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Fever during Anesthesia. Speaker: Guo, Shu-Lin Date: 2003-12-09. Thermoregulation. Thermoregulatory response: a core temperature that triggers physiological defenses against excessive heat or cold Inter-threshold range: the difference between the sweating and vasoconstriction thresholds.

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fever during anesthesia

Fever during Anesthesia

Speaker: Guo, Shu-LinDate: 2003-12-09

thermoregulation
Thermoregulation
  • Thermoregulatory response:a core temperature that triggers physiological defenses against excessive heat or cold
  • Inter-threshold range:the difference between the sweating and vasoconstriction thresholds
thermoregulation3
Thermoregulation
  • Setpoint:the normal inter-threshold range is only a few tenths of a degree centigrade
role of fever
Role of Fever
  • Pathphysiology:the pyrogenic stimulation activates hypothalamic thermoregulatory control centers
  • Elevation of setpoint:a synchronous elevation in the cold-response and warm-response threshold
role of fever6
Role of Fever
  • Kluger et al. Science. 1975
    • Method: the desert iguana infected with bacteria
    • Result: a clear correlation between the increase in body temperature after bacterial infection and the host survival rate
role of fever7
Role of Fever
  • Vaughum et at. Brain Research Bulletin 1998
    • Method: rabbit with fever
    • Result: antipyretic use reduced body temperature and significantly decreased the host survival rate
role of fever8
Role of Fever
  • Disadvantage:
    • Increasing cardiac output, oxygen consumption and energy consumption
    • Antipyretic use timing:the elderly or patients with poor cardiac or pulmonary function
process of fever
Process of Fever
  • Thermoregulatory control
    • Neuron-mediated primarily
      • Vagal afferent pathways
    • Humoral mediators
      • The major endogenous pyrogens
        • Interlukin-1
        • Interlukin-6
        • Tumor necrosis factor (TNF-alpha)
        • Interferon-alpha
process of fever10
Process of Fever
  • Process of fever
    • The core temperature elevates
    • All thermoregulatory response thresholds also elevate
    • Cold-defenses are strongly augmented
    • The maximal temperature usually dose not exceed 42°C
process of fever11
Process of Fever
  • Antipyretics:
    • Pyrogens vs. antipyretics (cryogens)
    • Endogenous antipyretics:
      • Interleukin-10
      • Glucocorticoids
      • Vasopression
      • Melanocyte-stimulating hormone (alpha-MSH)
      • Nitric oxide
fever during anesthesia13
Fever during Anesthesia
  • Thermoregulatory control during anesthesia
    • Volatile anesthetics, propofol, opioids and sedatives:
      • Slightly increase the sweating threshold
      • Markedly decreasing the vasoconstriction and shivering thresholds
      • Inter-threshold range increases to 2-4°C
volatile anesthesia and fever
Volatile Anesthesia And Fever
  • Fever is relatively rare during general anesthesia
  • The general anesthesia attenuates fever by the lowering of thermoregulatory threshold of cold defences
volatile anesthesia and fever15
Volatile Anesthesia And Fever
  • Negishi et al. Anesthesiology 1998
    • Method: desflurane and IL-2 induced fever
    • Result: 1.0 MAC essentially obliterating the temperature increase by IL-2
volatile anesthesia and fever17
Volatile Anesthesia And Fever
  • Lenhardt et al. Anesthesiology 1999
    • Methods: measure the thresholds of IL-2 induced fever and general anesthesia
    • Result: the combination of IL-2 administration and desflurane increased the sweating threshold and reduced the vasoconstriction threshold compared to IL-2 alone
volatile anesthesia and fever19
Volatile Anesthesia And Fever
  • Peripherally mediated inhibition by desflurane anesthesia
    • Desflurane did not affect the plasma concentrations of the circulating cytokines induced by IL-2
    • Desflurane decreases the thermoregulatory thresholds of cold defenses via central action
intravenous anesthesia and fever
Intravenous Anesthesia And Fever
  • Roytblat et al. A&A 1998
    • Before cardiac pulmonary bypass, ketamine (0.25mg/kg) reduces serum IL-6 concentration during and post surgery
  • Crozier et al. BJA 1994
    • Alfentil and propofol diminishes release of IL-6 during abdominal surgery
opioids and fever
Opioids And Fever
  • Opioids administration increases warm-response thresholds and decreases cold-response thresholds
  • The pattern of inhibition is similar to that produced by general anesthesia though the magnitude is somewhat low
opioids and fever22
Opioids And Fever
  • Opioids also suppress fever in a dose-dependent fashion
  • Opioids use in ICU or during the post-operation period need to be aware
neuraxial anesthesia and fever
Neuraxial anesthesia and Fever
  • Re-distribution is a major cause of core hypothermia during epidural and spinal anesthesia
  • The BT loss rate is determined by the inequality between heat loss and heat productions well as block level
neuraxial anesthesia and fever24
Neuraxial anesthesia and Fever
  • With neuraxial anesthesia peripheral nerve block is a more important cause of hypothermia
  • Sufficient core hypothermia will trigger vasoconstriction and shivering even during neuraxial anesthesia, but only in the unblocked areas
neuraxial anesthesia and fever25
Neuraxial anesthesia and Fever
  • Epidural analgesia is frequently associated with hyperthermia, especially during labor and post-operative period
  • The paradoxical hyperthermia often prompts clinical interventions such as work-up for infection and newborn sepsis
neuraxial anesthesia and fever26
Neuraxial anesthesia and Fever
  • During epidural analgesia, the sweating threshold slightly increases
  • Epidural pain control vs intravenous pain control
paralysis and fever
Paralysis And Fever
  • Paralysis prevents shivering and the associated increase in metabolic heat production
  • Paralysis can reduce the magnitude of fever, but clinically its effect seems to be less important than anesthetic-induced inhibition of fever
post operative fever
Post-operative Fever
  • A positive relationship between the post-operative increase in core temperature and plasma IL-6 concentration
treatment of fever
Treatment of Fever
  • Most febrile patients are treated with antipyretic, mainly for patients comfort
  • Fever should be treated in patients with cardiopulmonary dysfunction, acute brain stroke or injury, or in those whose temperature above 40°C
treatment of fever32
Treatment of Fever
  • Active cooling does not reduce core temperature, but increases the metabolic rate, activates the autonomic system, and provokes thermal discomfort
treatment of fever33
Treatment of Fever
  • Fever occurs in almost half of the patients with acute brain stroke or injury
  • Mild brain hyperthermia worsens the functional outcome by enhancing neurotransmitter release, exaggerating oxygen radical production, and extending blood-brain barrier breakdown