Endoscopy Practice and Sedation: Endoscopy Practice and Sedation: Safe Sedation

0:00Welcome to Board Pearls. This is episode three of four of the Endoscopy Practice and Sedation chapter, in the Endoscopic Procedures module. This episode is keeping sedation safe, and changing the plan for the patients who need it. The first patient is a woman whose capnography goes flat in the middle of a colonoscopy, and her case shows why capnography sees apnea before the pulse oximeter, how to predict a difficult airway, who needs full-stomach precautions, how to dose naloxone and flumazenil and why to keep watching after they work, and who must never get flumazenil. Four more patients then show the groups in whom the standard sedation plan changes: a man with cirrhosis, an older woman living alone, a man with sleep apnea, and a pregnant woman who needs an urgent procedure.

0:43Here's the first patient. A sixty-six-year-old woman is having a colonoscopy under moderate sedation with midazolam and fentanyl. She's taken alprazolam nightly for anxiety for ten years. Her body mass index, BMI, is thirty-seven. Before the procedure, with her mouth open and tongue out, only her soft palate was visible, and her chin-to-thyroid distance is about five centimeters. She's had four milligrams of midazolam and one hundred fifty micrograms of fentanyl and is on two liters of oxygen by nasal cannula. Twenty minutes in, her capnography waveform goes flat while her oxygen saturation reads ninety-eight percent.

1:21A flat waveform with a normal saturation is apnea: she's oversedated, and the capnograph is the monitor to believe. American Society of Anesthesiologists standards recommend capnography for all moderate and deep sedation, because end-tidal carbon dioxide reflects alveolar ventilation within one to two breaths, while pulse oximetry lags hypoventilation by thirty to ninety seconds in a patient on supplemental oxygen, whose oxygen reservoir delays desaturation. So loss of the waveform is the earliest reliable sign of apnea, and the oxygen she's receiving is masking the desaturation that would otherwise warn the team. Capnography reduces hypoxia and rescue events in randomized trials and is now standard of care for moderate and deep sedation.

2:07Her first response is support, not a drug. The procedure pauses, she's stimulated, her jaw is lifted, and her airway is supported until a weak waveform returns. She was meant to be at moderate sedation and has slid into deep sedation, which is why any team giving sedation has to be able to rescue a patient one level deeper than intended.

2:29Her airway exam had predicted that her rescue would be hard. The Mallampati classification scores what's visible with the mouth open and tongue out: class one shows the soft palate, uvula, and pillars; class two the soft palate and the base of the uvula; class three only the soft palate; and class four only the hard palate. Classes three and four predict difficult mask ventilation and difficult intubation. The other predictors are a thyromental distance under six centimeters, limited neck movement, prior difficult intubation, a small or receding jaw, a large tongue, a short neck, advanced rheumatoid arthritis involving the neck, trisomy twenty-one and other dysmorphic features, and a BMI over thirty-five. Any combination warrants anesthesia consultation before deep sedation or general anesthesia. She has Mallampati class three, a five-centimeter thyromental distance, and a BMI of thirty-seven. Airway prediction doesn't show who will stop breathing, because the drugs cause the apnea, but it shows whose rescue will be hard.

3:36A full stomach would have added aspiration to her risk, and it changes the airway plan entirely. Aspiration risk rises with gastroparesis, achalasia, gastric outlet obstruction, a recent meal, retained gastric content on a glucagon-like peptide one agonist, pregnancy after the first trimester, and a full bowel preparation in a colonoscopy patient with delayed transit. Those patients need either airway control, with general anesthesia, rapid sequence induction, and a cuffed endotracheal tube, or a delay until the risk is reduced. Rapid sequence induction shortens the gap between loss of consciousness and intubation, lowering the chance of passive regurgitation, and cricoid pressure is often applied during it, though its value is debated. Had she also had gastroparesis and finished her preparation three hours earlier, her airway would have called for anesthesia or a delay, not a nasal cannula.

4:30With her airway supported, her opioid is reversed first, because it's the drug that can be reversed safely in her. Her respiratory rate is six and her breathing shallow. Naloxone, a competitive mu-opioid antagonist, is dosed for sedation reversal at forty micrograms to four-tenths of a milligram intravenously every two to three minutes, titrated to breathing and consciousness, and at four-tenths to two milligrams as a starting dose for full opioid overdose. Its onset is within two minutes, and it lasts about thirty to ninety minutes, shorter than most opioids, especially methadone and sustained-release forms. So re-sedation can occur, and monitoring continues for at least four hours, longer after long-acting opioids. Abrupt full reversal can cause pain, hypertension, tachycardia, and pulmonary edema in opioid-tolerant patients, which is why small doses are titrated. Eighty micrograms bring her respiratory rate to twelve with a normal waveform.

