No one would doubt that there are tremendous variations in the way that endoscopic sedation is practiced around the world. For instance, in the United States almost all endoscopists use intravenous conscious sedation for colonoscopy, and most of the time this entails a combination of a benzodiazepine with a narcotic. However, the same procedure in France may well involve general anesthesia in 83% of the cases,1Greff M Colorectal cancer screening in France: guidelines and professional reality [editorial].Endoscopy. 1999; 31: 471Crossref PubMed Scopus (6) Google Scholar whereas another study from Germany reported that 95% of patients did not require any form of sedation whatsoever for colonoscopy.2Eckardt VF Kanzler G Schmitt T Eckardt AJ Bernhard G Complications and adverse effects of colonoscopy with selective sedation.Gastrointest Endosc. 1999; 49: 560-565Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar Marked worldwide variations also exist in the use of sedation for EGD, which in the United States is routinely performed with intravenous conscious sedation. The “Perspectives” section of Gastrointestinal Endoscopy in December 1999 reported on questionnaires that had been sent to all members of the International Editorial Board of the Journal inquiring about the use of sedation for EGD. In the Asian zone, only 44% of the respondents used sedation routinely for EGD, and 53% did not believe that sedation was needed at all for patient comfort.3Perspectives Worldwide use of sedation and analgesia for upper intestinal endoscopy.Gastrointest Endosc. 1999; 50: 888-891PubMed Google Scholar In fact, even the same expert endoscopist may use different levels of sedation for the same procedure depending on where the expert is “performing” around the world.What makes it even more confusing is that alternative forms of, or adjuncts to, conventional endoscopic sedation also exist, such as nitrous oxide,4Forbes GM Collins BJ Nitrous oxide for colonoscopy: a randomized controlled study.Gastrointest Endosc. 2000; 51: 271-277Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar, 5Notini-Gudmarsson AK Dolk A Jakobsson J Johansson C Nitrous oxide: a valuable alternative for pain relief and sedation during routine colonoscopy.Endoscopy. 1996; 28: 283-287Crossref PubMed Scopus (45) Google Scholar relaxation music,6Bampton P Draper B Effect of relaxation music on patient tolerance of gastrointestinal endoscopic procedures.J Clin Gastroenterol. 1997; 25: 343-345Crossref PubMed Scopus (53) Google Scholar hypnotherapy,7Zimmerman J Hypnotic technique for sedation of patients during upper gastrointestinal endoscopy.Am J Clin Hypn. 1998; 40: 284-287Crossref PubMed Scopus (7) Google Scholar acupuncture,8Cahn AM Carayon P Hill C Flamant R Acupuncture in gastroscopy.Lancet. 1978; 1: 182-183Abstract PubMed Scopus (32) Google Scholar, 9Li CK Nanck M Loser C Folsch UR Creutzfeldt W Acupuncture for lessening pain during colonoscopy.Dt Sch Med Wochenschr. 1991; 116: 367-370Crossref PubMed Scopus (17) Google Scholar and virtual vision.10Kozarek RA Raltz SL Brandabur JJ Bredfeldt JE Patterson DJ Wolfsen HW et al.Virtual vision for diagnostic and therapeutic esophagogastroduodenoscopy and colonoscopy.Gastrointest Endosc. 1997; 46: 58-60Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar An investigational form of sedation for GI endoscopy that has attracted a great deal of interest is the use of intravenous propofol. Propofol (2,6-diisopropylphenol) is a substituted derivative of phenol and is the most recent intravenous anesthetic to be introduced into clinical practice.11Reves JG Glass PSA Lubarsky DA Nonbarbiturate intravenous anesthetics.in: 5th ed. Anesthesia. Churchill Livingstone, Philadelphia2000: 228-271Google Scholar In the United States it is formulated as an isotonic milky white, oil-in-water emulsion containing 10 mg/mL of propofol, together with soybean oil, glycerol, egg lecithin, and disodium edetate (Diprivan, AstraZeneca Pharmaceuticals LP, Wilmington, Del.). Propofol is primarily a hypnotic compound that is thought to act centrally by facilitation of γ-aminobutyric acid activity in the brain. It has an extremely rapid onset of action, producing unconsciousness within seconds, and a short half-life that permits fast recovery from anesthesia. Propofol is administered intravenously and has to be continuously titrated to maintain the desired effect. This is generally accomplished by the use of a continuous intravenous infusion, although intermittent bolus technique can also be used. Propofol has a relatively narrow therapeutic range and patients can easily cross from conscious to deep sedation. It has no analgesic properties and so a narcotic must be added during painful procedures. It has a variable amnestic effect (depending on the dose) and a benzodiazepine is frequently coadministered. When used alone, propofol is both a cardiovascular and