An Intriguing Diagnosis

Case 1:

Hypothermia Following a Fall

A 62-year-old woman was found on thefloor of her bathroom at home with herwheelchair partially on top of her.She was unresponsive except to painfulstimulus.The patient had a 20-year historyof multiple sclerosis, diabetes mellitus,and hypertension. Home health carenurses visited her several times a week.During the previous months, she hadbeen admitted to the hospital severaltimes for falls.When she arrives at the emergencydepartment (ED), the patient isstill unresponsive; her temperature is29C (84.2F). She is immobilized toprotect the cervical spine and is intubatedwithout complication. She is thentransferred to a trauma facility for furtherevaluation.At the trauma facility, the patientarrives intubated and immobilized.Her breath sounds are equal; pulsesare equal but weak throughout. Hertemperature is 30C (86F); bloodpressure, 137/56 mm Hg; heart rate,83 beats per minute; and respirationrate, 14 breaths per minute. There isno evidence of head trauma; pupils are3 mm and reactive. Heart and lungsare normal; abdomen is soft and nontender,with hypoactive bowel sounds.Extremities show multiple bruises invarious stages of healing, 1+ pedaledema, and no deformities. Neck andback examination reveal no deformity,misalignment, or abrasions.Initial radiographs of the cervicalspine and pelvis show no fracture. Achest radiograph reveals no infiltratesor pneumothorax. The endotrachealtube is in the proper position.An ECG demonstrates normalsinus rhythm, prolonged QRS durationand QT interval, and Q waves inferiorlythat suggest a remote inferior wall in-farction (Figure). J (Osborne) wavescan be seen in lead II and the lateralprecordial leads.Blood glucose level is 655 mg/dL;bicarbonate, 14 mEq/L; sodium, 151mEq/L; chloride, 103 mEq/L; potassium,2.4 mEq/L; blood urea nitrogen,69 mg/dL; and creatinine, 1.1 mg/dL.Toxicology screening is negative for alcoholand other substances of abuse.Creatine kinase level is 1885 U/L(normal, 57 to 375 U/L). Moderatequantities of ketone bodies are presentin the serum. Results of urinalysis arenegative for infection but reveal blood,myoglobin, and large quantities of ketonebodies. A CT scan of the headshows brain atrophy; there is no bloodor evidence of a stroke.External warming is done in theED with warm fluids and blankets.Humidified warm air is providedthrough the ventilator. The patient istransferred to the ICU, where rewarmingis continued and treatment for diabeticketoacidosis is initiated.

Case 1:

HYPOTHERMIA:AN OVERVIEW

One of the most common environmentalemergencies, hypothermiaoccurs in all geographic locationsand during all seasons. It isdefined as a core temperature of lessthan 35C (95F).1 Hypothermiacan be mild (32C to 35C [89.6Fto 95F]), moderate (28 to 32C[82.4F to 89.6F]), or severe (lowerthan 28C [82.4F]).

¹

Approximately700 deaths occur annually from hypothermiain the United States;half of these are associated with extremelycold weather.

²

Signs and symptoms worsen asthe degree of hypothermia progresses.Mild hypothermia is characterizedby vigorous shivering, cold diuresis,and tachycardia. As the body temperaturefalls, amnesia, apathy, bradycardia,loss of fine motor skills, andslurred speech may occur. Signs ofsevere hypothermia include apnea; extreme bradycardia; coma; hypotension;impalpable pulses; and fixed,dilated pupils.

CAUSES OF HYPOTHERMIA

Accidental hypothermia is morecommonly seen in those who areill, isolated, and socially deprived(

Table 1

). Predisposing causes includeadvanced age, medication use,and acute and chronic pathologicconditions.

¹

Hypothermia may beprecipitated in a healthy person byacute exposure to a cold environment,more prolonged exposure ina less cold environment (chronic hypothermia),

¹

or forced inactivity (eg, after a fall).Disease states associated withhypothermia include stroke, CNS infectionor trauma, uremia, Parkinsondisease, and multiple sclerosis.1 Autonomicdysfunction from diabetes mellitus,infection, or cardiac failure alsopredisposes to hypothermia. Heatproduction may be impaired by hypothyroidism,hypoadrenalism, or hypoglycemia.Pancreatitis and diabeticketoacidosis

³

have also been cited asprecipitants of hypothermia.Elderly persons are especiallyprone to hypothermia. The ability tothermoregulate becomes impairedwith age.

¹

Elderly persons are less ablethan younger ones to generate heatbecause of such factors as decreased lean body mass, impaired mobility, inadequatediet, a decreased shiveringresponse, and diminished vasoconstrictiveability. Many have multiple medicalconditions that impair thermoregulation.Alcohol consumption and theuse of medications, such as sedatives,narcotics, and tricyclic antidepressants,further impair thermoregulation.

