Environmental Disorders 7.22.docx

Today we will be discussing various environmental disorders that can impact health. Heat illness: The first environmental disorder we will discuss which is common in Texas is heat illness. There are two forms of heat stroke, classic and exertional. Classic heat illness typically affects elderly indi...

Today we will be discussing various environmental disorders that can impact health. Heat illness: The first environmental disorder we will discuss which is common in Texas is heat illness. There are two forms of heat stroke, classic and exertional. Classic heat illness typically affects elderly individuals with chronic medical conditions. It can also include the very young, people on certain medications or drugs, people who lack air conditioning, and people enclosed within an automobile. Exertional heat illness affects otherwise healthy people who engage in strenuous exercise in hot or humid weather. This would include your athletes, military, or can include construction workers. Heat illness signs, symptoms & treatment: The signs and symptoms of heat illness may include cramping, fatigue, dizziness, nausea, vomiting, headache, syncope, and edema. We do not use diuretics to correct the edema. The edema is transient and will improve once the person is removed from the heat. Removing the person from the heat is also the treatment for cramping. For syncope, having the patient lie in a cool place should improve the symptom. To treat the fatigue or exhaustion, nausea, vomiting, dizziness, and headache removing the person from the heat and giving them PO hydration with fluids and electrolytes with sugar will resolve the symptoms. Heat Injury and stroke: If progression to end-organ damage occurs it then becomes heat injury. Any neurologic alteration distinguishes heat stroke from heat injury. Patients who present with heat stroke typically have vital sign abnormalities to include an elevated core body temperature, sinus tachycardia, tachypnea, a widened pulse pressure, and a quarter of patients will be hypotensive. On physical exam, classic heat stroke patients often present with hot, dry skin because of a failure of the normal sweating response, also known as anhidrosis. With exertional heat stroke, anhidrosis is an uncommon finding. Instead, you will see prolonged sweating occurs following the cessation of exercise. With the heavy exertion you will find these patients to have rhabdomyolysis which leads to acute tubular necrosis. Management of heat stroke includes ensuring adequate airway protection, breathing, and circulation.  After ABC’s, rapid cooling becomes the mainstay of treatment with response to other end-organ damage. The patient will rarely need to be intubated if they are unconscious as rapid cooling quickly improves the Glasgow coma scale. Adequate rehydration is essential without over-correcting the sodium if derangements exist. It is mandatory to measure core temperature with a rectal or esophageal probe continually and cooling measures should be stopped once the temperature is 38 to 39 degrees Celsius. There are no definitive studies support any cooling method over another. Ice bath immersion is the timeliest to reduce core body temperature, however, in older populations, it may not be realistic as cardiac monitoring may not be feasible and extreme agitation may hinder compliance. Other common methods include ice pack applications to the groin or axilla and evaporative cooling using a fan with cool saline on the skin of patients. There is no role for antipyretics in the treatment of heatstroke patients and may be toxic to the liver. Hypothermia: Now we will move to the other end of the spectrum and discuss hypothermia. This is when the core temperature is less than 35 degrees Celsius.  The underlying cause of accidental hypothermia is excessive cold stress and inadequate heat generation from the body or thermogenesis. Other factors increase the risk of developing hypothermia which include elderly, burns, trauma, sepsis, and hypoglycemia. Common signs of hypothermia include altered mental status and bradycardia. With the bradycardia, patients will have an idioventricular or junctional escape beat with prominent J waves in the anterior leads also known as Osbourne waves. Here in the ekg the arrows show these Osborne waves. Hypothermia treatment: The management and treatment of accidental hypothermia revolve around the prevention of further heat loss and the initiation of rewarming. However, the initial steps are always to evaluate and support airway, breathing, and circulation. Wet clothing should be removed and replaced with dry clothing or insulation as soon as possible to prevent further heat loss. Rewarming of hypothermic patients involves passive external rewarming, active external rewarming, active internal rewarming, or a combination of these techniques. The treatment of choice for mild hypothermia is passive external rewarming. After the removal of wet clothing, additional layers of insulation are placed on the patient with the goal to prevent heat loss and promote retention of heat produced by patients. Shivering allows the body to produce heat. However, the success of this method requires adequate glucose stores so that a patient can produce heat. It is appropriate to supply glucose to these individuals orally when possible. In individuals with mild hypothermia, it is recommended to warm them at 0.5 to 2 C per hour. Vigorous shivering, however, can be problematic in people with limited cardiopulmonary reserve as it requires an increase in the consumption of oxygen. Patients with more severe hypothermia may fail to respond to passive techniques, so it is appropriate to progress to active external rewarming