Paramedic Entrance Exam

Directions: Carefully read the EMS related article below. Answer the questions in this exam based on the information presented in the article. Each question is worth 4 points. Cold-Related Emergencies Introduction Cold-related injuries and hypothermia are not new concepts in medicine. Throughout history there have been reports of cold-related injuries, Most of these occurred during military campaigns. During 1812-1813 there are reports from Baron de Larrey, Napoleon’s Chief Surgeon, of massive amounts of frostbite injuries. These reports describe the freezing, thawing and then refreezing of extremities that lead to thousands of soldiers requiring amputations. Many others died of tetanus sustained from their wounds. The treatment modality of the time was rubbing the frostbitten extremities with snow. This remained the mainstay of treatment until the l950’s when rapid rewarming was first studied. Hypothermia remains a significant problem in the United States. More than 700 people die from hypothermia each year. Most at risk are patients at the extremes of age and those with altered mental status. Elderly patients have difficulty sensing cold, and neonates have large body surface areas and have difficulty conserving heat. In this article we will explore the normal physiology of temperature control. We will also review conditions such as nonfreezing injuries, freezing injuries and hypothermia. Finally we will review the common clinical presentations of these conditions as well as the treatment modalities. Normal physiology During normal activities temperature is controlled by a variety of factors. As we interact with the environment, body temperature falls when heat loss is greater than production. The skin is the primary organ of temperature regulation. Heat loss occurs as the result of conduction, convection, radiation or evaporation. Conduction is the transfer of heat by direct contact. Convection is the transfer of heat by the movement of heated particles from the body; convection is particularly important when we talk about windy conditions. Heat is also lost through radiation from non-insulated parts of the body. Evaporation, the most efficient method of heat loss, occurs when water converts from liquid to vapor off the skin or from breathing. Heat generation occurs through various processes. The hypothalamus controls most of these processes through hormonal regulation. Generally the two methods the body uses to avoid heat loss are conservation and heat production. Conservation happens via peripheral vasoconstriction and by behavioral responses to a cold environment. The behavioral responses such as putting on a coat or coming inside from the cold are easily blunted when drugs or alcohol are involved. Heat production occurs though shivering, where voluntary muscle is forced to contract involuntarily. The hypothalamus also triggers increased output from the thyroid and adrenal glands, which increases the body’s metabolic rate and increases heat. Non-freezing Injuries: Chilblains and Trench Foot Chilblains, also called Pernio, are mild inflammatory lesions that are caused by chronic exposure to damp nonfreezing temperatures. Typically the cutaneous changes occur within 12 hours of the exposure. These changes include local edema, erythema, cyanosis, and nodules. After rewarming, the nodules may become tender and blue and may remain for several days. Young women with Raynaud Phenomenon are most at risk. Trench foot got its name during World War I. Soldiers would spend long hours standing in trenches containing cold water. The pathophysiology involves direct injury to the soft tissue by prolonged cooling, which is accelerated by the wet conditions. On initial exam the feet appear mottled, pale and immobile; this is accompanied by numbness and tingling. With rewarming the extremity becomes hyperemic and as sensation returns the patient can experience severe burning pain. Treatment for both Chilblains and Trench foot is supportive with gentle rewarming and loose bandages. Prophylaxes for trench foot includes assuring proper boot fit and keeping feet as dry as possible. There is no specific therapy for trench foot; feet should be kept dry and elevated and be closely watched for signs of early infection. Freezing injuries: Frostnip and Frostbite Pathophysiology As was previously mentioned, one of the body’s main mechanisms of temperature regulation is through changes in cutaneous vascular tone. This is regulated by sympathetic adrenergic vasoactive fibers. Basal cutaneous flow rate in a 70 kg euthermic male is 200 – 500 ml/min. As the skin temperature drops to 57a F, flow rate drops to 20 - 50 mL/min. As the skin temperature drops further to 50a F, blood flow becomes negligible and the body begins to exhibit cold-induced vasoconstriction. This is a process by which there is cycling of vasoconstriction and vasodilatation every 5-10 minutes. This process eventually leads to central cooling. As the core body temperature drops, blood flow is completely shut down to the coldest extremities. Frostbite occurs through two phases. Phase I is where irreversible tissue damage occurs. Skin temperature falls below freezing and ice crystals begin to form in the extracellular space. The crystals cause an osmotic force that leads to intracellular dehydration and increased intracellular sodium concentration; this causes proteins to become denatured and enzymes are destroyed. As the process continues intracellular ice crystals form that may physically damage cells. Phase II is characterized by the reperfusion injury that occurs as the extremity is rewarmed. Oxygen free-radicals are generated as well as many vasoactive substances such as prostaglandins and thromboxane. These substances lead to a leaky endothelium and vasoconstriction, which in turn causes necrosis, ischemia and dry gangrene. Three zones characterize the area of frostbite injury. The zone of coagulation is the most distal area where damage is the most severe and irreversible. The most proximal zone is called the zone of hyperemia and generally recovers within ten days. The middle zone, called the zone of stasis, is characterized by severe but possibly reversible cell damage. This is the zone that is targeted during treatment. Clinical Features Frostbite can present on any skin surface but is generally found on exposed areas. Clinically frostbite is classified by severity, using a degree scale similar to bums. Initial clinical appearance can be deceiving. Classification Signs Symptoms Superficial First degree: Partial skin freezing Erythema, Edema, Hyperemia, No blistering/necrosis Transient stinging and burning, Throbbing Second degree: Full-thickness injury