Antiemetic, Antihistimine, and Aspiration Prevention

Question 1

Risk factors for postoperative nausea and vomiting in adults

Answer 1

Patient specific:
Female gender
Nonsmoking status
History of PONV/motion sickness

Anesthetic risk factors:
Use of volatile agents
Nitrous oxide use
Use of intraoperative and postoperative opioids

Surgical risk factors:
Duration of surgery (every 30min increase in duration increases PONV 60% of baseline)
Type of surgery (laparoscopy, laparotomy, breast, stabismus, plastic surgery, maxillofacial, gynecological, abdominal, neurologic, opthalmologic, urologic)

Question 2

Simplified PONV risk score for adults

Answer 2

Question 3

Simplified POV risk score for children

Answer 3

Question 4

What are strategies to reduce baseline risk of PONV

Answer 4

Question 5

Antiemetic timing and dosing for prevention of PONV in adults

Answer 5

Question 6

Algorithm for management of PONV

Answer 6

Question 7

Stimulation of H1 receptors leads to what?

Answer 7

Contraction of intestinal smooth muscle

Question 8

Contraction of H2 receptors leads to what?

Answer 8

Increases gastric acid (HCl) secretion from parietal cells

Question 9

H2 blockers are used to treat what?

Answer 9

Duodenal and gastric ulcers
Zollinger ellison syndrome
GERD
IV - critically ill patients to prevent stress ulcer (stessulcer prophylaxis)
Reduce perioperative risk of aspiration pneumonia

Must administer day before surgery at bedtime as well as 2 hours prior to surgery (renal elimination)

Question 10

H1 blockers are used to treat what?

Answer 10

Diphenhydramine (25 to 50 mg IV or PO, Lasts 4 to 6 hours)

Suppress allergic reactions (given with H2 blocker, blocks effects of histamine)
Suppress upper respiratory symptoms of allergic reactions
Vertigo
Motion sickness and other nausea and vomiting
Sedation
Cough suppression
Antimuscarinic effects (dystonic reactions of dopaminergic antagonists, decrease secretions)

Question 11

Effects of H1 blockers in anesthesia?

Answer 11

Sedative effects
Antianxiety effects
Decreased GI motility
Antimuscarinic like effects

Question 12

What do PPI do and what are the uses?

Answer 12

Pantoprazole, lansoprazole, omeprazole

• *They inhibit acid secretion** (Bind to the K+/H+ pump)
• Longer lasting effect ~ 24 hours, Slower onset

Uses: Duodenal ulcer, GERD, stress ulcer prophylaxis

Question 13

Metoclopramide MOA, uses, and adverse effects?

Answer 13

Dopamine receptor agonist - CNS with some muscarinic effects

Increases LES tone, speeds gastric emptying time by increasing GI motility, anti nausea effect requires very HIGH doses, NO effect on acid secretion

Uses: primarily for diabetic patients with gastroparesis, some GERD, prokinetic effect in anesthesia (0.15mg/kg IV), antiemetic dose is 1-2mg/kg IV -> adverse effects:

Adverse effects: dopamine antagonism, extrapyramidal effects, acute dystonic reaction (Oculogyric crisis, Torticollis), akithisia -> Treat with an antimuscarinic (or diphenhydramine)

Question 14

Rescue antiemetics

Answer 14

If N and V occur in PACU: administer antiemetic from different class of drug from what was used for prophylaxis (unless gave subtherapeuticdose)

Question 15

What are the 5 neurotrasmitters that cause PONV, what are ways to treat it?

Answer 15

Question 16

Location of neurological pathways involved in PONV

Answer 16

Question 17

What are the central mechanisms behind PONV

Answer 17

Higher cortical signals being communicated by the central pattern generator (formerly called the vomiting center) in the medulla

Fear, pain, anxiety, conditioned nausea related to environmental cues, and stimulation of the vestibular system are central stimuli that may cause nausea and vomiting

Question 18

What are the peripheral mechanisms behind PONV?

Answer 18

Trauma causing release of substance P and serotonin from enterochromaffin cells, thereby activating the vagal and splanchnic nerve 5-HT receptors

Vagal and splanchnic nerve afferents terminate in the nucleus tractussolitariusin the brain stem, near or within the area postrema(also called the chemoreceptor trigger zone)
-Bowel surgery and blood in the gastrointestinal tract from oral or ear, nose, and throat surgery may cause nausea and vomiting via this pathway

Question 19

How do opioids/volatiles induce PONV?

Answer 19

Both opioids and inhalation anesthetics may cause nausea and vomiting by stimulation of the area postrema at the base of the fourth ventricle in the medulla.

The area postrema then communicates with the central pattern generator via dopamine and serotonin to trigger the vomiting reflex

Question 20

5HT3 mechanism of action and uses? Adverse effects?

Answer 20

Selective for 5HT3 receptors located in GI tract (vagal afferents), and centrally (outside BBB)

Uses: especially useful for vagal stimulated PONV (chemo, postop), given towards end of procedure to help prevent vomiting

Adverse effects: lacks sedative effects, prolonged QT (avoid in patients at risk), may need to adjust in liver disease

Question 21

Dexamethasone uses and risks?

Answer 21

Uncertain of the antiemetic effect, slower onset (4mg IV beginning of case)

Uses: antiemetic, decreasing ICP (4-12mg)

Adverse effects: impaired glucose tolerance (6-12 hours of rise after administration), risk for wound infection

Question 22

Anticholinergic drug and adverse effects?

Answer 22

Scopolamine (IV or transdermal 1.5mg), apply several hours prior to surgery can be equally as effective as ondanestron

Adverse effects: dry mouth, blurry vision, older age maybe cognitive impairment

Question 23

Other dopamine receptor antagonists (butryophenones)?

Answer 23

Droperidol (0.625 to 1.25 mg IV) and Haloperidol (1 mg IV or 1 mg PO, or 1 mg IM)

Droperidol adverse effects: QT prolongation (black box warning), not used in children, risk for arrhythmia torsades de pointe, most likely at higher dose – when used for neuroleptanesthesia

Perphenazine (5 mg IV)

Promethazine (6.25 to 12.5 mg IV)

Prochlorperazine (5 to 10 mg IV)

Question 24

Neurokinin receptor antagonist MOA uses?

Answer 24

Substance P – neuropeptide that may mediate nausea and vomiting; central and peripheral

Antagonism of neurokinin-1 receptors - NK1 (peripherally and centrally)

Uses: reduce PONV

Aprepitant (80 mg PO)