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Journal of Clinical Anesthesia 2007; 19:397-404

Understanding modes of moderate sedation during gastrointestinal procedures : a current review of the literature. Journal of Clinical Anesthesia 2007; 19:397-404. 1. Introduction Colorectal cancer - Substantial morbidity and mortality

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Journal of Clinical Anesthesia 2007; 19:397-404

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  1. Understanding modes of moderate sedation during gastrointestinal procedures : a current review of the literature Journal of Clinical Anesthesia 2007; 19:397-404

  2. 1. Introduction • Colorectal cancer - Substantial morbidity and mortality - Second leading cause of cancer-related mortality in the United States - 5-year survival rate of only 62% • To improve survival, early detection is essential - Wide spread screening -> the most effective method for early detection - Screening -> cost-effective -> potential to improve patient outcomes

  3. In 2002, 14.2 million colonoscopies were performed in the U.S. • Most of these procedures are performed with sedation in patients who are at average risk of complications associated with endoscopic sedation - Risk stratification for endoscopy is not well defined • Sedation is routinely provided to patients during colonoscopy and is considered the standard of practice in the U.S., where the performance of unsedated colonoscopy is highly unusual

  4. Although endoscopic procedures can be performed without sedation, results of two studies showed that 16% to 56% of such procedures are terminated because of pain • An important goal of colonoscopy is cecal intubation - Without adequate sedation the endoscope is less likely to reach that distance, increasing the possibility of missing adenomatous polyps or tumors • Thus, moderate sedation with or without supplemental analgesia is not only the standard of practice in the U.S. for patients undergoing endoscopic procedures, it is often necessary for successful completion of the procedure

  5. Current options for sedation - Benzodiazepines (eg, midazolam, diazepam) - Propofol - Opioids (eg, fentanyl, meperidine) - Ketamine - Inhaled anesthetics (eg,nitrous oxide) • Dexmedetomidine - Side effects (hemodynamic instability, complicated administration, and prolonged recovery)

  6. Current guidelines of the ASA 1) The person responsible for monitoring patients who undergo sedation - Be trained in recognizing complications associated with sedation/analgesia - Be competent to rescue the patient from a deeper level of sedation 2) Significant sedation-related risk factors (eg, potentially difficult airway, severe obstructive pulmonary disease, coronary artery disease, congestive heart failure, sleep apnea) Deep sedation is necessary to obtain adequate procedural conditions - It is recommended that an anesthesiologist be consulted

  7. 2. Safety of current sedation regimens for colonoscopy • Most endoscopic procedures occur at a moderate level of sedation • The goal while preserving cardiopulmonary function - To relieve anxiety, discomfort, and pain - To provide amnesia • Clinical practice guidelines call for the careful titration of sedative medications using small incremental doses

  8. Data from the American Society for Gastrointestinal Endoscopy's computer-based management system was used to review more than 21,000 GI endoscopies in 1988, performed primarily with sedation with either midazolam or diazepam - The overall complication rate was 13.5 events per 1,000 procedures - The rate of serious cardiacorrespiratory complications was 5.4 per 1000 - Death was reported in 0.3 per 1,000 procedures - There was no significant difference in the rate of complications between patients receiving midazolam and those receiving diazepam

  9. More recent data evaluating the safety and efficacy of meperidine and diazepam or meperidine and midazolam, when used for moderate sedation during upper and lower GI endoscopic procedures performed overa1 2-year period, - Revealed no deaths - There were no episodes of cardiopulmonary arrest or pulmonary aspiration reported in this series • The most recent study using sedation-trained nurses administering propofol to 36,743 patients at three centers with a limited selection of busy endoscopists reported - No fatalities or intubations - Only 0.1% to 0.2% needing assisted ventilation

  10. The incidence and severity of oxygen desaturation are critical data • One older study, assessing 261 consecutive patients receiving diazepam or midazolam plus meperidine - 45% of patients had an oxygen saturation (SaO2) of less than 90% - colonoscopy (54%) vs upper endoscopy (40%) • These findings may explain the increasing use of propofol - Propofol will wear off quickly and the patient will start to breathe again • A lower number of oxygen desaturation events (<90%) - Propofol vs midazolam/meperidine (12% vs 26%; P<0.01)

  11. Misjudging the depth of sedation with propofol is easier than with other agents, and the risk of apnea is greater (although prolonged oxygen desaturation may occur less frequently) • The primary concerns with propofol - Narrow therapeutic window -> Potential to cause severe respiratory and cardiopulmonary complications -> Requires the presence of ananesthesiologist or nurse anesthetist - Minimal-to-moderate sedation can decrease ventilatory drive and produce hypoxemia - Airway manipulations to prevent or reverse airway obstruction may be required

  12. The use of combination regimens increases the risk of oversedation and cardiopulmonary complications - Benzodiazepine/opioid and propofol/opioid combinations • Although only 65% of the total study population had received an opioid -> 94% of patients who experienced cardiopulmonary complications had received a concomitant opioid • Patient characteristics also influence the safety of sedative regimens - Morbid obesity, older age - Underlying cardiovascular, pulmonary, renal, hepatic, metabolic, and neurologic disease -> Risk factors for the development of hypoxemia

