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RESEARCH ARTICLE
Comparison of intravenous magnesium
sulphate and lidocaine for attenuation of
cardiovascular response to laryngoscopy and
endotracheal intubation in elective surgical
patients at Zewditu Memorial Hospital Addis
Ababa, Ethiopia
Abebaw MisganawID
1
*, Mulualem Sitote
2
, Suliman Jemal
2
, Eyayalem MeleseID
2
,
Metages Hune
3
, Fetene Seyoum
4
, Alekaw Sema
5
, Dagim Bimrew
4
1Department of Anesthesia, School of Medicine, Debre Markos University, Debre Markos, Ethiopia,
2School of Anesthesia, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia,
3Department of Anesthesia, College of Medicine and Health Sciences, Debre Tabor University, Debre
Tabor, Ethiopia, 4Department of Anesthesia, College of Medicine and Health Sciences, Dire Dawa
University, Dire Dawa, Ethiopia, 5Department of Midwifery, College of Medicine and Health Sciences, Dire
Dawa University, Dire Dawa, Ethiopia
*abebawmisganaw@gmail.com
Abstract
Background
Laryngoscopy and endotracheal intubation are essential components of general anesthesia.
But it is always associated with side effects called reflex cardiovascular responses. Many
methods have been identified to attenuate these responses like intravenous lidocaine, deep
inhalational anesthesia, vasodilators, intravenous magnesium sulphate even though thera-
peutic superiority remains understudied.
Methods
An institutional-based cohort study on 112 adult patients aged between 18–60 years was
applied. 37 patients in the non-exposed group (Group N), 37 in the lidocaine group
(Group L), and 38 in magnesium sulphate (Group M) were included. The hemodynamic
parameters like heart rate, systolic, diastolic and mean arterial blood pressure at various
time points up to 7 minutes post-intubation were recorded and the effect of both drugs to
reduce hemodynamic responses was compared. Parametric data were analyzed using
ANOVA and nonparametric data using the Kuruska-Wallis H rank test. P-value <0.05
considered statistically significant.
Results
In all three groups, there was a statistically significant rise in heart rate and blood pressure
from baseline. There was a statistically significant difference in mean heart rate throughout
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OPEN ACCESS
Citation: Misganaw A, Sitote M, Jemal S, Melese E,
Hune M, Seyoum F, et al. (2021) Comparison of
intravenous magnesium sulphate and lidocaine for
attenuation of cardiovascular response to
laryngoscopy and endotracheal intubation in
elective surgical patients at Zewditu Memorial
Hospital Addis Ababa, Ethiopia. PLoS ONE 16(6):
e0252465. https://doi.org/10.1371/journal.
pone.0252465
Editor: Vincenzo Lionetti, Scuola Superiore
Sant’Anna, ITALY
Received: December 3, 2020
Accepted: May 16, 2021
Published: June 1, 2021
Peer Review History: PLOS recognizes the
benefits of transparency in the peer review
process; therefore, we enable the publication of
all of the content of peer review and author
responses alongside final, published articles. The
editorial history of this article is available here:
https://doi.org/10.1371/journal.pone.0252465
Copyright: ©2021 Misganaw et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
study minutes among the groups (p<0.001). However, there was no statistically significant
difference in mean heart rate between Groups M and L at all post-intubation time intervals.
In blood pressure at all three parameters there was statistically significant difference among
groups at all-time points except no difference at 7
th
minutes in DBP. There was significantly
lower blood pressure in group M compared to both groups.
Conclusion
In conclusion, prophylactic administration of magnesium sulphate and lidocaine was effec-
tive in attenuating hemodynamic responses to the stress effect of laryngoscopy and intuba-
tion. But based on our finding prophylaxis of magnesium sulphate is associated with a more
favorable hemodynamic response.
Background
Endotracheal intubation is an essential component of general anesthesia. It serves in the main-
tenance of patency of upper airway, proper ventilation, reduction in the risk of aspiration, and
delivery of the inhalational anesthetic agents to the patients through breathing circuits [1]. Lar-
yngoscopy and tracheal intubation are considered the most critical events during induction of
general anesthesia which stimulate somatic and visceral nociceptive afferents fibers which
induce reflex sympato-adrenal responses associated with enhanced neuronal activity in the
cervical sympathetic efferent fibers [2].
