Chapter 38: Environmental Emergencies

Chapter 38

Environmental

Emergencies

National EMS Education

Standard Competencies

Trauma

Integrates assessment findings with principles of epidemiology and pathophysiology to formulate a field impression to implement a comprehensive treatment/disposition plan for an acutely injured patient.



Environmental Emergencies

Recognition and management of

− Submersion incidents

− Temperature-related illness




Pathophysiology, assessment and management of

− Near drowning

− Temperature-related illness

− Bites and envenomations




Pathophysiology, assessment and management of

− Dysbarism

• High-altitude

• Diving injuries

− Electrical injury

− Radiation exposure

− High-altitude illness

Introduction

• Environmental emergencies: Medical conditions caused or worsened by weather, terrain, or unique atmospheric conditions at high altitude or underwater

Introduction

• EMS providers may be called to emergencies in:

− Endurance sports events

− Mass gatherings

− Acutely confused older patients

© Martin Pisek/ShutterStock, Inc.

Introduction

• Certain weather conditions affect ability to adapt to environment:

− Wind

− Rain

− Snow

− Temperature extremes

− Humidity

Introduction

• Emergency locations may affect:

− Learning about emergency

− Responding to scene

− Reaching patients in remote settings

Introduction

• Common risk factors predispose people to environmental emergencies.

− Younger and older people —harder to maintain thermoregulation

− Preexisting conditions (diabetes, cardiac disease)

− Dehydration

Homeostasis and Body

Temperature

• Body processes that balance supply and demand of body ’s needs

• Thermoregulation: Thermosensitive neurons in anterior hypothalamus balance heat production and dissipation.


Temperature

• Body tries to keep temperature of 98.6

° F.

• CBT: Temperature in part of body consisting of heart, lungs, brain, and abdominal viscera

• Starting temperature for:

− Hypothermia —95 ° F

− Heat stroke —104 ° F


Temperature

• Oral temperature used for measurement in general medical conditions

− Can vary dramatically from CBT if patient is:

• Breathing by mouth

• Drinking hot or cold liquids

• Axillary temperature (armpit) about 1 ° F cooler

• Rectal temperature about 1 ° F hotter


Temperature

• Rectal thermometers most accurate means of determining CBT, but CBT unlikely to affect treatment

Thermoregulatory Mechanisms

• Hypothalamus hosts main thermoregulatory center.

• Hypothalamus receives signals from:

− Thermoreceptors in skin and muscles

− Central receptors in core, triggered by blood temperature changes


• At rest, the body:

− Produces heat by metabolism of nutrients, with liberation of water and carbon dioxide

• Basal metabolic rate (BMR): Heat energy produced at rest from normal body metabolic reactions


• BMR of average 70-kg person is around

70 kcal/hour, based on factors including:

− Age

− Gender

− Stress

− Hormones


• Heat loss to environment increases as ratio of body surface area to body volume increases.

− With two people of the same weight, the shorter will have a higher BMR.

− Exertion affects metabolic rate.


• Heat generated by metabolism and glycogen breakdown warms the body.

− Excess dissipated by temperature gradient between body and outside environment

− If environmental temperature is higher, body heats by absorption of outside heat.


• Skin plays vital role in body temperature regulation.

− Can both conserve and liberate heat energy through skin

• To liberate heat, blood flow to skin can include up to

8 L/min and 60% of cardiac output.

• In cold, blood flow can approach zero in certain areas.

Physiologic Reponses to Heat and Cold

• Thermolysis: Release of stored heat and energy of the body

− Increase in CBT causes vasodilation and sweating, which causes:

• Increased effective vascular system volume

• Increased heart output

• Increased pulse rate and stroke volume


• Cooling can be done by:

− Radiation —via electromagnetic waves

− Conduction —via direct physical contact

− Convection —moving air or liquids

− Evaporation —conversion of liquid to gas


• Thermogenesis: Production of heat and energy to deal with cold stressors

− Skin is body ’s thermostat in cold environment

− Shivers with cold skin, even if CBT not lowered

− Hypothalamus stimulates peripheral vasoconstriction to shunt blood to core.

− Heavier people are more insulated from cold.

Pathophysiology, Assessment, and Management of Heat Illness

• Heat illness: Increase in CBT due to inadequate thermolysis

− Inability to rid heat buildup from body because of:

• Hot and humid conditions, mobility

• General health/preexisting illness, age

Risk Factors for Heat Illness

• Older people are at particular risk

− Perspire less

− Acclimatize more slowly

− Feel thirst less readily

− Decreased mobility

− Chronic conditions


• Medications that affect temperature regulation ability include:

− Diuretics —dehydration and electrolyte disturbances

− Beta blockers —slow tachycardic response to heat stress


• Infants and young children are vulnerable.

− Proportionately higher metabolic heat production

− CBT rises faster during dehydration.

− Smaller organ and vascular systems do not dissipate heat as well.

• Military recruits and athletes also at increased risk

Heat Cramps

• Pathophysiology

− Acute, involuntary muscle spasms

− Occur from:

• Profuse sweating

• Sodium loss

− Most often afflict those in good physical condition

Heat Cramps

• Assessment

− Starts during strenuous or prolonged activity

− Usual presentation:

• Severe, incapacitating pain

• Hypotension and nausea

• Rapid pulse

• Pale and moist skin

• Normal temperature

Heat Cramps

• Management

− Treatment to eliminate exposure and restore lost salt and water:

• Move patient to cool environment.

• Position supine if feeling faint.

Heat Cramps

• Management (cont ’d)

− If no nausea:

• Give one or two glasses of salt-containing solution.

