Welcome back to the Deep Dive. Today we're doing something a
little different. We are getting right into that
specific headspace of a post grad student at like 3 in the
morning. I know that feeling all too
well. You know it, right?
The coffee is stone cold, You've got Miller's anesthesia open on
one side, the Oxford Handbook on the other, and you're staring at
a topic that looks, I don't know, deceptively easy but is
actually a total trap. The classic wolf in sheep's
clothing topics. They look simple on the
syllabus, but they are absolutely where exams are won
and lost. Exactly.
And the topic is anesthetic management for upper GI
endoscopy and colonoscopy. And honestly my first thought
was it's just a bit of sedation, right?
How hard can it be? And that's the first mistake.
But then I started digging into these notes you sent over,
specifically the sections on RRA, you know, non operating
room anesthesia, and I realized this is actually a minefield.
It is, and that's exactly why examiners love it.
If you walk into Aviva thinking it's just a bit of propofol, you
will fail. I can guarantee it.
The exam question isn't really about the endoscopy itself.
It's about how you manage a compromised airway in a dark
room with limited help on a patient who might be actively
bleeding. It tests your crisis resource
management just as much as your pharmacology.
Yeah, Miller really emphasizes the the hostility of the
environment. It's not the pristine or we're
used to. Not even close.
So the goal today, our mission is to synthesize these heavy
texts into that perfect 15 mark answer for the Gujarat
University MD Anesthesiology exams.
We need to build the structure pre op, intra op, the specific
pharmacology and of course the disaster management.
Right. And there's a core tension.
We need to keep coming back to a central theme, and that's the
concept of the shared airway. In almost every other surgery,
the anesthesiologist owns the airway.
It's our domain. But in upper GI endoscopy,
you're renting space. You're renting it from a
gastroenterologist who is actively, if unintentionally,
trying to obstruct it. That's a great way to put it.
So let's kick this off. Part A introduction and exam
framing. If I'm sitting in the exam hall,
I turn over the paper and I find a long question on this.
How do I even start? Do I just define the procedure?
You start by defining the scope, yes, but you do it to show you
understand the clinical context. So you'd write Upper GI.
Endoscopy, often called EGD or OGD, involves the visual
examination of the esophagus, stomach, and duodenum.
Then colonoscopy is the examination of the lower GI
tract from the rectum to the cecum and sometimes the terminal
ileum. OK, simple definitions.
But you must immediately pivot to the purpose.
Don't just say what they are, say what they're for.
These are diagnostic and therapeutic procedures.
Therapeutic meaning that they might be clipping bleeds or
removing polyps or something like.
That exactly, and that single word therapeutic changes the
entire anesthetic risk profile instantly.
But the most critical part of your introduction, the part that
gets you the marks is to classify this under ONORA, non
operating room anesthesia. You need to write that acronym
down and define it. OK N or R?
Miller makes a very, very strong point here.
Norara is a rapidly growing field and it often involves
sicker patients ASA three and four in what it calls remote
locations. Let's unpack that remote
location aspect a bit in the exam.
Why is that a point worth marks? It's still in the hospital,
right? It is, but remote in this
context means remote from the safety and resources of the main
operating theater. It implies risk.
You're working with limited space, for one.
The room is designed for the gastroenterologist, not for us.
The lighting is dimmed for their screens.
Which means you lose visual cues.
You can't see the patient's color properly.
Precisely. You can't see cyanosis and the
support staff are endoscopy nurses.
They are brilliant what they do, but they are not trained in
anesthetic emergencies in the same way an OR technician is.
You're often physically isolated from backup.
So things go South. You are basically on an island.
You're on an island and you need to have brought all your
equipment and plans with you. That directly leads back to the
shared airway concept we mentioned in EGD.
The endoscope itself is a foreign body.
It's an airway obstruction. It's sitting right there in the
pharynx it. Triggers the gag reflex.
It can cause laryngospasm. You can't easily get a seal to
mass ventilate with a scope in the mouth.
This competition for space is the defining anesthetic
challenge. If you don't mention shared
airway in the first paragraph of your answer, you've missed the
entire point of the question. Got it.
OK, what about other exam patterns?
Where else does this topic pop up besides the long question?
Oh, it's everywhere. You'll see it in short notes,
usually phrased as sedation challenges in colonoscopy, or
maybe Neurala safety principles. But the Viva?
The Viva is where they really get you.
Of course, in a Viva they won't ask you to list facts.
They'll present a scenario. You have a 70 year old male for
an ERCP. 5 minutes in, his saturation drops to 85%.