ECG FINDINGS INHYPOTHERMIA

ECG findings may include sinusbradycardia, prolonged intervals,junctional rhythms, and atrial fibrillation(

Table 2

).

⁴

When a patient'score temperature falls below 30C(86F), there may be increased myocardialirritability and ectopic beats.The risk of asystole and ventricularfibrillation increases as temperaturedecreases to below 25C (77F).

⁴

Ventricular fibrillation is more likelyto occur with sudden changes in partialpressure of oxygen, partial pressureof carbon dioxide, or myocardialtemperature, or changes in electrolytesor acid-base status.

⁴

With severehypothermia, treatment of ventricularfibrillation is difficult until thecore temperature approaches 30C(86F). Bretylium is the antiarrhythmicof choice, because it increasesthe refractory period and raises thearrhythmia threshold.

¹

The J wave is defined as a deflectionat the end of the QRS complexthat is 1 mm or greater in elevationand occurs in 2 consecutivebeats. The J wave is most commonlyfound in the lateral precordial leadsand in lead II.

^4,5

The exact cause ofthis wave is unknown. The presenceof a J wave is sensitive and specificfor hypothermia; however, thesewaves have also been associatedwith subarachnoid hemorrhage,acute cardiac ischemia, and hypercalcemia.

⁴

In hypothermic patients,the size of the J wave correlates inverselywith falling temperatures.The J wave does not correlate withprognosis. The J wave in the precordialleads may mimic ST-wave elevationand therefore might cause confusionas to whether the patientmight be having an acute myocardialinfarction.

TREATMENT

Airway, breathing, and circulationconcerns need to be addressedquickly and efficiently. Airway manipulationin the hypothermic patientwas formerly thought to precipitatemalignant arrhythmias. However, intubationcan be done safely with goodpreoxygenation. Management shouldalso include evaluation for trauma,especially if there is a recent historyof a fall or if the patient was foundunconscious.A critical element of treatment isappropriate rewarming. Passive rewarmingmay include removal of wetclothing, a warm blanket, and a warmenvironment. Active rewarming includeswarm intravenous fluids, warmhumidified air, and gastric or peritoneallavage with warm fluids. Someinvestigators have noted improvedoutcomes with cardiopulmonary bypass.

^6,7

Continuous arteriovenous rewarming--hemofiltration through thefemoral artery and vein--has beenshown to improve survival and reduceblood and fluid requirements,organ failure, and length of stay in the ICU.

⁸

Shock that requires treatmentwith vasoactive drugs is an independentrisk factor for mortality;initial core temperature is not.

⁷

Most patients with hypothermiaare treated with a combination ofpassive rewarming and warm fluids.These measures need to be initiatedas soon as possible in the field andcontinued in the ED. For patientswho do not respond to initial management,more aggressive approachesmay be considered. Because formalguidelines do not exist, local experienceand availability of intensivists oranesthesiologists will dictate themethod chosen.

OUTCOME OF THIS CASE

While the patient was in theICU, pneumonia and sepsis developed.After a prolonged ICU course,and following consultation with thefamily, support was withdrawn. Thecause of the hypothermia was probablya combination of prolonged immobilityfollowing a fall precipitatedby her multiple sclerosis, and the underlyingdiabetes. Her previous fallswere witnessed by a visiting nurse;this was the first time she had sufferedsuch prolonged immobility.

References:

REFERENCES:

1.

Mallet ML. Pathophysiology of accidental hypothermia.

QJM

. 2002;95:775-785.

2.

Hypothermia-related deaths-Philadelphia, 2001,and United States, 1999.

MMWR

. 2003;52:86-87.

3.

Gale EA, Tattersall RB. Hypothermia: a complicationof diabetic ketoacidosis.

Br Med J

. 1978;2:1387-1389.

4.

Vassallo SU, Delaney KA, Hoffman RS, et al. Aprospective evaluation of the electrocardiographicmanifestations of hypothermia.

Acad Emerg Med

.1999;6:1121-1126.

5.

Mattu A, Brady WJ, Perron AD. Electrocardiographicmanifestations of hypothermia.

Am J EmergMed

. 2002;20:314-326.

6.

Walpoth BH, Walpoth-Aslan BN, Mattle HP, et al.Outcome of survivors of accidental deep hypothermiaand circulatory arrest treated with extracorporealblood warming.

N Engl J Med

. 1997;337:1500-1505.

7.

Vassal T, Benoit-Gonin B, Carrat F, et al. Severeaccidental hypothermia treated in an ICU: prognosisand outcome.

Chest

. 2001;120:1998-2003.

8.

Gentilello LM, Cobean RA, Offner PJ, et al. Continuousarteriovenous rewarming: rapid reversal ofhypothermia in critically ill patients.

J Trauma

. 1992;32:316-325.