− If nauseated:

• Rapidly infuse normal saline by IV.

Heat Syncope

• Pathophysiology

− Orthostatic syncopal episode in nonacclimated people under heat stress

− Can occur from:

• Prolonged standing

• Standing suddenly from a sitting or lying positions

Heat Syncope

• Assessment and management

− Place patient in supine position.

− Replace fluid deficits.

− If patient does not recover quickly, suspect:

• Heatstroke

• Heat exhaustion

• Cardiac syncope

• Atypical acute coronary syndromes

Heat Exhaustion

• Pathophysiology

− Milder form of heat illness, with:

• Volume depletion

• Heat stress

− Two types:

• Water depleted

• Sodium depleted

Heat Exhaustion

• Exercise-associated hyponatremia

− Prolonged exertion with excessive fluid intake

− Too much water in body in relation to sodium

− Arginine vasopressin (AVP) contributing factor

• Hormone that increases water absorption in kidneys

Heat Exhaustion

• Symptoms include:

− Headache

− Fatigue

− Weakness

− Dizziness

− Nausea

− Vomiting

− Abdominal cramping

• Other signs and symptoms:

− Profuse sweating

− Pale, clammy skin

− CBT normal or slightly elevated

− Tachycardia

− Orthostatic hypotension

Heat Exhaustion

• Management

− Move to cool environment.

− Remove excess clothes.

− Place supine with legs elevated.

− If temperature is elevated:

• Sponge, spray, or drip with tepid water and fan gently.

− Oral hydration with sports drinks

Heat Exhaustion

• If suspected exercise-associated hyponatremia, no fluids by mouth

− Check blood sodium level.

− IV normal saline or hypertonic saline

Heatstroke

• Pathophysiology

− Least common but most deadly

− Caused by severe disturbance in body ’s thermoregulation

− Findings to determine heatstroke:

• Core temperature of more than 104 ° F (40 ° C)

• Altered mental status

Heatstroke

• Consequences are related to effects of elevated temperatures on the body ’s cells.

• Two heatstroke syndromes:

− Classic heatstroke

− Exertional heatstroke

Heatstroke

• Assessment

− Signs include:

• Irritability, combativeness

• Signs of hallucination

• Dehydration

• Dry, red, hot skin (classic heatstroke)

• Pale and sweaty skin (exertional heatstroke)

Heatstroke

• Fever and conditions that mimic heatstroke

− Fever can signal a fight against infection.

− Anticholinergic poisoning

− Syndromes that cause hyperthermia

− Malignant hyperthermia

Heatstroke

• Management

− Evaluate ABCs.

− Move patient to a cool environment.

− Cool as rapidly as possible.

− Start an IV line, and monitor cardiac rhythm.

− Prepare to treat for seizures.

Prevention of Heat Illness

• Measures to protect from heat illness:

− Acclimatize when possible.

− Maintain personal fitness.

− Limit time spent in heavy activity, especially during hot periods.

− Maintain hydration, eat appropriately, and rest.

− Improve cardiovascular and muscular strength.

Prevention of Heat Illness

• Be alert for early heat illness symptoms:

− Headache

− Nausea

− Cramps

− Dizziness

Local Cold Injury/Frostbite

• Often localized to extremities or exposed areas

• Frostbite: Ischemic injury classified as superficial or deep

− Frostnip is a mild form of frostbite.


• Deeper degrees of frostbite —tissue freezes.

• Risk factors:

− Cold exposure without adequate clothing

− Impeding circulation to extremities

− Fatigue, dehydration, or hunger

− Direct contact with cold objects

− Hypothermia


• Superficial frostbite: Altered sensation of numbness, burning

− Skin is:

• Waxy and white

• Firm to palpation

− Thawing causes:

• Cyanotic skin

• Hot, stinging sensation

Courtesy of AAOS


• Deep frostbite

− White, yellowwhite, or mottled blue-white skin

− Feels hard, cold, without sensation

− Major damage when tissues thaw

• May cause gangrene

Courtesy of Dr. Jack Poland/CDC


• Management

− Difficult to determine depth of injury

− Reperfusion injury can be excruciating.

− Treatment is determined by distance to hospital and if partially or completely thawed.


• General principles:

− Remove from cold, and remove wet clothing.

− Do not rub or massage area.

− Transport with injured area elevated.

− Give pain medication as needed.

− Cover blisters with dry, sterile dressing.

− Consider rewarming if no potential of refreezing.


• Principles of rewarming:

− Rewarm before transport if medical control agrees.

• Water bath —ensure immersion without touching container.

• Temperature between 98 ° F and 100 ° F

• Administer IV analgesia.

Trench Foot and Chilblains

• Trench foot similar to frostbite but can occur at temperatures as high as 60 ° F

− From prolonged exposure to cool, wet conditions

− Prevention best treatment —keep feet warm and dry.

Trench Foot and Chilblains

• Chilblains –itchy reddish or purple lesions on face or extremities

− Long exposure to temperature just above freezing

− Treatment:

• Remove from cold environment.

• Room temperature rewarming

Hypothermia

• Decrease in CBT starting at 95 ° F due to:

− Inadequate thermogenesis

− Excess environmental cold stress

© Andy Barrand, The Herald Republican/AP Photos

Hypothermia

• Body regulates cold stress by:

− Increasing thermogenesis

− Decreasing thermolysis

− Adaptive behavioral changes

Hypothermia

• Risk factors:

− Increased thermolysis

− Decreased thermogenesis

− Impaired thermoregulation

Hypothermia

• Hypothermic condition results from:

− Cold temperatures

− Improper gear

− Wetness and dehydration

− Length of exposure

− Intensity of weather conditions

Hypothermia

• Alcohol is the most common cause of heat loss in urban settings.

