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[MEDSCAPE]:10种常见的野外或环境疾病及损伤
2017年06月15日 时讯速递, 进展交流 暂无评论

10 Common Wilderness and Environmental Medical Illnesses and Injuries

William Selde, MD, FAWM; Will Smith, MD, FAWM, Paramedic | June 1, 2017

Outdoor recreational activities in wilderness environments or remote locations have become increasingly popular, with estimates of US consumer spending reaching $646 billion each year. [1] The growth of interest in these pastimes necessitates an understanding of the potential related illnesses and injuries, particularly in areas where resources may be limited.

Can you identify and acutely manage the following wilderness and environmental illnesses and injuries, some of which may be life threatening without early recognition and prompt treatment?

The images show severe frostbite of both feet in a 60-year old patient.

Altitude Sickness

Image courtesy of Paralikar SJ, Paralikar JH. Indian J Occup Environ Med. 2010;14(1):6-12. [Open access.] PMID: 20808661, PMCID: PMC2923424.

The image shows the relationship between altitude, barometric pressure, and inspired oxygen.

Altitude sickness generally occurs in individuals who ascend rapidly to elevations above 8000 feet (2438 m). [2] It is commonly classified as acute mountain sickness (AMS) and can progress to high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE). [2,3]

AMS signs/symptoms include headache, nausea, and fatigue; these are the most common forms of altitude illness. [2,3]

HAPE and HACE

 

Images courtesy of Shrestha P, Pun M, Basnyat B. Extrem Physiol Med. 2014;3(1):6. [Open access.] PMID: 24636661, PMCID: PMC3984695.

HAPE and HACE are severe forms of altitude illness that lead to the development of fluid in the lungs (shown) or brain swelling, respectively.

The left chest radiograph shows HAPE in a Himalayan trekker. Note the pulmonary infiltrates in the right lung, especially in the right mid and lower lung zones, and normal heart size, indicative of non-cardiogenic pulmonary edema. The right chest radiograph was obtained 2 days later at lower altitude and reveals rapid resolution of the edema.

HAPE signs/symptoms include shortness of breath, activity intolerance, and a dry cough that transitions to a wet, pink, frothy cough with severe illness. [2,3]

HACE may manifest as headache, changes in alertness, and lack of coordination. These can progress to coma and death. [2,3]

Prevention and treatment

Image courtesy of Taylor AT. Rambam Maimonides Med J. 2011;2(1):e0022. [Open access.] PMID: 23908794, PMCID: PMC3678789.

Ascending slowly over the course of days allows for acclimatization and can reduce the incidence of altitude illness. Acetazolamide, a diuretic, may aid in acclimatization. [2,3]

Definitive treatment for altitude illness is returning to a lower elevation. [2,3] Mild AMS signs/symptoms usually resolve with rest and hydration. Ibuprofen may be used to treat a mild headache.

Severe manifestations, including difficulty with coordination, changes in behavior, or shortness of breath at rest, require immediate removal to a lower altitude. [2,3] Dexamethasone, a steroid, may help to temporize severe illness, but this agent will not definitively treat it. If immediate evacuation is not possible, portable inflatable hyperbaric chambers (shown) can be used to begin therapy.

Heat Illness

Adapted table courtesy of US Department of Labor, OSHA.

Heat illness occurs along a continuum ranging from mild heat cramps to heat stroke, coma, and death. The elderly, the very young, those with chronic disease, individuals using drugs (including alcohol), and people who are active in areas with elevated temperatures are at the highest risk of suffering from heat illness. [2,3]

Heat cramps result from excessive salt and water loss from profuse sweating in individuals whose bodies are attempting to rapidly lose heat. [4]

Heat exhaustion, in which the body overheats, may occur with a significant loss of water.

Heat stroke is the most severe form of heat illness and is a medical emergency. It typically manifests with a body core temperature of 105.8°F (41°C) or higher. [4]

The table is adapted from responses to heat-related emergencies in workers by the Occupational Safety & Health Administration (OSHA). Signs/symptoms of, and acute management for, heat cramps, heat exhaustion, and heat stroke are shown.

Passive versus exertional hyperthermia

Images courtesy of Flickr/Jessica Merz (left) and Wikimedia Commons/Eckhard Pecher (Arcimboldo) (right).

