The role of pethidine in sedation for colonoscopy

As sedation with a combination of benzodiazepines and opioids has been associated with an increased risk of serious cardiorespiratory events, it is rarely used in upper gastrointestinal endoscopy. The combination is, however, still commonly used in sedation for colonscopy and endoscopic retrograde cholangiopancreatography (ERCP). This study aimed to determine the benefits and disadvantages of adding pethidine to diazepam (Diazemuls) in the sedation for colonoscopic examinations.

Seventy-one consecutive patients attending for routine colonoscopy were randomized in a double-blind, placebo-controlled manner to sedation with Diazemuls alone or Diazemuls with pethidine. The colonoscopist was at liberty to administrate any dose of Diazemuls considered appropriate for the patient's age and size, following which the patient was given an injection of pethidine 50 mg or a placebo. Both the patient and the endoscopist were blind to whether pethidine or a placebo was used. Adequacy of sedation was assessed and oxygen saturation recorded throughout the procedure. Oxygen was administered if the oxygen saturation fell below 92%. Patient satisfaction with sedation and recall of the procedure was recorded, by questionnaire, one day after examination.

A total of 71 patients were entered into the trial. The two groups were similar with respect to age, sex, weight, alcohol intake, and state of health. An average of 18 mg of Diazemuls was given in the pethidine group and 19 mg in the placebo group. There was no statistically significant difference in the level of sedation obtained with the two regimens, although there was a tendency for the combination of Diazemuls with pethidine to give deeper sedation. Three patients were inadequately sedated with Diazemuls alone, requiring the code to be broken for pethidine to be given. Nine colonoscopies had to be abandoned due to patient intolerance in the group receiving Diazemuls, compared to five in the group receiving the combination regimen (p = 0.22). Twice as many patients receiving the combination of Diazemuls with pethidine required oxygen supplementation to maintain oxygen saturation during the procedure. This difference was highly statistically significant (p = 0.008). With the administration of supplemental oxygen, the average drop in oxygenation was similar in both groups. Satisfaction with sedation and recall for the procedure were similar in both groups.

Although the patients had no preference for either regime, there may be an advantage in using the combination of Diazemuls and pethidine, as there was a trend for this combination to be preferred by the colonoscopists. The combination of a benzodiazepine with an opiate should be used with caution, however, as there was a greater requirement for oxygen in the group sedated by Diazemuls and pethidine.