Antiemetics - Dr. C PowerPoint Flashcards
What is the leading cause of unanticipated hospital admission following outpatient surgery?
PONV and its complications
Without prophylaxis, nausea occurs in what percent of patients who receive general anesthesia? Can be as high as ____% in high risk patients.
40%
As high as 80%.
A patient who experiences nausea or who vomits within how many hours of a surgical procedure that required anesthesia meets the criteria for PONV diagnosis
24 hours - anything within 24 hours falls under anesthesia
Early PONV is NV within?
6 hours
Late PONV is NV between?
6-24 hours
PONV can be associated with morbidity due to:
Dehydration, electrolyte abnormalities, wound dehiscence from retching, bleeding, esophageal rupture, airway compromise such as aspiration
Is emesis always proceeded by nausea?
No
The sequence of events that occur during emesis is controlled by? Which lies in the?
Vomiting center in the medulla oblongata
A number of neurotransmitters modulate the activity of the vomiting center what are some of these?
*Serotonin, *dopamine, substance P, ACh, GABA, and cannabinoids
Slightly superior or cephalad to the vomiting center is the chemoreceptor trigger zone (CTZ), also known as? This area, detects what in the bloodstream?
Area postrema, detects noxious chemicals in the bloodstream
Is the chemoreceptor trigger zone within or outside the blood-brain barrier?
Outside the blood-brain barrier, allowing it to sample more chemical chemicals in the blood
A number of transmitters modulate the activity of the vomiting center name them
Serotonin, Dopamine, Substance P GABA, Cannabinoids
Patient risk factors that increase risk of PONV
women, nonsmokers, hx of motion sickness, previous episodes of PONV
Surgical factors that increase risk of PONV
Long surgical procedures, gynecology, laparoscopic, ENT, breast surgery, plastic surgery, orthopedic surgery
Anesthetic factors that increase risk of PONV
Use of inhalational anesthetics, including nitrous, neostigmine and opioids
What are the current anti-emetic drug classes?
Corticosteroids
Phenothiazines - (compazine)
Butyrophenes -(droperidol, haloperidol)
Benzamides - (reglan)
Anticholinergics
Antihistamines
5-HT3 Antagonists
NK-1 Antagonists
Benzodiazepines
Scopolamine works best a preventing what kind of Nausea and Vomiting
Prevention of motion-induced NV
How long is one patch of scopolamine good for
24-72 hours
What is the most reported side effect of scopolamine
drying of secretions / dry mouth
Due to its anti-dopaminergic activity metoclopramide should be used with caution, if at all in patients with?
Parkinson’s disease, restless, leg syndrome, movement disorders related to dopamine, inhibition, and depression
What is akathisia?
Can occur after administration of reglan- feeling of unease and restlessness in lower
extremities can occur following IV administration
Adult dose of Reglan
10-20mg IV
What is the MOA of metoclopramide (reglan)
Week antiemetic, stimulates the GI tract via cholinergic mechanisms that result in features gastric and small intestinal.
If using Midazolam for antiemetic effects - when should it be administered during a case?
Should be administered IV towards the end of the case by infusion in intubated and vented patients in the ICU
What is believed to be the MOA of midazolam’s antiemetic effects?
Believed to decrease dopamine’s emetic effect and decrease the release of serotonin
What are three antiemetic drugs in the Butyrophenones class?
Droperidol and Haloperidol
Barhemsys (Amisulpride)
What is the PONV dose for droperidol
0.625-1.25mg
What is the PONV dose for haloperidol
0.5-2mg
Is droperidol less, the same, or more effective than decadron or zofran?
As effective as both decadron and zofran preventing PONV
If using droperidol, when should it be given during the case?
Give at the beginning of the case or as a rescue drug in PACU when all else hasn’t worked
What population should butyrophenones (droperidol and haloperidol) be used with caution in?
Patients with Parkinson’s, restless leg syndrome, or other diseases related to dopaminergic activity. It can cause extrapyramidal symptoms.
What is the black box warning for droperidol?
Can prolong QT interval in doses higher than the PONV prophylaxis doses.
What is Barhemsys (Amisulpride) MOA?
Selective D2 and D3 receptor antagonist
What is Barhemsys (Amisulpride) used for?
approved as a rescue agent for PONV
What is the dose of Barhemsys (Amisulpride) ?
recommended dose 5-10mg
What patients should you avoid using Barhemsys (Amisulpride) ?
Patients with congenital long QT syndrome
Is Barhemsys (Amisulpride) sedating?
advertised as non-sedating
Is droperidol sedating?
yes
Dose for decadron PONV
4-8mg IV
Which pts are at risk for increased perioperative hyperglycemia with a single dose of decadron
Obese and diabetic
what dose of droperidol has similar effectiveness as zofran or decadron
1.25mg
5-HT3 receptor antagonists can each cause what ecg change
slight prolongation of QTc interval
What is the brand name for Dimenhydrinate
Dramamine
What is Dimenhydrinate (Dramamine) effective at preventing?