Sympathetic stimulation from laryngoscopy and endotracheal intubation causes a signifi-
cant increase in the plasma concentration of catecholamines (adrenaline and noradrenaline)
[3,4] that can provoke left ventricular failure, renal failure, surgical bleeding, cerebral hemor-
rhage and myocardial ischemia in anesthetized patients. The mechanism of this may be that,
vasoconstriction, increased myocardial work, a demand for increased coronary flow, narrowed
coronary arteries cannot accommodate the increased flow, and parts of the myocardium may
receive insufficient oxygen [5–7].
The rise in blood pressure and heart rate is usually variable and unpredictable. The reflex
tachycardia and hypertension effects of laryngoscopy are greater than of tracheal intubation.
Once the endotracheal tube is in position, and the laryngoscope withdraws; hypertension,
tachycardia, and disturbing dysrhythmia subside but tended to persist for up to 3–10 minutes.
Hypertensive patients are more prone to exaggerated cardiovascular response to laryngoscopy
and tracheal intubation than normotensive patients [2,8–13].
Change in mean MAP during laryngoscopy and endotracheal intubation from baseline
ranges from 23 to 52 mmHg [5,14,15]. Mean heart rate change from baseline after laryngos-
copy & intubation ranges from 20 to 31 beat/minute [16,17].
Both Magnesium sulphate and Lidocaine showed attenuation to presser response to laryn-
goscopy and endotracheal intubation with a different success rate in previous studies [9–11,
13,18–24]. Many methods have been identified to attenuate these responses including topical
anesthesia of oropharynx, laryngotracheal instillation of lidocaine before intubation, intrave-
nous lidocaine, deep inhalational anesthesia, narcotics, vasodilators, intravenous magnesium
sulphate, adrenergic and calcium blockers even though these techniques have drawbacks [25,
26]. Therefore this study aimed to compare the effect of intravenous lidocaine and magnesium
sulphate on the attenuation of cardiovascular responses after laryngoscopy and endotracheal
intubation in elective surgical patients.
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Data Availability Statement: The minimal data set
supporting the conclusions of this article is
available from the corresponding author and also
uploaded as ‘supporting information’.
Funding: The author(s) received no specific
funding for this work.
Competing interests: The authors have declared
that no competing interests exist.
Abbreviations: ASA, American Society of
Anesthesiologists; BSc, Bachelor of Science; BP,
Blood Pressure; CABG, Coronary Artery Bypass
Grafting; DBP, Diastolic pressure; DRERC,
Departmental Research and Ethics Review
Committee; ETI, Endotracheal intubation; GA,
General anesthesia; Group L, lidocaine group;
Group M, magnesium sulphate group; Group N,
non-exposed group; HR, Heart Rate; IV,
intravenous; MAP, Mean arterial blood pressure;
MgSO4, Magnesium sulphate; MSc, Master of
Science; NMDA, Nmethyl-d-aspartate; OR,
Operation room; PACU, post anesthesia care unit;
SBP, Systolic blood pressure; SPSS, Statistical
Package for Social Science.
Materials and methods
Study setting and period
The study was conducted in Zewditu Memorial Hospital. It provides service to an estimated
above 800,000 people annually in the different departments who are referred from different
zone of the city as well as all over the country. It has five major operation rooms and two post-
anesthesia care unite (PACU). The hospital provides surgical services for about 10,000 patients
annually. The research was conducted from November 7–2018 to March 7–2019. Patients who
were induced with thiopental as non-exposed, premedicated with either iv lidocaine or magne-
sium sulphate, age 18 up to 60 years, and ASA I &II were included in the study. Patients on
beta/Calcium channel blockers, premedicated with anticholinergic, hypertensive patients
whose blood pressure >140/90 mmHg, hypotensive patients whose systolic blood pressure
<90 mmHg, hypothyroidism or hyperthyroidism, difficult intubation were excluded.
Sample size and sampling procedure
The sample size was calculated using the previous study done in Iran in 2013 [18] by taking
mean HR, SBP, DBP, MAP, and the largest sample size was taken using the comparison of two
mean with equal sample size formula and using 80% power,α= 0.05. By adding a 10% non-
response rate, the final sample size was 112. Study participants were selected using systematic
random sampling technique using skip interval from the daily operation in the operation
room (OR) in those patients induced with thiopental with or without ether lidocaine or mag-
nesium sulphate premedication were used as a sampling frame.
A situational analysis done for one month, on average 3 patients per day or 60 patients per
month were undergone surgery using thiopental as an induction agent with or without study
drugs in Zewditu Memorial Hospital.