What do you do? They want to see your thought
process. They want to know you were safe.
Your crisis management algorithm.
Exactly. They're testing your ability to
think under pressure, far from your usual environment.
OK, this is making a lot more sense now let's move to park B
them procedural characteristics and challenges.
So to write a good answer, I need to think like the
gastroenterologist for a second. What are the key procedural
characteristics I need to list out?
First thing is duration and invasiveness.
Usually these procedures are short, you know, 10 to 30
minutes. But, and this is a big but, they
are highly variable. A quick diagnostic look is one
thing. A complex therapeutic ERCP can
take hours. So the anesthetic plan has to be
flexible. It has to be, Yeah.
And generally, the surgical stress is minimal.
It's not like a laparotomy. Yeah.
And that's why we get lulled into this false sense of
security. Right, and positioning is a big
one. I see references to this
everywhere in the Oxford Handbook and Histos.
It's not supine usually. No, and you must know this.
This is a key exam detail. The standard position for both
EGD and colonoscopy is the left lateral position.
It's also known as The Sims position.
You have to write that down. OK, left lateral.
Let's really visualize the setup here.
We know the standard position is left lateral, and that obviously
helps the endoscopist get access.
But looking at the sources, there's a massive anesthetic
safety angle here too, right? It's not just about their
convenience. Crucially, no.
It's not about convenience at all.
It's about physics. It's about safety.
Think about the physics of aspiration for a moment.
In the supine position, gravity is working against you.
Any regurgitated content, any fluid pools at the glottis and
can just fall straight into the trachea.
It's the worst possible position for an unprotected airway.
But in the left lateral position.
Your mouth is now lower than your larynx.
The corner of the mouth becomes the lowest point, so you're
essentially using gravity as a passive suction device.
Anything that comes up will tend to drain out of the mouth rather
than down into the lungs. Which is a huge safety buffer if
you're doing deep sedation without an endotracheal tube.
It's your single biggest safety buffer against aspiration in
that scenario. But, and this is how you show
the examiner, you're thinking at a higher level.
There's a trade off. OK, what's the downside?
While the airway is safer from aspiration, your monitoring
becomes harder. You can't easily see chest
excursion, can you? The patient is on their side,
they're covered in drapes and physiologically you have to be
very careful about VQ mismatch, especially in obese patients.
VQ mismatch. That's ventilation perfusion.
Why is that worse here? Because the dependent lung, the
left lung in this case, is being compressed.
Right by the weight of the other lung and the mediastinum.
By the abdominal contents pushing up in the diaphragm, so
your functional residual capacity, your FRC drops
significantly in that lung. If you have an obese patient,
their FRC is already low. That dependent lung might be
adelectatic before you even start the procedure.
Which means they have less oxygen reserve.
They'll desaturate much faster if they become apnoic.
Seconds if not minutes. So when you write the answer for
positioning, don't just write left lateral.
That's a pass you write. The left lateral position is
utilized for both endoscopic access and to minimize
aspiration risk via passive gravity drainage.
However, it can compromise visual monitoring of respiration
and may reduce FRC in the dependent lung, thereby
accelerating the onset of hypoxia during apnea.
That is the distinction between a pass and a distinction.
Like a fantastic point. OK, now let's talk about
stimulation levels. Is it actually painful?
It depends on which end you're looking at, and this is a
nuanced examiner's love. EGD, an upper GI endoscopy is
not painful in the somatic sense.
It's not like a skin incision, but it is intensely, intensely
stimulating. How so?
Insertion of the scope triggers the glossopharyngeal and vagal
nerves. That's your gag reflex and your
laryngeal reflexes. The body's primal response is to
cough, gag and fight it. So for EGD, you need reflex
suppression more than you need pain relief.
Exactly. You need to Uptown the gag.
You need to make the body tolerate this massive foreign
object. Colonoscopy on the other hand,
is a different beast entirely. Colonoscopy causes true visceral
pain. This comes from 2 main sources,
Gas insufflation, stretching the bowel wall, and traction or
torque on the mesentery as the scope navigates the bends of the
colon. It's a cramping, deep, poorly
localized pain. So to summarize, for the exam,
EGD requires reflex suppression. Colonoscopy requires analgesia
and anxiolysis. That's a very clear distinction.
That brings us to the big topic, anesthetic challenges.
We've mentioned 4R and the shared airway.
What else is really high yield here?
