Heat Related Injury and Illness

Question 1

The 4 ways the body dissipates heat

Answer 1

1. Radiation (infared rays)
2. Convection (air/water across skin)
3. Conduction (physical Contact)
4. Evaporation (Sweat)

Question 2

Pathophysiology of a Fever

Answer 2

Temperature elevation due to activity of the hypothalamus, in response to cytokines triggered by infection or sterile inflammation

Question 3

Pathophysiology of Hyperthermia

Answer 3

Temperature elevation due to uncontrolled heat generation (i.e. muscular hyperactivity), which can generate temperatures higher than a fever, with greater risk of thermal injury to tissues.
Unlike fever, hyperthermia involves complete loss of thermal control

Question 4

Does Fever or Hyperthermia involve complete loss of thermal control?

Answer 4

Hyperthermia

Question 5

As body temp incr, skin sensors and warm blood stimulates the anterior hypothalamus, which stimulates ….

Answer 5

• Vasodilatation
• Increased Cardiac Output
• Increased Respiratory Rate
• Increased Sweat Production

Question 6

as temp incr above ____, most heat loss occurs thru sweating.

Answer 6

95F

Question 7

As relative humidity incr above ____%, sweating becomes ineffective

Answer 7

75%

bc moisture on skin cannt transfer into air bc theres not enough of a humidity difference b/w skin and air

Question 8

Factors contributing to incr heat illness danger

Answer 8

• High heat
• high humidity
• lack of wind

Question 9

Types of heat illness

Answer 9

• Heat cramps
• Heat exhaustion
• Heat stroke

Question 10

Heat cramps

Answer 10

• painful, involuntary spasmodic muscle cramps that occur in heavily exercised muscles in hot and humid environments
• mildest form of heat injury
• ET: e- imbalance

Question 11

Do heat cramps results in hyper or hyponatremia?

Answer 11

hyponatremia bc you sweat and replace water but not salt

Question 12

Typical body temp during muscle cramps?

Answer 12

norm, body is still thermoregulating

Question 13

Heat cramps trmnt

Answer 13

• firm passive muscle stretching (ankel dorsiflexion for calf cramp)
• rest in cool space
• Oral fluids (1-2L water with 2 tsp salt)

Question 14

When to seek immediate attention for heat cramps?

Answer 14

• Cramps cannot be controlled
• Insufficient fluid intake due to nausea/vomiting
• Significant weakness
• Profuse sweating not controlled in air-conditioned environment
• May have in addition to heat exhaustion or heat stroke

Question 15

Heat exhaustion can very quickly lead to ______ if not treated ASAP

Answer 15

heat stroke

Question 16

Heat exhaustion is determined by a core temp >______

Answer 16

An illness resulting from prolonged, heavy activity in a hot environment with subsequent dehydration, electrolyte depletion, and rectal temperature 37.8 °C - 40 °C (100 °F - 104 °F)

Question 17

Heat stroke is determined by a core temp >_____

Answer 17

A life-threatening heat illness characterized by extreme hyperthermia (core temperature >40 °C [104.0 °F]), dehydration, and neurologic manifestations

Question 18

Which two types of heat illness are thermoregulation issues?

Answer 18

Heat exhaustion and heat stroke

Question 19

Which heat illness is due to electrolyte abnorm?

Answer 19

Heat cramps

Question 20

Heat exhaustion vs heat stroke (SS & trmnt)

Answer 20

Question 21

Exertional vs Non-exertional heat stroke

Answer 21

• Exertional = Young althete on the field for too long
• Non-exertional = old women watching the game in the shade

Question 22

Meds that impair heat dissipation (risks for elderly)

Answer 22

phenothiazines, anticholinergics, antihistamines, beta-blockers

• Anticholinergic properties (atropine)
• Antiepileptic (topiramate)
• Antihistamines
• Glutethimide (Doriden)
• Phenothiazines
• Tricyclic antidepressants
• Amphetamines, cocaine, “ecstasy”
• Ergogenic stimulants (e.g., ephedrine, ephedra)
• Lithium
• Diuretics
• β-Blockers
• Ethanol

Question 23

Predisposing factors for heat illness (not due to illness)

Answer 23

Lack of acclimatization
Low physical fitness
Excessive body weight
Dehydration
Advanced age
Young age

Question 24

Predisposing factors for heat illness (medical co-morbidities)

Answer 24

• Inflammation and fever
• Viral infection
• Cardiovascular disease
• Diabetes mellitus
• Gastroenteritis
• Rash, sunburn, and previous burns to large areas of skin
• Seizures
• Thyroid storm
• Neuroleptic malignant syndrome
• Malignant hyperthermia
• Sickle cell trait
• Cystic fibrosis
• Spinal cord injury

Question 25

Heat exhaustion or stroke?

• Generalized malaise, weakness, headache, muscle and abdominal cramps, nausea, vomiting, hypotension, tachycardia.
• Rectal temperature is usually normal.
• Sweating is usually present.

Answer 25

exhaustion

Question 26

Heat exhaustion or stroke?

• Neurologic manifestations (seizures, tremor, hemiplegia, coma, psychosis, other bizarre behavior)
• Evidence of dehydration (poor skin turgor, sunken eyeballs)
• Tachycardia, hyperventilation
• Skin is hot, red, and flushed
• Sweating is often (not always) absent, particularly in elderly patients

Answer 26

stroke

Question 27

why are kids under 4 and elderly over 65yo at higher risk for heat illness?

