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Postoperative Nauseaostoperative Nausea
& VomitingVomiting
Annlynn Annlynn KuokKuok
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One of the most common and distressingOne of the most common and distressingsymptoms to followsymptoms to follow anaesthesiaanaesthesia and surgery isand surgery isPONVPONV
Considered by some patients to be even worseConsidered by some patients to be even worsethanthan postoppostop painpain
Intractable PONV is the most frequentIntractable PONV is the most frequent
anaestheticanaesthetic-related cause for unanticipated-related cause for unanticipatedhospital admission of surgical day caseshospital admission of surgical day cases
Reported incidence is around 20-30% for up toReported incidence is around 20-30% for up to
24 hours24 hours postoppostop
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Overviewverview
PhysiologyPhysiology
Aetiology Aetiology
Associated factors Associated factors
ManagementManagement
PreventionPrevention
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Physiologyhysiology
Vomiting reflexVomiting reflex
Afferent inputs Afferent inputs
Processing centreProcessing centre
Motor Motor efferentsefferents
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Vomiting Centreomiting Centre
Located in the medullaLocated in the medulla
Represents multiple nuclei involved in the
integration of the vomiting reflex
The motor component of the vomiting
reflex is mediated by both autonomic and
somatic systems, whose activity iscoordinated in the vomiting centre
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Afferent pathwaysfferent pathways
Gastrointestinal tract (5HT3, D2)Gastrointestinal tract (5HT3, D2)
MechanoreceptorsMechanoreceptors located in the wall of the gut are
activated by abnormal distension, contraction,
physical damage or manipulation during surgery
ChemoreceptorsChemoreceptors located in the mucosa arelocated in the mucosa are
triggered by noxious chemical stimulitriggered by noxious chemical stimuli
Information relayed via theInformation relayed via the vagusvagus nerve to thenerve to thenucleusnucleus tractustractus solariussolarius in the vomiting centrein the vomiting centre
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Afferent pathwaysfferent pathways
Chemoreceptor Trigger ZoneChemoreceptor Trigger Zone
Area Area PostremaPostrema
Located in the floor of the 4Located in the floor of the 4thth ventricleventricle
Defective BBB for detecting circulatingDefective BBB for detecting circulating
toxins in the blood and CSFtoxins in the blood and CSF
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Afferent Pathwaysfferent Pathways
OthersOthers
Vestibular system: responsible for motionVestibular system: responsible for motion
sicknesssickness
Cardiovascualr Cardiovascualr system: afferents fromsystem: afferents fromcardiac ventricles and blood vesselscardiac ventricles and blood vessels
Higher Higher centrescentres: limbic system, olfactory and: limbic system, olfactory andvisual cortexvisual cortex
Pharyngeal afferents (?gag reflex)Pharyngeal afferents (?gag reflex)
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Efferent pathwaysfferent pathways
Vomiting reflex is divided into 2 phasesVomiting reflex is divided into 2 phases
Pre-ejection or Pre-ejection or ProdromalProdromal phase: relaxationphase: relaxationof the gastric muscles followed by smallof the gastric muscles followed by small
intestinal retrograde peristalsisintestinal retrograde peristalsis
Ejection phase : comprises of retching and
vomiting with expulsion of gastric contents.
Mediated by autonomic and somaticMediated by autonomic and somaticsystems, coordinated in the vomitingsystems, coordinated in the vomiting
centrecentre
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Diagram toDiagram to
summarisesummarise
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Risk Factorsisk Factors
Patient factorsPatient factors
Preoperative factorsPreoperative factors
IntraoperativeIntraoperative factorsfactors
Anaesthetic Anaesthetic factorsfactors
Surgical factorsSurgical factors
Postoperative factorsPostoperative factors
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Patient Factorsatient Factors
Age Age Highest in 6-16 age groupHighest in 6-16 age group
Gender Gender Women 2-4x more likely than menWomen 2-4x more likely than men
ObesityObesity
Non-smoker Non-smoker GastroparesisGastroparesis
Diabetes, hypothyroidism, pregnancy,Diabetes, hypothyroidism, pregnancy, h/oh/o swallowing blood,swallowing blood,
full stomach, intra-abdominal pathologyfull stomach, intra-abdominal pathology History of motion sickness, PONVHistory of motion sickness, PONV
Chemotherapy patientsChemotherapy patients
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Preoperative Factorsreoperative Factors
FoodFood
Prolonged pre-op fastingProlonged pre-op fasting
Not starvedNot starved
Anxiety Anxiety
PremedicationPremedication
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Intraoperativentraoperative factors:factors:
Anaestheticnaesthetic Intubation
Deeper plane of anaesthesia
Gastric inflation during mask ventilation
Intraoperative dehydration
Drugs : Opioids, Ketamine compared with propofol andthiopentone
Inhalation Agents: N20 compared with sevoflurane,isoflurane, desflurane
General anaesthesia compared with spinal andregional anaesthesia
Neostigmine: in high doses
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Postoperative factorsostoperative factors
Head movement of patient after waking
Postoperative pain
Early ambulation, dizziness
Early intake of food
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Surgery factorsurgery factors
Duration of surgeryDuration of surgery
Type of surgeryType of surgery
GynaecologicalGynaecological
ENTENT
Abdominal Abdominal
Head+neckHead+neck
Squint correctionSquint correction
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Management:anagement:
Pharmacological Prophylaxisharmacological Prophylaxis
Multiple receptors involved in theMultiple receptors involved in the
vomiting reflexvomiting reflex
5HT-35HT-3
D2D2
M1M1 ACh ACh
H1H1 Neurokinin-1Neurokinin-1
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Diagram toDiagram to
summarisesummarise
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Antagonists Antagonists
5HT-35HT-3 DolasetronDolasetron,, GranisetronGranisetron,, TropisetronTropisetron,,
OndansetronOndansetron
D2D2
DroperidolDroperidol,, MetoclopramideMetoclopramide,, ProchlorperazineProchlorperazine
ACh ACh CyclizineCyclizine, Scopolamine, Scopolamine
H1H1
PromethazinePromethazine,, CyclizineCyclizine
Neurokinin-1Neurokinin-1
Aprepitant Aprepitant
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Agonists Agonists
SteroidsSteroids
DexamethasoneDexamethasone
BenzodiazepinesBenzodiazepines MidazolamMidazolam
CannabinoidsCannabinoids
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Managementanagement
Prevention is the aimPrevention is the aim
As a general rule the relative indication As a general rule the relative indicationfor prophylaxis increases as the number for prophylaxis increases as the number
of risk factors increasesof risk factors increases
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5HT-3 Antagonists5HT-3 Antagonists
NNT = 5NNT = 5 Timing?Timing?