− Hinders body ’s attempt to insulate warm core

• Impairs shivering thermogenesis.

• Promotes cutaneous vasodilation.

• Inadequate glycogen stores from liver disease

• Subnormal nutritional status

• Impairs judgment.

Hypothermia

• Others at risk include:

− Those using:

• Sedative medications

• Tricyclic antidepressants

• Phenothiazines

− Older patients

− Trauma patients

Hypothermia

• Ensure ambulance is preheated.

− Conserve patient ’s body heat.

© Jim Cole/AP Photos

Hypothermia

• National Institutes of Health —focus on

“umbles” in early stages:

− Stumbles

− Mumbles

− Fumbles

− Grumbles

Hypothermia

• 2010 American Heart Association ACLS guidelines define:

− Mild hypothermia —CBT greater than 93.2

° F

− Moderate hypothermia —CBT between 86 ° F to

93.2

° F

− Severe hypothermia —CBT below 86 ° F

Hypothermia

• Classifications:

− Acute

− Subacute

− Chronic

• Also classified as:

− Primary

− Secondary

Hypothermia

• No strong correlation between specific CBT and signs and symptoms.

− Most dramatically apparent in CNS, where everything slows

• Thinking and feeling

• Speaking slow and slurred

• Impaired reasoning ability and coordination

Hypothermia

• Signs and symptoms may resemble:

− Stroke

− Head injury

− Acute psychiatric disturbance

− Alcohol intoxication

Hypothermia

• Changes in cardiovascular system lead to:

− Increase in blood viscosity

− Impaired circulation and hypovolemic state

− State of hypovolemia

Hypothermia

• 2010 AHA guidelines suggest attempting defibrillation once.

− If persisting, treatment may include repeating attempts in conjunction with rewarming.

• Respiratory rate initially speeds up, then slows, with decreased minute volume:

− Tracheobronchial secretions increase

− Bronchospasm

− Pulmonary edema

Hypothermia

• Muscular system slows.

− Initial reaction is shivering.

− Shivering stops at around 91 ° F.

• Cold muscles become progressively weaker and stiffer.

Hypothermia

• Care aimed at preventing more heat loss and rewarming

− Strip patient of wet cloths.

− Insulate patient from further heat loss.

Hypothermia

• Breathing patients with pulse

− Mild hypothermia (93.2

° F)

• Passive rewarming

− Moderate hypothermia (86 ° F to 93.2

° F)

• If perfusing rhythm, active external rewarming

− Severe hypothermia (Less than 86 ° F)

• Active core rewarming sequence in-hospital

Hypothermia

• Patients with no pulse or not breathing

− 2010 BLS guidelines recommend CPR if no signs of life are present.

• Rapid rhythm identification

• One defibrillation attempt

• IV access and infuse warm normal saline

• Attempt advanced airway, and give warm, humid oxygen.

Hypothermia

• Patients are generally considered dead if:

− Obvious lethal traumatic injuries

− So solidly frozen as to block airway or chest compression efforts

• Resuscitation unlikely if submersion precedes arrest.

Drowning

• Process of experiencing respiratory impairment from submersion or immersion in liquid

• Outcomes include:

− Death

− Morbidity

− Near morbidity

Drowning

• Drowning continuum:

− Breath holding

− Laryngospasm

− Accumulation of carbon dioxide/inability to oxygenate lungs

− Respiratory and cardiac arrest from tissue hypoxia

Drowning

• Risk factors:

− Toddlers — bathtubs

− School-age children —pools

− Teens —lakes and rivers

− Comorbidities

Drowning

• Predictable sequences starting with inability to keep face out of liquid

− Length of breath holding depends on:

• State of health and fitness

• Level of panic

• Water temperature

Drowning

• Resuscitation is the same as for others in respiratory or cardiac arrest.

• Reaching victim — leave to those trained/experience d in water rescue

Drowning

• Treatment follows ABCs.

− Establish airway.

− Cervical spine precautions, especially if:

• History of diving or water slide

• Signs of injury

• Alcohol intoxication

Drowning

• Continue rescue breathing until on land.

• Once on solid surface:

− Start supplementary oxygen.

− Determine pulse.

− Continue to treat according to ABC guidelines.

Drowning

• Start chest compressions after two breaths.

− Establish IV access.

− Administer indicated medications.

− Perform cardiac monitoring.

− Defibrillate shockable rhythms.

− Do not perform manual abdominal thrusts.

− Suction to clear airway.

Drowning

• Most drowning victims receiving rescue breathing or compressions will vomit.

− Remove vomit from mouth via:

• Suction

• Finger swipes

• Other devices

− Consider placing on side.

Drowning

• Maintain some positive pressure at end of exhalation to:

− Keep alveoli open.

− Drive fluid accumulated in alveoli back into interstitium or capillaries.

Drowning

• Positive end-expiratory pressure (PEEP)

− Maintains some positive pressure at end of expiratory phase.

− Indicated for intubated patients with long transports

− Some devices allow PEEP via endotracheal tube.

− Portable ventilators usually have PEEP setting.

Drowning

• If ET tube inserted, insert nasogastric tube to decompress stomach.

• If pulse absent, implement ALS measures for cardiopulmonary arrest:

− IV access

− Epinephrine administration

− Cardiac monitoring, defibrillation if needed

Drowning

• Do not give up on submersion patient.

