GI- Aspiration prophylaxis & PONV Flashcards
What are antacids usually made of?
What are they used for?
- Made of aluminum, Calcium, and Magnesium salts
- Used to neutralize or remove acid from gastric content
- increase pH to >5
- they are not first line treatment for ulcers, but do increase ulcer healing and improve pain
What are the antacid agents available?
What are the adverse effects?
- Agents:
- Aluminum hydroxide
- Magnesium hydroxide
- Sodium Bicarbonate
- Calcium carbonate (tums)
- Adverse effects:
- Constipation
- diarrhea
- electrolyte abnormalities
What medication is used for preoperative nonparticulate antacid therapy?
Dose?
onset?
- Socium Citrate = Bicitra
- Clear antacids are show to cause less of a “foreign body reaction” if aspirated
- Dose: 15-30 ml PO
- Onset: rapid- give 15-30 minutes preop to facilitate adequate gastric mixing and emptying
- pH is 8.4, unpleasant taste
What are prokinetic drugs used for?
Example?
- Increase lower esophageal sphincter (LES) tone
- accelerates rate of gastric emptying
- enhances peristalsis
- Metoclopramide
What is Metoclopramide?
What does it stimulate?
- Dopamine antagonist- structure similar to procanamide but lacks local toxidity
- Kinetic ONLY, does not change gastric pH
- Cholinergic stimulation of GI tract:
- increased LES tone
- increased gastric and small bowel motility
- relaxation of pylorus and duodenum
- **does this by sensitizing smooth muscle to ACh. The affect is opposed by atropine & glyco
What are the CNS effects caused by metoclopramide
- Extrapyramidal effects
- stimulates prolactin secretion
- Anti emetic
- blocks dopamine stimulation of chemo receptor trigger zone (CRTZ)
What are the pharmacokinetics of metoclopramide?
absorption?
peak plasma conc.?
E1/2t?
excretion?
- Rapidly absorbed PO
- peak plasma concentration within 40-120 min
- E1/2t 2-4 hours
- Renal excretion, 40% unchanged
What are the uses of Metoclopramide?
- Decrease gastric fluid volume
- antiemetic
- treatment of gastroparesis
- symptomatic treatment of GERD
- Improve lactation ??
What are the periop doses of metoclopramide?
- 10-20 mg IV (over 3-5 min, 15-30 min prior to induction)
- Will cause severe abdominal cramping if administered too rapidly
- 0.15 mg/kg IV to mother after delivery of infant reduces PONV w/c-section
- 0.15 mg/kg in children post T&A decreases PONV
- 10 mg pre-induction in patients with diabetic gastroparesis
What are the side effects of metoclopramide?
- abdominal cramping- if administered too rapidly
- dardiac dysrhythmias- esp. when given with ondansetron
- sedation
- dry mouth
- dystonic extrapyramidal symptoms
- oculogyric crisis, trismus, torticollis, akathesia
- increases sedative actions of CNS depressants
- may or may not inhibit plasma cholinesterase activity
What are the contraindications of metoclopramide?
- bowel obstruction
- parkinson’s disease
- seizure disorders
- in combination with phenothiazines
- b/c or extrapyramidal symptoms and sedation
What is Serotonin (5HT)?
- 5-Hydroxytryptamine (5HT) synthesized from tryptophan
- important neurotransmitter for pain and nausea impulses
- 90% is in enterochromaffin cells in the gut
- 10% is in CNS and on platelets
- there are 7+ types of 5HT receptors
- many drugs act as serotonin antagonists
What are the 5HT antagonists used as anti-emetics?
Where do they work?
What are they used for?
- agents:
- Ondansetron
- Granisetron
- Dolasetron
- Tropisetron
- Selective antagonism at peripheral (in GI) and central receptors (CRTZ)
- Useful for:
- chemotherapy
- PONV
- hyperemesis gravidarum
What are the side effects of the 5HT antagonists?
metabolism?
- HA with rapid administration
- cardiac sysrhythmias- rare
- rely on liver metabolism
- reduce dosage in liver disease
What is the dosing for:
Ondansetron
Granisetron
Dolasetron
- Ondansetron:
- adults 4-8 mg IV
- peds 0.05-0.15 mg/kg IV (up to 4 mg)
- Granisetron (used for chemotherapy nausea)
- 0.01-0.04 mg/kg
- Dolasetron
- 12.5 mg IV
