Hypothermia - sure, if you survive that long...

[GregS]

The thread title is plagarised: see Hypothermia - sure, if you survive that long - an excellent article from Kayak Quixotica highlighting the dangers of cold shock.

Cold shock is often presented as an afterthought in a discussion of hypothermia, and yet it can take you down almost instantly, well before hypothermia has a chance to set in. Cold shock is more immediate. What is cold shock? Well, it’s an almost instantaneous reaction to immersion in cold water. A variety of symptoms can cause almost immediate incapacitation and even death. Let’s have a look…

What you need to know first is that the risk & symptoms of cold shock really kick in when water temps are around 55f and increase as the water temps continue to sink. Air temperatures are not relevent. Sudden immersion at these water temperatures can cause uncontrolled gasping which, if your head is under water at the time, will lead to nearly instant drowning. This is one reason kayakers have been found upside down, seemingly never even attempting to roll or wet exit. Cold shock can also play havoc with your breathing even if you keep your head above water. It can cause hyperventilation which can lead to panic and a condition called Alkalosis, which can cause confusion, dizziness and possible loss of consciousness well before hypothermia has time to set in. Some folks will experience breathlessness, or the inability to breath. From here, dizziness, panic and an overwhelming sense of claustrophobia can take hold causing hyperventilation once again. The point to take home is that cold shock can kill you instantly or slow you down and put you into a state where you’ll be making bad decisions long before the onset of hypothermia.

This article links to a Cold Water Primer for Sea Paddlers article on AlaskaKayakSchool.com... which in turn leads (via a broken link) to a superb, 7 page introduction on AtlanticKayakTours.com.

The latter isn't overly long, but covers:

• Cold Shock
• Hypothermia
• How Your Body Regulates Core Temperature
• Types & Signs of Hypothermia
• Treatment of Hypothermia
• Cold Water Equipment

None of the contents are repoduced here: the whole lot takes just a few minutes to read and merits seeing in context!

Mario Vittone's Staying Alive in Cold Water (1-10-1) discusses "Cold Water Boot Camp, USA" and elaborates on the 1 – 10 – 1 principle of cold water immersion: "three numbers that will help you remember how to survive the three phases of an unexpected dip into cold water". This is also discussed here.. with a better graphic. Combining the two sources:

Phase 1: The cold shock response – accidentally falling into cold water (say, under 59° F) is an assault on the body’s senses. Characterized by uncontrollable gasping and disorientation, the first moments can be the most dangerous. So for that first minute (1), do nothing but keep your head above water, try and stay calm, and control your breathing. The gasping will stop and then you’ll be able to work on getting yourself safely out of the water.

Phase 2: Swim failure – or the loss of muscle control – happens to everyone who stays in cold water long enough. If you’re not wearing a life jacket – regardless of how strong a swimmer you are – you will drown long before you ever become clinically hypothermic. The longer you stay in, the weaker you become. So after that first minute of just staying calm, you have about ten (10) minutes to try and self rescue. If you haven’t gotten out of the water by then, you’re not going to. Conserve your energy to delay phase three.

Phase 3: Hypothermia – core body temperature of 95° or less – takes a surprisingly long time to happen. The point here is not to panic. Depending on variables like air and water temperature, no matter how uncomfortable you are (and trust me – you will be) you will have an hour (1) or more before you lose consciousness from hypothermia.

Cold Shock and cold incapacitation can happen while a victim is normal thermic. Once you lose strength and coordination it will not come back. Use what you can when you an.

The gCaptain blog contains an even better article by the self-same Mario Vittone. This is entitled The Truth About Cold Water, and notes it "is impossible to die from hypothermia in cold water unless you are wearing flotation, because without flotation – you won’t live long enough to become hypothermic".

When the water is cold (say under 50 degrees F) there are significant physiological reactions that occur, in order, almost always.

• You Can’t Breath
• You Can’t Swim
• You Last Longer than You Think

He goes on to discuss:

• Rescue Professionals Think You Live Longer...
• Out of the Water is Not Out of Trouble

The article encourages viewing of Cold Water Boot Camp, dubbing it "one of the best 10 minutes on immersion hypothermia ever produced"...