respiratory depressant drug. However, concomitant use with a narcotic or a benzodiazepine is associated with added risks because of enhanced respiratory depression that may lead to unplanned deep sedation and general anesthesia. Unlike opioids and benzodiazepines, propofol has no pharmacologic reversal agent. Nonetheless, this is not as worrisome as it may seem at first, given its short half-life and rapid reversal of anesthesia with discontinuation of the drug. The current uses of propofol approved by the United States Food and Drug Administration (FDA) are as follows: the induction and maintenance of general anesthesia, initiation and maintenance of monitored anesthesia care sedation, and initiation and maintenance of intensive care unit sedation in intubated, mechanically ventilated patients. As such, the manufacturer currently recommends that propofol be administered only by persons trained in the administration of general anesthesia who are not involved in the conduct of the surgical/diagnostic procedure. For intensive care unit patients, the manufacturer currently recommends that propofol be administered only by persons skilled in the management of critically ill patients and trained in cardiovascular resuscitation and airway management.12Physicians' Desk Reference. Diprivan 1%. 55th ed. Medical Economics, Montvale (NJ)2001: 620-626Google Scholar This generally means that propofol should only be used by anesthetists and intensivists (at least in the United States). Its use by other types of medical personnel for the purposes of providing conscious sedation during GI endoscopy is off-label and remains controversial.In this issue of Gastrointestinal Endoscopy, there are 3 original articles from institutions outside of the United States describing the “safe” use of propofol for providing endoscopic sedation in colonoscopy13Ng J-M Kong C-F Nyam D Patient-controlled sedation with propofol for colonoscopy.Gastrointest Endosc. 2001; 54: 8-13Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar, 14Külling D Fantin AC Biro P Bauerfeind P Fried M Safer colonoscopy with patient-controlled analgo-sedation using propofol and alfentanil.Gastrointest Endosc. 2001; 54: 1-7Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar and ERCP.15Gillham MJ Hutchinson RC Carter R Kenny GNC Patient-maintained sedation for endoscopic retrograde cholangiopancreatography using target-controlled infusion of propofol: a pilot study.Gastrointest Endosc. 2001; 54: 14-17Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar The reader should note that in none of these 3 articles was documentation made of the preprocedure airway assessment, which is a critical aspect of safe sedation practice.16Graber RG Propofol in the endoscopy suite: an anesthesiologist's perspective [editorial].Gastrointest Endosc. 1999; 49: 803-806Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar Ng et al.13Ng J-M Kong C-F Nyam D Patient-controlled sedation with propofol for colonoscopy.Gastrointest Endosc. 2001; 54: 8-13Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar from Singapore randomized 88 adult patients who were scheduled for elective, outpatient (mainly diagnostic) colonoscopy, to sedation with either intravenous bolus midazolam or intravenous propofol administered with patient-controlled sedation (PCS) technique. An anesthetist was present in the endoscopy room throughout the procedure. The investigators concluded that “PCS with propofol is effective and results in high patient satisfaction and faster discharge.” Of concern is that one patient (aged 81 years) reached a deepest sedation score of 6 on a 6-point sedation scale, which indicates that this patient did not respond to mild physical stimulation. Rather than conscious sedation, a sedation score of 5 or 6 would indicate deep sedation, which is clearly an inappropriate level of sedation for performing diagnostic colonoscopy. The zero lockout interval on the PCS pump may have contributed to this deeper level of sedation because the patient could potentially request multiple doses of propofol before the first dose takes effect. The reader should also take note that conscious sedation (or as it is now more correctly termed, moderate sedation/analgesia) has been defined as “A drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate. Cardiovascular function is usually maintained.”17Care of patients (TX): standards, intent statements, and examples for sedation and anesthesia care.in: Comprehensive accreditation manual for hospitals (CAMH): the official handbook Update 3. Joint Commission Resources, Inc, Oakbrook Terrace (IL)August 2000: 15-17Google Scholar It is important to reiterate the investigators' comments that the patients in this study were relatively young and healthy (mean age of 54 years in the propofol group with American Society of Anesthesiologists [ASA] physical status classification of I or