techniques. Despite active external rewarming, some patients may require more invasive methods ranging from airway rewarming with humidified air to full cardiopulmonary bypass. Most patients will be started on warm intravenous fluids of 40 to 42 C as they are readily available and safe, as well as humidified air. Lavage of body cavities such as stomach, bladder, colon, peritoneal and pleura with warm fluid, though invasive, can be considered. Pleural and peritoneal lavages are preferable due to the larger mucosal surface area. Extracorporeal methods, including hemodialysis, continuous arteriovenous rewarming, cardiopulmonary bypass, and extracorporeal membrane oxygenation (ECMO). Hemodialysis is the most accessible and can raise the core temperature 2 to 3 C per hour. Cardiopulmonary bypass surgery and venoarterial ECMO is the most effective but highly invasive method of rewarming a patient. These methods are only for hypothermic patients in cardiac arrest, those patients refractory to other rewarming techniques, and hemodynamically unstable patients.  Frostbite: Frostbite is tissue damage that occurs due to cold exposure, occurring at temperatures below zero degrees Celsius. Homeless populations, children, and the elderly are especially vulnerable to frostbite. Prolonged duration and lower temperatures increase the risk of frostbite and the extent of the injury. Certain pre-existing conditions, including peripheral vascular disease, malnutrition, Raynaud's disease, diabetes mellitus, and tobacco use may worsen frostbite-related tissue damage.  Physical examination may reveal blanched, white skin. Patients may complain of heaviness in an exposed extremity as numbness progresses. In later stages of frostbite, exposed areas may become dark or purplish in hue due to poor vascular tone and pooling of blood. Superficial or first degree frostbite affecting the epidermis and subcutaneous fat will have pale, white blisters upon rewarming. 2nd degree will have clear blisters. 3rd degree you will see hemorrhagic blisters, as this is deeper. 4th degree is to the bone. With deep, full-thickness frostbite this can become hemorrhagic with rewarming and may become gangrenous. It is important to know that the initial exam will not accurately reveal the final depth and extent of the injury. Patient with frostbite are at risk for rewarming injury. During rewarming, edema may start to appear within 3-5 hours and may last 7 days. Blisters tend to appear within 4-24 hours. Presence of eschar will be obvious at 10-15 days and mummification with a line of demarcation may develop in 3-8 weeks. Patients should have protection from further injury by covering exposed areas. The care of patients with frostbite begins with rewarming. Remove patients from the wind. Remove wet clothing and replace with dry clothing. Avoid vigorous rubbing as this can cause further damage. In-hospital management includes warm water baths, approximately 40-42 degrees C. Patients with systemic hypothermia should be managed by raising core temperature above 35 degrees C using warm IV fluids, and this should precede warming of the affected extremity. NSAIDS like ibuprofen are indicated for controlling pain and preventing further inflammation, but stronger analgesics including narcotics may be necessary to achieve pain control. Frequent re-examination for sensation should accompany rewarming. Complete rewarming should be achieved before surgical debridement. Signs of compartment syndrome include edema, pulselessness, and extreme pain. This should prompt urgent surgery. Patients with full-thickness injuries and evidence of ischemia and no restoration of tissue perfusion after rewarming may be candidates for thrombolytic therapy. tPA may reduce the need for digital amputation. Combination therapy with tPA and IV heparin may also reduce the need for digital amputation. Burns: Now we will discuss burns. Burns are injuries of the skin involving the two layers: the thin, outer epidermis and the thicker, deeper dermis. 86% of burns are caused by thermal injury, while about 4% are electrical and 3% are chemical. Burns may be caused by abuse, chemicals such as strong acids, paint thinner or gasoline, electrical currents, fire, hot liquid, hot metal, glass or other objects, steam, radiation from x-rays, and sunlight or ultraviolet light. A variety of factors guides the evaluation and management of burns. First is the type of burn such as thermal, chemical, electrical or radiation. Second is the extent of the burn usually expressed as the percentage of total body surface area involved. Next is the depth of the burn described as superficial, partial or full thickness. Finally, other factors include specific patient characteristics like the age of the patient, other medical or health problems, if there are specialized locations of the burn like the face, eyes, ears, nose, hands, feet and perineum, and if there are any associated injuries, like smoke inhalation and other traumatic injuries. For extent there is the Rule of Nines which the head represents 9%, each arm is 9%, the anterior chest and abdomen are 18%, the posterior chest and back are 18%, each leg is 18%, and the perineum is 1%. There is also the Lund and Browder Chart. This is a more accurate method, where each arm is 10%, anterior trunk and posterior trunk are each 13% and the percentage calculated for the head and legs varies based on the patient’s age. For the Burn depth is classified into one of three types based on how deeply into the epidermis or dermis the injury might extend. Superficial burns or First Degree involve only the epidermis and are warm, painful, red, soft and blanch when touched. Usually, there is no blistering. A typical example is a sunburn. Partial thickness burns or Second Degree extend through the epidermis and into the dermis. The depth into the dermis can vary superficial or deep dermis. These burns are typically very painful, red, blistered, moist, soft and blanch when touched. Examples include burns from hot surfaces, hot liquids or flame. Full-thickness burns or Third Degree extend through both the epidermis and dermis and into the subcutaneous fat or deeper. These burns have little or no pain, can be white, brown, or charred and feel firm and leathery to palpation with no blanching. These occur from a flame, hot liquids, or superheated gasses.  