold.
• Remove wet clothing and put on layers of dry clothes, wear PFD for insulation.
• On shore physical activity and dry clothes are usually sufficient
• An open fire, heat packs, warm sweet liquids, and quick calorie foods can speed rewarming
• Preventing recurrence is essential because the person is likely weakened and has less reserve engery.

Treatment of Severe Hypothermia

• Severe Hypothermia is a complex disorder, simple measures used to treat mild cases are inadequate.
• First major problem is hypothermic heart is extremely prone to ventricular fibrillation which can be brought on with the slightest bump or jolt. Do not attempt CPR! Options for both field treatment or successful evacuation are extremely limited.
• Second major problem is rewarming with external heat sources is required, but success of wilderness techniques is limited. Three general procedures are used: protection from environment, external rewarming, and central rewarming.
• For purpose of ACC School on the Mulberry River, I would not try to move a victim of severe hypothermia other than to get him out of the river. I would shelter, begin rewarming, and send runners to call for help. I would stay put and try to keep things stable until better qualified medical help arrived.

Prevention

• Prevention is more effective than any treatment.
• Understand hypothermia and our susceptability to it.
• Be Prepared.
  • Dress appropriately for sudden immersion in the water.
  • Carry drybag with extra clothes and fire starter.
  • Be trained and practiced in self rescue and rescue of others.
  • Anticipate and avoid conditions that put you at unreasonable risk.
• Be aware of weather and river conditions.
• Be aware of each other.
• Eat and drink often to maintain your engery reserve.
• Know your limits for air and water temperature and use good judgement.

Reference Materials and Offsite links:

• Hypothermia, Frostbite and other Cold Injuries, Wilkerson, The Mountaineers, 1986
• Whitewater Rescue Manual, Walbridge and Sundmacher, Ragged Mountain Press, 1995
• Medicine for Mountaineering, Wilkerson, The Mountaineers, 1992
• Wilderness Medicine, 4th Edition, Forgey, ICS Books, 1994
• Medicine for the Back Country, Tilton and Hubbell, ICS Books 1990
• Swiftwater Rescue, Slim Ray, CFS Press, 1997.
• Hypothermia Prevention, Recognition and Treatment
• Ohio Dept of Natural Resources
• Boating, Cold Shock and Hypothermia
• SAR British Columbia