Heat illness is often categorized as passive or active.

Passive hyperthermia is more likely to affect individuals at the extremes of age, and it occurs when the body is in an environment that is too hot for too long, such as a child left in a car on a hot day. [2,3]

Exertional hyperthermia often occurs at lower ambient temperatures than passive hyperthermia, and it results from an inability to lose heat created by the activity of the body. [2,3]

Prevention and treatment

Still image from "Sun stroke treatment" courtesy of Mihir Das via YouTube (Creative Commons Attribution license (reuse allowed)).

Gradual acclimation to increased temperatures may reduce the incidence of heat illness by altering the body's response to high temperatures (eg, changes in the composition of sweat and the temperature at which sweating begins).

Treatment for heat illness includes transferring the person to a cooler environment; administering chilled, but not ice cold, fluids if the person is able to drink; and using evaporative cooling to lower the body temperature. [2,3]

Cooling is best accomplished by covering the person with a light cotton cloth; wetting them with cool, but not cold, water; and using a fan to speed up evaporation.

Avoid overcorrection to hypothermia by stopping active cooling at 100°F (37.8°C).

Hypothermia

Image of homeless person courtesy of Flickr/daveynin; image of ECG segments courtesy of Mine T, Sato I, Kishima H, Miyake H. J Med Case Rep. 2012;6:429. doi: 10.1186/1752-1947-6-429. [Open access.] PMID: 23272675, PMCID: PMC3760449.

Hypothermia results from an inability of the body to maintain normal temperature (average: 98.6°F [37°C]). It is generally categorized as mild to moderate and severe.

Risk factors for hypothermia are similar to those for hyperthermia, including being at the extremes of age, use of drugs (including alcohol), and having chronic disease. [2,3]

Signs/symptoms of hypothermia include shivering, loss of coordination, and confusion.

The electrocardiogram (ECG) segments are from an elderly patient with left ventricular systolic dysfunction following accidental hypothermia. Segment A depicts Osborn waves ( arrows) in leads V4-V6 at presentation. Segment B shows the same leads in the patient following warming.

Mild to moderate and severe hypothermia

Images courtesy of Lund FK, Torgersen JG, Flaatten HK. Cases J. 2009 Aug 18;2:6204. [Open access.] PMID: 19918562, PMCID: PMC2769272. | Darren Baker /Dreamstime (Top inset)

The images are from a case of a 48-year old kayaker who capsized in 38°F seawater and was found by an ambulance helicopter with cardiopulmonary arrest and severe hypothermia. He received cardiopulmonary resuscitation (bottom right) and cardiopulmonary bypass was used for rewarming. Return of circulation was achieved almost 3.5 hours after cardiac arrest. He recovered fully. Heart rate data was taken from his pulse watch from before the accident until arrival to the OR (top).

A person with mild to moderate hypothermia will respond to passive rewarming, such as the use of additional blankets or a sleeping bag, or transfer to a warmer environment. [2,3]

Severe hypothermia occurs when the body's shivering reflex disappears; consequently, the affected person is no longer able to warm themselves. [2,3] Patients with severe hypothermia require active rewarming, such as being placed in a sleeping bag next to a person with normal temperature or being surrounded with hot water bottles and wrapped in a thick layer of insulation if definitive medical care is not immediately available. [2,3]

Frostbite

Image courtesy of Chang N, Nunn R, Milner SM, Price LA. Eplasty. 2013;13:ic37. Epub 2013 Mar 15. [Open access.] PMID: 23573343, PMCID: PMC3601455.

Frostbite occurs when the skin and underlying tissues are frozen. It is classified much like burns on the basis of the depth of the frozen skin, such as the following [2,3]:

First-degree frostbite: Occurs in the epidermis, the outermost layer of skin; signs/symptoms include redness and pain. It is fully reversible.

Second-degree frostbite (shown): Occurs in the epidermis and dermis and results in blister formation and pain. Usually, this will resolve on its own with minimal long-term effects

Third-degree frostbite: Occurs when the full thickness of the skin and, often, the deeper tissues are frozen. These areas may or may not heal on their own and sometimes require delayed amputation or other definitive wound treatment.