II). Thus the findings of this study may not pertain to older, sicker hospitalized patients or those needing endoscopic intervention. Furthermore, the investigators have chosen to compare intravenous bolus administration of midazolam (their standard sedation method for colonoscopy) with PCS-administered propofol. It is uncertain whether the apparent differences in the results between the two patient groups were due to different anesthetic medications (midazolam vs. propofol) or to the different methods of administration (conventional versus PCS). This study would have been stronger if the investigators had chosen to compare a single variable. In addition, most endoscopists in the United States would have used a combination of a benzodiazepine together with a narcotic agent rather than a benzodiazepine alone. This could certainly have affected the study results pertaining to patient cooperation, level of comfort, and surgeon satisfaction.The second original article on the use of propofol in colonoscopy, which is by Külling et al.14Külling D Fantin AC Biro P Bauerfeind P Fried M Safer colonoscopy with patient-controlled analgo-sedation using propofol and alfentanil.Gastrointest Endosc. 2001; 54: 1-7Abstract Full Text Full Text PDF PubMed Scopus (112) Google Scholar from Switzerland, is a better-designed study overall, and it addresses some of my prior concerns with the article by Ng et al.13Ng J-M Kong C-F Nyam D Patient-controlled sedation with propofol for colonoscopy.Gastrointest Endosc. 2001; 54: 8-13Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar but raises others. In this study, 150 consecutive patients scheduled for elective, outpatient colonoscopy were randomly assigned to 1 of 3 medication groups. Group I patients were given propofol and alfentanil by using a PCS system with a zero lockout interval; Group II patients were given the same two medications but by continuous intravenous infusion and additional boluses were given, as needed; Group III patients were given an initial intravenous bolus of midazolam and meperidine followed by additional boluses of the same medications, as needed. Similar to the study by Ng et al.,13Ng J-M Kong C-F Nyam D Patient-controlled sedation with propofol for colonoscopy.Gastrointest Endosc. 2001; 54: 8-13Abstract Full Text Full Text PDF PubMed Scopus (109) Google Scholar the patients enrolled in this study were relatively young and healthy (median age of 54 years with ASA physical status classification of I or II). An anesthetist was not physically present in the endoscopy room during the procedure; instead the investigators tell us that anesthesia support was available on-call. The use of propofol plus alfentanil (a short-acting intravenous narcotic) combination, is theoretically much more risky because of enhanced respiratory depression. Nonetheless, they tell us that no serious cardiorespiratory complications occurred in any of the 3 groups. This may have been because 31% of the patient attempts to obtain additional boluses of propofol and alfentanil in Group I (PCS) were unsuccessful. One possible explanation is that this particular PCS system had a slow drug delivery rate, and therefore this may have functioned as a surrogate lockout mechanism. The investigators also informed us that during colonoscopy, there were no differences between the 3 groups with respect to changes in mean arterial blood pressure or oxygen saturation. Although transcutaneous pCO2 increased to a lesser degree in Group I (PCS) compared with Groups II and III, this finding did not translate to better patient safety (at least in this relatively small study). Because none of the patients had any serious cardiorespiratory complications, this study does not prove that one sedation regimen is safer than the other. In terms of recovery from sedation, as assessed by the investigators by using the Trieger dot-joining test, the only differences in recovery between the 3 groups were noted at 45 and 90 minutes after the procedure in favor of Group I (PCS) over Group III (midazolam/meperidine). It is difficult to know what this means in actual clinical practice because they do not tell us whether there were any differences in the discharge times of the patients from the endoscopy unit. An average patient discharge time (with an escort) of 45 minutes after colonoscopy would be similar to our current discharge times when using conventional intravenous benzodiazepine and narcotic sedation in our endoscopy unit. During the recovery period, the investigators also found a greater decrease in mean arterial blood pressure in Group III (midazolam/meperidine) than in Group I (PCS), but they do not tell us whether this affected actual patient management. However, despite less amnesia, the patients in Group I (PCS) were more satisfied with their overall degree of sedation than those in the other 2 groups.The third original article, which is by Gillham et al.15Gillham MJ Hutchinson RC Carter R Kenny GNC Patient-maintained sedation for endoscopic retrograde cholangiopancreatography using target-controlled infusion of propofol: a pilot study.Gastrointest Endosc. 