129. Heat illness Flashcards
1
Q
Name 4 groups of people at risk for heat related illness
A
older adults
low SES/income
reexisting disease
children
people who exert themselves (american football, military, athletes)
2
Q
In the absence of cooling mechanisms, how much would your baseline metaboolic activity increase per hour?
A
1.1 c/2 deg F hourly
3
Q
What are the 4 ways in which your body dissipates heat?
A
conduction
convection
radiation
evaporation
4
Q
Describe conduction
A
transfer of heat warmer to cooler objects by direct physical contact
5
Q
Describe convection
A
heat loss to air and water vapor molecules circulating around the body
6
Q
Describe radiation
A
Heat transfer by electromagnetic waves
7
Q
Describe evaporation
A
conversion of liquid to gas phase
8
Q
What is the principle method of heat loss during exercise?
A
evaporation
9
Q
What are the three key regulators of body temperature?
A
thermosensors (peripheral, central)
central integrative area (CNS)
thermoregulatory effectors - sweating, peripheral vasodilation
10
Q
What are the two kinds of sweat glands humans possess?
A
apocrine
eccrine
11
Q
Where are apocrine sweat glands
A
- axillae
- adrenergically innervated and respond to emotional stress as well as to heat. Most glands producing so-called thermal sweat are eccrine glands.
- These are cholinergically innervated and distributed over the entire body, with the largest num- ber on the palms and soles.
12
Q
What is eccrine sweat?
A
Eccrine sweat is colorless, odorless, and devoid of protein.
- Individuals exercising in hot environments com- monly lose 1 or 2 L/h of sweat.
- A loss of up to 4 L/h is possible with strenuous exercise.
13
Q
As humidity increases, evaporative heat loss …
A
becomes non-existent
14
Q
Describe the vascular response to heat regulation
A
- cutaneous vasodilation
-compensatory vasoconstriction of splanchnic and renal beds
to do this, BP must +++ increase
15
Q
Daily exposure to work and heat for ___ min/day results in acclimatization within 7-14 days
A
100
16
Q
Define acclimatization
A
constellation of physiologic adaptations that occur in a normal person as the result of repeated exposures to heat stress.
17
Q
How does the cardiovascular system acclimatize?
A
HR lower
higher SV
18
Q
How does aldosterone change in acclimatization
A
earlier release
then over time generate lower level during ex heat stress
19
Q
How does total body K change in acclimatization ?
A
depletion of up to 20% or 500mEq by second week of acclimatization
20
Q
List 5 RF for heatstroke
A
older adult
psych conditions
chronic disease - CF, burns, scleroderma, ectodermal dysplasia
obesity
“certain meds” per Rosen’s - beta blockers, CCB, diuretic, anticholinergic meds
21
Q
What is the most critical variable in decreasing exertional heat stroke?
A
fluid intake/dehydration
22
Q
The goal of fluid consumption is the maximize voluntary intake and gastric emptying - what fluid vol and temp does this?
A
large 500-600ml
cool (10-15.8 deg)
23
Q
An athlete with a loss of 2% to 3% body weight (1.5 to 2 L in a 70-kg man) should drink extra fluid and be permitted to compete only when his or her body weight is within ____ of the starting weight on the previous day.
A
0.5 to 1 kg (1 or 2 pounds)
24
Q
What are signs of mod-severe dehydration and weight loss of 5-6%?
A
intense thirst, scant dark-colored urine, tachycardia, and increase in rectal temperature of approximately 2°C (3.6°F)
25
What is an appropriate salt diet for successful adaptation for work in heat? (per Rosen's_
A 6-g sodium diet is sufficient for successful adaptation for work in the heat, with sweat losses averaging 7 L/day. Excessively high salt intake in relation to salt losses in sweat during initial heat exposure can impair acclimatization because of the inhibition of aldosterone secretion. Excessive salt ingestion can also exacerbate potassium depletion.
26
what are recommendations to increase evaporative cooling?
loose fitting/ventilated
light colored
27
Describe the wet bulb globe temperature heat index (as a concept), what temperature this is considered concerning for healthy people and what temp should avoid ex/strenuous work?
measures effects of T, humidity and radiant thermal E from sun
>25 deg C wet bulb = even healthy people high risk. >28 - avoid ex and strenuous work
28
Describe wet bulb globe temperature: what is the equation and its variables?
WBGT=0.7 Tn +0.2 Tg +Ta
Tn = “Natural” wet bulb temperature—the temperature achieved by a ther- mometer covered with a moistened white wick and left exposed to the ambient environment
Tg = Globe temperature—the temperature inside a blackened hollow copper sphere exposed to the ambient environment
Ta = Ambient temperature
These measurements can be done manually or calculated automatically with
the help of computer algorithms.
29
Why is it important to distinguish between feve and hyperpyrexia?
fever is not damaging whereas in hyperpyrexia, person needs to be cooled actively and passively to prevent damage and antipyretics are not recommended
30
What is miliaria rubra?
