4 Patient Preparation and Sedation for Endoscopy
T. Wehrmann
4.1 Introduction
Sedation in endoscopy is drug-induced reduction of the patients’ consciousness. The aim of sedation in endoscopic procedures is to increase the patient′s comfort and to improve endoscopic performance, especially during therapeutic procedures. Traditionally, the sedation regimen most commonly used for conscious sedation during gastrointestinal endoscopy was a combination of benzodiazepines and opioids. However, the use of propofol has enormously increased during the last two decades, and several studies showed advantages of propofol over the traditional regimes in terms of faster recovery time. Conversely, one must be aware that the complication rates of endoscopic procedures might increase when using propofol sedation. Therefore, a thorough risk evaluation before the procedure and monitoring during the procedure are paramount. In addition, properly trained staff and emergency equipment are essential. Sedation can be provided by anesthesiologists, nonanesthesiologist physicians (i.e., gastroenterologists or surgeons), or a well-trained nursing staff, depending on institutional and regional restrictions. Nurse-administered sedation for low-risk endoscopic procedures and low-risk patients has become accepted in some European countries. Ideally, a sedation regimen is tailored to the individual patient after assessment of clinical risk and patient anxiety level, as well as to the complexity of planned endoscopic procedure.
Analgesia is the elimination of pain by analgesic agents. The combination of sedation and analgesia is used to achieve optimal patient tolerance during diagnostic and therapeutic endoscopic procedures. Patient tolerance, in turn, is important for successful completion and safety, which leads to better patient compliance with subsequent endoscopies. 1 Procedural sedation provokes a high level of physician and patient satisfaction, and may improve the quality of an endoscopic examination. 2 , 3 Although it is feasible to perform routine endoscopies without sedation in selected patients, for complex endoscopic procedures sedation is required. 4 , 5 , 6 The sedation frequency for endoscopic procedures has risen significantly during the last two decades. 7 , 8 , 9 , 10 As a consequence, several guidelines have been published regarding endoscopic sedation. 4 , 5 , 6 , 11 , 12 , 13 , 14 , 15 , 16 , 17
4.2 Presedation Assessment
Before choosing a sedation strategy, an appropriate risk assessment is necessary. Cardiorespiratory problems, which could occur during endoscopy, should be carefully evaluated for each patient. A detailed past medical history and a focused physical examination should be conducted. This includes at least vital signs and weight measurement, heart and lung auscultation, blood pressure measurement, and an airway assessment using the Mallampati classification (▶Table 4.1).
Patients should then be classified using the criteria of the American Society of Anesthesiologists (ASA) (▶Table 4.2), and the respective ASA score should be documented. Patients with an ASA class ≥ III are at an increased risk for sedation-related complications. 18 Morphologic characteristics that may make airway management more difficult, such as a reduced ability to open the mouth (Mallampati III or IV), 19 a short neck (chin–hyoid distance < 4 cm), and history of difficult endotracheal intubation, should be considered. Further risk factors to be aware of are a history of sleep apnea, alcohol or substance abuse, adverse reaction to sedation, and anticipated prolonged procedure duration; such patients are not suitable for nurse-administered sedation, and sedation must be performed by a second physician who is not directly involved in the endoscopic procedure. Otherwise, the assistance of an anesthesiologist should be considered. 1 , 3 , 4 , 5 , 6
Pregnancy testing is recommended for women of childbearing age who may be pregnant. In general, endoscopy during pregnancy is not recommended unless there is a strong indication, and, if possible, should be postponed until the second trimester. 20
A presedation visit is important for the evaluation of possible risk factors and for planning of the individualized sedation regimen. Furthermore, informed written consent should be obtained for both the endoscopy and the sedation plans, including possible adverse events. Recommendations regarding fasting before elective procedures vary. According to ASA recommendations, patients should fast a minimum of 2 hours prior to a procedure following clear liquid ingestion and 6 hours for a light meal. 21
Requirements regarding airway management and cardiac life support must be available, and endoscopic sedation should only be provided by properly trained staff. Maintenance of personal qualification of the endoscopy team through repeated participation in dedicated training courses is recommended. 4 , 5 , 6
4.3 Monitoring during Endoscopic Sedation
4.3.1 Introduction
Changes of the patient’s level of consciousness during endoscopic sedation occur along a continuum. Although most endoscopic (diagnostic) procedures are performed under moderate sedation, a prediction of patient response to sedation is not always possible, and some patients may move past moderate sedation levels into deep sedation. 3 Therefore, clinical monitoring of the patient’s level of consciousness is important and requires the full attention of qualified staff (nurse or physician certified in cardiac life support) who are not involved in the endoscopic procedure, especially in difficult therapeutic procedures and/or when deep sedation is planned.
Observation of patient awareness, compliance with the procedure, pain reactions, and reflex status is difficult to assess in a darkened procedure room and during the performance of endoscopic interventions. Therefore, adequate monitoring of cardiorespiratory parameters is mandatory to allow for detection of early signs of patient distress; clinical assessment should be supported by objective data through technical monitoring.
4.3.2 Hemodynamic Monitoring
Heart rate and blood pressure should be determined before sedation is initiated, and should be monitored every 3 to 5 minutes during the procedure, depending on clinical requirements, and especially during propofol administration. 4 , 5 , 6 , 11 , 12 , 13 , 14 , 15 , 16 , 17 Hemodynamic parameters may be affected not only by the sedative agents but also by the endoscopic procedure. For example, tachycardia and hypertension may be indicative of inadequate depth of sedation, whereas bradycardia and hypotension may be caused by oversedation.
Electrocardiography
Electrocardiography (ECG) is only recommended in patients with significant cardiovascular disease to detect and analyze cardiac arrhythmia during endoscopy. 4 , 5 , 6 ECG is not required for low-risk patients (ASA I or II). 4 , 5 , 6 Other patients in whom ECG monitoring should be considered are elderly patients and those in whom prolonged procedures are anticipated. However, the precise value of ECG monitoring in these groups of patients has not been established.
Pulse Oximetry
This noninvasive method, used to monitor hemoglobin oxygenation, is recommended for all patients, irrespective of the sedation regimen or type of endoscopic procedure. 3 , 4 , 5 , 6 , 11 , 12 , 13 , 14 , 15 , 16 , 17 Although oxygen desaturation can be readily assessed, it is relatively insensitive for detecting hypoventilation, because oxygen desaturation is a late sign of depressed ventilation. Typically, 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.
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