Hypoxia. You need to write that in
capital letters. It is the number one adversary
in the endoscopy suite. And remember what we said about
the environment. You often working in a darkened
room. Right, so they can see their
monitor. Which means, as Miller
emphasizes, clinical observation of cyanosis is almost
impossible. You cannot rely on looking at
the patient's lifts or nail beds.
You rely strictly, and I mean strictly on your monitors,
specifically the pulse oximeter and the cavanagraph.
We'll come back to monitoring in detail.
What about aspiration? This seems a bit controversial.
These patients are technically fasting usually, so why do we
treat them as high risk? Do not under any circumstances
tell an examiner the risk is low.
That's a major red flag. Miller's crystal clear on this.
There are several reasons. First, you have gastric
insufflation. The endoscopus is actively
pumping air into the stomach to see.
What does that do? It increases intragastric
pressure. It blows the stomach up like a
balloon, making regurgitation more likely.
Second, many of these patients have underlying pathology.
They're not healthy volunteers. They have GRDA, hiatus hernia,
esophageal strictures. Their lower esophageal sphincter
is already incompetent. And if they're actively
bleeding? That's the trump card.
That is the absolute indication. If a patient is having an upper
GI bleed. That is a full stomach scenario
by definition, regardless of when they last ate.
Blood is a potent to medic. It irritates the stomach lining.
So if you are doing an emergency scope for a bleed, you must
assume they will vomit you treated as a rapid sequence
induction. OK.
That clarifies a lot. Moving on to Part C,
preoperative assessment. This is listed in our notes as
absolutely essential. So if I skip this in Aviva, I
fail, right? You fail immediately without
question. Safety begins before the patient
even enters the room. You cannot fix a lack of
preparation with agility and skill inside the room.
It's too late by then. So what are we looking for in
the pre procedure evaluation? Where's the focus?
You start with the airway assessment.
Always Morgan is insisting on this.
You must document the Malampatti score, Thyro, mental distance,
neck mobility and mouth opening the full assessment.
But wait, here's a question I've always had.
If we're not planning to intubate, if the plan is just
sedation, why does the Malampatti score even matter?
That is the trap. That is exactly the trap a
junior resident falls into. You assess the airway not for
your plan A, but for your plan BC and D.
For the rescue. Always for the rescue if your
sedation plan A fails, or if they obstruct and you suddenly
can't ventilate them, you need to know immediately if this is
going to be a difficult innovation.
You do not want to be discovering A Mullampati 4
airway with a receded chin after you've pushed a bolus of
propofol and the saturation is plummeting to 60%.
That makes perfect sense. Always prepare for the rescue,
OK? What about comorbidities?
What are the big red flags? Miller points out.
The biggest one, and it's huge in all the Norway our
literature, is obstructive sleep apnea, OSA.
These patients have a collapsible pharyngeal airway.
That's the definition of the disease.
When they sleep at night, they obstruct when you give them even
a whiff of a sedative like propofol or midazolam.
What do you think happened? Instantly.
Instantly and completely. Miller strongly suggests using a
screening tool like Stop a Bang if they are high risk.
For OSA, you need to be much, much more cautious with
sedation. You might even decide Georgia
with a secure airway is the only safe option.
And cardiac disease. For cardiac disease, look at
their functional status. Can they climb two flights of
stairs without getting breathless?
What's their met T score? Miller notes the risk of
ischemia. The procedure itself can cause
stress, tachycardia, hypertension, and a colonoscopy
can cause profound vagal stimulation and bradycardia.
You need to know their cardiac reserve is.
Let's talk about fasting status, the NPO guidelines.
I assume the standard ASA guidelines apply here.
Yes, and you must state them in the exam.
Two hours for clear fluids, 6 hours for a light meal or
formula, 8 hours for a fatty or fried meal.
The 268 rule. Here's the exam trap I've heard
people discuss. Can I get away with being a bit
LAX on this because it's just a minor procedure or just a camera
test? Absolutely not, That's a huge
trap. The exam answer is standard
fasting guidelines must be strictly adhered to.
In fact, you need to show your thinking even more deeply.
Miller warned specifically about gastric emptying issues in
patients with long standing diabetes, Castroparesis.
Right, so a diabetic patient who says they fasted for 8 hours
might still have a stomach full of food from the day before.
Exactly, their autonomic neuropathy means the stomach
doesn't empty properly, so for a long standing diabetic with poor
control you treat them as a full stomach.
Even if they follow the MPO guidelines.
That might be an indication to intubate them rather than just
sedate them. Great point.
Let's touch on some special patient groups.
The elderly, what's the key concern?
