Hello and welcome to our lesson on the basics of anaesthesia.  ​ Prior to the surgeon beginning the procedure, the anaesthetist will anaesthetise or induce the patient, which will remove the sensation of pain during the procedure, and depending on the operation, render the patient unconscious. There are a few different types of anaesthetic that may be used, and these can be divided simply into general anaesthetic, regional anaesthetic, and local anaesthetic. Following administration of a general anaesthetic, the patient will be unconscious and will have no awareness or sensations. General anaesthetic may be administered via a vapour or gas through a mask, or intravenously. Most major operations involving the heart, lungs, or abdomen will require general anaesthesia, as well as many involving arteries or the brain. The drugs work by preventing the brain from responding to sensory impulses from the peripheral nerves of the body. Unlike normal sleep, a patient cannot be woken from general anaesthesia until the drugs are stopped and wear off. Regional anaesthesia involves a local anaesthetic being injected near to nerves supplying a larger area of the body resulting in a numbing effect. · Spinal and epidural anaesthesia are the most common forms of regional anaesthetic. A benefit of these forms of anaesthesia is that the patient remains conscious whilst staying free of pain. Both techniques work by causing everything below the injection site in the spinal cord to become numb. These are typically used for operations involving the lower body, for example: caesarean sections, bladder operations and hip replacements. For a spinal anaesthetic, drugs are injected directly into the CSF located within the subarachnoid space of the spinal canal. This utilises a small drug dose and a finer needle than an epidural, with pain relief also being much shorter lasting (1-2 hours) which allows us to not insert a catheter. In an epidural, drugs are injected into the epidural space, and a catheter is typically inserted allowing for a continuous infusion to be set up for longer term pain relief. As the medication has to cross the dura mater to reach the target nerves in the spinal cord, it takes around 10-15 minutes for pain relief to begin. Studies have shown that epidural anaesthesia has a decreased side effect profile and results in shorter lengths of in-hospital stay. · Nerve blocks target a localised area of tissue, with pain sensation remaining intact elsewhere in the body. It causes the target area of the body to become numb, preventing the sensation of pain. This form of anaesthesia works by injecting the local anaesthetic near a specific nerve or a cluster of nerves providing sensation to the specific target area. This form of anaesthetic also provides further pain relief for several hours after the operation. This can take the form of a small injection into a tissue such as a toe for minor operations, but may also require injection into a large nerve cluster such as the brachial plexus to numb an entire arm. ​ Local anaesthetic is the simplest of the anaesthesia types. Local anaesthesia is injected around the operative site only. This may be done as the only form of anaesthesia, such as in minor procedures in dermatology, or it may be done as part of a larger procedure to reduce pain when the patient wakes up, such as in a knee replacement. Lastly, regarding anaesthesia, it is important to note that it is very poor practice to enter and leave the anaesthetic room whilst the patient is being induced and intubated. This is mostly because of the very sensitive nature of the procedure and it is often when a patient feels most vulnerable.