Dexmedetomidine versus remifentanil for sedation during awake intubation using a Shikani optical stylet: a randomized, double-blinded, controlled trial
Xu et al. BMC Anesthesiology
Dexmedetomidine versus remifentanil for sedation during awake intubation using a Shikani optical stylet: a randomized, double-blinded, controlled trial
Ting Xu 0
Min Li 0
Cheng Ni 0
Xiang-yang Guo 0
0 Department of Anesthesiology, Peking University Third Hospital , Beijing 100191 , China
Background: The purpose of this study was to compare the efficacy and safety of dexmedetomidine versus remifentanil for sedation during awake intubation using a Shikani optical stylet (SOS). Methods: Sixty-eight patients with cervical trauma or severe cervical spondylosis undergoing cervical spinal surgery were enrolled in this prospective study. They were randomly assigned to receive dexmedetomidine (Group D) or remifentanil (Group R). In Group D, the patients received an intravenous loading dose of dexmedetomidine 1 μg · kg−1 over 10 min followed by a continuous infusion of 0.7 μg · kg−1 · h−1. In Group R, a target-controlled infusion of remifentanil was administered to achieve a plasma concentration of 2.5 ng · ml−1, increased to 3 ng · ml−1 10 min later. An endotracheal tube was inserted using a SOS under dexmedetomidine or remifentanil sedation after topical anesthesia to the airway. Midazolam was given as rescue sedation. We recorded the first attempt intubation success rate, the dose of midazolam, duration of intubation, Ramsay Sedation Scale (RSS) score, tracheal tube tolerance score, duration of drug infusion, adverse events and patient satisfaction score. Results: The RSS score was significantly higher in Group D than in Group R. First attempt success rate, rescue midazolam dose and the duration of intubation did not differ between the groups. Patients in Group R were significantly more tolerant of the tracheal tube. The incidence of hypoxia was significantly higher in Group R than Group D, but there was no significant difference in the incidence of other adverse events between the groups. The hemodynamic responses of the two groups were similar, but more patients in Group R were able to recall airway instrumentation. Conclusions: Both dexmedetomidine and remifentanil are effective sedatives for awake intubation using an SOS. Although the first attempt success rates were similar, patients sedated with remifentanil tolerated the tracheal tube better after intubation with moderately increased risk of desaturation. Trial registration: www.chictr.org.cn; ChiCTR-TRC-13003052 (February 4th, 2013).
Dexmedetomidine; Remifentanil; Shikani optical stylet; Awake intubation; Sedation
The Shikani optical stylet™ (SOS; Clarus Medical,
Minneapolis, MN, USA) is a rigid but malleable stylet with
fiberoptic rods and a lens. The SOS is an effective means
of managing patients with a difficult airway [
Compared with a Macintosh laryngoscope, use of a SOS
reportedly reduces cervical spine movement during intubation
, suggesting that it might reduce the risk of spinal cord
injury during instrumentation of the airway in patients
with a potential or documented cervical spine injury.
The SOS is most often used to intubate patients under
general anesthesia. Awake intubation using the SOS in a
patient with a difficult airway has been reported in two
]. The best means of providing sedation in awake
SOS intubation has not yet been established. Sedation is
one of the key elements for successful awake intubation.
Intravenous midazolam, propofol and remifentanil are
commonly used as sedatives for awake fiberoptic endoscope
intubation (AFOI), and there have been recent reports of
the safe and effective use of dexmedetomidine [
Dexmedetomidine is a highly selective α2 adrenoceptor agonist
that acts as a sedative, analgesic and a moderate
antisialagogue without respiratory depression, suggesting that it could
be a suitable drug for facilitating awake intubation. Previous
studies have demonstrated that dexmedetomidine is
superior to midazolam [
], fentanyl [
], propofol [
] in AFOI. Two studies compared
dexmedetomidine with remifentanil for AFOI, but their results were
The sedation regimen for AFOI might not be suitable
for awake intubation when a SOS is used instead of a
fiberoptic bronchoscope (FOB), as the two devices have
different characteristics and are manipulated differently.
