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Pharm > PONV/GI > Flashcards

PONV/GI Flashcards

1
Q

How is “early” PONV defined?

A

occurs within the first 6 hours of surgery

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2
Q

How is “late” PONV defined?

A

occurs 6-24 hours after surgery

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3
Q

What is the incidence of PONV?

A

40% in general anesthesia
80% in high risk population

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4
Q

What patient factors put someone at risk for PONV?

A

female
non-smoker
hx of motion sickness
previous incidence of PONV

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5
Q

What surgical factors put a patient at risk for PONV?

A

long procedure
laparotomies, gyn sx, laparoscopic, ENT, breast, ortho

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6
Q

What anesthesia factors put a patient at risk for PONV?

A

inhalational agents
N2O
neostigmine
narcotics
etomidate

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7
Q

Where is the vomiting center located?

A

medulla oblongata

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8
Q

What are the 4 areas that trigger N/V?

A

chemoreceptor trigger zone
vestibular apparatus
thalamus & cerebral cortex
neurons in the GI tract

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9
Q

Describe the pathway of N/V

A

efferent signal travels via cranial nerves through vagal sympathetic fibers and parasympathetic chains that trigger a motor process to occur (emesis)

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10
Q

List the NT associated with PONV

A

dopamine
serotonin
acetylcholine
histamine
substance P

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11
Q

What receptors/NT play a role in PONV in the vestibular system?

A

H1 receptor (histamine)
M1 receptor (ACh)

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12
Q

What receptors/NT play a role in PONV in the CTZ?

A

chemoreceptors
D2 receptors (dopamine)
NK receptors (Substance P)
5-HT3 receptors (serotonin)

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13
Q

What receptors/NT play a role in PONV in the vomiting center?

A

H1 (histamine)
M1 (ACh)
NK (Substance P)
5-HT3 (serotonin)

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14
Q

What receptors/NT play a role in PONV in the GI tract?

A

mechanoreceptors (stretch)
chemoreceptors
5-HT3 (serotonin)
H1 (histamine)
NK (substance P)
M1 (ACh)

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15
Q

List the anticholinergics used to treat PONV

A

atropine
hyoscine
scopolamine

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16
Q

List the benzamides used to treat PONV

A

metoclopramide (Reglan)

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17
Q

List the benzos used to treat PONV

A

midazolam

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18
Q

List the butrophenones used to PONV

A

droperidol
haloperidol

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19
Q

List the cannabinoids used to treat PONV

A

dronabinol
nabilone

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20
Q

List the glucocorticoids used to treat PONV

A

dexamethasone

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21
Q

List the 5-HT3 antagonists used to treat PONV

A

dolasetron
granisetron
ondansetron
palonosetron
ramosetron
tropisetron

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22
Q

List the neurokinin-1 antagonists used to treat PONV

A

aprepitant
fosprepitant

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23
Q

List the phenothiazines used to treat PONV

A

prochoperazine
promethazine
chlorpromazine

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24
Q

How does scopolamine work to combat PONV?

A

-blocks transmission of impulses from vestibular apparatus to medulla

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25
Q

What is the dose of scopolamine for PONV and how is it delivered?

A

5mcg/hr x 72 hours
best if given at least 4 hours before stimulus
transdermal delivery allows for slow and sustained dosing and prevents anticholinergic side effects

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26
Q

List the common uses for scopolamine

A

motion sickness
middle ear surgery
N/V with PCA or epidural morphine

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27
Q

Describe the MOA of metoclopramide for PONV

A

stimulates the GI tract via cholinergic and anti-dopaminergic effects

-contracts lower esophageal sphincter & gastric fundus
-increases gastric and small intestine motility
-decreased muscle activity in pylorus & duodenum w/ stomach contraction

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28
Q

What populations should metoclopramide be cautiously used in and why?

A

Parkinson’s
RLS

d/t anti-dopaminergic effects

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29
Q

What is the MOA of midazolam for PONV?

A

decrease synthesis & release of dopamine within the CTZ

30
Q

When should midazolam be given for PONV?

A

at the end of the case

31
Q

What is the MOA of droperidol for PONV?

A

competitive dopamine antagonist @ D2 receptor (blocks dopamine and GABA)

32
Q

What is the dose of droperidol given for PONV?

A

0.625mg-1.25mg prophylactically

33
Q

In which populations should droperidol be cautiously used?

A

Parkinson’s
RLS
potential for prolonged QTc (high doses)

34
Q

What is the MOA of dexamethasone for PONV?

A

inhibits prostaglandin synthesis and controls endorphin release

35
Q

What is the typical dose of dexamethasone given for PONV?

A

4mg

36
Q

In what patient populations should dexamthasone be cautiously used?

A

obese
DM (increased r/f hyperglycemia)

37
Q

What type of receptor is the 5-HT3 receptor? What NT acts on it?

A

ligand-gated (Na+ and K+) cation channel
depolarizes the plasma membrane
excitatory
acted on by serotonin

38
Q

Besides nausea, what other effects does serotonin have on the body?

