Hello ladies and gentlemen.
Welcome back to our ongoing
series of lectures on Anesthesiology. In this lecture
we're going to talk about General Anesthesia.
And we're going to review many of the devices
that we talked about in the last
lecture. So you'll get to see some of the devices and how
they are used. We're going to start with our agenda for
the talk and it will include Pre-Operative Assessment
of the patient, which is a very important aspect
of the anesthesiologist's care of the patient.
We're going to talk about Evaluation of the Airway.
Induction of general anesthesia. Securing the airway.
Maintenance of general anesthesia.
Reversal of muscle relaxation if necessary.
Recovery from general anesthesia.
Management of pain. And Recovery
room care of the patient.
So, immediately before surgery, or days
before surgery, patients undergoing any form
of anesthesia require an Anesthetic Assessment.
This could be immediately before
surgery, if the surgery is a fairly straightforward
simple procedure, and the patient is known to
be healthy before you go ahead
with the surgery. Surgery
will be canceled at this point, if the anesthesiologist is dissatisfied
that the patient is safely prepared for surgery.
So there is an incentive for surgeons to make sure
that their patients are seen by anesthesiology
in advance of their admission to hospital. In many
hospitals, including my own, patients are seen
days to weeks before surgery, so that
the anesthesiologist can assure that the patient
is fully prepared for surgery. So what do we ask about?
What do we do when we see these patients prior
to the surgery? Well, we get a full history of previous
anesthetics, we get a family history of anesthetic problems,
particularly if there's any history of Malignant
hyperthermia or Pseudocholinesterase deficiency.
We examine the airway, lungs and heart,
and we do a general history and physical
for other potential medical conditions such as diabetes,
heart disease, asthma, rheumatoid arthritis, etc.
Almost any medical disease has
some anesthetic implications.
We're the airway experts, so it's
really important that we maintain
an open airway during surgery. One way of doing
this is using a Guedel airway, which is
the little hooked airway most of you have seen,
goes in the mouth and holds the tongue forward.
This is often useful in preparing the patient
position for intubation. So after they're
induced, but before intubation, you can use the Guedel
airway. We're going to talk about the laryngeal
mask airway, which is very useful for maintaining
an airway during surgery, particularly in patients who
are maintaining spontaneous ventilation. This device
is also useful for maintaining oxygenation
in a difficult airway situation. Additional
helpers include the stylet,
which I described earlier, and the bougie, which is basically
a long, very thin device that can go through
the endotracheal tube, and can act as a guide for the endotracheal
tube, through the cords and into the trachea.
And then a number of devices for visualizing
the airway, including the standard laryngoscope,
a device known as a Glidescope,
a Storz Videoscope, and the fiber optic
bronchoscope. So part of the airway
assessment is to do a Mallampati Score.
And a Mallampati Score is extremely easy to do
and everybody gets it done. Basically,
the patient should be sitting between 30 and 45 degrees,
open the mouth as wide as possible and extend
the tongue as far as possible. They should not say,
“Aahh.” If it's a Mallampati I, you can see
all the teeth, you can see the hard palate, the soft palate,
the uvula, you can see right into the oropharynx.
Mallampati II, the uvula, the tip of the uvula
gets cut off, it's a little harder
to see the oropharynx, but you can still get a pretty
good view. Mallampati III, you've lost the uvula,
and you can only see perhaps just a tiny bit
of the oropharynx. In Mallampati IV, you basically
see tongue and very little else.
It's an incredibly easy test
to perform and everybody gets it done. Problem is,
it isn't very sensitive and it doesn't really tell us very
often that we're going to have problems.