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Moderate Sedation or Monitored Anesthesia Care
for Colonoscopies: Is There a Difference?
MATTHEW NG, M.D., RAHIM DHANANI, M.S., HADIZA GALADIMA, PH.D., JESSICA BURGESS, M.D.
From the Eastern Virginia Medical School, Norfolk, Virginia
To determine whether monitored anesthesia care (MAC) results in shorter colonoscopy time. A
retrospective chart review from electronic medical records at Sentara Norfolk General Hospital
was performed of all patients seen by the Eastern Virginia Medical School Department of Surgery
who underwent a screening or diagnostic colonoscopy from December 2015 to July 2017. The
primary end point is procedure time, with secondary end point of sedation time. There is a sta-
tistically significant difference in time to cecum between moderate sedation (MOD) and MAC
(P50.002). Operator perceived difficulty is statistically associated with increased time to cecum
(P<0.0001). Time to cecum between MOD and MAC over the levels of difficulty was not sig-
nificant (P50.403). A subanalysis looking at time to cecum between MOD and MAC for each
level of difficulty showed a significant effect when difficulty was described as no difficulty. There
is a statistically significant difference in time to scope insertion between MOD and MAC (P<
0.0001). Our data show that, taken as a conglomerate, the procedure and sedation time is shorter in
MAC than in MOD. The use of MAC is associated with decrease time to scope insertion and
overall time to cecum.
THE UNITED STATES Preventative Task Force rec-
ommends screening for colorectal cancer with
colonoscopy, starting at the age of 50.
1
A colonoscopy
can be an uncomfortable experience for the patient.
Traditionally, a colonoscopy is performed with mod-
erate sedation (MOD), administered by the endo-
scopist. Recently, with the growing trend for a painless
procedure, monitored anesthesia care (MAC) has
been introduced. This entails an independent oper-
ator trained in anesthesia to provide sedation, at this
institution, propofol. The hypothesis queries whether
MAC provides a better procedure for the patient and
whether it is worth the extra costs.
Traditionally, MOD describes a state of conscious
sedation for the patient. It is a pharmacologic induced
depressed state in that the patient is still conscious, but
they are able to tolerate unpleasant stimuli. They are
able to respond to verbal or light tactile stimuli. The
patients continue to maintain their cardiovascular sta-
tus.
2
A common regimen is fentanyl and midazolam. A
bolus dose of fentanyl and midazolam is given and the
patient’s response is assessed in interval time.
3
Another form of sedation is MAC (also known as
deep sedation) which is commonly used in endoscopic
procedures. Propofol is routinely used and adminis-
tered by an anesthesia provider (certified registered
nurse anesthetist or anesthesiologist). The patients
continue to manage their own airway and respond to
repeated or painful stimuli. Similarly, they are able to
maintain their cardiovascular status.
4
At our institution, our surgeons perform colo-
noscopies using both types of sedation. Perceived
difficulty, prior colonoscopies, costs, and attending
preference drive decision-making for selecting se-
dation. This study aims to determine whether MAC
results in shorter procedure time.
Methods
A retrospective chart review from electronic medical
records at Sentara Norfolk General Hospital was per-
formed on all patients who underwent a screening or
diagnostic colonoscopy by the Eastern Virginia Med-
ical School Department of Surgery from December
2015 to July 2017. The primary end point is procedure
time, with the secondary end point being sedation time.
Data abstracted from chart reviews of patients who
underwent colonoscopy are the basis of this study. The
major variables being abstracted for this study are as
follows: age, time to cecum, difficulty of procedure as
documented by the surgeon (no difficulty, moderate
difficulty, and extremely difficult), and the American
Society of Anesthesiologist (ASA) score.
The inclusion criteria included patients aged 18 to
90 years undergoing screening or diagnostic colonos-
copy with an adequate bowel prep to evaluate for
Address correspondence and reprint requests to Matthew Ng,
M.D., Eastern Virginia Medical School, 825 Fairfax Avenue, 6th
Floor Norfolk, VA 23507. E-mail: ngm@evms.edu.
