This is a commonly used drug in anesthesia and critical care, mainly as an induction agent and in total intravenous anesthetic technique in neuroanesthesia. It is also used as a sedative agent in critically ill patients especially in neurocritical care unit to provide cerebral protection. Propofol decreases the cerebral metabolic rate for oxygen (CMRO₂), which leads to a reduction in CBF and ICP. However, one must be cautious when large doses are being used as it may result in systemic hypotension that will further compromise the CPP. Propofol is known to cause myoclonus but is non-epileptogenic, and is sometimes used to treat refractory status epilepticus.

Thiopental is less commonly used nowadays due to its unfavorable pharmacokinetic profile. It decreases CMRO₂ and causes cerebral vasoconstriction which result in reduced CBF, cerebral blood volume (CBV) and ICP. Thiopental can cause significant hypotension, which can impair CPP. It is sometimes used in selected cases with refractory elevated ICP to produce a state of deep coma when other conventional therapies failed to reduce ICP. Induced coma with the use of barbiturates like thiopental is called barbiturate coma.

Agents in this category such as midazolam are widely used as sedative agents in neurocritical care unit. Its effect on cerebral physiology is similar to the above drugs, but to a lesser degree, with a less significant drop in CMRO₂, CBF, CBV and ICP.

Cerebral blood flow (CBF) is affected mainly by oxygen and carbon dioxide tensions in the blood and by autoregulation. CBF under normal conditions is maintained at a relatively constant rate despite variations in CPP. The mechanism involves alteration in the cerebral vascular resistance by changing the diameter of the cerebral arterioles. This phenomenon is known as autoregulation (Fig. 13.2). CBF is held constant over the CPP range of 50–150 mmHg. At the upper limit, the arterioles are maximally vasoconstricted and any increase in CPP will result in increased CBF. At the lower limit, the arterioles are maximally dilated in an attempt to maintain CBF, below which CBF becomes pressure dependent.

Cerebral perfusion pressure (CPP) depends on the mean arterial pressure (MAP) and the ICP or jugular venous pressure (JVP), whichever is greater, whereby
Many conditions can affect this autoregulatory process, which includes traumatic brain injury, hemorrhage, infection, tumor and certain pharmacological agents. Cerebral blood flow can be controlled by manipulating the mean arterial pressure and by changing the caliber of the cerebral blood vessels.