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The fact that most gastrointestinal endoscopy procedures require some level of sedation raises patient safety concerns. Most sedation for such procedures involves use of benzodiazepines with or without an opioid. Propofol has also been used in some circumstances. Propofol has the advantage of rapid onset of action and predictable depth of sedation but it has a relatively narrow therapeutic window. Moreover, it lacks a reversal agent. Therefore, use of propofol usually requires administration by an anesthetist or anesthesiologist.
The emergence of propofol target-controlled infusion (TCI) systems is felt by some to provide a potential alternative to anesthetist-managed sedation. Propofol TCI systems are pre-programmed with pharmacokinetic models and some adjust for patient weight and age.
A recent study from a tertiary medical center in Argentina analyzed the experience of patients who had undergone elective gastrointestinal endoscopy under propofol target-controlled infusion sedation (García Guzzo 2020). 823 outpatients, age 18 and older with ASA scores I–III (85% were actually score I-II) who underwent diagnostic and therapeutic EGD, colonoscopy, or both were included in the analysis. 48% had colonoscopy alone and 37% had combined EGD and colonoscopy. Patients who had endoscopic retrograde cholangiopancreatography, enteroscopy, and procedures performed under planned tracheal intubation were excluded from the study. The propofol target-controlled infusions (TCI’s) were administered and monitored by anesthetists. Conventional monitoring included blood pressure, EKG, and oxygen saturation by pulse oximetry. Capnography apparently was not used.
The following adverse events were noted during the procedure: oxygen desaturation < 95% (rate 22.35%), vasoactive drug administration (19.2%), hypotension (12.64%), and oxygen desaturation < 90% (9.92%). Only 0.5% of patients required advanced airway management. No patients required ACLS or died. In the post-anesthetic period, hypotension occurred in 4.6% and oxygen desaturation (SaO2 < 95%) in 0.12%. No patients had SaO2 < 90%. The incidence of nausea/vomiting episodes was 0.6%. No patients required advanced airway management or ACLS during the post-anesthetic period. Colonoscopy and higher doses of propofol were associated with hypotensive episodes. All patients were discharged on the day of the procedure.
A strong dose-effect relationship was found between hypoxia and obesity; patients with body mass index ≥40 were nine times (odds ratio 10.22) more likely to experience oxygen desaturation < 90% events.
The authors conclude that propofol sedation using target-controlled infusion appears to be a safe and effective anesthetic technique for gastrointestinal endoscopic procedures with acceptable rates of adverse events and could be more widely adopted in clinical practice.
Overall, this was a low-risk population and the procedures were relatively low-risk, So the results cannot be extrapolated to patients with higher ASA scores. These results are comparable or better than most results reported for use of other sedation regimens for such gastrointestinal endoscopic procedures.
Though the overall safety profile looks very good, we are concerned about use of propofol in patients with obesity. In fact, the researchers found a strong dose–effect relationship between obesity and episodes of oxygen desaturation to SaO2 < 90%. Compared to patients with a normal BMI, the risk of those with BMI 30–35 was almost double (OR 1,68), for those with BMI 35–40 three times (OR 2.85) and for those with BMI ≥40 nine times (OR 10.22) more likely to experience episodes of oxygen desaturation to SaO2 < 90%.
Of course, we would not be surprised if those same rates of desaturation are seen in obese patients undergoing these procedures using alternative sedation protocols. Obese patients have a high incidence of obstructive sleep apnea (OSA) and apneic episodes are probably as likely triggered by sedation with benzodiazepines, opioids, or propofol. Also keep in mind that 87% of the patients in this study received not only propofol but also received the opioid fentanyl.
The authors note that use of a high-flow nasal cannula or continuous positive airway pressure via nasal mask (SuperN2va) have been proposed to reduce oxygen desaturation events for spontaneously breathing obese patients.
