The purpose of this study is to determine whether externally warming critically ill afebrile adult septic patients will improve indices of immune function and/or clinical outcomes.

Inclusion Criteria:

• Admitted to a surgical or medical intensive care unit
• Age greater than 18 years
• Diagnosis of sepsis within 24 hours of enrollment
• Requirement for mechanical ventilation with expected duration of mechanical ventilation > 48 hours
• Goal Richmond Agitation Sedation Scale (RASS) < 0
• Maximum baseline temperature (within previous 24 hours) < 38.3°C

Exclusion Criteria:

• Treatment with chemotherapy within 6 months of enrollment
• Treatment with corticosteroids at a dose > 300 mg/day hydrocortisone (or equivalent)
• History of solid organ transplant on any immunosuppression medication
• History of immunological disease
• History of chronic infection with hepatitis B or C virus
• History of acute stroke, acute coronary syndrome, or severe head injury requiring osmotic therapy within 7 days prior to enrollment
• History of multiple sclerosis
• Contraindications to both bladder or esophageal core temperature monitors or to forced air warming blankets
• Moribund status
• Sepsis without source control