Problems During IV Sedation
Intravenous sedation is a widely used and extremely predictable technique with
an unparalleled safety record within dentistry, which is a testament to the
profession. There are however many potential pitfalls that can catch out even
experienced sedationists ands this article aims to illustrate how to avoid or at
least manage such unexpected events to maintain the safety of the patient.
Correct Assessment
Without doubt the most crucial aspect of sedation provision is a thorough pre-op
assessment and it is here that potential problems can be averted. The
assessment should be carried out at a separate visit, ideally a week before any
planned sedation treatment as this allows sufficient time to carry out further
investigations and the clinician and patient are under no pressure to carry on in
the face of any contra-indications.
The assessment visit is an opportunity to discuss the nature, benefits, risks and
alternatives to treatment under IV sedation and provide the patient with written
pre and post-op instructions. It’s very important to emphasise the importance of
the patient having a responsible adult escort attend with them at the treatment
appointment and also to remain with them for the immediate 24 hours
afterwards.
Patient factors to be checked during assessment:
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Medical history
Drug history
Anxiety level
Alcohol consumption
Baseline blood pressure
Baseline pulse and oxygen levels
BMI
Previous sedation experience
Social factors and availability of an escort
Cannulation site
The following problems can be encountered during intravenous sedation and I
will describe the management of these:
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Failed cannulation
Over sedation
Hiccups
Distressed patient
Excessive doses required
Prolonged recovery
Failed Cannulation
Without doubt the aspect of sedation that causes the beginner the most stress is
accurate cannulation and the feeling that you have to ‘get it first time’! I suggest
that those new to sedation should choose their cases very carefully, perhaps
starting with low anxiety patients having a traumatic procedure e.g. wisdom
tooth removal; this way the pressure is off the clinician somewhat and a less
anxious patient is easier to cannulate. Get a few of these under your belt before
trying it on the shaking, wailing and crying variety.
One helpful tip is to have several cannulae available on the tray so that if the first
attempt fails, you simply reach for another and carry on as if nothing went
wrong. It looks less slick if you have to go rooting through the drawer for a
second one and the patient will think something didn’t go to plan. If you do fail
first time, especially after getting ‘flashback’ then leave the failed cannula in
place, tape it down and try a different vein / site. If you remove the failed
cannula, you will cause a haematoma to form at that site as soon as the
tourniquet is re-applied thus preventing use of that entire arm.
I suggest 3 attempts per arm maximum. If it’s not happening after that abandon
the sedation, review your technique and consult a mentor or more experienced
clinician as you’ve either badly assessed the site at the pre-op visit or your
technique needs some revision.
The two favoured sites are the dorsum of the hand and the antecubital fossa (in
the cephalic vein). The hand presents possibly the most visible and ‘easy’ veins
however patients report much higher pain in this area compared to the ACF. The
ACF can be cannulated almost painlessly but the veins can be harder to locate
particularly in women and those with higher BMI’s. I suggest starting with the
hand as a beginner but pre-warn the patient about the discomfort. Many people
that have been in hospital have had much larger cannulae inserted at this site so
don’t be overly concerned about the pain aspect.
Oversedation
Oversedation is defined as vital sats dropping below the 90% oxygen saturation
for a period of time. It must be remembered that it is the trend that is important
so before the sats actually hit 89%, an eye should be kept on the readings and a
downward trend should alert the clinician to act before the numbers are too low
and the patient is put at risk.
There should really be very little chance of oversedation if the assessment has
been carried out correctly and a slow titration technique used during induction.
Medical issues that may lead to oversedation include un-disclosed drug histories
particularly the use of other sedatives and hypnotics, antihistamines and alcohol
all of which can act synergistically with midazolam. Elderly patients are
particularly at risk of oversedation as their levels of plasma proteins are lower so
less midazolam is bound up and it is the ‘free’ unbound amount that causes
sedation. I suggest titrating at a slower rate in the elderly (over 60 is considered
elderly for the purposes of sedation) and a rate of 0.5mg per minute. It may even
help to dilute the midazolam to 1mg per 2ml so that more accurate titration can
be done. This can be achieved by simply adding 5ml of normal saline to a 5mg in
5ml phial of midazolam.
Higher BMI subjects may also be at greater risk of oversedation as not only does
the fat soluble midazolam disperse into lipid stores requiring higher doses to be
used, the abdominal mass when the patient is laid flat can cause difficulty in
breathing. I advise a cut off BMI of 30 for IV sedation. High BMI also causes issues
with prolonged recovery as will be explained later.
We must always remember that midazolam is fully reversed by administration of
flumazenil (Anexate) and this is totally safe should there be concerns about the
oxygen saturation dropping below 90% and trending further downward after
other methods have not helped.
