Why does body temperature drop during sepsis?

Why Body Temperature Drops During Sepsis

Body temperature drops during sepsis due to dysregulation of thermoregulatory mechanisms caused by the overwhelming inflammatory response, leading to peripheral vasodilation, altered hypothalamic function, and metabolic derangements that impair heat production.

Pathophysiological Mechanisms of Hypothermia in Sepsis

Thermoregulatory Dysfunction

• Sepsis causes dysregulation of the body's normal temperature control mechanisms, which are primarily regulated by the hypothalamus 1
• The systemic inflammatory response in sepsis can directly affect hypothalamic function, impairing its ability to maintain normal body temperature
• Hypothermia (core temperature <36°C) is recognized as one of the diagnostic criteria for sepsis in major guidelines 1

Hemodynamic Changes

• Peripheral vasodilation occurs during sepsis due to the release of inflammatory mediators
• This vasodilation increases heat loss through the skin surface
• Impaired peripheral vasoconstriction (normally a protective mechanism against cold) contributes to heat loss 1
• Circulatory shock in sepsis reduces tissue perfusion, limiting the body's ability to generate and distribute heat

Metabolic Derangements

• Sepsis can impair cellular metabolism and mitochondrial function
• Reduced metabolic activity leads to decreased heat production
• Severe sepsis may cause a shift from heat-generating processes to conservation of energy as a protective mechanism

Clinical Significance of Hypothermia in Sepsis

Prognostic Implications

• Hypothermia in sepsis is associated with significantly higher mortality rates compared to normothermic or febrile sepsis 2
• The adjusted odds ratio for in-hospital mortality with hypothermia in sepsis is 6.82 (95% CI 3.08-15.22) according to recent research 2
• Up to 30% of patients with severe sepsis may present with hypothermia at triage 2

Natural Course of Hypothermic Response

• Contrary to common perception, hypothermia in sepsis is often transient and self-limiting rather than progressive 3
• The median recovery time from hypothermic episodes is approximately 6 hours 3
• Body temperature rarely falls below 34.0°C during septic hypothermia 3
• Hypothermia appears to be an inherent response in human sepsis rather than simply a terminal event 3

Clinical Approach to Hypothermia in Sepsis

Recognition and Diagnosis

• Hypothermia (<36°C) is a key diagnostic criterion for sepsis according to consensus definitions 1
• 10-20% of patients with hypothermic sepsis may not have other vital sign abnormalities, making temperature monitoring crucial 2
• Bidirectional oscillations in body temperature may be observed during septic episodes 3

Management Considerations

• Do not use targeted temperature management below 36°C in patients with septic shock 1
• Instead, maintain normothermia in septic shock patients 1
• For fluid resuscitation, administer at least 30 mL/kg of crystalloids IV in the first 3 hours 4
• Use advanced methods with servo-regulated cooling if temperature management is needed 1

Distinguishing Features from Other Causes of Hypothermia

• Septic hypothermia differs from environmental hypothermia in its pathophysiology and natural course
• Unlike environmental hypothermia, septic hypothermia is typically self-limiting and rarely severe 3
• Hypothermia in sepsis is not consistently associated with shock or respiratory distress, as nearly half of hypothermic episodes occur in the absence of these conditions 3
• Medications (antipyretics, sedatives, neuroleptics) do not reliably predict the onset of hypothermia in sepsis 3

Understanding the mechanisms and significance of hypothermia in sepsis is crucial for proper patient assessment and management, as it represents an important diagnostic criterion and prognostic indicator that should prompt rapid intervention according to established sepsis management protocols.