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The forms of anaesthesia
There are four types of anaesthesia:
| Sedation
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Local
Anaesthesia |
General
Anaesthesia |
Regional
Anaesthesia |
Your anaesthetist will determine the best type of anaesthesia for
you, according to your desires whenever possible. These options will be discussed during
your preoperative interview with the anaesthetist. The final decision about the best type
of anaesthetic depends on the specific operation, patient, anaesthetist, and surgeon
involved.
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This means that the patient is given a drugs which make the
patient drowsy and relaxed, but not completely asleep. Sedation can be used when
performing regional anaesthesia or during surgery under regional anaesthesia to help the
patient relax.
Local anaesthesia, strictly speaking, means putting local
anaesthetic around the affected area to make it pain free. This is where only a small area
is anaesthetized e.g. freezing the skin so that a cut can be stitched up. For small cuts
and the removal of small skin lesions, local anaesthetic is injected around the site. This
may require several injections, but it is usually simple, safe and effective.
However, many people use the phrase loosely to include regional anaesthesia.
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Anaesthesia means the absence of sensation. General
anaesthesia is most often used for major surgical procedures that require prolonged
unconsciousness. During general anaesthesia the entire body, including the brain, is
anaesthetized. The patient is deeply asleep, feels nothing during the operation, and
remembers nothing about the operation afterward. General anaesthesia may be given either
by injection or by mask, or both. During general anaesthesia, different machines must
monitor vital functions (blood oxygen concentration, heart rate, blood pressure).
If you are receiving general anaesthesia, you will be lying on the operating table while a
mask and/or intravenous flexible catheter is put in place. After the gaseous or
intravenous anaesthetic is administered, you will be absolutely unconscious. While
under anaesthesia, the surgery is performed and your vital signs are monitored. While
unconscious, your breathing will usually be controlled by a special machine using a
breathing tube in your wind pipe ("trachea").
After surgery, into the recovery room, your vital signs will continue to be monitored.
There may be an interval of confusion as you regain consciousness. Once you are completely
aware, you may begin to feel some pain in the area of surgery, irritation in the throat,
and nausea. These symptoms may persist for a few days and you may require drugs for pain
relief.
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What does the Anaesthetist use to put me
to sleep?
General anaesthesia includes three parts: sleep, absence of pain, and absence of
movement.
Anaesthetists choose from a variety of drugs to fulfill various functions such as stopping
pain, making the patient unconscious, and relaxing the muscles. To do this, they may
administer anaesthetic gases (inhalation drugs), sedatives, narcotic drugs (pain killers),
muscle relaxants and many other drugs that act to help maintain normal body functions.
The simplest anaesthetic consists of an IV injection like pentothal or propofol which can
produce all these effects for a short period of time.
If you are able to breathe during the anaesthetic, a short tube (an "airway")
may be placed in your mouth. But for other operations, muscle relaxants are required to
paralyse the patient during surgery. In this case, a piece of curved plastic, called
"endotracheal tube" will be placed in your trachea ("windpipe").
How do I wake up?
This depends on the type of anaesthetic. Short acting drugs simply wear off.
Anaesthetic gases are replaced by air or oxygen. Muscle relaxants, and sometimes the
powerful narcotic drugs (painkillers), may need special drugs to reverse their effects.
Once you are sufficiently awake, any tube in your mouth can be removed. You will stay in
the Recovery Room for a period until you are completely awake. You should remember not to
operate machinery or drive a car for 24 hours after your anaesthetic.
How does the Anaesthetist know if I'm OK
during anaesthesia?
The anaesthetist and operating room nurses will ensure that you are properly monitored
throughout the anaesthetic. These monitors will allow them to closely follow how your body
is doing while the surgeon is working. These monitors include heart rate, blood pressure,
oxygen saturation, temperature, and carbon dioxide monitors.
In addition to all these mechanical monitors, and the alarm systems built into the
anaesthetic machine, the anaesthetist remains with the patient from the time the patient
goes to sleep until he/she is safe and stable in the recovery room.
Could I wake-up during general
anaesthesia?