2001; 54: 14-17Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar from the United Kingdom, is a small (n = 20), uncontrolled pilot study that examined the use of propofol for ERCP with a target-controlled infusion (TCI) of propofol, coupled with PCS capability. TCI is a relatively new drug delivery system designed for intravenous anesthetic agents, with which the anesthetist targets a plasma drug concentration in order to achieve a predetermined effect.18Billard V Cazalaa JB Sevin F Viviand X Target-controlled intravenous anesthesia.Ann Fr Anesth Reanim. 1997; 16: 250-273Crossref PubMed Scopus (28) Google Scholar A microprocessor then commands the infusion device based on known pharmacokinetic data. In this study, the pharmacokinetic calculations were based on the patients' age and weight. This TCI model would allow one to reach some consistent target blood concentration of propofol. Coupling the TCI system with PCS capability allowed the patients in this study to supplement with propofol, based on their own requirements. Is a TCI-based system better and safer for patients than more conventional approaches? It is too early to tell. However, it is known that there is individual variability in the drug levels needed to achieve certain desired (or undesired) effects. Consequently, the right target dose in one patient may be an overdose in another. It would seem too simplistic to base the calculations of target blood levels solely on patient age and weight. In the end it may be safer to carefully titrate the drug to the response of each individual patient. In this article by Gillham et al.,15Gillham MJ Hutchinson RC Carter R Kenny GNC Patient-maintained sedation for endoscopic retrograde cholangiopancreatography using target-controlled infusion of propofol: a pilot study.Gastrointest Endosc. 2001; 54: 14-17Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar the investigators concluded that TCI-administered propofol with PCS was safe and fully effective in 16 patients. However, it is important for the reader to note that in 4 patients (20%) the TCI system failed, and sedation overdoses occurred in another 4 patients (25%) of the remaining 16. (Fortunately, an anesthetist was present at all times and these 4 patients recovered without complications.) Thus, in 8 patients out of 20 (40%), the TCI system either failed to deliver adequate sedation or there was oversedation and the patients crossed into the realm of deep sedation. In addition, this study was unblinded and there was no patient control group. Furthermore, the investigators allowed the patients up to 20 minutes to titrate themselves to an adequate level of sedation before the ERCP was even started. During this time, the patients would require an appropriate level of monitoring for adverse effects from the propofol. How much would this add to the total time and cost of the procedure? Consequently, for all of these reasons, I would currently consider TCI-based systems as a research tool that is not ready to be used in everyday clinical practice.What is the major impetus for all of this research into endoscopic sedation? Are patients dissatisfied with the current status of endoscopic sedation in the United States? Probably not. Are serious cardiopulmonary complication and death rates from endoscopic sedation unacceptably high in the United States (estimated at 54 and 3 per 10,000 cases respectively, in one retrospective study)?19Arrowsmith JB Gerstman BB Fleischer DE Benjamin SB Results from the American Society for Gastrointestinal Endoscopy/U.S. Food and Drug Administration collaborative study on complication rates and drug use during gastrointestinal endoscopy.Gastrointest Endosc. 1991; 37: 421-427Abstract Full Text PDF PubMed Scopus (456) Google Scholar Perhaps, and no one would argue that everyone should fervently strive to reduce complication rates to the absolute minimum. Are endoscopy units in the United States under increasing pressure to perform more procedures, reduce costs, and to have shorter patient turnaround time? Definitely yes. Sedation is the major factor that keeps the patient waiting in the recovery area after the completion of any endoscopic procedure. Any shortening of the time to discharge could potentially reduce costs and allow more procedures to be performed. For instance, there are studies examining the routine use of pharmacologic reversal agents after endoscopic sedation to reduce time to discharge.20Wille RT Chaffee BW Ryan ML Elta GH Walter V Barnett JL Pharmacoeconomic evaluation of flumazenil for routine outpatient EGD.Gastrointest Endosc. 