What are the vitals of a moderate hypothermia patient?

With a body temperature between 82.4°F and 90°F (28-32°C), a person is in a state of moderate hypothermia, which dramatically alters their vital signs and places them at a high risk for cardiac complications. Understanding these changes is crucial for proper emergency care.

Quick Summary

In moderate hypothermia, core body temperature falls to 28-32°C (82.4-90°F), causing slowed heart rate, low blood pressure, shallow breathing, and mental status changes like confusion and lethargy. Shivering ceases, and the risk of serious arrhythmias, such as atrial fibrillation, increases significantly.

Key Points

• Temperature Range: Moderate hypothermia is characterized by a core body temperature between 28-32°C (82.4-90°F).

• Cardiovascular Effects: Patients experience a slowed heart rate (bradycardia) and low blood pressure (hypotension).

• Respiratory Depression: Breathing becomes slow and shallow (bradypnea), reflecting a general systemic slowdown.

• Neurological Changes: Mental state declines, progressing to confusion, lethargy, or stupor; shivering ceases in this stage.

• Arrhythmia Risk: The cold heart is irritable and prone to arrhythmias like atrial fibrillation, which can progress to more serious ventricular arrhythmias.

• ECG Findings: Characteristic electrocardiogram changes include prolonged intervals (PR, QRS, QT) and the appearance of Osborn (J) waves.

Understanding the Stages of Hypothermia

Hypothermia, a dangerously low body temperature, progresses through three primary stages: mild, moderate, and severe. Each stage presents with a distinct set of symptoms and vital signs, reflecting the body's diminishing ability to regulate its temperature. Moderate hypothermia represents a critical phase where the body's compensatory mechanisms begin to fail, requiring immediate medical intervention to prevent progression to life-threatening severe hypothermia. Recognizing what are the vitals of a moderate hypothermia patient is a crucial skill for first responders and concerned bystanders alike.

The Core Vital Signs

Core Body Temperature

• The defining vital sign of moderate hypothermia is a core body temperature ranging from 28 to 32°C (approximately 82.4 to 90°F).
• This drop below the normal range of 36.5–37.5°C (97.7–99.5°F) indicates that the body can no longer produce enough heat to counteract its losses to the environment.
• Accurate temperature measurement requires specialized low-reading thermometers, as standard devices may not register this low range.

Cardiovascular Vitals: Heart Rate and Blood Pressure

• Heart Rate (Bradycardia): Unlike the initial, compensatory rapid heart rate seen in mild hypothermia, the heart rate in moderate hypothermia slows significantly (bradycardia) as the heart muscle cools.
• Blood Pressure (Hypotension): The patient will also experience low blood pressure (hypotension). This is worsened by 'cold diuresis,' a condition where the cold-induced constriction of blood vessels initially elevates blood pressure, but then leads to increased urination and subsequent fluid loss.
• Arrhythmias: The cooled myocardium becomes highly irritable, increasing the risk of arrhythmias. Atrial fibrillation is a common rhythm disturbance seen in this stage, but it can progress to more serious and life-threatening ventricular fibrillation as the temperature drops further.

Respiratory Vitals: Breathing Rate

• As with the cardiovascular system, the respiratory system slows down in moderate hypothermia. This leads to a decreased respiratory rate, known as bradypnea.
• Breathing may become slow and shallow, reflecting the body's overall systemic depression.

Neurological Vitals: Mental Status and Reflexes

• Mental Status: Patients in this stage show significant central nervous system (CNS) depression. They may be lethargic, confused, or stuporous, often losing the ability to think clearly or move effectively.
• Shivering: The body's last line of defense, shivering, typically ceases when the core temperature falls below approximately 30–32°C (86–90°F). This loss of a major heat-generating mechanism is a critical indicator of worsening hypothermia.
• Reflexes: Deep tendon reflexes become sluggish or are completely absent (hyporeflexia).
• Pupils: The pupils may dilate and become less responsive to light.

Additional Physical Signs

• Paradoxical Undressing: A phenomenon in which a person with moderate or severe hypothermia may become disoriented and remove their clothing, increasing heat loss.
• Weakened Muscle Tone: Muscles become stiff, and coordination is severely impaired, contributing to clumsiness and poor motor control.
• Skin Appearance: Skin often appears pale or bluish (cyanotic) and is cold to the touch.

