OVERVIEW OF MODERATE SEDATION
Among the diagnostic procedures for which moderate sedation
is most commonly used are routine endoscopic examinations, the number of which has escalated
because of their value in colorectal cancer screening [23]. According to a 2006 survey of American Society for Gastrointestinal
Endoscopy (ASGE) members, 45% of the 724 respondents did not routinely offer unsedated
endoscopic procedures and more than 70% said they would choose to be sedated for a routine
endoscopic procedure [23]. In a more recent
survey of American College of Gastroenterology (ACG) physician members, more than 98% of
1,353 respondents said they used sedation during their endoscopic procedures [24]. People scheduled for endoscopic procedures
have come to expect sedation; in the ASGE survey, lack of patient acceptance was the most
common reason given for not offering unsedated endoscopy [23].
OVERVIEW OF MODERATE SEDATION
In their guidelines on moderate sedation for endoscopy, the
AGA Institute and the ASGE follow the ASA guidelines and recommend that the use of an
anesthesia professional be strongly considered for patients classified as having ASA
physical status IV or V [28,31]. In addition, several other patient-related
and procedure-related factors are "possible indications" for an anesthesia specialist,
including a history of alcohol or substance abuse, morbid obesity, neurologic disorders, and
complex therapeutic procedures [28,31]. The ACEP guidelines note that there are no
specific level A or B recommendations regarding personnel requirements needed to provide
procedural sedation and analgesia in the emergency department. However, the guidelines state
that a "nurse or other qualified individual" should be present during procedural sedation
and analgesia for continuous monitoring of the patient in addition to the provider
performing the procedure (level C recommendation) [7]. The guidelines also state that emergency physicians working or
consulting in the emergency department should coordinate procedures that require
administration of procedural sedation and analgesia [7]. All clinicians providing moderate sedation must be trained to
administer drugs to achieve a desired level of sedation, monitor patients and maintain a
desired level of sedation, and manage complications [7]. In 2011, the ACEP published comprehensive recommendations for physician
credentialing, privileging, and practice; the ACEP also strongly supports the administration
of propofol, ketamine, and other sedatives by qualified emergency department nurses under
the direct supervision of a privileged emergency physician [7,33]. The AAP guidelines
note similar requirements for training and add that clinicians must have training in how to
oxygenate a child in whom airway obstruction or apnea develops and in advanced pediatric
airway skills [13].
PATIENT ASSESSMENT AND MONITORING
The guidelines agree that routine laboratory or other
diagnostic testing is not needed before moderate sedation [7,11,31]. However, if the
results of testing may affect the management of sedation, such testing should be done
before the patient is sedated [7,11,31].
PATIENT ASSESSMENT AND MONITORING
A noninvasive method of assessing the level of
consciousness is bispectral index (BIS) monitoring, which has been used since the
mid-1990s in the setting of general anesthesia. BIS records electroencephalographic (EEG)
waveforms from a probe adhered to the forehead, and the EEG recording is analyzed with an
algorithm to generate a score on a scale of 0 to 100. EEG activity is a sensitive measure
of sedation, with a low-amplitude, high-frequency signal representing the awake state and
a high-amplitude, low-frequency signal representing sedation. BIS monitoring is helpful in
ensuring that patients are not oversedated or undersedated, and research has shown that
BIS results correlate with validated sedation scales. The ASA guideline does not mention
BIS explicitly and notes that although monitoring of the level of consciousness reduces
the risk of deep sedation, no data have shown that such monitoring improves outcomes [11]. The ACEP and the ASGE found insufficient
or poor evidence to recommend the routine use of BIS [31,69]. The AAP
recommends against the routine use of BIS monitoring in children [13].
