Accidental Hypothermia & Cold Water Immersion

It has been a long and grueling week at the office and you and your fishing buddy have next week set aside as your yearly end of the tournament season trip to Trinity Lake.

It’s November and the Smallmouth fall bite is on, crisp cool mornings and Indian summer afternoons. Anticipations are high as the ritual starts as in years past.

The afternoon of the second Day while cranking points in the Papoose arm was a pleasant 72 degrees and sunny, in fact the weather has been stable all week and no major storms are forecasted. The both of you are fishing in short pants and light cotton shirts with a light blended jacket for the ride back to the marina where you have rented a cottage for your 3 day trek. The water temperature is 62 degrees and actually the both of you were hoping for a storm to jump start the reaction bite. Perhaps a storm would have helped.

The crank bait bite picked up at dusk with the smallmouth moving shallow, so the stars are out as you settle in for the half hour ride back to the marina squeezing out every last minute of ambient light, then some. The Life vest are on and the kill switch is applied when planning speed is reached, about 30 mph and wham, spin and the both of you are in the water. Apparently a “widow maker” strikes again, with your lower unit now lying on the bottom of the lake you both safely climb aboard, surviving the initial cold water immersion. The ambient air temperature is now a pleasant 58 degrees with light winds of about 10 miles per hour out of the North-West and the water temperature is 61 degrees. You noted that at dawn this morning it was 42 degrees and the water temperature was 58 degrees.

Our two fishermen do have a cell phone; however, like a lot of our lakes there is no service available. Also, the families do not expect them home for two more days. It’s also November, a Tuesday night and only two other boats were seen all day and both were fishing the tailings which are on the opposite end of the Lake.

Who thinks by reading this our two fishermen are in trouble? What is the probability that one or both will die during the night? What changes or behavior would you expect in your self and your fishing partner? What might you do now to perhaps save your lives? What could you have prepared ahead of time to maximize your survival chances?

Accidental Hypothermia and cold water immersion is what we are going to briefly discuss and in fact the United States Coast Guard data supports the majority of fishing related fatalities occur during the colder months. Hypothermia is both a symptom and a clinical disease entity. The normal body temperature is 98.6 Fahrenheit (oral temperature, plus minus 1 degree). So how much heat does one have to loose in order to be in trouble? One way we compensate to the cold perceived by our skin is shivering, termed shivering thermo genesis, which we all are familiar with. This is an attempt to raise our core temperature and is primarily driven by skin temperature. Maximum shivering occurs at a core body temperature of 95.0 degrees Fahrenheit. This is only about 3 degrees below where we live normally. This physiologic mechanism produces approximately4.5 times the resting rate of heat production by our bodies. We are also going to urinate a lot; in fact immersion in cold water can increase urine production by 350%, which leads to volume depletion and dehydration.

What exactly is in medical literature considered cold water? Numerous reports in the literature all consider water colder than or equal to 25 degree centigrade to be dangerous. Folks that is 77 degree Fahrenheit when converted. Thermally neutral water is about 91 degree Fahrenheit, which means heat loss is equal to heat production for a nude subject at rest. In this thermally neutral water one could remain indefinitely without risk of hypothermia. One may reasonably ask where all this data comes from. The most famous is the Titanic which sank in 1912. The ship sank at 11:40 pm on April 14th, in calm seas with a water temperature of 32 degree Fahrenheit. Of the 2201 people on board, only 712 were rescued, all from the ship’s lifeboats. The 1489 people who died, the majority of whom had life jackets on, died in the water despite the arrival of a rescue vessel within 2 hours.

Fortunately the only data that exist for severely hypothermic humans are those from the infamous Dachau concentration atrocities, in which conscious victims were cooled to death in cold water. Other accidents which come to mind include the cruise ship accident in 1963 of the ship Lakonia in which 120 people died in 64 degree Fahrenheit water, again with life jackets on.

