UNIT 3
Anaesthesia
Starting point
1 Before reading about anaesthesia, think about the subject in general:
What is anaesthesia?
When and for what purpose is it used?
In what medicine branches is anaesthesia used?
What types of anaesthesia do you know?
2 Now read the text quickly. Note all the words or phrases which you don’t know or are not sure of clearly.
Anesthesia, or anaesthesia (see spelling differences; from Greek αν-, an-, "without"; and αἲσθησις, aisthēsis, "sensation"), has traditionally meant the condition of having sensation (including the feeling of pain) blocked or temporarily taken away. This allows patients to undergo surgery and other procedures without the distress and pain they would otherwise experience. The word was coined by Oliver Wendell Holmes, Sr. in 1846. Another definition is a "reversible lack of awareness", whether this is a total lack of awareness (e.g. a general anaesthetic) or a lack of awareness of a part of the body such as a spinal anaesthetic or another nerve block would cause. Anesthesia is a pharmacologically induced reversible state of amnesia, analgesia, loss of consciousness, loss of skeletal muscle reflexes and decreased stress response. Today, the term general anesthesia in its most general form can include:
Analgesia: blocking the conscious sensation of pain;
Hypnosis: producing unconsciousness;
Amnesia: preventing memory formation;
Paralysis: preventing unwanted movement or muscle tone;
Obtundation of reflexes, preventing exaggerated autonomic reflexes.
There are several forms of anesthesia. The following forms refer to states achieved by anesthetics working on the brain:
General anesthesia: "Drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation." Patients undergoing general anesthesia can often neither maintain their own airway nor breathe on their own. While usually administered with inhalational agents, general anesthesia can be achieved with intravenous agents, such as propofol.
Deep sedation/analgesia: "Drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulation." Patients may sometimes be unable to maintain their airway and breathe on their own.
Moderate sedation/analgesia or conscious sedation: "Drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation." In this state, patients can breathe on their own and need no help maintaining an airway.
Minimal sedation or anxiolysis: "Drug-induced state during which patients respond normally to verbal commands." Though concentration, memory, and coordination may be impaired, patients need no help breathing or maintaining an airway.
The level of anesthesia achieved ranges on a continuum of depth of consciousness from minimal sedation to general anesthesia. The depth of consciousness of a patient may change from one minute to the next.
The following refer to the states achieved by anesthetics working outside of the brain:
Regional anesthesia: Loss of pain sensation, with varying degrees of muscle relaxation, in certain regions of the body. Administered with local anesthesia to peripheral nerve bundles, such as the brachial plexus in the neck. While traditionally administered as a single injection, newer techniques involve placement of indwelling catheters for continuous or intermittent administration of local anesthetics.
Spinal anesthesia: Refers to a Regional block resulting from a small volume of local anesthetics being injected into the spinal canal. The sub arachnoid block results in a loss of pain sensation and muscle strength, usually up to the level of the chest (nipple line or 4th thoracic dermatome).
Epidural anesthesia: Regional block resulting from an injection of a large volume of local anesthetic into the epidural space. This is basically an injection around the spinal canal.
Local anesthesia is similar to regional anesthesia, but exerts its effect on a smaller area of the body.
3 Now answer the questions before the text using the information given in it. Try to give detailed answers.
4 Match the phrase on the left to the definition on the right. Check that your ideas make sense in the context of the text.
1. General anesthesia |
a. Drug-induced state during which patients respond normally to verbal commands. |
2. Deep sedation/analgesia |
b. Regional block resulting from an injection of a large volume of local anesthetic into the epidural space. |
3. Moderate sedation/analgesia or conscious sedation |
c. Drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation |
4. Minimal sedation or anxiolysis |
d. Refers to a Regional block resulting from a small volume of local anesthetics being injected into the spinal canal. |
5. Regional anesthesia |
e. It is similar to regional anesthesia, but exerts its effect on a smaller area of the body |
6. Spinal anesthesia |
f. Drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulation |
7. Epidural anesthesia |
g. Loss of pain sensation, with varying degrees of muscle relaxation, in certain regions of the body |
8. Local anesthesia |
h. Drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation |
5 Mark the following statements as true (t) or false (f). Prove your point of view.
1. Anaesthesia allows patients to undergo surgery and other procedures with the distress and pain they would otherwise experience. |
T/F |
2. Anesthesia is a pharmacologically induced reversible state of amnesia, analgesia, loss of consciousness, loss of skeletal muscle reflexes and decreased stress response. |
T/F |
3. Today, the term general anesthesia in its most general form can include only blocking the conscious sensation of pain and producing unconsciousness |
T/F |
4. Patients undergoing general anesthesia can often neither maintain their own airway nor breathe on their own. |
T/F |
5. Patients undergoing moderate anesthesia cannot breathe on their own and need help maintaining an airway. |
T/F |
6. Spinal anesthesia is similar to regional anesthesia, but exerts its effect on a smaller area of the body. |
T/F |
7. Paralysis means producing unconsciousness. |
T/F |
8. Obtundation of reflexes prevents exaggerated autonomic reflexes |
T/F |
6 Skim the text about anaesthesia. Find an appropriate heading for each section (1-8).
A Is anaesthetic safe?
B What is it like after the operation?
C What is an anaesthetic?
D How do people feel when they wake up?
E What does the anaesthetist do?
F How and where does the patient wake up?
G Who is the anaesthetist?
H Where and how does the patient go to sleep?
Written by Dr Gordon FN Smith, consultant anaesthetist
(1) An anaesthetic is used to temporarily reduce or take away sensation, usually so that otherwise painful procedures or surgery can be performed. Throughout the procedure, different types of medicines are added or removed to relieve the pain and maintain the right level of unconsciousness.
(2) A consultant anaesthetist is a specialist doctor who, after qualifying in medicine, spends about six years training in the specialty of anaesthesia. Anaesthetists see patients while being trained, but a consultant supervises them during all procedures.
(3) The anaesthetist takes a careful look at the history of the patient's general health and uses this information to decide how best to offer care. During the operation, the anaesthetist stays with the patient at all times to make sure they are comfortable and safe. This includes controlling pain, replacing body fluids and measuring and controlling all the vital functions of the body such as the heart beat, blood pressure and brain and kidney function.
(4) Anaesthetics are almost entirely safe, but every operation carries a very slight risk. A recent survey in the UK showed that death due to anaesthesia occurred in about five in every million anaesthetics given.
(5) Patients are given a small injection in the hand to make them go to sleep. This usually takes place in a room next to the operating theatre. Some patients - especially children - have an anaesthetic cream rubbed onto the skin beforehand so that they won't even feel the injection. Others are given a mixture of gases to put them to sleep very quickly.
(6) After the operation, the anaesthetist stops giving the medicines that were keeping the patient unconscious and he or she is taken to a recovery room where there are specially trained staff. The longer the operation, the longer it takes to wake up. When the patient has woken up completely, they are taken back to the ward. Occasionally, people recover consciousness in the operating theatre once their operation is over. This is quite safe.
(7) Patients often feel cold and slightly confused. They may have pain or feel a bit sick, but these symptoms can be treated when the anaesthetist visits the patients to check that they are alright.
(8) How people feel after the operation depends on the kind of surgery they have had. They will be encouraged to get out of bed as soon as possible and will usually be allowed to eat and drink in the first few hours after a minor operation.
http://www.netdoctor.co.uk/health_advice/facts/anaesthetic.htm