Jaguar Mauling

The tragic event of a 140-pound jaguar mauling and killing a zookeeper in Denver reminds us about the inherent dangers of close contact with wild animals, no matter what their prior behavior. Animals act by instinct, and even with domestication, can be provoked by interactions with humans.

Once again, I would like to turn to the wisdom of Luanne Freer, M.D., who has written a chapter on wild animal attacks in the forthcoming 5th edition of the textbook Wilderness Medicine. As Dr. Freer notes, adult cats (including large cats, such as jaguars) have 30 permanent teeth, arranged in rows of 16 upper and 14 lower teeth. The upper teeth overlap the lower, resulting in an overbite. This helps the animal lock its teeth into prey and exert twisting and tearing forces.

Big cats typically attack from behind, biting the neck and occiput (lower portion of the skull) of their prey and attempting to maneuver their canine teeth between the victim’s neck vertebrae and into the spinal cord. In a report of fatalities from jaguar attack, 77% of victims were bitten on the nape of the neck and half of the bites were made to the base of the skull. The goal of rapidly paralyzing its prey is also accomplished by a violent shake of the cat’s head, which breaks the victim’s neck. In a fifth of cases, the killing bite was to the head, with at least one canine tooth piercing the skull or ear canal. Big cats also claw their prey, producing deep parallel slash wounds. If the abdomen or chest is involved, the injuries can be very severe, including exposure of and injury to internal organs. Several victims have died from bleeding without evidence of strangulation or cervical spine injury. As we are all aware, because wild animals are kept as pets or in zoos, injuries by big cats can occur anywhere.

Our thoughts and prayers are with the family and friends of the victim of this unfortunate happening.

Tags: jaguar attack, jaguar, medical, physician, health, wilderness medicine, outdoor medicine, healthline

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Weak Ankles

If you have a tendency to twist your ankles while hiking or running, you may be prone to sprained ankles. This is an extremely common affliction, and ruins outdoor adventures and athletic endeavors on a regular basis. Are high-topped hiking boots, tape, or ankle braces the only solutions?

Unfortunately, there aren’t any great exercises to strengthen an ankle joint, because the structural integrity of the joint is provided by ligaments, which cannot be strengthened or tightened by exercise. If your ankle tends to twist and “sprain,” which is stretching and/or tearing of the ligaments, then you need to keep it in a stable situation. For climbing and hiking, this is best accomplished with high-topped shoes or boots. They don’t necessarily need to be heavy and clunky – they just need to provide enough support so that your ankle can not be easily twisted (or bent) in or out. Thin-fabric high-topped sneakers won’t give you much support, but some of the intermediate weight hiking shoes are excellent. Be certain that the base of the shoe is wide enough to provide good lateral stability, and that the shoes have a decent arch. Wrapping (e.g., with an elastic bandage wrap) or taping your ankles, as do athletes prior to competition, also provides support, but this requires expertise and an extra effort. There are lightweight cushioned splints that can be worn over your foot and ankle while inside a low-topped shoe, but they are not very comfortable when worn over a great distance.

How else do you protect your ankles? Be careful on rocky, steep, and/or slippery terrain. Use adjuncts, such as hiking poles, to prevent falls. When you are tired and more prone to be weak, achieve a rest period. Train for the environment and anticipated level of exertion.

Tags: ankle sprain, ankle, medical, sprain, health, wilderness medicine, outdoor medicine, healthline

photo courtesy of Hiking in Colorado

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Clean Planet Association

It is difficult to envision that there would be a Wilderness Medical Society if there was no wilderness, or if we degraded our environment to the point that we significantly shrank the wilderness. Although the thrust of this blog is to inform readers about medical issues, I think it's important for all of us to be reminded from time to time about ways in which we can help preserve and improve the natural environment.

The Clean Planet Association is an organization with a vision "to help everyone become aware that the well being of the planet is his or her responsibility." The aim of the association is to support local populations in their efforts to clean up and maintain nature sites. We all should share in that responsibility. A candy wrapper or aluminum container left by a lakeside does not gather the notoriety of an oxygen cylinder discarded at the base camp of Mount Everest, but the thought is the same. Everyone should do their part to "leave no trace," pack out what they pack in, and encourage travelers and trip operators to show the same respect for the land that they show for their bodies.

While the website is not extensive, it says a great deal in a brief, but very focused message to each of us. By adopting a culture of preservation and respect for the environment, we can establish the only approach that offers our planet a reasonable chance for survival beyond our current ethic of consumption and disregard for future generations.


Tags: Clean Planet Association, environment, medical, physician, health, wilderness medicine, outdoor medicine, healthline

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Learning First Aid

Many experts on education believe that first aid is taught effectively in a structured setting where there is hands-on experience. But where to begin? If you are a layperson without any special medical training, you might begin with an American Red Cross-type program that covers the basics of first aid, including rescue breathing and cardiopulmonary resuscitation (CPR). Wilderness medicine is the application of medical knowledge in an outdoor environment, with additional instruction on situations related to special situations, such as cold, heat, altitude, etc. So, once you have a reasonable first aid background, you then need to add the special knowledge needed to be able to manage medical situations outdoors. This very often depends upon your ability to improvise.

