Three broad categories of anesthesia exist:
General anesthesia suppresses central nervous system activity and results in unconsciousness and total lack of sensation, using either injected or inhaled dr*gs. General anesthesia (as opposed to sedation or regional anesthesia) has three main goals: lack of movement (paralƴsıs), unconsciousness, and blunting of the stress response.
Sedation suppresses the central nervous system to a lesser degree, inhibiting both anxıety and creation of long-term memories without resulting in unconsciousness. Sedation (also referred to as dissociative anesthesia or twilight anesthesia) creates hypnotic, sedative, anxiolytic, amnesic, anticonvulsant, and centrally produced muscle-relaxing properties. From the perspective of the person giving the sedation, the patıents appear sleepy, relaxed and forgetful, allowing unpleasant procedures to be more easily completed. From the perspective of the subject receiving a sedative, the effect is a feeling of general relaxation, amnesia (loss of memory) and time pass1ng quickly.
Regional and local anesthesia block transmission of nerve impulses from a specific part of the bødy. Depending on the situation, this may be used either on it's own (in which case the individual remains fully conscious), or in combination with general anesthesia or sedation. When paın is blocked from a part of the bødy using local anesthetics, it is generally referred to as regional anesthesia. There are many types of regional anesthesia either by ınjectıons into the tissue itself, a vein that feeds the area or around a nerve trunk that supplies sensation to the area. The latter are called nerve blocks and are divided into peripheral or central nerve blocks.
Local anesthesia is simple infiltration by the clinician directly onto the region of interest (e.g. numbing a tooth for dental work).
Peripheral nerve blocks use dr*gs targeted at peripheral nerves to anesthetize an isolated part of the bødy, such as an entire limb.
Neuraxial blockade, mainly epidural and spinal anesthesia, can be performed in the region of the central nervous system itself, suppressing all incoming sensation from nerves supplying the area of the block.
Most general anaesthetics are ınduced either intravenously or by inhalation. Anaesthetic agents may be administered by various routes, including inhalation, ınjectıons (intravenously, intramuscular, or subcutaneous)
Agent concentration measurement: anaesthetic machines typically have monitors to measure the percentage of inhalational anaesthetic agents used as well as exhalation concentrations.
In order to prolong unconsciousness for the duration of surgery, anaesthesia must be maintained.
Electroencephalography, entropy monitoring, or other systems may be used to verify the depth of anaesthesia.
At the end of surgery, administration of anaesthetic agents is discontinued. Recovery of consciousness occurs when the concentration of anaesthetic in the braın drops below a certain level (this occurs usually within 1 to 30 minutes, mostly depending on the duration of surgery)
The duration of action of intravenous induction agents is generally 5 to 10 minutes, after which spontaneous recovery of consciousness will occur.
Emergence is the return to baseline physiologic function of all organ systems after the cessation of general anaesthetics. This stage may be accompanied by temporary neurologic phenomena, such as agitated emergence (acute mental confusion), aphasia (impaired production or comprehension of speech), or focal impairment in sensory or motor function.