Prevention and treatment

Images courtesy of Ramdass MJ. Cases J. 2009;2:6635. [Open access.] PMID: 20181167, PMCID: PMC2827043.

The images are from a patient with frostbite that required bilateral below knee amputations. The left image shows the feet 2 days after presentation. The right image reveals the completely mummified feet 3 weeks after the initial injury.

Preventive measures against frostbite include protective covering, such as loose layers of clothing, hats and gloves, and socks and boots, as well as keeping hydrated. [5]

Treatment of frostbite involves gentle and gradual warming of the affected areas. [2,3,5] This is often best accomplished with the use of a warm, but not hot, water bath. Significant pain and swelling often accompany rewarming.

Note that warming should only occur when it is certain that the frostbitten part will be protected from any further cold exposure. Blisters should be left intact whenever possible, and routine wound care should be initiated for any open skin.

Dehydration

Image courtesy of Dreamstime/Martinmark.

Dehydration involves the loss water from the body, such as through perspiration, respiration, and urination. Often, this leads to abnormalities in the balance of electrolytes in the body.

Extremes in age, the presence of chronic medical conditions, drug use (including caffeine and alcohol), hyperthermia, and hypothermia are risk factors for dehydration. [3]

Signs/symptoms of dehydration include general malaise, feeling dizzy or faint, nausea, vomiting, and muscle cramps. [3]

Loss of fluid and electrolytes

Image courtesy of Dreamstime/Czuber.

The electrolytes most often affected in dehydration are sodium and potassium. The loss of water without the loss of electrolytes causes hypernatremia.

Perspiration due to high temperatures and exertion may lead to excessive loss of sodium. This condition can be exacerbated if only water is ingested. Water poisoning occurs when the body's electrolytes are diluted by the ingestion of too much water, which may occur regardless of exposure to extreme temperatures.

Physiologic alterations that cause extremely low or high electrolytes levels may be life threatening.

Prevention and treatment

Images courtesy of Wikimedia Commons/tshrinivasan (left); Dreamstime/Jim Delillo (right); and US Army, Ft Detrick (center inset).

The appropriate amount of fluid intake is best measured by urination. [3] In well-hydrated individuals, the urine should be light yellow to near colorless in appearance.

A balanced electrolyte solution is key for hydration, to prevent both dehydration and electrolyte imbalance. Salt tablets should be avoided. [3] In very hot conditions, the hydration fluid should be slightly chilled but not ice cold. In very cold conditions, the fluid should be warm but not scalding hot.

For individuals with mild or moderate dehydration, gradually administer fluid replacement and encourage rest. [6] In hot conditions, if possible, remove the person from direct sunlight and out of the heat, and loosen or take off extra clothing. In cold conditions, rest and gradual fluid replacement remain essential measures. Keep the affected person's clothing on but loose enough to allow proper circulation.

Patients with severe dehydration require emergent medical management.

Snake Bites

Image courtesy of Wikimedia Commons/Mikael Häggström.

Although most snakes in North America are not dangerous to humans, pit vipers and coral snakes are two types of venomous snakes in the United States whose bites may be life threatening. [7]

Pit vipers include rattlesnakes, fer de lances, copperheads, water moccasins, and others. [8] Coral snakes belong to the same family as cobras. [9] However, even nonvenomous snake bites require medical attention. [2,3]

Pit vipers

Image of the head of a Malabar pit viper (Trimeresurus malabaricus) courtesy of Wikimedia Commons/L Shyamal Wynaad.

Pit vipers are identified by a pit below their nostrils; a broad, arrow-shaped head; slant "cat eyes"; a single set of ventral scales; and often, but not always, a collection of rattles at the end of their tails. [2,3]

Most pit viper venom is directly toxic to tissues and blood cells. Although all bites will contain venom, snake size is not correlated with the amount of venom. Strikes may or may not be preceded by a warning rattle.

Note that rattle snakes are capable of striking half their body length. [2]

Coral snakes

Image of an Eastern coral snake (Micrurus fulvius) courtesy of Wikimedia Commons/Norman Benton.

Coral snakes are identified by the red-on-yellow bands that circle their bodies. [2,3] Their venom is neurotoxic and leads to progressive paralysis, with paralysis onset typically occurring 30-60 minutes after the bite. [2,3]

The bite appearance of coral snakes is more saw-like as opposed to the quick puncture of a pit viper.

