9.15. HYPOTHERMIA/IMPACT OF COLD ENVIRONMENT

Related titles

Hypothermia, frostbite, damage caused by cold.

Purpose of assistance

1. Maintenance of stable hemodynamics.
2. Prevention of further heat loss.
3. Warming the patient by safe methods.
4. Proper control of hypothermia, including circulatory arrest caused by it.
5. Prevention of limb loss.

Description of the patient

1. A patient may suffer from hypothermia as a result of being in a cold environment (increased heat loss) or in the presence of a disease or injury that, in combination with exposure to a cold environment (heat loss combined with reduced heat production), leads to hypothermia.
2. The patient may suffer from cold (hypothermia) or localized effects (for example, frostbite).
3. Patients with mild hypothermia will have a normal level of consciousness, shivering, and have normal vital signs. Patients with moderate to severe hypothermia will have an altered state of consciousness, gradual disappearance of tremors, and progressive bradycardia, hypotension, and worsening respiratory status.
4. In patients with frostbite, numbness of the affected area of the body gradually develops with the simultaneous presence of a sensation of “sealing” along the whitened skin, late signs of frostbite include “woodiness” of the skin to the touch, decreased or loss of sensitivity, blistering, white and waxy color of the skin on the affected area.

Inclusion criteria

Patients with systemic or localized damage caused by cold.

Exclusion criteria

1. Patients without cold lesions.
   OR
2. Patients affected by cold, but without symptoms of hypothermia or frostbite.

Management of the patient

Status assessment

1. Assessment of the condition should begin with an initial examination, attention is paid to signs of insufficient blood circulation and ensuring effective ventilation:

a) with moderate or severe hypothermia, there may be a significant change in vital signs, including a weak and extremely slow pulse, marked hypotension and respiratory depression;
b) the rescuer may need more time to examine a patient with hypothermia compared to a person without hypothermia (the examination can take 60 seconds or more).

2. Anamnesis – in addition to standard data collection according to the SAMPLE scheme, additional information about the patient’s condition should include data on:

a) presence of associated damage and injuries;
b) duration of exposure to cold environment;
c) ambient air temperature;
d ) provided treatment before the arrival of EMD workers.

3. There are several ways to categorize the severity of hypothermia, depending on body temperature or clinical signs. If possible, rescuers should measure the patient’s basal body temperature and assign the patient to one of the following levels of hypothermia:

a) mild hypothermia: normal body temperature 35-32.1°C;
b) moderate hypothermia: 32°-28°C;
c ) severe hypothermia: – 28°-24°C;
d) deep: less than 24°C.

4. Equally important is the patient’s clinical picture and the patient’s signs or symptoms – the above temperature-based categorization should be balanced against these clinical findings:

a) mild hypothermia – vital signs and consciousness are normal, there is no shivering, the body is able to maintain heat on its own;
b) medium/severe hypothermia – progressive bradycardia, hypotension, slowing of breathing, change of consciousness with gradual onset of coma, cessation of shivering with moderate hypothermia (usually at a temperature of 30-31°C), general slowing down of body functions; the body loses its ability to thermoregulate.

Treatment and intervention

1. Maintain the safety of the patient and rescuers – the patient is a victim of cold injury and rescuers will likely have to enter the same environment. Keep rescuers safe by preventing exposure to the cold.

2. Control the respiratory tract (according to the instruction “Control of the respiratory tract”).

3. Mild hypothermia:

a) remove the patient from the cold environment, prevent further heat loss by removing wet clothing and drying the skin, and protect from contact with the ground, shelter from wind and moisture, insulate with dry clothes or thermoblankets Cover the patient with a blanket to prevent evaporation of moisture from the surface of the body and, if possible, move the patient to a warm environment;
b) with hypothermia, the need for oxygen decreases, so oxygen therapy may not be necessary.
If necessary, supplemental oxygen – it should be warmed to a temperature of 40-42°C and, if possible, hydrated.
c) provide warm drinks or foods containing glucose, if possible, and the patient is conscious and able to control the breathing process on his own;< br />d) severe shivering can cause an increase in heat production, shivering should be treated by replacing lost calories;
e) apply the following field methods of rewarming – application of heat packs or heat blankets (chemical or electric, as appropriate) to the front wall chest or wrap the chest around if the patient’s chest is large enough – special blankets that heat the air, if available, they are an effective method of warming in field conditions;
e) constantly monitor the condition – in case of a decrease in body temperature or suppression of consciousness;
e) provide IV access:

• • • • indications for IV injections and infusions in mild hypothermia are the same as for patients without hyperthermia;
      • fluids for infusion should be warmed, ideally to a temperature of 42°C;
      • bolus therapy is more suitable than drip;
      • the recommended fluid for volume replacement in a patient with hypothermia is normal saline;

e) if the state of consciousness changes, check the glucose level and provide appropriate help (see the guidelines “Hypoglycemia” or “Hyperglycemia”) and evaluate the presence of other reasons for the change of consciousness:

• • • • transport to the department where it is possible to warm the patient.

