Constipation Flashcards
1
Q
What is constipation?
A
- Difficult passage of hard or infrequent stool
- Decrease in stooling frequency to 2 or less times / week
- Rome criteria not relevant to palliative patients
- Rome criteria:
- 3 months
- straining 25% of time
- sensation of anorectal fullness 25%
- lumpy or hard stool 25% of time
- < 3 BM/week
2
Q
List factors that predispose to constipation
A
- diet lacking in fibre
- malnutrition
- decreased mobility
- environmental factors (lack of privacy, inconvenient facilities)
- medications ***
- Metabolic disorders
- dehydration, hypercalcemia, hyponatremia, uremia, hypothyroidism)
- Advanced age
- Depression
- Malignancy
- Neurologic disorders (SCC, autonomic dysfunction)
- Altered attention to rectal fullness in elderly
3
Q
List medications that are constipating
A
- Diuretics
- chemotherapy (vincristine, platinums)
- Opioids
- Sedatives
- Antacids
- Antipsychotics
- Anticholingerics
- TCAs
- NSAIDS
- Antihistamines
- Iron
- Ondansetron
4
Q
Describe normal bowel function
A
- Normal bowel function:
- coordination of gut motility, molecular transport across bowel wall and reflexes of defecation
- motility : autonomic nervous system + hormones
- Adrenergic, muscarinic, dopaminergic, opioid receptors
- gut contents 2-4 hours in small bowel, 24-48 hours in large bowel
- peristalsis 2 peaks : morning after waking, midday meal
- 2 neurotransmitters :
- Acetylcholine (ascending contraction)
- Vasoactive peptide (descending relaxation)
5
Q
How do opioids cause constipation?
A
- Prolong intestinal transit time in small and large intestine
- Results in increased fluid absorption
- Opioids increase rectal sphincter tone
- Reduce awareness of rectal filling
6
Q
Approach to constipation treatment
A
- Prevention is primary goal
- ongoing monitoring, anticipate constipating meds
- adequate fluid intake (1.5L/day), physical activity, fibre intake,
- All patients on opioids should be on regular scheduled prophylactic bowel regimen
- PRN laxatives little role : leads to diarrhea/constipation, non adherence to medications
- titrate to response of stool, not opioid
- Canadian Consensus Recommendations :
- stimulants (senna, bisacodyl) first alone or with
- osmotic laxatives (PEG, lactulose)
- second line : suppository / enema
- Third line: methylnaltrexone, etc
7
Q
How would you conduct an assessment for constipation?
A
- History:
- pattern, frequency BM
- quantity and quality
- pain
- change
- associated symptoms (fever, pain, cognition)
- URINARY RETENTION / INCONTINENCE
- Physical
- abdominal exam
- bowel sounds (low pitched infrequent)
- distended bladder
- volume status
- Stool appearance
- anal area : excoriation, fissure, fistula, hemorrhoids
- DRE: NO septic or neutropenic patients
- empty and ballooned rectum (proximal fecal mass)
- empty and collapsed rectum (no rectal impaction)
- loaded rectum (fecal impaction)
- Bowel performance Scale
- Imaging : flat plate and upright abdo Xray (2 views)
- Scoring
- Ascending, transverse, descending, rectosigmoid
- 0-3 score (0= no stool, 1 - stool < 50% lumen, 2 - stool > 50% lumen, 3 -stool 100% lumen
- score > 7/12
8
Q
Bulk forming laxatives
A
- Bran, psyllium, methylcellulose
- Onset :24-72 hours
- SE: bloating, flatulence
- MOA:
- increased stool bulk, decreased transit time, increased motility
- requires adequate fluid intake
- not suitable advanced disease
9
Q
Surfactant laxatives and stool softeners
A
- Docusate:
- onset 24-72 hours
- SE : well tolerated, cramps, diarrhea, nausea
- MOA: detergent, increased water penetration, softens stool
- Mineral oil
- onset 6-8 hours
- SE: malabsorption of fat soluble vitamins, other medications, risk of lipid pneumonia
- MOA: lubricates and softens stool.
