Hypothermia: Staging, Physiology, ECG Changes, Rewarming, and Cardiac Arrest Practice Questions

25 multiple-choice questions on Hypothermia: staging, physiology, ECG changes, rewarming, and cardiac arrest for paramedic and EMT students, from Chapter 39 (Environmental Emergencies). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

25 practice questions

1. Which core temperature marks the line between mild and moderate hypothermia?

   1. A. 35°C (95°F)
   2. B. 28°C (82°F)
   3. C. 24°C (75°F)
   4. D. 32°C (90°F)
   Show answer

   Answer: D. 32°C (90°F)

   Hypothermia begins below 35°C (95°F); mild is 32 to 35°C (90 to 95°F), moderate 28 to 32°C (82 to 90°F), and severe below 28°C (82°F). Around 32°C shivering fades and mental status and heart rate fall, so 35°C marks the onset of hypothermia, not the mild-moderate boundary.

2. A 50-year-old hiker is shivering vigorously, alert, and stumbling, with slurred speech, after a cold rain. Her stage of hypothermia is most likely:

   1. A. Moderate
   2. B. Severe
   3. C. Mild
   4. D. Profound
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   Answer: C. Mild

   Shivering with a normal level of consciousness but poor coordination fits mild hypothermia (Swiss stage 1). Shivering stops and confusion worsens in moderate hypothermia.

3. In the Swiss staging system, which is used when core temperature cannot be measured, the stage is assigned mainly by:

   1. A. Heart rate and the systolic blood pressure
   2. B. Skin color and capillary refill
   3. C. Pupil size and the reflexes
   4. D. Level of consciousness and shivering
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   Answer: D. Level of consciousness and shivering

   Swiss staging uses clinical signs: stage 1 conscious and shivering, stage 2 impaired consciousness and not shivering, stage 3 unconscious, and stage 4 no vital signs. These correlate roughly with temperature bands.

4. A man found outdoors is confused, has stopped shivering, and has a pulse of 48/min. His temperature is most likely in the range of:

   1. A. 33 to 35°C (91 to 95°F)
   2. B. 28 to 32°C (82 to 90°F)
   3. C. Below 24°C (75°F)
   4. D. 35 to 36°C (95 to 97°F)
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   Answer: B. 28 to 32°C (82 to 90°F)

   Loss of shivering, confusion, and bradycardia point to moderate hypothermia. Mild hypothermia keeps shivering and normal mentation.

5. A finding typical of severe hypothermia below 28°C (82°F) is:

   1. A. Coma with slow breathing and bradycardia
   2. B. Vigorous shivering with a fast heart rate
   3. C. Hot, flushed skin with heavy sweating
   4. D. Rapid breathing with agitation and pain
   Show answer

   Answer: A. Coma with slow breathing and bradycardia

   Severe hypothermia causes coma, rigidity, slow breathing, and bradycardia, and pupils may be fixed and dilated without meaning death. Shivering and tachycardia belong to mild hypothermia.

6. The Osborn (J) wave seen on the ECG of a hypothermic patient is:

   1. A. A deep, inverted T wave in the limb leads
   2. B. A narrow, peaked T wave in V2 to V4
   3. C. A saw-tooth baseline between QRS
   4. D. A positive hump at the end of the QRS
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   Answer: D. A positive hump at the end of the QRS

   The J wave is a positive deflection at the junction of the QRS and ST segment, becoming larger as temperature falls. Peaked T waves suggest hyperkalemia, not hypothermia.

7. Which ECG rhythm is common in moderate hypothermia?

   1. A. Sinus tachycardia at a rate above 150/min
   2. B. Atrial fibrillation with a slow rate
   3. C. Supraventricular tachycardia
   4. D. Ventricular tachycardia with pulses
   Show answer

   Answer: B. Atrial fibrillation with a slow rate

   Slow atrial fibrillation, sinus bradycardia, and prolonged PR, QRS, and QT intervals are typical as the heart cools. Tachycardia is expected only in mild hypothermia while the patient shivers.

8. A hypothermic patient produces large amounts of dilute urine early in the cold exposure. This cold diuresis results from:

   1. A. Increased drinking of warm fluids
   2. B. Kidney injury from muscle damage
   3. C. Central shunting of blood volume
   4. D. High levels of antidiuretic hormone
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   Answer: C. Central shunting of blood volume

   Vasoconstriction moves blood centrally, the body senses volume overload, and the kidneys excrete fluid, leaving the patient volume depleted. ADH release is actually suppressed, not increased.

9. A severely hypothermic patient must be moved gently and kept horizontal because rough handling can:

   1. A. Trigger ventricular fibrillation
   2. B. Cause her to start shivering again
   3. C. Break bones made brittle by the cold
   4. D. Cause a potassium surge
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   Answer: A. Trigger ventricular fibrillation

   The cold myocardium is irritable, and jostling, rough transfers, or sitting the patient up can precipitate VF. Keeping the patient flat also limits orthostatic hypotension. Gentle handling is not about bone fragility or potassium release, and renewed shivering would be a sign of recovery rather than a danger.

