128 Hypothermia, Frostbite and Nonfreezing Cold Injuries

Question 1

Hypothermia defn

Answer 1

temp <35 celcius

Question 2

What variables contribute accidental hypothermia?

Answer 2

exposure
old age
poor health
inadequate nutrition
meds and intoxicants

Question 3

Compensatory responses to heat loss x4

Answer 3

convection
conduction
radiation
evaporation

Question 4

Cold stress increases preshivering muscle tone, potentially __ heat production

Answer 4

doubling

Question 5

How long does heat production from shivering last?

Answer 5

only few hours due to glycogen depletion and fatigue

Question 6

Shivering thermogenesis: how much does this increase BMR?

Answer 6

up to 5x which rapidly incr o2 consumption

Question 7

What part of the CNS modulates shivering?

Answer 7

posterior hypothalamus and sc

Question 8

What part of the CNS is in charge of nonshivering heat conservation and dissipation?

Answer 8

preoptic anterior hypothalamus

Question 9

MC causes of accidental hypothermia

Answer 9

convective heat loss to cold air

conduction and convection in cold water

Question 10

5 ways heat loss occurs?

Answer 10

radiation
conduction
convection
respiration
evaporation

Question 11

How much does wet clothing increase heat loss?

Answer 11

3-5x

Question 12

Greater losses of cutaneous and respiratory heat in which kind of environments?

Answer 12

cool
dry windy

Question 13

When there is no sweating, how is more heat lost?

Answer 13

radiation
convection

Question 14

When the core temp is between 30 to 37, what mechanisms generates heat?

Answer 14

vasoconstriction
shivering
nonshivering basal and endocrine thermogenesis

Question 15

When does shivering tend to stop ? (temp range)

Answer 15

30 to 24

BMR decr

Question 16

At temp below 24, what happens to autonomic and endocrine mechanisms of heat conservation?

Answer 16

inactive

Question 17

MC heart rhythm in hypothermia?

Answer 17

bradycardia

Question 18

Cold stress - temp 37-35 - what are the characteristics of this you will see in a patient?

Answer 18

shivering
incr metabolism

Question 19

Mild hypothermia: Temp 35 to >32 - what are the characteristics of this you will see in a patient

Answer 19

increased shivering and thermogenesis
incr BMR
normal bp
max resp stimulation
ataxia
apathy
amnesia

Question 20

Moderate hypothermia: Temp 32 to 29 - what are the characteristics of this you will see in a patient

Answer 20

stupor with a 25% decr in o2 consumption
incr shivering thermogenesis
atrial fib/dysrhythmias, poikilothermia, pulse and cardiac output 2/3 of N, insulin ineffective, progressive decrease in consciousness and LOC can be seen

Question 21

Severe hypothermia: temp 28 to 19

Answer 21

vent fib susceptible with 50% decr in o2 consuption and pulse

loss reflexes

major a-b differences, no reflex or response to pain

cerebral blood flow 1/3 normal, co 45% normal, pulmonary edema possible to develop

no corneal or oculocephalic reflex

at 22 -max risk of vfib and 75% o2 consumption

at 20 lowest resuption of cardiac electromech activity, 20% of normal

at 19 flat ecg

Question 22

What is an osborn J wave?

Answer 22

junction of QRS and ST segment

J waves are normally upright in aVL, aVF, and the left precordial leads

Question 23

What conditions other than hypothermia can a J wave be seen in ?

Answer 23

cardiac ischemia
sepsis
cns lesion
hypocalcemia

Question 24

What arrh are mc in mod-sev hypothermia?

Answer 24

atrial and vent dysrh

prolonging of cardi cycle - PR prolong, qrs, qtc

Question 25

At less than what temp is afib common?

Answer 25

<32

Question 26

Core temp afterdrop - what is this?

Answer 26

decr in individual’s core temp after removal from the cold

contribution of equilibriation core cool to periphery and countercurrent cooling of blood to cold tisues in periphery before reurning to warm = greater effect

Question 27

At what temp of hypothermia do we see cns alterations?

Answer 27

33.5

Question 28

Renal system changes when faced with hypothermia

Answer 28

diuresis
dilute, does not clear nitrogenous waste

Question 29

Hypothermia and the resp system - what happens?

Answer 29

initially stimulates incr RR
then decr in minute vol (decr 50% with an 8 deg decr in temp)

can cause acidosis with rentension, hypercapnia

viscous bronchorrhea, decr ciliary motility, noncardiogenic pulmonary edema

Question 30

What 4 categories may include factors predisposing someone to hyperthermia?

Answer 30

1. decr heat production
2. impaired thermogenesis
3. miscell assoc clinical syndromes
4. impaired thermoregulation

Question 31

8 examples of decreased heat production

Answer 31

endocr failure
hypopituitarism
hypothyroid
diabetes
hypoglycemia
age extremes
inactivity
nalnutrition

Question 32

8 examples of incr heat loss

Answer 32

environmental
immersion
nonimmersion
induced vasodilation
pharmacologic
toxicoloic
burns
psoriasis
cold infusions
iatrogenic

Question 33

8 examples of impaired thermoregulation predisposing to hypothermia

Answer 33

diabetes
cns failure
cva
toxicologic
metabolic
hypothalamic dysfunc
parkinson
anorexia
neoplasm
MS

Question 34

8 predisposing factors to hypothermia under miscellanous conditions category

Answer 34

recurrent hypothermia
sepsis
pancreatitis
carcinomatosis
uremia
vascular insuff
sarcoidosis
GCA
paget’s disease
hodgkin disease

Question 35

How does ethanol effect hypothermia?

Answer 35

etoh metabolized slowly in hypothermia
directly suppresses activity of posterior hypothalamus and mamillary bodies
decr vasodilation and shivering

Question 36

What medication classes can impair thermoregulation leading to hypothermia?

Answer 36

antidepressants
mood stabilizers
antipsychotics
anxiolytics
general anesthesia
OD: organophosphates, opioids, sedatives, barbituates, co

Question 37

Abnormal plasma osmolality may cause hypothalamic dysfunction - examples?

Answer 37

uremia
lactic acidosis
dka
hypoglycemia

Question 38

Major RF of hypothermia in trauma pt

Answer 38

extremes of age
severe injury intoxication
large transfusion requirements
prolonged field, ED, operating room times

Question 39

What is paradoxical undressing?

Answer 39

widely reported in hypothermic pt - related to periheral vasoconstrictive changes of hypothermia (final preterminal effort)

Question 40

Above 22 degrees, it should be assumed that nonreactive dilated pupils are more likely related to…

Answer 40

inadq tissue perfusion as opposed to hypothermia

Question 41

*Neuromuscular examination may reveal stiff posture, pseudo– rigor mortis, or opisthotonos. Reflexes are usually hyperactive to 32°C (89.6°F) and then become hypoactive, disappearing around 26°C (78.8°F). Cremasteric reflexes are absent because the testicles are already retracted. The plantar response usually remains flexor until 26°C (78.8°F). The knee jerk reflex is the last reflex to disappear and the first to reappear with rewarming. Diagnosis of CNS disorders, includ- ing spinal cord lesions, may be obscured by hypothermia. From 30°C to 26°C (86°F to 78.8°F), both contraction and relaxation phases of the reflexes are equally prolonged. If intact, the ankle jerk is helpful to diag- nose hypothermic myxedema. Myxedema characteristically prolongs the relaxation phase more than the contraction phase.

Answer 41

-

Question 42

ddx