Modification of focal cerebral ischemia by cardiac output augmentation

Area of Science:

• Neurology
• Cardiovascular Physiology
• Experimental Medicine

Background:

• Intravascular volume expansion is a recognized treatment for ischemic stroke.
• The underlying physiological mechanisms, specifically the roles of cardiac output and hemodilution, remain unclear.
• Controlled studies are needed to elucidate these mechanisms.

Purpose of the Study:

• To investigate the effects of cardiac output augmentation versus isovolemic hemodilution on local cerebral blood flow (lCBF) in a primate model of focal cerebral ischemia.
• To determine the physiological basis for successful intravascular volume expansion in treating ischemic stroke.

Main Methods:

• Two groups of anesthetized rhesus monkeys underwent unilateral middle cerebral artery occlusion.
• Extensive cardiovascular monitoring and local cerebral blood flow (lCBF) measurements using the hydrogen clearance method were performed.
• One group received blood volume expansion (Dextran 40), while the other underwent isovolemic hemodilution (Dextran 40) with constant cardiac output.

Main Results:

• Significant increases in lCBF were observed exclusively in ischemic brain regions.
• These lCBF increases were directly correlated with cardiac output augmentation, not blood pressure or viscosity changes.
• Isovolemic hemodilution did not result in any significant changes in lCBF.

Conclusions:

• Ischemic brain regions exhibit selective vulnerability to changes in cardiac output, independent of blood pressure.
• Intravascular volume expansion, through cardiac output augmentation, plays a crucial role in improving cerebral blood flow during acute ischemic stroke.
• These findings support the therapeutic application of volume expansion and cardiac output enhancement in stroke management.