hi everyone and welcome to abc's of anesthesia and today i'm going to talk about a four-step
post-operative nausea vomiting plan or the four-step ponv plan let's get started
when i first started anaesthetics i kept hearing about this term p-o-n-v these four letters p-o-n-v
i'd really know not much idea about what they stood for because i'd never heard them in the
rest of my medical training but it's just one of the most common things you'll hear about and purev
stands for post-operative nausea and vomiting you might hear pov which is postoperative vomiting
and post discharge nausea and vomiting or pdnv so a few terms that i've kind of set out quite a lot
in anesthesia but not in most other specialties and again why is this so important like nausea
and vomiting for most people is just something you might have you know when you eat when you've
eaten something a bit funny or maybe you've gone on a car trip or a plane ride and you feel a bit
nauseous but in anesthesia and perioperatively it's a really big deal so they say that about
thirty percent of the general surgical population could suffer from postoperative nausea and
vomiting and this can rise up to eighty percent so the eight out of ten people who are at higher risk
or who have the high risk factors may um suffer from pnb or post-operative nausea and vomiting
and this is a really big deal so you know not only is a major patient satisfaction issue like
essentially patients care as much about nausea and vomiting after their operation as they do
about pain so a really big patient satisfaction issue but also imagine a patient who has had you
know meant for a day operation or day surgery they've got post-op nausea vomiting and they
just can't be discharged because they can't eat adequately they can't drink adequately and they
just can't do their normal activities as a daily living and so this is a really big deal you know
severe unretracting nausea in vomiting is a real problem so now this can be even more dangerous
for particular surgeries now imagine someone's had near a neurosurgical operation or they had
some kind of bowel operation or stomach operation suddenly a patient who is actively vomiting and
the amount of intracranial pressure rise or the amount of muscle contraction that occurs can
severely compromise the surgery itself so again pnv a massive issue it's common it can be serious
it can delay discharge and it can cause surgical complications as well so we need to know about it
now what i really want to do with all of these presentations is to give you information that's
not just my opinion i want it to be as well evidence-based as possible and the great thing
is that there's so many things out there there's so many resources out there and this is one of
them so the fourth consensus guidelines for the management of post-operative nausea and vomiting
so this was recently redone so 2020 was what it was published in a very reputable article
and tj gan and his team essentially some of the main players in this field of nausea and vomiting
management and also in all the iterations of the guidelines so there's a fantastic guideline and a
lot of the information i'm going to present now in a concise fashion is from this incredible document
and i'll put the link in in the story notes for that document as well so you know you can have
a really good read and get into the absolute fine detail but right now i'm here to give you
a four-step plan so you can just get into your anaesthetic training you can get into theater and
do a really reasonable approach or management plan for someone who's at risk of ponv now this article
this review article which gathered a lot of the most current evidence and all the evidence through
an incredible literature review by a great panel of experts in this area they had a few aims and
obviously we're not going to go through all of these things but the aims included identifying
reliable predictors of po v risk in adults and post-operative vomiting in children establish
interventions to reduce the baseline risk of ponv assess the efficacy of individual
anti-medic and combination therapies and including non-pharmacological intervention interventions and
ascertain the efficacy of po v and postage size nausea and vomiting treatment with or
without prior purity prophylaxis determine the optimal dosing and anti and timing of antimatter
prophylaxis appraise the cost effectiveness create an algorithm as well as evaluate the
management of pure v and also propose a research agenda for future studies so we'll go through
the most clinically relevant stuff in all of those aims from this incredible document so the first
thing i want to mention is that you'll hear a lot of risk factors for post-operative nausea vomiting
and a lot of this might be just anecdotal evidence or an anecdotal experience and just people saying
things that they've seen in the past so the great thing about this document they've gone through a
massive literature review over decades to find out what these risk factors really are and how
significant they are so this table here will go through pretty much the evidence-based factors
or risk factors and this is what we're going to use for our four-step process so firstly
positive overall with levels of evidence female gender history of ponv or motion sickness
non-smoking younger age general versus regional anesthesia use of volatiles and nitrous oxide
post-operative opioids duration of anesthesia and the type of surgery now interestingly there
was really conflictive evidence for asa physical status so the sicker the patient not necessarily
the more nausean vomiting is is uncertain menstrual cycle wasn't really correlated level of
anesthesiologist experience wasn't correlated and perpetrative fasting was also undecided
now interestingly disproven things or that with limited clinical evidence was a high bmi anxiety
having a nasogastric tube having a migraine and supplemental oxygen so good to know that some
of these things are just not risk factors as we know so far so this table is really interesting
because it essentially correlates the number of risk factors with this dramatic rise in the
risk of post-op of nausea vomiting so zero risk factors is you know 10 so your baseline risk is 10
already so one in 10 people having an anesthetic will have nausea vomiting from that baseline risk