That is very rare except in special circumtances (cardiac surgery, caesarean section,
trauma) where the anaesthetist has to limit depth of anaesthesia. Patient movement is a
sign of insufficient anaesthesia and an indication to deepen the anaesthesia. Also an
increased heart rate and blood pressure are signs of inadequate anaesthesia. Caesarean
section under general anaesthesia has the highest incidence of awareness.
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Regional anaesthesia means blocking the nerve supply to area of the body so the
patient cannot feel pain in that region.
Many patients, and even some physicians, automatically presume that surgery requires
general anaesthesia, and that the patient should be asleep during surgery. Many procedures
can be performed on awake patients, using local or regional anaesthesia. This may avoids
the risks and unpleasantness sometimes associated with general anaesthesia and may provide
specific benefits such as reduced blood loss and better postoperative analgesia.
People are often anxious about having surgery under a local or regional
anaesthetic. These
fears are not usually justified by the facts. The more patients understand the benefits of
local or regional anaesthesia, the more likely they are to choose this technique.
Here is a list of the common operations or
procedures that can be done with regional anaesthesia:
- Surgery on the arm and hand
- Surgery on the leg and foot
- Hernia repair
- Caesarean section and childbirth
- Bone-setting after a fracture
- Ophthalmic surgery
- Haemorrhoid removal
- Urologic surgery
- Gynaecologic surgery
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How is it used?
Local or regional anaesthesia can often be used to prevent pain during
surgery.
Sometimes it is used by itself, with no other medications, so that the patient remains
wide awake during surgery. It can also be combined with sedative drugs to make the patient
relaxed or sleepy during surgery.
Sometimes local or regional anaesthesia is used in addition to a general anaesthetic
(i.e., in patients who are asleep during surgery). This is done to reduce the stress
associated with surgery, to allow a lighter level of anaesthetic during surgery, and to
provide pain relief after surgery.
Nerve blocks are also used in the diagnosis and treatment of some painful
conditions, and
to provide pain relief during labour.
What drugs are used?
The most common drugs are local anaesthetic agents, which block all types of nerve
conduction. They prevent pain and may also prevent movement in the area until the block
wears off.
A variety of local anaesthetic drugs is available: Bupivacaine, Lidocaine,
Mepivacaine, Tetracaine, and Ropivacaine, (a new longer-acting agent which appears to be safer than
Bupivacaine).
Other drugs may be added to the local anaesthetic, including epinephrine (adrenaline), to
decrease bleeding, and sodium bicarbonate, to decrease the acidity of the drug, in an
attempt to make it work faster.
For spinals and epidurals, narcotic drugs such as morphine and fentanyl can be
used,
usually in addition to a local anaesthetic.
Will it hurt?
Local and regional anaesthetic techniques involve using a syringe and needle to inject
drugs in the correct area. Unfortunately, this can often be unpleasant, and the local
anaesthetic may sting during injection. But this discomfort is a small price to pay for
pain relief during and after surgery.
During the operation, patients may still be able to feel touch and pressure or
occasionally tugging. But patients should not feel pain during the operation.
Will it work?
When the right amount of the right drug is injected in the right place, it will
eventually work and provide good pain relief. The problem areas are usually putting the
drug in the right place and waiting long enough for it to work. In some cases, the correct
spot is easy to identify (e.g. spinal anaesthesia) while, in other cases (e.g.
epidural,
sciatic nerve block), it is harder to find the correct spot. Most blocks take 5-20 minutes
to work.
Commonly used blocks are usually 95% likely to work, depending on the type of block and
the skill of the anaesthetist.
What if it does not work regional anaethesia?
Depending on the circumstances, there are a variety of alternatives
available:
- Add more local anaesthetic. Often, additional anaesthetic can be
given, either by
repeating the original block, doing a different block of the same area, or injecting local
anaesthetic into the incision, during surgery.
- Add some sedation. A small amount of analgesic medication often makes the patient more
relaxed and comfortable.
- Convert to a general anaesthetic.
- Postpone the procedure.
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What are the possible side effects?
The potential for side effects or complications exists with any form of
anaesthesia.
In general, local or regional anaesthesia is very safe, and usually safer than a general
anaesthetic.
The most common side effect is a temporary weakness or paralysis of the affected area.
This is wears off after a while.
