128 Hypothermia, Frostbite and Nonfreezing Cold Injuries Flashcards
Hypothermia defn
temp <35 celcius
What variables contribute accidental hypothermia?
exposure
old age
poor health
inadequate nutrition
meds and intoxicants
Compensatory responses to heat loss x4
convection
conduction
radiation
evaporation
Cold stress increases preshivering muscle tone, potentially __ heat production
doubling
How long does heat production from shivering last?
only few hours due to glycogen depletion and fatigue
Shivering thermogenesis: how much does this increase BMR?
up to 5x which rapidly incr o2 consumption
What part of the CNS modulates shivering?
posterior hypothalamus and sc
What part of the CNS is in charge of nonshivering heat conservation and dissipation?
preoptic anterior hypothalamus
MC causes of accidental hypothermia
convective heat loss to cold air
conduction and convection in cold water
5 ways heat loss occurs?
radiation
conduction
convection
respiration
evaporation
How much does wet clothing increase heat loss?
3-5x
Greater losses of cutaneous and respiratory heat in which kind of environments?
cool
dry windy
When there is no sweating, how is more heat lost?
radiation
convection
When the core temp is between 30 to 37, what mechanisms generates heat?
vasoconstriction
shivering
nonshivering basal and endocrine thermogenesis
When does shivering tend to stop ? (temp range)
30 to 24
BMR decr
At temp below 24, what happens to autonomic and endocrine mechanisms of heat conservation?
inactive
MC heart rhythm in hypothermia?
bradycardia
Cold stress - temp 37-35 - what are the characteristics of this you will see in a patient?
shivering
incr metabolism
Mild hypothermia: Temp 35 to >32 - what are the characteristics of this you will see in a patient
increased shivering and thermogenesis
incr BMR
normal bp
max resp stimulation
ataxia
apathy
amnesia
Moderate hypothermia: Temp 32 to 29 - what are the characteristics of this you will see in a patient
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
Severe hypothermia: temp 28 to 19
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
What is an osborn J wave?
junction of QRS and ST segment
J waves are normally upright in aVL, aVF, and the left precordial leads
What conditions other than hypothermia can a J wave be seen in ?
cardiac ischemia
sepsis
cns lesion
hypocalcemia
What arrh are mc in mod-sev hypothermia?
atrial and vent dysrh
prolonging of cardi cycle - PR prolong, qrs, qtc