1284
polyps. These patients must have received either MOD
or MAC. Patients were excluded because of incom-
plete dictation.
Statistical Analysis
Patient demographics were summarized and tested
for differences between MOD and MAC using the ttest
for continuous variables after verifying normality of
data with the normal probability plot, and the chi-
square test for categorical variables. The normal data
were summarized as mean ± standard deviation and the
categorical variables as frequency (%). Differences
between MOD and MAC in terms of time to cecum and
time to scope insertion were tested using the non-
parametric Kruskal-Wallis test. A multiple linear re-
gression was used to assess the impact of ASA, body
mass index (BMI), and level of difficulty on time to
cecum. A two-way analysis of variance was used to
compare the time to cecum between MAC and MOD
over the levels of difficulty. All analyses were con-
ducted using SAS v9.4 (SAS Institute, Cary, NC). All
tests were considered statistically significant if the
Pvalue is less than 0.05. Statistics were provided by
the Eastern Virginia Medical School Center for Health
Analytics and Discovery.
Results
From December 2015 to July 2017, we identified
361 patients to be included in our study; 48 patients
were excluded. Of the 361 patients, 200 underwent
MAC and 161 had MOD. The characteristics of the
patients are identified in Table 1. The only signifi-
cant difference between the two groups is ASA
score. Patients undergoing MOD tended to have
lower ASA scores; ASA scores one (13 vs 1) and
two (130 vs 76), whereas higher scores for MAC,
ASA three (120 vs 18) and four (3 vs 0). There was
no difference in age (MAC: 57.91, MOD: 57.03),
BMI (MAC: 31.69, MOD: 30.56), gender (MAC:
female 114, male 86, MOD: female 78, male 83), or
perceived difficulty.
There is a statistically significant difference in time
to cecum between MOD and MAC (P40.002).
Median time for MAC is 17 minutes. It is statistically
lower than the median time in MOD of 21 minutes
(Table 2).
A subgroup analysis was performed to determine
whether ASA, BMI, or perceived level of difficulty
influenced time to cecum. Surgeon perceived diffi-
culty is statistically associated with a lower time to
cecum (P< 0.0001). ASA (P40.3515) and BMI
(P40.5029) did not affect time to cecum (Table 3).
As part of our standard documentation, surgeons
comment on their perceived difficulty of the proce-
dure. Using a numerical scale, 0 represents no diffi-
culty, 1 represents moderate difficulty, and 2 represents
extremely difficult. When colonoscopies were con-
sidered not difficult, the procedure time was statisti-
cally shorter for MAC (17 vs 21 minutes, P< 0.05).
TABLE 1. Patient Demographics
Demographic Characteristics MAC (n 4200) MOD (n 4161) PValue
Age (mean ± SD) 57.91 ± 9.34 57.03 ± 8.89 0.367
BMI (mean ± SD) 31.69 ± 8.68 30.56 ± 7.14 0.185
Gender
Female 114 (57%) 78 (48.45%) 0.1055
Male 86 (43%) 83 (51.55%)
ASA <0.0001
1 1 (0.5%) 13 (8.07%)
2 76 (38%) 130 (80.75%)
3 120 (60%) 18 (11.18%)
4 3 (1.5%) 0 (0%)
Difficulty 0.4479
0 144 (72%) 109 (67.7%)
1 33 (16.5%) 35 (21.74%)
2 23 (11.5%) 17 (10.56%)
SD 4standard deviation.
04perceived as no difficulty.
14perceived as some difficulty.
24perceived as extremely difficult.
TABLE 2. Time to Cecum between MOD and MAC
Variable MAC (n 4200) MOD (n 4161) Chi-Square Df PValue
Time to cecum, median (min – max) 17 (3–70) 21 (7–95) 14.08 1 0.0002
No. 8 MOD OR MAC FOR COLONOSCOPIES ?Ng et al. 1285
There is no statistically significant difference in time
to cecum between MAC and MOD when difficulty is
considered moderate or extremity difficult (Table 4).