The American Burn Association recommends burn center referrals for patients with partial thickness burns greater than 10% total body surface area, full thickness burns, burns of the face, hands, feet, genitalia, or major joints, chemical burns, electrical, or lighting strike injuries, significant inhalation injuries, burns in patients with multiple medical disorders, and burns in patients with associated traumatic injuries. In Dallas, Parkland is the hospital that offers a burn center. Minor burns which you plan to treat can be approached using the “C” of burn care in include cooling small areas of burn with tap water or saline solution to prevent progression of burning and to reduce pain. Cleaning can be done by using mild soap and water or mild antibacterial wash. Large blisters are debrided while small blisters and blisters involving the palms or soles are left intact. Cover burns with topical antibiotic ointments or cream with absorbent dressing or specialized burn dressing materials are commonly used. Provide comfort with over-the-counter pain medications or prescription pain medications when needed. The patient will also need an updated Tetanus vaccine. For burns classified as severe or > 20% total body surface area, fluid resuscitation should be initiated to maintain urine output > 0.5 mL/kg/hour.  One commonly used fluid resuscitation formula is the Parkland formula. The total amount of fluid to be given during the initial 24 hours equals 4 ml of LR × patient’s weight in kilograms multipled by the percentage of total body surface area.  Half of the calculated amount is administered during the first eight hours beginning when the patient was initially burned. For example, if a 70 kg patient has a 30% TBSA partial thickness burn they will need 8400 mL Lactated Ringer solution in the first 24 hours with 4200 mL of that total in the first 8 hours. The fluid resuscitation formula for burns is only an estimate and the patient may need more or less fluid based on vital signs, urine output, other injuries or other medical conditions. In patients with moderate to severe flame burns and with suspicion for inhalation injury, carboxyhemoglobin levels should be checked, and patients should be placed on high flow oxygen until carbon monoxide poisoning is ruled out.  If carbon monoxide poisoning is confirmed, continue treatment with high-flow oxygen and consider hyperbaric oxygen in select cases. Cyanide poisoning can also occur from smoke inhalation and can be treated with hydroxocobalamin. Electrical injuries: Electrical injuries are when high-energy current travels through the body due to contact with an electrical source. Injuries occur due to either the flow of current through the body, arc flash, or clothing that catches fire. With the former two, the body converts electricity to heat, which results in a thermal burn. It is important to consider that the outward appearance of an electrical burn does not accurately predict the true extent of the injury, as internal tissues or organs may be much more severely burned than the skin. Common causes of electrical injuries include utility worker who falls from a bucket truck and instinctively grab a power line to catch himself or a worker may be holding a pole that comes in contact with a power line.  More commonly, a person becomes a victim of electrical injury at home, such as when an electrical cord on an appliance becomes exposed and makes contact with the human body or when an electric source contacts water that an individual is in contact with as well, such as a hair dryer falling into a bathtub. A thorough history should be obtained, including the source of patients electrical injury, the voltage and current type of the energy source, the duration of electrical exposure, and how the injury was incurred. It is also important to obtain the patient's cardiac history, including any history of prior arrhythmias. Low-frequency alternating current or AC causes more extensive injury to tissues than does high-frequency AC or direct current or DC. This is because low-frequency AC causes ongoing local muscle contraction (flexor muscles greater than extensor muscles) at the site of contact with the electrical source, often rendering the victim unable to let go of the offending object. In addition, AC injuries are much more common, as AC powers households and other buildings. DC causes a single strong muscle contraction, often throwing its victim away from the energy source. The most common examples of DC injuries include lightning strike and contact with a car battery. Of note, the risk of death and/or severity of injury from lightning strike depends on many factors, such as if the exposure was a direct lightning strike or the lightning hit something else nearby like a tree and then traveled to the individual’s body. Burns can be classified as high or low voltage.  High voltages greater than 500-1000 Volts cause deep burns and extensive deep tissue and organ damage. Low voltage exposures tend to result in lesser injury.  