Vol.3, No.10, 623-625 (2011)
doi:10.4236/health.2011.310105
C
opyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/HEALTH/
Health
Comparison of postoperative sore throat following
laryngoscopy conducted by Miller and Macintosh
laryngoscope blades
Khosro Barkhordari, F arhad Ete zadi, R eza Shariat Mo harari , Mohammad Re za Khaj avi*
Tehran University of Medical Sciences, Sina Hospital, Tehran, Iran; *Corresponding author:
Received 6 January 2011; revised 1 June 2011; accepted 15 June 2011.
ABSTRACT
BACKGROUN D: Post operative sore throat (PST)
is one of the most common complaints after
tracheal intubation. In this study we compared
the effects of curved and straight laryngoscope
blades on severity and incidence of PST. METH-
OD: In this prospective randomized clinical trial
we evaluated incidence and severity of PST in
147 ASA physical status I–II, aged 18 – 62 y
(group Miller, n = 71), (group Macintosh, n = 76)
following intubation with Miller and Macintosh
laryngoscope blades by using Visual Analog
Scale (VAS). RESULTS: The overall incidence of
PST in our study was 35.4% (Macintosh group =
39.5% and in Miller group = 31% and P = 0.829).
The incidence of PST was not statistically differ-
ent between two kinds of laryngoscope blades
and the mean rank of pain score was not statisti-
cally different in recovery room and up to 48
hours after surgery. CONCLUSIONS: Our study
showed these types of laryngoscope blade had
not association with incidence and severity of
PST.
Keywords: Post Operative Sore Throat;
Tracheal Incubation; Laryngoscope Blades
1. INTRODUCTION
Post operative sore throat (PST) is one of the most
frequent complaints after tracheal intubation and its in-
cidence varies between 14% - 50% [1-4]. Mucosal injury,
stretch of ligaments and muscles of throat, prolonged
surgery, changing position of patients during surgery
have been implicated in the pathogenesis of PST [4].
Chandler’s study showed that pressure trauma is very
important to induce PST and he found an association
between mechanical forces and PST [4].
Our hypothesis was that straight blade (Miller) gener-
ates less pressure on pharyngeal wall, muscles and liga-
ments of pharynx than curved blade (Macintosh). Hast-
ings et al showed that the use of Miller laryngoscope
blade required less force and head extension than Mac-
intosh one [5]. We didn’t find any study comparing se-
verity of pain produced by these two common blades
used for laryngoscopy.
The aim of our study was to compare the incidence
and severity of PST with Macintosh and Miller laryngo-
scope blades during normal intubating attempts.
2. METHODS
After Institutional Ethics Committee app roval, written
informed consent was obtained for all patients. We pro-
spectively studied 147 consecutive adult patients (18 -
64 years old) with ASA physical status I–II receiving
general anesthesia with tracheal intu bation. Using a com-
puter generated sequence of numbers, patients were
randomly allocated to be in tubated using either a straight
blade laryngoscope (n = 71) or a curved blade, (n = 76).
Failure to tracheal intubation in the first attempt, posi-
tive history of sore throat, use of NSAIDS, head and
neck surgery, smoking, Mallampati class greater than 2
were our exclusions criteria. After establishing IV access
and use of standard monitoring, midazolam 0.05 mg/kg,
fentanyl 2 µg/kg injected as premedication, thiopental
Na 5 mg/kg, and atracurium 0.4 mg/kg were used for
induction of anesthesia. An anesthesiologist with three
years of continuous practice performed all endotracheal
intubation gently. Size of tracheal tubes were adjusted
for age and body size of patients, and miller no 2 and
Macintosh no 3 blades were used. Endotracheal tubes
(ETT) were lubricated with sterile water. ETT cuffs were
inflated at the safe occlusive volume so initial Cuff
pressure was fixed at 20 cm H2O (Mallinckrodt, Seel-
scherf 1, Germany). Anesthesia was maintained by: air/
N2O (50%/50%), isoflurane (1% to 1.2%) a nd inter mittent
injection of fentanyl as was necessary.
When tracheal extubation criteria were met (return of
neuromuscular function confirmed using train-of-four

K. Barkhordari et al. / Health 3 (2011) 623-625
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/HEALTH/
624
peripheral nerve stimulation, ability to follow verbal
commands, r egular spontaneou s ventilation), tracheal ex-
tubation was performed just after gentle suctioning at the
discretion of anesthesiologist who was a member of an-
esthesia team. Another anesthesiologist who was blin-
ded to the study evaluated th e PST w ith a Visual Analog
Scale (VAS, 0 - 10 score) in the postoperative period (at
0, 3, 6, 12, 24 and 48 hours after surgery). Sample-size
was calculated based on our pilot stud y with 70 patients.