Preventing PONV as well as motion sickness
What is the PONV dose of Dimenhydrinate (Dramamine) ?
20mg IV
In children, Dimenhydrinate (Dramamine) at what dose can significantly decrease the incidence of vomiting after strabismus surgery
0.5mg/kg IV
What is one Neurokinin 1 Receptor Antagonist that can be used for PONV prophylaxis? What dose and when should you give it?
Emend
40mg PO before surgery
What is the MOA of Emend?
Substance P and NK-1 receptor antagonists
What is believed to be the mechanism behind neurokinin 1 receptor antagonism related to PONV
It is believed to provide antiemetic activity by suppressing their activity at the nucleus of the solitary tract (NST), where vagal afferents from the GI tract converge with inputs from the area postrema (aka chemoreceptor trigger zone) and other regions of that brain that initiate emesis
One patch of scopolamine contains how much medication
1.5mg
Normal dose of Prochlorperazine (Compazine) for adults
10mg IV
Aspiration during GA occurs in ~ 1/? adults and 1/? children
1/8500 adults
1/4400 children
What are two situations with an increased risk for aspiration
emergency operations due to full stomachs
Bowel obstructions
Drugs that increase the pH of gastric contents are called
antacids
Drugs that decrease the volume of gastric contents are called
prokinetics
How do oral antacids work
Neutralize (remove) hydrogen ions from gastric contents or decrease secretion of hydrogen chloride into the stomach
What is the nonparticulate (clear) antacid? What population receives it the most
Sodium Citrate - used in OB
What is the benefit of a nonparticulate (clear) antacid?
They are less likely to cause a foreign body reaction if aspirated, and their mixing in gastric fluid is more complete than particulate antacids
What is the dose of sodium citrate? When should it be given?
15-30mL and admin 15-30min before induction of anesthesia
What are some complications of Antacid Therapy
Bacterial overgrowth in small intestine
UTI
Urolithiasis
Altered Renal Elimination (reflects increased urinary ph)
Acid rebound (unique to calcium-containing antacids)
Hypophosphatemia
Milk-Alkali Syndrome (hypercalcemia, systemic alkalosis)
Drug interactions
How do Macrolides work in the GI System
increases lower esophageal
sphincter tone, enhances intraduodenal coordination, and
promotes emptying of gastric liquids.
prokinetic properties
What are the most effective drugs available for controlling gastric acidity and volume?
Proton Pump Inhibitors
What is the MOA of PPIs?
Histamine induces what within the body
Contraction of smooth muscles in the airways
Increases the secretion of acid in the stomach
Stimulates release of neurotransmitters in the CNS
How do Histamine Receptor Antagonists work
bind to receptors on effector cell membranes, to the exclusion of agonist molecules, without themselves activating the receptor (histamine receptor antagonists do not inhibit release of histamine)
How are H1 receptor antagonists characterized? What are the differences?
First Generation: Tend to produce sedation
Second Generation: Relatively nonsedating
How fast do H1 receptor antagonists take to reach peak plasma concentrations
Within 2 hours
What are the clinical uses of H1 Receptor Antagonists
-Prevent and relieve symptoms of allergic rhinitis.
-Used to treat acute anaphylactic rxns
-Diphenhydramine used as a sedative, antipruritic, and antiemetic
What CNS effects are associated with H1 Receptor Antagonists?
Somnolence
Diminished Alertness
Slowed Reaction Time
Impairment of cognitive fxn
What are some possible cardiac side effects of H1 receptor antagonists?
Tachycardia, prolong QTc, heart block, arrythmias
MOA of H2 Receptor Antagonists
Produce selective and reversible inhibition of H2 receptor-mediated secretion of hydrogen ions by parietal cells
What are some H2 blockers
Cimetidine
Famotidine
Cimetidine clearance decreases _____% between the ages of 20 and 70 years old
75%
What are the nonspecific Anti Histamine Agents
Nonspecific antihistamines, likely acting on H1 receptors, including diphenhydramine,
dimenhydrinate, and promethazine
What is the MOA of H2 Blockers
H2-receptor antagonists competitively and selectively inhibit the binding of histamine to H2 receptors, thereby decreasing the intracellular concentrations of cAMP and
the subsequent secretion of hydrogen ions by the parietal cells
How long before induction of anesthesia should omeprazole be administered
> 3 hours before induction
What is the usual dose of omeprazole? How long until onset effects occur?
20mg PO
Occurs within 2-6 hours
How does omeprazole reduce aspiration risks
effectively increases gastric fluid pH and decreases gastric fluid volume
What is the only drug approved by the FDA for the tx of diabetic gastroparesis
Metoclopramide
IV admin of Reglan may be associated with
hypotension
tachycardia
bradycardia
cardiac dysrhythmias
Who should not receive GI prokinetic drugs
A patient with a suspected or known mechanical obstruction to gastric emptying