Electricity follows the path of least resistance with most injuries occur to tissues with the least amount of resistance. Skin is the tissue with the most amount of resistance in the human body, followed by bone. Nerves, muscle, and blood have the least amount of resistance. Moist tissues like muscle have much lower resistance than dry tissues like skin. Higher skin resistance results in more diffuse burns to the skin. Lower skin resistance results in deeper burns that are more likely to involve internal organs. Electricity passes through the highly-resistant skin tissue and then spreads out through the underlying tissues with less resistance. Therefore, skin burns can appear mild when internal tissues and organs are severely damaged. EKG, cardiac enzymes, CBC, CK, and urinalysis to check for myoglobin due to rhabdomyolysis should be obtained.  Any patient that was in contact with a high voltage source should have continuous cardiac monitoring during evaluation.  Fluids should be titrated to produce adequate urine output. Pain control is also a priority for these patients. Altitude sickness: Now we will discuss altitude sickness. This is caused by a relative hypoxia due to the increased atmospheric pressure that occurs with increasing elevation. This can occur in anyone, and being physically fit in not a protective measure. This usually occurs at elevations greater than 8000 feet, and can start as early as day 1. Patients may have headache, nausea, fatigue, and insomnia. These symptoms can be worsened with sedatives and alcohol. This is usually treated with NSAIDS, steroids, oxygen, and descent. HACE/ HAPE: More serious concerns with higher elevation include high altitude cerebral edema or HACE, and high altitude pulmonary edema or HAPE. High Altitude Pulmonary Edema and High Altitude Cerebral Edema are both life-threatening emergencies requiring immediate treatment, with a descent to lower altitude or higher pressure artificial environment quickly. HACE generally occurs after 2 days above 4000m but can occur at lower elevations around 2500m and with faster onset.   HACE is a clinical diagnosis with the patient typically presenting with signs of increased intracranial pressure or encephalopathy, preceeded by signs and symptoms of Acute Mountain Sickness. The onset of neurological findings such as progressive decline in cognitive or mental function, declining level of consciousness, impaired coordination, and slurred speech signify the transition from AMS to HACE.  Typical evaluation consists of an abnormal neurological exam, with ataxia often being the earliest finding. Early symptoms may be misinterpreted as exhaustion and it is important to exclude these, as well as other disorders such as dehydration, hypoglycemia, hypothermia, or hyponatremia which all may have signs and symptoms that overlap with that of HACE. The mainstay of treatment is the immediate descent of at least 1000 meters or until symptoms improve. One should not descend alone and should have assistance to minimize physical exertion, which may worsen the patient’s condition. If descent is not an option, one may use a portable hyperbaric chamber and/or supplemental oxygen to temporize illness, but this should never replace or delay evaluation/descent when possible. Dexamethasone 8mg for one dose, followed by 4mg every 6 hours should be given to adults either PO, IM, or IV routes. Diamox can be beneficial at 250 mg PO twice daily.  The severity of HAPE will depend on multiple factors including altitude, initial recognition and management, and access to medical care. HAPE typically occurs 2 to 5 days after arrival at altitude. It has an insidious onset with a non-productive cough, decreased exercise tolerance, chest pain, and exertional dyspnea. Without treatment, it can progress to dyspnea at rest and severe exertional dyspnea. A cough may become productive of pink and frothy sputum or frank blood. The patient also may have rales or wheezes, central cyanosis, tachypnea, and/or tachycardia. HAPE's clinical diagnosis would include at least two of the following symptoms or complaints to include chest tightness or pain, cough, dyspnea at rest, and decreased exercise tolerance. It also would have two of the following exam findings to include central cyanosis, rales/wheezes, tachycardia, and tachypnea.  If available, CXR may show patchy alveolar infiltrates with normal-sized mediastinum/heart, The mainstay of treatment is to descend 1000 meters or until there is a resolution of symptoms with the descent. During the descent, it is important to minimize exertion as exertion may increase hypoxemia from metabolic demands of the body and worsen an individual’s condition. If available, a trial of oxygen therapy may ameliorate symptoms and help temporize the patient if the descent is technically difficult or delayed. That said, the mainstay of treatment remains descent, regardless of oxygen availability. Diving: From the mountains, and now to the beach. Pulmonary barotrauma related to SCUBA diving is due to lung overexpansion when a diver returns to the surface without exhaling or when the air becomes trapped in the lung. During any dive, a diver is subject to the limitations imposed by Boyle's Law, which states that pressure and volume are inversely related. As the diver swims deeper or increased pressure, their lungs will have decreased volume. As pressure decreases or swimming back to the surface, the volume will increase proportionally, which means that the same diver holding his breath and ascending would double his lung volume on return to the surface if that were anatomically possible without structural damage to the lungs. A diver who holds his or her breath and ascends from as little as 3 feet may cause an over-pressurization sufficient to rupture lung alveoli and introduce gas into the surrounding tissues and/or blood vessels. This is referred to as pulmonary overinflation syndrome or also called pulmonary barotrauma. Increased risk factors include acute exacerbation of reactive airway disease, anatomic anomalies such as bullae or blebs, or holding the breath can entrap air in the lungs of a diver.  