There are a number of venues for wilderness medicine education. The National Outdoor Leadership School (NOLS), Outward Bound, Advanced Wilderness Life Support, and other outdoor education organizations have programs that teach medicine for the outdoors. From time to time, the Wilderness Medical Society holds educational seminars for laypersons, and often holds them for medical professionals. You may be able to learn about programs through a local outdoor retailer, such as Recreational Equipment Incorporated (REI). There are unique local programs, such as the ones that used to be sponsored in the San Francisco Bay Area by the Mountain Medicine Institute.

Regardless of where you begin, you owe it to yourself, friends, and family to take the time to learn what you can about wilderness medicine, before you need the knowledge and skills in a real life situation. It is more than important to be smart, and to be prepared.

Tags: first aid, education, medical, physician, health, wilderness medicine, outdoor medicine, healthline

photo courtesy of Newcastle Wilderness Medicine Society

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Hypothermia Frostbite And Other Cold Injuries

The 141-page paperback second edition of Hypothermia Frostbite And Other Cold Injuries, by Gordon Giesbrecht, Ph.D. (“Dr. Popsicle”) and James A. Wilkerson, M.D. is available from The Mountaineers Books for $17.95 U.S. While only in its second edition, this book is likely to become a classic. Written for medical professionals, it is a succinct guide to prevention of and survival from hypothermia, and rescue and treatment of hypothermic victims. The physiology and pathophysiology of hypothermia are very well explained and the information on cold water immersion is particularly comprehensive. As would be expected from the world’s expert on immersion hypothermia, the recommendations for rescue are plentiful and superb. I particularly enjoyed the section on cold weather clothing, which includes useful information in order to understand choices of clothing and how best to prepare for the cold. The discussion on frostbite reflects the fact that we have not seen any real advance in clinical approach for decades now. This will be a useful “refresher” book for knowledgeable medical professionals who wish to be conversant with the most recent accepted approaches to hypothermia, and a very important book for the library of any health care provider who may be called upon to assist in the rescue and treatment of a hypothermic human being.

Tags: hypothermia, frostbite, cold injuries, physician, health, wilderness medicine, outdoor medicine, healthline

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Using a Tourniquet

Tourniquets have been a staple of emergency field care for centuries. The usual application of a constriction bandage to staunch the flow of bleeding is an emergency maneuver that takes the risk of losing a limb (from loss of circulation) in order to save a life. Other uses for constriction bandages generally involve severe envenomations, such as from venomous snakes or marine animals, in order to impede the distribution of life-threatening venom.

Again, a tourniquet is indicated only in a life-threatening situation and is best applied by an experienced person. Only in the case of torrential bleeding is a tourniquet more advantageous than continuous pressure, because pressure properly applied is very useful. The decision to apply a tourniquet is one in which a limb (hand, foot, arm, or leg) might be sacrificed to save a life.

A tourniquet should be applied to the limb between the bleeding site and the heart, as close to the injury as is effective to control the bleeding. The reason for placing it close to the bleeding is to preserve as much living tissue (which is "above" the tourniquet) as possible. The tourniquet should be tightened just to the point where the bleeding can be controlled with direct pressure over the wound. If you must leave the victim after applying a tourniquet, and therefore can no longer apply direct pressure, be certain to check that it is still effective after you have released pressure.

To construct a tourniquet, use a 2 to 4 inch (5 to 10 centimeter) bandage — not something thin (like a string, wire, or electric cord) that might cut through the skin. Wrap the bandage around the limb several times, then tie half or an entire square knot, leaving loose ends long enough to tie another knot on top of the first knot (as part of the next step). The next step is to place a stick or stiff rod over the first knot, then tie it firmly in place with the loose ends. Twist the stick until the bandage is tight enough to stop the bleeding, then secure it in place with another cloth, tape, or circular bandage.

If possible, the tourniquet should be loosened or released briefly every 10 minutes to see if it is still necessary. Some authorities recommend loosening it after 5 minutes, which might be all right if the bleeding is not torrential. If the bleeding can now be controlled with direct pressure, don't re-tighten the tourniquet, but keep a very close watch on the situation. If the original wound damaged or severed a very large blood vessel, it is likely that you will need to keep the tourniquet in place for more than 10 minutes. Always keep a tourniquet in plain view, so that it doesn’t get left in place longer than necessary just because someone didn’t know or forgot it was there.

For the benefit of EMS (emergency medical services providers, such as EMTs [emergency medical technicians] or paramedics), the question arises whether a tourniquet should be loosened prior to establishment of an intravenous (IV) line and fluid administration. I believe the guidelines above should suffice. If a person is in a very precarious position with respect to hemorrhage (low blood pressure or shock), then I would err on the side of caution and resuscitate with fluid prior to releasing the tourniquet. On the other hand, if the patient was "stable" (reasonable blood pressure, normal mental status, etc.), and I might save the limb by loosening the tourniquet, I might opt to follow that pathway. It is a judgement call made at the scene by someone willing to accept responsibility for the outcome.

