Heat Emergencies

Question 1

Controlled by the hypothalamus, the body maintains a core temperature between___________

Answer 1

36°C and 38°C

Question 2

Native thermal regulation mechanisms begin to fail at core temperatures of ________________

Answer 2

<35°C (<95°F) and >40°C (>104°F)

Question 3

Sharp increases in the rate of sweat production normally occur with core temperature elevations above ________

Answer 3

37°C

Question 4

the adaptation of the body to environmental changes

Answer 4

Acclimation

Question 5

In most individuals, acclimation can be achieved over _____________ to _______________.

Once removed from the hot environment, the body will de-acclimate to the original physiologic parameters within _____________.

Answer 5

7 days to several weeks

1 to 2 weeks

Question 6

Temperatures of _________ can produce cellular injury in hours

Answer 6

> 41.6°C (>106.9°F)

Question 7

__________________occurs during periods of high environmental heat stress.

Physical exertion is not required if the heat gain occurs at environmental temperatures and humidity levels that overwhelm the native heat loss mechanisms.

The increase in core temperature seen in this setting is often slow, occurring over a period of hours to days.

Because of this slow rise in heat burden, volume and electrolyte abnormalities are common.

Answer 7

Classic heat injury

Question 8

_________________ usually affects individuals who are participating in athletic events or performing jobs under conditions of high heat stress.

Risk factors include dehydration, concurrent illness, obesity, wearing too much clothing, and poor cardiovascular fitness.

In this setting, heat production and heat gain from the environment exceed the capacity of heat removal processes.

Answer 8

Exertional heat injury

Question 9

____________________ is the most common single source of internal heat production.

Answer 9

Physical exercise

Question 10

_________ ___ is the most common single source of internal heat production.

Answer 10

Physical exercise

Question 11

______________________ is a special category of nonexertional hyperpyrexia and can occur in several circumstances, such as when children are left inside cars, when stowaways are abandoned inside closed vehicles or railroad cars, and when workers are occupationally exposed to heat inside enclosed spaces.

Answer 11

Confinement hyperpyrexia

Question 12

_________________is a self-limited process manifested by mild swelling of the feet, ankles, and hands that appears within the first few days of exposure to a hot environment.

This is due to the cutaneous vasodilatation and orthostatic pooling of interstitial fluid in gravity-dependent extremities.

An increase in the secretion of aldosterone and antidiuretic hormone in response to the heat stress contributes to the mild edema.

This is found in elderly nonacclimatized individuals who are physically active after a period of sitting while traveling in a vehicle or airplane.

Answer 12

Heat edema

Question 13

Identify

Answer 13

Miliaria rubra (prickly heat)

Question 14

_____________ is a pruritic, maculopapular, and erythematous rash over normally clothed areas of the body.

It is an acute inflammation of the sweat ducts caused by blockage of the sweat pores by macerated stratum corneum.

The sweat ducts become dilated under pressure and ultimately rupture, producing superficial vesicles in the malpighian layer of the skin on a red base.

Itching is the predominant clinical feature during this phase and can be treated successfully with antihistamines.

Answer 14

Prickly heat

Also known as lichen tropicus, miliaria rubra, or heat rash

Question 15

With prolonged or repeated heat exposure, a keratin plug fills the sweat duct, causing obstruction in the stratum malpighian layer. When the duct ruptures a second time, the resultant vesicle will be driven deeper into the dermis. This vesicle simulates the white papules of piloerection and is not pruritic. This is known as the _________________________ and can readily advance into a chronic dermatitis.

Answer 15

profunda stage of prickly heat (miliaria profunda)

Question 16

________________ are painful, involuntary, spasmodic contractions of skeletal muscles, usually those of the calves, although they may involve the thighs and shoulders.

These usually occur in individuals who are sweating profusely and replace fluid losses with water or other hypotonic solutions.

Answer 16

Heat cramps

Question 17

pathogenesis of heat cramps

Answer 17

deficiency of sodium, potassium, or magnesium and fluid at muscle level.

Patients with severe heat cramps may have hyponatremia and hypochloremia

Question 18

Treatment of heat cramps

Answer 18

1. fluid and salt replacement (PO or IV)
2. rest in a cool environment.
3. For mild cases, a 0.1% to 0.2% saline solution can be given PO. Two 650-milligram salt tablets dissolved in a quart of water provide a 0.1% saline solution.
4. electrolyte solution drinks (sports drinks)
5. Patients with more severe symptoms require IV rehydration with normal saline.