with one respect it jumps to 20 percent two risk factors jumps to 40 percent
three risk factors 60 and forest factors 80 so just think of that incredible rise
your patients come in most of them will come in with a couple of risk factors
they've got a baseline level of probably you know 40 and even 60 percent of the risk of
having nausea vomiting in this parabrief period so this is a really significant issue so let's
get cracking with the crux of the matter so what i want to give you is that four-step
pov plan that you can implement into your practice straight away so the four steps are calculate
the risk lower the risk use preventative agents and then use treatments or rescue treatments so
calculate risk lower risk preventative treatment and rescue treatment is your four-step plan
so what i do in real life i go and assess my patient as i would for any anesthetic assessment
and then after my assessment i can tally up these risk scores so is the patient female
do they have a history of postoperative nausea and vomiting are they a non-smoker
what kind of surgery are you having is it gynae surgery laparoscopic surgery bariatric surgery or
is it a cholecystectomy these are the surgeries that might increase the risk in adults so most
people look at the duration of the surgery so most surgeries will be under an hour most you know
basic day surgeries will be under an hour but if it if the surge is greater than an hour calculate
that as one extra risk factor now the actual study which was published in 1999 i'll put the link
to that below is interesting because they showed that an increase in 30 minutes duration of surgery
increased the risk of nausea vomiting by something like 50 percent uh so quite a remarkable increase
and that was a study of you know reviewing over 17 000 patients so really interesting but old study
so most of us would just look at the duration of greater than hour as being significant
now this paper also talks about younger age and i looked into it again the same study
of the of the 17 000 patients showed that an increase in age by 10 years
decreases the nausea vomiting risk by 13 so if you round it off increase 10 years decrease by 10
so all i do practically speaking if my patient is under 50 years of age then i think that's an extra
risk factor so just giving you a practical version of some very nuanced information so at the end of
your patient assessment how many risk factors do you have and roughly we'll group this into
one or two risk factors or greater than two risk factors and we'll get to that in a second
the next thing you do in general is to lower the risk as appropriate for example you can do quite
a few things um obvious things like avoiding nitrous oxide you might want to avoid volatile
anesthetics you might want to use regional or local anaesthetic anesthesia or try opioid
sparing techniques so these are all the things that you can do to lower risk there's certain
things you can't do for example you can't change the patient's age you can't really change the
surgery or the duration of surgery so these are some easy modifiable risk factors that you can do
now the next thing is how do you decide on preventative treatment now this guideline has
a really lovely flow chart and it talks about if their patient has one to two risk factors
give them two agents and i mean practically speaking that's a lot of patients will have
one to two risk factors think about any patient under 50 female non-smoker having post-operative
opioids it's very easy to have one to two risk factors and this guideline would recommend that
every one of these patients gets two agents now if the patient is at higher risk they're greater than
two risk factors you'd want to give three to four agents and so that's how they stratify their risk
and their preventative treatment interestingly you want to now know what what agents you can
give and there's so many different agents and you'll have to really be guided by your local
protocols and what your hospital can provide but generally speaking your citrons your endanzatrons
are 5ht3 or serotonin receptor antagonists your corticosteroids like dexamethasone really helpful
dopamine receptor antagonists like dro peridol are commonly available antihistamines these
include promethazine and cyclazine using propofol nk1 receptor antagonists are newer agents like
apriptant which are available now anticholinergics like hyacine and acupuncture so the pericardium
six or pc six point is actually well evidence based for preventing noise and vomiting as well
so there's a whole range of agents that you could use and i'll give you my kind of opinion
of what i do in my practice in my in my hospital setting at the end of the at the end of the talk
so with rescue treatment i think the first thing to know is if your patient is vomiting
you really need to assess the patient for example nausea vomiting could just be the normal
expected complication of anesthesia surgery and the patient or it could be something more
serious for example maybe there's been a surgical problem maybe there's been wound adhesions or some
kind of ultra problem with the repair then you want to know that that's happening so you need
a surgical assessment likewise one of the first signs of severe hypotension in patient can be
nausea vomiting if you've ever seen a patient have a vasovagal faint they'll often complain of
feeling nauseous or a bit off before they faint so i want you to take it very seriously and be
able to assess the patient or have your nurse or assistant or trainee colleague assess the patient
and don't and you know not just give treatment without doing the you know the formal processes
and then you give an agent so if you've ruled out all the serious things that could have been going
wrong with this patient then you can go ahead and give some preventative some rescue treatment
and what we usually recommend is give an agent from another class so if you've already given
say a corticosteroid and an anti-dopaminergic agent you might try and on dance toronto one of
the 5ht3 receptor antagonists or an antihistamine so now what do i do in my practice again depending
on what's available to you in your hospitals this will change dramatically but pretty much
most patients like i mentioned we have one to two risk factors and so i would often do the standard
