Download Hypothermia in the elderly - South African Family Practice

Hypothermia
in the elderly
Even in moderate climates, geriatric patients are
vulnerableto accidental hypothermia - and the condition
mimics many other disorders.
Bg RE Carlson, MD and PJ Hering, MD
1 f someone told you that he or she
Ihad just diagnosed a patient with
"accidentalhypothermia," you might
immediatelypicture an alcoholicwho
had passedout in a snowbank during
a drunken stupor and sustained frostbite of the extremities and a
decreased core temperature.
Until fairly recently, alcoholics
were the group at greatest risk in the
US for accidential hypothermia;
becausealcohol is a vasodilator,central nervous system depressant, and
anaesthetic, it can cause hypoglycemia and increasethe risk of trauma
and exposure.
Today, however, the hypothermic
patient is more likely to be that
elderly teetotaling, fixed-income
patient on medications for hypertension. diabetes. or emotional
problems whom you just saw in your
office a few weeks ago for a routine
follow-up visit.
Prolonged exposure to temPeratures as high as 16C to l BC (6OF to
63F) can trigger hgpothermia in
geriatric patients. 1
You needn't practise in an area
with an extremely cold climate to see
accidental hypothermia in the
elderly.
Often, it occurs in people who
simply live in chilly apartments or do
- May 1982
FamilyPractice
not use heaters in order to save
money.
preoptic anterior hypothalamus
(Figure 1). The neural network,
via the autonomic nervous
Normalthermoregulation sacting
ystem, rapidly controls heat
To understand how accidental dissipation.
hypothermia occurs, it's helpful to
The neuroendocrine aspects of
briefly review the body's heat-regul- h e a t p r o d u c t i o n ( n o n s h i v e r i n g
ating system.
thermogenesis) involve a more
We can think of the body as a delayed increase in heat production
l a y e r e d s t r u c t u r e w i t h a c o r e through the pituitary, thyroid, and
protected by a superficial zone and adrenal mechanisms.
an intermediate zone, which
Hypothermia occurs when the
modulate heat loss and gain.
system fails to function properly or
The superficial zone is composed w h e n e n v i r o n m e n t a l c o n d i t i o n s
of the skin, subcutaneoustissue,and render it inadequate.
thermoreceptors; these structures
The most obvious consequence is
are the most important agents in heat a decreased metabolic rate; it drops
exchange.
to 50 percent of normal when core
Skin temperature varies with blood temperature reaches 2BC (B2F),
flow, ambient air temperature, hum- diminishing oxygen consumption
idity, and air velocity and may drop and CO2 production.
to nearly environmental levels in an
effort to conserve heat.
How hypothermiaoccurs
The intermediate zone is
Accidental hypothermia is defined
composed of the skeletal-muscle
mass, which ordinarily contributes as a spontaneous decrease of the
core temperature (rectal, oesophaglittle to heat production.
When the core is in danger, how- eal, or tympanic membrane) below
ever, the muscles can produce a con- 35C (95F), usually but not always in
siderable amount of heat by shiver- a cold environment, presenting as an
ing, which, in turn, causes muscular acute problem without primary
vasodilatation and an increase in disease of the temperature-regulatblood flow and delivery of warmed ory centre.
Among the reasons for the
blood to the core.
Integration of these various com- increased incidence of the disorder
among the elderly are inactivity; malponents of the body's response to
cold exposure is coordinated by the Continuedouerleaf
Hypothermia in the elderly
nutrition; medications that impair
central nervous system responses
and peripheral vasomotor responses;
decreased basal metabolic rate, body
fat, and skeletal-muscle mass; the
presence of circulatory or hormonal
disorders; and reduced mental
capacity.
In addition, elderly people may
lack the appropriate physiological
responses to cold.
