Core Principles and Goals of Medical Hibernation
Therapeutic hypothermia involves artificial, strictly controlled cooling of the body. It can be either systemic (general) or regional (local).
Key objectives of this intervention:
- Substantial reduction in metabolic rate.
- Suppression of the functional activity of tissues, organs, and physiological systems.
- A manifold increase in the resistance of cellular structures to hypoxia (oxygen deprivation).
Application in Surgical Practice
Systemic therapeutic hypothermia is vital during surgical procedures that require temporary cessation or severe reduction of blood flow. These are the so-called operations on 'bloodless' organs (e.g., the heart or brain).
The pathophysiological rationale is that under cold conditions, tissue resistance increases to such an extent that an organ can be completely disconnected from blood supply for several minutes. After the manipulations are completed, its viability and adequate function are fully restored.
Two levels of cooling are distinguished:
- Standard level: the patient's core (rectal) temperature is lowered to 30–28 °C.
- Deep hypothermia: used for prolonged surgical procedures. It requires cardiopulmonary bypass (CPB), muscle relaxants, and specific metabolic inhibitors.
Management of Accidental Hypothermia: An Etiotropic Approach
If hypothermia occurs unintentionally, the rescue strategy depends on the stage of the process. In the compensation stage, it is sufficient to stop cold exposure and warm the person (warm bath, dry warm clothing, heating pads, warm drinks). In the decompression stage, intensive care based on etiotropic, pathogenetic, and symptomatic principles is required.
Etiotropic treatment aims to eliminate the cooling factor. The victim is immediately moved to a warm room, changed into dry clothes, and active rewarming is initiated.
Rewarming methods:
- External.
- Internal (via the stomach, rectum, or lungs).
- Combined (combining external and internal methods yields the greatest effect).
Important rule: Active rewarming must be stopped as soon as the rectal temperature reaches 33–34 °C. Continuing the procedure carries a high risk of hyperthermia, as the thermoregulatory system cannot immediately resume normal function.
Pathogenetic Therapy of Hypothermia
This stage aims to block the pathogenetic mechanisms of the disease process. It includes three main areas:
- Restoration of effective circulation and respiration. Maintaining airway patency (clearing mucus, correcting tongue drop), and performing assisted or mechanical ventilation with air or oxygen-enriched mixtures. In cardiac arrest, chest compressions and defibrillation are indicated. In concurrent blood loss, circulating blood volume is restored (transfusion of blood, plasma, or plasma expanders).
- Correction of acid-base balance (ABR) and fluid balance. Balanced salt and buffer solutions (e.g., sodium bicarbonate) are administered, along with dextran solutions of various molecular weights (Polyglucin, Reopolyglucin).
- Correction of glucose deficit. Glucose solutions of varying concentrations are administered in strict combination with insulin and vitamins.
Symptomatic Treatment and Prevention
Symptomatic therapy combats secondary complications that worsen the patient's condition. Physicians manage severe headaches, normalize diuresis, prevent edema of internal organs and tissues, and treat concurrent medical conditions and frostbite.
To prevent hypothermia (including in hospital settings), it is essential to maintain thermal balance:
- Monitor optimal room temperature and humidity.
- Use dry and warm bedding.
- Warm infusing fluids to body temperature.
- For neonates, use heated bassinets and radiant warmers.