Physical signs and symptoms of pulmonary barotrauma symptoms include cough, shortness of breath, hemoptysis, chest pain, dyspnea, choking, change in voice, hoarseness, difficulty swallowing, cyanosis, respiratory failure, loss of consciousness, cardiac arrest, and death. Pneumomediastinum can be symptomless, or patients can experience chest discomfort, substernal chest pain, cough, shortness of breath, change in voice, hoarseness, and difficulty swallowing.  This overinflation or barotrauma can result in one or more overexpansion injuries including pneumomediastinum, pneumothorax, subcutaneous emphysema, or arterial gas embolism.  Air-gas emboli can reach the coronary arteries and present as an acute myocardial infarction with chest pain, chest pressure, pain radiating to the neck, shoulders, back, or jaw. Shock and cardiac arrest can ensue. Treatment includes stabilizing the diver with basic and advanced cardiac life support. Intravenous access should be obtained along with the application of supplemental oxygen. Administration of crystalloid intravenous fluid for hydration is recommended. Perform intubation in patients who have an unstable airway or have persistent hypoxia despite breathing 100% oxygen. No specific treatment is required for mild cases of pneumomediastinum as air will reabsorb on its own. Supplemental oxygen can be initiated for persons experiencing hypoxia. Higher concentrations of oxygen increase the reabsorption rate of the air. Pneumothorax may resolve without treatment or require chest tube thoracostomy. Tension pneumothorax mandates chest tube thoracostomy to drain air and reduce pressure to allow blood flow and circulatory function. Treatment for arterial gas embolism related to pulmonary barotrauma should ideally be completed within the first two hours. This provides the most benefit and best chance of complete resolution of symptoms. Any delays in recompression and hyperbaric oxygen therapy of more than six hours are associated with worse outcomes. Recompression therapy should be done at a dive chamber by medical personnel certified in hyperbaric medicine. Indications for recompression therapy include spinal cord injury and neurologic impairment. Drowning: Now we will discuss near-drowning. Drowning can be accidental or deliberate exposure to submersion in water or other liquid substances that inhibit the body's ability to oxygenate tissues and organs. Risk factors for drowning include head trauma, seizure, cardiac arrhythmia, hypoglycemia, hypothermia, alcohol and drug use, suicide, myocardial infarction, panic attack, depression, poor judgement, natural disaster, and scuba diving. All drownings are managed and treated essentially the same. The main difference is between the patient drowning in salt water versus fresh water. Swallowing plenty of freshwater leads to quick absorption into blood from the gastrointestinal tract due to a lower osmotic pressure than blood; therefore, it increases blood volume in a short amount of time that results in hemolysis. Unlike freshwater, saltwater does not induce the above complications because of having the equal osmotic pressure to blood, and it can increase sodium and chlorine causing symptoms. For this reason, swimmers are advised that if they swallow a lot of water, they try to self induce vomiting, and even if they are in a good condition, they should go to the hospital to evaluate electrolytes, as the symptoms may develop within the next few hours. Public perception regarding drowning includes the misconception that large quantities of water are aspirated, preventing ventilation and oxygenation. However, retrospective autopsy reveal that only a small percentage of fatal drownings are found to have large quantities of intra-alveolar fluid. The insult is primarily due to the development of a the physiologic response when faced with drowning and that is an involuntary laryngospasm. This prevents the exchange of gasses necessary for ventilation and oxygenation. As hypoxia and hypercarbia worsen, the ultimate outcome is cardiac arrest. Drowning in seawater with subsequent aspiration, results in pulmonary edema due to the large increase in osmolar gradients. Conversely, aspiration of fresh water has shown to cause a dilution effect of surfactant in the alveoli, with subsequent decrease in surface tension and collapse of the alveoli. This decrease in surfactant is the cause for alveolar collapse and development of ARDS. The greatest morbidity and mortality associated with non-fatal drowning is due to tissue hypoxia, specifically cerebral hypoxia, and thus, the greatest priority in the resuscitation process is to address and correct hypoxia quickly. Regardless of water source, the disruption of the oxygen gradient and the resulting pulmonary shunting results in the hypoxemia, hypercarbia, and acidosis. There are several methods that can be utilized to help improve the hypoxemia associated with severe ARDS secondary to drowning. Both prone positioning and extracorporeal membrane oxygenation or ECMO have been demonstrated to improve oxygenation and decreased mortality. Despite the alterations in the alveolar interface that are dependent on the tonicity of the fluid, the ultimate treatment of near-drowning injuries remains consistent regardless of the tonicity of the water. Aggressive therapy, tailored to the individual patient, can improve pulmonary shunting. Patients with hypoxemia requiring intubation should be ventilated with positive end-expiratory pressure (PEEP). Mammal bites: The initial injury is the result of the physical trauma of teeth puncturing and/or tearing soft tissue. The physical trauma from a human bite is relatively minor with lacerations and occlusion bruising being the main initial findings.  