Prevention and treatment

Images courtesy of Rao CP, Shivappa P, Mothi VR. J Occup Med Toxicol. 2013;8(1):7. [Open access.] PMID: 23522302. PMCID: PMC3614463 (left); and Harris JB, Scott-Davey T. Toxins (Basel). 2013;5(12):2533-71. [Open access.] PMID: 24351716, PMCID: PMC3873700 (right).

The left image shows a complete snake bite mark on the right thenar eminence. The right image depicts localized necrosis on the left foot in a different patient following a bite from a fer de lance ( Bothrops asper).

When possible, avoiding interactions with snakes is important. This includes not stepping on or placing hands in wood or rock piles or areas that can't be seen well. Wearing clothing designed to resist snake bites, or a minimum of heavy boots and long pants in high-risk areas, is also an important measure.

If bitten by a snake, try to identify the snake if possible—but do not risk another bite. Taking a picture of the snake with a digital camera or mobile phone may help in its identification.

General treatment for snake bites includes rinsing the bite area with clean water. [2,3] DO NOT cut the bite marks or attempt to suck out the venom.

Controversy exists regarding the use of pressure dressings. But, generally this is not recommended for North American snake bites.

As noted earlier, even nonvenomous snake bites require medical attention. All snake bites will likely need antibiotics, and some individuals may require antivenin and other supportive treatment.

Anyone with a known venomous snake bite, significant pain, swelling, or weakness should seek emergent medical attention. [2,3]

Lightning Injuries

Images courtesy of Axel Rouvin (left) and James Heilman, MD, (right), both via Wikimedia Commons.

Lightning is an extremely high-voltage, direct-current, electrical event that occurs over milliseconds. Injury can occur from a direct strike, when the current splashes off a nearby object, and/or when the current flows through another object to the victim. [2,3]

Lightning strikes can directly cause burns, loss of consciousness, seizures, and paralysis, as well as indirectly cause blast trauma, such as ruptured eardrums and broken bones.

The Lichtenberg sign/figure is a unique cutaneous finding with a branching, fern-like pattern [10] that may occur with lightning strikes. [2,3] A starburst–type, stippling skin burn can also be seen with lightning injuries.

Lightning safety and lightning injury treatment

Adapted image courtesy of the National Oceanic and Atmospheric Administration (NOAA).

The best defense against lightning injuries is to avoid lightning. [11] Outdoor safety and prevention tips during thunderstorms include the following [2,3,11]:

  • Keep in mind, "When thunder roars, go indoors." (If an enclosed shelter is available.)
  • Stay away from exposed areas such as ridge lines or open fields. Avoid shallow caves and depressions.
  • Avoid solitary tall objects; seek multiple small objects (eg, a stand of short trees).
  • Spread out large groups of people so that the everyone is not injured in one strike.
  • Remove metal objects such as jewelry (watches, rings, necklaces), belt buckles, etc.
  • Stay away from tent poles, and other metal objects as these may function as lightning rods.
  • Insulate yourself from the ground (eg, rubber sleeping mat), if available; otherwise, crouch down in a ball-like position and hands over the ears.
  • Individuals struck by lightning who are not breathing should receive cardiopulmonary resuscitation (CPR) first – reverse triage, followed by emergent medical care as soon as possible. [2,3] Patients with burn wounds require routine burn care.

Toxicodendron (Poison Ivy) Exposure

Images courtesy of SWMNPoliSciProject (top left), Freekee (top right), and Tim Vasquez (bottom) all via Wikimedia Commons.

The genus Toxicodendron includes poison ivy ( T radicans) ( top left), poison sumac ( T vernix) ( top right), and (western) poison oak ( T diversilobum) ( bottom). [12]

Toxicodendrons contain the oily compound urushiol; exposure to the sap from the leaves of these poisonous plants may cause a delayed hypersensitivity reaction, although not all who come in contact with urushiol will have an allergic reaction.

