Practical Gastrointestinal Endoscopy

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CHAPTER 6
Benzodiazepines have a useful mild smooth-muscle antispasmodic
action as well as their anxiolytic effect. Diazepam
(Valium®) is poorly soluble in water and the injectable form
is therefore carried in a glycol solution that can be painful and
cause thrombophlebitis, especially if administered into small
veins. If a hand vein is to be used, and also for pediatric practice,
it is better either to use water-soluble midazolam (Versed®) or
diazepam in lipid emulsion (Diazemuls®, where available), both
of which are less irritant. Midazolam causes a greater degree of
amnesia, which can be useful to cover a traumatic experience
but also ‘wipes’ any explanation of the findings, which must be
repeated later on. It should be borne in mind that intravenous
midazolam dosage should be half that of diazepam.
Opiates (pethidine notably) induce a useful sense of euphoria
in addition to analgesic efficacy. Pethidine may cause local pain
when administered through small veins, particularly in children,
but this can largely be avoided by diluting the injection 1·:
·10 in water. Some endoscopists prefer to give pethidine (meperidine)
intramuscularly 1·h beforehand. Pentazocine (Fortral®)
is a weaker analgesic, more hallucinogenic and seems to have
little to recommend it. Fentanyl (Sublimaze®) is a very shortlived
opiate, but has the disadvantage of significant respiratory
depressant effects without giving any sense of well-being.
Propofol (Diprivan®), a short-lived intravenous emulsion
anesthetic agent, is widely used for colonoscopy in some countries
(France, Germany, Australia) and sporadically in others.
It should ideally be administered by an anesthetist because of
the significant risk of marked respiratory depression but, with
appropriate training and safeguards, has been employed by
endoscopists alone. Its short duration of action—giving full recovery
within about 30·minutes—is an advantage over excessive
doses of conventional sedatives. On the other hand, the patient
is rendered insensible and so unable to co-operate with changes
of position or to give early warning of excessive pain. The routine
use of propofol for all cases cannot therefore be recommended.
Antagonists
The availability of antagonists to benzodiazepines (flumazenil)
and opiates (naloxone) is invaluable, providing a safety measure
for occasions when inadvertent oversedation has occurred. Some
endoscopists routinely administer antagonists (intravenously
and/or intramuscularly) to reduce the recovery period, which
suggests mainly that their ‘routine’ dosage regime is excessive.
We use flumazenil extremely infrequently, but periodically administer
naloxone intramuscularly on reaching the cecum in a
patient who has requested or needed extra sedation. The patient
is then conveniently awake by the time the examination is fin-