The complications may usually occur when the local anaesthetic is injected in the wrong
place. If a large volume (10-20 mls.) of local anaesthetic is injected into a vein by
mistake, it may cause convulsions and even cardiac arrest. This is why anaesthetist always
inject drugs slowly, sucking back on the syringe to check the local anaesthetic is not
going into a vein. In fact major nerve blocks must be performed in an area equipped with
oxygen, suction, drugs, and other resuscitation devices.
Why choose a local or regional anaesthetic?
Surveys indicate that anaesthetists would often choose local anaesthesia if they
required surgery themselves, for the following reasons:
- local anaesthesia avoids some of the risks and
unpleasantness, such as nausea and vomiting, which sometimes occurs with general
anaesthesia;
- local anaesthesia often lasts longer than the
surgery, providing pain relief for several
hours after the operation;
- local anaesthesia may reduce blood loss;
- some patients feel more "in control" when they are awake during
surgery.
Why avoid a local or regional anaesthetic?
The type of surgery may not be suitable. Most operations in the abdomen and chest
(e.g. bowel, heart and lung surgery) require general anaesthesia.
Some anaesthetists do not have the skills required to perform the necessary
procedures.
Not every patient is suitable for local or regional anaesthesia. Some patients cannot cope
with the idea of being awake during surgery.
What are spinal and epidural anaesthesia?
Spinal anaesthesia involves putting local anaesthetic near the spinal cord to
anaesthetize the lower region of the body. It is usually safe than general
anaesthesia.
Spinal anaesthesia is suitable for many procedures in the lower half of the body :
- Caesarean section and obstetric analgesia
- hernia repair
- hip and knee surgery
- transurethral resection of prostate
- most procedures on the foot or leg.
Technically, there are two types of "spinal"
anaesthesia: true spinal, or
"intrathecal" anaesthesia, and epidural or extradural anaesthesia.
The first technique involves injecting local anaesthetic into the fluid (CSF) which
surrounds the spinal cord. Spinal anaesthesia quickly blocks pain, with a small amount of
local anaesthetic (2 or 3 mls). The major disadvantage of a spinal anaesthetic is a drop
in blood pressure. This can be treated easily, if necessary.
These days headaches after spinal anaesthesia are vey rare because of the use of very thin
specially-designed needles. If they occur, they can be treated with rest, adequate liquids
to drink, pain-killers such as NSAIDs, Paracetamol (Acetaminophen) or Tramadol.
Epidural or extradural anaesthesia uses a larger volume of anaesthetic, positioned in an
area further away from the spinal cord (epidural space). This block takes effect more
slowly and is less likely to produce a drop in blood pressure. The major advantage is that
a thin tube can be placed in the epidural space to allow the block to be continued over a
period of days.
An important disadvantage of epidural analgesia is that larger amounts of local
anaesthetic are used (about 20 mls.) which can cause complications if they are put in the
wrong place (in a vein or in the CSF). These complications can be treated by an
anaesthetist, usually without long-lasting problems.
Can I have epidural analgesia in labour?
The epidural analgesia is the most effective form of pain relief in labour, and it can
even be extended for use in forceps delivery or Caesarean section.
A thin, sterile plastic tube is placed in the patient's back by an anaesthetist. Local
anaesthesia is inserted through the tube, providing pain relief. Sometimes pumps can be
used to give continuous epidural drugs. Women who have epidurals in labour may be more
likely to have forceps deliveries or Caesarean sections. Epidural analgesia may avoid the
potential complications of an emergency general anaesthetic, and is especially useful for
women with high blood pressure, twins, or breech presentation.
Side effects may include temporary weakness in the legs, difficulty passing urine, and/or
a decrease in blood pressure.
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Can I be paralyzed after epidural anaesthesia?
Paralysis after epidural anaesthesia is extremely rare. For example, it is even rarer
that death after general anaesthesia. The mid-lumbar spine location for most epidural
techniques is chosen because of it reduces the likelihood of nerve damage. In this area of
the back the spinal cord has finished and has divided into a bunch of nerves which float
in an area filled with cerebrospinal fluid. A needle entering this area is unlikely to
damage these nerves. Other risks include injecting the wrong drug, and the formation of a
blood clot or abscess in the back. Careful attention to detail, and to patient
selection,
minimise these risks.
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