This study was designed to compare the efficacy and
safety of dexmedetomidine with that of remifentanil
during awake intubation with a SOS.
After institutional ethics committee approval
(IRB000067612012045, Medical Ethics Committee of Peking University
Third Hospital), informed written consent was obtained
from all patients. We enrolled patients between December
2013 and December 2014. Inclusion criteria were: age 18–
70 years; American Society of Anesthesiologists (ASA)
physical status score I–III; requirement for preoperative neck
immobilization with a hard plastic collar; planned urgent or
elective cervical spine surgery for cervical trauma or severe
cervical spondylosis. Exclusion criteria were: pregnancy; use
of an α2 adrenoreceptor agonist or antagonist within the
previous 14 days; known or admitted alcohol or drug
misuse; uncontrolled seizure disorder; history of unstable angina
or myocardial infarction; resting heart rate (HR) <50 min−1;
and complete heart block.
Patients were assigned by a computer-generated
randomization schedule to receive sedation with
dexmedetomidine (Group D) or remifentanil (Group R). A research
nurse generated the allocation sequence, enrolled
participants and assigned them to their groups. While one
anesthesiologist prepared and infused the study drug,
another anesthesiologist experienced in the use of the SOS
was in charge of airway anesthesia and intubation. Another
research nurse assessed the patients, recorded intubation
time and followed up the patients postoperatively. The
participants, the intubating anesthesiologist and the nurse
who was responsible for assessment and follow up were
blinded to the group allocation.
All patients received a bolus of intravenous
scopolamine 0.3 mg as premedication and oxygen by nasal
cannula (3 L · min−1). Vital signs, including systolic blood
pressure (SBP), diastolic blood pressure (DBP), HR and
pulse oxygen saturation (SpO2) were recorded at
baseline and every 2 min until the completion of intubation.
The time required for intubation (from the first insertion
of the SOS to confirming intubation with capnography)
and the number of attempts was also recorded.
All patients received the study drug via an Alaris PK
Syringe Pump (Care Fusion, Becton Dickinson, Franklin
Lakes, NJ). The study drug was diluted to 50 mL with a
0.9 % NaCl solution, and the infusion was started 10 min
before airway anesthesia and continued throughout airway
management and intubation. Group D received a loading
dose of 1.0 μg · kg−1 dexmedetomidine over 10 min
followed by a continuous infusion of 0.7 μg · kg−1 · h−1 [
Group R received a target-controlled infusion of
remifentanil using the Minto three compartment model. The initial
target was set at 2.5 ng · ml−1 and increased to 3 ng · ml−1
10 min later. In both groups, the drug infusion was
continued until confirmation of successful intubation.
During application of topical airway anesthesia and
intubation, the cervical collar was not released. Airway
anesthesia began 10 min after the start of sedative drug
infusion. Lidocaine 200 mg was administered through a
laryngotracheal mucosa atomization device (LMA MADgic,
Teleflex Medical, Athlone, Republic of Ireland) to the
mouth, larynx and glottis.
The application of topical anesthesia to the upper airway
took no less than 10 min. The patient’s sedation level was
assessed using the Ramsay Sedation Scale (RSS) at baseline,
10 min after the drug infusion had started, and every 3 min
during airway anesthesia. Any patient with an RSS <2 was
given a rescue bolus of intravenous midazolam 0.5 mg until
an RSS of 2 was achieved [
A SOS preloaded with an endotracheal tube (ETT)
was inserted over the tongue. The supine patient was
asked to take deep breaths. The epiglottis and the glottic
opening were identified via the eyepiece. Once the vocal
cords were visualized, the tip of the ETT was advanced
during inspiration. After the tip of ETT had entered the
trachea, the SOS was withdrawn. Intubation score was
assessed using a 5-point scale during SOS endoscopy and
intubation (1, no movement; 2, grimacing; 3, mild cough;
4, major limb movement; 5, prolonged coughing) [
the intubation score was >2 during endoscopy, the SOS
was withdrawn and 3 mL 2 % lidocaine was sprayed on to
the glottis via the LMA MADgic. The patient’s sedation
level was reassessed and rescue midazolam 0.5 mg was
given repeatedly in 1-min intervals until RSS ≥2.