Erythema, Edema, Vesicles, Blisters with Eschar formation Numbness, Vasomotor disturbances Deep Third degree: Full-thickness injury with subcutaneous freezing Violaceous or hemorrhagic blisters, Skin necrosis, Blue discoloration Initially: No sensation, tissue feels like “wood” Late: Shooting pains, Burning sensation Fourth degree: Full-thickness injury with subcutaneous tissue, muscle, tendon, and bone freezing Little or no edema Initially: Mottled or cyanotic Eventually: Dry black skin No sensation Possible joint pain Treatment Field management of frostbite is simple. The involved extremities should be wrapped in dry sterile gauze, with affected fingers and toes separated. In most cases more aggressive management should be delayed until the patient is in the emergency department. In cases where transport is extended for several days, thawing should be initiated. Thaw in l04a F water for 10 - 30 minutes with active motion; pain medication should be considered. After thawing is completed clear blisters should be debrided, NSAIDs should be given as well as tetanus prophylaxis and penicillin. Hypothermia Pathophysiology and Clinical features Various organ systems respond differently to hypothermia. In general body temperatures from 89.6 a F - 95a F constitute mild hypothermia and body systems respond by increasing metabolic activity to try to retain heat. Below 89.5a F metabolism begins to slow and there is a decrease in O2 use and CO2 production. The cardiovascular system initially responds with a general excitation. There is an increase in heart rate, cardiac output and blood pressure. As the temperature decreases these all fall. Cardiac output and blood pressure become depressed by the negative inotropic and chronotropic effects of hypothermia and ever further by concomitant hypovolemia. Hypothermia also causes characteristic ECG changes and may cause lifethreatening dysrhythmias. The Osborn (J) wave is a slow positive deflection at the end of the QRS. It is characteristic, but not pathognomonic of hypothermia. The typical progression of the ECG is sinus bradycardia, followed by atrial fibrillation with a slow ventricular response, followed by ventricular fibrillation, and then asystole. Pulmonary changes initially include tachypnea followed by a progressive decrease in respiratory rate and tidal volume. Hypothermia also causes a left-shift in the oxyhemoglobin dissociation curve, leading to a decrease delivery of oxygen to tissues. Patients therefore have diminished oxygen reserves considering the diminished oxygen requirements. Oxygen should always be given. The CNS system is affected by a progressive depression of consciousness. Mild incoordination is followed by confusion, lethargy, and coma. Pupils may be dilated or unchanged. These changes are due to a decrease in cerebral blood flow. Cerebral oxygen requirements are decreased, even greater than other organ systems, which may help protect the brain against anoxia and damage. Intravascular volume is affected by two body systems. First the kidney loses the ability to concentrate the urine; this leads to a diuresis. The immobile hypothermic patient is also prone to rhabdomyolysis. Plasma also shifts into the extravascular space adding to the decreased in intravascular volume. Treatment The treatment of hypothermia includes both supportive care and specific rewarming techniques. Care must be taken to handle patients very gently due to the risk of inducing ventricular fibrillation. There has been great debate on when to perform CPR in an unmonitored arrested hypothermic patient. Opponents of CPR feel that pulses may be too difficult to feel and that CPR may induce ventricular fibrillation. They recommend waiting until confirmation of an arrested rhythm. Alternatively withholding CPR may lead to worsening brain hypoxia. It is important to understand that this controversy only applies to patients with severe hypothermia with core temperatures less than 82.4a F. Because many hypothermic patients are alcoholics Thiamine and D50 should be given. Rewarming of patients can be both passive and active. There are no prospective controlled studies that compare rewarming methods in adults, and each method has advantages and disadvantages. Rewarming Techniques Passive Rewarming: Removal from cold environment Insulation Active External Rewarming: Warm water immersion Heating Blankets and objects Radiant heat and forced heated air Active Core Rewarming: Inhalation rewarming, heated IV fluids GI tract lavage, Bladder lavage Peritoneal and pleural lavage Extracoporeal rewarming Mediastinal lavage via thoracotomy Passive rewarming allows for a more physiologic approach. It allows the body to warm on its own using natural metabolic processes. For passive rewarming to occur the body must be capable of metabolic heat production. Also if the patient has cardiovascular compromise passive rewarming may not be fast enough. Active rewarming is separated into external rewarming and core rewarming. Active external rewarming is usually very effective and in most cases is the method of choice. External rewarming may not be effective in cases where patients have poor peripheral circulation. Core rewarming is the most aggressive and invasive of all the techniques it has the theoretical advantages of preferentially warming internal organs. However, these techniques are very invasive and have the risks inherent to the procedures. Approach to rewarming As was mentioned before, there are no prospective controlled studies that compare rewarming methods in adults, thus there can be no firm guidelines. Patients with mild hypothermia, which are still in the excitation phase, are best served by passive rewarming techniques. The most important criteria for determining how aggressive one should be is cardiovascular status. Patients who are hemodynamically stable do not need aggressive active rewarming regardless of temperature. If there is any risk of life-threatening dysrhythmias rapid rewarming is indicated to a core temperature of 86 - 89.6aF. If cardiovascular insufficiency remains, active core rewarming should be continued using multiple rewarming modalities. Conclusion Environmental factors should always be considered when evaluating patients. In this article we have reviewed the normal physiology of temperature control. We have also discussed conditions such as nonfreezing injuries, freezing injuries and hypothermia. Treatment of these patients depends on hemodynamic status. Great care must be taken to not worsen a patient’s condition by rewarming too quickly or too slowly. As prehospital providers our goal should be to stop the cooling process, maintain or stabilize vital signs, and transport carefully for definitive care.

