Background
Endotracheal intubation has been shown to cause signifi-
cant physiological, pharmacokinetic, and dynamic changes,
along with postoperative respiratory complications in pa-
tients under general anesthesia [1]. Transient hemodynamic
changes during these periods increase myocardial oxygen
consumption, leading to myocardial ischemia. This can in-
crease the risk of cardiovascular and cerebrovascular dis-
eases, and of morbidity and mortality, in older patients
under general anesthesia. Stellate ganglion block can re-
strain the stress response from inducing anesthesia and
endotracheal intubations [2]. Several alternative approaches
to mitigating this response have also been reported, such as
the administr ation of esmolol, labetalol, nitroglycerin, cloni-
dineare, and lidocaine [3–7]. However, stellate ganglion
blocks are invasive and the alternative approaches are not
always satisfactory.
Lidocaine/prilocaine cream (a eutectic mixture of lido-
caine 25 mg/mL and prilocaine 25 mg/mL) is widely
used as a topical anesthetic [ 8–11]. To our knowledge,
however, no high quality randomized con trolled study
has been conducted to investigate the use of lidocaine/
prilocaine cream to prevent cardiovascular stress re-
sponses in older patients undergoing tracheal intubation
under general anesthesia. Our central hypothesis is that
lidocaine/prilocaine can be used substantially in tracheal
intubation of older patients under general anesthesia.
The purpose of our study was to carry out an RCT trial
on this application. The results offer accurate evidence
for the local use of lidocaine/prilocaine cream in tracheal
intubation of older patients under general anesthesia, to
facilitate the postoperative rehabilitation and quality of
life of these patients.
Methods
Trial design
The RCT trial was organized by the Third Affiliated
Hospital at Sun Yat-sen University, China. The trial was
conducted according to the CONSORT-2010 guidelines.
The study was approved by the Review Board of the
Third Affilia ted Hospital at Sun Yet-sen University
([2013]2–85). All subjects provided written informed
consent before the trial. Underlying data are available in
accordance with the Management of Human Genetic
Resources in China.
Participants and setting
Patients were included in the trial if they were over 60
years old and scheduled for upper abdominal surgery
under general anesthesia using endotracheal tube intub-
ation from August 2015 through December 2018. The
major exclusion criteria were the following: allergies to
lidocaine, prilocaine, or any other ingredients in the test
product; ischemic heart disease or advanced chronic
kidney disease; younger than 60 years old; American
Society of Anesthesiologists (ASA ) Grade IV. We ran-
domly assigned old er patients t o either lidoca ine/prilo-
caine cream treatment or a placebo (Vaseline) at a 1:1
ratio. The primary end point included cardiovascular
reactions during the induction of a nesthesia, along with
endotracheal intubations a nd cough e vents during the
recovery per iod. Figure 1 shows a flowchart for the as-
signment of participants in the study.
Intervention
Nurses inflated the endotracheal tube. According to the
random number table, in the test group, off-label use of
2 g of lidocaine/prilocaine cream (and in the control
group, 2 g of Vaseline cream) were laid over the surface
of the tracheal tube cuff. After ventilation, the anesthesi-
ologists placed the endotracheal tube and fixed the
endotracheal tube with air. Both the patients and the in-
vestigators were unaware of the trial-group assignments.
Before tracheal intubation, anesthetics was used and un-
conscious intub ation was carried out. The depth of
anesthesia was measured by the bispectral index (BIS).
Fentanyl was used as the induction agent according to
the sex, weight, and ASA rating of the patients. Benzene
sulfuro acted as the muscle relaxant and its dosage was
based on the weight and situation of the patients during
the operation.
Parameter measurement
Cardiovascular reaction during the induction of anesthesia:
systolic blood pressure (SBP) (mm Hg), diastolic blood
pressure (DBP) (mm Hg), heart rate (HR) (beats/min), and
cough reaction. Coughing that occurred during extubation
was defined as induced cough. The SBP, DBP, and HR were
measured with a monitor.
Sample size calculation
According to the pret est analysis of 10 patients in each
group, we set α = 0.05 and β = 0.20, with a sample drop
rate of 20%. Using Open Epi Version 2 [12 ], we calcu-
lated the minimum sample size of 125 cases in each
group (a total of 250 cases).
Statistical analysis
The measurements were calcu lated as the mean (±
standard deviation). An independent t-test was used to
compare the groups. Further, a chi-squared test was
used to compare the categorized data in the groups. An
analysis of variance of the repeated measurement data
was conducted to compare the data. We set p < 0.05 as
statistically significant. R version 3.0.2 was used to
process the data.
Lv et al. BMC Geriatrics (2020) 20:157 Page 2 of 5