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78

Chapter 6

Incolonoscopy, opioids are commonlyused incombinationwithabenzodiazepine to induce

amnesia. We did not consider this mandatory for CT colonography as this combination

leads to a greater respiratory depressant effect than opioids only. The benzodiazepine-

induced drowsiness may complicate the CT colonography procedure and recovery facilities

may be required.

A number of limitations have to be acknowledged. The dizziness caused by alfentanil may

have partly affected the double blind character of the trial. We had anticipated this however;

to our knowledge, no substance is available that causes dizziness in an equal number of

patients as alfentanil and that does not affect the outcomes. We chose to use 0.9% saline

solution for the placebo group because it was the solvent for alfentanil and the viscosity and

colour was similar to that of alfentanil. Importantly, patients were not aware that dizziness

would be more likely related to alfentanil administration than placebo. Pressure is higher in

prone position.

41

Therefore, pain was assessed in prone scan acquisition position only as we

wanted to limit the number of questions. The time of prone scan acquisition differed some

minutes between studies with and without intravenous contrast medium. The influence

of prone score on the maximum pain was negligible as these were much lower compared

with left decubitus. We chose to use an 11-point numeric rating scale, which is a commonly

used scale.

26,44

The visual analogue scale

44

is also commonly used, however this scale is less

practical during colonic insufflation on a narrow table, while having colonic cramps and

being monitored. Additionally, we have experience with the 11-point numeric rating scale

during CT colonography. For the Aldrete score we chose as reference values blood pressure

and heart rate measurements, recorded 1½ minute after injection of the spasmolytic agent.

Most patients received butylscopolamine bromide, which increases heart rate.

35

As the

effect of the spasmolytic decreases over time, heart rate also decreases. Furthermore, most

patients are nervous at the beginning of a medical procedure and calm down in the course

of the procedure. Both factors might have influenced Aldrete score negatively, although

all patients had a normal heart rate and blood pressure after the procedure. Despite the

fact the side effects of alfentanil were of minor clinical relevance and the benefit-risk ratio

seems to favour alfentanil, a safety profile cannot be made based on 45 patients. Although

other studies also have shown safe use of a single bolus low-dose alfentanil,

43,45

more data

on patient safety is warranted.

When alfentanil is used, it is important to realise that monitoring and airway intervention

equipment, and sufficient knowledge about the pharmacology of opioids and airway

interventions should be present. This means that the attendance of a physician is required.

For institutions where a technician is performing the CT colonography procedure,

adjustments will have to be made in the procedure. All patients receiving intravenous

alfentanil require an intravenous cannula, so that emergency medication can be given.

The above-mentioned issues may lead to an increase in costs. Furthermore, when using