− Successful resuscitation with complete neurologic recover in more than 1 hour of submersion in icy water

• Hypothermia protects body and brain from hypoxia

• Hypothermia more often dangerous than protective

Drowning

• Search for comorbidities:

− Trauma

− Hypoglycemia

− Acute coronary syndrome

− Cerebrovascular accident

Drowning

• Major predictors of outcome:

− Length of submersion

− Response to field resuscitation

− If awake upon hospital arrival, likely a better outcome

Drowning

• Postresuscitation complications

− Occur hours to days after submersion:

• Adult respiratory distress syndrome

• Hypoxic brain injury

• Multiorgan failure

• Sepsis syndrome

Diving Injuries

• Four modes of diving

− Scuba

− Breath-hold

− Surface-tended

− Saturation

General Pathophysiology: Physical

Principles of Pressure Effects

• Pressure —a force per unit area

− Different ways to express; for example, weight of air at sea level:

• 14.7 pounds per square inch

• 760 mm Hg

• 1 atmosphere absolute (ATA) (most common)



• Water much denser than air.

− For every 33 feet of seawater (fsw), pressure increases 1 ATA

• Sea level —pressure is 1 ATA

• 33 fsw —pressure is 2 ATA

• 66 fsw —pressure is 3 ATA

− Majority of scuba diving is at depths between 60 and 120 fsw (3 to 5 ATA).



• Liquid volume does not change with pressure.

− Body/tissues primarily water —not so affected by pressure changes in descent or ascent

− Gas-filled organs are compressible and follow several physical laws.



• Boyle ’s law—at a constant temperature, volume of a gas is inversely proportional to its pressure:

− Double pressure on gas, halve volume ( PV = K )



• Effect is most extreme near surface.

• Explains barotraumas that occur in gas-filled body areas



• Dalton ’s law—each gas in mixture exerts same partial pressure it would exert if it were alone in the same volume

− The total pressure of a mixture of gases is the sum of the partial pressures of all gasses in the mixture.

• Fresh air —P total

= PO

2

+ PCO

2

+ PN

2



• Henry ’s law—the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the liquid

− P – kC



• Commercial divers use a decompression schedule.

− Recreational divers —no-decompression limit to keep from decompressing

− Enriched Nitrox gas decreases risk of nitrogen narcosis.

General Assessment:

Diving History

• When did symptoms start?

• Type of diving and equipment?

• Type of tank?

• Diving site and water temperature?


Diving History

• Number of dives in the last 72 hours, and:

− Depth?

− Bottom time?

− Surface interval?

• Dive computer used?

• Safety stops used?


Diving History

• Any attempts at in-water decompression?

• Any dive complications?

• What were predive and postdive activities?

Injuries at Depth

• Nitrogen narcosis: Altered mental status from breathing compressed nitrogencontaining air at depth


• Signs and symptoms:

− Euphoria

− Inappropriate and dangers behavior

− Tingling of lips, gums, and legs

− May panic and surface too quickly.


• Management

− Lower nitrogen partial pressure through:

• Controlled ascent

• Use of a mixed gas for diving with a decreased nitrogen percentage

Barotrauma

• Result of pressure imbalance between gasfilled spaces in the body and external atmosphere

− Can affect any gas-filled space in the body

− Scuba divers generally protected by breathing compressed air

Barotrauma

• Pressure in middle ear cannot be equalized with outside water pressure if:

− Blockage of eustachian tube

− Valsalva maneuver does not equalize pressure.

• “Middle ear squeeze” syndrome causes severe pain.

• If tympanic membrane ruptures

− Nausea/vomiting

− Vertigo

− Panic/rapid ascent

Barotrauma

• Treatment:

− Loose dressing for bleeding ear

− IV antiemetics or sedatives

− Possible decompression symptoms:

• Hearing loss

• Vertigo

Pulmonary Overpressurization

Syndrome (POPS)

• If divers fail to exhale during ascent, pressure in lungs increases.

• POPS ( “burst lung”) causes:

− Pneumothorax

− Mediastinal/subcutaneous emphysema

− Alveolar hemorrhage

− Lethal arterial gas embolism (AGE)


Syndrome (POPS)

• Relative pressure and volume changes greatest near surface of water.

− Small overpressurization can rupture alveoli.

− Diving students trained to exhale constantly during ascent to vent air from lungs.

− COPD and asthma patients have slightly higher risk


Syndrome (POPS)

• Signs and symptoms depend on where escaping air ends up; most often into mediastinum and beneath skin, causing:

− Full sensation in throat

− Pain on swelling

− Dyspnea

− Substernal chest pain


Syndrome (POPS)

• Physical examination may show:

− Palpable subcutaneous air above clavicles

− Crunching noise synchronous with heartbeat audible by auscultation (Hamman ’s crunch)


Syndrome (POPS)

• Prehospital treatment depends on if arterial gas embolism is present

• In the field, provide 100% oxygen by nonrebreathing mask.

Arterial Gas Embolism

• Air bubbles from ruptured alveoli enter pulmonary capillaries and travel back to left side of heart.

− Bubbles may enter coronary arteries and produce effects of MI.

− Majority rise to head, causing strokelike symptoms.


• Dramatic clinical picture, with symptoms:

− Involving most cerebral functions

− Appearing within seconds to minutes after surfacing

• History of panic or uncontrolled ascent, but can occur in shallow water


• Patient can experience:

− Weakness or paralysis of extremities

− Seizure activity

− Unresponsiveness

− Parasthesias

− Visual disturbances

− Deafness

− Changes in mental status


• Transport to a hyperbaric chamber facility as soon as possible.