✓Thus, 240 patients were operated per the study period (4 months). The sampling interval;
K was determined using the formula: K = N/n; where, n = total sample size,
N = population per 4 months. K = 240/112 2
✓Therefore, the sampling interval was two and the first study participant (random start)
was selected using a lottery method from those induced with thiopental with or without
study drugs who fulfill selection criteria.
✓Then, every second case who induced with thiopental with or without study drugs was
included in study groups until the required sample size was filled during the study period.
Data collection procedures
Data was collected by a pretested structured questionnaire which enabled to take all necessary
information from the chart of the patients and measured vital signs displayed on the monitor-
ing screen. The study drugs lidocaine and magnesium sulphate in the study hospital are stan-
dardized or used routinely as part of preoperative care. We didn’t assign patients for research
purpose we just observed the anesthetists’ discretion of treatment and some anesthetists used
either lidocaine or magnesium sulphate for attenuation of hemodynamic reflex secondary to
laryngoscopy & tracheal intubation but some anesthetists intubated patients without using
both lidocaine and magnesium sulphate. Patients who refused to take part in the study were
excluded in the study but they were received similar care with study participants.
On arrival of the patients to the operative theater the routine hospital monitoring protocol,
HR, noninvasive blood pressure, and SPO2 were applied and after a room anesthetist decided
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to induce with thiopental, data collectors took verbal informed consent of patients. After pre-
oxygenation of patients with 100% oxygen for 3 minutes, anesthetists induced patients with
thiopental 5 mg/kg and suxamethonium 2mg/kg with or without pretreatment of either mag-
nesium or lidocaine and tramadol 100 mg IV for all patients. Lidocaine group (Group L)
received 1.5 mg/kg lidocaine2%, magnesium sulphate group (Group M) received 30 mg /kg
magnesium sulphate 50%, and Group N patients who induced with thiopental without taking
either premedication drugs. Lidocaine and magnesium sulphate were given before 5 minutes
of induction of anesthesia. Magnesium sulphate was injected slowly within 5 minutes. In our
study area, anesthetists who used either lidocaine or magnesium had the same practice regard-
ing the dose. Socio-demographic data like the patient’s age, sex, and ASA physical status, BMI,
associated coexisting illness were recorded from the chart. Mean arterial pressure, systolic
blood pressure, diastolic blood pressure, Heart rate and SpO2 were recorded as the baseline
(i.e., before starting of administration of magnesium sulfate or lidocaine for exposed or thio-
pental for non-exposed), 1 minute after injection of study drug, immediately after intubation
(i.e., within 30 seconds after intubation), at 2
nd
minutes post-intubation, at 5
th
minutes post-
intubation and at 7
th
minutes post-intubation.
Hypertension was considered when the BP values of SBP>140 or DBP >90 mmHg. Hypo-
tension was considered when BP values of SBP <90 mmHg. Tachycardia was considered
when HR >100 bpm. Bradycardia was considered when HR value lower than 50 bpm.
Data quality control and assurance
Data was collected using a pretested structured questionnaire which enabled to review the
chart records and measured vital signs displayed on the monitoring screen prepared in English
addressing the objective of the study. The pretest was done on 5% of the sample size at Minilik
II referral hospital. Data collectors were Anesthetists who are familiar with recording perioper-
ative data. Data collectors and supervisors were trained on each item included in the study
tools, objective, relevant of study, right of respondents. During data collection, regular supervi-
sion and follow up was made. The investigator cross-checked for completeness and consis-
tency of data on a daily basis.
Data processing and analysis
The statistical analyses were performed using SPSS 20 software. The data were tested for nor-
mality using the Shapiro–Wilk normality test and histogram. The homogeneity of variance
also checked by Levene’s test and Mauchly’s test for sphericity. One way Analysis of variance
(ANOVA) and repeated measure ANOVA was used for normally distributed continuous data.
Kruskal–Wallis H test was used for non-normally distributed data. If the ANOVAs test was
significant, then the Tukey post hoc test was used to compare one group with the others. Cate-
gorical data were analyzed using the Pearson Chi-squared test. Continuous variables were
expressed as a mean & standard deviation (SD) and Median (Q1-Q3). Categorical variables
were summarized by percentages. P-value <0.05 considered statistically significant.
