Gastroenterological Endoscopy. Группа авторов
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Название: Gastroenterological Endoscopy

Автор: Группа авторов

Издательство: Ingram

Жанр: Медицина

Серия:

isbn: 9783131470133

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СКАЧАТЬ hypoxemia occurs within 5 minutes of medication administration or intubation of the endoscope.22 Patients with a baseline oxygen saturation of less than 95% are at risk for respiratory complications during sedation, and require close monitoring.22 Limitations of pulse oximetry include the inability to detect an adequate signal as a consequence of hypothermia, low cardiac output, or motion artifacts.

      Capnography

      The noninvasive monitoring of carbon dioxide in exhaled breath is more sensitive in detecting hypoventilation than direct visual observation or pulse oximetry.23 Pulse oximetry is less sensitive when apnea occurs, because 60 to 120 seconds may elapse before arterial oxygen saturation begins to fall. Data from two randomized controlled studies show that episodes of apnea or disordered respiration can be detected significantly more frequently when using capnography as compared to pulse oximetry, but no difference in clinically relevant outcomes was seen.24,25 Therefore, most guidelines do not recommend routine use of capnography for monitoring during endoscopic sedation.4,5,6 However, the use of capnography is reasonable for patients with a high risk for respiratory depression.6

      Documentation of the Sedation Procedure and Administration of Supplemental Oxygen

      Most guidelines recommend that monitoring data (clinical and technical parameters), as well as drug administration, should be routinely documented.4,5,6,11,12,13,14,15,16,17

      Oxygen supplementation has been shown to significantly reduce the frequency of severe hypoxemia.26,27 However, oxygen supplementation can decrease respiratory drive in patients with pronounced hypercapnia due to chronic obstructive pulmonary disease. Additionally, preventive oxygen supplementation might cause a delay in detection of hypoventilation.28 However, most guidelines recommend the use of oxygen supplementation during endoscopic sedation.3,4,5,6

      4.4 Pharmacology

      4.4.1 Introduction

      The most commonly used drugs for sedation in gastrointestinal endoscopy are benzodiazepines, opioids, and propofol. Propofol use has increased enormously in the last decade after several studies demonstrated advantages over traditional benzodiazepine/opioid combinations, including faster recovery, and with the same safety profile.29,30,31 The pharmacologic profiles of the drugs most commonly used for sedation in endoscopy are listed in

Table 4.3.

      4.4.2 Benzodiazepines

      Benzodiazepines enhance the effect of the neurotransmitter gamma-aminobutyric acid (GABA), which results in sedative, hypnotic, anxiolytic, anticonvulsant, and amnesic action.32 The benzodiazepines diazepam and midazolam are the most commonly used sedatives in gastrointestinal endoscopy, and have comparable efficacy and safety.32,33 Because benzodiazepines do not have an analgesic effect, addition of an opioid is often necessary. Midazolam is frequently the drug of choice over diazepam for endoscopic procedures because of its rapid onset, short duration of action, 1.5 to 3.5 times higher sedation potency, and lack of associated phlebitis.34 In addition, midazolam has less respiratory depression and superior patient satisfaction compared to diazepam.34,35 However, the potency of midazolam increases in patients older than 60 years, with an increased potential for causing respiratory depression. Therefore, the dose of midazolam should be decreased and the intervals between administrations should be longer in such patients.35

      An advantage of benzodiazepines is temporary reversibility through the antagonist flumazenil (0.1–0.3 mg intravenous bolus). Because the half-life of action of flumazenil is shorter than that of midazolam/diazepam, resedation may occur after flumazenil reversal.3

      4.4.3 Opioids

      Introduction

      Opioids have a high analgesic effect, in addition to a mild sedative effect. The two most commonly used opiates for gastrointestinal endoscopy are meperidine/pethidine and fentanyl.9,10 They are often used in combination with benzodiazepines during endoscopic procedures, which is important as the sedation effect is quite pronounced. Because of the increased central nervous system depression, the opioid dose should be reduced when combination therapy is used, especially in the elderly and in patients with significant renal or liver dysfunction. Moderate sedation with a benzodiazepine/opioid combination results in high levels of physician and patient satisfaction, with a low risk of serious adverse events.3,29

      Pethidine Hydrochloride (Meperidine)

      Pethidine hydrochloride (meperidine) should be used primarily in procedures lasting longer than 30 minutes, because of its half-life of 3 to 4 hours. It is metabolized in the liver to normeperidine, an active metabolite with a half-life of 15 to 20 hours. Therefore, the clearance of meperidine may be significantly prolonged in patients with renal and hepatic insufficiency.3 In addition, the combination of meperidine with monoamine oxidase inhibitors is contraindicated due to the potential for life-threatening complications.36

      Fentanyl

      Because of its high degree of fat solubility fentanyl has a rapid onset and brief duration of action. In addition, it reduces the incidence of nausea as compared to meperidine and has analgesic properties approximately 100 times more potent than morphine, with relatively little effect on the cardiovascular system. Fentanyl has a shorter overall procedure duration during upper endoscopy and colonoscopy due to faster recovery.

      A dose reduction of 50% or more is recommended in the elderly.3 Fentanyl has a narrow therapeutic range with a high risk of respiratory depression, which may persist longer than the analgesic effect.3 In addition, it must be injected slowly to avoid chest-wall rigidity associated with rapid administration.3

      The central nervous effects of all described opioids can be reversed by intravenous administration of naloxone. The onset of action is only 1 to 2 minutes but its half-life is 30 to 45 minutes, and patients receiving naloxone should be monitored for at least 2 hours.3

      4.4.4 Propofol

      Pharmacology

      Propofol, a phenol derivate, is a short-acting hypnotic agent. It has a rapid onset of action and a rapid elimination, which leads to significantly faster time to sedation and shorter recovery times compared to other agents.3,29,37 Propofol is significantly more efficacious than the combination of midazolam and meperidine for therapeutic endoscopies.31,37,38

      Propofol has a weaker amnesic effect than midazolam, and has virtually no analgesic effects. However, the lack of analgesia is somewhat compensated when deeper sedation is reached. Dose reduction is not necessary for patients with moderately severe liver disease or renal failure, whereas a dose reduction is mandatory in patients with cardiac dysfunction and in the elderly.3 For interventional endoscopic procedures, propofol has been shown to be at least as safe as midazolam/pethidine, СКАЧАТЬ