PONV (Exam III) Flashcards
When does nausea peak in patients post-operatively?
How long does nausea/vomiting typically last post operatively?
Peak: 6 hours
Persists for 24 - 48 hours
What are the four major inherent (patient-specific) risk factors for PONV?
- Female
- Non-smoker
- PONV history
- History of motion sickness
Opioid use not an inherent risk factor.
What factor is the greatest cause of PONV?
Intraoperative and postoperative opioids.
What is the full list of anesthetic-technique risk factors for PONV?
- VAA’s
- Nitrous > 50%
- Opioids
- Neostigmine
- Gastric distention
- Anesthesia duration
- Forced PO fluids prior to discharge
What surgeries place a patient at higher risk for development of PONV?
- ENT surgeries
- Neuro surgeries
- Belly surgeries
- Breast, plastic, strabismus surgery (girly sx’s)
- Long surgeries
Pediatric PONV incidence increases with age until _______.
puberty
Which pediatric procedures are noted to have a higher incidence of PONV?
- Adenotonsillectomy
- Strabismus repair
- Hernia repair
- Orchiopexy
- Penile surgeries
Will increased O₂ concentrations increase or decrease PONV occurrence?
decrease
Will adequate hydration increase or decrease PONV occurrence?
decrease
Will nitrous use increase or decrease PONV occurrence?
increase
Will neuromuscular blockade reversal with acetylcholinesterase inhibitors increase or decrease PONV occurrence?
Increase
↑ neostigmine = ↑ PONV
Will minimized motion/ambulation increase or decrease PONV occurrence?
decrease
Let patient guide movement based on how they feel.
Where is the emetic center of the brain located?
Lateral reticular formation of the brainstem
Which substances act directly on receptors of the lateral reticular formation of the brainstem?
Trick Question. No substances act directly on the emetic center.
Where does afferent input arrive from to the emetic center?
- Pharynx
- GI tract
- Mediastinum
- Afferent nerves of CTZ and 8th CN
Where does CNS afferent input to the emetic zone come from?
- Chemotactic Zone (CTZ) of the area postrema
- Vestibular portion of Vestibulocochlear nerve (CN VIII)
The CTZ of the area postrema does not have the ______.
What are the implications of this?
Blood brain barrier (BBB)
No BBB means chemicals and drugs in the blood or CSF can trigger N/V.
What receptors are located in the Chemoreceptor Trigger Zone?
- Dopamine
- Serotonin 5-HT3
- Opioid
- Histamine
- Muscarinic
- Neurokinin-1
- Cannabinoid
What drug is the gold standard for PONV prophylaxis and treatment?
Trick question. No single drug is gold standard.
Patients (should / should not) receive the same drug for prophylaxis and treatment of PONV.
Should not.
Ex. If ondansetron is used for prophylaxis, use promethazine for treatment
When it comes to anti-emetics more is _______ (better, or worse.)
Better
Opioid premedication will ______ risk of PONV.
Benzodiazepine premedication may ______ risk of PONV.
Increase
Decrease
What induction drug(s) increase risk of PONV?
- VAA’s
- Etomidate
- Ketamine
What induction drug(s) decrease risk of PONV?
Propofol
What volatile agent is associated with PONV (especially in concentrations greater than 50%)?
Nitrous Oxide
One single dose of an opioid is not enough to cause PONV. T/F?
False. A single dose can cause PONV.
Greater than ____mg of Neostigmine is associated with increased PONV risk.
> 2.5mg
Dose dependent: ↑ neostigmine = ↑ PONV.
What drug could reduce the PONV associated with neostigmine?
Atropine
What is the mechanism of action of PONV induced by neostigmine?
Though to be muscarinic actions on the GI tract
At how many risk factors is PONV prophylaxis indicated?
What is P-6 stimulation?
Radial compression
How is P-6 manipulation thought to treat PONV?
P-6 compression → Hypophyseal secretion of β-endorphins → inhibition of CTZ.
Is P-6 manipulation good at treating nausea and vomiting?
No really, better at inhibition.
What are the subtypes of anti-dopaminergics that are used to treat PONV?
- Butyrophenones
- Phenothiazines
What are the side effects of dopamine receptor antagonists?
- Drowsiness/sedation
- Extrapyramidal s/s
What drugs are butyrophenones?
Haloperidol
Droperidol
What black box warning exists for Droperidol?
Torsades de Pointes and sudden death.
More than ______mg of droperidol should never be given.
0.625mg
Droperidol is as effective as ___________ for treatment of PONV.
Ondansetron 4mg
Droperidol also has effects as a ______________ thus resulting in hypotension.
weak α blocker
What drugs are phenothiazines?
Prochlorperazine
Chlorpromazine
Promethazine
What black box warnings are there for promethazine?
- Tissue damage
- Resp arrest for < 2yo’s
What receptors does promethazine act on?
- Anti-dopamine
- Anti-histamine
- α adrenergic
- muscarinic
What are known side effects of promethazine?
- Sedation
- Hypotension
- EPS
How do 5HT3 Antagonists work in the treatment of nausea/vomiting?
Antagonize serotonin receptors on the vagal nerve and CTZ
Chronic use of 5HT3 antagonists can result in mild elevation of what?
Liver enzymes
When should ondansetron be given?
4mg within 15 - 20 min of surgery end.
What anticholinergic is given for PONV prophylaxis?
What dose and route is utilized?
Scopolamine 1.5mg transdermal patch
What is the PONV rescue dose of dexamethasone?
Trick question. Dexamethasone should be used for prophylaxis only.
When is dexamethasone given and what dosage is utilized?
Given during or immediately after induction. 4mg (just as effective as 8mg)
How does metoclopramide combat PONV?
Increases LES tone and GI motility.
Not very efficacious. 10 - 20mg IV
What NK-1 antagonist is given for PONV? How does it work?
Aprepitant:
- antagonizes substance P in the emetic center.
- Depresses NTS activity
- Blocks afferent messages from enterochromaffin cells
What is the aprepitant dose?
40mg or 125mg
How does propofol prevent/treat PONV?
Blocks serotonin release in subhypnotic doses.
May also inhibit CTR.
What is the subhypnotic dose of propofol?
16.7 mcg/kg/min
What drug needs to be given alongside propofol?
Glycopyrrolate (to counteract bradycardia)
______ ______ has been associated with a 50% reduction in nausea.
Isopropyl alcohol