Environmental Exposure

Location of missions must be taken into account when considering threats, such as cold and heat extremes, environmental moisture, and sun exposure. Environmental injury can hinder a team’s effectiveness and pose severe health threats.

During cold weather missions the primary preventive medicine concerns regard frostbite and hypothermia. It is important for team members to be outfitted with appropriate clothing, gear, water availability, and protection. Hypothermia occurs when the body loses heat faster than it is able to generate it. Core body temperature falls below normal, typically defined as a core temperature below 95 °F. It is critical to understand that freezing environmental temperatures need not be present for hypothermia. It tends to occur during cold, windy weather, rapidly changing weather environments, and in those who are wet, exhausted, and poorly dressed. Prevention includes proper clothing, staying dry, avoiding wind, getting rest, and monitoring your fellow team members. Operators are very likely going to be wearing heavy gear and armor that will lead to perspiration. Sweat will lead to evaporative and conductive heat loss and significantly increase the risk of developing hypothermia. Proper head coverage is essential. The TEMS provider must help team leaders to remember work-rest cycles on sustained operations and has a responsibility to ensure that operators have a place to rewarm periodically. These cycles are particularly important for those with extended exposure roles, most notably snipers, spotters, and countersnipers. Warm drinks should be made available if possible. Critically the prevention of a team philosophy of “toughing it out” will help assure that members in need of help will ask for it.

Frostbite occurs at temperatures below freezing in those who are wet, underprepared, and poorly dressed. Frostbite injuries occur on a spectrum from superficial injury to severe, full thickness skin injuries, which can lead to loss of limb or extremity. For the purposes of tactical medicine, recognizing the early stages, known as frostnip, allows the TEMS provider to perform actions to reverse the condition before development of true frostbite.

Frostnip is a superficial, nonfreezing cold injury associated with intense vasoconstriction on exposed skin, usually cheeks, ears, or nose. By definition, ice crystals do not form in the tissue nor does tissue loss occur in frostnip. The numbness and pallor resolve quickly after covering the skin with appropriate clothing, warming the skin with direct contact, breathing with cupped hands over the nose, or gaining shelter that protects from the elements. No long-term damage occurs. The appearance of frostnip signals conditions favorable for frostbite, and appropriate action should be undertaken immediately to prevent injury.

Frostbite occurs when tissue freezes, forming intracellular ice crystals and leading to variable degrees of tissue damage. Although outside the scope of this chapter, there are well-defined degrees of frostbite that correlate somewhat to the better-known descriptions of the severity of burns. Contributing factors to frostbite include the amount of tissue exposed, ambient temperatures, nutritional status, wind chill, nicotine use, previous cold injury, physical activity, and tight-fitting clothing or boots. Severe frostbite can require evacuation for hospital evaluation and result in loss of a team member.

Immersion injury, such as trench foot, can occur during extended operations as well. This disease process was defined during World War I and is caused by prolonged exposure to dampness and cold temperatures. Improper footwear and hygiene are the primary preventable risk factors. The ambient temperature need not be below freezing. Symptoms of trench foot include a tingling and/or itching sensation, pain, swelling, cold and blotchy skin, numbness, and a prickly or heavy feeling in the foot. The foot may be red, dry, and painful after it becomes warm. Blisters may form, followed by skin and tissue dying and falling off. In severe cases, untreated trench foot can involve the toes, heel, or entire foot. ^, Preventative measures, such as waterproof boots, dry socks, massage, and early recognition, are key.

Heat injuries are a serious concern during prolonged operations in warm climates. In hot environments body temperature increases, which places stress on the body’s ability to regulate temperature and can lead to failure of compensatory mechanisms in the body. High humidity interferes with sweat evaporation, leaving radiation of heat as the primary method of cooling. The layers of gear and heavy equipment required in tactical operations reduce the ability to radiate heat to the environment and block wind-driven convection heat loss, adding to the cumulative heat stress and thus increasing the risk of heat injury. By overwhelming the body’s ability to maintain temperature equilibrium, heat illness can occur. The spectrum of disease includes heat cramps, heat exhaustion, and ultimately heat stroke. It is very important for tactical teams to prevent heat-related illness, starting with the MTA consideration of environmental temperature, humidity, and air movement. Prevention of temperature-related injury involves reducing exposure times, work-rest cycling, heating or cooling areas for operators, moisture-wicking base layer garments, and adequate hydration. It is critical that officers feel comfortable informing their commander if they develop early temperature injury to prevent progression to more severe forms. Lastly, overexposure to ultraviolet (UV) light from the sun can lead to sunburn and also contributes to heat injury. Use of high sun protection factor (SPF) sunscreen before deployment and reapplying often can prevent sunburn. Finding shade when available will also reduce UV burden and lessen the individual’s heat stress.

