General anesthetics act on the central nervous system (CNS) to induce a reversible loss of consciousness, analgesia, amnesia, and muscle relaxation. They do this by modulating neurotransmitter activity, primarily by:

1. Enhancing Inhibitory Neurotransmission

 • Most general anesthetics enhance the effect of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid) at the GABA-A receptor.

• GABA-A is a ligand-gated chloride channel. When activated:

 • Chloride ions (Cl⁻) enter the neuron.

 • This causes hyperpolarization (the inside becomes more negative).

 • Neurons become less likely to fire, reducing brain activity.

Examples:• Propofol  • Etomidate • Barbiturates • Inhaled anesthetics (e.g., isoflurane, sevoflurane)

2. Inhibiting Excitatory Neurotransmission

Some anesthetics inhibit excitatory pathways, especially those mediated by glutamate.

 • NMDA receptors are a type of glutamate receptor. When blocked:

 • Neuronal excitation is reduced.

 • Leads to analgesia and dissociative anesthesia.

Examples: • Ketamine (blocks NMDA receptors)  • Nitrous oxide • Xenon 

3. Modulation of Other Ion Channels

 • Two-pore domain potassium channels (K2P): Their activation causes K⁺ efflux, hyperpolarizing neurons.

 • Voltage-gated sodium channels: Some anesthetics reduce neuronal excitability by affecting sodium influx needed for action potentials.

A general anaesthetic is used for many different types of operation (surgery) or procedure.

It's done so that during the procedure:

• you're asleep (unconscious)

• you do not feel any pain

• you're not aware of what's happening

• you're not moving and your muscles are relaxed, so doctors can treat you safely

A general anaesthetic is used if other types of anaesthetic are not suitable. These include a local anaesthetic or regional anaesthetic (where you're awake but the part of your body being treated is numbed) or sedation (where you're relaxed but not unconscious).

If you're going to have a general anaesthetic, you'll be given advice about things you can do to prepare.

If your procedure is planned in advance, you can help your recovery and help make your treatment more successful by:

• making sure any long-term conditions are managed as well as possible, such as diabetes, high blood pressure or anaemia

• keeping as physically active as possible, including doing exercise that raises your heart rate if you can

• stopping smoking

• getting treatment for any problems with your teeth, to reduce the risk of them being damaged by the breathing tube that's used during the general anaesthetic

A general anaesthetic is given in hospital. The anaesthetic team, led by a specialist doctor (consultant anaesthetist), will monitor you and adjust the anaesthetic when they need to.

You may be given other medicines before the general anaesthetic. This may include medicines to help you relax, reduce stomach acid, stop you feeling sick or help with pain.

The type of general anaesthetic that's used depends on the procedure you're having and what's best for you. It can be given as:

• an injection through a small tube (cannula) into a vein in your arm

• a gas that you breathe in through a mask – this is usually only used if it's difficult to find a vein in your arm

The general anaesthetic starts to work quickly. You'll fall asleep (become unconscious) within about a minute and will not be aware of anything until you wake up after the procedure.

During the procedure an anaesthetist will stay with you all the time. They will:

• monitor your heart rate, blood pressure and oxygen levels

• put a tube into your throat while you're asleep to help you breathe

• give you fluids through a drip into a vein

How long you're asleep (unconscious) depends on the type of procedure you're having. It can be from a few minutes to several hours.

You'll wake up either in the operating theatre after the procedure is over, or in the recovery room.

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After a general anaesthetic you'll start to wake up soon after the medicine is stopped at the end of the procedure.

You'll feel drowsy at first. You may have an oxygen mask to help you breathe. This will be removed when you're fully awake. Staff will look after you and give you medicines for any pain or sickness (nausea).

You can usually start eating and drinking again when you feel ready.

The effects of a general anaesthetic can last around 24 hours. How long it takes to fully recover depends on the type of procedure you had.

You may be able to go home within a few hours. Someone will need to collect you from the hospital and take you home by car or taxi.