Heat cramps can be prevented by maintaining adequate dietary salt intake or by drinking commercial electrolyte beverages

Question 19

part of the continuum of heat illness but does not meet criteria for heat stroke

can result from either water or sodium depletion, but is typically a combination of both

Water depletion tends to occur in the elderly and in persons working in hot environments with inadequate water replacement.

Answer 19

Heat stress

Question 20

Heat stress presents with symptoms

Answer 20

headache, nausea, vomiting, malaise, dizziness, and muscle cramps as well as signs of dehydration, such as tachycardia and orthostatic hypotension or near-syncope.

Question 21

True or false

Heat stress on physical examination, the temperature may be normal or elevated, usually not above 40°C (104°F)

Answer 21

True

Question 22

Heat stress treatment

Answer 22

1. volume and electrolyte replacement and rest
2. Removal from the heat-stressed environment
3. Patients with mild heat stress may be treated with oral electrolyte solutions.
4. Rapid infusion of moderate amounts of IV fluids (1 to 2 L of normal saline) may be necessary in patients who demonstrate significant tissue hypoperfusion. Ideally, the choice of IV solution should be guided by laboratory determinations, but isotonic salt solutions may be used until specific electrolyte abnormalities are identified.

In general, hospitalization is not required. Patients with congestive heart failure or severe electrolyte disturbances may require admission, because of the time needed to correct fluid and/or electrolyte deficits.

Question 23

True or false

Heat stress with an elevated temperature can progress to heat stroke even after the patient is removed from the hot environment. Therefore, patients with heat stress who do not respond to approximately 30 minutes of fluid replacement and removal from the hot environment should be cooled until the core temperature drops to ≤39°C (102°F). Patients should not be prematurely labeled as having heat stress without observation and reassessment.

Answer 23

True

Question 24

acute life-threatening emergency with high mortality and is fatal if left untreated.

Answer 24

Heat stroke

Question 25

The cardinal features of heat stroke are____________ and _______________

Answer 25

hyperthermia (>40°C [>104°F]) and altered mental status.

Question 26

Differential Diagnosis of Heat Stroke

Answer 26

Question 27

PREHOSPITAL CARE in HEAT STROKE

Answer 27

1. Remove the patient from the hot environment immediately
2. Perform standard resuscitation measures. Check point-of-care glucose if there is altered mental status.
3. Start cooling by
   A. removing clothing
   B. spray the patient with water
   C. provide airflow over the patient (ideal method but not always practical during transportation); D. place wet towels or sheets over the patient’s body; D. place ice on the patient
   E. Administer a bolus of normal saline (1 to 2 L) if hypotension is present.

Question 28

ED RESUSCITATION in HEAT STROKE

Answer 28

The goals of therapy are
1. immediate cooling
2. aggressive support of organ system function

Continue standard resuscitation measures.

1. Administer IV fluids at a rate that ensures adequate urine output.
2. In elderly patients or patients with cardiovascular disease, consider invasive monitoring. Check glucose levels. Monitor core temperature with an electronic rectal thermometer, temperature probe–equipped urinary drainage catheter, or esophageal thermometer.

Question 29

With all cooling methods, the goal is to reduce the core temperature to approximately________ and to avoid overshoot hypothermia.

Answer 29

39°C (102.2°F)

Question 30

How does Evaporative Cooling work?

Answer 30

1. Remove patient clothing
2. spray cool water (∼15°C [59°F]) on most of the patient’s body surface.
3. Directing a fan over the patient facilitates evaporation.

If the skin temperature is reduced <30°C (86°F), shivering will result in more heat production, and peripheral vasoconstriction will impair evaporation.

To prevent hypothermic overshoot, some recommend using either tepid water warmed to 40°C (104°F) or exposing the patient to hot air (45°C [113°F]) with the fan.

Question 31

two main difficulties associated with evaporative cooling are _________ and _____________

How do you manage?

Answer 31

shivering and the inability of cardiac electrodes to adhere to the skin.

Management:
Shivering : short-acting benzodiazepines and phenothiazines.

Phenothiazines may
A. lower the seizure threshold
B. cause hypotension
C. impair sweating from anticholinergic properties

Question 32

Immersion cooling is performed by

Answer 32

placing the undressed patient into a tub of ice water deep enough to cover the trunk and extremities, while keeping the patient’s head out of the water

Question 33

The most rapid method of cooling a heat stroke victim is

Answer 33

cardiopulmonary bypass