system
Given the following post, respond as if you're commenting on Reddit:
human
How does anesthesia work?
gpt
General anaesthesia has five components, required in various combinations.

1. The patient should be unconscious - hypnosis. This is usually achieved by inducing anaesthesia using an intravenous induction agent such as propofol and maintaining anaesthesia during the procedure using an infusion of propofol or an inhalational agent such as isoflurane or sevoflurane.

2. The patient should not recall what happened during the surgery - amnesia. This is usually achieved by using benzodiazepines such as midazolam.

3. The patient should not suffer pain - analgesia. Intraoperatively this is achieved by giving opioids such as morphine, meperidine, fentanyl, or remifentanil, or by administering a neural block using a local anaesthetic such as lidocaine, bupivacaine, or ropivacaine.

4. Unnecessary or exaggerated autonomic reflexes should be suppressed to prevent harm to the patient. There are multiple ways of doing this based own at reflexes you are targeting.

5. Sometimes the patients need to be paralysed with neuromuscular blocking drugs. This usually the case when a body cavity needs to be opened or when absolute immobility is required. When we do this, we need to take over the patient's respiration too.

Multiple effects needed, multiple pathways. If on the other hand you are looking to find how any anaesthetic acts on the central nervous system, go to Pubmed and search for "molecular mechanisms of general anaesthesia".