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Medicine for the Outdoors

Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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The Desert and Desert Survival 3

This is the fifth post based upon educational sessions and syllabus material presented at the Wilderness Medical Society Annual Meeting & 25th Anniversary held in Snowmass, Colorado from July 25-30, 2008. This post continues the discussion about the desert and desert survival, based upon the extensive knowledge of Dr. Edward J. (“Mel”) Otten, who is Professor of Emergency Medicine and Pediatrics, and Director of the Division of Toxinology at the University of Cincinnati.

Survival Kit:

The survival kit must be carried at all times, have quality equipment and supplies, and be protected from the elements. Each item should have multiple uses if possible. There must be items that can be used for shelter, signaling, fire building, first aid, and other uses. Many items will routinely be carried by most hikers and backpackers, but some specialized items should be added. One’s clothing is the basic survival shelter and if properly selected will be the first step in protection from the climate. General use items include a Swiss Army knife with as many blades as possible. The “Swiss Champ” includes among many other features a magnifying glass, which is quite useful for removing cactus spines or starting fires. Parachute cord (eight strand) has multiple uses, including shelter construction, creation of snares, and fishing nets and lines. A signal mirror, whistle, matches/ metal match/lighter, first aid supplies, compass, safety pins, water disinfection tablets, and plastic bags can be stored in a relatively small container that should be kept on one’s person at all times. The first aid kit should contain bandages, insect repellant, sunscreen, lip balm , antiseptic ointment, aspirin,
antihistamines, tape, and any prescription medications.

The desert survival kit should include a 5 foot by 5 foot piece of plastic , 4 foot length of plastic tubing, and metal cup (all for making a solar still), emergency blanket ( silver on one side, red on the other), extra sunglasses/eye protection, nylon canteen (minimum 5 quart size), and extra sunblock.

The “Rule of 3’s” gives us a priority list for the survival. One can live three minutes without oxygen, three hours without warmth, three days without water, and three weeks without food.

The key to desert survival is water. Unfortunately water weighs 8 pounds (3.6 kg) per gallon( 3.8 L) and each individual needs up to 2 gallons (7.6 L) per day. Always carry as much water as possible. Collapsible canteens can carry several quarts of water and keep it cooler ( because the surface heat absorption to volume is less ) than can hard plastic or metal. Drink at every stop and while hiking if using a drinking tube. Flavoring and cooling water increase palatability and thus consumption. Most hikers do not carry enough water for more than one day, so having a method for acquiring water is mandatory. Solar stills, vegetable stills, digging along arroyos and in dry lake beds, wiping dew from plants in the early morning, and extracting water from succulent plants are all methods for obtaining water in a desert survival environment, but minimal water may be acquired by these methods.

While there are a number of methods for obtaining water in the desert,
minimizing water loss is an essential strategy for a human with limited water resources. All desert plants and animals have developed adaptive mechanisms for conserving water and humans, if the are to survive, must develop strategies for conserving their sweat, not their water. While this may be intuitive, most desert travelers neither limit their travel to cooler times of the day nor their work activities to the shade. Employing a strategy of resting in the shade from 1000 hours until 1500 hours, drinking adequate water based on the appearance of the urine (see below), and keeping as much skin covered as possible has decreased the number of heat casualties in the military during training exercises.

While thirst and amount of sweat on clothing are poor indicators of hydration status, the color and amount of urine produced can roughly estimate it. The darker the urine, the more concentrated and the greater the degree of dehydration. If potable water is available, it should be consumed; it is better to conserve sweat rather than water. If there is a limited amount of water , food should not be eaten unless the food contains a large amount of water. The metabolism of food, especially protein and fat, and excretion of waste products requires potentially unnecessary consumption of water. Only potable water should be drunk, because vomiting and diarrhea caused by contaminated water could quickly become fatal in the desert. Water obtained from lakes, streams, wells, or springs should be considered contaminated and must be made potable prior to drinking. Water holes may attract dangerous game as well as potential food.

Desert water may be found by looking for animal sign, such as trails or spore. Some plants, such as cottonwood, sycamore, willow and cattails, may be indicators of water. Water may sometimes be found by digging at the outside bend of a dry riverbed or stream (arroyo and wadi are terms used to indicate rain run-off channels that may contain water during the rainy season). Rainwater, dew and water obtained from a solar or vegetable still is relatively potable. Urine, seawater, alkaline pools and brackish water should never be drunk. They contains large amount of solutes that would require more water to excrete than they contain and hasten dehydration and renal failure. Liquid from automobile radiators is contaminated with glycols and should not be drunk or used in solar stills. Many plants, such as barrel cacti and traveler’s tree, and animals such as the desert tortoise contain water that can be extracted in an emergency.

A solar still may yield a small amount of water. It can be constructed by placing a 5 feet by 5 feet piece of clear plastic over a hole 3 to 4 feet in diameter and dug 3 to 4 feet deep in the ground into which vegetation, urine, or brackish water has been placed. Solar energy causes water to evaporate within the hole and collect on the underside of the plastic. Because it cannot escape it will drip back into a container placed at the bottom of the hole. A tube can be attached to the inside of the container so that the water can be drunk without dismantling the still. A plug should be put in the drinking end of the tube to prevent clogging. The amount of water produced depends on the amount of moisture in the hole, amount of sunshine directed at the still, and the size of plastic sheet. A still dug into a dune or dry sand will not produce much water. Dew, rainwater and edible animals may fall into the still as a bonus. Moisture can be wiped off of plants during early morning and can be squeezed from the pulp of certain plants, such as yucca. Milky, bitter, or sour pulp should not be used and the pulp should not be eaten. Water can be made potable by boiling or using filters or chemicals.

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About the Author

Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.