Urushiol can be transferred to humans from other animals (eg, dogs) or objects (eg, backpacks). [2,3] Blisters that may develop following urushiol exposure do not contain, and will not spread, urushiol. [2,3,13]

Prevention and treatment

Images of urushiol-induced contact dermatitis on bilateral arms 72 hours after contact with poison ivy courtesy of Wikimedia Commons/Larsonia.

Wear long sleeves, long pants, and gloves; separately launder exposed clothing in hot water with detergent. [13] Barrier skin creams/lotions that contain bentoquatum may offer some protection before contact.

If urushiol exposure is recognized, immediately rinse the affected skin with water to keep the compound from reacting with the skin; soap is not recommended. [3]

Mild cases of Toxicodendron dermatitis often require routine wound care as well as antihistamines for itching.

Moderate to severe cases may require at least 14 days of oral steroid treatment. [3]

Tick-Borne Illnesses

Images of black-legged tick larva (far left), nymph (second from left), adult male (second from right), and adult female (far right) courtesy of Flickr/Fairfax County.

Ticks are one of the most common vectors of disease transmission in the United States. [3] They are generally more active in the spring and summer months and prefer to attach to areas of moist, protected skin, such as the armpits, groin, and scalp. [2,3]

Tick bites are more than a nuisance; they can cause bacterial infections and, rarely, an ascending paralysis. [14]

Prevention and treatment

Images courtesy of Medscape; .gif courtesy of Sam Shlomo Spaeth.

Patients exposed to tick-endemic areas should wear long-sleeved, light-colored clothing. [14] Lighter colors allow for easier identification of ticks. Over-the-counter chemical repellents with DEET (N,N-diethyl-3-methylbenzamide) and picaridin are available as sprays or lotions. Permethrin is an acaricide that can be applied to clothing and is used in conjunction with chemical repellents.

Remove any ticks as soon as possible by using tweezers to pinch close to the skin (not the body) and pulling straight out. [2,3,14] Avoid causing the tick distress by pinching its body, burning it, or covering it in petroleum jelly. Ticks removed within 36 hours of attachment do not require treatment for Lyme disease. [3]

Individuals with any rash or fever following a known or suspected tick bite should seek medical attention. [14]

Hymenoptera Stings

Image of a yellow jacket wasp courtesy of Flickr/James.

The order Hymenoptera includes bees, wasps, and ants (or "membrane-winged insects"). [15] Their stings can cause pain, erythema, inflammation, and itching at the affected site.

More importantly, Hymenoptera stings may cause an immediate life-threating anaphylactic reaction in certain individuals. At least one sting is required to sensitize an individual.

Images courtesy of Ittyachen AM, Abdulla S, Anwarsha RF, Kumar BS. Int J Emerg Med. 2015;8:6. [Open access.] PMID: 25852776, PMCID: PMC4385238.

These images of mild ulcerations on the head and upper limb are from a male agricultural worker who was stung by multiple wasps (species unknown). He developed multiorgan dysfunction within 2 days of being stung but survived following aggressive clinical management, including intravenous fluids, steroids, antihistamines, and prophylactic antibiotics; multiple hemodialysis sessions; and transfusions with fresh frozen plasma and with platelet concentrates. He did not require mechanical ventilation.

Prevention and treatment

Image of the stinger of a black bee (Apis mellifera mellifera) courtesy of Wikimedia Commons/SuperManu.

Preventive measures against insect stings include the following [16]:

  • Wear clean, light-colored, smooth-finished clothing that covers as much of the body as possible, and bathe daily.
  • Avoid perfumed soaps, shampoos, and deodorants, as well as bananas and banana-scented toiletries; don't wear cologne or perfume.
  • Avoid flowering plants when possible.

If stung, wash the site with soap and water. [16] If stung by a bee, remove the venom sac (shown) by scraping it away [2,3,16]; never squeeze the stinger or use tweezers. [16] Apply ice to reduce swelling, and avoid scratching the affected site to prevent increased swelling and itching, and to reduce the potential for infection. [16]

Treat mild symptoms with over-the-counter medications and cool compresses. Monitor for signs of infection (eg, fever). [2,3]

Severe allergic reactions, including swelling or any difficulty breathing, should be treated with epinephrine. [2,3] Note that reactions can recur after an initial dose of epinephrine and may require repeat doses—immediately seek emergent medical care. [2,3]

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