Antiemetics Flashcards
What are the 3 mechanisms of Glucocorticoids?
- Anti-inflammatory effects
- Direct central action at the solitary tract nucleus
- Interaction with the neurotransmitter serotonin, receptor proteins tachykinin (NK-1 & NK-2, alpha-adrenaline, prostaglandins)
Where does 1/3 of aspiration occur
1/3 occurs during laryngoscopy & intubation
1/3 occurs during the procedure
1/3 occurs during extubation
What is the volume that determines aspiration pneumonitis
15 - 25 mLs
What is the #1 thing patients complain about after surgery?
- emesis
- gagging on the ETT during extubation
- pain
- intraoperative recall
True or False: if your patient experiences nausea or has emesis within 24 hrs of a surgical procedure that required anesthesia, your patient was considered “under anesthesia”
True
What is the most important complaint following surgery & the leading cause of unanticipated hospital admissions following outpatient surgery
PONV
- along with pain
Where is the vomiting center found?
Lies in the nucleus tractus solitarus within the medulla & parts of the reticular formation
The vomiting center receives sensory input from what three locations:
- Chemoreceptor trigger zone (CTZ)
- Vestibular apparatus
- GI tract
How does the CTZ receive noxious stimuli ?
It detects noxious chemical in the bloodstream because it is outside the BBB
Once the vomiting center is activated how is the signal transmitted?
Efferent signals travel via CN. V, VII, IX, X, & sometimes XII through the vagal parasympathetic fibers & sympathetic chain to skeletal m. through alpha motor neurons
True or False: Treating PONV is easier than preventing it.
False.
It is easier to prevent PONV than actually treating it.
- this is completely the anesthesia role
What are the most common patient risk factors for PONV?
- Female
- Non-smoker
- Hx of motion sickness
- Previous PONV
- Youth > elderly
What are 5 anesthetic risk factors for PONV?
- Halogenated agents
- N2O
- Opioids
- Etomidate
- Neostigmine
- Also the longer the procedure the > the risk
- Laparotomies, GYN, & Laparoscopic procedures
Why do women have an increased risk of PONV?
Progesterone & estrogen in the CTZ or on the vomiting center itself
- PONV varies within the menstrual cycle & is reduced after menopause
When should you give Decadron and why?
Give during induction once the patient is asleep b/c it will feel like their genitals are on fire
(even though the text says to give 1 hr prior to anesthesia)
When might you see an increase in blood glucose after giving decadron?
6-12 hrs post-op
When should you administer zofran?
Ondansetron 4mg should be given 30 minutes of the case finishing up
When is Zofran not effective?
Serotonin receptor antagonists are NOT effective in the treatment of motion-induced nausea & vomiting
What is the gold standard antiemetic?
(Ondansetron) Zofran
If you give the higher dose of Zofran what can happen?
QT prolongation & Torsades de pointes
If you combine Zofran with Decadron & Emend what will happen?
the efficacy increases
= Synergistic effect
Neurokinin-1 receptor antagonists
(Emend) Aprepitant
(Emend) Fosaprepitant = pro-drug
(Akynzeo) Netupitant
(Varubi) Rolapitant (P/NK-1 receptor antagonists)
- Work if your patient has a hx of emesis & motion sickness
What are the common side effects of scopolamine?
- Blurred vision
- Dizziness
- Dry mouth
What is the only drug used for gastroparesis?
(Metoclopramide) Regalan
- gastrointestinal prokinetic drug that increases lower esophageal sphincter tone & stimulates motility
Where does (Metoclopramide) Reglan work and what should you be cautious of?
Reglan is a Dopaminergic (D2) & serotonergic (5-HT3), peripheral 5-HT4 at higher doses antagonists that works in the area of postrema
- Contraindicated in Parkinson’s disease b/c of EPS &
patients with bowel obstruction - Patients with restless leg synd.
- patients with movement disorders related to dopamine inhibition or depletion
What are the most common EPS (extrapyramidal symptoms)
- Rigid muscles in the limbs
- Tremors
- Increased salivation
- Changes in one’s posture or gait
- 20-40% of pts taking antipsychotics develop Parkinsonian symptoms
If you give your patient Reglan and they become hypotensive & Tachycardic what do you want to give?
Phenylephrine
Droperidol has a black box warning for what?
association with QT prolongation
True or False: Droperidol is not as effective as Decadron or Zofran in preventing & treating PONV
False.
If there is no concern for your patient having dopamine antagonism Droperidol is just AS effective
What are the most commonly used H2 receptor antagonists and what are they used for?
Most commonly used:
- Cimetidine (Tagamet)
- Famotidine (Pepcid)
- Ranitidine (Zantac)
- Nizatidine (Axid)
All used for GERD
What is the most potent H2 receptor antagonist?
Famotidine is the most potent
- Cimetidine is the least potent
If you discontinue your H2 receptor antagonist with is a side effect to be expected?
Discontinuation lead to hyper-secretion of gastric acid
Oral antacids contain aluminum and this may interfere with what?
Interfere with the absorption of tetracyclines and poss. digoxin
What drug class is the most effective drugs at controlling gastric acidity & volume?
Proton pump inhibitors (PPI)
- Omeprazole, esomeprazole, lansoprazole, pantoprazole, rabeprazole
What is the mechanism behind gastric acid secretion and PPI Moa?
The final step in gastric acid secretion is the membrane enzyme proton pump that moves hydrogen ions across the gastric parietal cell membrane in exchange for POTASSIUM IONS**
PPI stops the pump for transporting
What is Aminophylline?
A bronchodilator
- relieves cough, wheezing, SOB, & trouble breathing by increasing the flow of air into the bronchial tubes
- works as a phosphodiesterase inhibitor (inhibits cAMP = bronchodilation)**
- it CONTROLS symptoms but does NOT CURE them**
Why is Aminophylline not used very often?
- Cannot take with caffeine, coffee, tea, chocolate
- NTI & has a ton of adverse side effects that increase 30-day mortality rates
Chronic treatment of asthma with a Beta 2 agonists can lead to what?
Tachyphylaxis
Ipratropium (Atrovent)
Inhaled antimuscarinic (short acting)
- related to Atropine
- given with an MDI (meterdosed inhaler) to promote bronchodilation w/o appreciable systemic anticholinergic effects
What is Doxapram
Respiratory agent that stimulates the CNS
- acts centrally & peripherally to augment breathing efforts (increase TV & increase MV)
Which agent primarily targets the chemoreceptor trigger zone?
a. Ondansetron
b. Scopolamine
c. Dexamethasone
d. Hydroxyzine
a. Ondansetron = 5-HT3 receptor antagonist
- treats PONV by antagonizing serotonin receptors in 2 places: CTZ (area of postrema) & peripheral receptors in the GI tract & vagus n.
A patient with Parkinson’s disease is scheduled for a mastoidectomy under general anesthesia. Select the MOST appropriate antiemetic drug classes to reduce the risk of postoperative nausea & vomiting (Select 2):
a. Anticholinergics
b. Phenothiazine
c. Neurokinin-1 antagonists
d. Butyrophenones
a. Anticholinergics
c. Neurokinin-1 antagonists
- Antidopaminergic drugs are contraindicated in patients w/ Parkinson’s they can exacerbate extrapyramidal effects. These drugs include:
- Metoclopramide
- Butyrophenones (Haloperidol & Droperidol)
- Phenothiazines (promethazine)
- Anticholinergics are very useful for patients undergoing middle ear surgery
