Draw a graph to demonstrate cerebral autoregulation? How does this change in hypertensive patients?

  • Cerebral blood flow is autoregulated between a MAP of 50 – 150 mmHg
    • Outside the autoregulatory range:
      • When MAP >150 mmHg CBF becomes directly proportional to CPP
      • When MAP falls <50 mmHg CBF falls proportionally below the ‘normal’ value of 50 mL/100 g/min, resulting in ischaemia
    • In hypertensive patients autoregulation occurs between a higher range of pressures (60 and 160 mmHg)
  • Can be displayed using an autoregulation curve:
    • Represents an oversimplification of the true relationship
    • In vivo changes in perfusion pressure may be regional and there is not a neat linear relationship at each end of the curve
Effects of cerebral autoregulation, demonstrating the relationship between cerebral perfusion pressure and cerebral blood flow