Physiologic Montitoring
Monitoring Technology

Targeting moderate sedation is generally considered a safe goal for non-anesthesiologists. However, the exact dose of any sedation agent needed to complete the procedure in a given patient is impossible to accurately predict. (see Patient Factors Involved in Choice of Sedation Regimen). Therefore, a successful outcome is dependent on an understanding of incremental dosing, the synergistic effects of drug classes, and the onset of action and peak effects of sedation agents. In addition, appropriate monitoring should be in place and clinicians should always be prepared to rescue patients who move to the next deeper level of sedation. Before embarking on a procedure, the endoscopist must decide the level of sedation necessary for that procedure and ensure that the proper personnel and equipment are in place to recognize and manage complications should they occur. 

The Society of Gastroenterology Nurses and Associates (SGNA) Statement on the Use of Sedation and Analgesia in the Gastrointestinal Endoscopy Setting articulates the levels of sedation as well as the role of the registered nurse in moderate and deep sedation.

The American Society for Gastrointestinal Endoscopy (ASGE) Guidelines for Conscious Sedation and Monitoring during Gastrointestinal Endoscopy state that all patients undergoing endoscopic procedures under moderate or deep sedation should be monitored before, during and after the administration of sedatives.  

The ASGE and SGNA Joint Position Statement on the Role of GI Registered Nurses in the Management of Patients Undergoing Sedated Procedures clarifies the roles of physician and nurses for patient monitoring during sedation.

Physiologic Monitoring

The Practice Guidelines for Sedation and Analgesia by Non-Anesthesiologists published by the American Society of Anesthesiologists (ASA) outlines the following areas for patient monitoring during moderate or deep sedation. 

• Level of consciousness. Patient response to verbal commands and stimuli while undergoing sedation and analgesia is a guide to the level of consciousness. Monitoring levels of consciousness can help detect adverse drug responses so they can be treated in a timely manner, thus reducing risks for both moderate and deep sedation. A patient under moderate sedation should be able to respond to verbal commands and light tactile stimuli. Response during deep sedation will require more profound stimuli. A patient whose only response is reflex withdrawal from painful stimuli are deeply sedated, bordering on general anesthesia.
• Pulmonary ventilation. Drug-induced respiratory depression is the primary cause of morbidity associated with sedation and analgesia. The risk of adverse outcomes can be reduced by monitoring ventilatory function through observation or auscultation (including thoracic palpation, observation of abdominal/chest excursions and sensation of exhaled air). Monitoring via capnography may reduce risks during moderate and deep sedation, and automated apnea monitoring may have application when the patient is physically separated from the caregiver. Because ventilation and oxygenation are separate physiologic processes, pulse oximetry cannot substitute for monitoring ventilatory function.
• Oxygenation. The risk of adverse events such as cardiac arrest and death can be decreased through the use of pulse oximetry with appropriate alarms for the early detection of hypoxia. Pulse oximetry has been shown to be more effective in detecting oxygen desaturation and hypoxemia during sedation/analgesia than clinical assessment alone.
• Hemodynamics. Regular monitoring of vital signs reduces the likelihood of adverse outcomes during both moderate and deep sedation.  Sedative and analgesic agents may interfere with the appropriate autonomic compensation for hypovolemia and procedure-related stressors.  Inadequate sedation or analgesia, on the other hand, may result in patients developing dangerous autonomic stress responses such as tachycardia and hypertension.  The risk of these complications may be reduced with early detection of changes in heart rate and blood pressure that lead to interventions to avert serious problems. Vital signs should be monitored every 3-5 minutes once a stable level of sedation has been established.   Continuous electrocardiogram monitoring can be used to reduce risks during deep sedation and for high-risk patients (significant cardiovascular disease or dysrhythmias) during moderate sedation. There is no clear opinion supporting the use of electrocardiography in normal-risk patients during moderate sedation. 

*The current package insert notes that for general anesthesia or monitored anesthesia care (MAC) sedation, propofol should be administered only by persons trained in the administration of general anesthesia and not involved in the conduct of the surgical/diagnostic procedure. There is a body of literature that has demonstrated the safety and efficacy of trained gastroenterologists and registered nurses administering propofol sedation for gastrointestinal endoscopic procedures in a carefully selected patient population. The reader is invited to review the bibliography and associated links.

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Monitoring Technology

In addition to observation by a member of the endoscopy team dedicated to patient monitoring, a number of electronic monitoring methods can be used to assess patient status. Electronic monitoring should never replace close observation by a well-trained assistant. 