Compared with younger people,
they may be unable to control their
heat loss effectively by peripheral
vasoconstriction. Often, they are less
able to sense the cold than they were
when they were younger.2
An episode of hypothermia may
itself damage the patient's thermoregulatory mechanism for as long as
three years afterward and may make
him even more vulnerable to subsequent episodes of hypothermia.2, 3
The mortality from significant
hypothermia in the elderly is about
BO percent, compared with only 10
percent in younger patients, an astounding difference.
One of the reasons is that
temperature is usually recorded with
standard clinical mercury thermometers, which do not register low
levels of body temperature, even
when shaken down.
The proper diagnosis of hypothermia requires a thermometer that will
read at least as low as 24C (75F).
Electronic digital thermometers have
a far wider range than mercury
thermometers.
When
to
hypothermia
suspect
As most of us were taught in
medical school, you can't diagnose
what you don't think of; therefore,
considerthe possibilityof accidental
hypothermiain the differentialdiag.
nosisof elderlypeoplewho haveany
of a number of presentations,even
when environmentalconditions are
not extreme.
Surprisingly,most elderly victims
of accidential hypothermia neither
shivernor turn pale.
These symptoms may be followed
by fatigue, weakness, slow move.
ments, incoordination, apathy, and
generalised confusion. As the core
temperature decreases, judgement
declines, hallucinations often occur,
and the patient may become
extremely combative and resist all
attempts at medical aid. If the core
temperature drops below 27C
(80,6F), the patient will go into a
deep coma.
and dead. Patients have fully
recoveredafter core temperaturesas
low as 17C (60F).
When an elderlypersonis found in
a state of undress, people may
suspectthat he or she is a victim of
foul play.aIf the patientis a woman,
Checkthe organ systems police may jump to the conclusion
Beyond the fact that hypothermia that she is a rape/murdervictim and
may be missed through inadequate refuse to allow anyone, including
temperaturereadings,patientsmay medical personnel,to examine the
be subjectedto over.zealous
or even body.
If there is even the remotest
injuriousmedicalcare.
Since the disorder can affect chance that accidentalhypothermia
literally every organ system in the is involved, aggressiveaction must
body, it may mimic such diseasesas be taken, no matter what the
hypothyroidism, hypopituitarism, authoritiessay.
Several anecdotal reports tell of
hypoadrenalism,senile dementia,
doctorsbeing arrestedfor interfering
and cardiovascular
shock.
Becauselow body temperatureis with a murder investigation,with the
associated with many of these "murder victim" being saved after
conditions,
the hypothermia
goesun- appropriatemedicaltherapy.a
noticedand untreated.
Cardiouascularsgstem. Look for a
Thus, in making a differential declinein heartrate and cardiacoutdiagnosisit is important to evaluate put as indicationsof hypothermia.
the organsystemswith an understan- Although the blood pressurerisesinding of how a hypothermic state itially, it gradually falls with core
affectsthem.
hypothermia.
Central neruoussgstem. Cerebral
Clinicallysignificanthypotensionis
blood flow decreasesseven percent usuallypresentby 25C (7BF).
for each degree centigradedrop in
Be especially alert to hemo.
c o r e t e m p e r a t u r e . T h i s a n d dynamic effects of cold .on myo.
alterations in the microcirculation cardialconduction.At 3OC(B6F),a
resulting from increasedblood vis. definite progressionof ECG abnor.
cosity are the causesof the typical malities begins, with a diminished
abnormal or decreased mentation sinusrate,T.waveinversion,Q-T intervalprolongation,and the develop.
seen in hypothermicpatients.
Dizziness, blackouts, confusion, ment of the pathognomonicJ, or
euphoria, or even overt psychosis "Osborn",wave (Figure 2).
Atrial fibrillationor flutteris usually
may developas the core temperature
presentby 2BC (B2F), and below
orops.
