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Cerebral blood flow and metabolism in severely head-injured children. Part 2: Autoregulation
J P Muizelaar1, J D Ward, A Marmarou
1Department of Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond.
Insights
Cerebral blood flow autoregulation was assessed in pediatric severe head injury patients. Impaired autoregulation was linked to abnormal cerebral blood flow levels, not clinical factors, impacting intracranial pressure management.
Area of Science:
- Neurology
- Critical Care Medicine
- Pediatric Neuroscience
Background:
- Severe head injury in children poses significant management challenges.
- Cerebral blood flow (CBF) autoregulation is crucial for maintaining brain perfusion.
- Understanding autoregulation is vital for optimizing treatment strategies in pediatric head trauma.
Purpose of the Study:
- To evaluate the autoregulation of cerebral blood flow in pediatric patients with severe head injury.
- To correlate CBF autoregulation with clinical status, outcome, and intracranial pressure (ICP).
- To investigate the impact of blood pressure manipulation on CBF and ICP in this patient cohort.
Main Methods:
- Utilized 133Xe to measure CBF in 26 pediatric patients with severe head injury.
- Manipulated blood pressure using phenylephrine and trimethaphan camsylate.
- Correlated CBF with Glasgow Coma Scale (GCS) score, outcome, ICP, pressure-volume index (PVI), and injury site determined by evoked potentials.
Main Results:
- Autoregulation was intact in 59% of measurements.
- Impaired autoregulation was significantly associated with CBF levels outside -2 to +2 standard deviations from normal.
- No correlation found between autoregulation and GCS score, outcome, time post-injury, or injury location.
- Intact autoregulation showed inverse ICP changes with blood pressure manipulation; PVI changed inversely to ICP.
Conclusions:
- Cerebral blood flow autoregulation is frequently impaired in pediatric severe head injury.
- Abnormal CBF levels, rather than clinical parameters, are indicators of autoregulation dysfunction.
- Findings have implications for managing intracranial pressure through blood pressure control in pediatric head trauma.
Abstract:
Autoregulation of cerebral blood flow ("CBF15") was tested in a series of 26 pediatric patients (mean age 13.2 years) with severe head injury (average Glasgow Coma Scale (GCS) score 5.5) in the acute stage. A baseline 133Xe CBF measurement was performed and then repeated, after blood pressure was increased by 29% with intravenous phenylephrine or decreased by 26% with intravenous trimethaphan camsylate. Correlations were made between CBF and clinical condition, outcome, time after injury, intracranial pressure (ICP), and pressure-volume index (PVI) changes, and the site of injury (hemispheres, diencephalon, or brain stem). The site of injury was determined with multimodality evoked potential measurements. Autoregulation was intact in 22 (59%) of 37 measurements. There was no correlation with GCS score, outcome, time after injury, site of injury, or way of testing (decreasing or increasing blood pressure). Autoregulation was statistically significantly more often impaired when CBF was either below normal -2 standard deviations (SD) (reduced flow) or above normal +2 SD (absolute hyperemia). In cases with intact autoregulation, mean ICP decreased from 17.5 to 15.0 mm Hg with higher blood pressure and increased from 19.0 to 21.3 mm Hg with lower blood pressure. When PVI was measured during the blood pressure manipulations, it was found to change in a direction opposite to the ICP change. The consequences of these findings in the management of ICP problems with blood pressure control are discussed.