Treatment of common GI conditions Flashcards
To be able to work up and manage a patient presenting with nausea, vomiting or diarrhea.
Weigh the patient, assess for dehydration
Assess for signs of malabsorption, malnutrition and concurrent illness
Careful history and physical exam essential
Laboratory assessment for malabsorption and nutritional parameters
Stool studies if available vs emperic treatment
Role of endoscopy if bleeding or anemia
Imaging studies
define: nausea
A vague, unpleasant or uneasy epigastric feeling
accompanied by the sensation that vomiting might occur
- typically preceded by anorexia, objectively associated with decreased gastric tone and gastric peristalsis
define: vomiting
The forceful expulsion of gastric contents through the mouth
- Typically preceded by anorexia and nausea
why and how do we vomit
1) Vagal afferent fibers carry signals from the gut mucosa to the CNS
2) Sympathetic afferents (from the GI tract, the heart, the vestibular system) synapse in the vomiting center in the medulla
3) Vomiting center collection of nuclei that coordinate act of vomiting
4) Afferents from the chemoreceptor trigger zone (CTZ) synapse in the vomiting center in the medulla as well
CTZ very sensitive to stimuli, toxins, neurotransmitters, meds
5) Afferent stimuli from higher levels in the CNS (cortex, thalamus, hypothalamus) synapse in the vomiting center as well.
6) These pathways involved in vomiting that occurs with unpleasant tastes, offensive odors, or somatic pain.
define: retching
Similar to vomiting, but occurs without expelling gastric contents
gagging
the initial motor movements involved in vomiting, mostly limited to the oral region
- non-specific
- may represent a hypersensitive pharyngeal reflex or
- the initial motor movements involved in vomiting
rugurgitation
The sudden, effortless, involuntary movement of small amounts of gastric contents into the esophagus or mouth.
- without the violence of vomiting
rumination
Food is chewed, swallowed, and then voluntarily regurgitated.
– usually psych background
what are the stages/acts of vomiting
Act 1
- The final common pathway from the vomiting center involves coordinated messages to the GI tract, diaphragm, abdominal wall muscles, palate, and oropharynx.
- The vagus and phrenic nerves are intimately involved, along with spinal nerves to the abdominal wall musculature.
- The vomiting reflex cannot occur without an intact vagus nerve.
Act 2
- Large amplitude small-bowel contractions
- Retrograde movement of bile and secretions into the stomach
- Pylorus contracts, stomach relaxes
- Abdominal wall muscles and diaphragm contract; respiration ceases
- LES relaxes, esophagus dilates
- Glottis closes, soft palate rises, mouth opens
What is the vomiting center?
- A collection of nuclei that are linked and which coordinate the complicated act of vomiting
- Not a discrete area in the brain
- When appropriately activated by afferent stimuli from the CTZ, the ANS, somatic afferents, or higher brain centers, then vomiting occurs.
what is the chemoreceptor trigger zone
- The chemoreceptor trigger zone is located in the area postrema of the floor of the 4th ventricle
- It is outside of the blood-brain barrier
- It is very sensitive to chemical stimuli, toxins, neurotransmitters, and medications
- Surgical ablation of this area prevents chemically induced vomiting (via apomorphine, a DA receptor agonist)
47yo female has just undergone cholecystectomy, on post-op check she has severe N/V
Diffdx:
- retained stone
-
47yo female has just undergone cholecystectomy, on post-op check she has severe N/V
dx?
tx?
Diffdx:
- retained stone
- bile leak
- pain
- ?complications from surgery
tx
- zofran
- compazine
what classes of antiemetics and what are their targets
- what drugs do we have for it
M1 – muscarinic D2 – dopamine H1 – histamine 5-hydroxytryptamine (HT)-3 – serotonin Neurokinin 1 (NK1) receptor – substance P
Phenothiazines (compazine) Antihistamines (meclizine, Diphenhydramine) Anticholinergics (scopolamine) DA antagonists (metoclopramide) 5HT-3 antagonists (ondansetron) Others: marinol, lorazepam, prednisone,
what are examples of antihistamines
- why do we use it
- ADRs
examples:
- Dimenhydrinate (Dramamine) 50 mg PO q 4 hrs
- Promethazine (Phenergan) = antihistamine + phenothiazine, 12.5 to 25 mg PO/IM/IV q 4 hrs or 12.5 to 25 mg PR q 12 hrs
- Meclizine (Antivert) 25-50 mg PO q 24 hrs
- Diphenhydramine (Benadryl) 25 to 50 mg PO q 6 hrs, or 10-50 mg IV/IM
use: especially with movement-associated nausea/vomiting
ADRs: sedation
what are examples of phenothiazines
- why do we use it
- ADRs
examples:
- prochlorperazine (compazine) 5 to 10 mg PO/IM q 6 hrs or 2.5 to 10 mg IV q 4 hrs or 25 mg PR q 12 h
- promethazine (phenergan) = phenothiazine and antihistamine
use:antagonizing D2-dopamine receptors in the area postrema of the midbrain (boat rides)
ADRs:
- Extrapyramidal Reactions:
- Acute dystonia and tardive dyskinesia Prolonged usage.
- Hypotension in elderly or when drugs are used IV
what are examples of anticholinergics
- why do we use it
- ADRs
examples: scopolamine transdermal 1.5mg q72h= M1-muscarinic receptor antagonist
use: prophylaxis against motion sickness / perioperatively, chronic N/V
ADRs: Dry mouth, drowsiness, visions disturbance
what are examples of 5HT-3 antagonists
- why do we use it
- ADRs
examples:
- Ondansetron (Zofran) 4-8 mg/IV or 4-24 mg PO
- Granisetron (Kytril)
- Dolasetron (Anzemet)
use:chemotherapy-induced emesis and now widely used for other causes (post op, post endoscopy)
ADRs: QTC prolongation in high doses (16-32mg total)