Fixed, dilated pupils suggest a 2BC junctional rhythm, ventricular
temperaturelevel below 30C (B6F). fibrillation,and asystoleall become
Hyporeflexiaprogressesas the core likely possibilities.
temperature drops, and a classic
Careful management of patients
"hung up" reflexdevelopsthat can be with such abnormalitiesis criticalto
easilyconfusedwith hypothyroidism. avoidtriggeringventricularfibrillation
The patient is usually areflexicat or cardiacasystole.5
25C (77F) or below. A flat EEG
Respiratorgsgstem. Depressionof
indicatesa level below 20C (6BF). In the respiratory centre becomes
an emergency room setting, these significant only when the core
findingsand the lack or palpableperi. temperatureis very low, but decreaspheral pulsesmay make the patient ed mentation, a diminished cough
appeardead.
reflex, and cold-inducedbronchorThe one universalaxiom of hypo. rhea lead to aspiration, difficulty
thermia that needs to be stressedis clearing secretions,and secondary
that no one is dead until he is warm Pneumonias'
To paqe6
FamilyPractice- May 1982
-Hypothermia
i the elderl
l"
:ir:"trri
Stimulation of
skin thermoreceDtors
Direct reflex
uasoconstriction
Shiuering
Vasodilation
in skeletal
Endocrine
calorie
production
(thgroid
adrenal)
lncreased
blood flow
',
return to the core
.:irP:
t'
.t-.'
Feedback to
hgpothalamus
Figure 7 How the body keeps warm
Samples for blood gases are
The oxyhemoglobindisassociation routinely put on ice and in the
laboratory are rewarmed to 37C
curve shifts to the left with an increas'
is
(98,6F)
to be run through the blood'
this
but
for
oxygen,
affinity
ed
u s u a l l y n o t c l i n i c a l l y s i g n i f i c a n t gas analyzer.
If you fail to warn the lab that a pabecause of the decrease in oxYgen
core temperature is, say, 3OC
hYPothermia.
tient's
requirementswith
(B6F), the blood-gas analysiswill be
In hgpothermta, respiratorg arrest r e p o r t e da s p H , 7 , 2 O , P C O 2 , 6 0 p e r '
usuallg indicates that the patient's
cent, and PO2, 90 percent, instead
core temperature has fallen to 24C
of 7,3O, 44, and 60, respectively.
(7sF).
A diagnosis of excessive CO2
and over-allacidosis,based
retention
the
affects
Hypothermia markedly
data, could result
unadjusted
on
the
gases,
blood
routine
of
interpretation
and blood-gas determinations must in inappropriate and excessive treat'
be adjusted to reflect the effective ment.
Alkalosis, like acidosis, markedlY
tissue level at a given core
the develoPment of venti"
favours
temDerature.
cular tachycardia. The treatment of
an apparent severe acidosiswith ex'
cessive amounts of bicarbonate
could easily produce alkalosis, with
catastrophicresults.5
Acid-base equiltbrium. The acidbase status of a patient with hypo'
thermia depends to a great extent on
the patient's age and the presence of
other concomitant illnesses. Most
hypothermic patients show acidosis
secondary to CO2 retention from
respiratory failure, or metabolic
microcirculatoryfailure.
If shivering has occurred it may
also causea great increasein the production of lactic acid; the accumula-
- May 1982
FamilyPractice
Hypothermia in the elderly
tion may be aggravated by decreased
metabolic clearance of the lactic acid
by the liver.
ln addition, circulatory failure may
prevent organic acids from being
mobilised toward the appropriate
buffer systems. This may help to explain why patients are only mildly
I
acidotic while they are hypothermic
and why they tend to get much more
severe acidosis during the rewarming
process as the products of anaerobic
I
metabolism return to the general cir\
II
7
culation.
{
Hematologic effects. Hypothermia
H
brings an increased hematocrit as a
result of plasma loss and splenic con.
traction. A significant increase in
blood viscosity occurs at 27C (BOF)
Figure 2. The characteristicJ or "Osborn" waue of hgpothermiacloselgfollows
or less.
the QRS.It mag be mistakenfor a T waue with a narrow QT interualif the true T
The leukocyte and platelet counts
waue is obscured.Theslightlg roundedpeak distingubhesit from the R' of rightare depressedas a result of splenic, bundle-branchblock.
hepatic, and intravascular sequestration.