Dehydration

Dehydration occurs when fluid losses exceed intake. Those under high stress and in warm environments lose most of this fluid through sweating but also through insensible means, such as respiration. Heavy gear and hard exertion can lead to fluid losses of 1 L/h. Replacing lost water is necessary in order to maintain an adequate hydration status and avoid heat injury. Any exposed operator is at risk, and command-driven oral hydration should be mandated by the commander and TEMS provider. This is primarily important because unfortunately thirst is not the ideal indicator of hydration status. Headache is a likely first indicator of dehydration and must be addressed as such. Preventive medicine dictates that all team members prehydrate and carry adequate supplies on their person, typically in the form of a backpack bladder. Rehydration with water or 0.5- to 0.25-strength diluted sports drinks will work for minor cases of dehydration, and the dilution will prevent the gastrointestinal (GI) upset sometimes seen with heavy carbohydrate drinks. Although weather conditions and individual variation in sweating may dictate different fluid requirements, a safe recommendation is 1 L/h of work, and the urine color concentration can be used as a rough guide for hydration status.

Infectious Diseases

In the tactical environment the most likely infectious diseases to be encountered are those transmitted by insect vectors. For missions within the United States the greatest risks for mosquito and tick-borne illnesses are West Nile virus and Lyme disease, respectively. However, other tick-borne illnesses, such as babesiosis and rickettsial Rocky Mountain spotted fever, are also important diseases to consider when operating in endemic areas. American trypanosomiasis, also known as Chagas disease, is a protozoal disease caused by transmission from the bite of the “kissing bug” found in the southern United States and Latin America.

Because of the variable incubation periods of vector-borne diseases, acute transmission of these diseases are unlikely to take an operator out of action during a mission. But that does not obviate the TEMS provider of the responsibility of making sure team members undergo proper evaluation for these infections if symptoms develop days or weeks later. All of these diseases can lead to significant impairment, including fevers, encephalitis, myocarditis, neurologic impairment, or sometimes death. The best treatment is prevention. Team members should prepare appropriately with protective clothing, application of high concentration N , N -diethyl-meta-toluamide (DEET) to all exposed skin, and using appropriate pest control with netting and sprays at home base.

Viral infections typically cause self-limited disease; however, more significant infections leading to influenza, measles, hepatitis, and weaponized smallpox could possibly occur. Fortunately vaccination has helped to decrease the risk of infection with hepatitis A, hepatitis B, influenza, measles, poliomyelitis, rabies, smallpox, and mumps when exposed. But, in an era where fringe thinkers are increasingly choosing to ignore science and forgo vaccinating their children, it is imperative that operators stay up to date with immunizations. Adenovirus is very contagious and leads to a spectrum of respiratory illnesses. However, vaccination in some populations and good hygiene in close corridors can prevent the spread of disease. Similarly many viral infections can lead to gastroenteritis, with diarrhea and vomiting, which can ultimately cause dehydration and impair the ability to fight. Good hygiene, including proper toileting away from camp and waste disposal, is a critically important piece of disease prevention.

Bacteria can lead to severe infections and often do not resolve without proper treatment with antibiotics. Since the terrorist attacks in the United States, anthrax has become a true terrorist threat. It is a spore-forming bacterium leading to cutaneous, GI, or inhalational infection. Vaccination in the appropriate population helps to prevent infection when exposed. In addition, caution with human and animal blood and bodily fluids and disinfection of the premises are important aspects in avoiding the spread of disease. ^, Bubonic plague, a zoonotic bacterial infection caused by Yersinia pestis , is transmitted from rodents via a flea vector and is endemic to parts of the southwest United States. The more deadly pulmonary form, called pneumonic plague, is transmitted person to person by droplet inhalation. Vaccination does not protect against pneumonic plague but can help prevent contraction of the bubonic form from fleas. Other preventative measures include pest control, avoidance of dead animals, and protective gear. ^, Tetanus, a neurotoxin-based illness caused by the spore-forming bacterium Clostridium tetani found in soil and animal GI tracts, is introduced through contaminated wounds and infection and leads to acute, lethal central nervous system disease. Cleaning wounds and maintaining current immunizations is an important aspect of prevention of tetanus.