"heat rash"
blocked sweat bland pores by broken down stratum corneum and secondary staph infection
31
What are the clinical features of Miliaria rubra?
itchy vesicles on erythematous base
confined to clothed areas
typically anhidtrotic area
can get a week later, deeper vesicle in dermis (profunda stage) - moreso now white papules, not itchy
32
DDX Miliaria rubra
contact dermatitis
cellulitis
allergic reaction
33
Management of Miliaria rubra
- light, loose fitting clean clothes
-avoid cont sweat
- gentle exfoliation may help, no soap
- topical hydrocortisone 2.5% or triamcinolone 0.1% BID 1-2 weeks may help itchy only
34
What are heat cramps?
Cramps of most worked muscles
Usually occur after exertion
Copious sweating during exertion
Copious hypotonic fluid replacement during exertion
Hyperventilation not present in cool environment
35
How do you differentiate heat cramps from hyperventilation tetany?
hyperv tetabt : + carpopedal spasm and paresthesias in distal extremities and perioral area
36
Labs for heat cramps
maybe hyponatremic, hypochloremic
37
Heat cramp tx
salt solution - 0.1-0.2% salt solution (2-4 10 grain salt tabs in 1 quart of water) = improvement
NOT salt tabs as they just bug your belly, delay gastric emptying
38
Why does heat edema occur?
hydrostatic pressure, vasodilation of cutaneous vessels, with orthostatic pooling --> vascular leak, accumulation of interstitial fluid in lower extremities
also aldosterone level incr in response to heat stress
39
DDx heat edema
HF
liver disease
neprhosis
LE infection
DVT
40
Management of heat edema
leg elevation
thigh high support hose
41
Heat syncope - why does this occur?
vasodilation means for blood flow to cutaneous vessels, increasing vascular volume at expense of thoracic so inadequate central venous retrun, drop in CO, and cerebral pefusion --> syncope
42
Recommendations to prevent heat syncope
move around often, flex leg muscles repeatedly when standing sta- tionary, avoid protracted standing in hot environments, and assume a sitting or horizontal position when prodromal warning symptoms or signs occur.
43
What is the definition of heat exhaustion?
clinical syndrome defined by vol depletion occuring under heat stress
- water depletion
- salt depletion
44
Heat exhaustion symptoms
weakness, fatigue, frontal headache, impaired judgment, vertigo, nausea and vomiting and, occasionally, muscle cramps (Box 129.3). Orthostatic dizziness and syncope can occur. Sweating persists and may be profuse. The core temperature is only moderately elevated, usually below 40°C (104°F). Signs of severe CNS dysfunction (e.g., altered mental status) are not present.
45
List 6 factors required for diagnosis of heat stroke
* Vague malaise, fatigue, headache
* Core temperature often normal; if elevated, <40°C (104°F)
* Mental function essentially intact; no coma or seizures
* Tachycardia, orthostatic hypotension, clinical dehydration (may occur)
* Other major illness ruled out
* If in doubt, treat as heatstroke.
46
Management of heat exhaustion
Rest
Cool environment
Assessment of volume status—orthostatic changes, blood urea nitrogen
level, hematocrit, serum sodium concentration
Fluid replacement—normal saline to replete volume if the patient is ortho-
static; replace free water deficits slowly to avoid cerebral edema.
Healthy young patients are usually treated as outpatients; consider admission if the patient is older, has significant electrolyte abnormalities, or would be
at risk for recurrence if discharged.
47
What diagnostic tests can you do for heat exhaustion?
hyponatremia
hypochloremia
low urinary Na and Cl
CK and renal function, AST+ALT can be helpful
48
Recommendations for heat exhaustion outpatient tx
Young, otherwise healthy patients who do not have significant lab- oratory abnormalities and who respond rapidly to hydration do not require hospitalization. These patients should be instructed to drink plenty of fluids and avoid heat stress for 24 to 48 hours.
Older patients, particularly those with cardiovascular disease or other chronic dis- eases, may benefit from more cautious inpatient fluid and electrolyte replacement and frequent reassessmen
49
What is heat stroke?