2000; 51: 282-287Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar, 21Chang AC Solinger MA Yang DT Chen YK Impact of flumazenil on recovery after outpatient endoscopy: a placebo-controlled trial.Gastrointest Endosc. 1999; 49: 573-579Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar Of course, the ultimate extent of this approach would be sedationless endoscopy: this is an evolving area and much current research focuses on this topic.22Sorbi D Gostout CJ Henry J Lindor KD Unsedated small-caliber esophagogastroduodenoscopy (EGD) versus conventional EGD: a comparative study.Gastroenterology. 1999; 117: 1301-1307Abstract Full Text Full Text PDF PubMed Scopus (99) Google Scholar, 23Thiis-Evensen E Hoff GS Sauar J Vatn MH Patient tolerance of colonoscopy without sedation during screening examination for colorectal polyps.Gastrointest Endosc. 2000; 52: 606-610Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar The reader should also note that cost analysis of endoscopic sedation is highly complex, and a detailed analysis is beyond the scope of this editorial. Nevertheless, many variables are involved, some of which may be institution and payor-mix specific. It is thus difficult (almost impossible) to provide endoscopic sedation guidelines that will be universally effective at reducing the actual cost of performing endoscopy.In the United States, the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has issued updated guidelines stating that practitioners who are credentialed to administer moderate sedation (formerly known as conscious sedation) must also be qualified to rescue patients from deep sedation, be competent at managing a compromised airway, and be able to provide adequate oxygenation and ventilation.17Care of patients (TX): standards, intent statements, and examples for sedation and anesthesia care.in: Comprehensive accreditation manual for hospitals (CAMH): the official handbook Update 3. Joint Commission Resources, Inc, Oakbrook Terrace (IL)August 2000: 15-17Google Scholar What does this really mean? Is Advanced Cardiac Life Support certification adequate? Probably, but is it adequate for the use of propofol? Probably not. At most institutions in the United States, propofol (and alfentanil) have traditionally been considered general anesthetics. Thus, one would have to have general anesthesia privileges to administer them to unventilated patients. If an anesthetist (or an additional qualified individual) is needed for the administration of propofol and for monitoring the patient, how does this impact the total cost of the procedure? Perhaps with more time and research, propofol will eventually be found to be safe for use by nonanesthetists for the purpose of GI endoscopic sedation. For instance, there has been interesting recent research on the use of capnography to adjust the rate of propofol infusion in real-time by detecting apneic episodes during the performance of advanced upper endoscopic procedures (like ERCP).24Vargo JJ Zuccaro Jr, G Dumot JA Shay SS Conwell DL Morrow B Gastroenterologist-administered propofol for therapeutic upper endoscopy with graphic assessment of respiratory activity: a case series.Gastrointest Endosc. 2000; 52: 250-255Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar This may assist in preventing the serious occurrence of prolonged apneic episodes in patients receiving propofol sedation, particularly during ERCP. (In recent studies, manual ventilation was required in two patients for 6 to 8 minutes.)25Jung M Hofmann C Kiesslich R Brackertz A Improved sedation in diagnostic and therapeutic ERCP: propofol is an alternative to midazolam.Endoscopy. 2000; 32: 233-238Crossref PubMed Scopus (155) Google Scholar, 26Wehrmann T Kokabpick S Lembcke B Caspary WF Seifert H Efficacy and safety of intravenous propofol sedation during routine ERCP: a prospective, controlled study.Gastrointest Endosc. 1999; 49: 677-683Abstract Full Text Full Text PDF PubMed Scopus (240) Google Scholar It is possible that the evaluation of propofol for use in endoscopic sedation may be following the “irrational pattern of drug evaluation” as outlined in a previous editorial in the Journal by Graber.16Graber RG Propofol in the endoscopy suite: an anesthesiologist's perspective [editorial].Gastrointest Endosc. 1999; 49: 803-806Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar It is far too early to tell. With present data, I believe that propofol should not be used by nonanesthetists for the purpose of GI endoscopic sedation unless it is carefully done as part of an Institutional Review Board-approved research study.Practice guidelines for sedation and analgesia by nonanesthesiologists have been set forth by the American Society of Anesthesiologists and were published in 1996.27Anesthesiology. 