General anaesthesia is often homologated to physiological sleep whereas they only share some of the same characteristics. The differences are remarkable in electroencephalographic characteristics and in the way in which the state of disconnection from the environment is established. General anaesthesia and surgery are phenomena that alter the physiological cycles of postoperative sleep depending on the drugs used, the neurological depression achieved, the functional reserve of the patient and specific phenomena of neuroinflammation triggered by the surgery. Anaesthesia shares very partially the mechanisms that trigger sleep but shares a common phenomenon: the sleep inertia; They do share a common phenomenon: the inertia of awakening, possibly enhanced by anaesthesia in susceptible patients. Given the physiological importance of sleep in the postoperative reparative process, it is essential to recognize which patients are likely to influence their reconnection and to take preventive actions to minimize the impact on postoperative sleep architecture. This article describes the differences and similarities between anaesthetic and physiological sleep, including electroencephalographic differences, the effect of different anaesthetics on postoperative sleep architecture, the phenomenon of common inertia and neuroinflammation.