Elderly Man With Obtundation

An 87-year-old man had recently been hospitalized for5 days for treatment of hypernatremia and dehydration.His condition improved following hydration and cautiouscorrection of the hypernatremia, and he was discharged.However, within 48 hours the patient's caregiver notedthat he was obtunded and less responsive; she broughthim to the emergency department.HISTORY
The patient has had at least 2 major strokes--themost recent about 4 years ago--and as a result has significantleft spastic hemiplegia. However, he has had reasonablemental function, has been quite conversable, and hasbeen able to live at home with significant help from hiscaregiver. He has hypertension, which is well controlledwith a β-blocker and a diuretic, and he is catheterized. Hismedical history includes multiple urinary tract and pulmonaryinfections over the last 7 years, which have respondedto various antibiotics. His medications includemetoprolol, hydrochlorothiazide, and clopidogrel; currently,he is not taking any antibiotics.PHYSICAL EXAMINATION
Repeated rectal temperatures are between 33.3^oCand 33.8^oC (92^oF and 93^oF). Heart rate is 68 beats perminute and regular; blood pressure, 130/70 mm Hg; and oxygen saturation, 97% on room air. Mucosae appear hydrated.Diffuse rhonchi are audible, but no lung consolidationis evident. Abdomen is nonremarkable. There are noskin lesions or decubiti. A neurologic examination revealsobtundation, no nuchal rigidity, and a dense spastic hemiplegiaon the left; these results--except for mental status--are unchanged from those at his previous admission.LABORATORY AND IMAGING RESULTS
Hemoglobin level is 10.7 g/dL. White blood cellcount and platelet count are normal. Serum sodium levelis 142 mEq/L, with normal osmolarity and no anion gap.Blood urea nitrogen level is 29 mg/dL, and creatininelevel is 2.1 mg/dL; these levels are unchanged since hislast admission. Serum albumin level is 1.9 g/dL.A review of data from the patient's last admissionreveals several instances of low temperatures (32.7^oC to33.8^oC [91^oF to 93^oF]) and normal thyroid function studies.Normal thyroid-stimulating hormone (TSH) andthyroid hormone levels were noted in the records of anadmission 6 months earlier.A chest radiograph shows no evidence of pneumonia.A brain CT scan reveals multiple old infarctions but noacute bleeding or other changes from the scan obtainedthe previous week.Which of the following is the most appropriate next step?A. Immediately administer thyroid hormone.B. Order appropriate cultures, and initiate broad-spectrum antibiotics.C. Immediately discontinue all medications.D. Immediately initiate an active core warming technique.E. Administer dantrolene sodium.CORRECT ANSWER: B
This patient has hypothermia that is not related to unusualexposure to cold. Although this condition is not frequentlyreported, it is probably not uncommon. Accidental hypothermiais a more common problem that is encountered incolder climates, particularly in the elderly.This man's hypothermia is unusual in that it developedin the hospital (and subsequently at home) and inthe summer, when ambient temperatures are much closerto body core temperature. However, analysis of his situationand findings shows that this thermoregulatory failureis not surprising.In a population of inpatients in whom hypothermiadeveloped, the average age was 77 and there was a malepreponderance and an array of underlying cofactors.These included infection, 85%, and cerebrovascular disease and stroke, 19%¹.This patient is elderly, has had cerebrovascularaccidents with residual effects, and has an indwellingcatheter, which predisposes him to infections.Hypothyroidism is a well-documented cause of hypothermia.However, this condition is much more commonlyassociated with hypothermia that develops out-of-hospital.² In addition, although the thyroid status of illpatients must be interpreted cautiously,³ this patient's normalTSH level from 6 months earlier (before he was ill)reasonably excludes this diagnosis and the need for thyroidhormone supplementation (choice A).Medications are another important risk factor forboth in-hospital and out-of-hospital hypothermia. Thosemost commonly associated with hypothermia are neuroleptics,such as phenothiazines, which likely affect centralhypothalamic control of temperature; neuroleptics are involvedin approximately 25% of cases of hypothermia.However, this patient's medications (an antihypertensive,a diuretic, and an antiplatelet agent for stroke prophylaxis)are less likely to be associated with hypothermia. It isprobably not necessary to discontinue these agents(choice C).Active core warming techniques (choice D), whichinclude the introduction of heated humidified air via endotrachealtube and volume expansion with warmed intravenous fluids, are indicated for moderate to severe accidentalhypothermia (32.2^oC to less than 28^oC [90^oF toless than 84^oF]). They are far too aggressive in the settingdescribed here.²Intravenous administration of dantrolene sodium(choice E), a muscle relaxant that inhibits calcium release,is the optimal therapy for malignant hyperthermia of anesthesia.It has no role in the treatment of hypothermia.⁴The prognosis for thermoregulatory failure is quitepoor. Mortality is 77%, and death usually follows a longhospital stay.¹ Comorbid predictors of death include poornutrition and sepsis. (This patient's nutrition has beendeteriorating, and his serum albumin level is less than2 g/dL. He also has a history of infections.)These associations sidestep the question of whichcomes first, hypothermia or its correlates. Most authoritiesbelieve the deterioration of bodily function--to thepoint that in-hospital hypothermia develops--itself suggestsa poor prognosis and impending death and signifiesa "point of no return."¹ In this setting, supportive measuresare indicated, including empiric antibiotic therapy(choice B).Outcome of this case. Repeated culture of specimensfrom the patient's Foley catheter revealed morethan 10⁶ colony-forming units/mL of Proteus species sensitiveto ceftriaxone. The urinary tract infection may haveprecipitated his hypothermia. Antibiotics were continued,and his temperature stabilized at around 36.1^oC (97^oF);however, he never recovered to his preadmission status.He received a percutaneous endoscopic gastrostomy tubeto supplement his oral intake. After a long hospitalization,he died in his sleep.

References:

REFERENCES:

1.

Kramer MR, Vandijk J, Rosin AJ. Mortality in elderly patients with thermoregulatoryfailure.

Arch Intern Med.

1989;149:1521-1523.

2.

Lazar HL. The treatment of hypothermia.

N Engl J Med.

1997;337:1545-1547.

3.

Spencer E, Eigen A, Shen D, et al. Specificity of sensitivity assays of thyrotropin(TSH) use to screen for thyroid disease in hospitalized patients.

ClinChem.

1987;33:1391-1396.

4.

Simon HB. Hyperthermia.

N Engl J Med.

1993;329:483-487.