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Choices of Anaesthesia


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General anaesthesia
Being put to sleep

This is the most common form of anaesthetic people will encounter. The name implies a state where your whole body is included in the unfeeling, uncaring state which is induced. While most people think of it as sleep, it is much more than sleep. When you are asleep your body is still just as active as when you are awake. All your body reflexes are still at similar levels to when you are awake - for example if someone was to cut you with a knife you'd wake up in pain and do something to protect yourself from it. General anaesthesia on the other hand is a state of induced coma. It changes the way the body responds to different senses. You usually do not dream except just as you're being anaesthetised and when you are rousing from your anaesthetic. Your bodies reflexes are very changed with only primitive body functions still working. No actual rest like sleep is actually achieved during a general anaesthetic so if you are sleepy prior to being anaesthetised you are still sleepy afterwards no matter how long you have been anaesthetised for. Despite this, I will still refer to it as "sleep" from here on for simplicity.

Most forms of general anaesthesia involve some combination of intravenous drugs and anaesthetic gases. Although you will be rendered asleep for this sort of anaesthetic this does not mean you wont get some form of regional anaesthetic also. Most commonly the drug that will put you off to sleep will be but into your intravenous drip and then you will be kept asleep by anaesthetic gas during the operation. Once you have been anaesthetised a breathing tube is normally placed into your mouth which keeps you connected to the anaesthetic machine. This anaesthetic machine gives you all the oxygen and anaesthetic gas you need and may help your breathing as well. Further drugs are given by either the drip and the gases as are required during the operation (simple examples are pain killers and antibiotics). Whether you have full muscle strength for yourself or if this is weakened during the operation is determined by the requirements of the operation and the anaesthetic - more often you have full muscle strength. Waking up is the process of weaning you off the gases and drugs, and giving you drugs to increase your muscle strength. When you have reached a certain level of consciousness the breathing tube will be removed and you will have an oxygen mask placed on your face and you will be moved to the recovery room.

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Regional anaesthesia
Being made numb

Regional anaesthesia, as the name implies, is where only a region or part of your body is given the unfeeling, uncaring state. As well as this state, you can be given differing degrees of sedation to make you comfortable or even asleep if appropriate. This can be accomplished in numerous ways.

Local Anaesthetic
The simplest form of regional anaesthesia most people understand is having an operation under local anaesthetic. This is - like at the dentist - where local anaesthetic drug is injected around the area where the operation is to occur and the area to be operated on becomes numb. Then the operation can proceed without you feeling any pain. Occasionally the sensation that someone is touching you is still there but it is not painful. The local anaesthetic has a duration which long outlasts the operation but the feeling usually returns within 1-4 hours depending on the drug used. Other painkillers can then be taken to prevent pain being felt in the area.previously operated on.

Nerve Block
A more involved form of regional anaesthesia is the nerve block. As the name implies the nerves that give the feeling to the area being operated on are `blocked' by local anaesthetic, preventing pain being felt. A common example of this is the arm block. If you need an operation on your hand for example, an arm block can be used for this. An arm block involves injecting local anaesthetic at a discrete spot (usually in the armpit). An arm block usually lasts between 2 and 16 hours depending on the drug used. There are numerous other nerve blocks than can and are performed around the body to make different areas numb. While these can be used alone for the operation you may be put to sleep as well. They have the benefit of decreasing the amount of other drugs given to you for the general anaesthetic thereby limiting the side effects you may get from the general anaesthetic, and providing you with excellent pain relief after the operation while it remains numb. Occasionally a small drip can be inserted near the nerve to continually give local anaesthetic after the operation to give better pain relief.

Spinal Anaesthetic
A spinal anaesthetic is a very specialised way of applying local anaesthetic to make the lower half of the body numb. It is performed by placing a very fine needle into your lower back - the `lumbar region' between the bones of the spine, and injecting local anaesthetic drug into the fluid that surrounds your spinal cord (which gives all your body it's feeling). The needle is not injected into the nerves or the bones, and is usually only as painful as having blood taken. Local anaesthetic then blocks the nerves in your spine and makes you go numb from about the waist down. Along with this your legs feel very weak and often you will be unable to move them during the operation. A spinal usually lasts between 2 and 6 hours depending on the drugs used.