• Pulse oximetry. Pulse oximetry, using a finger or ear-probe sensing device, is a continuous, non-invasive monitoring method of a patient’s arterial hemoglobin saturation and heart rate.  It is important to recognize that pulse oximetry measures oxygenation, not ventilation.  Especially in the presence of supplemental oxygen, arterial oxygen desaturation as measured by pulse oximetry may represent a delayed sign of hypoventilation. For this reason, pulse oximetry cannot be considered a replacement for direct observation of patient ventilatory function.

• Electronic blood pressure monitoring equipment. Automatic noninvasive blood pressure devices can provide a valuable adjunct to patient monitoring. Whenever possible, blood pressure should be determined before sedation/analgesia is established.  The patient’s hemodynamic status can be closely tracked by setting the cycle for 1 minute intervals.  It may take several cardiac cycles before readings are accurate. Accuracy of the readings will also be affected by erratic cuff movements and improperly-fitting cuffs.  The American Heart Association recommends that the cuff size should equal 40% of the arm circumference.

• Continuous electrocardiogram (EKG) monitoring. Use of electrocardiography during sedation/analgesia delivers real-time assessment of the patient’s heart rate. It can help the clinician identify dysrhythmias, myocardial ischemia, electrolyte disturbance, and pacemaker function.

• Capnography. Capnography is the continuous analysis and recording of carbon dioxide (CO2) concentrations in respiratory gases throughout respiration. The measurement of end-tidal carbon dioxide (ETCO2) offers the clinician a useful adjunct to other monitoring methods in determining if hypercarbia is present.  Capnography may be able to detect hypoventilation before pulse oximetry indicates oxygen desaturation. It has also been shown to be a more sensitive gauge of hypoventilation than visual observation.  In procedural sedation, sidestream capanography equipment usually consists of sampling probes to measure gases from the nose and sometimes the mouth. Additional oxygen can be administered through the same cannula. Continuous sampling of gases during inhale and exhale is managed through an aspiration port. 

• Bispectral index analysis (BIS monitoring). BIS technology directly assesses a patient’s level of consciousness by measuring the effects of anesthesia on the brain. Using a self-adhesive forehead probe, the bedside device records encephalographic activity which is translated into a BIS index that ranges from 0 to 100, with 70 to 90 indicating moderate sedation, and 60 to 69 indicating deep sedation. However, a recent observational study concluded that BIS has a low accuracy for detecting deep sedation and BIS scores correlated poorly with sedation levels determined by the Modified Observer's Assessment of Alertness and Sedation (MOAA/S). In addition, the usefulness of BIS during NAPS has been brought into question by research that indicates the patient’s BIS score lags substantially behind level of consciousness during sedation with propofol.

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Sources

American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-Anesthesiologists. Practice Guidelines for Sedation and Analgesia by Non-Anesthesiologists. Anesthesiology. 2002; 96(4):1004-17.

American Society for Gastrointestinal Endoscopy. Guidelines for conscious sedation and monitoring during gastrointestinal endoscopy. Gastrointestinal Endoscopy. 2003;58(3): 317-322.

Cohen LB, DeLegge MH, Aisenberg J, Brill JV, Inadomi JM, et al. AGA Institute review of endoscopic sedation. Gastroenterology. 2007 Aug;133(2):675-701.

Dobbins K. Protocols for Practice: Noninvasive Blood Pressure Monitoring, Critical Care Nurse. 2002;22(2):123-124

Drake LM, Chen SC, Rex DK. Efficacy of bispectral monitoring as an adjunct to nurse-administered propofol sedation for colonoscopy: a randomized controlled trial. Am J Gastroenterol. 2006;101(9):2003-7. 

Kost M. Moderate Sedation/Analgesia: Core Competencies for Practice, 2nd Ed. St. Louis, MO: Saunders, St. Louis; 2004:147.

Lightdale CJ, Lightdale JR. Advances in Endoscopy and Endoscopic Sedation. Medscape, 2003.

Qadeer MA, Vargo JJ, Patel S, et al. Bispectral index monitoring of conscious sedation with the combination of meperidine and midazolam during endoscopy. Clin Gastsroenterol Hepatol. 2008;6(1):102-8. 

Rex DK. Moderate Sedation for Endoscopy: Sedation Regimens for Non-Anesthesiologists. Ailment Pharmacol Ther. 2006;24(2):163-171

Wiener-Kronish J, Grooper. Conscious Sedation. Philadephia, PA: Hanley & Belfus, Inc; 2001:79.

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Last Updated October 1, 2008