4. Moderate or severe hypothermia:

a) assess the state of the respiratory tract, breathing, circulation; checking the pulse in case of hypothermia should take 60 seconds; if possible, measure body temperature in the presence of signs of moderate/severe hypothermia:

• • • • the most accurate way to measure temperature is an esophageal probe (if available), the patient’s airway must be protected and the rescuer must be able to insert the probe;
      • if it is impossible to measure the esophageal temperature, use an ear thermometer, which is specially designed for use at the pre-hospital stage and has a disposable earpiece;
      • rectal thermometers can also be used, but only in a warm environment, rectal thermometers are not a reliable indicator and should therefore only be used in a warm environment (for example, in a warm ambulance);

b) control the airway, if necessary:

• • • • when providing assistance, do not allow hyperventilation, as it lowers the threshold for the onset of ventricular fibrillation in hypothermia;
      • indications and contraindications for the use of additional methods of recovery and ensuring the patency of the respiratory tract in hypothermic patients are the same as for other patients;

c) prevent further heat loss by removing wet clothes and drying the skin, protection from contact with the ground, shelter from wind and moisture, warming with dry clothes or a thermal blanket. Cover the patient with a blanket that prevents evaporation of moisture from the body and, if possible, move the patient to a warm environment;
d) apply field methods of warming – applying heat packs or heat blankets (chemical or electric, if appropriate) to the front wall of the chest cages or wrap around the chest if the patient’s chest is large enough:

• • • • chemical or electrical heat sources should not come into direct contact with the skin;
      • create a barrier between the skin and the heat source to avoid burns;
      • special air-heating blankets, if available, are an effective method of warming in the field;

g) work with the patient carefully:

• • • • try to keep the patient in a horizontal position, it is important to limit the movement of the limbs to avoid increasing the outflow of cold blood to the heart;
      • immediately after entering a warm environment, you should cut off your clothes (instead of removing them by moving your limbs);
      • move the patient only in cases where it is necessary to move the patient away from heat sources;

e) apply cardiac monitoring or an external automatic defibrillator (if available);
e) provide IV access and introduce warmed saline, repeat the infusion if necessary;
g) if the state of consciousness changes, check the glucose level and provide appropriate help (see the instructions “Hypoglycemia” or “Hyperglycemia”) and evaluate the presence of other causes of the change of consciousness;
g) transport as soon as possible to a hospital with available facilities for resuscitation measures. If cardiac arrest occurs, transport to a center with cardiopulmonary bypass or cardiopulmonary bypass (if available);
c) warm the ambulance interior to 24°C during transport.

5. Frostbite.
If there are signs of frostbite and the need for evacuation/transportation for examination and treatment, avoid warming the extremities until definitive treatment is possible. Additional damage occurs as a result of reheating followed by re-return to a cold environment. Carry out rewarming in the absence of a further situation of return to a cold environment:

a) if warming is possible, use circulating warm water (37-39°C) to warm the affected area of the body until it is fully warmed up. If warm water is not available, rewarm by touching the frostbitten limb to an unaffected part of the body. Do not rub the affected areas;
b) after warming, cover the affected areas with a sterile bandage. If the blisters present are painful and the rescuer is experienced, they can be aspirated but not ruptured. Avoid repeated freezing of affected areas. Provide care according to the “Pain Control” guideline.

Patient safety

1. Given the additional effects of additional cold stress, the patient should be removed from the cold environment as soon as possible.
2. It is critical that patients with moderate to severe hypothermia not be allowed to stand or exercise as this can lead to circulatory collapse.
3. Devices that self-generate heat (e.g. heating packs) should be wrapped with something to avoid direct contact with the skin during use to prevent burns. Available evidence suggests that heating packs with a peak temperature above 45°C can cause burns. If the patient is unconscious or unable to recognize progressive damage, periodically check the surface under the warming pack for possible tissue damage.

Useful information for training

Key points

Cardiac arrest precautions.