Answer 27

kids CNS is not fully developed and cant thermoregulate as well
Elderly ppl have deterioating CNS

Question 28

Which labs can differentiate b/w heat exhaustion and stroke?

Answer 28

Mild or absent increases in heat exhaustion:
creatine phosphokinase (CPK)
aspartate aminotransferase (AST)
lactate dehydrogenase (LDH)
alanine aminotransferase (ALT)

Question 29

Possible lab abnormalities for heat exhaustion and stroke

Answer 29

• HIGH BUN, creatinine, hematocrit
• Hypo/hypernatremia, hyper/hypoK+
• HIGH LDH, AST, ALT, CPK, Bilirubin
• Lactic acidosis, resp alkalosis (hyperventilation)
• Myoglobinuria, hypofibrinogenemia, fibrinolysis, hypocalcemia

Question 30

Heat exhaustion trmnt

Answer 30

• get out of the heat
• fluids 2L q4hr
• salt replacement (1/4 tsp salt in 1L water)
• if IV fluids if unable to drink

Question 31

IV Fluids for heat exhaustion?

Answer 31

• young athletes -> NS IV (3-4L over 6-8hrs)
• elderly patients -> consider using D5½NS IV with the rate titrated to cardiovascular status.

Question 32

Heat stroke trmnt

Answer 32

• rapid cooling
• rmv clothes
• if unconscious -> roll pt on their side
• protect airway and give nasal O2 at 4L/min to keep SatO2 >90%
• Monitor body temp q 5min (rectal temp goal: 38C (102.2F) within 30-60min)
• Stop active cooling when 38-39 °C to prevent overcooling
• Continue monitoring for thermal instability for up to 6 hours

Question 33

The goal of active cooling is to drop the temp down to ________ within ______min

Answer 33

38C (102.2F) within 30-60min

Stop once this is reached to prevent overcooling

Question 34

Monitor body temp q ____min

Answer 34

5

Question 35

Ways to cool a person with heat stroke?

Answer 35

• spray bottle + fan
• immersion in tepid water (15C, 59F) is preferred over ice immersion to minimize risk of shivering
• ice bath (more effective than other intrusive options like ice cold stomach lavage)

Question 36

Why should you NOT cool a person by puting ice packs on their bare skin (axilla, neck, groin)

Answer 36

they increase peripheral vasoconstriction and may induce shivering.

Question 37

Why are antipyretics ineffective at cooling a person with heat stroke?

Answer 37

the hypothalamic set point during heat stroke is normal despite the increased body temperature.
Antipyretics are agents that try to decrease a fever by telling the hypothalamus to decrease the set body temperature.
Trying to turn the temperature down won’t do anything if the room is on fire

Question 38

Why are Arctic sun (cooling pads) not preferred to cool a person with heat stroke?

Answer 38

not quick enough

Question 39

Why should vasopressors be avoided if possible in pt with heat stroke?

Answer 39

may cause cutaneous vasoconstriction which impairs heat release

Question 40

management of heat stroke

Answer 40

• Intubate a comatose patient, or one with extreme rigidity, or in status epilepticus
• Otherwise, nasal O2
• Insert Foley catheter
• Continuous ECG monitoring is recommended.
• Insert at least two large-bore IV lines and begin IV hydration with normal saline (NS) or Lactated Ringer.
• Draw initial laboratory studies: Electrolytes, complete blood count, blood urea nitrogen, creatinine, AST, ALT, CPK, LDH, glucose, PT (INR), PTT, platelet count, Ca2+, lactic acid, Coag profile, and arterial blood gases.

Question 41

Hyperthermia complications

Answer 41

• Rhabdomyolysis
• Acute hepatic failure (rarely leading to fulminant failure requiring transplantation)
• Seizure
• Aspiration pneumonia -> ARDS
• Stress-induced cardiomyopathy
• Disseminated Intravascular Coagulation (DIC)
• Hypoglycemia
• Hyponatremia (likely hypernatremic if dehydrated)

Question 42

Heat stroke complication trmnts

Hypotension

Answer 42

Vigorous hydration with normal saline or Ringer lactate

Question 43

Heat stroke complication trmnts

Shivering

Answer 43

• Benzodiazepines, muscle relaxation and anti-seizure effects
• Ketamine, help control agitation
• Opioids, treat pain if source of agitation (avoid fentanyl if concerned of serotonin syndrome)
• Magnesium
• Buspirone 30mg PO

Caution, these can decr resp drive (especiially opiates). if you have to use, knock them out and intubate

Question 44

Heat stroke complication trmnts

Acidosis

Answer 44

Use bicarbonate judiciously (only in severe acidosis)

usu you just treat the underlying ET

Question 45

Heat stroke complications

Rhabdomyoloysis is a concern for ____

Answer 45

compartment syndrome

Question 46

heat stroke prognosis

Answer 46

• Most patients recover completely within 48 hr.
• Central nervous system injury is permanent in 20% of cases.
• Mortality rate can exceed 30% in patients with prolonged and severe hyperthermia.
• Delayed access to cooling is the leading cause of morbidity and mortality in persons with heat stroke.

Question 47

heat stroke complications trmnt

Agitation

Answer 47

Low-dose ketamine