Courtesy of Perry Baromedical Corporation


• Treatment includes:

− Ensure adequate airway.

− Administer 100% supplemental oxygen.

− Transport in supine position by ground.

− Establish IV access, and administer normal saline.

− Monitor cardiac rhythm.

Decompression Sickness

• Nitrogen bubbles in blood and tissues come out of solution during ascent.

− Bubbles cause damage by:

• Interfering mechanically with tissue perfusion

• Triggering chemical changes in body

− Multisystem disorder —can potentially affect every organ in the body


• Nitrogen and oxygen are carried to tissues; oxygen is metabolized, but nitrogen remains.

− If ascent slow enough, enough nitrogen will escape with each breath.

− If ascent more rapid than nitrogen can be removed, diver ’s tissues will begin to bubble.


• Other risk factors include:

− Obesity

− Dehydration

− Fatigue

− Flying within 12 to14 hours of diving


• Risk of severe neurologic DCS if patient has a patent foramen ovale

− Congenital defect in which foramen ovale between atria fails to close at birth

− May allow nitrogen bubbles to travel from pulmonary circulation into systemic circulation

− Increased damage to CNS and proximal spinal cord


• Type I —mild form that involves only:

− Skin

− Lymphatic system

− Musculoskeletal system

• Symptoms:

− Joint pain

− Mottled and pruritic skin

− Fatigue and weakness

− Lymph dysfunction leading to edema

(rare)


• Type II —symptoms in all other organ systems:

− Pulmonary

− Cardiovascular

− Nervous


• Management :

− Administer 100% oxygen.

− Manage acute problems.

− Transport to hyperbaric facility, even if symptoms appear to resolve.

Hyperbaric Oxygen Therapy

• Intermittent inhalation of pure oxygen under pressure greater than 1 ATA

− Mechanically reduces bubble size.

− Reduces nitrogen content.

− Increases oxygen delivery to ischemic tissues.

• Treatment pressures and times from established tables


• Indicated in patients with:

− AGE

− DCS

− Carbon monoxide poisoning

− Other subacute or chronic medical conditions

− Routine decompression of industrial divers


• Risks:

− May convert a pneumothorax into a tension pneumothorax if no chest tube

− Seizures from oxygen toxicity

− Barotrauma


• Care recommended in patients who:

− Are pregnant

− Have lung disease

− Have fever

− Have seizure disorders

• In patients with possible AGE or DCS, benefits may outweigh risks.

Other Gas-Related Problems

• Most recreational divers use compressed air.

− Tanks with various mixtures of nitrogen/oxygen allow divers to be underwater longer.

− Less nitrogen —less likely to develop DCS

− More oxygen —prone to oxygen toxicity (CNS emergency)


• Signs and symptoms include:

− Dizziness

− Lack of coordination

− Confusion

− Twitching or paresthesia

− Underwater seizures


• Evacuation from water:

− Controlled ascent

− Ensure diver maintains airway and has air access during ascent.

• AGE risk does not increase when seizing or postictal patient is brought to surface.

− DCS may be a concern.


• Once back in boat or on shore, treatment includes:

− 100% oxygen

− Supportive therapy

− Hyperbaric oxygen therapy in pregnant patients or those with significant exposure

Shallow Water Blackout

• Frequently seen in teenage boys competing in remaining the longest underwater

− May hyperventilate just before going under to extend endurance

• Decreases PaCO

2

, causing cerebral vasoconstriction

• PaO

2 increases as swimmer descends.


• Because PaCO

2 drive suppressed is relatively low, respiratory

− Diver can remain underwater longer, but oxygen continues to be removed from alveoli

− Cerebral function maintained at depth by increased PaO

2


• On surfacing:

− Ambient pressure rapidly decreases.

− PaO

2 plummets.

− Hypoxia and cerebral vasoconstriction together cause blackout just before reaching surface.


• Treat as for any other case of drowning.

• When patient regains consciousness, explain seriousness of injury.


• DAN —24-hour consultation service

− (919) 684-8111

− Connect with physician experienced in diving medicine who can:

• Assist with diagnosis.

• Provide advice for early management.

• Supervise referral to recompression chamber.

Altitude Illness

• Altitude: Terrestrial elevation above 1,500 m

(5,000 ft)

− Level where physiologic changes from hypobaric hypoxia begin

− Altitude illness: Low partial pressure of oxygen leads to hypoxia


• Barometric pressure varies according to:

− How far from the equator

− Season –typically lower in winter

− Local changes in barometric pressure, can alter

“relative altitude” by 500 to 2,500 ft.


• Types:

− Acute mountain sickness (AMS)

− High-altitude cerebral edema (HACE)

− High-altitude pulmonary edema (HAPE)


• Typically occurs in those rapidly ascending to above 8,000 ft, but can occur as low as

6,500 ft.

− Symptoms usually within 6 to 10 hours.

− Directly related to how high and how quickly arrived


• Body adjusts by defending amount of oxygen available for delivery to tissues.

− First response is hyperventilation.

− Quickly leads to respiratory alkalosis

− Kidneys secrete bicarbonate in urine.

− Causes compensatory metabolic acidosis


• Hypoxia main problem but mechanism poorly understood

− Initiates series of reactions that cause overperfusion to brain and lungs, increasing:

• Capillary pressures

• Leakage

• Cerebral and pulmonary edema


• HAPE results from marked vasospasm of pulmonary arteries.

− Results in high pressure driving fluid from pulmonary vasculature into lungs

− Does not result from volume overload state

• Nitroglycerin and furosemide not used for HAPE


• Risk factors

− History of AMS

− Normal residence below 3,000 ft

− Obesity

− Rapid or high ascents

© Alan Heartfield/ShutterStock, Inc.