For tactical operational teams, such as military special forces or groups deploying for disaster response internationally, additional region-specific illnesses must be considered which can cause significant morbidity and mortality. Malaria is a potentially lethal protozoal infection endemic to tropical and subtropical areas and is caused by species of the Plasmoidium genus. It is widespread across developing countries, particularly in Africa, and is transmitted by Anopheles mosquito bites. Symptoms vary but typically include fever, chills, myalgias, abdominal pain, and diarrhea. Prophylactic medications, such as mefloquine, Malarone, and doxycycline, can help prevent infection while in these areas and should be mandatory for all operators before travel and after return.

Dengue fever is a viral infection spread via mosquitos in tropical urban centers. Infectious symptoms include fevers, headaches, myalgias, hemorrhage, and sometimes shock or death. Prevention is similar to avoiding other mosquito-borne illnesses but typically involves the avoidance of outdoor activities while mosquitos are active and using protective clothing, nets, and DEET spray. ^,

Yellow fever virus causes a viral hemorrhagic fever and is endemic to tropical jungle environments in Africa and South America. Prevention with immunizations and boosters are important and should be given before travel to any endemic area because the mortality rate for unvaccinated patients is as high as 50%. Another infection, typhoid, is caused by Salmonella typhi and is spread from human to human via fecal contamination and shared food. It causes a febrile illness characterized by abdominal pain and sometimes rash. It is encountered both domestically and abroad, typically when exposed to contaminated drinking water in developing countries. Vaccination is available. Otherwise, preventive measures include properly cooking and washing food, drinking appropriate water, and practicing good fecal hygiene.

Parasitic infections are typically contracted through contact with or ingestion of contaminated water. The most common infections include amebiasis, ascariasis, giardiasis, and schistosomiasis, all of which can lead to significant diarrhea, abdominal pain, and in some cases liver failure or death. Prevention with filtering water, boiling water, good hand washing and hygiene, avoidance of fresh water, and safe food preparation is vital. Domestic tactical operations are typically short in duration, close to urban centers, and well within reach of clean water and sanitation. In other operational environments, such as disaster deployment and military missions, these illnesses may be encountered and should be part of the MTA.

Tropical environments lend themselves to more exotic animals and exposure risks. Within the United States the vast majority of poisonous snakebites are caused by pit vipers, such as rattlesnakes, copperheads, and cottonmouth snakes. However, most deaths within the United States are caused by diamondback rattlesnakes. There is a correlation between envenomation dose and rapidity of onset of illness. Symptoms can range from mild swelling of the extremity with localized pain, to diarrhea, confusion, and severe cardiovascular collapse and shock. Prevention includes appropriate leather boots and situational awareness. In the case of envenomation the TEMS provider should arrange medical evacuation to the nearest hospital for supportive care and antivenin, as needed. Venomous spiders, which in the United States are primarily the infamous black widow spider and the brown recluse (“fiddleback”) spider, which are the only two endemic species capable of human envenomation, are rarely life or limb threatening. The black widow produces a painful bite and injects a neurotoxin. The brown recluse bite is typically painless, and the necrotoxin injected can cause variable degrees of tissue loss from small ulcers to loss of fingers or toes.

Preventive medicine is a key concept to be understood by all practitioners in the tactical medicine realm. Similar to military and flight medicine, TEMS providers are the medical conscious of the team and for the commander. As such, it is the responsibility of the team’s medical expert not only to respond to injured officers, suspects, and civilians but also to engage the team in the important concepts of preventive medicine. In doing so the provider helps to ensure that the operators are in peak fighting condition and are able to participate safely in the mission at hand. Ensuring that each member is screened appropriately before acceptance to the team and before each relevant mission maximizes the probability of mission success and safe return of each participant.