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The cerebrovascular response to hypocapnia in children receiving propofol

Cengiz Karsli1, Igor Luginbuehl, Bruno Bissonnette

  • 1From the Department of Anesthesia, The Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada.

Anesthesia and Analgesia
|September 24, 2004
PubMed

Insights

Hyperventilation to end-tidal carbon dioxide (ETco(2)) below 30 mm Hg does not further reduce cerebral blood flow velocity in children under propofol anesthesia. This suggests lower ETco(2) targets may not be necessary for managing intracranial pressure.

Area of Science:

  • Pediatric Anesthesiology
  • Neurocritical Care
  • Cerebrovascular Physiology

Background:

  • Hypocapnia is a strategy to reduce intracranial pressure (ICP) during neurosurgery.
  • Cerebrovascular reactivity to carbon dioxide (CCO(2)R) is crucial for managing cerebral blood flow.
  • Previous studies suggested a plateau in CCO(2)R below 35 mm Hg end-tidal carbon dioxide (ETco(2)) in children.

Purpose of the Study:

  • To precisely define the relationship between ETco(2) and cerebral blood flow velocity (V(mca)) in children.
  • To investigate the plateau effect of CCO(2)R at lower ETco(2) levels during propofol anesthesia.
  • To determine the optimal ETco(2) threshold for achieving maximal reduction in V(mca) in pediatric patients.

Main Methods:

  • Utilized transcranial Doppler (TCD) sonography to measure V(mca) in 27 healthy children.
  • Adjusted ETco(2) in small increments (1-2 mm Hg) between 24 and 40 mm Hg.
  • Administered standardized propofol infusion and caudal epidural block for anesthesia.

Main Results:

  • An exponential relationship was observed between ETco(2) and V(mca) above 30 mm Hg (r = 0.82).
  • V(mca) showed no significant change with ETco(2) levels below 30 mm Hg (r = 0.06).
  • No significant alterations in heart rate or arterial blood pressure were noted.

Conclusions:

  • Hyperventilation to ETco(2) below 30 mm Hg may not provide additional benefits in reducing cerebral blood flow velocity in children receiving propofol.
  • Current recommendations for managing intracranial pressure via hyperventilation in this population may be reconsidered.
  • Findings suggest that targeting ETco(2) values above 30 mm Hg is sufficient for achieving maximal cerebrovascular effects under propofol anesthesia in children.

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