• Acute mountain sickness (AMS) symptoms include headache plus:

− Fatigue or weakness

− GI symptoms

− Dizziness or light-headedness

− Difficulty sleeping


• High-altitude pulmonary edema (HAPE)

− Two of the following:

• Dyspnea at rest

• Cough

• Weakness

• Chest tightness or congestion

− Two of the following:

• Central cyanosis

• Audible rales or wheezing

• Tachypnea

• Tachycardia


• High-altitude cerebral edema (HACE)

− Presence of change in mental status or ataxia in a person with AMS

− Presence of mental status changes and ataxia in a person without AMS


• Signs of possible causes other than AMS:

− Symptoms develop 4 or more days after higher elevations

− Lack of headache

− Failure of descent to improve signs or symptoms


• Management of all altitude illnesses includes

− Oxygen

− Descent

− Evacuation

− Various treatments specific to illness


• Prevention by:

− Acclimatization

− Use of acetazolamide for most susceptible


• AMS treatment :

− Acetaminophen or aspirin for headaches

− Antiemetics for nausea

− Acetazolamide for AMS and acclimatization

− Oxygen

− Do not ascend until symptoms resolve.


• HAPE treatment:

− Immediate descent

− Oxygen

− Medication as adjunctive treatment limited to patients where:

• Descent and oxygen are not easily available.

• Descent and oxygen do not rapidly help patient.


• HACE treatment:

− Oxygen

− Mandatory descent

− Dexamethasone given as soon as possible

• 8 mg by any accessible route, followed by 4 mg every 6 hours during descent/evacuation

Portable Hyperbaric Chambers

• Useful when descent cannot be carried out

• Patient placed inside bag and pressurized air pumped in

− Provides equivalent of descent of several hundred to several thousand feet

Lightning Strike

• Leading cause of environmental death in

United States

• Different than industrial electrical injuries:

− Not AC or DC current

− Massive unidirectional flow, voltages in millions

− Duration miniscule

− Energy flows over victim.


• Most common injury is side splash injury

• Bolt ’s energy may act as a giant depolarizing charge to body.

− Can cause asystole and respiratory arrest:

• Diaphragm depolarization

• Brainstem-induced central apnea


• After depolarization:

− Heart usually spontaneously resumes sinus rhythm.

− Respiratory effort does not restart.

− If apnea remains, heart will go into secondary hypoxic arrest.


• Morbidity high

− As many as 75% have long-term complications

− May have

“Lichtenberg figure ”

− Evaluate for trauma.


• “Reverse triage”

− Attend those who appear dead first.

− Strikes induce cardiac and respiratory arrest.

− CPR/rescue breathing

• All lightning strike victims should be evaluated at a medical facility.

Envenomation: Bites and

Stings

• Most common venomous creatures

− Bees, wasps, hornets, fire ants

− Snakes

− Black widow, brown recluse, hobo spiders

− Scorpions


Stings

• Most frequent cause of mortality — anaphylactic reaction

− Most common and most deaths from hymenoptera bites

− Treatment is same as in other cases of anaphylaxis


Stings

• Treatment includes:

− ABCs management

− Transport

− Obtain vascular access.

− Ensure scene is safe from venomous creatures.

Hymenoptera

• Most common cause of deaths:

− European honey bees (Aphidae)

− Yellow jackets, wasps, hornets

(Vespidae)

− Fire ants

(Formicidae)

© Stuart Elflett/ShutterStock, Inc.

Hymenoptera

• Venom is a mixture of proteins causing local reactions:

− Erythema

− Swelling

− Pruritus

• Melittin —protein that causes immediate pain

Hymenoptera

• Local reaction in ¼ of stings.

− Reaction can be extensive.

• Anaphylaxis occurs rapidly, typically within

10 minutes (within 60 minutes 95% of time).

Hymenoptera

• If no history of allergic reaction and no systemic reaction, transport is not necessary.

− Advise patient of anaphylaxis signs.

− Wound should be checked if no improvement in

24 hours

− Infection likely from fire ant stings

Hymenoptera

• Treatment focuses on pain and minimization of infection risk.

− Determine if stinger and venom sac are still attached.

• If so, remove as rapidly as possible.

• Clean wound thoroughly.

• Cool compresses and elevation for reaction

• Antihistamines for symptomatic treatment

Hymenoptera

• Additional treatment for fire ant stings include:

− Moving patient and crew away from site.

− Brushing off ants.

− Providing supportive care as needed.

Snake Bites

• Two snake families of concern in United

States:

− Viperidae

− Elapidae

• Most common in southeastern United

States

Snake Bites

• Pit viper venom has both hemolytic and proteolytic enzymes, causing extensive local tissue damage and systemic effects:

− Soft-tissue swelling and necrosis

− Local, then systemic bleeding

− Clotting problems

Snake Bites

• Coral snakes have potent neurotoxic venom:

− Paresthesias

− Fasciculations

− Weakness

− Respiratory difficulty

− Strokelike symptoms

Snake Bites

• Pit vipers

− Heat-sensing pits between the eye and the nostril

− Main types:

• Rattlesnakes

• Cottonmouths

• Copperheads

Snake Bites

• Coral snakes

− Small fangs

− Snakes need to stay attached for envonemation.

− Several hours for symptoms to show

− Transport if possible bite

Courtesy of Luther C. Goldman/U.S. Fish & Wildlife Service

Snake Bites

• Be certain snake is no longer a danger.