Recommendations about noninvasive monitoring of end-tidal
carbon dioxide with capnography have evolved. At the time of their guidelines on
monitoring during moderate sedation, the ASA and the AGA Institute found insufficient
evidence to recommend the routine use of capnography, and the ASA only recommended
capnography during moderate sedation when ventilation could not be directly observed. The
ACEP noted only that procedural monitoring "may include" capnography, and the ASGE stated
that capnography may improve patient safety [7,11,28,31]. However, since the publication of those guidelines, several studies
have demonstrated that capnography readings are a more sensitive measure of ventilatory
function, detecting hypoventilation earlier than changes in vital signs, clinical
observations, or pulse oximetry [70,71,72,73]. In a study in the
emergency department setting, capnography had a sensitivity of 100% (and specificity of
64%) in detecting hypoxia before onset [72]. In addition, a meta-analysis (five studies) demonstrated that respiratory depression
was more than 17 times more likely to be detected during procedural sedation when
capnography was used than when it was not used [73]. In 2010, the ASA issued standards for anesthetic monitoring
(reaffirmed in 2020) stating that monitoring for the presence of exhaled carbon dioxide
should be carried out during moderate (or deep) sedation. This is supported in the 2018
ASGE guidelines [31,74]. In 2018, the ASA issued updated
guidelines for moderate procedural sedation that include a new recommendation for
continual monitoring with capnography to supplement observation and pulse oximetry [11]. Use of capnography during sedation is
also recommended by the Emergency Nurses Association, and, in a joint position statement,
the ASGE, the AASLD, the ACG, and the AGA Institute acknowledge that capnography reduces
the occurrence of apnea and hypoxemia during gastrointestinal endoscopy with propofol
sedation [41,75]. A multisociety-developed curriculum on
sedation during gastrointestinal endoscopy notes that proper training should include
interpretation of capnography readings [69].
The routine use of supplemental oxygen has also been
debated. The ASA and ASGE guidelines note that supplemental oxygen should be considered
for moderate sedation, and the ASGE states that supplemental oxygen can reduce the
magnitude of oxygen desaturation during sedated endoscopy [11,31]. The ASGE additionally states that supplemental oxygen should be
administered if hypoxemia is anticipated or develops [31]. However, the AGA Institute asserts that there is little evidence to
indicate that the use of supplemental oxygen reduces the incidence of significant
cardiopulmonary complications in patients monitored with pulse oximetry [28]. In addition, the results of several
studies have shown that supplemental oxygen may actually increase the rate of
complications associated with sedation, as its use may delay recognition of hypoxemia and
apnea [76,77]. As a result, the AGA Institute
recommends the use of supplemental oxygen during endoscopy only for older individuals and
people with significant comorbid disease (ASA class IV and V) [28]. According to one survey, approximately
73% of endoscopists routinely use supplemental oxygen [24].
There is no evidence to indicate that continuous
electrocardiography (ECG) monitoring is of benefit during moderate sedation, especially
for patients who have no underlying cardiopulmonary disease [7]. Guidelines from the ASA, the AGA
Institute, and the ASGE all note that ECG monitoring is not needed for low-risk patients
[11,28,31]. The ASA
guidelines suggest ECG monitoring to decrease risks for patients who have significant
cardiovascular disease or dysrhythmia, and the AGA Institute and the ASGE state that ECG
monitoring should be considered for high-risk patients, such as patients with a history of
significant cardiac or pulmonary disease [11,28,31]. The AAP recommends that an ECG monitor
and defibrillator be readily available [13].
PATIENT ASSESSMENT AND MONITORING
Scoring systems for anesthesia recovery are available, but no
evidence has established standard discharge criteria; healthcare facilities should establish
their own standardized criteria [11,13,28,31]. In general, the
following parameters are used to indicate that a patient can be discharged: stable vital
signs, alert and oriented status, patent airway, good skin color and condition, minimal
nausea and vomiting, adequate pain control, ability to walk without dizziness, and ability
to dress independently [11,28]. Many facilities have eliminated criteria
related to the ability to eat or drink or void before discharge [28,78]. If a reversal agent has been used, the patient should be observed for
two hours after the agent was given to ensure that he or she will not become re-sedated
after the effects of the reversal agent wear off [11].
