Practical Gastrointestinal Endoscopy

COLONOSCOPY AND FLEXIBLE SIGMOIDOSCOPY 95
can be expected within 2–3 ·hours. For the seriously constipated,
magnesium sulfate, although unpleasant-tasting, is highly effective
if taken in repeated hourly doses (5 ·mL of crystals in 200·mL
hot water, followed by juice and other fluids) and guaranteed
eventually ‘to move mountains’.
Sodium phosphate
Sodium phosphate, presented as a flavored half-strength
orally administered equivalent of the phosphate enema (Fleet’s
Phospho-soda®), has received numerous good reports when
trialed against PEG-electrolyte preparation. It proves to be as
effective as PEG-electrolyte solution but significantly more acceptable
to patients, principally because the volume ingested is
only 90·mL. It must be followed by at least 1 liter of other clear
fluids of choice—water, juices, lager, etc. No large trial has been
made against other apparently very acceptable and effective regimes—such
as the senna/magnesium citrate combination.
Routine for taking oral preparations
Low-residue diet instructions should have been followed. The
patient is preferably supplied with petroleum jelly or barrier
cream to avoid perianal soreness (colorless if possible to avoid
endoscope lens contamination).
As mentioned above, large-volume PEG-electrolyte solutions
are ideally split-administered in two doses, starting on the
evening beforehand but with the remainder taken on the morning
of the examination so that the cecal contents remain fluid. If
an afternoon examination is scheduled, and the patient does not
have a long distance to travel, both doses can be drunk on the
day of examination. If in doubt, a purgative (such as senna, 4–6
tablets) can be also be taken at the previous bedtime in order to
‘prime the pump’.
PEG-electrolyte solution should be drunk at a rate of around
1.5·L/h (250·mL/10·min initially). Chilling mannitol solution
makes it taste much less sweet; cooling PEG-electrolyte solution
also improves palatability but may overcool the drinker
too. Adding sugar-containing flavoring agents, such as fruit
cordials, to PEG-electrolyte solution is discouraged on the theoretical
basis that increased sodium absorption could occur, but
using ‘diabetic’ cordials would avoid this. Sodium phosphate
solution is easily downed with a ‘chaser’ of some more pleasant
drink, and then 1 liter or more of any fluid to follow in the next
hour or two.
The patient should be encouraged to carry on with normal
activities, rather than sitting still during the drinking period, in
order to encourage transit. Drinking should stop temporarily if
nausea or uncomfortable distension occurs. Bowel actions should