This article was written by Scott Light, PA-C. The Central Oregonian published it in the Health Matters column in September 2007.
The air is changing. There are cooler nights…a little more rain. Rifle hunters are heading out to check zeros on their long guns, and if you didn’t realize it the archers are already out beating the bush. Hunting season is back. This month I thought I’d take just a few moments to discuss hunter safety. Dehydration, heat and cold injuries and firearm safety are all important considerations while in the field, and they can all be tackled from the medical point of view.
This season starts early when daytime temperatures soar into the 90s. The same elements that make daily doubles treacherous for high school athletes present challenges to the sportsman, often without the luxury of an igloo cooler full of Gatorade close at hand. Forty- to sixty-percent of total body weight is water.1 Medically speaking, water loss from sweat that is not replaced is termed “sensible loss.” This is the most likely culprit for dehydration while out hunting, but certainly vomiting or diarrhea and a host of other medical conditions can cause or exacerbate dehydration .1 The fluid you lose from sweating is technically “hypotonic;” that is to say, it contains less salt than your normal blood or plasma. 2
One of the chief causes of too much sodium in the body (a condition termed “hypernatremia”) is simply not restoring fluid lost through sweating or breathing.3 Depending on the level of conditioning, an athlete (of course, I consider hunters athletes) can expend one to four liters of fluid an hour. As a general rule of thumb, you should replace fluids until your urine is barely yellow or clear, and you should be urinating at least “every three to five hours.”4, 5
In contrast to hypernatremia , if you are drinking plenty of water, but you aren’t taking regular meals, there is a risk of running low on salt. This condition called “hyponatremia” (low sodium) can become dangerous and result in serious neurological problems. As long as you are eating at least semi-regularly, you’ll get plenty of salt to go along with the water you drink. If unlimited plain water is available but conditions do not allow for taking regular meals (or heat is so excessive that food becomes unattractive), hyponatremia can be a problem. The invention of rehydration backpacks that can provide many liters of water have made this illness a bit more likely and especially so in extreme endurance events. If meals aren’t taken regularly, the addition of some salt-containing supplement, or even simply adding table salt to fluids can prevent this evil cousin of dehydration. A note about sweet sports drinks is in order. Too much sweet drink can cause diarrhea, which would definitely be a problem in a hot or arid environment. Typically you can cut these drinks by half with plain water and do pretty well.
When your body overheats and cannot adjust or decrease temperature adequately, heat exhaustion and/or heat stroke are the result. One reference explains that heat exhaustion occurs at core temperatures greater than 100.4 degrees F, while heat stroke is normally considered at core temperatures greater than 104.0 F.5 Classically heat stroke can occur as a result of untreated or ignored heat exhaustion, with the chief difference in symptoms being a change in the level of consciousness. If your hot, dehydrated, sick-appearing hunting partner starts making even less sense than usual, or gets downright loopy, this is a bad sign indicating heat stroke rather than heat exhaustion. Lack of sweat was once considered the determining factor for heat stroke, but “exertional” heat stroke can be occurring in a perspiring patient, so consider level of consciousness the key indicator even in the face of active perspiration.5 Cold water or ice should be placed around the head and neck, groin, and armpits, while the person is “fanned” aggressively to assist in evaporative heat loss.5 If mental status changes are recognized, the affected hunter needs to be evacuated to a higher level of medical care as rapidly as possible.
Next, as I mentioned in the intro, this time of year can also be marked by cool nights. Extreme temperature variations between daytime highs and nighttime lows are common.
First let’s discuss how heat is lost. There are five mechanisms for heat loss described in virtually every physiology reference: “radiation, conduction, convection, evaporation, and respiration.”6 The hunter who perspires heavily in the late afternoon in order to set up at last light may suffer from evaporative heat loss due to the wet nature of his skin and clothing. Evaporation and conduction are also major sources of heat loss for the wet water foul hunter, or those caught out in the snow or rain. Water has a “thermal conductivity …approximately 30 times that of air.”6 Moisture trapped on the exposed skin or held near the skin with fibers that don’t wick it away (like cotton) can rapidly sap heat from the sportsman. Cold windy conditions can also cause heat loss through convection, or through radiation which is simply heat emanating from the body, especially those areas vulnerable to heat loss such as the head and low back.
Hypothermia is often categorized as mild, moderate and severe with mental status changes occurring even in mild cases in the form of “apathy,” or a lack of concern for one’s own worsening condition.6 Moderate illness can result in a worsening mental deterioration which will progress to severe hypothermia and all-out coma if no effort at treatment is made.6
Let’s discuss prevention. The old dogma “cotton kills” is absolutely true. Cotton fibers trap moisture next to the skin and typically provide only minimal insulation for their weight even when dry. Wool or synthetic fibers like pile or polypropylene are ideal since they wick moisture away from the skin. Warming insulating layers, then trapping that warmth next to the skin, is effective. Materials that are thick and fluffy are effective for this. Down is good, but only in dry climates. Garments and sleeping bags with synthetic loft can act like down, but remain useful when damp. Synthetic loft is usually not as light or compressible as down, so there is a trade off. In rain or snow, a waterproof breathable shell is paramount for protecting insulating layers, and is typically effective for blocking the wind as well. Dress in layers starting with light weight polypropylene underwear, and then increasing thicknesses of wool or pile and finishing with a shell. Remove or add layers as needed to minimize sweat and overheating, or to remain comfortable while at a hide or when resting. Mittens, as a rule, work much better than gloves, but provide a challenge to the shooter. I recommend experimenting on the range with whatever hand wear you select prior to the season, and recognize the limitations anything covering the hands presents.
