Adjuncts to anesthesia Flashcards
Antihistamines
H1 and H2 receptor antagonists or H2 blockers
Stimulation of H1 receptors in the GI tract leads to
Contraction of intestinal smooth muscle
Stimulation of H2 receptors in parietal cells leads to
Gastric acid secretion H+ (hydrochloric acid)
H2 blockers used to treat
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
H2 blocker if used to reduce aspiration risk
1.) must administer at bedtime the day preceding the procedure plus 2 hours prior to procedure
2.) depends on renal elimination
H2 blocker examples
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
H1 Blocker uses
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)
H1 blocker use in anesthesia
1.) sedative effects
2.) anti anxiety effects
3.) decreased GI motility
4.) antimuscarinic like effects
H1 blocker for allergic reactions
Given with H2 blocker and blocks the effects of histamine on capillary permeability, hypotension, cardiovascular, pulmonary, upper respiratory, and dermal
H1 blocker example
Diphenhydramine (Benadryl) 25 to 50mg IV or PO. Lasts 4 to 6 hours
Proton pump inhibitor
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
Proton pump inhibitor drugs
Pantoprazole, lansoprazole, and omeprazole
Metoclopramide
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
Metoclopramide uses
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
Metoclopramide adverse effects
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)
Receptor causes of N&V and their pharmacologic options
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
5HT3 receptor antagonists
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
5HT3 receptor antagonists
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)
Dexamethasone (glucocorticoid)
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
Antimuscarinic - scopolamine
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
Scopolamine adverse effects
Typically mild
1.) dry mouth
2.) blurry vision
3.) older age may lead to agitation, cognitive impairment
Antihistamines
Diphenhydramine and dimenhydrinate
Dopamine receptor antagonists
Blocks D2 receptors in chemoreceptor trigger zone (CTZ)
1.) Butyrophenones (Droperidol 0.625-1.25 mg IV and Haloperidol 1mg IV, PO, or IM)
Droperidol - D2 blocker
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
Dopamine receptor blocker adverse effects
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
D2 receptors antagonist drugs
1.) Metaclopramide?
2.) perhenazine 5mg IV
3.) promethazine 6.25-12.5mg IV
4.) Prochlorperazine 5-10mg IV
Neurokinin receptor antagonist
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)
