0016-5107/92/3805-0564$03.00 GASTROINTESTINAL ENDOSCOPY Copyright © 1992 by the American Society for Gastrointestinal Endoscopy

Pain following colonoscopy: elimination with carbon dioxide G.

w. Stevenson, FRCP, FRCR, FRCP(C),

J. A. Wilson, MRCP J. Wilkinson, BA, G. Norman, PhD R. L. Goodacre, FRCP(C), MB, BS Hamilton, Ontario, Canada

Fifty-six patients have been examined in a prospective randomized study on the effects of air and carbon dioxide on post-procedural discomfort following colonoscopy. A significant reduction in post-procedural pain was observed at 6 hours (p = < 0.0005) and was still present the next day (p = 0.01). This was associated with a difference in the grading of flatus at 6 and 24 hours (p = < 0.0001 and < 0.05, respectively). An abdominal radiograph 1 hour after the procedure showed minimal gas in the CO 2 patients, while the patients who had air showed distention of large and small bowel (p = < 0.0001 and < 0.01, respectively). Seventeen of 29 patients who had air suffered post-procedural pain, compared with 2 of 27 of the CO2 patients. Fifty-seven percent of the patients who were given air had colonic diameters over 6 cm on a 1-hour post-colonoscopy radiograph and 18% over 10-cm diameter. Provision by equipment manufacturers of simple and safe devices for routine delivery of CO2 for lower gastrointestinal endoscopy is long overdue. (Gastrointest Endosc 1992;38:564-567)

A substantial minority of patients suffer from pain after colonoscopy or double contrast barium enema. We have previously reported a study on the use of CO 2 rather than air during double contrast barium enema, l in which we found a reduction in the postprocedural incidence of moderate to severe pain from 30% to 11 %, and others have also commented on the improved level of comfort following barium enema with CO 2 • 2, 3 It has already been shown that the use of carbon dioxide at colonoscopy reduces the amount of gas visible on plain abdominal radiographs 1 hour after the procedure,4 but the effect of this on reducing postprocedural pain has not been documented, and the use of CO 2 at colonoscopy has not become widespread, despite numerous publications on the increased safety that it can provide. 5- 11 There are currently no satisfactory commercial units available for administering CO 2 as the main Received January 30, 1992. For revision March 23, 1992. Accepted May 7,1992. From the Departments of Radiology, Gastroenterology, and Clinical Epidemiology, McMaster University, Hamilton, Ontario, Canada. Reprint requests: G. W. Stevenson, FRCP, Department of Radiology, Chedoke-McMaster Hospitals, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada.

564

distending agent at colonoscopy, despite requests to the manufacturers and leading editorials on the need for this. 12 We have conducted an experiment to discover whether, and to what extent, the use of CO 2 rather than air reduces the discomfort that patients experience after colonoscopy. METHODS

The departmental booking desk used a printed list of randomized numbers to allocate sequential colonoscopy patients to have their examination with either air or CO 2 • Both types of patients could be examined on any given list. Patients who had colonic resections were excluded, and there were no children in the study. Polypectomy was to be performed as indicated during the procedures. The air button on the colonoscope was covered with a metal shield, and the CO 2 button was used for all gas infusion. Air and CO 2 cylinders were connected to the colonoscope's CO 2 input nipple with a technologist switching the tap to A or B according to the preallocated selection of air or CO 2 , The allocation of A and B was also changed by the technologist from time to time so that the endoscopist would not learn whether A or B represented air. Standard sedation was used according to the endoscopist's preference, with most patients receiving 100 mg of meperidine and 10 mg of Diazemuls"', but less if they were small, old, or frail. GASTROINTESTINAL ENDOSCOPY

