Autoregulation Of Cerebral Perfusion Pressure 5e4u6u

Cerebral Autoregulation

Monroe-Kelly Doctrine The doctrine that the central nervous system and its accompanying fluids are enclosed in a rigid container whose total volume tends to remain constant. An increase in volume of one component (e.g., brain, blood, or cerebrospinal fluid) will elevate pressure and decrease the volume of one of the other elements.

Terminology • Cerebral Perfusion Pressure : P = MAP - I The pressure gradient acting across the cerebrovascular bed and, therefore, a major factor in determining cerebral blood flow (CBF) • Cerebral Blood Flow (CBF) Blood supply to the brain in a given period of time • Mean Arterial Pressure Average arterial pressure during a single cardiac cycle • Intracranial Pressure The pressure inside the skull and thus in the brain and cerebrospinal fluid

Terminology

Morton R., Ellenbogen RG. 2005. Intracranial hypertension: Principle of Neurological Surgery, Third edition. USA. Elsevier Saunders. p. 311-23

Cerebral Blood Flow (CBF) Blood supply to the brain in a given period of time

CBF of 50 mL/100 g/min CBF of 25 mL/100 g/min CBF of 15 mL/100 g/min CBF of 6 to 15 mL/100 g/min CBF of less than 6 mL/100 g/min

: Normal : Electroencephalogram slowing : Isoelectric electroencephalogram : Ischemic penumbra : Neuronal death

Morton R., Ellenbogen RG. 2005. Intracranial hypertension: Principle of Neurological Surgery, Third edition. USA. Elsevier Saunders. p. 311-23

Cerebral Autoregulation Autoregulation is a process of adjustment on the part of the brain’s arterioles that keeps cerebrovascular resistance constant over a range of P. Increased P causes stretching of the walls of the arterioles, which compensate by dilating and relieving this pressure. Likewise, in the setting of decreased pressure, the arterioles constrict to maintain P. This autoregulation prevents transient pressure increases from being transmitted to smaller distal vessels. When the MAP is less than 65 mm Hg or greater than 150 mm Hg, the arterioles are unable to autoregulate, and blood flow becomes entirely dependent on the blood pressure, a situation defined as "pressure-ive flow." The CBF is no longer constant but is dependent on and proportional to the P.

Factors Affecting Cerebral Vasculature

Morton R., Ellenbogen RG. 2005. Intracranial hypertension: Principle of Neurological Surgery, Third edition. USA. Elsevier Saunders. p. 311-23

Autoregulation Normal Condition vs Pathological Condition

Morton R., Ellenbogen RG. 2005. Intracranial hypertension: Principle of Neurological Surgery, Third edition. USA. Elsevier Saunders. p. 311-23

Effect of hypercapnia on cerebral autoregulation

Hypercapnia affect the curve, the plateau ascends and shortens, the lower limit shift rightward, and the upper limit leftward

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