MOST COMMONLY USED DRUGS FOR MODERATE SEDATION
Potential Adverse Events and Side
Effects. Respiratory depression may occur, but myoclonus is the most common
side effect, reported in 20% to 45% of patients during procedural sedation. In one small
study, myoclonus occurred in 72% of patients receiving etomidate [81,90,92,93]. There are protocols for minimizing
myoclonus, including pretreatment with a fraction dose of etomidate or a small dose of a
short-acting benzodiazepine. Pain at the injection site has also been common, occurring in
up to 40% of patients [81]. Nausea and
vomiting during emergence have also been reported at low rates [83,90].
MOST COMMONLY USED DRUGS FOR MODERATE SEDATION
Meperidine is contraindicated for patients taking an MAO
inhibitor, as life-threatening complications may develop from the interaction of these two
drugs [28]. The drug should be used with
caution in patients with renal disease because the accumulation of normeperidine can lead
to a neurotoxic reaction [69].
MOST COMMONLY USED DRUGS FOR MODERATE SEDATION
Absolute contraindications for ketamine include an age
younger than 3 months (because of the high risk of airway-related complications) and known
or suspected schizophrenia [79,96]. Relative contraindications include major
procedures that stimulate the posterior pharynx; a history of airway instability; active
pulmonary infection or disease; significant cardiac arrhythmia, coronary artery disease,
or hypertension; CNS abnormalities; glaucoma or acute globe injury; and thyroid disorders
[96]. Head trauma, minor oropharyngeal
procedures, and an age of 3 to 12 months are no longer contraindications [96].
MOST COMMONLY USED DRUGS FOR MODERATE SEDATION
The ASA recommends that, whenever possible, antagonists
should be on hand during the use of moderate sedation [11]. Antagonists are available to reverse the effects of opioids and
benzodiazepines, but as yet no antagonist agents exist for propofol, etomidate, or
barbiturates [69]. Naloxone hydrochloride
can be used to reverse the effect of opioids, and flumazenil (Romazicon) can reverse the
effects of benzodiazepines (Table 12) [28,69].
COMPARISON OF MODERATE SEDATION DRUGS IN SPECIFIC SETTINGS
Data on sedation for children and adolescents undergoing
endoscopy are limited. The authors of a systematic review published in 2012 (11 randomized
and 15 nonrandomized controlled trials) targeted studies involving children and
adolescents younger than 18 years of age [106]. Few of the trials compared different drugs, but the review
demonstrated that propofol-based sedation had a safety profile similar to that of an
opioid and benzodiazepine [106]. Data on
midazolam- and ketamine-based sedation were too limited to draw conclusions. Sedation was
most effective with propofol; the authors noted that adding midazolam, fentanyl, or
ketamine to propofol may enhance the effectiveness without increasing adverse events [106].
MANAGEMENT OF COMPLICATIONS
Knowledge and skill in managing potential complications of
moderate sedation is essential. Most complications occur because of sedation becoming deeper
than intended (rather than not reaching adequate sedation) [11]. This is especially important for children, as studies have indicated that
children often reach a level of sedation that is deeper than intended [13]. Clinicians who administer moderate sedation
must be qualified to rescue patients who reach a deep level of sedation [11].
LEGAL/RISK MANAGEMENT ISSUES
Determining the number of malpractice claims related to the
use of moderate sedation is difficult. It has been estimated that approximately one in every
500 malpractice claims involves complications related to endoscopic sedation [28]. (Data on claims related to sedation in the
emergency department setting are not available.) Potential legal issues related to moderate
sedation are associated with a failure to administer sedation according to the standard of
care, failure to obtain appropriate informed consent, and the patient's discharge status [28,133]. In addition, patient expectation of pain-free procedures may increase the
risk of malpractice claims for two reasons: patients' claims of inadequate sedation, and
oversedation as a way to ensure a pain-free status [28]. Some key measures can help clinicians reduce their risk of malpractice
related to moderate sedation (Table 18) [134]. All clinicians should discuss the
possibility that the patient may have pain or discomfort despite appropriate sedation [28]. The discussion about sedation should also
note that the patient may not remember the procedure and postprocedure discussion and that
there is a risk for allergic drug reactions and local reactions at the IV site [28]. The discussion of these points should be
carefully documented to provide proof in the event of legal action. The preprocedure
discussion should also address informed consent, as outlined previously.
