Critical closing pressure in cerebrovascular circulation

Area of Science:

• Neuroscience
• Critical Care Medicine
• Cerebrovascular Physiology

Background:

• Cerebral critical closing pressure (CCP) is a theoretical arterial pressure threshold.
• It is hypothesized to equal intracranial pressure (ICP) plus active cerebral arterial tone.
• Understanding CCP's relationship with ICP and cerebral autoregulation is crucial for managing head injuries.

Purpose of the Study:

• To evaluate the correlation of CCP with ICP, cerebral autoregulation, and other hemodynamic parameters in head-injured patients.
• To determine if CCP can accurately estimate ICP and cerebral perfusion pressure (CPP).
• To assess the predictive value of CCP-ICP for patient outcomes.

Main Methods:

• Daily recordings of ICP, arterial blood pressure (ABP), and middle cerebral artery blood flow velocity in ventilated patients.
• Calculation of CCP, cerebral autoregulation index (Mx), ABP, ICP, and CPP from recorded waveforms.
• Statistical analysis to determine correlations between CCP, ICP, CPP, Mx, and patient outcomes.

Main Results:

• CCP changes reflected ICP variations during plateau and B waves.
• A mild but significant correlation was found between CCP and ICP (R=0.41).
• The CCP-ICP difference significantly correlated with cerebral autoregulation (Mx) and CPP, but not with patient outcomes.

Conclusions:

• CCP is sensitive to ICP and CPP variations but lacks accuracy as an estimator.
• The CCP-ICP difference correlates with cerebral autoregulation but does not predict head injury outcomes.
• CCP is not a reliable clinical tool for estimating ICP or CPP in head-injured patients.