Ethics approval and consent to participate
Before the data collection, ethical clearance was obtained from the Departmental Research and
Ethics Review Committee of the Department of anesthesia, School of Medicine, College of
Health Sciences of Addis Abba University. The purpose and importance of the study were
explained to study participants and the director of the hospital. We believed the study is free of
any risk since the study was an observational cohort and also the study-drugs were standard-
ized, therefore, we used verbal consent. There was no issue to obtain a written consent and the
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IRB approved the use of verbal consent. The obtained oral consent recorded by ticking on ‘yes’
if the participant agreed to participate in the study and ‘no’ if not agreed. All findings were
kept confidential. The name and addresses of the participants were not recorded in the ques-
tionnaire. Furthermore, all the basic principles of human research ethics (respect for a person,
beneficence, voluntary participation, confidentiality, and justice) were valued.
Results
Demographic and clinical characteristics of the patients
One hundred twelve patients were analyzed in this study. Thirty-seven patients in the non-
exposed group (Group N), Thirty-seven in the lidocaine group (Group L), and Thirty-eight in
magnesium sulphate (Group M) were included in this study. There was no significant differ-
ence among the three groups concerning age, gender, BMI, diagnosis, ASA physical status,
type & MAC% of inhalational agents, surgery starting time, and maintenance muscle relaxant
(p-value >0.05) as showed in Table 1.
Comparison of mean heart rate at different time points among magnesium sulphate,
lidocaine, and non-exposed groups. At baseline, Mean Heart Rate (HR) among the groups
did not show a significant difference statistically (p = 0.436). The one way ANOVA analysis
showed that there was a statistically significant difference in mean heart rate throughout study
minutes among the groups (p<0.001). And the post hoc analysis showed that mean HR was
higher in Group N with statistically significant value compared to both groups (p<0.001).
However, there was no statistically significant difference in mean heart rate between Groups
M and L at the immediate, 2
nd
, 5
th
, and 7
th
post-intubation time intervals(p = 0.324,0.222,
0.356,0.737) respectively (Table 2). Regarding within-the group comparison, there was a statis-
tically significant rise in mean heart rate from baseline in all study groups throughout study
minutes (p<0.05) (Fig 1).
Table 1. Demographic data and anesthetic characteristics of patients in Zewditu Memorial Hospital, Addis Ababa in 2018/2019.
Characteristics Group M Group L Group N P-value
Age (years) Mean ±SD 32.32±7.19 36.05±7.69 34.68±8.34 0.112
Sex (F/M) Female (%) 84.2 78.4 89.2 0.448
Male (%) 15.8 21.6 10.8
ASA status ASA I (%) 100 100 100 -
BMI Median (Q3-Q1) 24 (25–23) 24 (25–23) 24 (25–23) 0.660
Diagnosis Goiter (%) 47.4 40.5 51.4 0.843
Cholilethiasis (%) 28.9 35.1 32.4
Neurosurgery (%) 23.7 24.4 16.2
Maintenance inhalational agents Isoflurane (%) 81.6 67.6 75.7 0.372
Halothane (%) 18.4 32.4 24.3
MAC of inhalational agent MAC1% (%) 18.4 27 10.8 0.103
MAC1.5%(%) 78.9 67.6 73.0
MAC2%(%) 2.7 5.4 16.2
Maintenance muscle relaxant within 7 minutes Pancuronium (%) 28.9 10.8 13.5 0.286
Vecuronium (%) 10.5 10.8 10.8
No muscle relaxant within 7 minutes (%) 60.6 78.4 75.7
Is surgery started within 7 minutes of intubation? Yes (%) 15.8 21.6 16.2 0.765
No (%) 84.2 78.4 83.8
Data are analyzed by ANOVA, Kruskal Wallis, and Chi-Square Test, BMI-Body mass index, MAC- minimum alveolar concentration.
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Comparison of mean SBP at different time points among magnesium sulphate, lido-
caine, and non-exposed groups. There were no statistically significant intergroup differ-
ences in baseline SBP among groups (p = 0.655). There was a statistically significant difference
in mean SBP among groups at the all-time points. Post hoc analysis showed significant lower
mean SBP at immediate, 2
nd
, and 5
th
minutes post-intubation in group M compared to Group
L (p <0.001, p = 0.001, p = 0.029), respectively. And there was also a statistically significant
decrement in mean SBP when group M compared to group N at the immediate, 2
nd
, 5
th
(p<0.001), and 7th minute post-intubation (p = 0.006) but there was no significant difference
between two treatment groups at 7
th
minute. There was also a statistically significantly lower
mean SBP in group L compared with group N at all-time points except at 7
th
minute (Table 3).