A

addiction
aggression
vasoconstriction
increased intestinal motility
learning and memory consolidation

39
Q

Why are 5HT-3 antagonists not useful for motion sickness or vestibular stimulation?

A

no 5HT-3 receptors located in those areas

40
Q

What is the typical dose of ondansetron?

A

4mg, onset 30-60min

41
Q

What are some side effects of ondansetron?

A

headache (major)
diarrhea
QTc prolongation

42
Q

Which 5HT-3 antagonist has an active metabolite?

A

dolasetron

43
Q

What is the typical dose of granisetron? How often is it dosed?

A

0.1mg
lasts 24 hours

44
Q

Which 5HT-3 antagonist is used to treat symptoms with carcinoid syndrome?

A

tropisetron

45
Q

Describe Substance P

A

primary NT produced by pain & temp afferent peripheral neurons

46
Q

What receptors does substance P act on and where are they located?

A

neurokinin (NK1, NK2, NK3)
located in gut and nausea pathways

47
Q

What is the MOA of aprepitant? What is the most common type of NV that it is used for?

A

competitive antagonist at NK1 receptors, inhibits substance P from binding

used in chemotherapy-induced NV

48
Q

What is a noteworthy side effect of aprepitant?

A

inhibition of steroidal contraceptives x 7-10 days

49
Q

What is the MOA of phenothiazines? Give some examples

A

antagonize H1 and M1 receptors, preventing histamine and ACh from binding

E.g. promethazine, procholoperazine, chlorpromazine

50
Q

Histamine is synthesized from what substance?

A

histadine

in the CNS, immune cells, and GI tract

51
Q

Where are histamine receptors located?

A

H1: vascular smooth muscle, bronchial smooth muscle, CNS
H2: stomach
H3: presynaptic cleft

52
Q

List examples of H1 receptor antagonists

A

diphenhydramine (Benadryl)
hydroxyzine (Atarax, Vistaril)
phenergan
meclizine

53
Q

What is the typical dosage/onset/duration of diphenhydramine?

A

dose: 25-50mg IV
onset: 3 min (or less)
duration: 1-7hrs

54
Q

Describe dimenhydrinate

A

aka dramamine
antagonizes H1 and M1 receptors
used for motion sickness & sleep aid

55
Q

What are some side effects of H1 receptor antagonists that are unrelated to the H1 blockade?

A

sedation
anti-nausea/anti-emetic
adrenoceptor blocking (esp Phenergan which may cause orthostatic hypotension)

56
Q

What two methods are used to prevent aspiration?

A

antacids (increase gastric pH)
prokinetics (decrease gastric fluid volume)

57
Q

Is aspiration more or less common in pediatric patients?

A

more common (r/t use of inhaled anesthetics for induction??)

58
Q

Which patient populations present with a higher r/f aspiration?

A

pregnant
diabetic
mask induction
emergent case

59
Q

What is the most common oral antacid given in anesthesia?

A

Bicitra
15-30mL given right before induction
used in C-sections
tastes awful

60
Q

List the four H2 drugs currently available

A

cimetidine
ranitidine
famotidine
nizatidine

61
Q

What is the MOA of H2 blockers?

A

selective, reversible competition with histamine at H2 sites

62
Q

What are the clinical uses for H2 receptor antagonists?

A

peptic duodenal ulcer
gastric ulcer
erosive esophagitis
hypersecretory conditions

63
Q

What are the s/s of H2 receptor antagonist toxicity?

A

CNS dysfunction (slurred speech, delirium, confusion)
liver toxicity
(mostly with cimetidine)

64
Q

H2 receptor antagonists interact with which drugs?

A

inhibits the cytochrome P450 system
(esp warfarin, dilantin, propranolol, metoprolol, labetalol, diazepam, CCBs)

65
Q

List some commonly used PPIs

A

omeprazole
pantoprazole
esomerprazole
lansoprazole

66
Q

What effect do PPIs have on the body?

A

increase gastric fluid pH
decrease gastric fluid volume
*must be metabolized
*can take days for effect
*crosses BBB (HA, agitation, confusion)

67
Q

Which drug is used to treat Zollinger-Ellison syndrome?

A

omeprazole

68
Q

What do GI prokinetics do? List 2 examples

A

increase LES sphincter tone, enhance peristaltic contractions, accelerate the rate of gastric emptying

E.g. metoclopramide, domperidone

69
Q

What is the MOA of metoclopramide in the GI system?

A

involves cholinergic stimulation and dopamine antagonism
-contract LES and gastric fundus (prevents reflux)
-increase gastric emptying
-decrease pylorus and duodenum muscle activity
-crosses BBB and affects CTZ

70
Q

What is the typical dose of metoclopramide?

A

10-30mg over 3-5 mins

71
Q

What effect does metoclopramide have on gastric pH?

A

no effect

72
Q

What are some side effects of metoclopramide?

A

crosses the placenta
abdominal cramping if given fast
extrapyramidal reactions (d/t dopaminergic effects)
prolongs succs metabolism

Pharm (19 decks)

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