This video can be followed up through Beyond Boot Camp resources:

• Lectures - The stages the body encounters and experiences during cold-water immersion, hypothermia, and recovery.
• Extractions - Utilizing many different types of safety gear available to any rescue-responder and boater.
• Triage - For all victims of cold-water immersion and with particular attention to mild, moderate, and severe hypothermia.
• Transport - Demonstrating proper techniques with different types of rescue equipment.
• Extras - Ambulance Transport to Hospital and Thermal Protection Test and interviews with the responders.

See also Paddling Light article on The Risks of Cold Water Paddling

[GregS]

Going beyond the sea kayaking resources have been listed first in this thread...

The RYA produce a basic guide to Cold shock, hypothermia and drowning.

The initial response to immersion is cold shock. It only lasts a few minutes but is the cause of many deaths. On contact with cold water the blood vessels in the skin constrict and increase the blood flow back to the heart. This, together with an increased heart rate and hydrostatic squeeze from the water, raises the blood pressure dramatically. This dangerous combination can lead to death from cardiac arrest or stroke in susceptible individuals.

In a fitter casualty the inability to breath-hold and a phase of rapid, uncontrollable breathing may lead to the inhalation of water.

In the second phase of immersion the heart and breathing rate decrease and a gradual decline of muscular strength begins. The ability to swim fades and hands become useless as the body temperature falls.

Pete Seidel (United States Coast Guard Auxiliary) provides a fuller account:

To properly prepare, you have to first understand what happens to your body in cold water. Water removes heat from a body 25 times faster than cold air and most of the body heat is lost through the head. Swimming, thrashing about, and other physical activity increases the heat loss through the limbs and extremities. If you become a person in the water (PIW) you will sharply reduce your survival time though physical activity. Strong swimmers wearing a PFD have died before they covered 100 yards in cold water. Did you know that in water with a temperature of less than 40º F., a strong man can expire before he can swim 100 feet? Two factors come into play against a you while you are immersed in cold water: they are cold shock and hypothermia.

Cold shock is the body’s reaction to the shock of cold water. During cold weather boating all persons on board should wear life jackets. Cold shock from falling into icy water can trigger an involuntary gasping reflex that will cause you to inhale water through your mouth. Without a life jacket a person can drown without ever coming back to the surface. Wearing your life jacket will increase the likelihood of survival if you should accidentally fall into the cold winter water. Cold shock may also result in cardiac arrest. When the head and chest are exposed to cold water, the result is often a very sudden increase in heart rate and blood pressure. Cold water immersion can also result in immediate loss of consciousness but, depending on the type of life jacket worn an unconscious victim can survive without drowning.

His account of hypothermia is also concise and to the point:

Hypothermia in layman’s terms is decreased body temperature. This condition develops more slowly than the effects of cold shock and you may not be immediately aware of the symptoms. The symptoms of hypothermia include shivering as the body loses heat and body temperature drops; uncontrolled rapid breathing follows the initial gasping response and may cause a loss of consciousness, muscle rigidity and loss of voluntary motor function resulting in physical helplessness. A hypothermia victim starts to shiver as core body temperature falls from 97ºF. down to about 90ºF. A person at risk of hypothermia must try to control breathing rate to avoid hyperventilation leading to unconsciousness following the immediate involuntary gasping response to the initial immersion into cold water. Uncontrolled or rapid breathing will speed up the chilling process. When the body’s core temperature falls to 93ºF. physical ability is severely diminished and mental capacity begins to deteriorate rapidly. A victim usually falls into an unconscious state when body temperature falls to 86ºF. If the victim doesn’t drown first, hypothermia will finish him off when the body temperature falls to or near 80ºF. Survival figures show that an adult dressed in average clothing may remain conscious for one hour in water at 40ºF, and perhaps as long as 2 - 3 hours in 50ºF water. Remember, any movement in water accelerates body heat loss. Unnecessary movement can reduce survival time to minutes. The film, Titanic, graphically portrayed the fatal effects of lowered body temperature on persons in the water.