Particularlyduring rewarming, disseminated intravascular coagulation
is a major complication in some pa- Rewarming
the patient
has also been used successfully.S'9
tients, especially the elderly.
The
choice
of
a
specific
warming
A relatively new technique, inhalaGastrointestinal tract. Gastroinmethod
may
depend
on
the
duration
tion
of heated aerosol, can be used in
testinal motility decreasesbelow 34C
(94F), and ileus is universal in signifi- and degree of hypothermia, the the field or office situation. Although
cant hypothermia. Hepatic detoxi- availability of resources, the time the data are somewhat limited at this
fication and conjugation are also n e c e s s a r y t o m o b i l i s e t h e s e time, the proponents of heated aeroseverely depressed with hypother- resources, and contraindications that sol claim that it is just as effective as
the other ms*1e45.1o' 11
mia, and drugs, especially those may be present in individual cases.
general,
In
most
experts
feel
You should anticipate postwarmthat
given during the hypothermia, reing
rapid
core
rewarming
is
the
most
complications such as ischemic
efmain in the system for prolonged
fective way to increase survival.5, 6 damage to various parLsof the body,
periods.
This is another frequent cause of Peritoneal dialysis, first used in pneumonia, adult respiratory distress
1967,
h a s b e e n e x t r e m e l y syndrome, disseminated intravaserror in treating hypothermia.
cular coagulation, acute tubular
effective.T
Kidnegs. Urine flow increases with
necrosis, and sepsis so that you can
E
x
t
r
a
c
o
r
p
o
r
e
a
l
r
e
w
a
r
m
i
n
g
,
b
y
(cold
ditemperature
a dropping core
uresis),probably because of depress- means of either femoral-femoral treat them appropriately if they deshunt or cardio-pulmonary bypass, v e l o p . I
ed oxidative tubular activity.
Reducedsodium and water resorption results;with a shift of fluids to the
extracellular spaces, it renders the
References
hypothermic patient hypovolemic in1 Altus, P, Hickman, JW, Pina, l, et al: Hgpothermia in the sunng South. South Med J
travascularly.
73:1491,198O.
2 What's uarm enough for the goung mag kill the old (editoria\. JAMA 239:180, 1978.
Endocrine sgstem. Because
3 6OF can induce accidential hgpothermia in the aged. Internal Medicine News and
hypothermia inhibits both the release
Diagnosis Neus 14:19, February 6, 1981 .
of insulin from the pancreas and the
4 Cunbg, P: Cold facts concerning hgpothermia. JAMA 243:1403, 1980.
peripheral use of glucose, it causes
5 Reuler, JB: Hgpothermia: Pathophgsiologg clinical settings, and management. Ann Intem Med 89:519, 1978.
hyperglycaemia. The condition
6 Welton, DE, Mattox, KL, Miller, RR, et al: Treatment of profound hgpothermia. JAMA
usually disappears with rewarming,
24O:2291,1978.
and any attempt to reverse it with in7 Reuler, JB, and Pa*er, RA: Peritoneal dialgsis in the management of hgpothermia.
sulin is extremely dangerous, since it
JAMA 24O:2289, 1978.
may result in profound hypogly8 Dorseg, JS: Venoarterial bgpass in hgpothermia (letter). JAMA 244:19OO, 198O.
9 Totune, WD, Ceiss, WP, Yanes, HO, et al: Intractable uenticular fibrillation associated
caemia.
with profound accidental hgpothermia - successful treatment uith partial cardiopul.
Remember, shivering may deplete
monary bgpass. N Engl J Med 287:1 135, 1972.
much of the body's stored glycogen,
1O Miller, JW, Danzl, DF, and Thomas, DM: Urban accidental hgpothermia - 135 cases.
a situation that can also lead to hypoAnn Emerg Med 9:456, 1980.
1 1 Edsall, DW: Treatment of hgpothermia (letter). JAMA 244:1902, 1980.
glycemia if insulin is given.
il
JI
FamilyPractice- May 1982