Table 2. Comparison of mean heart rate among the groups and between groups in Zewditu Memorial Hospital, Addis Ababa, 2018/2019.
Time interval Group M Group L Group N Significance of the difference among the groups Comparison between Group M & Group L
Mean ±SD Mean ±SD Mean ±SD P-value P-value
Baseline 80.97±6.28 80.24±4.85 82.16±7.84 0.436 0.876
Immediate Post
Intubation
99.82
±10.86
96.35±9.25 120±11.04 <.001
, #
0.324
2min post Intubation 94.47
±11.37
90.49±9.64 112.22±9.93 <.001
, #
0.222
5min post Intubation 88.13±9.58 84.84±8.28 104.46
±12.70
<.001
, #
0.356
7min post Intubation 85.79±8.48 84.03±8.69 100.65
±12.95
<.001
, #
0.737
p<0.05 compared group N with M
#
P value <0.05 compared group N with L (ANOVA, Tukey test).
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Fig 1. Within-the group change in heart rate at different time intervals in Zewditu Memorial Hospital, Addis Ababa, 2018/2019.
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Regarding within-the group comparison there was a significant rise in SBP in group M at the
immediate post-intubation time only (p <0.001) and return to baseline at the 2
nd
minute of
intubation. In the lidocaine group, there was a significant rise in SBP at the immediate and at
2
nd
minute post-intubation (p<0.001) and return to baseline at 5
th
minute of intubation
(p= 0.643) whereas in non-exposed group significant rise in SBP continued till the fifth post-
intubation minute (Fig 2).
Comparison of mean DBP at different time points among magnesium sulphate, lido-
caine, and non-exposed groups. The baseline DBP was comparable among the three groups
(p = 0.194) and there was a statistically significant difference among the groups at immediate,
2
nd
, and 5
th
minutes post-intubation intervals but not at 7
th
minutes post-intubation. Post hoc
analysis showed that group M has significantly lower mean DBP at immediate, 2
nd
, and 5
th
minutes post-intubation compared to Group N (p <0.001). There was also a statistically
Table 3. Comparison of mean SBP among the groups and between groups at different time intervals in Zewditu Memorial Hospital, Addis Ababa, 2018/2019.
Time Interval Group M Group L Group N Significance of the difference among the groups Effect size
Mean ±SD Mean ±SD Mean ±SD P-value η2
Baseline 126.66±7.48 126.62±6.37 127.78±4.14 0.655 -
Immediate Post intubation 142.71±10.14 155.27±12.62 179.27±17.82 <.001
, #, +
0.55
2min post Intubation 129.58±10.96 141.54±11.47 152.95±17.98 <.001
, #, +
0.33
5min post Intubation 119.26±7.94 125.68±10.36 134.22±13.18 <.001
, #, +
0.25
7min post Intubation 115.71±7.81 118.35±10.08 122.49±9.81 0.0030.08
p<0.05 compared group N with M
#
P value <0.05 compared group N with L
+p<0.05 compared group L with group M (ANOVA, Tukey test).
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Fig 2. Within-the group change in SBP at different time intervals in Zewditu Memorial Hospital, Addis Ababa, 2018/2019.
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significant lower mean DBP in Group L at the immediate, 2
nd
, and 5
th
minutes post-intubation
compared to Group N (p <0.001, <0.001, = 0.002); respectively. There was no statistically sig-
nificant difference in mean DBP between Group M and Group L except at immediate and 2
nd
minute post-intubation periods (p = 0.018, 0.019) respectively (Table 4). Regarding within-the
group comparison, there was a significant rise in DBP in group M only at immediate and at
2
nd
minute of intubation with (p <0.001, = 0.010) respectively. Similarly in the lidocaine
group, there was a significant rise in DBP at immediate and at 2
nd
minute of post-intubation
(p<0.001) whereas in the non-exposed group significant rise in DBP continued till the fifth
minute (p<0.001).
