colonoscopy prep Flashcards
what are the types of bowel preps
isosmotic
hyper-osmotic
stimulant laxatives
What is isosmotic prep
no permeation of cell membranes
these are PEG (polyethylene glycol) - based electroylet lavage solutions
negligible absorption from GI tract
what is the MOA for PEG
osmotic effect of PEG causes water to be trained in colon - produces watery stool
no significant changes in water or electrolyte balance occur
what are the full volume isosmotic preps
colyte
GoLYTELY
NuLYTELY
TriLyte
what are the low volume preps
HalfLytely
Miralax
MoviPrep
what are the advantages of PEG-based preps
no mucosal damage
minimal osmotic fluid shifts
safer than sodium phosphate-based solutions in patients with impaired renal function, CHF, cirrhosis or baseline elecytrolyte abnormalities
what are the disadvantages of PEG-based preps
large volume of fluid (4L)
unpalatable taste (if not flavored)
what are contraindications of PEG-based solution
patients with gastric outlet obstruction
high-grade small bowel obstruction
suspected bowel perforation
how often is PEG-based solutions taken
240ml (8oz) every 10 minutes
what is a hyperosmotic prep
contains a higher concentration of salts or other dissolved material than normal tissues
what is the MOA of hyperosmotic preps
increase intraluminal water (pulls water into intestine) by promoting passage of extracellular fluid across the bowel wall
high Na+ concentration - causes watery diarrhea
what is the main formulation of hyperosmotic preps
sodium phosphate
what are the hyperosmotic preps
OsmoPrep
Suprp
Prepopik
Clinpiq
what is the first FDA approved ready to drink low volume bowel prep
clenpiq
what is the MOA of clinpiq
prodrug, has no significatn direct physiological effect on the intestine
metabolized by gut bacteria into active compound 4,4’-dihydroxydiphenyl-(2-pyridiyl) methane (DPM, DPHM)
what does DHPM act on
directly on the colon, stimulating peristalsis
what are contraindications for Clenpiq
creatinine clearance < 30ml/min - may lead to accumulation of magnesium
what are the advantages of hyperosmotic preps
small volume (though additional fluids must be consumed as well)
more palatable than PEG-based solutions
what are the disadvantages of hyperosmotic preps
potential for causing fluid and electrolyte shifts by drawing water into the intestine
renal damage
what are the risks of NaP bowel prps
acute phyosphate nephropathy
patients at most risk: increased age, hypovolemia, decreased bowel transit time, activity colitis, baseline kidney disease)
what are contraindicatiosn to NaP bowel preps
pediatric patients
elderly patients
patients with bowel obstruction
renal insufficiency or failure
CHF
liver failure
what is the MOA oof stimulatn laxatives
increase smooth muscle activity (peristalsis)
ex. senna,busacodyl, sodium picosulfate
what does senna do
increase rate of motility - enhances colonic transit and inhibits water and electorylte secretion
often used as adjunct to PEG regimens
what does Bisacodyl do
2 MOA: stimulation of small intestine enzyme secretion and increased motor activity within the colon
what is the rationale of “split-dose regimen”
better tolerated by patients
part of purgative is taken the evening before and the remainder is taken the morning of the procedure
what is “split-dose regimen”
part (usually 1/2) of laxative takne evening prior and remaineder am of procedure (3-8 hours before)
colonoscopy should be performed within 8 hours of last dosing
what are the barriers of split dosing
patient acceptance of sleep disturbances
bowel activity in transit to procedure
non-compliance with pre-procedure fasting fuidelines
what are dietary recommendations prior to colonoscopy
~2 days before colonoscopy - low fiber, no while grains, nuts, seeds, dried fruit or raw fruits/vegetables
day before: no solid foods (clear liquids only)
the day of: clear liquid only - dont eat or drink 2 hours prior to procedure
what patients characterisitcs increase the risk of a bad prep
elderly
obesity
lower education
hx constipation
hx of non-compliance or poor response to prep
