Antiemetics Flashcards
Define nausea.
subjective feeling of the need to vomit; unpleasant; sometimes emesis isn’t preceded by nausea
Define vomiting.
involves contractions of the ileum and jejunum which move their contents back towards the stomach, the glottis closes to protect the airway, and the diaphragm contracts, the pharyngeal sphincters relax, the abdominal muscles contract which creates increased intraabdominal pressure that compresses the stomach; with open upper esophageal sphincters, emesis occurs
Define retching.
occurs when the same process happens, but the stomach is empty, no stomach contents are expelled
Define regurgitation.
Esophageal sphincters are not completely closed allowing stomach contents to pass into esophagus in setting of elevated abdominal pressure, no forceful expelling of stomach contents (no vomiting)
What is an example of regurgitation?
excessive mask ventilation
What is vomiting center?
controls vomiting & retching; located within the nucleus of tractus solitarius & parts of reticular formation in medulla oblongata
What are neurotransmitters that are involved in the vomiting center?
Neurotransmitters that activate or inhibit vomiting center: acetylcholine, dopamine, histamine, substance P, & serotonin
Review vomiting center components.
What is the Chemoreceptor Trigger Zone (CTZ?
located in the area postrema on the floor of 4th ventricle in the brain, lies outside the blood-brain barrier
What can the Chemoreceptor Trigger Zone (CTZ) detect?
CTZ can detect agents & relay signals to the vomiting center where the mechanical act of vomiting is stimulated
Where does the vomiting center send impulses?
Mechanical act of vomiting activated by vomiting center
When activated, vomiting center sends impulses (efferent signals) via CN V, VII IX, X, & XII; transmits efferent signals from the vomiting center to motor fibers GI & spinal nerves to diaphragm & abdomen to elicit vomiting
What are other ways to activate the vomiting center?
can also be activated by vestibular apparatus, thalamus, cerebral cortex, & neurons within GI tract
What is the definition of Postoperative Nausea and Vomiting (PONV)?
Defined as having nausea or emesis within 24 hours of a surgical procedure
Along with pain, _______ is a major issue that contributes to patient satisfaction
PONV
What is the occurance of PONV?
Can occur up to 40% of patients untreated, 80% for high-risk patients
What are antiemetics targets of?
Numerous neurotransmitters and receptor sites serve as a target for antiemetic medications
What are patient risk factors for PONV?
- Women
- Nonsmokers
- Hx PONV
- Hx of motion sickness
What are surgical risk factors for PONV?
- Surgery > 1 hr
- GYN, laparotomy/laparoscopy, ENT, breast, plastics, orthopedics
- Peds: incidence starting at age 3 - herniorrhaphy, T&A, strabismus, male genitalia
What are anesthetia risk factors for PONV?
- Inhaled anesthetics
- Nitrous oxide
- Neostigmine
- Opioids
What are the properties of PONV?
- Prevention easier than treatment
Use __________ for prevention and treatment PONV
multimodal approach (multiple drugs targeting multiple receptor sites)
Review components of the multimodal aprroach to PONV prevention and treatment.
What is the anticholinergic used for PONV?
Scopolamine
What is the drug class of Scopolamine?
Anticholinergic (antimuscarinic): tertiary amine (crosses the blood brain barrier)
What is the formulary for Scopolamine?
Antiemetic - transdermal patch
What is the use of Scopolamine?
Used as antiemetic for motion sickness & PONV prophylaxis
What is the MOA of Scopolamine?
Exerts antiemetic action by blocking muscarinic acetylcholine receptors within the vestibular system near the CTZ
What is the administration of Scopolamine?
- Apply 1 patch at least 4hrs before noxious stimulus (remove after 72hrs)
- Apply to dry postauricular area
What is the half life of Scopolamine?
Long half-life: 4.5 hr
What is the amount of Scopolamine delivered by the patch?
1.3 mg delivers about 5mcg/hr
What is the main side effect of Scopolamine?
visual disturbances (anisocoria)- wash hands after handling; dry mouth
When should Scopolamine be used cautiously?
Caution with glaucoma, seizures, psychosis, people over 65, not studied on peds
When is Scopolamine not approved?
Not approved for anyone younger than 18 y/o
What are causes of Central Anticholinergic Syndrome?
Can result from atropine and scopolamine (not glycopyrrolate, doesn’t cross blood-brain barrier)
What are the s/s of Central Anticholinergic Syndrome?
restlessness, hallucinations, somnolence, unconsciousness
What is a mnemonic for Central Anticholinergic Syndrome?
“atropine fever”
Anticholinergic med overdose: “Blind as a bat, Mad as a hatter, Red as a beet, Dry as a bone, Hot as hell, Full as a flask”
What is true about small children and Central Anticholinergic Syndrome?
small children can develop w/therapeutic dose of anticholinergic drug
What is the treatment for Central Anticholinergic Syndrome?
physostigmine (lipid soluble tertiary amine) 15-60 mcg/kg IV
What is the MOA of Physostigmine?
an anticholinesterase (acetylcholinesterase inhibitor) which increases ACh levels (within CNS) to compete with anticholinergic drugs such as atropine or scopolamine within the CNS
Why are Edrophonium, neostigmine, pyridostigmine not effective against Central Anticholinergic Syndrome?
not effective d/t quaternary ammonium structure & not able to enter the CNS
What is the repeat does of Central Anticholinergic Syndrome?
Repeat every 1-2 hours
What can Central Anticholinergic Syndrome be mistaken for?
This syndrome can be mistaken for delayed recovery from anesthesia and postop delirium