In the treatment of hypothermia , the first step should be prevention of further heat loss. Any wet clothing should be carefully removed and then warm dry insulating layers applied. These measures allow any capability for the patient to rewarm themselves to flourish, and is termed “passive” rewarming. Certainly if the individual is conscious warm fluids by mouth are acceptable. Any further attempts at active rewarming are complex, since depending on the severity of the hypothermia, active rewarming may cause cold blood and cellular waste from the extremities to be circulated to the core of the body creating a more serious medical problem. The worse off the person is mentally then the more likely it is that these complications exist. Based on the severity of illness, the moderately- to severely-impacted victim should be treated to avoid further heat loss, handled carefully and transferred to a higher level of medical treatment.7
Finally I’d like to discuss firearms safety. I own several firearms and I’m fully supportive of shooting and hunting as important sports. From the medical viewpoint, however, some important statistics can’t be ignored. Over five thousand kids under the age of 18 are killed in accidental shootings each year, and many more are injured.8 A study of shootings in homes in three major US cities showed that for every one legitimate shooting “there were four unintentional shootings.” This indicates that many who own guns aren’t practicing simple weapons safety.9 Unfortunately many more statistics can be cited.
Every shooting organization has its own set of safe shooting rules, but I prefer the basic principals set out by the late Jeff Cooper.
First, all guns are loaded all the time. This is true until you have personally verified that they are not, and even then they are treated as if they are loaded. This also means that every time you pick up a gun you personally ensure that the chamber is clear.
Second, never let the muzzle cover anything you aren’t willing to destroy. Rule two means never putting a gun barrel on your toe, letting it sweep your partner, or pointing it at anything other than a safe area or your intended target regardless of its status.
Third, keep your finger off the trigger until your front site is on the target and you are ready to shoot. Your finger is the best safety. Anytime your finger is on the trigger the gun can easily be fired. Use, but don’t rely on the safety catch.
Fourth and last, be sure of your target and what’s behind it. If you haven’t positively identified it, you aren’t ready to pull the trigger.10
If these four rules are religiously maintained the chances of an accidental shooting are finite. Many military units no longer refer to rounds going off unintentionally as accidental discharges, but now it is often termed a “negligent discharge,” and in my point of view this more accurately describes the situation. Those of us who choose to use and own guns have a responsibility to store them safely and to model and teach safe shooting principals.
Certainly we have only scratched the surface on all of these topics, but I hope this has been a relevant review of some of the salient safety issues for this year’s hunt. With proper knowledg and preparation, tragedy can be avoided. I certainly wish everyone a safe and successful hunt this year and for many to come.
Scott Light, PA-C, practices in association with Michael Knower, M.D. His office is in the Prineville Associates Medical Building , 1251 NE Elm Street . The telephone number for appointments is (541) 447-1680.
References
1. Tierney L, McPhee S, Papadakis M. Current Medical Diagnosis & Treatment. 44th ed. New York . Lange Medical: 2005.
2. Ginsburg J. Gastrointestinal physiology webpage. Medical collage of Georgia. Available at: http://lib.mcg.edu/edu/eshuphysio/program/section6/6ch10/s6c10_11.htm. Accessed on 21 August 2007.
3. Adrogue H, Madias N. Hypernatremia. New England Journal of Medicine. Vol 342, No 20. May 18, 2000 .
4. Wanke C. Patient information: acute diarrhea in adults. Up to Date. Available at: http://patients.uptodate.com/topic.asp?file=inf_immu/8950 . Accessed on 24 August 2007 .
5. Wexler R. Evaluation and treatment of heat related illness. American Family Physician. Vol 65, No 11. June 1, 2002 .
6. McCullough L, Arora S. Diagnosis and treatment of hypothermia. American Family Physician. Vol 70, No 12. December 15, 2004 .
7. McSwain N, Fame S ed. Pre hospital trauma life support, military edition. 5th ed. St. Louis . Elsevier Mosby: 2005.
8. Bernstein D, Shelov S. Pediatrics for medical students. 2nd ed. Philadelphia . Lippincott Williams & Wilkins: 2003.
9. Kellermann L, Rivara F, Lee R, et al. Injuries due to firearms in three cities. New England Journal of Medicine. Vol 335:1438-1444, No 19. November 7, 1996 .
10. Wikipedia. Jeff Cooper (colonel). Wikipedia. Available at: http://en.wikipedia.org/wiki/Jeff_Cooper_(colonel). Accessed on 25 August, 2007 .