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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