1996; 84: 459-471Crossref PubMed Scopus (462) Google Scholar These guidelines have been officially endorsed by the Governing Board of the American Society for Gastrointestinal Endoscopy. However, despite these guidelines, it is clear that the published data on endoscopic sedation are all confusing, even contradictory. What then should the practicing endoscopist do? Should the endoscopist order the all-you-can-eat buffet, combination set menu, select from the à la carte menu, or let the patient go hungry? I believe that the practicing endoscopist will have to critically assess various patient and procedural-related factors before reaching a decision on what specific type of endoscopic sedation (if any) to use. These factors should include the following: a careful preprocedure medical (and brief psychological) assessment of the patient; an inquiry as to whether there were any prior anesthetic difficulties; an appropriate assessment of the airway; a recognition of the specific type of endoscopic procedure being considered, the degree of pain associated with it, and the length of time it will take to complete; a consideration of the anticipated findings and the possibility for endoscopic therapy; and an assessment of patient expectations together with patient education about the intended procedure. Above all, it is important for the endoscopist to be thoroughly familiar with whatever type of sedation is chosen and to be able to successfully rescue patients from unintentional oversedation. In the future, the best approach to ordering endoscopic sedation may be to ask the waiter for the à la carte menu, s'il vous plaît. No one would doubt that there are tremendous variations in the way that endoscopic sedation is practiced around the world. For instance, in the United States almost all endoscopists use intravenous conscious sedation for colonoscopy, and most of the time this entails a combination of a benzodiazepine with a narcotic. However, the same procedure in France may well involve general anesthesia in 83% of the cases,1Greff M Colorectal cancer screening in France: guidelines and professional reality [editorial].Endoscopy. 1999; 31: 471Crossref PubMed Scopus (6) Google Scholar whereas another study from Germany reported that 95% of patients did not require any form of sedation whatsoever for colonoscopy.2Eckardt VF Kanzler G Schmitt T Eckardt AJ Bernhard G Complications and adverse effects of colonoscopy with selective sedation.Gastrointest Endosc. 1999; 49: 560-565Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar Marked worldwide variations also exist in the use of sedation for EGD, which in the United States is routinely performed with intravenous conscious sedation. The “Perspectives” section of Gastrointestinal Endoscopy in December 1999 reported on questionnaires that had been sent to all members of the International Editorial Board of the Journal inquiring about the use of sedation for EGD. In the Asian zone, only 44% of the respondents used sedation routinely for EGD, and 53% did not believe that sedation was needed at all for patient comfort.3Perspectives Worldwide use of sedation and analgesia for upper intestinal endoscopy.Gastrointest Endosc. 1999; 50: 888-891PubMed Google Scholar In fact, even the same expert endoscopist may use different levels of sedation for the same procedure depending on where the expert is “performing” around the world. What makes it even more confusing is that alternative forms of, or adjuncts to, conventional endoscopic sedation also exist, such as nitrous oxide,4Forbes GM Collins BJ Nitrous oxide for colonoscopy: a randomized controlled study.Gastrointest Endosc. 2000; 51: 271-277Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar, 5Notini-Gudmarsson AK Dolk A Jakobsson J Johansson C Nitrous oxide: a valuable alternative for pain relief and sedation during routine colonoscopy.Endoscopy. 1996; 28: 283-287Crossref PubMed Scopus (45) Google Scholar relaxation music,6Bampton P Draper B Effect of relaxation music on patient tolerance of gastrointestinal endoscopic procedures.J Clin Gastroenterol. 1997; 25: 343-345Crossref PubMed Scopus (53) Google Scholar hypnotherapy,7Zimmerman J Hypnotic technique for sedation of patients during upper gastrointestinal endoscopy.Am J Clin Hypn. 1998; 40: 284-287Crossref PubMed Scopus (7) Google Scholar acupuncture,8Cahn AM Carayon P Hill C Flamant R Acupuncture in gastroscopy.Lancet. 1978; 1: 182-183Abstract PubMed Scopus (32) Google Scholar, 9Li CK Nanck M Loser C Folsch UR Creutzfeldt W Acupuncture for lessening pain during colonoscopy.Dt Sch Med Wochenschr. 1991; 116: 367-370Crossref PubMed Scopus (17) Google Scholar and virtual vision.10Kozarek RA Raltz SL Brandabur JJ Bredfeldt JE Patterson DJ Wolfsen HW et al.Virtual vision for diagnostic and therapeutic esophagogastroduodenoscopy and colonoscopy.Gastrointest Endosc. 1997; 46: 58-60Abstract Full Text Full Text PDF PubMed Scopus (3) Google Scholar An investigational form of sedation for GI endoscopy that has attracted a great deal of interest is the use of intravenous propof