The origin of the word anaesthesia is the greek word for insensitivity - „anaisthaesia“.
It describes the total numbness of the body or parts of it.
This condition is reached with different drugs which inhibit the activity of neural tissue locally, in a specific region or in the whole CNS.
Depending on the mode of application there are injectible and volatile (inhalation) anaesthetics.
Analgesia: a pain-free condition
Sedation: the calming down of an animal through CNS depression. The patient is dizzy and doesn´t respond to its surroundings, but reacts on a painful stimulus.
Narcosis: is a drug induced status of deep sleep from which the patient cannot easily be woken. Depending on the used drug narcosis can be accompanied by analgesia or not.
Hypnosis: is a drug induced state of sleep or trance through CNS depression from which the patient can be woken relatively easily.
General anaesthesia: a condition of reversible unconsciousness and insensitivity due to drug induced CNS depression. Waking up is impossible, even with painful stimuli.
Sensoric, motoric and autonomous reflexes are reduced.
Surgical anaesthesia: is a stadium of general anaesthesia characterized by unconsciousness, muscle relaxation and analgesia deep enough to allow surgery without pain.
Balanced anaesthesia: is a surgical anaesthesia achieved with the combinational use of different drugs, each of which is responsible for a specific effect.
Neuroleptanalgesia: is a twilight sleep with analgesia achieved by the combination of a tranquilliser with an opioid. Neuroleptanalgesia is a commonly used premedication in many european countries. By itself it does not provide surgical tolerance.
Premedication - Induction - Maintenance
Every general anaesthesia should consist of these three parts.
Premedication is important to calm down the patient, reduce stress and provide preemptive analgesia.
The necessary amount of drugs used for induction and maintenance can be significantly reduced in premedicated patients.
Drugs used for induction are mainly injectibles.
CNS depression is deep enough to allow intubation.
Either total intravenous (TIVA) or gas anaesthesia can be used for maintenance. The combinationof both is called partial intravenous anaesthesia (PIVA) and has become increasingly popular in the last years.