Reduced physiological reserve is the umbrella term, but be
specific. Their circulation time is
slower. Miller notes that drugs take
longer to reach the brain. Slower arm to brain time.
So if I push a dose of propofol and nothing happens in 20
seconds and I get impatient and push another ghost.
You've just overdosed them. The first dose hasn't even
arrived at the brain yet. By the time the second dose hits
on top of the first, they are profoundly apnoic and
hypotensive. The mantra for the elderly is
start low, go slow, and wait. They're also much more sensitive
to the cognitive side effects of metazolem, leading to post
operative delirium. OK.
And the obese patient? We touched on the VQ mismatch in
FRC. Yes, but also remember the pure
mechanics of their airway. They have a heavy, thick neck.
When they lose consciousness, that redundant soft tissue
collapses inwards immediately, and because of the weight of the
chest and abdomen, they have that severely reduced FRC.
Their oxygen tank is tiny. They desaturate in seconds, not
minutes. They are the definition of a
high risk airway in this setting.
And finally, patients with liver disease.
Long cases has a whole section on this.
And for good reason. Liver patients are frequent
Flyers in the endoscopy suite for Ferris wheel screening,
banding, things like that. You have three main problems to
worry about. 1 Altered drug metabolism.
Drugs, especially those metabolized by the liver, last
much longer. Two must be Coagulopathy.
Correct bleeding risk during biopsies is high.
You need to know their INR and platelet count and three,
encephalopathy. They are extremely sensitive to
sedatives, particularly benzodiazepines.
Why benzodiazepine specifically? I've heard this before.
They can precipitate or worsen hepatic encephalopathy.
The mechanism is complex, but it involves the GABA receptors in
the brain, which are already up regulated in liver failure.
So Miller advises avoiding midazolam in patients with
severe liver disease if possible, or using tiny,
carefully titrated doses. Propofol is often a better
choice as its metabolism is less dependent on liver function,
right? OK, let's move into Part D,
choice of anesthesia. This is marked in our outline as
Exam gold. So how do I describe the
different options available to me?
You must start by describing the continuum of sedation.
The American Society of Anesthesiologist, the ASA
defined 4 distinct levels. You need to know these
definitions by heart for the exam.
OK, let's go through them. Level 1 is minimal sedation or
anxiolysis. Here the patient responds
normally to verbal commands. Cognitive function might be a
little impaired, but their airway and breathing are
unaffected. Level 2.
Moderate sedation, which used to be called conscious sedation.
This is the key one. The patient responds
purposefully to verbal commands, either alone or accompanied by
light tactile stimulation. The crucial part of the
definition is no interventions are required to maintain a
patent airway. So they're still breathing on
their own just fine. Correct.
Now Level 3 is deep sedation. Here the patient cannot be
easily aroused, but will respond purposefully following a
repeated or painful stimulation. And here's the Cliff edge.
The definition includes the phrase The ability to
independently maintain ventilatory function may be
impaired. So that's the danger zone, the
transition from moderate to deep.
That is the precipice. As soon as you cross from
moderate to deep, which can happen in a matter of seconds
with a drug like propofol, you are effectively inducing general
anesthesia, but without a protected airway.
And the final level, of course, is general anesthesia GA, a loss
of consciousness where the patient is not arousable even by
painful stimulation. And Miller notes, there's been a
real shift in the field here, hasn't there?
Away from the traditional moderate sedation.
A massive shift. Historically conscious sedation
with a combination of midazolam and opioid like fentanyl was the
standard, but there has been a huge move toward propofol based
deep sedation. And why is that?
Three reasons. Better patient satisfaction.
They remember nothing and feel better afterwards.
Faster recovery and discharge times and frankly better
operating conditions for the endoscopist.
The patient is completely still, but it comes to the cost of that
Higher risk of airway compromise in apnea.
Is there a controversy here about who gets to give the
propofol A? Huge controversy.
This is the whole N double AAP debate.
Non anesthesiologist administer propofol.
Stolting discusses this at length.
Can a specially trained nurse or the gastroenterologist
themselves give propofol safely? The FDA label for propofol is
very clear. It says it's for use only by
persons trained in the administration of general
anesthesia. So anesthesiologists would argue
it's unsafe for others to be using it.
The argument is that you need someone whose sole job, whose
entire focus is monitoring the patient's level of
consciousness, their airway, and their hemodynamics.
You cannot safely perform the endoscopy and manage a deep
sedation simultaneously. For the exam and for any high
risk patient, the answer is clear.
