When does PONV peak?
6 hours after surgery and lasts 24-48 hours
What do we do as anesthetists that increases the risk of PONV?
VAs
N2O
opioids
neostigmine
gastric distention
duration of anesthesia
mandatory PO fluids before DC
Which adult surgeries have the highest incidence of PONV?
laparoscopy
laparotomy
neurosurgery
ENT surgery
Plastics
At what age does the risk increase for women to experience PONV?
adolescence
Which pediatric surgeries have the highest risk of PONV?
Adenotonsillectomy
Strabismus repair
hernia repair
orchiopexy (for undescended testicles)
penile surgery
List a few anesthesia strategies that reduce the risk of PONV…
regional anesthesia
TIVA c Propofol
adequate hydration
adequate oxygenation
avoid nitrous
avoid VAs
minimize opioids
minimize neostigmine
What are the concerns we have in regards to PONV?
patient discomfort
tension on suture lines
wound dehiscence
aspiration
dehydration and electrolyte imbalance
increased ICP and IOP
prolonged stay in PACU
Where is the emetic center in the brain?
in the lateral reticular formation of the brainstem
What do anti-emetic drugs target?
receptors of areas that send afferent signals to the reticular formation
What are some afferent inputs to the lateral reticular formation?
pharynx
GI tract
mediastinum
chemoreceptor trigger zone in the area postrema
vestibular portion of CN8
What receptors are found in the chemoreceptor trigger zone?
dopamine
serotonin
opioid
histmaine
muscarinic
neurokinin-1
cannabinoid
What do we know about preventing PONV?
no “gold standard drug”
targeting multiple different receptors is more effective
preventing is more effective than treating
Which anesthesia drugs decrease likelihood of PONV?
benzodiazepines
propofol
What drug is best to give with neostigmine for NMBD reversal to reduce risk of PONV?
Atropine
What are the recommended PONV drugs from low risk to high risk?
low risk: 5HT3 antagonist
moderate risk: 5HT3 antagonist + steroid
high risk: 5HT3 antagonist + steroid + TIVA
What are the rescue drugs used for PONV?
5HT3 antagonists
phenothiazine (promethazine/Phenergan)
antihistamine
metoclopramide
What receptor do phenothiazines target? What are some common side effects?
Dopamine receptors
S/E: drowsiness, sedation, extrapyramidal sx
What class of drug is Droperidol? What receptor does it target? It is as effective as______ and more effective when given with______.
Why don’t we give it?
Butyrophenone
targets DA receptors
as effective as 4mg Ondansetron and more effective when given with 10mg of metoclopramide
Black Box warning: torsades and sudden death
What is the typical dose of promethazine in adults? What is the black box warning associated with it?
12.5-25mg
BBW: tissue damage and respiratory arrest in children <2 y/o
What dose do we give of Ondansetron? Dexamethasone?
4mg of each (studies show 8mg of each is not more effective)
When is Dexamethasone given?
Just after induction
When is ondansetron given?
within 15-20 minutes of end of surgery
How does Reglan work? What are some side effects?
It increases LES tone and GI motility
S/E: restlessness, extrapyramidal sx
What is an example of an NK-1 antiemetic and how does it work?
Aprepitant, it works by antagonizing substance P in the emetic center and interferes with afferent messages from enterochromaffin cells
