Gastrointestinal 1

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Gastrointestinal 1
2012-03-30 11:09:13

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  1. List 9 GI clinical signs. What are the 3 most common GI signs?
    • vomiting
    • regurgitation
    • anorexia
    • weight loss
    • diarrhea
    • colic
    • bloat
    • flatulence
    • constipation
    • 3 most common: vomiting, diarrhea, anorexia
  2. If a patient shows vomiting, diarrhea, and anorexia, does this mean that the patient definitely has just a gastrointestinal problem?
  3. What 4 major factors affect the GI system?
    nervous system - autonomic nervous system, endocrine system - GI hormones, substances released by GI cells, bacterial toxins
  4. What are the 2 parts of the autonomic nervous system.
    • parasympathetic nervous system
    • sympathetic nervous system
  5. What general effects does parasympathetic stimulation have on the GI tract?
    increases digestive secretions, increases GI blood flow, increases gut motility and absorption, relaxes sphincters
  6. Do cholinergic drugs have sympathetic or parasympathetic effects?
    parasympathetic (cholinergic = acetylcholine)
  7. What general effects does sympathetic stimulation have on the GI tract?
    decreases digestive secretions, decreases GI blood flow, decreases gut motility and absorption
  8. Do anticholinergic drugs have sympathetic or parasympathetic effects?
    sympathetic (against acetylcholine)
  9. List 3 GI hormones.
    • gastrin
    • secretin
    • cholecystokinin
  10. List 2 substances released by GI cells.
    • prostaglandins
    • histamine
  11. What are the specific types of prostaglandins released by GI cells?
    PgE - prostaglandin e, and PgI - prostaglandin I
  12. Are the effects of prostaglandins in the GI tract protective or harmful? List the effects.
    protective. increases GI mucus and fluid production, decreases hydrochloric acid (HCl) production, increases intestinal motility, inceases GI blood flow, increases secretion or bicarbonate buffer in the mucus layer lining the stomach.
  13. Are the effects of histamine in the GI tract protective or harmful? List the effect.
    can be harmful. histamine increases hydrochloric acid production - HCl can damage gastric and duodenal mucosa.
  14. What cells release histamine, and under what conditions?
    basophils and mast cells release histamine - during inflammatory reactions and allergic reactions
  15. Histamine has to combine with histamine receptors in order to cause its effects. Where are H1 (histamine 1) receptors located? What does stimulation of H1 receptors cause?
    H1 receptors - bronchiolar smooth muscle - stimulation causes bronchoconstriction. also present in the skin.
  16. Where are H2 receptors located? What does stimulation of H2 receptors cause?
    H2 receptors - located on gastric parietal or oxyntic cells - in the stomach lining. stimulation causes increased HCl secretion.
  17. What effects do bacterial toxins have? How can bacterial toxins cause dehydration?
    have various effects. can cause fever, can stimulate gastric fluid production, can lead to diarrhea which can cause dehydration.
  18. What are "emetics"?
    drugs that induce vomiting.
  19. When is it useful to induce vomiting in a patient?
    used in poisoning cases to empty the stomach of the toxin. used before anesthesia to empty the stomach, to prevent vomiting or regurgitation and aspiration under anesthesia.
  20. What is the emetic, or vomiting, center, and where is it located?
    the emetic center is a part of the brainstem that controls the vomiting reflex - controls the muscles involved in vomiting.
  21. What 5 factors can stimulate the emetic center of the brain?
    direct stimulation of the vomiting center itself, irritation of peripheral receptors located in the GI tract and other organs innervated by the vagus nerve, stimulation of the CRTZ - area in brain that detects toxins. cerebral cortex stimulation (emotional) stimulation of inner ear.
  22. Vomiting can be caused by stimulation of what 3 types of receptors on the neurons of the emetic center?
    • alpha receptors
    • serotonin receptors
    • dopamine receptors
  23. Irritation of peripheral receptors can also cause vomiting by stimulating the emetic center. Where are these peripheral receptors located? These organs are innervated by a particular, important parasympathetic nerve - name it.
    GI tract, heart, pharynx, urinary tract, and other organs innervated by the vagus nerve.
  24. The CRTZ can stimulate the emetic center to cause vomiting. What is the CRTZ?
    chemoreceptor trigger zone - area of the brainstem that detects toxins in the blood and CSF. (for example - drugs, bacterial toxins). has free nerve endings - no blood brain barrier at the CRTZ - so it can be affected by toxins.
  25. What receptors are located in the CRTZ?
    dopamine receptors, H1 histamine receptors, alpha 2 receptors, serotonin receptors (5 - HT receptors - 5 hydroxytrptamine)
  26. What types of inner ear problems can stimulate the emetic center to cause vomiting?
    vestibular problems - inner ear infections, motion sickness.