Propofol sedation should be administered by a dedicated
anesthesia provider. OK, so sticking with that safety
principle, when do I as the anesthesiologist decided to skip
sedation and go straight to general anesthesthesia?
What are the hard indications for GA?
This feels like a classic exam question.
It's an absolute exam favorite. You need to have a must intubate
list in your head. It's about identifying
unacceptable risks. OK, what's on the list?
Number one, high aspiration risk.
We've already covered this. Active GI bleeding is the
classic example. Blood in the stomach equals a
full stomach. Also known bowel obstruction,
severe GERD or conditions like achalasia. #2.
Uncooperative patients. This could be a child, an adult
with severe anxiety or claustrophobia, or a patient
with cognitive impairment or developmental delay who cannot
follow commands or stay still. That makes sense.
What's #3. Complex or prolonged therapy,
the procedures. Think of ERCP which requires the
patient to be prone or semi prone for a long time, or a
procedure like POEM, paroral, endoscopic myotomy.
Anything where you anticipate it will take a long time and the
patient simply won't tolerate staying in one position under
sedation and the last one failed sedation.
This is a judgment call. If you have given what you
consider to be safe and appropriate doses of sedation
and the patient is still fighting, agitated or
uncomfortable, you don't just keep pushing more drugs.
That's how disasters happen. You stop, you reassess, and you
convert to a controlled general anesthetic.
Excellent. That's a really solid safe list
for an exam answer. Now let's move into the room
part E, intraoperative anesthetic management.
Let's talk about our airway management strategies.
OK, we're in the room for a standard EGD.
Under sedation, you have a shared airway.
You almost always start with topicalization.
You mean like a lidocaine spray? Exactly.
A lidocaine spray to the back of the throat or a viscous gargle.
Morgan highlights this. Why do we do it?
It tons. That gag reflex we talked about?
This makes scope insertion more tolerable and often lowers the
total dose of intravenous sedation you need to give.
And what about oxygen delivery it?
Is mandatory. You never do sedation without
supplemental oxygen. Standard nasal cannula are the
minimum. You can also get specialized
bite blocks now that have a little oxygen port built right
into them, which is quite clever.
I see a high yield note here from Miller about something
else, high flow nasal oxygen HFNO.
Yes, this is a real game changer especially for high risk
patients. You might also hear it called TH
rive Transnasal Humidified rapid insufflation Ventilatory
exchange. OK, that's a mouthful.
How does it actually help in this situation?
It provides very high flows of warm humidified oxygen, up to 60
or 70 liters per minute. This is 2 very important things.
One, it creates a massive reservoir of 100% oxygen in the
pharynx and fills the lungs. This dramatically extends the
safe apnoea time. If the patient stops breathing,
their saturation stays up for many minutes longer give you
more time to intervene. And the second thing.
The high flow generates a small amount of PEEP, or positive end
expiratory pressure. It's only about 5 to 7
centimeters of water, but it's often enough to splint the
pharyngeal airway open, preventing it from collapsing.
Especially in an obese patient with OSA, it's a fantastic tool.
So if we decide to go to GA, the debate is LMA versus
endotracheal tube or ETT. And for an EGD and upper GI
endoscopy, the endotracheal tube ETT is almost always the
preferred device. Why not an LMA?
It's less stimulating, easier to put in.
Because the LMA, by its very design, occupies the pharyngeal
space, it sits right in the hypopharynx, which is exactly
where the endoscopist needs to go.
If you put an LMA in, the scope has to be squeezed past the LMA
cuff. You are literally fighting for
space Lus. The LMA does not fully rotect
against aspiration if the stomach is full of blood or air
from insufflation. But for a colonoscopy.
For a colonoscopy the airway is free O an LMA or even just mask
ventilation is perfectly acceptable if you're doing a
Georgia. But for EGD, YouTube them.
Secure the airway, get it out of the way, and let the endoscopist
do their job. OK, let's talk about the drugs,
sedation and drug consideration. Right.
The pharmacology, as we said, the text describe a massive
shift over the last decade. It used to be all
benzodiazepines and opioids. Now if you read Stolting, it's
practically a love letter to propofol.
But for the exam you can't just, say, use propofol.
You have to be more nuanced. You do you say that Propofol is
often considered the gold standard for outcomes.
It has a rapid onset, a very rapid offset and valuable anti
emetic properties. It is perfect for a high
turnover endoscopy list where efficiency is key.
I see a note here in Sculpting about something called sadasis.
What was that? Oh.