1. The following are contraindications for resuscitation in case of hypothermia:

a) clear signs of fatal injury (for example, decapitation);
b) presence of signs of total frostbite (presence of ice formations in the respiratory tract);
c) strong rigidity of the chest walls, which does not allow their compression;
d) danger for rescuers from physical fatigue;
g) snow avalanche victims who were under rubble for more than 35 minutes and with obstruction of the respiratory tract by ice or snow.

2. Static and dilated pupils are a clear sign of cadaveric asphyxiation and other signs of death may not be contraindications for CPR in patients with severe hypothermia.

3. The basis of therapy for severe hypothermia and cardiac arrest should be effective chest compressions and rewarming.
The frequency of chest compressions should be the same as in normal patients.

4. The temperature at which defibrillation should first be performed in severely hypothermic patients with cardiac arrest and the number of defibrillation attempts is unclear. There are different approaches to resuscitation in cardiac arrest in patients with hypothermia:

a) According to the American Heart Association (AHA) guidelines, if the patient has a shockable rhythm (ventricular fibrillation/ventricular tachycardia), defibrillation should be attempted. It is appropriate to continue defibrillation attempts according to AAC protocols simultaneously with rewarming strategies;defibrillation once, followed by chest compressions for 2 minutes and then checking the pulse and heart rhythm:

• • • • if a defibrillation attempt is unsuccessful and the patient’s body temperature is below 30 degrees, do not make a new defibrillation attempt until the body temperature is raised above 30°C;
      • continue CPR and rewarming measures;

c) an alternative strategy, according to the Wilderness Medical Society guideline for hypothermia, suggests that if the patient’s core temperature is below 30°C, try defibrillation once and then wait until the patient has warmed at least 1°-2°C or up to 30°C before attempting additional shocks. It is noted that the probability of successful defibrillation increases with each increase in temperature by 1°C;
d) if defibrillation is unsuccessful, but the body temperature is above 30 degrees, follow the protocols as when working with other patients;
e) if defibrillation is unsuccessful and the patient’s core temperature is above 30°C, follow the guideline for patients with a normal temperature; rhythm (other than ventricular tachycardia/ventricular fibrillation) and no pulse, do not start CPR and monitor indicators:

• • • • although this may represent pulseless electrical activity, it may also represent situations where the patient’s pulse is not detectable but remains effective due to reduced metabolic demands;
      • in the case of EDP, the rhythm will quickly deteriorate to asystole, then start CPR;
      • given the likelihood of ventricular fibrillation due to indirect cardiac massage, protocols recommend that it is better to maintain effective cardiac activity than to initiate CPR and cause ventricular fibrillation.

5. Support the patency of the respiratory tract (according to the guideline “Cardiac arrest”):

a) in the absence of means of professional airway patency, carry out auxiliary ventilation with the same frequency as for other patients;
b) in case of intubation, ventilate with less half rate to prevent hyperventilation.
If an ETCO2 monitor is available, ventilate to maintain normal ETCO2 levels.

6. There is little evidence to guide medication use in severe hypothermia with cardiac arrest, however, the 2010 AAC Update to Professional Cardiac Life Support recommends using vasopressors according to standard ACLS protocols, while the 2014 State of Alaska and Wilderness Medical patient management guidelines with hypothermia, it is recommended to stop taking drugs until the patient’s temperature rises above 30°C.
If the body temperature is above 30 degrees, you need to double the intervals between the administration of drugs until the body temperature rises to 35 degrees – from this moment, you can use the usual drug administration intervals.

7. After restoration of spontaneous circulation, provide care according to the guideline “Help for adult patients after restoration of spontaneous circulation”.

8. With severe hypothermia and circulatory arrest, there is still the possibility of successful resuscitation even after prolonged collapse, and survival with subsequent preservation of neurological function has been observed even after prolonged resuscitation.
Patients cannot be declared dead until rewarming has been performed.

9. If the patient’s heart stopped during hypothermia and he was in a state of hypothermia for a long time between the stop and the start of resuscitation, then there is no point in starting resuscitation and rewarming procedures.

Corresponding evaluation results

1. Identification of associated traumatic injuries (if any).
2. Detection of localized frostbite.
3. The patient’s body temperature (if possible to measure).

Key elements of documentation

1. Duration of exposure to a cold environment.
2. Air temperature around and recent temperature changes.
3. Attempts to rewarm or carry out other therapies before the arrival of the EMD team.
4. Consumption of alcohol/narcotic substances by the patient.

Criteria for the effectiveness of aid provision

1. Measurement of the patient’s body temperature and methods of measurement.
2. Presence of cardiac arrhythmias.
3. DПеревод documentation of related injuries (if any).
4. Glucose level analysis.