Now that we know we are going to urinate a lot and shiver like a mad hatter, what next? When our core temperature drops two more degrees, to 93.2 Fahrenheit, amnesia, inability to speak clearly, and poor judgment develop. Decisions like I can swim to that island become attractive. Its cold out hear in the wind on this cold boat and the water is 70 degrees so I’ll get in the water and warm up. Life or death decisions. One very interesting point of progression is when shivering stops. This occurs at a body core temperature drop to around 87.8 degrees Fahrenheit. Real trouble starts now as the various heart beat irregularities start to show up. Unconsciousness occurs at or about a core temperature of 86 degrees Fahrenheit. The lowest accidental adult hypothermia survival victim reported had a core temperature of 60.8 degrees.

Let’s go back to coordination for an example. A well known study of semi-nude subjects, that is lightly clothed, in 50 degree water found that after the first five minutes of immersion, grip strength, began to fall at a rate of approximately 1.8% per minute.

One of the important variables determining cooling rate is the amount of subcutaneous body fat. The more body fat, the longer it takes for the core temperature to drop. I’m sure many of us welcomed that statement, I know I did. Unfortunately, as in most things you don’t get something for nothing so the overweight population tends to be in poor cardiovascular condition. Therefore, while they may be more resistant to the early core cooling once we drop into the 80 degree range and the heart rhythm disturbances start to surface this population has a higher fatality rate.

We now know the definition of hypothermia, a two degree drop in core body temperature, the definition of “Cold Water”, and the meaning of the cessation of shivering which equals the beginning of cardiac problems. The remaining time will be spent on prevention and making the best of what we have.

The two fishermen above in the example are I and Dr. Regor, a veterinarian who I fish with often. The incident is true except the Cold water immersion. Our engine would not start and we faced the very real possibility of spending the night on the Boat. Fortunately for us the Veterinary school programs teach basic boat mechanics which I missed in medical school and we made it back in several hours after dark, thanks to Dr. Regor. My first question was do we have any other clothing on board as we were not fishing in my boat? Do we have any matches or a lighter on board? No to both questions came back quickly. We have all heard success comes when opportunity meets preparation. This is true, as well as the following statement; accidents and the outcome of accidents, come to those who loose focus and are careless for only a moment. I will give one more example to drive home this point. Death and disability do not come to stupid or dumb people, although it certainly can. It can happen to experienced sportsman who loose focus, panic, have no plan, or become complacent.

During my Fourth year in Medical School I went to the State of Montana, Fort Belknap Indian reservation to do Family medicine as a two month rotation. Naturally, as an avid bow hunter and being from South Carolina; however, never out West my trip was in the Late Fall to coincide with hunting season. I was fortunate enough to get a Pronghorn Tag from the Reservation. It was November and December in Eastern Montana with the night temperature around minus zero. Many afternoons after clinic I would drive my four wheel drive across the moon appearing landscape and glass Antelope. One afternoon I had glassed a nice buck maybe a mile away, so I parked in a slight depression and made a stalk crawling along in slight depressions for the last quarter mile or so. To complicate things the herd relocated three times during my stalk. It was getting dark and I was as close as I was going to get with enough light to shoot. I made a shot and went to my first Antelope and field dressed him at this point with my pen light. I stood up and noticed total darkness, no lights for as far as I could see and since I had been crawling along on my belly I had no idea which way the truck was. My total focus was on that stalk and nothing else existed in my universe at that moment in time. I had on light clothes and was in no way prepared to encounter below zero temperatures. No one knew where I was and certainly I would not be missed until the morning rounds at the hospital. I did not even tell anyone I was going out that afternoon. Panic shook me to my core. Long story short I picked a star and walked in a straight line in the general direction from whence I came and eventually crossed some tire tracks in the grass. These had to be mine as no one else was out there, or had there been? Once again blind panic surfaces and now do I go right or left? I actually forgot which way I went but came back to my truck and actually cried for thankfulness. I was not afraid of being lost all night; I’ve spent more than one night in a Low Country Swamp slightly turned around with no fear at all. Here in Montana, there was no doubt in my mind that if I do not locate my truck in the next few hours I will die here. What could I have done? To start I could have turned my dome light on inside the vehicle which in that flat country could be seen for miles. I could have told someone where I was going and what time I should be back. Those two ideas’ are simple, easy to do and could have very well meant the difference between life and death.