Human oral flora and contagious disease though spread to account for the greater amount of morbidity with human bites. Eikenella corrodens, as well as more common aerobic and anaerobic bacteria, are normal human flora.  Herpes, hepatitis, and human immunodeficiency viruses are all transmissible through bite injuries.  Closed-fist injuries show a predication for infection due to the injury overlying the joint capsule of the MCP and the extensor tendon sheath.  In the case of dog bites, these can cause crush injuries. Dog bites are more commonly macerated due to the ripping and tearing forces involved. Cat bites are narrow and deep as the animal rarely pulls or shakes its head, simply biting and holding. Because the cat bite wound is deep and narrow, it is much more likely to seal itself relatively quickly, providing an anaerobic environment for the inoculated bacteria as well as initially appearing less consequential and prolonging time to seeking medical care.   All wounds or bites require extensive irrigation, and the patient’s tetanus status updated if necessary. Provide appropriate pain management before exploration, irrigation, or debridement of the wounds. The patient’s TDaP status should be updated if necessary. For uncomplicated dog bites, the patient should be educated on the risk/benefit of closure versus healing by secondary intention and the decision made with the provider. If the patient presents delayed from the initial bite, the risks of closing the wound almost certainly outweigh the cosmetic benefits of closure. If the wound is closed, the patient should be discharged with a week’s course of amoxicillin-clavulanate. Complicated dog bites should be stabilized and referred for the appropriate consultation service. Cat bites deeper than superficial need thorough irrigation under local anesthesia and the wound left open. The patient should be discharged with a week’s course of amoxicillin-clavulanate and given strict wound care precautions. All bites to the hands or feet, bites in immunocompromised individuals, bites that already show signs of infection, and bites with a puncture characteristic require treatment with amoxicillin-clavulanate. For patients with penicillin allergies, second-line therapy is doxycycline or Bactrim plus metronidazole or clindamycin. Arachnid bites: Arachnids are the class of arthropods that include ticks, mites, scorpions, and spiders.   Tick bites are usually painless and can present with a wide variety of rashes and other dermatologic findings, making diagnosis challenging. Bites often appear as an erythematous papule with surrounding erythema. Tick-borne infectious diseases such as Lyme disease and Rocky Mountain spotted fever present with characteristic rashes. The most significant impact of ticks on humans is their ability to serve as vectors for significant diseases including Rocky Mountain spotted fever, endemic typhus, ehrlichiosis, Q-fever, encephalitis, hemorrhagic fever, Lyme disease, relapsing fever, and tularemia.. Simple, uncomplicated tick bites are treated with routine wound care, topical corticosteroids and systemic antihistamines for pruritic lesions and antibiotics if secondary infection is present. Ticks should be removed with fine-tipped tweezers, grasping the tick as close to the skin as possible and pulling upward with steady, gentle pressure. Scorpions Scorpions have a tail-like structure containing a stinger and two venom glands. In the United States, only the bark scorpion possesses venom with the potential to cause systemic toxicity. Most stings produce only localized pain, and a diagnostic clue is increased sensitivity to touch or tapping on the area. While systemic symptoms are uncommon, the venom from the bark scorpion can cause several adverse autonomic and motor effects such as hypertension, tachycardia, tachydysrhythmias, and myoclonus. The diagnosis of scorpion envenomation generally relies on a history of a scorpion sting, presence in a scorpion endemic region and characteristic findings. In patients with moderate to severe symptoms, serum electrolytes, liver enzymes, creatine kinase, and urinalysis should are necessary. Additional studies such as a serum lipase, complete blood count, coagulation studies and an EKG may be required depending on patient presentation. Most stings can be managed with supportive care including removing the stinger if present, cleaning the site with soap and water, ice application to the area and acetaminophen for pain. Agitation, muscle spasms and myoclonus should be managed with benzodiazepines while tachyarrhythmias and hypertension treatment is with intravenous beta-blockers. An FDA approved antivenom is available but is only for cases of severe systemic toxicity. In North America, the two spiders that have the greatest potential to cause significant morbidity are the Black Widow and Brown Recluse. Brown Recluse spiders are predominantly found in the south and the central United States and reside in dark, dry places such as woodpiles, sheds, closets, and garages. Bites typically occur on the extremities when the spider’s dwelling is disturbed, or it feels threatened. Bites may be perceived as a sharp, stinging sensation but are often painless and cause only minor, inconsequential reactions, usually presenting as small erythematous lesions. Some bites will develop an area of cyanosis or pallor, sometimes with the appearance of hemorrhagic blisters, due to tissue ischemia.  