BAD
life threatening emergency when homeostatic thermoregulatory mechanics fail to regulate body temp
50
Why is heat stroke bad? List body system issues
1. Neuro
tissue damage due to high temps
Cerebral edema
petechiae in third and fourth ventricles
cerebellar Purkinje cell damage
LT motor/cerebellar/cognitive changes may persist
--> ongoing = increased ICP
2. Cardiovascular
Circulatory failure
3. Abdo
- vasoconstriction of splanchnic and renal vasculature to try to increase skin blood flow --> splanchnic and renal ischemia (hence GI sx)
- hepatic damage ++++ common
51
Heatstroke diagnosis per Rosen's box 129.5
* Exposure to heat stress, endogenous or exogenous
*Signs of sever CNS dysfunction - coma, seizure, delirium
* Core temperature usually >40.5°C (105°F), but may be lower
* Hot skin common, and sweating may persist
* Marked elevation of hepatic transaminase levels
52
Name 5 characteristics of exertional vs classic heatstroke
Exert:
yo
during ex
sporadic
with diaphoresis
hypioglycemia
DIC
rhabdo
acute renal failure
marked lactic acidosis
hypocalcemia
Classic:
predispoing factor, meds
older
sedentary
heat wave occurrence
anhidrosis
normal BG
mild coagulopathy
mild CK rise
oliguria
mild acidosis
normocalcemia
53
DDX for heat stroke - list 8
CNS hemorrhage
meningitis, encephalitis
thyroid storm
drug induced ( anticholinergic meds *pupillary differences, etoh withdrawal, stimulant use or sympathomimetic, aspirin or clopidogrel OD, ephedra, antipsychotic)
ex induced hypoNa
NMS
serotonin syndrome
high fever and sepsis
54
Triad of serotonin syndrome
mental status change
autonomic hyperactivity
NM abnormality
55
What type of temp measurement should be done for heat stroke dx?
rectal
56
Diagnostic tests for heat stroke
ABG
cbc for plt and r/o wbc
liver AST, ALT
ext electrolyte anel
glucose
BUN
cr
trop
BG
CK and myoglobin
urinalysis - protein in urine, granular cast, RBC
PTT, INR, fibrin degradation products
LDH
57
When should liver transaminases, LDH be repeated?
within 24h
58
List 5 cooling mechanism in heat stroke
Preferred:
Evaporative cooling with large circulating fans and skin wetting (clothes off)
Ice water immersion
Adjuncts:
Ice packs to axillae and groin, neck
Cooling blanket
Peritoneal lavage (unproven efficacy in humans)
Rectal lavage
Gastric lavage
Cardiopulmonary bypass
59
Immersion in ice water for heat stroke - what time frame should they decrease to below 39 deg body temp?
10-40 min
60
If a patient becomes tachycardic in heat stroke and you think about electrical cardioversion, what should you do?
WAIT
myocardium not cooled yet
avoid NE due to vasoconstriuction promotion without improvement of CO, perfusion, decrease cutaneous heat exchange and may just worsen the gut ischemia
61
How do salicylates make heat stroke worse?
uncoupling oxidative phosphorylation
aggravating coagulopathies
62
If rhabdo is present in heat stroke, what rate of urine output is recommended?
>/= 2ml/kg/h
63
When in heat stroke should you consider urinary alkalinazation ph >6.5?
acidemia
dehydration
underlying renal disease
64
Tx of choice for shivering in heat stroke cooling modalities
benzos IV
65
If DIC occurs in heat stroke, how to manage?
same- FFP, plt, monitor
66
1. An 18-year-old female marathon runner presents to the medical aid station during a hot summer race. She is extremely irritable and diaphoretic. She is complaining of generalized weakness, diz- ziness, nausea, and headache. The physical examination reveals an oral temperature of 40.5°C (105°F), heart rate of 120 beats/min, muscle twitching, and ataxia. What is the most appropriate man- agement?
a. Assess her volume status and immediately start normal saline to replete volume loss before transfer to a hospital.
b. Encourage her to drink cold water to replace her free water defi- cit rapidly.
c. Immediately remove her from the hot environment and begin cooling before transfer to a hospital.
d. Prescribe immediate rest, after which she may be allowed to fin- ish the race.
c
67
2. Which of the following statements regarding heat exhaustion is true?
a. It causes body temperatures that often exceed 40.5°C (105°F).
b. It only exists in two discrete forms, either salt depletion or water
depletion.
c. It is associated with systemic symptoms.
d. It is characterized by hyponatremia and hyperchloremia. e. It occurs when muscles are fatigued by heavy work.
Answer: c. Heat exhaustion is a clinical syndrome. Whereas there are typically two types of heat exhaustion, water depletion and salt deple- tion, pure forms of either type are rare. Most cases of heat exhaus- tion involve mixed salt and water depletion. In salt depletion heat exhaustion, the syndrome is characterized by hyponatremia, hypo- chloremia, and low urinary sodium and chloride concentrations. The symptoms and signs associated are variable and nonspecific but usually systemic, such as weakness, fatigue, frontal headache, vertigo, nausea, and vomiting. The body temperature usually remains nearly normal.
c
68
3. Despite cooling measures, poor outcomes are seen in heatstroke patients with which of the following?
a. Altered coagulation status
b. History of schizophrenia
c. Need for supplemental oxygen
d. Presentation with acute renal failure
e. Presentation with acute rhabdomyolysis
a
69
4. The usual characteristics of classic heatstroke include which of the following?
a. Diaphoresis
b. Disseminated intravascular coagulation c. Hypoglycemia
d. Marked lactic acidosis
e. Usual occurrence during heat waves
e
70
5. Which of the following is associated with heat cramps? a. Excessive salt intake
b. Drinking copious amounts of hypertonic fluids
c. Carpopedal spasms with distal extremity paresthesias d. Hyponatremia and hypochloremia
e. Rhabdomyolysis
d