All of the following are methods of heat loss, EXCEPT

Crystals formed during phase I frostbite cause an osmotic force leading to

Rapid rewarming became the mainstay of emergency treatment of frostbite in which era?

In freezing injuries, cutaneous blood flow becomes negligible at

Convection is the transfer of heat by

6. Vasoactive substances such as prostaglandins and thromboxane lead to a leaky endothelium and vasoconstriction, which in turn cause all of the following, EXCEPT

_______________ patients are the most at risk for hypothermia.

8. In the second phase of frostbite, there are three zones that characterize the area of frostbite injury. The zone that generally recovers within 10 days is the a. zone of stasis b. zone of cell damage c. zone of coagulation d. zone of hyperemia

Radiation is the transfer of heat by

All of the following define active external rewarming, EXCEPT

One method the body uses to avoid heat loss is

A patient having a suspected second degree frostbite injury would normally show signs & symptoms of all of the following, EXCEPT

Place the following hypothermia induced ECG changes in the proper order: 1. asystole 2. atrial fibrillation with slow ventricular response 3. sinus bradycardia 4. Osborn wave 5. ventricular fibrillation

Heat production occurs where

Field frostbite treatment of involved extremities notes that the extremities should be ,

CNS responses to hypothermia include all of the following EXCEPT

For patients with frostbite, when transport is delayed for several days, all of the following treatments should be considered, EXCEPT

A patient chronically exposed to damp, non-freezing temperatures may have signs & symptoms of local edema, cyanosis, nodules, and erythema. This patient may be diagnosed as having

The main center of temperature control in the body is

Initial cardiovascular response to hypothermia includes a. increased heart rate and increased B/P b. decreased heart rate and decreased B/P c. increased heart rate and decreased B/P d. decreased heart rate and increased B/P

Hypothermia causes a ___________ shift in the oxyhemoglobin dissociation curve, leading to an increase in delivery of oxygen to tissues.

Basal cutaneous flow rate in a 70 kg euthermic male is

A patient who presents with a foot that is erythematous, edematous, hyperemic, and throbbing, after a 3 day camping trip, most likely has?

In the development of hypothermia and frostbite, the process of cyclic vasoconstriction and vasodilatation occurs every