• Note time of bite.

• Determine type of snake.

− Remember —dead snakes can still bite.

Snake Bites

• Crotalid venom

− Promotes tissue destruction through:

• Proteolysis

• Hemolysis

•

Thrombogenesis

• Elapid venom

− Neurotoxin causing respiratory failure and death

Snake Bites

• Crotalid bite symptoms include:

− Swelling, bleeding

− Weakness

− Unconsciousness

− Tachycardia

− Coagulopathies

− Shock, cardiovascular collapse

Courtesy of AAOS

Snake Bites

• Degree of envenomation determined by symptoms:

− Mild —minimal local swelling with no systemic symptoms

− Moderate —swelling extending up extremity, systemic symptoms; no significant bleeding

− Severe —extensive soft-tissue swelling and severe systemic effects and bleeding

Snake Bites

• Treatment —provide antivenin (at hospital).

− Monitor ABCs.

− Clean wound with antimicrobials.

− Draw blood for hospital use (if protocols allow).

− Immobilize involved extremity in neutral position below heart level.

− Do not use excessive constriction.

− Remove constricting jewelry.

Spider Bites

• Estimated 34,000 species worldwide

• Most carnivores and can bite

• Three species of concern in US:

− Black widow

− Brown recluse

− Hobo spiders

Spider Bites

• Black widow —only female dangerous

− Glossy black with

½-inch oval body

− Orange or reddish hourglass mark

− Lives in sheds, basements, woodpiles

− Most bites on hands or forearms

© Crystal Kirk/ShutterStock, Inc.

Spider Bites

• Brown recluse

(fiddleback) spider:

− Southern Midwest to Southeast

− Not aggressive, bites only when accidently encountered

Courtesy of Kenneth Cramer, Monmouth College

Spider Bites

• Hobo spiders

− Found in Northwest

− Bite clinically similar to brown recluse

− Slightly more aggressive

Spider Bites

• History of spider bite not always confirmed.

− Patient may report:

• Sudden, sharp prick followed by cramping

• Numbing pain beginning at bite area and gradually spreading

• Extreme restlessness (in case of black widow bite)

Spider Bites

• Black widow one of most venomous North

American spiders

− Local pain with rapid onset within 30 to 60 min

− Local muscle spasm and localized diaphoresis

− Diffuse and more muscle spasms

− If diaphragm affected, may have respiratory difficulty

Spider Bites

• Brown recluse bites usually painless

• Small percentage develop local and/or systemic symptoms

• Some may develop loxoscelism.

Courtesy of Department of Entomology, University of Nebraska

Courtesy of Department of Entomology, University of Nebraska

Spider Bites

• Black widow spider bite treatment:

− Intermittent ice use

− Antimicrobial cleansing of wound

− Pain and muscle spasm relief

− Prompt transport

• Further treatment:

− Monitor ABCs.

− IV access, oxygen

− Narcotics, muscle relaxants/sedatives

− Antivenin reserved for young and old with severe envenomation

Spider Bites

• Brown recluse/hobo spider bite treatment:

− Antivenin not routinely available

− Previous treatments (dapsone, steroids) shown to have no benefit

Scorpion Stings

• Only the bark scorpion is a potential threat to humans.

− Most result in a painful local reaction.

− Venom located in stinger ’s glands © Visual&Written SL/Alamy Images

Scorpion Stings

• Local sting symptoms within minutes, last several hours:

− Erythema

− Pruritis

− Urticaria

− Sharp, burning pain

− Paresthesia

Scorpion Stings

• A sting from the more neurotoxic bark scorpion causes few local symptoms.

− Systemic symptoms begin within minutes

− Peak at 4 to 6 hours

− Resolve within 24 to 72 hours

Scorpion Stings

• Symptoms

− Sympathetic stimulation:

• Tachycardia

• Hypertension

•

Palpitations

• Dry mouth

• High temperature

− Parasympathetic stimulation:

• Bradycardia

•

Hypotension

• Salivation

• Defecation

• Cranial nerve findings

Scorpion Stings

• Symptoms (cont ’d)

− Somatic stimulation

• Muscle contractions

• Myoclonic jerking

• Fasciculations

Scorpion Stings

• Prehospital treatment:

− ABCs

− Monitoring

− Transport

− Intubation if necessary

− IV for volumes needed for blood pressure

Scorpion Stings

• Prehospital treatment (cont ’d):

− Ice pack for local swelling

− Immobilize extremity

− Constricting band

− Treat seizures per protocol

Scorpion Stings

• In-hospital treatment includes care for

ABCs:

− Alpha and beta blockers

− Atropine

− Vasoactive drugs

− Antivenin if available

Tick Bites

• Blood-sucking arthropods found in rural, wooded areas

− Bites a concern because of disease transmission

• Lyme disease

• Rocky Mountain spotted fever

© Joao Estevao A. Freitas (jefras)/ShutterStock, Inc.

Tick Bites

• Treatment

− Remove tick:

• Use curved forceps to grab head as close to skin as possible.

• Pull straight up using even pressure.

• Do not twist or jerk.

• Dispose of it in container of alcohol.

Tick Bites

• Once tick is removed:

− Wash bite with soap and water.

− May be no reason to transport if patient is asymptomatic (check with local protocol).

− Advise patient to see a physician.

Summary

• Environmental emergencies: Medical conditions caused or worsened by weather, terrain, or unique atmospheric conditions such as underwater or high altitude

• Predisposing risk factors include very young, elderly, poor state of health, and certain medications.

