Sepsis is a life-threatening medical emergency arising from the body’s overwhelming and dysregulated response to an infection. While the body typically mounts a fever to fight off pathogens, sepsis can paradoxically lead to an unusually low body temperature, known as hypothermia. This temperature drop is often a serious indicator, signaling a severe progression of the condition.
Sepsis and the Body’s Temperature Control
The human body maintains a stable internal temperature through a process called thermoregulation, primarily controlled by the hypothalamus in the brain. This area acts like a thermostat, constantly receiving signals from temperature receptors throughout the body. When an infection occurs, the immune system releases substances that signal the hypothalamus to raise the body’s set point, leading to a fever. This elevated temperature is a deliberate defensive mechanism, as higher temperatures can inhibit pathogen growth and enhance immune cell function.
In severe sepsis, however, this finely tuned system can become overwhelmed or malfunction. Instead of generating a fever, the body’s temperature control mechanisms can be disrupted, resulting in hypothermia, defined as a core body temperature below 36°C (96.8°F). This shift from fever to hypothermia indicates a profound failure in the body’s ability to regulate its internal environment. Approximately 10-30% of patients with sepsis may present with hypothermia upon admission.
Immune System’s Role in Temperature Drop
The immune system plays a central role in the temperature changes observed in sepsis. In response to an infection, immune cells release a complex array of signaling molecules called cytokines. These include both pro-inflammatory cytokines, which promote inflammation and fever, and anti-inflammatory cytokines, which aim to dampen the immune response. In sepsis, this release becomes dysregulated, leading to an uncontrolled “cytokine storm” where both types of mediators are excessively produced.
While pro-inflammatory cytokines typically induce fever by affecting the hypothalamus, the overwhelming and prolonged release of anti-inflammatory mediators, such as Interleukin-10 (IL-10), can suppress the body’s heat-generating capabilities. This can lead to a state where the immune system becomes exhausted or “paralyzed,” known as immunoparalysis. In this state, immune cells show reduced function and numbers, impacting the body’s ability to regulate temperature. The body may shift from an initial hyper-inflammatory phase to an immunosuppressive phase, contributing to the temperature drop.
Cellular Energy and Blood Flow Changes
Beyond the immune response, metabolic and circulatory disruptions significantly contribute to hypothermia in sepsis. Sepsis leads to widespread cellular dysfunction, particularly affecting the mitochondria. Mitochondria are responsible for producing adenosine triphosphate (ATP), and this process also generates heat. In sepsis, mitochondrial function becomes impaired, reducing the cell’s ability to produce ATP and, consequently, to generate heat.
Furthermore, sepsis severely impacts blood flow throughout the body. The widespread inflammation causes vasodilation, meaning blood vessels widen, leading to a significant drop in blood pressure. This reduced blood pressure and impaired microcirculatory function, where blood flow to the smallest vessels is compromised, results in insufficient oxygen delivery to tissues. Cells become starved of oxygen, further impairing mitochondrial energy production and heat generation. The body’s inability to maintain adequate circulation and cellular energy production prevents it from sustaining its core temperature, leading to hypothermia.
Why Low Temperature Matters
A low body temperature in sepsis is a serious clinical sign. It often reflects a profound failure of the body’s compensatory mechanisms, indicating a more advanced and severe stage of the illness. Patients presenting with hypothermia in sepsis generally experience a higher incidence of organ dysfunction.
Hypothermia in sepsis is associated with significantly increased mortality rates. Studies have shown that patients with hypothermia have a considerably higher risk of death. This symptom suggests that the body is no longer able to mount an effective inflammatory response and is struggling to maintain basic physiological functions.