Dose-related adverse cardiopulmonary events associated with conventional intravenous sedation accounted for most of the complications during colonoscopy. This thesis described clinical trials to look for a safer sedative method (patient-controlled sedation, PCS) and possible ways to reduce the need of sedative medications during colonoscopy. / One hundred elderly patients (over 65 years old) were randomised to receive either PCS (a combination of propofol and alfentanil) or conventional intravenous sedation (a combination of diazemuls and pethidine) during colonoscopy. The patients in the PCS group experienced significant less adverse cardiopulmonary events. Other parameters, however, were similar in both groups. The use of PCS for colonoscopy thus appeared safer when compared to conventional intravenous sedation. In a subsequent large scale prospective study (N=500), twenty-two percent of the patients were unwilling to use PCS for colonoscopy; and that the younger patient (<50 years old), female gender, a higher mean dose of sedatives consumed, a lower satisfaction score expressed, and the presence of delayed side effects were independent factors identified to predict the unwillingness of using PCS for colonoscopy. / The use of adjunct sedation such as audiovisual distraction was proposed as a way to reduce sedative requirements during colonoscopy. By using PCS as a quantitative outcome measure, audio distraction (in the form of music) was found to be able to decrease sedative requirements by 28%. The use of visual distraction alone, however, failed to decrease the sedative requirements; but nonetheless improved the acceptance of colonoscopy. Finally, a randomised comparison on the use of conventional endoscopes with that of the newly available variable stiffness endoscope used for colonoscopy was performed; and found that the latter was associated with less procedure-related pain and hence the consumption of sedative medications. / To conclude, PCS for colonoscopy was safe, feasible and acceptable. The use of adjunct sedation (audio distraction) and the newly available variable stiffness endoscope might decrease the need of sedative medications during the procedure. / Lee Wai Hung, Danny. / "September 2005." / Adviser: S. C. S. Chung. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3694. / Thesis (M.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 256-280). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / School code: 1307.