  13. 3. Disadvantages of currently available agents • Benzodiazepines - lipid-soluble (particularly midazolam) - Repeat doses result in accumulation in adipose tissue that is subsequently released, resulting in prolonged effects • Newcomer and colleagues - 4% of patients had an unplanned work absence the day after their colonoscopy - The most common reasons for missing work were feeling sleepy and weak, or experiencing abdominal pain and bloating

  14. Propofol - fast onset and rapid recovery - When used alone, propofol can cause deep sedation, resulting in hypotension and respiratory depression • Propofol vs midazolam/meperidine for outpatient colonoscopy - Greater mean level of sedation (propofol) -> Fewer propofol-treated patients being able to assist with the procedure (eg, changing position) -> Increased risk of perforation because patients are not able to report pain

  15. The ASA and the American Association of Nurse Anesthetists issued a joint statement in 2004 - "whenever propofol is used for sedation/analgesia, it should be administered only by persons trained in the administration of general anesthesia" • There is controversy regarding the safety of propofol when administered by nonanesthesiologists -> Nonanesthesiologists in general are reluctant to use it • These clinicians are instead likely to continue to use sedatives with which they are comfortable, such as a benzodiazepine with an opioid

  16. 3.1. Properties of an ideal agent • The ideal agent for sedation - Consistent and predictable pharmacokinetic/pharmacodynamic profile - Rapid onset of action - Analgesic and anxiolytic effects - Immediate resolution of sedation without any lingering effects on mental and psychomotor function - Amnestic period extending long enough for the procedure - Minimal associated risks or adverse effects - No pain on injection - No requirement for administration by ananesthesiologist • Although available agents have some of these properties, none fulfill all of the criteria

  17. 4. New Concepts in Sedation for Colonoscopy • New concepts in sedation for colonoscopy - Enhanced mechanisms for drug delivery [target-controlled infusion (TCI) and PCS] - Development of new drugs [modified cyclodextrin-based formulation of propofol, fospropofol disodium (Aquavan Injection), a water-soluble prodrug of propofol] • Propofol - lipid-based formulation Cyclodextrins - widely used as solubilizing agents -> injectable format

  18. A modified cyclodextrin-based formulation of propofol - Eliminate some of the formulation-dependent problems (pain on injection and the support of microbial growth) -> Similar sedative effects, but producing less pain on injection • No differences in sedative, hemodynamic, or respiratory effects Statistically worse pain score

  19. Fospropofol disodium (Aquavan Injection) - Novel sedative/hypnotic - Water-soluble prodrug of propofol with pharmacokinetic and pharmacodynamic properties that differ from those of propofol emulsion - Hydrolyzed by alkaline phosphatase to release propofol

  20. Results of the most recent dose-response study conducted in 127 patients with ASA physical status I, II, III, and IV - Sedation success was dose dose-dependent (without the need for alternative sedative medication and without requiring manual/mechanical ventilation) - 2, 5, 6.5, and 8mg/kg 1) sedation success - 24.0%, 34.6%, 69.2%, and 95.8% 2) Time to discharge - 6.0, 4.0, 7.5, and 11.5 minutes - 25% of patients in the 8mg/kg group went into deep sedation (3.8% of patients in both the 5mg/kg and 6.5mg/kg groups) - No patient required manual or mechanical ventilation, and there were no deaths - The most common adverse events were burning sensation, paresthesia, and pruritis • Aquavan 6.5mg/kg - high level of sedation success (87% of patients) - high level of physician- and patient- rated satisfaction

  21. PCS - Self-administered by the patient in response to pain (the patient has to be conscious enough to press the handheld button) - Lockout time - Rapid-acting drugs such as propofol and alfentanil -> oversedation unlikely to occur • Target-controlled infusion systems - According to the drug's pharmacokinetics, using an infusion pump controlled by a computer - Complex mathematical models - to compute the drug dosage and they may account for various patient characteristics that alter drug disposition

  22. Propofol - the most frequently infused drug via TCI • PCS using IV boluses of propofol vs patient-maintained sedation using TCI of propofol - Mean time ± SD taken for titration to adequate sedation - 5.7 ± 3.1 vs 8.6 ± 3.7 min (P<0.005) - Two (9%) patients became oversedated during PCS - Most patients preferred PCS using TCI

  23. 5. Conclusions • Sedation and analgesia are routinely provided for most patients undergoing colonoscopy in the United States, so as to allow them to tolerate the procedure • An ideal agent for procedural sedation - Provide rapid, controlled onset and recovery, analgesia, and no pain on injection - Can be safely administered by nonanesthesiologists • There are many different medications - None of the currently available sedative/hypnotic agents completely fulfills these needs

  24. Benzodiazepines and opioids ->> Propofol - Rapid onset of action - Full relief from discomfort - Rapid recovery to alertness without residual sedative effects • Narrow therapeutic window -> potential to cause deep sedation • New sedation agents and delivery systems under development -> potential to improve the quality of endoscopic sedation

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