Practical Gastrointestinal Endoscopy

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CHAPTER 6
of local trauma. At-risk patients (see also pp. 28–29) (including
those with heart-valve replacements, cyanotic heart disease,
previous endocarditis or a recent aortic prosthesis) and immunosuppressed,
severely neutropenic or gravely ill patients (especially
immunocompromised infants) should have a suitable
antibiotic combination administered beforehand so as to give
therapeutic blood levels at the time of the procedure. A possible
adult regimen is: ampicillin 3·g orally 1·hour beforehand—or 1·g
in 2.5·mL 1% lidocaine (lignocaine) intramuscularly (IM) just
beforehand—plus another 0.5·g orally 6·hours later and gentamicin
120·mg IM 1·hour before (or IV just beforehand). Alternatively
give a single IV dose of gentamicin (80 ·mg) and ampicillin
(500·mg) before premedication. Vancomycin (20·mg/kg by slow
IV infusion over the 60·minutes prior to the procedure) can be
substituted for ampicillin in patients with a history of penicillin
sensitivity. Children under 10 years of age receive half the adult
dose of amoxicillin and gentamicin—2·mg/kg body weight. In
high-risk subjects it may be wise to continue antibiotics for up
to 24–48·hours.
EQUIPMENT
Colonoscopy room
Most units perform colonoscopies in undesignated endoscopy
rooms, because the only special requisite for colonoscopy is
good ventilation, to overcome the evidence of occasional poor
bowel preparation. In a few patients with particularly difficult
and looping colons it has in the past been helpful to have access
to X-ray facilities, particularly in teaching institutions. Threedimensional
(3D) imaging systems (see below), will perform the
same function without X-rays.
Colonoscopes
Colonoscopes are engineered similarly to upper gastrointestinal
endoscopes, but are longer, wider-diameter (for better twist
or torque control) and have a more flexible shaft. The bending
section of the colonoscope tip is also longer and so more gently
curved, to avoid impaction in acute bends, such as the splenic
flexure. Ideally, colonoscope control-body ergonomics and angulation
controls will in future be modified (with a tracker ball
or similar mechanism controlling power-steering facilities) so as
to make one-handed steering and activation of the different controls
and switches easier. Present control mechanisms are almost
unchanged from those of early gastrocameras and gastroscopes
and are far from ideal for the more finicky steering movements
required during colonoscopy. Video-colonoscopes have largely
eclipsed the use of fiber-optic instruments because they do not