One hour after the examination a supine abdominal radiograph was taken. Patients were then asked by a research assistant to score, on five point scales (as shown in Tables 1 to 3), any pain that they had felt during the examination; if they had passed gas after the colonoscopy, and if so, how much; and some other questions about level of stress, what they most liked or disliked about the examination, and how willing they would be to have the examination again. The research assistant telephoned the patient at home to administer a further questionnaire 6 hours after the procedure and again 24 hours after the procedure. The same questions were asked and, in addition, if pain was experienced after the examination, how soon it was felt, what kind of pain it was, how long did it persist, and how severe it was. The radiographs were kept and, after the study was complete, the films were shuffled and read by a gastrointestinal radiologist. The amounts of gas in the colon and in the small bowel were recorded, using five point scales: for the colon, of trace, minimal, whole colon filled but not distended, colonic diameter >6 em, and colon diameter>10 em; and for the small bowel, of trace, mild, moderate, severe, and extreme.

corded at the 24-hour interview (p = < 0.01) (Table 1).

An additional analysis comparing the frequencies of grade 0 (no pain) responses to the sum of all other responses yielded similar findings; there was no significant difference between air and CO 2 during the procedure, and a highly significant difference at 6 and 24 hours post-procedure. Of the CO 2 patients, two had post-procedural pain, one mild colic, and one who had no pain at 6 hours had severe continuous pain at 24 hours, and a chart diagnosis of anxiety, depression, and agoraphobia. Of 29 air patients with complete data, 17 (57%) had post-procedural pain, of whom 14 recorded colic at the 6-hour interview. Three more had pain of more than 12 hours' duration by the 24-hour interview (one colic and two continuous pain). The duration of the pain was longer than expected: six patients >12 hours, three 6 to 8 hours, four 4 to 5 hours, and four 1 to 3 hours. Eighteen percent of the air patients experienced pain that was more than mild after leaving the department.

RESULTS

Fifty-six patients were recruited into the study and all who were recruited completed the study. Fortyeight patients were examined by one endoscopist. The patients were all booked for elective colonoscopy, and there were none with acute major bleeding or severe acute inflammatory bowel disease. Pain

The use of CO 2 rather than air had no effect on the amount of pain experienced during the examination. There was a statistically significant effect on reducing post-procedural pain at the 6-hour interview (p = < 0.0005), and this was still apparent overnight as re-

Table 1. Results of patient questionnaire administered 1 hour after, 6 hours after, and 24 hours after colonoscopy, documenting the patient's perception of pain experienced during the procedure, and in the few hours before the two telephone calls

Passing gas

The difference in gas passed was not surpnsmg since CO 2 is known to be absorbed from the colon 160 times faster than nitrogen,13 but the duration of the difference was a surprise. Table 2 shows that although the CO 2 patients gradually started to pass gas again, there is still a statistically significant difference in the amount of gas passed during the 12 hours leading up to the final 24-hour interview. At 1 hour, 46% of the air patients and 92% of the CO 2 patients reported no gas passed, perhaps because of our standard practice of removing air from the rectum and sigmoid at the end of the procedure. An analysis comparing the frequencies of grade 0 (no gas passed responses) to all other responses again gave similar results with no Table 2. Patient responses to questions about the amount of flatus at 1, 6 and 24 hours after colonoscopy with air or with CO2

% Passing gas

Percentage of patients with pain Grade

None, 0 Mild,l Moderate, 2 Severe, 3 Extreme, 4

During

6 hours post

24 hours post

Air

CO,

Air

CO,

Air

CO,

26 22 22 19 11

17 25 21 29 8

50 32 7 11

97 3

56 24

95

12 5

x' = 1.27

x' = 17.6

x' = 12.35

NS

p < 0.0005

p 0.01

VOLUME 38, NO. 5, 1992

Grade

None, 0 A little, 1 Moderate, 2 A lot, 3 Extreme, 4

At 1 hour

By 24 hours

By 6 hours

Air

CO,

Air

CO,

Air

CO,

46 25 21 4 4

92 8

4 15 42 31 8

83 8 4 4

12 12 28 40

60 60 5 10 4

x' = 13.4 P =

Pain following colonoscopy: elimination with carbon dioxide.

Fifty-six patients have been examined in a prospective randomized study on the effects of air and carbon dioxide on post-procedural discomfort followi...
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