Propofol is a widely used intravenous anesthetic known for its ability to induce dose-dependent sedation and general anesthesia. Its mechanism of action is primarily through potentiation of GABA receptors, enhancing inhibitory neurotransmission and reducing neuronal excitability. This interaction leads to a reduction in consciousness and, when administered in higher doses, induces general anesthesia.
Propofol exerts significant effects on cerebral perfusion. Compared to volatile anesthetics administered at Bispectral Index (BIS)-equivalent doses, propofol causes a marked reduction in cerebral blood flow (CBF) and a corresponding decrease in cerebral metabolic rate of oxygen consumption (CMRO₂). This decrease is attributed to intact flow-metabolism coupling, meaning the reduction in CBF is matched with the decrease in metabolic demand. Interestingly, in vitro studies have demonstrated that when propofol is applied directly to cerebral vessels, it induces vasodilation, further suggesting that its effect on CBF is not due to direct vasoconstriction but rather reduced metabolic demand.
Importantly, cerebral autoregulation (CA), which maintains stable CBF over a range of blood pressures, remains intact during propofol administration at doses up to 200 μg/kg/min. This ensures that the brain continues to regulate its blood flow despite changes in systemic blood pressure, maintaining adequate perfusion. In practical terms propofol lowers CBF, cerebral blood volume and ICP in a dose-dependent way, down to burst suppression and an isoelectric EEG, where CMRO₂ is roughly halved; because it also lowers MAP, cerebral perfusion pressure has to be defended with vasopressors so the ICP benefit is not lost to hypotension. Although early studies suggested that propofol might blunt vasomotor reactivity (VMR), more recent investigations using near-infrared spectroscopy (NIRS) have shown that the cerebrovascular reactivity to hypocapnia (caused by hyperventilation) is similar for both propofol and volatile anesthetics such as sevoflurane.
Neuroprotective Potential of Propofol
Evidence for the neuroprotective properties of propofol comes from trials such as the SIESTA and GOLIATH trials, which indicated improved neurological outcomes in patients undergoing endovascular clot retrieval for stroke when general anesthesia was maintained with propofol. However, these studies did not focus on the agent-specific effects of propofol but rather compared general anesthesia to sedation. In a separate trial where propofol was titrated to induce burst suppression during cardiac valve surgery, no improvement in neurological outcomes was found. This may be attributed to the fact that burst suppression, in itself, is associated with adverse neurological effects. As a result, while propofol has shown promise in some settings, more studies are needed to assess its specific neuroprotective effects.