The SOS was withdrawn if the patient’s SpO2 was ≤92 %
during endoscopy. Oxygen was given via facemask (5 L ·
min−1) and the patient was instructed to take deep breaths.
When SpO2 recovered to ≥95 %, another intubation
attempt was made.
Immediately after intubation, end tidal CO2
concentration (first breath) was recorded. Tolerance of the ETT
was assessed using a 3-point scale (1, well tolerated and
cooperative; 2, mild coughing and/or grimacing but still
cooperative; 3, severe coughing and/or agitated and not
]. General anesthesia was induced
immediately after assessment of ETT tolerance. Infusion of
the study drug was discontinued upon completion of
induction of general anesthesia.
At the 24-h postoperative follow-up visit, patients were
interviewed to assess their recall of pre-anesthesia events,
administration of topical anesthesia, endoscopy and
intubation, and whether there had been complications (for
example, injury to the teeth, lip or oral mucosa, sore throat
or hoarseness). Patient satisfaction with the whole
procedure was assessed on an 11-point numeric rating scale (0,
completely dissatisfied; 10, completely satisfied).
The primary efficacy endpoint of this study was the
proportion of patients intubated successfully at the first
attempt. Based on the findings of a previous study, in
which the first attempt success rates using
dexmedetomidine versus remifentanil in AFOI were 38 and 76 %
], we calculated that a sample size of 64
patients would be sufficient to detect a difference
between the treatment groups with a power of 0.8 and a
significance level of 0.05. Considering possible 5 %
dropout, the sample size was set at 68.
We used SPSS 13.0 software (SPSS, Chicago, IL) for
statistical analyses. Continuous variables are expressed
as mean ± standard deviation, and were compared within
groups using the paired t-test and between groups using
the independent t-test. The chi-squared test or Fisher’s
exact test were used to compare categorical data
between the groups. Intubation conditions and tolerance
score were analyzed using the independent samples
Mann–Whitney U test. Blood pressure and HR at
different time points were compared using two-way
repeatedmeasures analysis of variance. A P value <0.05 was
regarded as statistically significant.
A total of 70 patients were assessed for eligibility, and 68
patients were enrolled. The enrolled patients were
randomized and all of them completed this study (Fig. 1).
Patients’ demographic and clinical characteristics did not
differ between the groups (Table 1).
The baseline RSS of the two groups were similar (Table 2),
but RSS was significantly higher in Group D than in Group
R 10 min after drug infusion (Table 2, P = 0.001).
All patients were successfully intubated with the SOS.
The first intubation attempt success rates and the need
for rescue midazolam were similar between the groups
(Table 2). In first-time SOS insertions, the intubation
scores of the two groups were broadly comparable. After
intubation, mild coughing was observed in 12 patients in
Group R, compared with 24 patients in Group D (and
one case of severe coughing), resulting in significantly
different tube tolerance scores (P = 0.001). The duration
of drug infusion was 26.0 ± 4.5 versus 24.8 ± 4.0 min in
Groups D and R, respectively (P = 0.247).
Nine patients in Group R and two in Group D developed
hypoxia during intubation. The incidence of hypoxia
(defined as SpO2 ≤ 90 % or a decrease of 10 % below baseline
saturation, with the number of desaturation episodes
measured on a per patient basis) in Group R was significantly
higher than Group D (26 % versus 6 %, P = 0.021). The
lowest SpO2, observed in a patient in Group R, was 85 %. All
patients who developed hypoxia recovered to an SpO2 ≥
95 % within 2 min after administration of supplementary
oxygen by face mask. The hemodynamic changes observed
in both groups were similar (Table 3). There were no
significant differences in the occurrence of hemodynamic
adverse events between the groups from the beginning of
drug infusion until 10 min after intubation (Table 4).
Significantly more patients in Group R recalled airway
management than Group D (Table 2). There were no significant
differences in patient satisfaction (Table 2) or intubation
complications between the two groups (Table 4).