Comparison of mean MAP at different time points among magnesium sulphate,
lidocaine, and non-exposed groups. Regarding baseline-MAP, groups were matched
(p = 0.548). There was a statistically significant difference in mean MAP among all groups at
all-time points (Table 5). Post hoc analysis showed significant lower mean MAP at immediate,
2
nd
, 5
th
minutes post-intubation in group M compared to Group L (p = 0.002, p = 0.001,
p = 0.023 respectively). Group M compared to group N, mean MAP was significantly lower at
immediate, 2
nd
, 5
th
and at 7
th
minutes post-intubation intervals (p<0.001, <0.001, <0.001, =
0.011) respectively. Also Group L has significantly lower mean MAP at immediate, 2
nd
, and 5
th
minutes post-intubation intervals compared to Group N (p<0.001, <0.001, = 0.001 respec-
tively). At 7
th
minute there was no statistically significant difference in MAP between group L
and N (p = 0.310) (Table 5). Regarding within-the group comparison, there was a significant
rise in MAP in group M at immediate and 2
nd
minute of intubation with (p <0.001, = 0.041
respectively). Similarly in the lidocaine group, there was a significant rise in MAP at immediate
Table 4. Comparison of mean DBP among the groups and between groups at different time intervals in Zewditu Memorial Hospital, Addis Ababa, 2018/2019.
Time Interval Group M Group L Group N Significance of the difference among the groups Effect size
Mean ±SD Mean ±SD Mean ±SD P-value η2
Baseline 77.16±5.23 74.76±5.61 75.73±6.28 0.194 -
Immediate Post Intubation 91.29±8.29 97.70±10.28 112.81±11.40 <.001
, #, +
0.45
2min post Intubation 81.08±8.07 87.49±9.42 97.73 ±12.36 <.001
, #, +
0.32
5min post Intubation 72.87±7.44 77.11±7.79 84.59±11.96 <.001
, #
0.22
7min post Intubation 71.00±6.70 73.14±8.83 74.62.±6.98 0. 183 -
p<0.05 compared group N with M
#
P value <0.05 compared group N with L
+p<0.05 compared group L with group M (ANOVA, Tukey test).
https://doi.org/10.1371/journal.pone.0252465.t004
Table 5. Comparison of mean MAP among the groups and between groups at different time intervals in Zewditu Memorial Hospital, Addis Ababa, 2018/2019.
Time Interval Group M Group L Group N Significance of the difference among the groups Effect size
Mean ±SD Mean ±SD Mean ±SD P-value η2
Baseline 93.71±4.26 92.51±5.54 92.78±4.97 0.548 -
Immediate Post Intubation 108.29±8.40 116.95±10.29 134.65±13.36 <.001
, #, +
0.51
2min post Intubation 96.47±7.56 105.57±8.97 116.03±13.41 <.001
, #, +
0.38
5min post Intubation 87.87±7.30 93.35±7.56 100.95±11.20 <.001
, #, +
0.27
7min post Intubation 85.53±6.88 88.30±8.40 91.09±9.05 0.0150.07
p<0.05 compared group N with M
#
P value <0.05 compared group N with L
+p<0.05 compared group L with group M (ANOVA, Tukey test).
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and 2
nd
minute of post-intubation (p<0.001) whereas in the non-exposed group significant
rise in MAP continued till the fifth minute (p<0.001).
Discussion
In our prospective cohort study demographic data, anesthetic characteristics of patients, and
baseline hemodynamic variables (SBP, DBP, MAP, and HR) were comparable in both groups.
Heart rate
In this study the peak mean heart rates occurred at the immediate post-intubation time, which
was 99.82±10.86, 96.35±9.25, 120.0±11.04 in group M, L N respectively with (p <0.001). Our
study showed that there was a statistically significant difference in mean heart rate at all post-
intubation time intervals among the groups (p<0.001). The mean heart rate in Group N was
significantly higher compared with Group L and M at all post-intubation time intervals. How-
ever, there was no statistically significant difference in mean heart rate between Groups M and
L at all post-intubation time intervals. In this study, a statistically significant increase in mean
heart rate from baseline was observed in Group M, Group L, and Group N at all post-intubation
time intervals. Bandey S. et. al in 2016 noted Similar findings [11].
Our study is also consistent with other studies done by Bhalerao NS et al (2017) reported
that the difference in HR was not statistically significant between magnesium sulphate and
lidocaine groups throughout the study period. In contrary to our study, they found no sta-
tistically significant change in mean heart rate from baseline in both groups regarding
within-the group comparison [10]. The possible difference from our study may be the varia-
tion in the drug used for induction (propofol) and the dose of pretreatment (magnesium
sulphate: 50mg/kg and lidocaine: 2mg/kg but in our study anesthetists used 30mg/kg and
1.5mg/kg respectively).
In contrary to our finding, Waseem M et al (2011) showed that there was a statistically sig-
nificant difference between magnesium sulphate and lidocaine groups in attenuating incre-
ment of heart rate. A higher percentage of patients in the magnesium group (25.6%) than the
lidocaine group (12.35%) had heart rate increment from baseline by >25% from baseline [27].