thing which is avoid nitrous there's minimal benefit for giving nitrous in most circumstances
and i'd give either volatile or proper anesthesia just depending on all the other factors what would
be best for the surgery or the patient i always provide multimodal illness easier because that's
got really good evidence base for being effective for pain relief and also decreasing the dose of
each agent and decreasing opioid use and then give a local anaesthetic or regional if indicated so
i'm avoiding nitrous and i'm considering all the other usual things that i do at the start
of the case i'd always give four milligrams of dexamethasone slow iv and remember never give this
in a awake patient especially rapidly intravenously because you can get some really
interesting and weird side effects like perianal burning so the patient is anaesthetized and i give
it slowly uh four milligram four milligrams iv now you might give eight milligrams uh in this paper
they show that there's probably no difference in four milligrams to eight milligrams there's no
good evidence that eight milligrams is going to be better so you know i just give four milligrams and
that's best given at the start of the case at the end of the case i generally give dro peridol 0.625
milligrams iv and this is anti-dopaminergic agent and both of these agents dexamethasone
and troperidol have a fantastic number needed to treat so the number needed to treat us about five
prevent one episode of nausea vomiting you have to treat five patients and that nnt or number needed
to treat is incredibly effective now those are the two antimates i would give routinely to almost
every patient and then for a rescue treatment i'd have a dance tron and an antihistamine
like promethazine or cyclazine handy so again undancedron and cyclin fantastic number need to
treat i think it's about five for both of them as well um and just really effective at rescuing if
someone has nausea vomiting as well now you might get questions about dro peridol now dryparadol
um there was a i think is about 2001 or so that there was an fda black box warning and this
was due the risk of prolonged qt now this paper goes into a lot of large studies that shows that
at higher doses i think maybe over 25 milligrams or some really high dose that we're not using for
post-operative nausea vomiting prophylaxis maybe there's a risk of this but large studies showing
large numbers of patients having small doses like 0.625 milligrams had no issues with you know
ventricular tachycardias or prolonged qt that was sustained in any way so have a read of the article
make sure you're comfortable with that but also again just be guided by your hospital protocols
because these are systems that are in place to keep your patients safe it's probably worthwhile
also noting that you know giving promethazine intravenously does have some risks if the cannula
is tissued you really don't want subcutaneous promethazine it can have a lot of problems there
so you know sometimes there's advice about giving it as a deep intramuscular injection but yeah
again read the article have a look at the data out there and again follow your normal protocols now
let's go to the higher risk patients now imagine you've got a patient who has any combination of
these problems or high risk factors maybe they've had a history of really severe ponv that's lasted
for hours if not days maybe they've got multiple risk factors and you already know how to calculate
those risk factors and maybe the danger of nausea vomiting is really really deadly for example
they've had that abdominal or gastric operation or they've got that neurosurgery operation and
you really don't want someone straining and increasing the intracranial pressure so you've
got this really high risk patient what do you do then so i do a lot of this the same things but i'd
then take it to the next level for example i would always avoid nitrous in these cases i would run
proprovole tivo again if you're not familiar with doing that it has its own peculiarities and risks
so make sure you do it supervised make sure you're very comfortable doing that and run it with a
bispectral index or awareness monitor as well i'd give multiple allergies as normal i've tried
opioid sparing techniques i might try a regional local anaesthetic approach so for example in new
research cases how could you possibly do regional anesthesia to decrease the amount of opioids to
use it's quite easy so this is one definitely one to look up and there's a couple of resources
out there for regional anesthesia but you can do a scalp block which targets a lot of the nerves that
supply around the scalp and they're incredibly effective just giving lignicaine with adrenaline
just at the right sites means that you can get really good prolonged block for hours
which is again fantastic for decreasing opioid use and keeping your patients awake and insulated
and free of nausea vomiting as well so ask your supervisor find out how to do scalp blocks in
these cases because they're incredibly effective for pain management as well as decreasing nausea
vomiting due to opioid use so what would i do intraoperatively again i'd probably give
dexamethasone eight milligrams at this point give at the start of the case again watching
out for making sure that i'm giving it slowly so i don't get those side effects and also cautioning
in patients with diabetes as well then i'd give dro peridol anondanstron at the end of the case
so on that's from four milligrams drop peridot 0.625 milligrams iv and then i'd have ondansetron
as well as an antihistamine available in recovery like promethazine or cyclazine
you might want to add in an anticholinergic like scopolamine you might want to add in an
nk1 receptor antagonist if that's available to you at your hospital so i hope that was useful
in summary that's the four-step ponv plan it means you've got to calculate the patient risk
you can lower the risk with some simple maneuvers and simple techniques you can give preventative
drugs and medications and you can have rescue medications from another class that's the
four-step plan really easy and i hope that you can find that useful and really practical to start
even on your first day of anesthesia so thanks very much for watching abc's of anesthesia please
share with anyone who might be interested and thanks very much for watching see you next time
you