1. Nausea, Vomiting & Constipation

2. Objectives PART I Discuss common causes for nausea and vomiting
Identify the areas of the body and receptors involved that stimulate nausea and vomiting
Select medications to help control nausea and vomiting

3. Objectives PART II Define constipation
Review the physiology of bowel movements
Assessment and treatment of constipation

4. Incidence
Nausea: %
Vomiting: %
Constipation: %

5. DDx Metastases Mechanical Obstruction Meningeal irritation Motility
Movement
Metabolic
Mental anxiety
Microbial
Medications

6. Mechanism of Nausea and Vomitng

7. Mechanism of Nausea and Vomiting
Vomiting centre in reticular formation of medulla
activated by stimuli from:
Chemoreceptor Trigger Zone (CTZ)
area postrema in floor of 4th ventricle
outside of BBB (fenestrated venules)
Upper GI and pharynx
Vestibular apparatus
Higher cortical centres

8. Receptors Acetylcholine (AchM) Histamine (H1) Dopamine (D2)
Serotonin (5-HT3)
GABA
THC
Neurokinin (NK)

9. Mechanism of Nausea and Vomiting

10. Vestibular
(H1 AchM)
Movements
Opioids
Chemoreceptor Trigger Zone

11. Chemoreceptor Trigger Zone (5-HT3 D2 NK and more)
Toxins
Metabolites
Tumour Factors
Vestibular System
Drugs
Vagus nerve

12. Cerebral Cortex (GABA 5-HT3)
Meningeal irritation
ICP
Hyponatremia, Hypercalcemia
Opioids
Pain
Past experiences
Anxiety / Fear
Tastes / Smells

13. Vagus Nerve (5-HT3 NK AchM)
Mechanoreceptors
Chemoreceptors
Hepatic Chemoreptors

14. GI Tract
(D2 5-HT3 AchM)
Drugs
Obstruction
Medical comorbities

16. Medications Dopamine antagonists H1 antagonists (antihistaminics)
Serotonin antagonists
Antimuscarinic (anticholinergics)
others

17. Dopamine (D2) antagonists
Metoclopramide (maxeran)
10 mg po/sc/iv q4h
Domperidone
10 mg po qid
Prochlorperazine (Stemetil)
10 mg po/IV q4h
Haloperidol
1-2 mg po/sc/iv q4h
Methotrimeprazine

18. H1 antagonists Dimenhydrinate (Gravol) 25-50 mg po/sc/iv q4h
Promethazine (Phenergan)
25 mg po/iv q4h

19. Serotonin (5-HT3) antagonists
Ondansetron (Zofran)
4-8 mg po/sc/iv q8h
Granisetron (Kytril)
1 mg po/sc/iv q12h

20. Antimuscarinic
Scopolamine
Transform V patch q3d

21. Others
Nabilone
Dronabinol
Dexamethasone
Lorazepam

22. Principles of treating nausea and vomiting
Treat the cause if possible
Environmental measures
Antiemetic use
Anticipate need
Aim at presumed receptors (?)
Use adequate, regular doses
Use combinations if necessary
Use of alternate routes

24. Constipation Passage of small, hard stools Painful passage (straining)
Prolonged interval
N range: 3 in 1d to 1 in 3d

25. Physiology of a BM Coordinated effort: Motility (peristalsis)
Intact ANS
Hormonal activity
Mucosal transport
Defecation reflex
Coordination of motility, mucosal transport and reflexes. Motility needs CNS and ANS activity both para- and sympathetic systems and the function of hormones. 3 types of motility: segmental (non-propulsive) short-segment propulsive and long-segment propulsive. Segmental movement churn and mix, peristalsis moves forward. Incr. in segmental, nonpropulsive movements ass’d with constipation

26. Etiology
Malignancy
obstruction, compression, neural damage, spinal cord (cauda equina), hypercalcemia
Poor po, dehydration, weakness/inactivity, confusion, depression, unfamiliar toilet arrangements
Medications
Opioids, anticholinergic activity, TCA, antacids, diuretics, iron supplements, 5HT3
Concurrent Disease
Diabetes, hypothyroid, hypokalemia, hernia, anal fissures, hemorrhoids

27. Opioid effects impaired defecation reflex
↑ ileocecal & anal sphincter tone
↓ peristaltic activity
impaired defecation reflex
↓ sensitivity to distension
↑ electrolyte & water absorption

28. Assessment History Last BM? Frequency? stool characteristics?
Painful defecation?
Urge present but no stool?
No urge?
Blood?
N/V?
DRE?

29. Assessment
Physical
DRE
Masses, distension, BS
Pelvic exam

30. Constipation Score Flat plate of abdomen
4 quadrants - ascending, transverse, descending, rectosigmoid
No stool = <50% = 1
>50% = % = 3
CS > 7/12 requires treatment

31. Treatment Prophylaxis Good symptom control Activity Hydration
Recognize drug effects
Create a favourable environment

32. Treatment: Laxatives 80% of patients need laxatives
Little research to guide choice
Stimulants are often considered best first choice

33. Treatment Options Bulk forming agents: psyllium Surfactants: docusate
Contact cathartics: senna, bisacodyl
Osmotic laxatives: lactulose, PEG 3350
Saline osmotic: MgOH, phosphosoda
Enemas: oil, saline, soap suds, fleet

34. Treatment Options
Pro kinetic agents: cisapride, domperidone, metoclopramide
Antibiotics: erythromycin
Opioid antagonists: naloxone, methylnaltrexone
Cholinergic: pilocarpine
Herbal preparations: mulberry, rhubarb, licorice

35. QUESTIONS?