Adjuncts to anesthesia

Question 1

Antihistamines

Answer 1

H1 and H2 receptor antagonists or H2 blockers

Question 2

Stimulation of H1 receptors in the GI tract leads to

Answer 2

Contraction of intestinal smooth muscle

Question 3

Stimulation of H2 receptors in parietal cells leads to

Answer 3

Gastric acid secretion H+ (hydrochloric acid)

Question 4

H2 blockers used to treat

Answer 4

1.) duodenal and gastric ulcers
2.) Zollinger Ellison syndrome (too much gastric acid)
3.) GERD
4.) IV - critically ill patients to prevent stress ulcers (stress ulcer prophylaxis)
5.) effect pH - acid secretion - but only post administration
6.) USED TO REDUCE PERIOPERATIVE RISK OF ASPIRATION PNEUMONIA

Question 5

H2 blocker if used to reduce aspiration risk

Answer 5

1.) must administer at bedtime the day preceding the procedure plus 2 hours prior to procedure
2.) depends on renal elimination

Question 6

H2 blocker examples

Answer 6

Ranitidine (50mg IV)
Famotidine (20mg IV)
Nizatidine (150 to 30mg PO)
Cimetidine (rarely used due to CYP450 effects)
All have around 10-12hrs of acid suppression

Question 7

H1 Blocker uses

Answer 7

Not a primary drug to prevent aspiration
1.) suppress allergic reactions
2.) suppress upper respiratory symptoms of allergic reactions
3.) Vertigo
4.) Motion sickness and other nausea and vomiting
5.) Sedation
6.) Cough suppression
7.) Antimuscarinic effects (dystonic reactions of dopaminergic antagonists, decrease secretions)

Question 8

H1 blocker use in anesthesia

Answer 8

1.) sedative effects
2.) anti anxiety effects
3.) decreased GI motility
4.) antimuscarinic like effects

Question 9

H1 blocker for allergic reactions

Answer 9

Given with H2 blocker and blocks the effects of histamine on capillary permeability, hypotension, cardiovascular, pulmonary, upper respiratory, and dermal

Question 10

H1 blocker example

Answer 10

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

Question 11

Proton pump inhibitor

Answer 11

Inhibits acid secretion
1.) binds to K+ H+ pump
2.) longer lasting effects around 24 hours
3.) slower onset
Used for treatment of duodenal ulcer, GERD, and stress ulcer prophylaxis

Question 12

Proton pump inhibitor drugs

Answer 12

Pantoprazole, lansoprazole, and omeprazole

Question 13

Metoclopramide

Answer 13

1.) Dopamine receptor antagonist - central
2.) Some muscarinic agonist effects
3.) Increases LES tone
4.) Increases GI motility - not secretions. This decreases GI transit times and speeds up gastric emptying time. Lowers gastric fluid volumes
5.) No effect on gastric acid secretion or pH
6.) CTZ - antinausea effect requires very high doses

Question 14

Metoclopramide uses

Answer 14

1.) Chronic therapy - used primarily for patients with diabetic gastroparesis
2.) some GERD
3.) In anesthesia - 0.15mg/kg IV for pro kinetic effects. True antiemetic effect does is 1-2mg/kg IV - adverse effects
4.) renal elimination

Question 15

Metoclopramide adverse effects

Answer 15

1.) dopamine antagonism
2.) extrapyramidal effects (muscle spasms)
3.) Acute dystonic reaction. Oculogyric crisis (disconjugate eyes) and torticollis (neck muscle make head twist)
4.) Akathisia (restlessness)
Treat these with an antimuscarinic (or diphenhydramine)

Question 16

Receptor causes of N&V and their pharmacologic options

Answer 16

1.) M1 - antimuscarinic
2.) dopamine D2 - D2 receptor antagonist
3.) H1 - antihistamine
4.) Serotonin (5HT3) - 5HT3 receptor antagonist
5.) Neurokinin 1 (NK1) substance P - NK1 receptor antagonists
6.) corticosteroids

Question 17

5HT3 receptor antagonists

Answer 17

1.) selective for 5HT3 (avoid dopaminergic effects)
2.) Receptor locations - GI tract (vagal afferents) and Central (CTZ outside of the blood brain barrier)
3.) especially useful for emesis attributable to vagal stimulation (postoperative and chemotherapy)
4.) useful for prevention and treatment of vomiting. Often given near end of operative procedure. Some want to save and use for possible rescue therapy in PACU

Question 18

5HT3 receptor antagonists

Answer 18

1.) Lack sedative side effects
2.) Undergo hepatic metabolism CYP enzymes (may adjust ondansetron in hepatic disease)
3.) Risk for prolonged QT (avoid in patients at risk and concern when combined with other drugs)

Question 19

Dexamethasone (glucocorticoid)

Answer 19

1.) uncertain of mechanism (thought to be direct acting and have some benefit by reducing post op pain)
2.) slower onset - give at induction
3.) Intense perineal (or whole body) during with IV push (give slow)
4.) antiemetic dose - 4mg
5.) May also be used to decrease ICP (4 to 12mg)
6.) Impaired glucose tolerance (see rise about 6 to 12 hours after administration
7.) theoretical concern about increase risk for wound infection

Question 20

Antimuscarinic - scopolamine

Answer 20

1.) IV or transdermal 1.5mg
2.) transdermal is sustained release long acting patch
3.) Apply several hours prior to anesthesia
4.) shown to be equal to ondansetron and droperidol for PONV prophylaxis

Question 21

Scopolamine adverse effects

Answer 21

Typically mild
1.) dry mouth
2.) blurry vision
3.) older age may lead to agitation, cognitive impairment

Question 22

Antihistamines

Answer 22

Diphenhydramine and dimenhydrinate

Question 23

Dopamine receptor antagonists

Answer 23

Blocks D2 receptors in chemoreceptor trigger zone (CTZ)
1.) Butyrophenones (Droperidol 0.625-1.25 mg IV and Haloperidol 1mg IV, PO, or IM)

Question 24

Droperidol - D2 blocker

Answer 24

1.) not used in children
2.) FDA box warning due to QT prolongation risk
3.) risk for arrhythmia tornadoes de pointe
4.) most likely at higher doses - when used for neuroleptic anesthesia

Question 25

Dopamine receptor blocker adverse effects

Answer 25

1.) dopamine antagonism
2.) Extrapyramidal effects
3.) Acute dystonic reaction (oculogyric crisis and torticollis) treat with antimuscarinic or diphenhydramine
4.) akathisia
5.) Prolonged QT/arrhythimia risk (require telemetry monitoring for 2-3 hours after IV dose

Question 26

D2 receptors antagonist drugs

Answer 26

1.) Metaclopramide?
2.) perhenazine 5mg IV
3.) promethazine 6.25-12.5mg IV
4.) Prochlorperazine 5-10mg IV

Question 27

Neurokinin receptor antagonist

Answer 27

1.) substance P - neuropeptide that may mediate nausea and vomiting; central and peripheral
2.) acts at neurokinin-1 receptors - NK1
3.) NK1 antagonists inhibit at both central and peripheral receptors
4.) reduce N and V
5.) Aprepitant 80mg PO (especially helpful in delayed N&V)