Download Anaesthesia

The word "Anaesthesia" comes from a Greek word meaning absence or
loss of sensation.
Anaesthesia is one of the most significant developments of modern
medicine because it allows once-unbearable medical procedures to be
performed while the patient is relaxed and asleep.
Putting someone to sleep and keeping them asleep for
surgery or other medical procedures
Numbing an area of the body
Numbing a small part of the body
Medical doctors who
Specialise in the field of anaesthesia.
 Have expertise in intensive care medicine and other pain
relief techniques,
Are responsible for pain control and anaesthesia for
women in labour
Anaesthesia usually begins when the anaesthetist injects a drug
through a fine plastic tube (cannula) inserted into a vein in the back
of the hand.
Within a few seconds, this sends you quickly and smoothly to sleep.
This is known as the "induction" of anaesthesia
It is also possible to induce anaesthesia with anaesthetic gases,
breathed through a mask
A general anaesthetic drug is an anaesthetic drug that
brings about a reversible loss of consciousness
These drugs are generally administered by an anaesthetist
in order to induce or maintain general
anaesthesia to facilitate surgery.
(Gases or Vapors)
(Injections)
Most commonly these two forms are combined, although it is possible to
deliver anaesthesia solely by inhalation or injection
 Lasts until consciousness is lost
 Analgesia persists post operatively as Ether is Lipid soluble
and is released slowly from tissue stores.
 Begins with the loss of consciousness and ends with the
beginning of rhythmic respiration.
 Most difficult to manage as patient may move,vocalise,salivate
and vomit.
 Increased muscle tone,hypertension and tachycardia may also
occur
 Begins with reappearance of regular respiration.
 Loss of automatic eyelid closure, and loss of reflex closure of
eyelids on conjunctival stimulation
 Begins with the cessation of eye movements.
 Ends with the beginning of paralysis of the respiratory muscles
except the diaphragm
 Begins with increased abdominal excursions.
 Ends with paralysis of all respiratory muscles ,except the
diaphragm.
 Begins with the cessation of inter costal muscles.
 Ends with Diaphragmatic paralysis.
Begins with complete respiratory paralysis.
Ends with failure of circulation.
Medullary centers are completely paralyzed.
Heart and circulation fails.
EEG waves becomes smaller and eventually
disappears.
Ion channels are the ultimate site of action of general anaesthetics
General anaesthetics act on the central nervous system by modifying
the electrical activity of neurons at a molecular level by modifying the
function of ion channels
 This may occur by anaesthetic molecules binding directly to ion
channels or by their disrupting the function of molecules that maintain
ion channels
 Produce a progressive depression of CNS
 They depress the ARAS(ascending reticular activating system ) which is
concerned with Alertness and Wakefulness.
 The CONFORMATIONAL DISTORTIONAL THEORY postulates that the
Anaesthetic molecule distorts the membrane and impedes ionic flow
through the channels.
 The MEYER- OVERTON THEORY postulates that the more lipid soluble
a drug is , the greater is its potency.
 The HYDRATE OR WATER CRYSTAL THEORY states that the molecule
reacts with water in the brain tissue to form hydrates or micro crystals
of ice inhibiting nerve cell function.
 A number of bio-chemical theories have been advanced like Inhibition
of Glucose metabolism in brain cells.
Evaluation to determine which drugs (including dosages), additional
invasive monitors and/or analgesic therapies required by the patient
 Patient's age, weight, medical history, current medications, previous
anesthetics, and other factors relevant to administering
anesthesia noted
Facilitates the induction and maintenance
of anaesthesia
Minimizes the adverse effects of
anaesthesia
Defined as administration of drugs before
the anaesthetic is given
AIMS
 Relief of anxiety
 Relief in salivary and mucous secretion
 Inhibition of undesirable side-effects. (Bradycardia, Muscle
spasms)
Depend on type and length of surgery.
Condition of the patient.
Neuro-muscular blocking agents.
Muscle relaxants.
 Anti-Emetics. (To relieve Nausea and vomiting)
 Cholinergics (To relieve Abdominal distention
and Urinary retention)
 Analgesics (To relieve pain)
 Laxatives (To relieve Constipation)
Continuous Electrocardiography (ECG)
 Continuous Pulse Oximetry
 Blood Pressure Monitoring
Agent concentration measurement
Low oxygen alarm
Circuit disconnect alarm
Carbon dioxide measurement (capnography)
This is often to allow the surgeon to perform the operation by relaxing
the body’s natural muscle tone, which is present even when asleep.
When a muscle relaxant is used, the muscles responsible for breathing
are effectively paralysed and the anaesthetist has to control the
patient’s breathing.
To do this, a plastic tube is inserted into the windpipe (trachea)
and a machine called a ventilator inflates and deflates the lungs in an
accurate and controlled rhythm.
Muscle relaxation with skeletal muscle relaxants is an integral part of
modern anaesthesia.
Muscle relaxation, also known as neuro -muscular blockade,
allows surgery within major body cavities, eg. abdomen and thorax
without the need for very deep planes of anesthesia, and is also used to
facilitate endotracheal intubation
The muscles of the larynx are also paralysed so that the airway usually
needs to be protected by means of an endo -tracheal tube
Muscle relaxants work by antagonising the natural neurotransmitter
substance acetylcholine at the neuromuscular junction. Thus,
nerve impulses which would normally cause muscles to contract are
prevented from reaching their supplied muscles,
causing the muscles to relax.