The human body maintains a stable core temperature around 98.6°F (37°C) through thermoregulation. A drop below this range, known as hypothermia, can signal a serious health issue, particularly for individuals with cancer. In cancer patients, hypothermia is not always caused by external cold exposure. It frequently arises from the disease itself or necessary medical interventions, making it a potentially life-threatening complication requiring immediate attention.
Clinical Definition of Low Body Temperature
Hypothermia is clinically defined as a core body temperature falling below 95°F (35°C). Severity is based on specific temperature thresholds. Mild hypothermia is classified as 90°F (32°C) to 95°F (35°C), often causing shivering and mild confusion. Moderate hypothermia ranges from 82°F (28°C) to 90°F (32°C), where shivering usually stops and confusion increases.
Even mild drops in core temperature have serious physiological consequences, particularly affecting the cardiovascular system and blood clotting. As the body cools, heart rate slows and cardiac contractility decreases, increasing the risk of irregular heart rhythms like ventricular fibrillation below 82.4°F (28°C). Hypothermia also impairs the clotting cascade and platelet function, leading to a higher risk of bleeding.
Direct Effects of Cancer on Thermoregulation
Cancer can directly interfere with the body’s ability to generate and maintain heat. A primary mechanism is cancer cachexia, a severe wasting syndrome involving the loss of skeletal muscle and fat tissue. Since skeletal muscle is the primary site of metabolic heat production, its loss dramatically reduces the body’s capacity for thermogenesis.
Cachexia also disrupts the body’s energy balance, often increasing resting energy expenditure. This hypermetabolic state is partly driven by the activation and browning of white adipose tissue, which generates heat by uncoupling energy production from ATP synthesis. Although this process generates heat, the overall depletion of energy stores and muscle mass compromises the patient’s ability to maintain core temperature long-term.
In some instances, the tumor itself can directly impair the central thermostat in the brain’s hypothalamus. Tumors located near the suprasellar region, such as craniopharyngiomas, can damage the hypothalamic nuclei responsible for regulating body temperature. This damage causes profound dysregulation, potentially leading to abnormally high temperatures or an inability to generate heat effectively.
Systemic inflammation is another mechanism disrupting temperature control. The tumor and host immune response release signaling proteins called cytokines, such as Tumor Necrosis Factor-alpha (TNF-\(\alpha\)). While some cytokines typically cause fever by resetting the hypothalamic set point upward, a specific balance of these inflammatory mediators can sometimes suppress the set point, creating a state of regulated hypothermia.
Secondary Factors Contributing to Lowered Core Temperature
Factors associated with cancer care can indirectly lead to a drop in core temperature. Certain chemotherapy drugs, notably oxaliplatin, cause chemotherapy-induced peripheral neuropathy (CIPN). This nerve damage leads to cold dysesthesia, an extreme sensitivity where exposure to cold temperatures or drinks causes pain, numbness, and an exaggerated sensation of cold.
While cold sensitivity does not always cause hypothermia, the associated vasoconstriction reduces heat distribution and contributes to feeling cold. Furthermore, sepsis, a severe systemic infection, poses a significant risk to immunocompromised patients. Sepsis often begins with a fever, but failure of compensatory mechanisms can lead to a rapid, life-threatening drop into hypothermia below 96.8°F (36°C). Hypothermia during sepsis signals a severe inflammatory response and is a poor prognostic sign.
Nutritional deficiencies and anemia also lower the body’s thermal reserves. Cancer-related anemia reduces the blood’s capacity to transport oxygen, which is necessary for heat-generating metabolic processes. Severe malnutrition, often linked to cachexia, depletes energy stores like fat and muscle needed to fuel non-shivering thermogenesis.
Monitoring and Management of Hypothermia
Monitoring body temperature is a frequent practice for cancer patients, often using a reliable digital thermometer at least twice a day. Many standard thermometers may not accurately read temperatures below 95°F (35°C); therefore, a reading at the low end of the device’s range should prompt immediate concern. Early detection is important because hypothermia progresses quickly, especially in patients with reduced metabolic reserves.
If a low temperature is detected, immediate passive rewarming techniques should be employed while seeking medical help. Move the patient to a warm, dry environment, and gently remove any wet clothing to prevent further heat loss. Insulate the body with layers of dry blankets, coats, or newspaper, focusing on core areas like the neck, chest, and groin.
If the patient is alert and able to swallow, offering warm, sweet, non-alcoholic fluids can help raise the core temperature internally. Avoid applying direct heat, such as heating pads, to the arms and legs. This can cause cold blood to rapidly return to the core, leading to a sudden and dangerous drop in core temperature. Seek emergency medical care immediately if the temperature drops below 95°F (35°C), or if the patient experiences confusion, slurred speech, or loss of consciousness.