10. Afterdrop refers to:

    1. A. The sudden rise in core temperature with rewarming
    2. B. A drop in shivering once the core is warm
    3. C. Low blood pressure during the first exposure
    4. D. A continued fall in core temperature after rescue
    Show answer

    Answer: D. A continued fall in core temperature after rescue

    Cold blood returning from the periphery, along with continued conduction from cold tissue, can lower core temperature further after removal from the cold. Vigorous limb movement and rewarming the limbs first worsen it.

11. A 63-year-old man found in a snowbank is unresponsive and very cold, and you cannot see him breathing. Under wilderness hypothermia guidelines, you should check for breathing and a pulse for:

    1. A. No more than 5 seconds
    2. B. Up to 60 seconds
    3. C. About 10 seconds
    4. D. A full 5 minutes
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    Answer: B. Up to 60 seconds

    In severe hypothermia the heart rate and breathing can be so slow and weak that a short check misses them, so the WMS 2019 hypothermia update and ERC 2021 advise checking for signs of life, breathing, and a pulse (ideally a central pulse, and a monitor if available) for up to a minute. Starting compressions on a patient who still has a perfusing rhythm can trigger VF. The usual 10-second check of standard BLS is meant for normothermic patients and can miss a pulse of a few beats per minute; 5 seconds is even less reliable. A 5-minute check needlessly delays CPR in a patient who truly is in arrest. AHA 2020 acknowledges the pulse is hard to detect in hypothermia but sets no specific interval, so follow local protocol. (WMS 2019 hypothermia update; ERC 2021 special circumstances.)

12. The first step in caring for any hypothermic patient is to:

    1. A. Rub the arms and legs briskly to restore blood flow
    2. B. Give hot coffee to warm the patient fast
    3. C. Remove from the cold and stop further heat loss
    4. D. Place the patient in a sitting position
    Show answer

    Answer: C. Remove from the cold and stop further heat loss

    Removing wet clothing, insulating from the ground, protecting from wind, and moving to a warm environment stop ongoing losses. Rubbing the limbs drives cold blood to the core and risks VF.

13. Active external rewarming for a moderately hypothermic patient in the field includes:

    1. A. Heat packs to the chest, axillae, and back
    2. B. Hot water bottles placed on the hands and feet
    3. C. Immersing the patient in a hot tub
    4. D. Vigorous exercise to generate heat
    Show answer

    Answer: A. Heat packs to the chest, axillae, and back

    Heat sources should be applied to the trunk where large vessels lie close to the surface, with insulation between pack and skin. Warming the extremities first can worsen afterdrop.

14. While ventilating an intubated, severely hypothermic patient with a pulse, you should:

    1. A. Ventilate at 20 to 30 breaths/min
    2. B. Target an ETCO2 of 25 to 30 mm Hg
    3. C. Use the largest tidal volume tolerated
    4. D. Avoid hyperventilating him
    Show answer

    Answer: D. Avoid hyperventilating him

    Severely hypothermic patients produce little CO2, so hyperventilation easily causes alkalosis and may make the cold heart more prone to ventricular fibrillation. Ventilate at a normal or slower rate guided by capnography, using warmed, humidified oxygen if available. A high rate, a low ETCO2 target, or oversized breaths all amount to hyperventilation.

15. A hypothermia wrap for a wilderness evacuation should include:

    1. A. Insulation, vapor barrier, and wind shell
    2. B. One cotton blanket wrapped loosely over the body
    3. C. Wet clothing left on beneath a tarp
    4. D. Heat packs placed directly on bare skin
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    Answer: A. Insulation, vapor barrier, and wind shell

    A hypothermia wrap layers dry insulation (sleeping bags, pads underneath), a vapor barrier such as plastic or a foil sheet to stop evaporative loss, and an outer windproof and waterproof shell, so conduction, evaporation, convection, and radiation are all limited. A single loose cotton blanket gives little insulation and loses it when damp. Wet clothing left on keeps drawing heat out by evaporation and conduction; remove it or, if exposure is severe, wrap a vapor barrier over it. Heat packs belong on the chest, axillae, and back with a layer between pack and skin, because cold skin burns easily. (WMS 2019 hypothermia update.)

16. A shivering, alert hypothermic hiker who can swallow may be given:

    1. A. Alcohol to dilate vessels
    2. B. Snow to eat for hydration
    3. C. Warm, sweetened drinks
    4. D. Nothing by mouth
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    Answer: C. Warm, sweetened drinks

    Calories fuel shivering, so warm, sweet drinks or food help an alert patient who can swallow safely; the warmth itself adds little heat. Alcohol dilates skin vessels, increases heat loss, and impairs shivering. Eating snow costs body heat to melt and warm it, so melt it into warm water instead. Withholding everything by mouth is appropriate only when the patient cannot protect the airway; an alert, shivering patient benefits from the calories. (WMS 2019 hypothermia update.)

17. A hypothermic patient in VF should be treated, per current AHA guidance, with:

    1. A. No shocks until 35°C
    2. B. Standard defibrillation
    3. C. Lidocaine but no shocks
    4. D. Pacing instead of shocks
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    Answer: B. Standard defibrillation

    Current AHA guidance says it may be reasonable to defibrillate per the standard BLS algorithm and to consider epinephrine per standard ACLS, while rewarming. Some protocols still limit shocks and drugs below 30°C (86°F), so follow local direction.