5:26Her benzodiazepine isn't reversed, because her nightly alprazolam makes flumazenil dangerous. Flumazenil is a competitive antagonist at the benzodiazepine site of the gamma-aminobutyric acid type A receptor. It's dosed at two-tenths of a milligram intravenously over fifteen seconds, repeated each minute to a total of one milligram, with onset in one to two minutes and a duration of thirty to sixty minutes, shorter than midazolam's, so a patient who gets it is monitored for at least two hours. It's contraindicated in chronic benzodiazepine therapy and in seizure disorders, because abrupt benzodiazepine withdrawal can provoke seizures, and in mixed overdoses with tricyclic antidepressants, where it can unmask tricyclic-induced seizures. Her ten years of nightly alprazolam rule it out, and naloxone with airway support is enough.

6:16Her recovery is watched for the drugs that outlast their reversal. She's monitored for at least four hours after naloxone, with capnography and respiratory rate rather than saturation alone. Daily methadone would have needed longer monitoring and even more careful titration. Her airway predictors, her chronic alprazolam, and her combined midazolam and fentanyl were all visible beforehand, and together they favored lower doses, slower titration, or anesthesia support from the start.

6:44The rest of the episode is the patients in whom the standard plan changes because their pharmacology or aspiration risk is different. The first is a sixty-one-year-old man with alcohol-related cirrhosis, Child-Pugh B, with ascites controlled on diuretics and one episode of hepatic encephalopathy last year, now on lactulose and rifaximin. His creatinine has crept up to one point six, his blood pressure runs about one hundred over sixty, and he's booked for variceal screening esophagogastroduodenoscopy with sedation as usual.

7:15His cirrhosis, his encephalopathy, and his kidney function rule out sedation as usual. Cirrhosis prolongs midazolam, because falling hepatic CYP3A4 activity reduces its first-pass metabolism, and its active metabolites accumulate when there's kidney impairment, as in hepatorenal syndrome. Fentanyl is prolonged too, through reduced hepatic clearance. Any sedation also raises the risk of encephalopathy, because his brain is sensitized to drugs that act on gamma-aminobutyric acid, and sedation unmasks ammonia-driven encephalopathy, which he's already had once.

7:52His plan follows from those mechanisms. Midazolam doses are halved, with a typical induction of a half to one milligram and longer intervals, and many centers avoid benzodiazepines entirely in cirrhosis to preserve mental status. Propofol is generally preferred, because its clearance depends on hepatic blood flow rather than enzyme capacity, but patients with cirrhosis are often hypovolemic, and propofol's vasodilation causes more pronounced hypotension in them. So his plan is cautiously titrated propofol with close attention to his blood pressure, and no midazolam. A patient with Child-Pugh A disease, no encephalopathy, and a normal creatinine would still warrant reduced, slowly titrated midazolam. Anticoagulation and procedures in cirrhosis are covered in chapter twenty-three.

8:35Age changes the doses for a different reason, central sensitivity. An eighty-one-year-old woman is booked for colonoscopy for iron deficiency. She's otherwise well, lives alone, and walks with a cane. Patients over sixty-five need twenty-five to fifty percent dose reductions across all sedation agents, because of a smaller volume of distribution, reduced hepatic metabolism and kidney clearance, and greater central sensitivity from age-related changes in gamma-aminobutyric acid receptors and reduced cerebral blood flow. So the usual total midazolam dose of two to five milligrams falls to roughly one to under four, starting at the bottom, with the same reduction for fentanyl and propofol. Her peak effect is also delayed, three to seven minutes for midazolam compared with three to five in younger adults, so the usual intervals would stack doses on top of each other, and smaller boluses with longer gaps are used. Falls and prolonged sedation are the main adverse outcomes, so fall precautions apply after her procedure, and her discharge plan accounts for her cane and for her living alone.