Yes, Sadasis. That was a computer assisted
sedation delivery system. It was a machine designed to
allow non anesthesiologist to administer propofol for
endoscopy. It had built in monitors and
would titrate the drug based on the patient's response.
And what happened to it? Stolting mentions it is an
interesting technological development, but it was
withdrawn from the market. It's a good historical point to
mention in an essay to show you've read the text deeply, but
the principle it highlights remains.
Propofol is a powerful drug that needs very careful continuous
monitoring. What about the traditional
cocktail, the midazolam and fentanyl combination?
It's still used. It's the classic conscious
sedation mix. Midazolam provides excellent
amnesia and anxiolysis. Fentanyl provides that visceral
analgesia needed for colonoscopy.
But here is the massive, enormous trap.
Miller warns in no uncertain terms about synergistic
respiratory depression. This concept blew my mind when I
first read it. I always just thought, oh,
little midazolam, a little fentanyl, perfectly safe.
And that is the trap. It is not an additive effect.
It's not 1 + 1 = 2 with these drugs, it's more like 1 + 1 = 10
when it comes to respiratory depression.
The dose response curve for respiratory Dr. shifts
dramatically to the left. Why?
Is it because they hit different receptors but ultimately depress
the same respiratory center in the brain stem?
That's exactly it. So the exam tip here is crucial.
If you were describing the balance sedation technique, you
must explicitly state that the doses of each drug must be
significantly reduced by at least 50% when used in
combination. If you write down the standard
doses for both drugs given individually, the examiner will
assume you have just rendered the patient APNOEC in the dark
room. That's a vital point.
And what about dexametomidine? Dexametomidine is an interesting
1 long cases mentions it. It's an A2 agonist.
It provides what's called cooperative sedation and some
analgesia, but crucially, without significant respiratory
depression. Patients are sedated but can
often maintain their own airway and breathe spontaneously.
Sounds perfect. Why don't we use it all the
time? The downsides are it's slow on
set and it's long recovery time. It's not ideal for a quick 10
minute diagnostic scope where rapid turnover is needed.
It's much better suited for longer, more complex cases like
an ERCP, where you want the patient to be calm and breathing
spontaneously for an hour or more.
Monitoring. We've touched on this, but let's
drive it home for the exam. What do I need to list?
You list the standard ASA monitors as non negotiable ECG,
non invasive blood pressure, NIPP and pulse oximetry, but for
the exam you must emphasize and maybe even underline
capnography. Miller states that it is now
considered mandatory for any deep sedation in an RR
environment. And why is it so critical?
Why isn't the pulse oximeter this PO2 enough?
Because pulse oximetry is a lag indicator.
It tells you about oxygenation, not ventilation.
If a patient who is receiving supplemental oxygen stops
breathing, becomes apnoic, their oxygen saturation might stay at
98% for a minute or two. The oxygen in their lungs acts
as a buffer, but the capnograph which measures N title CO2 will
show you a flat line immediately.
So capnography measures breathing, while pulse oximetry
measures the consequence of not breathing.
Beautifully put. Exactly.
In that dark room where you can't see the chest moving?
Well, that little waveform on the monitor is your lifeline.
It detects apnoea before desaturation occurs, giving you
a critical head start. And a practical tip, how do you
even measure CO2 if they aren't intubated?
You use specialized nasal prongs that have a CO2 sampling line
built into them alongside the oxygen delivery ports.
It's simple and very effective. Long cases also mentions A
precordial stethoscope. Is that still relevant?
I think it is especially for Pediatrics or even just for your
own Peace of Mind. You tape it to the Super sternal
notch. Having that continuous audible
breath sound is a very reassuring thing in a dark,
quiet room. It's a low tech backup that
connects you physically to the patient's breathing.
OK, we are deep into the procedure now, Part F
Complications and emergencies, the outline says.
This is absolutely essential. It is.
This is where you prove you're a safe anesthetist.
You need to categorize these in your mind and in your exam
answer. There are anesthetic
complications and there are procedure related complications.
Let's start with the big anesthetic 1.
Hypoxia caused, as we've said, by airway obstruction from the
tongue or the scope, or by central hypoventilation from too
much drug. Or you can have laryngospasm.
This is a nightmare scenario. The scope or secretions touch
the vocal cords under light anesthesia and the cords just
snapshot reflexively. You can't ventilate in or out.
And hypotension. Very common, especially with
propofol. And remember why many of these
patients are significantly volume depleted.
