Volatile anesthetics, such as isoflurane, sevoflurane, and desflurane, are widely used in modern clinical practice. These agents are known to uncouple the typical flow-metabolism relationship in the brain, which is the mechanism by which cerebral perfusion (CBF) matches the metabolic demands of brain tissue.
Suppression of CMRO2
Volatile anesthetics consistently suppress cerebral metabolic rate of oxygen consumption (CMRO2) in both humans and animals. This reduction in CMRO2 is accompanied by alterations in cerebral blood flow. Studies employing transcranial Doppler (TCD) and gas diffusion techniques generally demonstrate a dose-dependent increase in CBF with volatile anesthetics. However, magnetic resonance imaging (MRI) studies suggest minimal changes in global CBF in humans. In contrast, non-human primates exhibit a dose-dependent increase in CBF under the same conditions.
Variable Effects of Sevoflurane on CBF
Sevoflurane, in particular, has shown conflicting effects on CBF across studies. Some studies report no change in CBF, while others describe both increases and decreases depending on factors such as anesthetic depth and experimental conditions. This variability suggests that the effect of sevoflurane on CBF may depend on its interaction with cerebral vascular resistance mechanisms.
