Most anesthetic techniques act by inducing a reversible disturbance of the central nervous system (CNS). Spinal or epidural application of local anesthetics produce a localized inhibition of impulse transmission at spinal cord level leading to central nervous blockade where the essential features are segmental loss of sensory and motor function. General anesthetics administered intravenously act through binding to specific receptors such as opioid or GABA (γ-aminobutyric acid) receptors; however, the mechanisms of action for inhaled anesthetics are less well described. Inhaled anesthetics bind to proteins and lipids in the neuronal membranes and anesthetic effect is probably mediated through several mechanisms—for instance, inhibition of synaptic transmission by specific and nonspecific binding, including interaction with GABA receptors.

Accordingly, depression of CNS function is intended as a part of anesthesia. We expect this condition to be perfectly reversible and transient but as it will be described, several complications may occur—some of these causing serious disability. The methods for detecting CNS dysfunction dictate the ability to recognize some of these conditions. The most common CNS dysfunction after anesthesia is cognitive dysfunction but this has been neglected after noncardiac surgery owing to its subtle nature and an inappropriate methodology applied in most studies within this field.

CNS dysfunction after anesthesia will be described in two ways: how different mechanisms may disturb CNS function after anesthesia and how this dysfunction presents clinically. In the last section of this article, the diagnostic approach and some preventive strategies will be discussed.