Gastroenterological Endoscopy. Группа авторов

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

Table 4.2 Physical status classification system of the American Society of Anesthesiologists (ASA)

ASA class	Definition
I	Hea lthy; no risk
II	Mild to moderate systemic disease, with no functional limitation; minimal risk
III	Severe systemic disease, but not incapacitating; moderate risk
IV	Severe incapacitating disease that is a constant threat to life; high risk
V	Moribund, patient is not expected to survive 24 hours irrespective of procedure/operation; very high risk
Source: Adapted from the ASA task force.^13

      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