We're going to talk about antiemetic
drugs now. Because post-operative nausea
and vomiting is very common. But the incidence
is predictable and prophylaxis is effective.
So, the APFEL score was developed by Dr. Apfel,
who's a Swedish, not Swedish
excuse me, a Swiss anesthesiologist, who did
a very large meta-analysis a number of years
ago on the many, many trials that have been done
on drugs used to prevent nausea and vomiting.
And he was able to break down the causes
of nausea and vomiting into 4 categories,
each of which had equal importance in terms
of creating post-operative nausea and vomiting.
So, unfortunately for women, one of the points is
for female gender. One of the points is for
non-smokers. So, the only thing I'm aware of,
where smoking actually helps you is it reduces
your chances of post-operative nausea and vomiting.
You get 1 point for a history of previous post-operative
nausea and vomiting, or a history of motion sickness.
And you get 1 point if opioids are required
for post-operative pain relief.
And if you look at this, you can see that each of these
points is worth about a 20% chance. So the cumulative
effect is that, if you have 4 points, you have
a 80% chance of having nausea and vomiting
post-operatively, unless you're given
prophylaxis. And we can reduce
this incidence, even in somebody with
a score of 4, to around a 10% chance.
So it's well worth doing. The most effective
drugs are 5-HT1 antagonists
(ondansetron, dolasetron, granisetron,
tropisetron). And patients with
a cumulative APFEL score greater than 1,
should receive one of these agents. So basically,
in my practice, every single woman gets this drug,
one of these drugs. And the one we use
is ondansetron. Second level of prevention
is to use dexamethasone,
which by itself is not an effective anti-emetic
for post-operative nausea and vomiting.
But in combination with the 5-HT antagonist
it actually has a cumulative effect
and it's very effective. So my actual practice,
because I come from a place where smoking is extremely
rare, about 8% of the adult population,
is to give every woman dexamethasone
and ondansetron as part of prophylaxis.
If their score is greater than 3 or 4,
they should be given dexamethasone,
a 5-HT3 antagonist, and an anesthetic
which avoids opiates. If opioids
can't be avoided, consider try
using regional anesthesia or TIVA with Propofol.
Propofol has very profound
anti-emetic effects of its own. Prophylaxis
of PONV is more effective than
treatment. So always consider adding
prophylaxis to the anesthetic regiment.
And interestingly, on surveys that have been
done of patients, of the thing they
fear most about coming into the hospital for surgery
and anesthesia, number one in every survey that's
been done is nausea and vomiting, not pain.