The most common complication in serious envenomations is full-thickness skin necrosis which may require significant debridement and skin grafting. Treatment of brown recluse envenomation depends on the clinical presentation. In uncomplicated bites, treatment consists of routine wound care, evaluation of tetanus status, and the local application of ice which may decrease the activity of damaging enzymes found in the venom. In cases of necrotic ulceration, early excision is not a recommendation as it can result in recurrent wound breakdown, delayed healing, scarring, and long-term distal extremity dysfunction. Black Widows are spiders reside throughout the United States and prefer to spin their webs in dark, close quarters such as woodpiles, basements, crawl spaces, attics, and stored boxes. Most bites are defensive, occurring when the female spider perceives a threat to herself or her eggs, or when the spider is unintentionally disturbed. While the black widow has potentially dangerous venom, many bites result in only minimal symptoms and produce no severe damage. Perception of the bite is usually as a sharp pinprick-like sensation which may develop into a dull ache or numbness at the site. Serious reactions may manifest as severe muscle spasms and pain in the chest, abdomen and lower back. Other clinical manifestations may include hypertension, sweating, salivation, restlessness, fasciculation, ptosis, nausea, vomiting, and dyspnea. Severe symptoms usually occur within 1 to 6 hours and last anywhere from 12 to 48 hours. The venom of the black widow spider is most notable for a potent neurotoxin, which unlike the brown recluse, does not cause local necrosis. Management for those without systemic symptoms is with supportive care including washing the bite site, application of an ice pack to the area, updating tetanus immunization, and treatment of pain with acetaminophen. Muscle spasms, cramping, and pain are usually manageable with benzodiazepines and opiates. An antivenom is available but reserved for those with significant systemic involvement. Rattle Snake bites: Rattlesnakes are found throughout the Americas. They exist in almost every state of the U.S., except Alaska and Hawaii. The morbidity and mortality associated with snake bites are usually due to the envenomation or the amount of venom in the bite. Snakebite wounds usually do not become infected. Humans are often bitten when inadvertently stepping on snakes or by moving too close to them while they are in hiding. Most deaths related to snake bites are due to immediate anaphylactic reactions or failure to seek medical attention for anti-venom administration. Rattlesnake bite victims may present with a variety of local and systemic symptoms. Fang marks are usually identifiable at the patient’s bite site. Local symptoms include localized pain, swelling, and bleeding from the bite site. In more severe cases, local tissue necrosis and ecchymosis can occur. Systemic symptoms include angioedema, bleeding from other orifices including hematemesis and hematochezia, nausea, vomiting, diarrhea, dyspnea, and anaphylaxis. Bloodwork should be performed for all snake bites and should include CBC, Serum Chemistry, Coagulation Panel, Fibrinogen, and Creatine Kinase. A urinalysis can be helpful to evaluate for myoglobinuria, which can help assess for rhabdomyolysis. Upon initial evaluation, the leading edge of the swelling and redness surrounding the bite site should be marked. Limbs should be evaluated for neurovascular status. Frequent reassessments for progressive swelling should be performed.  Do not use tourniquets, or I&D or attempt to remove venom. Immobilize the extremity to reduce the potential dissemination of venom through the lymphatic system. Patients presenting with a snake bite should be stabilized by initially assessing their airway, breathing, and circulation just like any other trauma situation.  Tetanus should be updated if necessary, and the local poison center should be notified. Signs of envenomation may vary between presentations but should be assessed in all snakebite victims. Systemic signs include hypotension, bleeding, or oozing from IV sites, vomiting, diarrhea, angioedema, and neurotoxicity. Assessment for facial edema including tongue swelling and respiratory distress should be recognized, and a definitive airway should promptly be obtained if there are concerns for airway compromise. A patient with minimal signs of envenomation should be monitored for at least eight hours and have a repeat coagulation panel performed to evaluate for delayed coagulopathy before discharge. Patients with progressive swelling, moderate envenomation, or coagulopathy should be given antivenom. Rabies: Finally we will discuss rabies. Domesticated animals have only been responsible for about 10% of cases of rabies transmission, while wild animals such as skunks, raccoons, foxes, and especially bats are responsible for the rest of the cases. Any mammal may carry rabies, so it is a priority to be mindful with any mammal bite. Rabies causes viral encephalitis so common symptoms include agitation, changes in mentation, autonomic dysfunction, increased deep tendon reflexes, nuchal rigidity, and finding positive Babinski sign. Other examination findings outside the nervous system can include tachycardia, tachypnea, and fever.   