Summary

• Thermoregulation: Body ’s ability to ensure a balance between heat production and release, with the hypothalamus and skin playing major roles

• Body produces heat through metabolism; basal metabolic rate is the heat energy produced at rest from normal metabolic reactions.

Summary

• Thermolysis: Release of heat and energy from the body

• Thermogenesis: Production of heat and energy for the body

• The body has four main means of cooling itself —radiation, conduction, convection, and evaporation.

Summary

• Heat illness: Increase in core body temperature from inadequate thermolysis

• Heat cramps: Acute, involuntary muscle pains in abdomen or lower extremities from profuse sweating and sodium loss

• Heat syncope occurs when overheated patient suddenly moves. Place patient supine and replace fluids.

Summary

• Heat exhaustion can result from dehydration and heat stress.

• Heatstroke: Core temperature above 104 F

(40oC) and altered mental status

• Fever can mimic heatstroke.

• Dress appropriately, stay hydrated, and stay in shade or air conditioning to prevent heat illness.

Summary

• Frostbite: Local freezing of a body part and is classified as superficial or deep

• Superficial frostbite is characterized by numbness, tingling, or burning. The skin is white, waxy, and firm to palpation.

• Deep frostbite is characterized by white, yellow-white, or mottled blue-white injured body part and is hard, cold, and without sensation.

Summary

• Trench foot results from prolonged exposure to cool, wet conditions.

• Hypothermia: Decrease in core body temperature; can be mild, moderate, or severe

• Mild hypothermia: Core body temperature of greater than 93 ° F (33.9

° C)

Summary

• Moderate hypothermia: Core body temperature from 86 ° F to 93 ° F (30 ° C to

33.9

° C)

• Severe hypothermia: Core body temperature of less than 86 ° F (30 ° F).

• Resuscitate hypothermic patients who are not breathing or without a pulse.

• Resuscitation can be attempted in cases of cardiac arrest and hypothermia.

Summary

• Drowning: Process of experiencing respiratory impairment from submersion or immersion in liquid

• Rescuing a patient who has drowned should be undertaken by specially trained rescuers.

• For diving injuries, obtain details such as type of diving, type of tank, number of dives in the past 72 hours, and predive and postdive activities.

Summary

• Barotrauma can happen during dive descent from the pressure imbalance between the inside of the body and the outside atmosphere.

• Nitrogen narcosis: Altered mental status from breathing compressed air at depth

• Pulmonary overpressurization syndrome

(POPS, burst lung) can occur if a diver ascends too quickly.

Summary

• Pulmonary overpressurization syndrome may lead to arterial gas embolism.

• Barotrauma treatment depends on whether there is an air embolism. A pneumothorax may require needle decompression. With an air embolism, the patient must receive treatment in a hyperbaric chamber.

• In decompression sickness, nitrogen bubbles in blood and tissues during dive ascent.

Summary

• Shallow water blackout occurs when a person hyperventilates just before diving and passes out before resurfacing.

• The Divers Alert Network is a resource for diving-related injuries.

• Altitude illness occurs when unacclimatized people ascend to altitude, with types including AMS, HACE, and HAPE.

Summary

• Symptoms of AMS include headache and fatigue, weakness, gastrointestinal symptoms, dizziness, light-headedness, and difficulty sleeping.

• Symptoms of HACE include mental status changes and/or ataxia in a person with acute mountain sickness or the presence of both in a person without acute mountain sickness.

Summary

• Symptoms of HAPE include at least two of the following: dyspnea at rest, cough, weakness, or chest tightness or congestion, and at least two of the following: central cyanosis, audible rales, wheezing, tachypnea, or tachycardia.

• Treatment of altitude illness includes descending or use of a portable hyperbaric chamber, providing oxygen, and administering IV medications.

Summary

• Cardiopulmonary resuscitation should be started promptly for lightning strike victims.

• In lightning strike cases, victims who appear to be dead should be treated first.

• Anaphylactic reaction is the most frequent mortality cause from insect bites and envenomations.

Summary

• To decrease toxin exposure, promptly remove hymenoptera stingers or venom sacs.

• Fire ant stings may result in infection.

• Most snake bites in the United States are from pit vipers.

• If there are visible fang marks with no bleeding with a crotalid bite, it is likely a “dry bite ” with no venom.

Summary

• For scene safety, ensure the snake is dead, gone, or trapped in cases of envenomation.

• All significant snake envenomations require antivenin treatment.

• The most concerning spider bites are from the female black widow, the brown recluse, and the hobo spider.

• A small subset of patients with brown recluse spider bites may develop loxoscelism.

Summary

• Scorpion stings produce a neurotoxic reaction causing autonomic excitation.

• Scorpion sting treatment is largely supportive and includes airway protection.

• Tick bites can transmit serious illnesses and rarely cause life-threatening paralysis.

Credits

• Chapter opener : Courtesy of BM1 Kevin

Erwin/U.S. Coast Guard

• Backgrounds : Red – © Margo Harrison/

ShutterStock, Inc.; Green – Jones & Bartlett

Learning; Purple – Courtesy of Rhonda Beck;

Blue – Courtesy of Rhonda Beck.

• Unless otherwise indicated, all photographs and illustrations are under copyright of Jones & Bartlett

Learning, courtesy of Maryland Institute for

Emergency Medical Services Systems, or have been provided by the American Academy of

Orthopaedic Surgeons.

Chapter 38: Environmental Emergencies

Chapter 38

Environmental

Emergencies

Pathophysiology, Assessment, and Management of Heat Illness

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Chapter 38: Environmental Emergencies

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Pathophysiology, Assessment, and Management of Heat Illness

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