The possible explanation for this different result might be due to a low dose of magnesium sul-
phate (10mg/kg) but in our study anesthetists used 30mg/kg.
Systolic blood pressure
Our study demonstrated a statistically significant difference in mean SBP among all groups at
all time points. There was lower mean SBP at the immediate, 2
nd
, and 5
th
minutes of post-intu-
bation in group M compared to Group L (p <0.001, p = 0.001, p = 0.029 respectively) and
compared to group N (p<0.001). Again there was significantly lower mean SBP in group L
compared with group N at all-time points except at 7
th
minute. At 7
th
minute there was a sig-
nificantly lower mean SBP in group M compared with group N (p= 0.006) but there was no
significant difference between the two treatment groups. On within-the group comparison
there was a significant rise in SBP in group M at the immediate post-intubation time only
(p <0.001) and return to baseline at 2
nd
minute of intubation. In the lidocaine group, there
was a significant rise in SBP at the immediate post-intubation time and 2
nd
minute post-intu-
bation (p<0.001) and there was no statistically significant difference at 5
th
minute post-intu-
bation time (p = 0.643) whereas in non-exposed group significant rise in SBP continued till 5
th
minute.
Our study is in line with a study done by Sachin Padmawar, et al (2016) reported that there
was a significantly higher mean SBP in the lidocaine group as compared with the MgSO4
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Comparison of intravenous magnesium sulphate and lidocaine for attenuation of cardiovascular response
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group at 1,3,5 minutes after intubation. Regarding within-the group comparison, SBP
increased significantly from baseline. But it came to baseline within 5 minutes in the magne-
sium group, whereas in the lidocaine group did not come to baseline value within 5 minutes in
our study these parameters came to baseline faster [13]. The possible reason might be in their
study used low volume% of halothane for maintenance (0.4–0.6%).
Our study is also consistent with other study done by Nooraei N et al (2013) found a statisti-
cally significant difference in mean SBP between magnesium sulphate and lidocaine groups at
1
st
and 2nd minutes(p = 0.001,0.033)respectively with higher value in the lidocaine group [18].
In contrast to our study, done by Mendonca FT et al (2016) they compared the episodes of
hypertension (increase in SBP >20%of baseline) after intubation and there was no statistical
significance difference between magnesium and lidocaine groups. Three patients in the mag-
nesium group (12%) had compared to one patient (4%) in the lidocaine group with (p >0.05)
they found magnesium has similar results to lidocaine [23]. The possible difference with our
finding might be due to variation in induction agent they used propofol and fentanyl pretreat-
ment in our study not.
Diastolic blood pressure
There was a statistically significant difference among all groups at immediate, 2
nd
, and 5
th
min-
utes post-intubation intervals but not at 7
th
minute of post-intubation. Group M has a statisti-
cally significantly lower mean DBP at immediate, 2
nd
, and 5
th
minutes post-intubation
intervals compared to Group N (p <0.001). Also Group L has significantly lower mean DBP
at immediate post-intubation, 2
nd
and 5
th
minutes post-intubation intervals compared to
Group N (p <0.001, <0.001, = 0.002). Group M compared to Group L has significantly lower
value only at immediate and at 2
nd
minutes post-intubation periods with (p = 0.018, 0.019
respectively). DBP rose significantly from baseline in group M at immediate and 2
nd
minutes
of intubation with (p <0.001, = 0.010 respectively). Similarly in the lidocaine group, there was
a significant rise in DBP at immediate and 2
nd
minutes post-intubation with (p<0.001)
whereas in the non-exposed group a significant rise in DBP continued till the fifth minute with
(p<0.001). Our findings are in line with two studies done in 2016 by Bandey S et al and Sachin
Padmawar et al [11,13].
In contrary to our findings, Nooraei N et al (2013) showed no statistically significant differ-
ence in mean DBP between magnesium sulphate and lidocaine groups throughout study min-
utes for five minutes [18]. The likely explanation for this inconsistency could be Nooraei N.
et. al used fentanyl which is effective in attenuating hemodynamic response secondary to lar-
yngoscopy and intubation [28].
Mean arterial pressure
There was a statistically significant difference in mean MAP among all groups at all time
points. There was also significant lower mean MAP at immediate, 2
nd
, and 5
th
minutes post-
intubation in group M compared to Group L (p <0.001, p = 0.001, p = 0.029 respectively).