9:36Sleep apnea changes the airway plan rather than the doses. A fifty-five-year-old man with obstructive sleep apnea who uses continuous positive airway pressure, CPAP, at home is booked for colonoscopy. Sleep apnea raises baseline aspiration and apnea risk, because the pharynx collapses more easily and breathing is more easily depressed by sedatives. Capnography is essential, and he uses his CPAP in recovery. Deeper sedation with airway-trained staff is preferred over moderate sedation that may slide into deeper sedation without the right monitoring, and some centers routinely use propofol with monitored anesthesia care for these patients. Patients without a diagnosis are screened before the procedure with STOP-BANG, which covers snoring, tiredness, observed apnea, blood pressure, BMI, age, neck circumference, and gender, and a high score prompts the same preparations.

10:30Pregnancy changes the plan again, because both aspiration risk and drug choice shift. A woman twenty weeks pregnant with choledocholithiasis needs endoscopic retrograde cholangiopancreatography, ERCP. After the first trimester, progesterone relaxes smooth muscle and the enlarging uterus compresses the stomach, delaying gastric emptying, so full-stomach precautions apply. Left lateral positioning keeps the uterus off the aorta and vena cava. Fetal monitoring is appropriate after twenty-two to twenty-four weeks, when the fetus is viable and intervention becomes possible.

11:07Her drugs are chosen on human data rather than the old letter categories. The twenty fifteen Pregnancy and Lactation Labeling Rule removed the Food and Drug Administration letter categories from drug labels, though older references list midazolam as D, fentanyl as C, and propofol as B. In practice, propofol is preferred when deeper sedation is needed, low-dose fentanyl is acceptable, midazolam is used sparingly and avoided in the first trimester when possible, and ketamine is avoided because it raises uterine tone. Elective endoscopy is deferred to the second trimester or after delivery when possible, because the first trimester carries teratogenic risk and the third carries a higher risk of preterm labor. Her ERCP isn't elective and falls in the preferred window, so she gets propofol with airway protection, a left lateral tilt, low-dose fentanyl if needed, no ketamine, and obstetric coordination. An elective esophagogastroduodenoscopy at nine weeks would be deferred, while an urgent ERCP for cholangitis at thirty-two weeks would proceed with fetal monitoring. Procedural timing in pregnancy is covered in chapter thirty-five.

12:12Here are the traps the boards set in sedation safety. A normal saturation on supplemental oxygen doesn't exclude apnea. Moderate and deep sedation need capnography. Mallampati class three or four, a short thyromental distance, or a BMI over thirty-five predicts a difficult airway, and a predicted difficult airway isn't taken deep without anesthesia. A full stomach isn't sedated without airway protection. An opioid-tolerant patient gets titrated naloxone, not a full bolus. Flumazenil isn't given with chronic benzodiazepine use or seizures. And a patient isn't discharged soon after reversal, because the reversal wears off first.

12:51For special populations, the traps are these. Standard midazolam doses aren't used in cirrhosis, sedation can precipitate encephalopathy, and propofol in cirrhosis needs attention to hypotension. Older patients don't get full doses, and they aren't redosed before the drug has peaked. Sleep apnea isn't sedated without capnography, and CPAP is used in recovery. A pregnant patient isn't laid flat, ketamine isn't used in pregnancy, and elective procedures aren't done in the first or third trimester.

13:24So, start to finish. Use capnography for all moderate and deep sedation, because it detects apnea within a breath or two, while oximetry lags thirty to ninety seconds on oxygen. Predict the difficult airway and involve anesthesia, and protect a full stomach with rapid sequence induction or delay. Reverse opioids with titrated naloxone and monitor for at least four hours, and reverse benzodiazepines with flumazenil and monitor for at least two, never with chronic benzodiazepine use or seizures.

13:54In cirrhosis, halve or avoid midazolam and prefer propofol with care for hypotension. Over sixty-five, cut all doses by a quarter to a half, titrate slowly, and plan for falls. In sleep apnea, screen with STOP-BANG, use capnography and airway-trained staff, and use CPAP in recovery. In pregnancy after the first trimester, use full-stomach precautions and a left lateral tilt, prefer propofol, accept low-dose fentanyl, avoid ketamine, monitor the fetus after twenty-two to twenty-four weeks, and defer elective procedures to the second trimester or after delivery.

14:31Episode four is antibiotic prophylaxis, cardiac devices, capsule endoscopy, and grading adverse events.

14:39For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode three of four of chapter twenty-eight, and I'll see you in the next one.