- Not recommended orally
10
Q
Stimulant laxatives
A
- Senna, bisacodyl
- Onset: 6-12 hours
- SE: cramping, electrolyte disturbances
- MOA: myenteric plexus stimulation, increased peristalsis/motility, decreased fluid absorption
11
Q
Saline laxatives
A
- Magnesium citrate, sodium phosphate
- onset 1-6 hours
- SE: electrolyte disturbances
- MOA: osmotically active particles draw fluid into colon
- Different from PEG because can be absorbed and cause lyte disturbances
- Caution in CHF, RF, hypertension
12
Q
Osmotic laxatives
A
- Lactulose and sorbitol
- Onset 24-48 hours
- SE: sweet taste, nausea, cramps, flatulence
- MOA: non absorbable molecules draw fluid into intestinal lumen, increased fecal weight, mechanical distention causing peristalsis
- Polyethylene glycol PEG
- onset 24-72 hours
- SE: no increase in gas, mild diarrhea
- MOA: non absorbable molecules draw fluid in
13
Q
Suppositories
A
- Glycerine
- onset 0.25-1 hour
- SE: rectal irritation
- MOA: softening of stool in rectum
- Bisacodyl
- onset 0.25-1 hour
- SE: rectal irritation
- MOA: distention of rectum, similar to senna
14
Q
Enemas
A
- Saline:
- onset 0.25 hour
- SE: rectal irritation
- MOA: increase intestinal water secretion, peristalsis, useful for impaction
- Sodium phosphate (fleet):
- onset 0.25 hour
- 150 ml sodium
- SE: rectal irritation, hypocalcemia
- MOA: same as above, useful for impaction
- Mineral oil enema
- onset 1 hour
- SE: rectal irritation
- MOA: softens impacted stool. High enema retained overnight
- use a foley catheter high in descending colon, inflate balloon. Follow with high saline enema.
- Tap water / soap suds enema
- not recommended, risk of changes in blood volume and electrolytes
15
Q
Prokinetic agents
A
- Domperidone
- Onset 0.1-1 h
- SE: rare
- MOA: D2 antagonist, does not cross BBB
- Metoclopramide
- onset 0.5-1h
- SE: EPS
- MOA: D2 antangonist, cholingeric agonist
16
Q
Opioid antagonists
A
- Methylnaltrexone (peripheral mu receptor antagonist)
- onset 1-24 h
- SE: no loss of analgesia, cramping
- MOA : peripheral mu antagonist, contraindicated in bowel obstruction
- reduced permeability to BBB, selectively acts on GI tract
- indicated for patients on opioids who are not responding to osmotic laxatives
- Naloxone
- onset 1-3 h
- SE: opioid withdrawal, pain,
- MOA : opioid antagonism, limited use for constipation
- Naltrexone
- MOA: central and peripheral opioid receptor antagonist
17
Q
5HT4 receptor AGONISTS and Lubiprostone
A
- Lubiprostone
- chloride channel activator in small and large intestine
- increases intestinal fluid secretions
- Prucalopride:
- selective 5HT4 receptor agonist
- increases colonic motility and transit
18
Q
List laboratory tests that could possibly be helpful in constipation
A
- calcium
- Na (hyponatremia)
- K (hypokalemia)
- TSH
- CR, urea (dehydration, uremia)
- Liver enzymes
19
Q
Constipation in SCC
A
- loss of rectal sensation, loss of voluntary control, poor tone, immobility
- cauda equina abolishes ano-colonic reflex
- Higher spinal cord lesion leaves reflex intact
- “Controlled continence”:
- daily oral laatives with suppostitory or enema q2-3 days
20
Q
Opioids and constipation : what medications are best for pain control in someone with constipation?
A
- transdermal fentanyl patch : less constipating vs morphine
- reduces direct effect of opioid on receptors in gut
- lipophilic
- Methadone may be less constipating
- when rotated, decrease in MEDD, less activity on receptors in gut
- partial activity on NMDA receptors, ? less mu activity
- oxycodone CR and naloxone combo (Targin)
- less constipation
21
Q
Intestinal Fluid Handling
A
- 7L fluid secreted into gut everyday (mucosal crypt cells)
- 1.5 L dietary fluid
- reabsorbed in jejunum (villous cells)
- 1L enters colon
- Difference between constipation and diarrhea is only 100ml/day
- enteric nervous system stimulates secretion and smooth muscle contraction
- 5HT, substance P, VIP
22
Q
List cormorbid conditions that cause constipation in palliative care patients
A
- Diabetes
- hypothyroidism
- hypokalemia
- hernia
- diverticular disease
- rectocele
- anal fissure
- hemorrhoids
- colitis