This progresses rapidly to hyperactivity. There is no effective treatment for rabies. Prevention is the mainstay of treatment including programs involving domestic animal vaccination, education, and monitoring. Treatment includes wound care, and in the United States, when a bite is known to be from a bat, skunk, raccoon, or fox, it is treated immediately with a rabies vaccine and rabies immune globulin. For patients with previous immunization, a typical treatment may be with a human diploid cell vaccine or purified chick embryo cell vaccine injected intramuscularly on the day it occurs which is day 0 and again on day 3. If the patient has not been previously immunized, the treatment still involves dosing with one of the two vaccines given intramuscularly on days 0, 3, 7, and 14, and on day 28 if the individual is immunosuppressed. The dose of the vaccine should be given at a site distant from where the human rabies immune globulin was given. These unimmunized patients are treated with human rabies immune globulin as well, with a preference to infiltrate as much of that dose around the wound as possible. Question: Now we can practice some questions. A woman arrives in your ED with a human bite to her breast that occurred earlier in the day. There is a small puncture wound and no signs of cellulitis. A Identify the species, clean and immobilize the site, and administer antivenin. B Clean the bite site and treat with prophylactic antibiotics. C Clean the site, observe the animal, and watch for signs of secondary infection. D Clean the site and begin rabies prophylaxis with active and passive immunization. E Admit for radical surgical debridement in the operating room. Answer: The correct answer is B. Human bites have high rates of infectivity. This wound does not appear to be infected. Nonetheless, the wound should be cleaned and a 3- to 5-day course of prophylactic antibiotics should be initiated. Human bites rarely lead to retained teeth, so a radiograph is not indicated. If this bite occurred on the hand or across a joint space, a radiograph should be performed. Tetanus toxoid should be given if indicated. Question: A scoutmaster brings a boy scout to the ED with a snakebite to his left foot. He says he heard the snake’s rattle just before it bit him. His entire foot is purple, swollen to his mid-calf with a slight ooze noted, and very painful to the touch. A Identify the species, clean and immobilize the site, and administer antivenin. B Clean the bite site and treat with prophylactic antibiotics. C Clean the site, observe the animal, and watch for signs of secondary infection. D Clean the site and begin rabies prophylaxis with active and passive immunization. E Admit for radical surgical debridement in the operating room. Answer: The correct answer is A. This is a high-risk snakebite. Although some percent of venomous snakebites fail to inject venom, this bite is clearly envenomed. The rapid swelling, pain, and discoloration demands immediate attention. First responders should immobilize the site. The swelling is not a compartment syndrome unless elevated pressures are measured. Avoid incisions and fasciotomies or packing in ice. Immediate antivenin injection in and around the site should be a priority. Best results are obtained within 4 hours. Mark the swelling every 15 minutes, evaluate coagulation profiles, electrocardiogram, renal function, and liver function, and consider ICU admission to ensure adequate perfusion and to avoid disseminated intravascular coagulation or DIC. Question: A 24-year-old patient is brought to the ED after drowning in a local lake. Upon arrival to the ED, he has a heart rate of 98 beats per minute, blood pressure of 90/56 mm Hg, respiratory rate of 34 breaths per minute, and oxygen saturation of 84%. He opens his eyes to pain, responds to questions with grunts, and withdraws from pain. Auscultation of the chest reveals diffuse rales. What is the next best step in management? A Aggressive deep suctioning B Endotracheal intubation C IV fluid bolus D Noninvasive positive pressure ventilation Answer: The correct answer is B. This patient has findings of severe respiratory distress with tachypnea as well as a marked hypoxia. Additionally, the mental status is depressed. This patient would be best served by endotracheal intubation for ventilation and also airway protection. Question: A 70-year-old man is brought into the ED complaining of headache and fatigue. His blood pressure is 100/70 mm Hg, heart rate is 100 beats per minute, and core temperature is 40.3°C (104.5°F). Upon using ice bags, his core temperature is down to 38°C (100.4°F). Which of the following is the best next step? A Observation for 4-6 hours and then, if stable, discharge home B Continue ice bags until the core temperature is 36.7°C (98°F) C Admission to the hospital for observation of complications D Administer cold gastric lavage E Discharge the patient only if he can be placed in a different environment after discharge Answer: The correct answer is C. All patients with severe heat exhaustion or heat stroke, particularly those who are older, should be admitted to the hospital. Question: A 33-year-old man is found comatose at a construction site in the noon-hour on a hot summer day. His core temperature is 41.7°C (107.1°F). The ED physician orders evaporative cooling measures and ice packs. The patient begins to exhibit intense shivering. Which of the following is the best next step? A Continued observation B Short-acting benzodiazepine C Begin intravenous cooling solution D Increase the number of ice bags E Stop the cooling Answer: The correct answer is B. This patient most likely has exertional heat stroke, in which core temperature elevations may occur rapidly; therefore, measures directed at reducing his core temperature are appropriate and must be continued. Benzodiazepines are first-line therapy for shivering or seizures in heat stroke. References: This concludes our lecture on environmental disorders. Thank you for listening!

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