They've been fasting, but more importantly, they've taken a
powerful bowel prep, strong laxatives that have dehydrated
them. You then give propofol, A potent
vasodilator, and their blood pressure can just fall like a
Cliff. Fluid resuscitation is part of
the anesthetic plant. Now, what about the procedure
related complications? This is where S dos is a good
reference. The big one is perforation.
The endoscope can literally punch a hole through the
esophageal, gastric, or colonic wall.
S Dos and Miller both warn you to look for the sign of free gas
under the diaphragm on a subsequent X-ray.
But how would you spot that during the case itself?
If the patient suddenly becomes tachycardic, their abdomen
becomes rigid and distended, and they become difficult to
ventilate. But the classic sign mentioned
in S Dos that you might pick up is of cutaneous emphysema.
The air from the gut escapes into the peritoneum, tracks up
the mediastinum, and you can feel this crackling like Rice
Krispies under the skin of the neck and chest.
And if you find that, it's a surgical emergency?
It's an immediate stop. Call the surgeons.
This is a life threatening complication.
And what about vasovagal episodes?
These are very common during colonoscopy.
As the scope stretches the mesentery, it stimulates the
vagus nerve. This can lead to profound
bradycardia and in some cases even a systol.
The anesthesia OSCE books highlight this risk.
You absolutely must have atropine or glycopyrrolate drawn
up and ready before any colonoscopy starts.
OK, so let's go into that war room scenario you mentioned
earlier. You're 5 minutes into an EGD.
The patient is obese. ASA three, you've given some
propofol. Suddenly the pulse oximeter tone
drops. It's not that polite high
pitched beeping anymore. It's that low ominous falling
tone. The screen says saturation is
88% and dropping fast. What is the cognitive flow
chart? What do you do?
The first rule is that panic is the enemy.
You have to rely on your training on the algorithm, and
step one is counterintuitive for the gastroenterologist who is
focused on the procedure. Step one is the procedure stops.
They must hate that, don't they? They're so close.
They just want to finish up real quick.
They do, but you have to be the authority in the room.
Your voice must be calm but firm.
Scope out now, please. You cannot diagnose or fix an
airway problem with a garden hose in the patient's esophagus.
OK, the scope is out. The patient's saturation is
still 85% and falling. Now you assess the mechanism.
Is it central apnea from the drug or is it obstruction?
In Nora? With sedation it is almost
always obstruction. The tongue has fallen back and
is blocking the pharynx. So first maneuver is a jaw
thrust. An aggressive 2 handed jaw
thrust. This serves 2 vital purposes. 1
It physically opens the airway by lifting the tongue off the
posterior pharyngeal wall. Two, it is an intensely painful
stimulus. That pain is often the best
respiratory stimulant you have. Sometimes just that action will
cause the patient to gasp and take a breath.
You can also apply pressure at Larson's Point just behind the
earlobe, which is also very stimulating and can help break a
laryngal spasm. And suction.
Yes, tab suction ready. Clear any secretions from the
mouth, but be gentle. Don't go too deep and trigger
more spasm. And if the jaw thrust doesn't
work, saturation is now 75%. Positive pressure ventilation.
Get a good seal with a face mask and bagging with 100% oxygen if
you still can't ventilate. If the chest isn't rising and
you feel resistance, you are now in a can't ventilate emergency.
You must call for help immediately, and your next step
is likely a muscle relaxant like sucxomathonium to break the
laryngospasm followed by immediate intubation.
And for the exam, the key is showing that stepwise escalating
response. Exactly, but you also add that
early recognition via capnography prevents you from
ever getting to the sucxathonium stage.
If you wait for the pulse oximeter to drop to 85%, you're
already a minute or two behind the event.
The capita graph tells you the second they stop breathing.
Clear and decisive. That's what they want to hear,
right? OK, let's move to part G post
procedure care. The procedure is done.
Can we just send the work to the ward or home?
Not yet. They must go to a dedicated
recovery area. We use a scoring system like the
Aldridge score or a modified PAS that's a post anesthetic
discharge scoring system to assess their readiness for
discharge and in recovery. We are specifically monitoring
for sedation. What exactly is reservation?
It's particularly a problem with drugs that have a longer half
life, like midazolam. The drug circulates, it can be
stored in fat tissue, and then leach back out into the
bloodstream later. So a patient might look
perfectly awake and alert in the procedure room, you wheel them
to recovery, and 20 minutes later they're fast asleep and
obstructing their airway again. This is why a mandatory
monitored recovery period is so important.
Makes sense. OK, the final step Discharge
criteria. This is another exam core topic.
Miller has specific guidelines. Yes, and you must know them.