Tags: tourniquet, bleeding, hemorrhage, physician, health, wilderness medicine, outdoor medicine, healthline

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Avalanches

Recently, there was a huge avalanche in Colorado that crossed a highway in the Arapaho National Forest. When someone is buried underneath the snow, there are issues of trauma and asphyxiation, but what is less frequently discussed in the medical literature is the actual formation of avalanche conditions. What follows below is a very condensed version of some information written in the forthcoming 5th edition of the textbook Wilderness Medicine in a chapter entitled “Avalanches,” authored by Knox Williams, Dale Atkins, and Colin Grissom.

Although snow cover appears to be nothing more than a thick, homogeneous blanket covering the ground, it is one of the most complex materials found in nature and goes through significant changes in relatively short periods of time. All snow crystals are made of water molecules, but local environmental conditions control the type and character of snow found at a given location. At a single site the snow cover varies from top to bottom, resulting in a complex layered structure.

In general, thicker layers represent consistent conditions during one storm, when new snow crystals falling are of the same type, wind speed and direction vary little, and temperature and precipitation are fairly constant. Thinner layers, perhaps only millimeters in thickness, often reflect conditions between storms, such as the formation during fair weather of a melt-freeze crust, a period of strong winds creating a wind crust, or the occurrence of surface hoar, the winter equivalent of dew. Delicate feather-shaped crystals of surface hoar deposited from the moist atmosphere onto the cold snow surface overnight offer a beautiful glistening sight as they reflect the sun of the following day. However, they are very fragile and weak, and once buried by subsequent snowfalls, they may be major contributors to avalanche formation.

One property of snow is strength, or hardness, which is of great importance in terms of avalanche formation. The arrangement of the ice skeleton and the changing density produce a wide range of conditions. The denser the snow layer, the harder and stronger it becomes, as long as it is not melting.

Wind can alter the shape of new snow crystals, breaking them into much smaller pieces that pack very closely together to form wind slabs. These in turn may possess a density 5 to 10 times that of new delicate flakes falling in the absence of wind. These processes occur at different times and locations at the surface of the snow cover and are buried by subsequent snowfalls, so a varied layered structure results.

After snow has been deposited on the ground, the density increases as the snow layer settles vertically or shrinks in thickness. Because an increase in density equals an increase in strength, the rate at which this change occurs is important with respect to avalanche potential. Snow is highly compressible because it is composed mostly of empty air pocket within an ice skeleton of snow crystals. Under very cold conditions, the original shapes of the snow crystals are recognizable after they have been in the snow cover for several days or even a week or two. As temperatures warm and approach the melting point, such shapes disappear within a few hours to a day.

Averaged over 24 hours, snow temperatures generally are coldest near the surface and warmest near the ground at the base of the snow cover. Warm air contains more water vapor than does cold air; this holds true for the air trapped within the snow cover. The greater the amount of water vapor, the greater the pressure. Therefore both a pressure gradient and a temperature gradient exist through the snow cover.

Depth hoar is of particular importance to avalanche formation. It is very weak because there is little or no cohesion or bonding at the grain contacts. Depth hoar or temperature-gradient snow layers can be compared to dry sand. Each grain may possess significant strength, but a layer composed of grains is very weak and flimsy because the grains lack connections. Thus depth hoar is commonly called “sugar snow.” In the cold, shallow snow covers of a continental climate, such as that of the Rocky Mountains, a gradient of this magnitude is common within the first snow layers of the season. Therefore a layer of depth hoar is frequently found at the bottom of the snow cover, and the resulting low strength becomes a significant factor for future avalanches.

There are two basic types of avalanche release. The first is point-release, or loose snow, avalanche. A loose snow avalanche involves cohesionless snow and is initiated at a point, spreading out laterally as it moves down the slope to form a characteristic inverted V shape. A single grain or a clump of grains slips out of place and dislodges those below on the slope, which in turn dislodge others. The avalanche continues as long as the snow is cohesionless and the slope is steep enough. This type of avalanche usually involves only small amounts of near-surface snow.

The second type of avalanche, the slab avalanche, requires a cohesive snow layer poorly anchored to the snow below because of the presence of a weak layer. The cohesive blanket of snow breaks away simultaneously over a broad area. A slab release can involve a range of snow thicknesses, from the near- surface layers to the entire snow cover down to the ground. In contrast to a loose snow avalanche, a slab avalanche has the potential to involve very large amounts of snow.

As the initial crack forms in the unstable snow, elastic energy is released, which in turn drives the crack further, releasing more elastic energy, and so forth. The ability of snow to store elastic energy is essentially what allows large slab avalanches to occur. As long as the snow properties are similar across the avalanche starting zone, the crack will continue to extend, allowing entire basins, many acres in area, to be set in motion within a few seconds.

Tags: avalanche, snow avalanche, medical, physician, health, wilderness medicine, outdoor medicine, healthline

photo by Colin Grissom

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