In order to permit 5% of type 1 error enrollment of 73
patients in each group was required. Demographic char-
acteristics and incidence of pain in both groups were
com- pared by using chi-square and Student’s t-test. VAS
scores were analyzed using Wilcoxon rank sum test.
Medians and their confidence intervals were calculated
using binomial interpretation. Statistical sign ificance was
defined as P < 0.05. Data were analyzed using SPSS
version 13 and Intercooled STATA version 9.1.
3. RESULTS
One Hundred Forty Seven patients were enrolled in
the study. Two cases in Miller group were exclud ed from
the study because first intubation attempt was failed. At
the baseline, there were no statistically significant dif-
ferences between groups regar ding sex , age, Mall ampatti
class, and ASA class and operation time between two
groups (Table 1). The overall incidence of PST in our
study was 35.4% (Macintosh group = 39.5% and in
Miller group = 31% and P = 0.829) and the highest mean
VAS score was observed at third post operative hour in
both groups (Figure 1).
The assumption for performing parametric test did not
met; therefore we used Wilcox, rank sum test to compare
VAS scores in the study groups. The assumption for per-
Table 1. Patient characteristics and demographic data.
Group A: Macintosh
blade (n = 76) Group B: Miller blade (n = 71) P value
Sex; n (%)
Male 26 (34.2%) 19 (27.7%) P = 0.33
Female 50 (66%) 52 (73.2%)
Mallampatti
class n (%)
I 74 (97.3%) 70 (98.6%) P = 0.33
II 2 (2.7%) 1(1.4%)
ASA class
I 71 (93.4%) 69 (97%) P = 0.74
II 5 (6.6%) 2 (2.8%)
Mean Age (yr) 33.4 ± 12.8 29.6 ± 10.4 P = 0.47
Operation time
(min) 52 ± 9.7 51.9 ± 8.7 P = 0.829
ASA: American Society of Anesthesiologists.
Figure 1. Incidence of sore throat in different time after opera-
tion.
forming parametric test did not met; therefore we used
Wilcox, rank sum test to compare VAS scores in the
study group s.
4. DISCUSSION
In our country, curved blade laryngoscope are more
commonly used than straight blades especially in our
hospital, because the laryngoscopic views obtained with
curved blades are better than straight blades [10]. How-
ever, there are many studies regarding severity and
higher incidence of PST in patients who were intubated
with curved blades [6-9]. Skills of intubator, history of
smoking, lung disease, and pressure of cuff and opera-
tion time have been implicated to be the factors which
are associated with PST [3,6-9]. Chandler ’s study show-
ed that mechanical trauma is an important factor in path-
ogenesis of PST and he found a positive assosiation be-
tween mechanical forces and PST (they studied on me-
chanical models) [4]. We didn’t find any study in litera-
ture for comparing incidence and severity of PST with
these two kinds of laryngoscope blades during tracheal
intubation. However, One study showed that force,
torque and head extension were 30% less with Miller
blade compared to Macintosh blade [5].
Our impression was that mechanical trauma plays
more important role in producing PST than other prob-
able factors. We thought that reducing stretch forces
during intubation by using straight blade may decrease
the rate of PST. But our study showed that PST rate in
recovery room and during first 48 hours after surgery
was not statistically different between Macintosh and
Miller blade. Our study has several limitations. One of
those was medications that we had to give to the patients
because of surgical pain in postoperative period. We
administered equivalent doses of morphine 0.1 mg/kg
for reducing postoperative surgical pain to both groups
of the patients. Another limitation was difficulty in ob-

K. Barkhordari et al. / Health 3 (2011) 623-625
Copyright © 2011 SciRes. http://www.scirp.org/journal/HEALTH/
625625
taining VAS score immediately after awakening from
anesthesia in some patients because of residual effect of
anesthetics. Other limitation of our study is enrollment
of only class 1 airway patients and excluding patients
with mallampatti class 3 and 4, therefore we suggest new
studies for finding probable association between difficult
intubation a n d occurrence of PST.
Openly accessible at
In conclusion, we didn’t find statistically significant
differences in the incidence and severity of PST between
curved and straight laryngoscope blades during uncom-
plicated attempts of intubation.
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