They must have stable vital signs back to their baseline.
They must be alert and oriented to time, place and person.
They should have no significant pain and minimal to no nausea or
vomiting. But the two big non medical ones
are absolutely critical for the exam and for real life.
What are they? One, they must have a
responsible adult escort. They cannot go home alone, no
Uber, no taxi by themselves. Someone has to be there to take
them home and look after them. And two, they're given explicit
instructions of no driving, operating machinery, or signing
legal documents for 24 hours if sedatives were used.
This is a medical legal absolute.
If they drive home and have an accident and you didn't document
that you gave this specific instruction, you are liable.
Excellent. Now let's wrap all this
knowledge up with Part H comparison and exam integration.
I love a good table. Let's compare endoscopy EGD
versus colonoscopy for the exam paper.
How would we structure that? This is a fantastic way to
present your answer. It shows you can synthesize
information. You draw a simple table with two
columns. For EGD you write Shared
restricted airway, high risk. For colonoscopy, you write
airway is free and accessible. For EGD it's Gaggler and Jill
reflexes. For colonoscopy is visceral pain
from distention. For EGD you write aspiration,
for colonoscopy you write dehydration from prep and vagal
tone stimulation. That's perfect.
And the same for sedation versus general anesthesia.
Another great table. Under pros you write faster
turnover, less invasive, fewer side effects like sore throat.
Under cons you write unprotected airway, variable, depth of
sedation, risk of obstruction. Under pros you write secure
protected airway with an ETT motionless field for the
endoscopist. Under cons you write more
hemodynamic instability, longer recovery, risk of post op nausea
and sore throat. Before we close out, let's hit
some of those common exam questions and Viva traps.
You mentioned trap number one. Can I just do this under local
anaesthesia? The trap is to say yes, of
course the safe and correct answer is only for a very
specific, highly cooperative patient for a brief diagnostic
procedure, and even then you would usually want an
anesthesiologist on standby ready to provide sedation if
needed. You cannot do a complex EGD on
an anxious patient with just a bit of throat spray.
Chap 2. Ignoring the bowel prep.
We mentioned this, but it's a common Viva question.
The examiner says your patient's blood pressure is 90 / 60 on
induction. Why?
You must mention the patient is likely significantly dehydrated
from the bowel preparation. If you just blame the propofol
and miss that key piece of Physiology, you lose marks.
And trap 3 How do you monitor respiration in a darkened room?
If you say I watched the chest rise and fall, you fail.
The answer is primarily with capnography, which directly
measures ventilation, and secondarily with the audible
pulse oximetry tone, which reflects oxygenation.
Miller is very specific on this. Finally, let's talk about
presentation. You mentioned diagrams, yes.
If you have time in a written exam, a simple diagram gets you
extra marks. Draw the Norar airway setup a
simple line drawing of a patient's head in the lateral
position showing the nasal cannula providing oxygen, the
bite block in the mouth and the endoscope going in clearly
separate from the trachea. You can also draw the flow chart
for desaturation, A box saying PO2 falls with arrows leading to
start procedure than to stimulate and jaw thrust, then
to bag mass ventilate and finally to intubate.
Visuals are powerful. Fantastic.
OK, let's summarize this whole session for that final 15 mark
answer. What's the checklist?
Here is your summary checklist. Your concluding paragraph should
hit these. Points safety standards.
Nor are our safety standards, are identical to or are
standards. No shortcuts are permissible.
Pre op assessment is paramount with a specific focus on the
airway and high risk comorbidities like OSA, cardiac
and liver disease. The shared airway is the primary
anesthetic challenge in EGD. Monitoring continuous
capnography is mandatory for detecting apnea early.
Technique. Propofol is the modern workhorse
agent, but you must understand the entire sedation continuum
and the synergetic respiratory depression trap with benzos and
opioids. Complications.
You must be prepared to manage hypoxia decisively and be ready
to convert to a general anesthetic if patient safety is
ever compromised. And to leave our listeners with
something to think about. A final provocative thought.
The debate continues and you'll see it in Stolting and Miller
regarding non anesthesiologist administering propofol.
Is it safe in young healthy ASA one patients?
Maybe the data supports it, but in the sick, elderly, obese,
complex and Nora population that we see more and more of today,
does it compromise the fundamental safety first
principle of our specialty? It's something to think about as
you study and form your own professional opinion.
That's a wrap on this deep dive. You have the notes, you have the
strategy, and you have the mindset.
Now go ace that exam. Safety, preparation, vigilance.
Good luck.