  27. Stimulation of what type of receptor located in the inner ear can cause vomiting?
    vestibular problems - inner ear infections, motion sickness.
  28. Stimulation of what type of receptor located in the inner ear can cause vomiting?
    H1 - histamine receptors.
  29. Cerebral cortex stimulation of the emetic center can cause vomiting. What types of stimulation can do this?
    • pain
    • fear
    • excitement
    • emotional shock
  30. If we induce vomiting in a patient, does this completely empty out the stomach?
    no - removes about 80% of stomach contents.
  31. Within how many hours of ingestion of a liquid toxn would it be helpful to induce vomiting?
    2 hours - the sooner, the better
  32. Within how many hours of ingestion of a solid toxin would it be helpful to induce vomiting?
    4 hours - the sooner, the better
  33. List the circumstances when it is best not to induce vomiting.
    ingestion of caustic substance, ingestion of volatile liquids, patient is comatose, has seizures, shock, dyspnea, bloat, gastric torsion, esophageal damage. not in the horse, rabbit, or rat.
  34. What are the risks of inducing vomiting under unfavorable circumstances?
    aspiration, further damage to esophagus and mouth.
  35. What are the 2 general categories of emetics?
    centrally acting and locally acting
  36. How do centrally acting emetics work?
    directly stimulate receptors in the CRTZ.
  37. What centrally acting emetic is most appropriate for use in dogs? Why?
    apomorphine - directly stimulates dopamine receptors in CRTZ to cause vomiting - dogs havemore dopamine receptors than cats.
  38. What centrally acting emetic is most appropriate for the use in cats? Why?
    xylazine - Rompun - directly stimulates alpha 2 receptors in CRTZ and the emetic center - cats are more sensitive to alpha 2 stimulation than dogs.
  39. What percentage of cats vomit when given xylazine? What percentage of dogs vomit when given xylazine?
    • cats - 90%
    • dogs - 50%
  40. How do locally acting emetics work?
    GI irritation - act on peripheral receptors in the GI tract.
  41. What locally acting emetic works most consistently? Is it still available?
    • syrup of ipecac.
    • yes, it is still available, but maybe not for long
  42. List 3 other locally acting emetics a client might have at home. How reliable are these?
    • hydrogen peroxide
    • warm concentrated salt water
    • powdered mustard and water
    • not very reliable
  43. What are "antiemetics"?
    drugs that reduce or prevent vomiting.
  44. Should all vomiting be stopped? Why or why not?
    no. initially, vomiting removes irritants from the GI tract.
  45. List the 5 main categories of antiemetics drugs.
    • phenothiazines
    • metoclopramide
    • antihistamines
    • anticholinergics
    • serotonin antagonists
  46. What are the most effective antiemetics in small animal medicine?
    phenothiazines - acepromazine
  47. How do phenothiazines work?
    block dopamine receptors in CRTZ and emetic center, also antihistaminic
  48. Do phenothiazines stop all types of vomiting?
    no - do not block local GI irritation - visceral stimulation.
  49. Why should you avoid using phenothiazines in patients who are dehydrated or in shock?
    alpha 1 blockers - block vasoconstriction - cause vasodilation and hypotension - low blood pressure.
  50. Name 3 specific phenothiazines.
    • acepromazine
    • chlorpromazine
    • prochlorperazine
  51. What specific drug is most commonly dispensed to clients for car-sickness in their pets?
  52. Why should you avoid using phenotiazines in seizure patients?
    lowers the seizure threshold.
  53. Which antiemetic drug is used for more serious vomiting - vomiting due to chemotherapy, parvovirus, or uremia?
    metoclopramide - Reglan
  54. Briefly describe metoclopramide's "central" activity.
    central - means working in the brain. metoclopramide blocks dopamine and serotonin receptors in the CRTZ.
  55. Briefly describe metoclopramide's local activity.
    is "prokinetic" - increases GI motility. increase lower esophageal and cardiac sphincter tone, increases gastric motility, speeds gastric epmtying, relaxes pylorus, incraeses upper intestinal motility.
  56. What does "prokinetic" mean?
    increases GI motility.
  57. Which antiemetic drug is indicated for patients with gastraic atony or delayed gastric emptying?
    metoclopramide - Reglan
  58. Are antihistamines very effective in animals for preventing vomiting due to motion sickness?
  59. List 2 antihistamines.
    • dimenhydrinate - Dramamine
    • diphenhydramine - Benadryl
  60. List 2 anticholinergic drugs that may be used as antiemetics.
    • atropine
    • aminopentmide - Centrine
  61. Is atropine a weak or a strong antiemetic?
  62. List one serotonin antagonist that may be used for severe vomiting not responsive to other drugs. Why is this drug not used very much?
    • ondansetron - Zofran
    • it is very expensive