Hiccups
Hiccups isn’t a serious problem but usually occurs when the midazolam is given
too quickly faster than the recommended 1mg per minute titration. The problem
usually shows when a patient is treated at a second sedation session and the
clinician already knows what dose the patient was comfortable with from a
previous session. The clinician then ‘fast forwards’ the titration rushing towards
the end dose that was recorded at the past session. Here a bolus hits the brain
and causes the hiccup phenomenon. Whilst not in itself a major issue, the fact
that it indicates a bolus dose, it can precede oversedation so the clinician must be
ready for that to occur and deal with appropriately.
Hiccups will pass in time so it may mean a wait of 10 or 15 minutes before the
patient is settled enough to carry on. If hiccups are occurring frequently with a
clinician, they should review their technique and even have a clock to time the 1
minute intervals between increments of midazolam
Distressed Patient
Different patients react differently with IV sedation. Whilst most will be calmed
and sleepy enough to allow treatment to proceed in a clam manner, some will
exhibit distress, cry throughout and have an apparent unpleasant experience.
The distressed patient can be unsettling for the clinician especially one with little
experience of this. What you must remember is that amnesia occurs early on in
the sedation titration so there is a very high chance that the patient did not
remember beiong distressed and their take on the event will be a lot more
positive. I advise clinicians to review sedation cases after a week especially
where patients have appeared distressed and they soon realize that the patients
for the most part found the sedation fantastic!
Success in IV sedation is NOT whether the patient was borderline general
anaesthesia, flat out cold! Success is that treatment was achieved and the
patient’s recollection was a positive one and even the most distressed patient
can have a very positive successful treatment. If they cried all the way through
but kept their mouth open and the dentistry was completed then that is success.
Some patients however show distress and will NOT allow treatment to proceed.
This could be an interaction with medication or just a difficult case. For this
reason, it is best not to be too adventurous in planning a long course of
treatment under IV sedation, particularly when you haven’t experienced how a
patient reacts whilst under IVS. I will carry out a ‘taster’ session perhaps to just
extract a tooth or do a simple filling. That way you will gain an understanding of
how compliant someone will be under IVS. Using that knowledge you can then
decide whether the RCT + crown prep on the UL8 is going to be possible!
Paradoxical reactions can occur under IVS and young patients (under 18) can
show this so we advise limiting IVS in general practice to adult and fully
competent patients. IVS has a place in special needs patients but there are
greater risks of paradoxical and unexpected reactions so unless you work in
these clinics with the appropriate backup, I suggest keeping things simple.
One particular example of a paradoxical reaction happened to me some years
back and it turned out was due to a patient smoking cannabis before their
appointment. I was not told about the cannabis until the following week after
first having to abandon the session due to acute distress from the patient. A
subsequent sedation was uneventful after I had asked the patient to avoid the
drug for 2 weeks. It is always worth asking about ‘drug use prescribed or
otherwise including recreational’ and hoping that patients are 100% honest!
Excessive Doses Required
If we look at the drug sheet in the box of midazolam, we will see that the sedative
dose indicated as 0.1mg per kg bodyweight. Obviously this just provides a
general guide and the correct technique is slow and accurate titration but our
average 70kg man would indicate a 7mg sedative dose. If we think about a
ceiling, many clinicians will accept 10mg as a maximum dose and anyone
requiring more than this may have a medical or physical factor that hasn’t been
accounted for. High BMI patients may require excessive doses due to the high
lipid solubility of midazolam. A proportion of the drug ends up in the large fat
stores so it takes higher doses to achieve sedation. On the flip side, recovery can
be longer as the lipid stored midazolam gradually leaves the fat prolonging the
sedative effect.
Patients that consume above average amounts of alcohol may also demand
excessive doses due to their liver being able to more rapidly metabolise the drug
and their CNS accommodating to the sedative effects of CNS depressants. It is
vital therefore that alcohol consumption is part of the list of questions asked at
the pre-op assessment visit.
Prolonged recovery
The minimum recovery time should be 1 hour from the LAST increment of
midazolam and judged when the patient can walk totally unaided. A type of
sobriety test has to be carried out and standing on one leg, walking unaided or
touching the nose with alternate arms are all types of this. The dentist has legal
responsibility for discharge after they have judged the patient ‘recovered’.
If the patient is not recovered enough to pass the sobriety test 2 hours after the
last increment we have to ask ourselves why. Elderly patients may metabolise
midazolam slower so we can expect a longer recovery time but should still be
comfortably within 2 hours. Patients taking medications that require liver
breakdown by similar enzymes that midazolam needs can prolong recovery. One
common example of this is Erythromycin, the dentist’s staple alternative to the
penicillins. So we a possible scenario of a penicillin allergic patient attending
with a dental infection requiring antibiotics and needing extraction under IV
sedation a week later once the antibiotics have reduced the infection. Any
erythromycin in the liver at this time can dramatically prolong midazolam
breakdown and create a prolonged recovery.
Avoiding problems in the first place
The secret to avoiding the above problems is to carry out a thorough assessment
and emphasise to the patient the need for total honesty in answering medical
and drug history questions. The other important thing to remember is that slow
titration measured against the patient’s responses is the key and always aim to
administer the minimum dose of sedative that will allow treatment to be
completed safely.