At the end of At the end of surgeysurgey
DolasetronDolasetron Dose?Dose?
12.5mg is sufficient12.5mg is sufficient
Which one?Which one? DolasetronDolasetron 12.5 =12.5 = OndansetronOndansetron 4 =4 = TropisetronTropisetron 22
RamosetronRamosetron Longer acting- effective for up to 48 hoursLonger acting- effective for up to 48 hours
Side effectsSide effects
TramadolTramadol interaction?interaction?
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D2 AntagonistsD2 Antagonists
DroperidolDroperidol NNT = 4-6 when used alone for prevention of PONVNNT = 4-6 when used alone for prevention of PONV
Dose? 0.625-1.25mgDose? 0.625-1.25mg
Cheap and cost effectiveCheap and cost effective
Also good for PCA Also good for PCA opioidopioid-induced nausea/vomiting-induced nausea/vomiting
Main side effect: sedatingMain side effect: sedating
Black box warning: relevance?Black box warning: relevance?
MetoclopramideMetoclopramide Conflicting evidenceConflicting evidence
Numerous trials demonstrating that asNumerous trials demonstrating that as monotherapymonotherapy it is noit is no
better than placebobetter than placebo
Apparently effective in combination with Apparently effective in combination with dexamethasonedexamethasonewhen given in larger doseswhen given in larger doses
As effective as As effective as ondansetronondansetron or or droperidoldroperidol in combinationin combination
withwith dexamethasonedexamethasone??
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DexamethasoneDexamethasone
Timing is importantTiming is important
As effective as 5-HT3 antagonists and As effective as 5-HT3 antagonists and
droperidoldroperidol
NNT = 4NNT = 4
Mechanism of action: various theoriesMechanism of action: various theories
Central inhibition of PG synthesisCentral inhibition of PG synthesis Decreased turnover of 5-HT in the CNSDecreased turnover of 5-HT in the CNS
Most effective dose?Most effective dose?
Side effectsSide effects
Flushing,Flushing, perinealperineal itchingitching
One-off dose is not associated with adverseOne-off dose is not associated with adverseeventsevents
C li iC li i
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CyclizineCyclizine 50mg as good as the 5HT-3 antagonists50mg as good as the 5HT-3 antagonists
NNT = 4-5NNT = 4-5 Expensive, not readily available at RPHExpensive, not readily available at RPH
ScopolamineScopolamine TransdermalTransdermal patch 1.5mg placed 1hr pre-op aspatch 1.5mg placed 1hr pre-op as
good asgood as intraoperativeintraoperative 5HT-3 antagonists or 5HT-3 antagonists or DroperidolDroperidol
Dry mouth major side effectDry mouth major side effect Not available at RPH anywayNot available at RPH anyway
PromethazinePromethazine
Prevention or rescuePrevention or rescue Effective in doses as low as 6.25mg IVEffective in doses as low as 6.25mg IV
More effective in middle ear surgery?More effective in middle ear surgery?
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Neurokinin-1 Receptorseurokinin-1 Receptors
The final pathway?The final pathway?
Aprepitant Aprepitant
Highly selective NK-1 antagonist, givenHighly selective NK-1 antagonist, given
orallyorally Phase 3 trial recently completedPhase 3 trial recently completed
Better thanBetter than OndansetronOndansetron for up to 48 hours for for up to 48 hours for
vomitingvomiting Same nausea rates and rescue requirementsSame nausea rates and rescue requirements
Expensive and disappointing results!Expensive and disappointing results!
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Cochrane reviewCochrane review
Just as good asJust as good as
pharmacologicalpharmacological
agents in preventingagents in preventing
postoppostop vomitingvomiting
Even better inEven better in
preventingpreventing postoppostop
nauseanausea
NNT = 5NNT = 5
P6 acupuncture point6 acupuncture point
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Acupressurecupressure
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Summary..ummary..
New thoughts..ew thoughts..
Numerous trials confirming combinationNumerous trials confirming combinationtherapy is more effectivetherapy is more effective
CombinationCombination antiemeticsantiemetics need to have differentneed to have different
sites of actionsites of action
MetoclopramideMetoclopramide might be usefulmight be useful
intraoperativelyintraoperatively in combination within combination withdexamethasonedexamethasone (20mg + 8mg)(20mg + 8mg)
Acupuncture works! Acupuncture works!