Acid-base balance and cerebrovascular regulation

Area of Science:

• Physiology
• Neuroscience
• Acid-Base Balance

Background:

• Intracellular pH regulation is vital for homeostasis.
• Cerebrovascular acid-base balance directly influences cerebral blood flow (CBF), impacting health and disease.
• Acid-base disturbances, like those in COPD and diabetic ketoacidosis, affect CBF regulation.

Purpose of the Study:

• To review classic experimental studies (75+ years) on the integrative relationships between CBF, PCO2, HCO3-, and pH.
• To elucidate how these factors influence acid-base compensatory changes and cerebrovascular responses.
• To propose mechanisms by which arterial HCO3- and extravascular PCO2/pH regulate CBF.

Main Methods:

• Review of historical experimental studies.
• Analysis of integrative relationships between physiological parameters.
• Examination of kinetic exchange between blood, extracellular fluid, and brain tissue.

Main Results:

• Arterial HCO3- alterations contribute to cerebrovascular acid-base regulation during respiratory acidosis/alkalosis.
• CBF regulation is influenced by direct changes in extravascular/interstitial PCO2 and pH, not solely arterial pH.
• CO2 diffusion across the blood-brain barrier is key to altering perivascular extracellular pH.

Conclusions:

• CBF regulation is affected by the severity of metabolic/respiratory disturbances and acid-base compensation.
• CBF regulation is independent of arterial pH; extravascular pH is the critical factor.
• Understanding these relationships can improve CBF regulation in clinical practice for systemic acid-base disorders.