title: Elevated thermostatic setpoint in postoperative patients.
abstract: BACKGROUND
  The mechanism and clinical relevance of increased core temperature (Tc) after surgery are poorly understood. Because fever is used as a diagnostic sign of infection, it is important to recognize what constitutes the normal postoperative thermoregulatory response. In the current study the authors tested the hypothesis that a regulated increase in Tc setpoint occurs after surgery.
  
  
  METHODS
  The authors prospectively studied 271 patients in the first 24 h after a variety of vascular, abdominal, and thoracic surgical procedures. Tc measured in the urinary bladder, skin-surface temperatures, thermoregulatory responses (vasoconstriction and shivering), and total leukocyte counts were assessed. In a subset of 34 patients, plasma concentrations of tumor necrosis factor, interleukin (IL)-6, and IL-8 were measured before and after surgery.
  
  
  RESULTS
  In the early postoperative period, the maximum increase in Tc above the preoperative baseline averaged 1.4 +/- 0.8 degrees C (2.5 +/- 1.4 degrees F), with the Tc peak occurring 11.1 /- 5.8 h after surgery. Fifty percent of patients had a maximum Tc greater than or equal to 38.0 degrees C (100.4 degrees F) and 25% had a maximum Tc greater than or equal to 38.5 degrees C (101.3 degrees F). The progressive postoperative increase in Tc was clearly associated with cutaneous vasoconstriction and shivering, indicating a regulated elevation in Tc setpoint. The elevated Tc was associated with an increased IL-6 response but not with leukocytosis. Maximum postoperative Tc was positively correlated with duration and extent of the surgical procedure.
  
  
  CONCLUSIONS
  A regulated elevation in Tc setpoint (fever) occurs normally after surgery. The association between Tc elevation, extent and duration of surgery, and the cytokine response suggests that early postoperative fever is a manifestation of perioperative stress.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA. sfrank@welch.jhu.edu
authors.forename: S M
authors.initials: SM
authors.lastname: Frank
authors.forename: M J
authors.initials: MJ
authors.lastname: Kluger
authors.forename: S L
authors.initials: SL
authors.lastname: Kunkel
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D001833:Body Temperature Regulation / Q000502:physiology*; D005260:Female; D005334:Fever / Q000097:blood / Q000503:physiopathology*; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D016209:Interleukin-8 / Q000097:blood; D007958:Leukocyte Count; D008297:Male; D012768:Shivering / Q000502:physiology; D013514:Surgical Procedures, Operative; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014661:Vasoconstriction
chemical_list: D015415:Biomarkers; D015850:Interleukin-6; D016209:Interleukin-8; D014409:Tumor Necrosis Factor-alpha