We remain cautious about the use of propofol with or without an opioid for GI endoscopic procedures in obese patients (or others who are at risk for obstructive sleep apnea). We’d probably like to see use of capnographic monitoring for that population. But the jury is still out on the value of capnography in the GI suite. Our March 2018 What's New in the Patient Safety World column “Capnography in the GI Suite” discussed that issue. The ASGE guidelines for sedation and anesthesia in GI endoscopy (Early 2018) state “capnography has been demonstrated to detect depressed respiratory activity before transient hypoxemia, but a clear link between transient hypoxemia and serious cardiopulmonary unplanned events during sedated endoscopy has not been established. Integrating capnography into patient monitoring protocols for endoscopic procedures with moderate sedation has not been shown to improve patient safety; however, there is evidence supporting its use in procedures targeting deep sedation.” However, under its recommendations for propofol use during endoscopy, it does state “Capnography should be considered because it may decrease the risks during deep sedation.” And under their summary recommendations they “suggest that capnography monitoring be considered for patients undergoing endoscopy targeting deep sedation.”
Most of the studies looking at the added value of capnography in GI procedures have concluded that, while capnography may reduce the number of hypoxic events, it has not changed the overall risk of serious events (Kim 2018, Veazie 2020, Saunders 2017).
A recent study at a high-volume university hospital GI department (Bisschops 2019) found that the relative risks of experiencing both adverse events and interventions during recovery were reduced significantly in patients monitored by capnography compared to a control group. There were 1,044 patients in the capnography arm and 1,092 patients in the control arm. The primary endpoint (change in total incidence of mild oxygen desaturation, severe oxygen desaturation, bradycardia, and tachycardia) occurred on average 11.45 times per 100 procedures in the control group, compared to 5.08 times per 100 procedures in the group monitored by capnography, a 55.69% reduction. There were nine escalations of care in the control group and none in the capnography group.
Jopling and Qiu (Jopling 2017) performed a retrospective analysis of a huge number of inpatients and outpatients undergoing gastrointestinal endoscopic procedures with sedation. They found the use of capnography was associated with and a 61% estimated reduction in the odds of a pharmacological rescue event compared to the matched outpatient population. (And note that, for the inpatient population, use of capnography was associated with a reduction in both mortality and pharmacologic rescue rates.)
But most studies have not stratified the patients by obesity or OSA risk. One study (Prathanvanich 2015) used capnography during upper endoscopy in morbidly obese patients and found it very useful in detecting early respiratory depression and no clinically significant cardiorespiratory complications occurred. However, there was no control group for comparison.
While the Argentina study suggests that propofol sedation using target-controlled infusion appears to be a safe and effective anesthetic technique for gastrointestinal endoscopic procedures with acceptable rates of adverse events, we would still recommend that capnography be used to monitor high risk patients (those with obesity or other risk factors for OSA) and those in whom a deeper level of sedation is considered likely.
García Guzzo ME, Fernandez MS, Sanchez Novas D, et al. Deep sedation using propofol target-controlled infusion for gastrointestinal endoscopic procedures: a retrospective cohort study. BMC Anesthesiology2020; 20(1): 195
Early DS, Lightdale JR,Vargo JJ, et al for the ASGE Standards Of Practice Committee. Guidelines for sedation and anesthesia in GI endoscopy. Gastrointestinal Endoscopy 2018; 87(2): 327-337
Kim SH, Park M, Lee J, Kim E, Choi YS. The addition of capnography to standard monitoring reduces hypoxemic events during gastrointestinal endoscopic sedation: a systematic review and meta-analysis. Ther Clin Risk Manag 2018;14: 1605-1614. Published 2018 Sep 6
Veazie S, Vela K, Mackey K. Evidence Brief: Capnography for Moderate Sedation in Non-Anesthesia Settings. US Department of Veterans Affairs Evidence Synthesis Program; June 2020
Saunders R, Struys MMRF, Pollock RF, et al Patient safety during procedural sedation using capnography monitoring: a systematic review and meta-analysis. BMJ Open 2017; 7: e013402
Bisschops R, Demedts I, Roelandt P. et al. Capnography During Endoscopy – A Value-Based Healthcare Pilot In A High-Volume Gastroenterology Practice. Endoscopy 2019; 51(04): S165
Jopling MW, Qiu J. Capnography Sensor Use Is Associated With Reduction of Adverse Outcomes During Gastrointestinal Endoscopic Procedures With Sedation Administration
BMC Anesthesiol 2017; 17(157): Published 28 November 2017
Prathanvanich P, Chand B. The role of capnography during upper endoscopy in morbidly obese patients: a prospective study. Surgery for Obesity and Related Diseases 2015; 11(1): 193-198
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