Group M compared to group N, mean MAP was significantly lower at immediate, 2
nd
minutes,
5
th
minute and at 7
th
minutes post-intubation intervals (p<0.001,<0.001,<0.001, = 0.011
respectively). Group L has a significantly lower mean MAP at immediate, 2
nd
, and at 5
th
min-
utes post-intubation intervals compared to Group N (p <0.001, <0.001, = 0.001respectively).
MAP rose significantly from baseline in group M at immediate and 2
nd
minutes of intubation
with (p <0.001, = 0.041 respectively). In the lidocaine group also there was a significant rise in
MAP at immediate and 2
nd
minutes post-intubation with (p<0.001) whereas in non-exposed
group significant rise in MAP continued till the fifth minute with (p<0.001). In line with our
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Comparison of intravenous magnesium sulphate and lidocaine for attenuation of cardiovascular response
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study done by R Vallabha et al (2018) reported mean MAP in lidocaine and magnesium sul-
phate group respectively were 88.70+8.95 vs 79.83+7.34, 88.70+8.95 vs 79.83+7.34, 86.50+8.37
vs 78.03+7.10 at 1
st
, 3
rd
, and 5
th
minutes respectively (p <0.001). They found a significantly
lower MAP in magnesium sulphate compared with lidocaine group [29].
Inconsistent to our study done by G Kiraci, et al (2014) observed no significant difference
in MAP at immediate, 2
nd
, 5
th
and 10
th
post-intubation minutes between magnesium, lido-
caine, and control groups (P>0.05) [30]. The possible controversy from our study might be
the variation in the drug used for induction (propofol) and the dose of pretreatment (magne-
sium sulphate: 10mg/kg and lidocaine: 1mg/kg but in our study anesthetists used 30mg/kg and
1.5mg/kg respectively).
Limitation
The current study has certain limitations such as inability to control over the confounding fac-
tors like type of inhalational agent for maintenance, MAC of inhalational agent, diagnosis and
maintenance muscle relaxant in addition in our study setting the study drugs are based on the
preference of anesthetists since the design is observational.
Strength
We have tried to make comparable study groups by including patients who induced with same
induction agent. We had no incomplete data with missing values, adequate sample size was
attained on the planned schedule of time. So that the difference observed may be due to expo-
sure factors.
Relevance of the study
Based on our finding we recommend prophylactic IV magnesium sulphate and lidocaine to
consider for attenuating hemodynamic response to laryngoscopy and endotracheal intubation.
We also recommend additional randomized clinical trial.
Conclusion
In conclusion, prophylactic administration of magnesium sulphate and lidocaine was effective
in attenuating hemodynamic responses of laryngoscopy and endotracheal intubation. But
based on our finding prophylaxis of magnesium sulphate is associated with a more favorable
hemodynamic response.
Supporting information
S1 File.
(SAV)
S2 File.
(DOCX)
Acknowledgments
We would like to thank the anesthesia department of Addis Ababa University for all their sup-
port and constructive comments.
We would like also to extend our appreciation to Zewditu Memorial Hospital medical
directorate, anesthesia staff, and data collectors for their assistance and cooperation in the
completion of this study.
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Comparison of intravenous magnesium sulphate and lidocaine for attenuation of cardiovascular response
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Author Contributions
Conceptualization: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem Melese,
Metages Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
Data curation: Abebaw Misganaw, Suliman Jemal, Fetene Seyoum, Alekaw Sema, Dagim
Bimrew.
Formal analysis: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem Melese,
Metages Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
Funding acquisition: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem Melese,
Metages Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
Investigation: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem Melese,
Metages Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
Methodology: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem Melese,
Metages Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
Project administration: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem
Melese, Metages Hune, Fetene Seyoum, Alekaw Sema.
Resources: Abebaw Misganaw, Suliman Jemal, Eyayalem Melese, Metages Hune, Fetene
Seyoum, Alekaw Sema, Dagim Bimrew.
Software: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem Melese, Metages
Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
Supervision: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem Melese, Metages
Hune, Fetene Seyoum, Dagim Bimrew.
Validation: Abebaw Misganaw, Mulualem Sitote, Eyayalem Melese, Fetene Seyoum, Dagim
Bimrew.
Visualization: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem Melese,
Metages Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
Writing – original draft: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem
Melese, Metages Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
Writing – review & editing: Abebaw Misganaw, Mulualem Sitote, Suliman Jemal, Eyayalem
Melese, Metages Hune, Fetene Seyoum, Alekaw Sema, Dagim Bimrew.
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