Comparison of Hypothermia Stages

Vital Sign	Mild Hypothermia (32–35°C / 90–95°F)	Moderate Hypothermia (28–32°C / 82.4–90°F)	Severe Hypothermia (<28°C / <82.4°F)
Core Temperature	32–35°C	28–32°C	<28°C
Shivering	Vigorous	Stops (<30-32°C)	Absent
Heart Rate	Fast (Tachycardia)	Slow (Bradycardia)	Very slow, arrhythmias, possible arrest
Blood Pressure	High (Hypertension)	Low (Hypotension)	Markedly low or undetectable
Breathing	Fast (Tachypnea)	Slow (Bradypnea)	Slow, shallow, or absent
Mental State	Confused, clumsy	Lethargic, stuporous, amnesia	Unconscious, comatose
Reflexes	Normal/Decreased	Hyporeflexia	Areflexia, pupils fixed and dilated

ECG Changes Associated with Moderate Hypothermia

Beyond the basic vital signs, an electrocardiogram (ECG) can reveal specific electrical abnormalities in a moderately hypothermic heart. The characteristic ECG changes include:

• Prolonged Intervals: All electrical intervals, including PR, QRS, and QT, are prolonged due to the generalized slowing of cardiac impulse conduction.
• Osborn Wave (J wave): A unique, dome-shaped deflection at the QRS-ST junction, which is particularly prominent in the precordial leads. While not exclusive to hypothermia, its presence in a cold patient is highly characteristic.
• Arrhythmia Progression: Patients are susceptible to arrhythmias, with atrial fibrillation being a common finding before temperatures drop to more dangerous levels where ventricular fibrillation can occur.

Management and Treatment

First Aid

• Gentle Handling: Minimize movement, as jarring motions can trigger ventricular fibrillation in the cold, irritable heart.
• Remove from Cold: Move the patient to a warm, dry environment. If that is not possible, shield them from wind and cold and place them on an insulated surface.
• Remove Wet Clothing: Cut away or gently remove any wet clothes to prevent further heat loss through evaporation and conduction.
• Insulate with Blankets: Cover the person with dry blankets or coats, and apply warm, dry compresses to the neck, chest, and groin—the central areas of the body. Avoid applying heat to the arms and legs, as this can force cold blood back to the core, causing a dangerous drop in core temperature.
• Warm, Sweet Fluids: If the person is conscious and can swallow, offer them a warm, non-alcoholic, non-caffeinated drink.

Medical Treatment

Medical care for moderate hypothermia focuses on active rewarming techniques:

1. Warm intravenous (IV) fluids: Warmed saline solution is administered to help rewarm the blood.
2. Airway Rewarming: Humidified and warmed oxygen can be given through a mask or nasal tube.
3. Active External Rewarming: Techniques like forced-air warming blankets are used to apply heat to the patient's skin.
4. Blood Rewarming: In more severe or unresponsive cases, procedures like hemodialysis or cardiopulmonary bypass may be used to warm the blood externally.

Complications of Moderate Hypothermia

Without prompt and effective treatment, moderate hypothermia can lead to severe and potentially fatal complications, including:

• Cardiac arrest
• Respiratory depression and failure
• Increased risk of life-threatening arrhythmias
• Liver and kidney damage
• Metabolic issues like acidosis
• Neurological damage, potentially leading to coma or lasting cognitive impairment
• Coagulopathy, a bleeding disorder resulting from impaired blood clotting

For more information on the guidelines for treating hypothermia, consult the resources provided by the American Academy of Family Physicians, such as their article on Diagnosis and Treatment of Hypothermia.

Frequently Asked Questions

At what body temperature does moderate hypothermia occur?

Moderate hypothermia is defined by a core body temperature between 28 and 32°C, which is 82.4 to 90°F.

What happens to the heart rate in moderate hypothermia?

In moderate hypothermia, the heart rate slows down, a condition known as bradycardia. The cooled myocardium also becomes more susceptible to dangerous arrhythmias, like atrial fibrillation.

Do patients still shiver in moderate hypothermia?

No, a key sign of moderate hypothermia is that the body stops shivering. This happens once the core temperature drops below 30-32°C (86-90°F), indicating a failure of the body's primary heat-generating mechanism.

What are the common mental signs of moderate hypothermia?

Neurological signs in moderate hypothermia include lethargy, confusion, amnesia, and stupor. Patients may lose the ability to think clearly, and in some cases, experience paradoxical undressing.

What is the risk of paradoxical undressing in moderate hypothermia?

Paradoxical undressing is a phenomenon occurring in moderate and severe hypothermia where a disoriented person removes their clothing. This is extremely dangerous as it accelerates heat loss.

How do doctors diagnose moderate hypothermia?

Diagnosis is made by taking a patient's core temperature using a low-reading thermometer and observing clinical symptoms. An ECG may also be performed to check for characteristic electrical changes.

What are the first aid steps for someone with moderate hypothermia?

The main first aid steps are to gently move the person out of the cold, remove any wet clothing, insulate them with dry blankets, and apply warm, dry compresses to the central body areas (neck, chest, groin). Avoid jarring movements.