Incredibly rare, affecting an estimated 1 in every 19,000
patients undergoing general anesthetic. Because of the muscle relaxants given
alongside anesthesia, patients are unable to signal to their surgeon or
anesthetist that they are still aware of what is happening.
Local anesthesia
is another option. It is given before minor surgeries, such as removal of a
toenail. This reduces pain sensations in a small, focused areas of the body,
but the person receiving the treatment remains conscious. Regional anesthesia
is another type. This numbs an entire portion of the body - the lower half, for
example, during childbirth. There are two main forms of regional anesthesia:
Spinal anesthetic and epidural anesthetic. Spinal
anesthetic is used for surgeries of the lower limbs and abdomen. This is
injected into the lower back and numbs the lower body. Epidural anesthesia is
often used to reduce the pain of childbirth and lower limb surgery. This is
administered to the area around the spinal cord through a small catheter
instead of a needle injection.
Pre-surgical evaluation:
Before general anesthesia is administered, patients will
have a pre-surgery assessment to determine the most appropriate drugs to use,
the quantities of those drugs and in which combination.
Stages:
Modern anesthetics and updated delivery methods have
improved the speed of onset, general safety, and recovery, but the four stages
remain essentially the same:
· The period following a loss of consciousness,
characterized by excited and delirious activity. Breathing and heart rate
becomes erratic, and nausea, pupil dilation, and breath-holding might occur.
·
Because of irregular breathing and a risk of
vomiting, there is a danger of choking. Modern, fast-acting drugs aim to limit
the time spent in stage 2 of anesthesia
·
surgical anesthesia: vomiting stops, Muscles
relax and breathing is depressed. Eye movements slow and then cease. The
patient is ready to be operated on
·
Too much medication has been administered,
leading to brain stem or medullary suppression. This results in respiratory and
cardiovascular collapse.
·
The anesthetist's priority is to take the
patient to stage 3 of anesthesia as quickly as possible and keep them there for
the duration of the surgery.
How does general anesthetic work?
The exact mechanisms that conspire to produce the state of
general anesthesia are not well known. The general theory is that their action
is induced by altering the activity of membrane proteins in the neuronal
membrane, possibly by making certain proteins expand.
Of all the drugs used in medicine, general anesthetics are
an unusual case. Rather than a single molecule acting at a single site to
produce a response, there is a huge variety of compounds, all of which
generating quite similar but widespread effects, including analgesia, amnesia,
and immobility.