Now back to Trinity Lake, PREPARATION:
I would consider the following items aboard your boat at all times to be a good start. A good high quality sleeping bag rated to zero degrees in a waterproof bag would be number one. Also in waterproof bag is a separate dry change of clothes to include thermal underwear and light waterproof upper and lowers like “Frogg Toggs”. A space blanket is also light and takes up very little space. A flare gun as well as matches in a waterproof container is also safely stored away. I usually have a firearm on my boat and three evenly spaced shots are considered a universal distress signal everywhere. Some type of assist device on the rear of your boat can facilitate re boarding your vessel and many current boat manufactures have this safety item as an option. I also like to take along a small backpackers stove and a six ounce bottle of white gas such as Colman’s fuel. When one is shivering it’s not the ideal time to practice our woodsman ship skills. This equipment is stored in my Ranger’s center front storage space and takes up little room. It is always there even in August. I never want to experience that feeling of total blind panic that I did on that Eastern Montana plane again and with a little preparation and planning I or you don’t have to.

In summary, Hypothermia can happen any time of the year not only in the winter; in fact when I worked as a Forensic Pathologist the majority of our exposure related fatalities occurred in the spring. I think the warm afternoons give us a false sense of complacency, like our two fishermen on Trinity. Perhaps a storm front would have helped the crank bait bite, but one thing for sure is both our anglers would have been better prepared for cold and wet exposure, therefore increasing the probability of survival. Most of our fatalities due to hypothermia at the Medical Examiner’s Office occurred in the “homeless” population who had not adequately prepared for the plummet in night time temperatures and the heavy due we experience at daylight. One can’t help but wonder if the warm spring afternoons lead to a sense of complacency that all is well.

Once an accident has occurred the most important consideration is getting dry and warming the core body temperature. If adequately prepared this should be no problem, unless of course your boat sinks. If not adequately prepared or your boat does sink along with all your gear number one is still to get dry, out of the wind if possible, and unless the water is 91 degrees or above to stay dry. If you cannot dry your clothing then leave the wet clothing on, as the cooling rate is linear and anything is better than exposed skin. Survivors should attempt to get as much of their bodies out of the water as possible. Water has a thermal conductivity approximately 25 times greater than air. So get as much of your body out of the water as possible, even if this means exposure to cold wind and spray. Many people including some medical personnel do not understand the concept of “wind-chill” and assume that survivors have a higher heat loss if exposed to wind when wet than they would if immersed in water and this is most true in water we would not consider “Cold”, that is for example 65-70 degree water temperatures. This term as proposed in its original concept by Sipple and Passel was used to describe heat loss from unprotected skin exposed to wind. This term is frequently misused in the media without regard to protected skin verses unprotected skin. This misleads people to erroneously conclude that wind-chill applies to both clothed and unclothed areas of the body. This has occasionally led to survivors leaving a position of relative safety atop a floating vessel usually with tragic results. It is important to keep in mind that the sensation of coldness is skin dependent and does not reliably convey information about the rate of heat loss when two different environments such as air and water are compared.

Finally, thank you for reading this and if one person’s family is spared making funeral arrangements then, well my time and thoughts have been well spent. These practices if implemented take little preparation and can mean the difference between a missed shift at work and a cold night on the lake to include one angry significant other verses the alternative ; the loss of life. Have a great and safe spring. Tight lines and go fishing, it’s one of the safest sports out there that the whole family can enjoy.

Dr. Rollins received his Dental and Medical degrees from The Medical University of South Carolina in Charleston, South Carolina. He went on to complete an internship and Anatomic Pathology Residency / Fellowship in Forensic Pathology at The University of California, Davis Medical School. He practiced both Forensic Dentistry and Medicine for five years in Arizona and California and currently is in private practice with U.S. Health Works Medical Group, Northern California as an Urgent Care, Occupational Medicine Physician. He is a Pro-Staff Team Member with “Fish Hedz”, and is an avid recreational and tournament angler.