18. The phrase "no one is dead until warm and dead" means that a hypothermic patient in arrest should:

    1. A. Be declared dead if no pulse is felt after 10 seconds
    2. B. Be warmed only after the coroner has been called
    3. C. Receive CPR only if the ECG shows ventricular fibrillation
    4. D. Be resuscitated and rewarmed before death is declared
    Show answer

    Answer: D. Be resuscitated and rewarmed before death is declared

    Cold protects the brain, and patients have survived prolonged hypothermic arrest with good neurologic outcomes, so resuscitation and rewarming continue (often to an ECMO or bypass center) before death is declared, unless there are injuries incompatible with life, the chest is frozen and cannot be compressed, or rescuers are at risk. A 10-second pulse check is too short in hypothermia, and a missed pulse is not death. Waiting for the coroner abandons a patient who may be salvageable. Asystole and PEA are also treated in hypothermic arrest; CPR is not limited to VF. (WMS 2019 hypothermia update; AHA 2020 accidental hypothermia.)

19. Which hypothermic patient in cardiac arrest is the best candidate for transport to a center with ECMO or cardiopulmonary bypass?

    1. A. A patient with a decapitating injury
    2. B. A patient who cooled before arresting
    3. C. A patient whose chest is frozen solid
    4. D. A patient with dependent lividity
    Show answer

    Answer: B. A patient who cooled before arresting

    Extracorporeal rewarming is the treatment of choice when hypothermia came first and caused the arrest, and it can restore circulation after prolonged CPR. Obvious lethal injury, a frozen incompressible chest, or signs of death such as lividity are reasons not to resuscitate.

20. Advanced airway management in a severely hypothermic patient who needs it is:

    1. A. Contraindicated below 32°C
    2. B. Avoided because it causes VF
    3. C. Indicated and performed gently
    4. D. Delayed until after rewarming
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    Answer: C. Indicated and performed gently

    The risk of inducing VF with intubation is low and outweighed by the benefit of a secure airway, so intubation is done gently when indicated. Avoid hyperventilation, which can also precipitate dysrhythmias.

21. An 80-year-old woman is found on her kitchen floor in winter with a temperature of 31°C (87.8°F). Besides environmental exposure, you should look for:

    1. A. An underlying cause such as stroke or sepsis
    2. B. Signs of an overactive thyroid from her medicines
    3. C. Evidence of recent alcohol withdrawal
    4. D. Recent strenuous exercise
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    Answer: A. An underlying cause such as stroke or sepsis

    Older adults often become hypothermic indoors because a stroke, fall, hypoglycemia, sepsis, hypothyroidism, or drugs prevented them from staying warm. Treat the hypothermia and look for the cause. An overactive thyroid, alcohol withdrawal, and exertion all tend to raise rather than lower body temperature.

22. A hypothermic patient's glucose is 52 mg/dL. This is common because:

    1. A. Cold increases insulin resistance
    2. B. The liver stores more glycogen
    3. C. Cold blocks glucose absorption
    4. D. Shivering consumes glucose stores
    Show answer

    Answer: D. Shivering consumes glucose stores

    Prolonged shivering depletes glycogen and glucose, and alcohol, malnutrition, and exhaustion contribute. Treat with dextrose per protocol.

23. Paradoxical undressing, in which a severely hypothermic person removes clothing, is thought to result from:

    1. A. Sudden vasodilation causing a sensation of heat
    2. B. An assault by another person at the scene
    3. C. Excess sweating as the core begins to warm up again
    4. D. Shivering that raises the core temperature
    Show answer

    Answer: A. Sudden vasodilation causing a sensation of heat

    Late in hypothermia, exhausted vasoconstriction may give way to vasodilation that makes the patient feel hot, along with confusion. It can be mistaken for assault when the patient is found undressed.

24. In an avalanche burial, a victim found in cardiac arrest after more than 60 minutes with a packed, obstructed airway most likely died of:

    1. A. Hypothermia rather than asphyxia
    2. B. Trauma from the snow above him
    3. C. Asphyxia rather than hypothermia
    4. D. Heat loss by evaporation of sweat
    Show answer

    Answer: C. Asphyxia rather than hypothermia

    Asphyxia kills most avalanche victims early; a long burial with an ice-packed airway suggests asphyxial arrest with a poor prognosis. A patent airway or air pocket raises the chance of a reversible hypothermic arrest.

25. A man rescued from cold water is alert and shivering. He tries to stand and walk to the ambulance. You should:

    1. A. Let him walk to warm the muscles
    2. B. Keep him horizontal and carry him
    3. C. Have him sit up to help breathing
    4. D. Rub his legs before he stands up
    Show answer

    Answer: B. Keep him horizontal and carry him

    After prolonged immersion, standing up can cause circumrescue collapse from loss of the water's hydrostatic support and from cold-induced dysrhythmias. Carry immersion victims horizontally.