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Pre-Surgical Information
Spaying or neutering your pet is a big step! There is a lot to consider
when we are planning your pet’s surgery. Here is some information to help
you make wise decisions.
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Special LibraryOur Special Library
is a collection of informative articles on a variety of health topics.
Click here . . .
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Discharge InstructionsClick here for
information on how to care for your pet at home.
Click here . . .
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Anesthetic Monitoring
Which would you rather have, a lousy surgeon and a great
anesthetist, or a great surgeon and a lousy anesthetist?
I think I would go with the lousy surgeon and the great
anesthetist, because at least I would survive the
operation to sue Dr. Fumblefingers later for his botched
surgery. The realities of surgery are that
your anesthetist has a far greater opportunity to kill
you than your surgeon does.
Some of us will remember a music group called the Bee
Gee's. In 1997 they wrote a smash hit called Stayin'
Alive. What was Stayin' Alive about? Hard to
tell, really. The Bee Gee 's
were famous for a lot of things, but clear diction and
crisp enunciation weren't among them. I could
never really tell what Stayin' Alive was about.
In an anesthesia setting, it's a lot easier to tell what
stayin' alive is all about. Stayin' alive is all
about the body's ability to get oxygen to the tissues
and get carbon dioxide away from them, at least on a
short-term basis. It's that simple. To do
that, it takes breathing and it takes blood flow.
But not just any breathing and not just any blood flow.
The breathing must be deep enough to actually exchange
gasses, and it must be regular. We supplement
oxygen during surgery, and that helps get oxygen in to
the blood, but oxygen does nothing to help carbon
dioxide get out of the blood. You have to be
breathing.
Then the bloodflow must have blood adequate pressure to
reach all the tissues. The maximum pressure can't
be too high, and the minimum must not be too low or you
can get into trouble. That means that you have to
have a heart beating in a normal rhythm and a normal
rate, with normal strength, and you must have normal
vascular tone.
How do we make sure all this is happening? It's a
little thing I call anesthetic monitoring. Every
body, both human and animal, is different.
Although there are "standard doses" of anesthetic drugs,
the reality is that the response to these standard doses
is different between individuals. For that reason,
anesthetic drugs are given "to effect," meaning that you
give only as much as is needed to produce the desired
effect and no more. It takes constant monitoring
to be sure that we have given enough but not too much.
As part of this monitoring, we check the following:
| Heart Rate |
Heart Rhythm |
Pulse Quality |
| Oxygen Stauration |
Capillary Refill Time
|
Jaw Tone |
| Eye Position |
Muscle Tone |
Body Temperature |
| Blood Pressure |
Mucous Membrane Color
|
Carbon Dioxide Levels |
Some of this checking is done with our eyes, ears, and
hands. While this is a low-tech approach, vital
information is obtained this way that could not be
obtained any other way. Mechanical and electronic
monitors are important, but nothing can replace trained
eyes and hands and ears. Our anesthetic monitoring
is done by a dedicated technician. Here, the word
"dedicated" is not talking about his or her devotion or
work ethic. It means that our anesthesia techs are
in the surgery room doing nothing but monitoring.
They are not running back and forth to the next room
doing laundry.
To supplement our techs' trained ears and eyes and
hands, we use a variety of electronic monitors. For
instance, we have two instruments which measure blood
pressure.
  The instrument on the right is a doppler unit used to
measure blood pressure in the smaller patients.
The instrument on the left is a dynamap, an
oscillometric unit used to measure blood pressure in the
larger patients. Measuring blood pressure is vital
to stayin' alive, since low blood pressure, or
hypotension, can be devastating to the patient.
If the blood pressure is low, not enough blood will
circulate to provide oxygen and remove carbon dioxide.
The tissues begin to die. This is not good,
especially if those tissues are in the brain or kidney,
the first two organs to suffer when blood pressure
drops. As CO2 accumulates, blood pH changes, and
so none of the complex biochemistry that happens in the
body works right. As the heart suffers from lack
of oxygen and CO2 build-up, it becomes weaker and able
to pump even less blood, then eventually goes into
abnormal rhythms and then arrest. You get the
picture.
Low blood pressure is a common finding in anesthetized
patients. We estimate that as many as 30% to 40%
of our anesthesia patients will experience hypotension
at some point. This is not due to something we are
doing wrong. It happens to humans under anesthesia
too. Uncorrected, it can pose serious
problems. Follow the link
Intra-Op Hypotension for a detailed explanation.
 Breathing is the second thing we monitor electronically.
Besides counting the number of respirations in a minute,
we also monitor the actual gasses in the blood.
The instrument below is a pulse oximeter. It
measures how much oxygen is dissolved in the blood.
If the patient is breathing adequately, the oxygen
saturation (or SaO2) will be high, near 100%. This
means that the blood is carrying all the oxygen that it
can. To tip the scales in our favor, we supplement
oxygen to anesthetized patients. Under anesthesia,
patients are breathing 99% oxygen ( plus 1% anesthetic
gas), as compared to room air which in only about 21%
oxygen. If breathing is not adequate, the percent
of oxygen saturation in the blood will drop, and our
pulse oximeter will tell us when this happens. You
can have regular breathing at a normal rate, but if the
breathing is not deep enough or if there are some lung
problems, not enough gas will be exchanged and
oxygen saturation will drop.
 Another type of respiration monitor is the
capnograph.
The capnograph measures the amount of CO2
that is expired. Because our patients are
breathing 99% oxygen, it really takes some serious
breathing problems to make the oxygen saturation go
down. However, supplementing oxygen does nothing
for helping the body expel CO2. Thus, when the
breathing first starts to get a little marginal, the
oxygen saturation will not change much, but expired CO2
(end-tidal CO2, or etCO2 as it is called), will start to
rise. Rising end-tidal CO2 is a very sensitive
early warning sign of respiratory problems.
The last monitor we will discuss in the electrocardiogram. Also called
an ECG for short, this TV-like device can also provide vital information.
Just because the heart beating does not mean that the heart is actually working
correctly. Sometime abnormal rhythms happen, often in response to low
oxygen and high CO2 situations, that seriously imterfere with the heart's
ability to pump blood, and which can sometimes progress to actual cardiac
arrest. To monitor the heart's rhythm, we sometimes we use an ECG machine.
The ECG machine measures the electrical wave form of the heart.
 Each monitor has it's good points and it's
bad points. The ECG, for instance, can appear perfectly normal for up to
ten minutes after the patient is clinically dead. The Pulse Oximeter can
register normal readings even though blood pressure has dropped to harmful
levels. The blood pressure monitors can give normal readings even though
there is no oxygen in the blood. A patient can appear normal to a trained
technician but be one heart beat away from arrest with an abnormal heart rhythm.
It takes a combination of close observation plus thoughtful interpretation of
all the monitoring numbers to provide safe anesthetic monitoring.
One of the most important things is to have someone actually paying attention to
the patient and the monitors. We have discussed the importance of a
dedicated technician earlier. It is a full-time job monitoring anesthesia.
To the right is an image of our monitoring chart. Our techs monitor the
patients continuously, but record values every 5 minutes or so. The chart
helps us to spot trends and to record interventions.
To summarize, anesthetic monitoring is the key to
Stayin' Alive during
anesthesia. We use a variety of modalities: sight, touch, hearing,
as well as various electronic senses to help us make sure our patients are doing
well. We use a dedicated technician, and use an anesthesia chart to record
what happens and to monitor trends. This is a very high level of care, a
best practice, and makes anesthesia as safe as can be.
Click the link to return to the
Consumer Guide to Elective Surgery
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