There is a statistically significant difference in time to
scope insertion between MOD and MAC (2.95 vs 5
minutes, P< 0.0001). This is the time period between
when the procedural time-out is performed and when
the patient is considered adequately sedated and the
scope inserted (Table 5).
Discussion
Our data show that taken as a conglomerate, the
procedure and sedation time is faster in MAC than in
MOD. With the rising costs of health care, it is im-
portant to be cognizant of extra expenditures on pro-
cedures while maximizing patient safety. However,
when looking at the level of difficulty for the pro-
cedure, there was no difference in time for moderately
and extremely difficult procedures. MAC results in
faster colonoscopies and also decreases induction
time. Induction of propofol is faster than that of fen-
tanyl and versed to achieve a level of sedation suitable
for colonoscopy. Patients were also more deeply se-
dated with propofol.
5
Similar to the study conducted by Ulmer et al., MAC
resulted in shorter procedure times, although their
study only recruited patients with ASA score 1 or 2.
They noted that the overall procedure length including
time to discharge was on average 15 minutes shorter
than that in MOD.
5
Further investigation delineating between screening
and diagnostic colonoscopies is needed. Unsurpris-
ingly, the only predicting variable of procedure time is
difficulty score. At no difficulty, the MAC group was
quicker. As the procedure became more difficult, no
statistically significant difference was seen. Perhaps,
this is because of the patient already at such a deep
level of sedation on MAC or MOD to allow for the
more complex procedure. The weaknesses of the study
include a small sample size. Because the cohort is
small, it is difficult to conclude that the differences are
real. Another confounding variable is due to a variety
of different level residents performing the procedure
and it is difficult to ascertain their involvement.
We believe that our data are supportive of using
MAC for colonoscopies. It allows for a faster proce-
dure and provides another qualified health professional
administering sedation and monitoring airway so the
surgeon can focus solely on the procedure. Further
analysis is needed, including level resident involve-
ment, postprocedure recovery, patient satisfaction, and
costs.
REFERENCES
1. US Preventative Services Task Force. Screening for co-
lorectal cancer US Preventive Services Task Force recommenda-
tion statement. JAMA 2016;315:2564–75.
TABLE 3. ASA, BMI, and Level of Difficulty Influence Time to Cecum
Parameter Estimates
Variable Label Df Parameter Estimate Standard Error tValue PValue
Intercept Intercept 1 22.59012 2.93884 7.69 <0.0001
ASA ASA 1 –0.93244 0.99944 –0.93 0.3515
BMI BMI 1 –0.04759 0.07097 –0.67 0.5029
Difficulty Difficulty 1 7.73279 0.81754 9.46 <0.0001
TABLE 4. Time to Cecum Based on Perceived Difficulty Level
Time to Cecum between MAC and MOD across Difficulty Levels
Difficulty 40 Difficulty 41 Difficulty 42
Sedation Mean PValue Mean PValue Mean PValue
MAC 17.299 0.0012 24.788 0.8238 32.565 0.0714
MOD 21.431 25.371 39.824
Difference (MAC – MOD) –4.133 –0.584 –7.258
TABLE 5. Time of Sedation before Procedure Starts
Variable MAC (n 4200) MOD (n 4161) Chi-Square Df PValue
Time to scope insertion 2.95 (1–14.82) 5 (0–26.77) 119.46 1 <0.0001
THE AMERICAN SURGEON August 20181286 Vol. 84
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3. McQuaid KR, Laine L. A systematic review and meta-
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routine endoscopic procedures. Gastrointest Endosc 2008;67:
910–23.
4. Faigel DO, Baron TH, Goldstein JL, et al. Guidelines for the
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5. Ulmer BJ, Hansen JJ, Overley CA, et al. Propofol versus
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No. 8 MOD OR MAC FOR COLONOSCOPIES ?Ng et al. 1287