We found that remifentanil and dexmedetomidine are
both suitable for use as sedatives for awake SOS
intubation. Although the first attempt success rates were
similar between the groups, patients sedated with remifentanil
SBP (mmHg) D
tolerated the tracheal tube better after intubation, but at
the expense of a greater risk of mild desaturation.
We selected the dose of the sedative according to
previous studies of AFOI. The loading dose of 1 μg · kg−1
over 10 min followed by a continuous infusion at 0.5–
0.7 μg · kg−1 · h−1 is a standard regime for intraoperative
use of dexmedetomidine, and is most widely reported in
use for dexmedetomidine sedation for AFOI [
A higher dose may cause hypertension [
], while a
lower one may not achieve adequate sedation. The
reported target concentrations of remifentanil for AFOI
9, 10, 23–30
]; in most studies the target effect site
concentration of remifentanil at the time of endotracheal
intubation was 2–4 ng · ml−1 [
9, 10, 23–28, 30
informed our choice of 3 ng · ml−1.
We found that the main differences between the
groups were sedation level and ETT tolerance. The
patients in Group D were more deeply sedated, but
patients in both groups were able to cooperate with the
Data are given as number (proportion, %). Baseline values of systolic blood
pressure (SBP), diastolic blood pressure (DBP) and peripheral oxygen
saturation (SpO2) were used to define adverse events. Hypotension was
defined as SBP <80 mmHg, DBP <50 mmHg or SBP decreased ≤30 % below
baseline values. Hypertension was defined as SBP >180 mmHg, DBP
>100 mmHg or an SBP increased ≥30 % higher than baseline values.
Bradycardia was defined as HR <45 min−1 or a decrease to ≤30 % below
baseline. Tachycardia was defined as HR >120 min−1 or an increased ≥30 %
higher than baseline values. Hypoxia was defined as SpO2 ≤ 90 % or a
decrease by ≥10 % of the baseline saturation
Data are presented as median (minimum, maximum), mean ± standard
deviation or number (proportion, %)
Abbreviations: RSS Ramsey sedation score, PETCO2 % end tidal carbon dioxide
operator during airway anesthesia. There were no
significant differences in the first intubation attempt success
rates or the overall score for intubation conditions at the
first attempt between the groups. After intubation, the
proportion of patients who coughed mildly in Group D
was twice that of Group R. Although patients in Group
D were significantly less likely to tolerate the ETT, there
was nonetheless no difference in the proportion with
hypertension or tachycardia compared with Group R.
The apparent lack of a profound hemodynamic response
to coughing and the higher incidence of bradycardia in
Group D may be explained by the anti-sympathetic
effect of dexmedetomidine.
In contrast, Hu and colleagues found that
dexmedetomidine and remifentanil were both effective in patients
undergoing awake fiberoptic nasotracheal intubation, and
there were no significant differences in intubation or
postintubation scores between those sedated with
dexmedetomidine versus remifentanil [
]. Unlike a flexible FOB, the
SOS is a more rigid rod with limited degrees of freedom.
This difference makes the manipulation of the SOS more
stimulating than a FOB. Additionally, the SOS does not
have a working channel though which local anesthetic can
be administered in a ‘spray-as-you-go’ manner. Although
the vocal cords and the airway above the vocal cords can
be adequately anesthetized through an LMA MADgic,
local anesthetic could not be sprayed into the trachea. The
suppression of the cough reflex after intubation relied
mainly on the analgesic properties of the sedative.
There have been several reports of the use of
dexmedetomidine or remifentanil for AFOI without topical
anesthesia. In one case report, a loading dose of 1.0 μg ·
kg−1 dexmedetomidine followed by an infusion of 0.6 μg ·
kg−1 · h−1 was used as the sole agent for AFIO in a
patient with local anesthetic allergy [
]. The authors
reported that the patient tolerated the procedure well with
minimal discomfort despite the lack of topical anesthesia.