Epidural Anaesthetic
An epidural anaesthetic is similar to the spinal in many ways. A needle is placed between the bones of your spine but it can be anywhere from the top to the bottom of the spine. The needle is not injected into the nerves or the bones, and is usually only as painful as having blood taken. Then a very small drip is often placed in the epidural space and taped to your back. Local anaesthetic can then be injected into this drip as often and as much as is required. This local anaesthetic then numbs the nerves as they come out of the spine. Because it can be put in a discrete position in your back, parts of your body can be made numb selectively. A common example of this is the pain of labor and childbirth where the pain is initially in the abdomen or back. A carefully placed epidural will allow this area to be made pain free in a band from about the mid chest to the mid thighs. By so doing it will allow your legs to still have most of the strength. Also we can vary the strength of the epidural to make it just numb enough to not feel labour pains or strong enough to allow surgery to be performed. A major advantage of the epidural anaesthetic is that further local anaesthetic can be injected into the epidural drip for days after the operation maintaining excellent pain relief no matter how painful the operation might have been.

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Sedation
Being made relaxed

There are some surgical procedures which are not painful but are unpleasant and mildly uncomfortable. For these procedures it is unnecessary to perform a general anaesthetic and so various degrees of sedation can be given to make them less unpleasant. Furthermore, the drugs used for this sedation often make you forget most of the procedure. Sedation can be used by itself for procedures such as a gastroscopy where you swallow a special telescope that looks into your stomach, or sedation can be used to supplement a regional anaesthetic, to make the overrall experience not unpleasant.

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Pros and Cons
What are the advantages and disadvantages of each anaesthetic technique?

A whole textbook of anaesthesia can be dedicated to this question alone so I will summarise only the key issues of concern. Because the safety of anaesthesia is so high it is difficult to prove that one technique is safer than another. In terms of overall safety there are a small number of operations and medical illnesses which are safer under regional anaesthesia. However for the majority of operations the differences are more subtle, with safety apparently being similar. There is no doubt that some people prefer to be asleep and some people prefer to be awake. If someone was to have a caesarean section to deliver their baby for example, most people would want to be awake to see the baby born - it is therefore lucky that this is one of the operations that is safer under regional anaesthesia.

Under general anaesthesia you are more likely to wake up at the end with some pain, nausea and drowsiness, but it has the obvious advantage of one injection and the next thing you know you're awake and it's over. With regional anaesthesia more procedures are performed on you prior to the operation (further injections for example), and the part of your body that is made numb remains numb for some time after the operation - this is an advantage as well as a disadvantage. One of the disadvantages of regional anaesthesia is that occasionally it does not make the area fully numb - don't worry no one will operate on you without testing the area first. This can usually be fixed with further local anaesthetic into the area or, if necessary, by putting you off to sleep. There is also a small risk of doing damage to the nerves that the regional block is working on. An arm block for example has a small rate of leaving a numb patch or weak spot in your hand that most often gets better within months but rarely can be permanent. Most people's fear of epidurals is that of being paralysed. This is an extremely rare occurrence and happens as rarely as dying under anaesthetic. In terms of advantages, regional anaesthesia minimises the amount your breathing and heart function is affected and this may have major benefits. It also decreases the amount of `stress' your body has in response to the operation and this too may be beneficial. Finally with regional anaesthesia you usually have better pain relief, and less nausea and drowsiness after the operation.

A common practice is to combine regional and general anaesthesia to capitalise on the advantages of both and decrease the disadvantages of using one alone. Ultimately your anaesthetist will have a plan for what they believe you are best served by and if there are options they will discuss them with you.


Gallery
 
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Going off to sleep (Click for larger image)
 

  Back to Top Site created by Con Kolivas Jan 2001
 

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