Our findings suggest that for awake SOS intubation a
combination of dexmedetomidine with a more potent
analgesic drug should be considered to achieve better ETT
tolerance. A recent study showed that for AFOI, the use
of dexmedetomidine (1 μg · kg−1 loading dose followed by
an infusion of 0.5 μg · kg−1 · h−1) plus ketamine (15 mg
loading dose and a 20 mg · h−1 continuous infusion)
provided better hemodynamic stability and sedation than
dexmedetomidine alone [
The proportion of patients in our study who
experienced mild or prolonged coughing after intubation was
significantly lower in Group R than Group D. In a
previous study, Song and colleagues used ‘no sustained and
repetitive coughing with head lift’ as the indicator of
suitable sedation conditions for AFIO in patients
undergoing cervical spine surgery [
]. Although in our
study,all patients in Group R met Song’s criteria, a
higher plasma remifentanil concentration might reduce
the incidence of mild coughing further. Vennila and
colleagues used a target controlled infusion of remifentanil
as the sole agent for AFIO without ‘spray-as-you-go’
local anesthesia [
]. The higher mean remifentanil
concentration that they adopted (6.3 ng · ml−1 at nasal
endoscopy, and 8.06 ng · ml−1 during tracheal intubation)
was shown to be safe. Although in the present study,
Group R had a higher incidence of hypoxia, the degree
of hypoxia was modest—the lowest SpO2 was 85 % in
one patient. Hypoxia was successfully addressed within
2 min in all patients who desaturated. The majority of
patients who developed desaturation in both groups had
a history of smoking or pulmonary disease, or a BMI
>30 kg · m−2. Caution should be exercised when
administering sedation in such patients.
We found that the proportion of patients who recalled
airway management was higher in the remifentanil group
than the dexmedetomidine group. This finding chimes with
those of previous studies, which have reported that
dexmedetomidine has a stronger amnesic effect than
]. Although the recall rate was higher in
Group R, most patients did not find the experience
unpleasant, reflected in broadly comparable patient
satisfaction scores. Although no dental injuries were reported in
our study, there was a high incidence of sore throat in both
groups (47.1 % versus 52.9 %, P = 0.628), which may have
been a consequence of surgery rather than airway
instrumentation. It has previously been reported that the
incidence of sore throat was as high as 51–74 % in patients
undergoing cervical spine surgery .
Our study had some limitations. First, the sample size
in each group was 34 and the primary endpoint was
first-attempt intubation success rate. These were 79.4
and 85.3 % in each group, meaning that the risk of a
statistical type II error was 0.88. Therefore, further larger
samples studies will be needed to confirm our results.
Second, there was also a relatively high chance that our
sample size was inadequate to detect intergroup
differences for uncommon adverse events (e.g., lip or teeth
injuries, complications associated with oxygen desaturation
events, etc.). Finally, our results cannot be extrapolated to
settings where target-controlled infusion of remifentanil is
Dexmedetomidine and remifentanil are effective sedatives
for awake intubation using the SOS. Although the
firstattempt success rates were similar between the two groups,
patients sedated with remifentanil tolerated the ETT better
at the expense of an increased risk of mild hypoxia.
AFOI, awake fiberoptic endoscope intubation; DBP, diastolic blood pressure;
ETT, endotracheal tube; FOB, fiberoptic endoscope; HR, heart rate; RSS,
Ramsay Sedation Scale; SBP, systolic blood pressure; SOS, Shikani optical
stylet; TCI, target controlled infusion
We sincerely thank all the staff of the Anesthesiology Department of Peking
university third hospital for their help in this research.
Availability of data and materials
The data during this study are available from the corresponding author on
All authors have made substantive intellectual contributions to the manuscript.
ML and TX designed the study. TX and CN were responsible for conducting the
study and analyzing the data. ML, TX and CN wrote the manuscript. XG
participated in study design and revised the manuscript. All authors
have seen the original study data, reviewed the data analysis and
approved the final manuscript.
The authors declare that they have no competing interests.
Consent for publication
Written informed consent was obtained from the patient for publication of
the Fig. 2c in this article.
Ethics approval and consent to participate
The study was approved by Peking university third hospital medical ethics
committee and each participant provided written informed consent.
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