ATTENUATION OF THE PRESSOR RESPONSE TO LARYNGOSCOPY AND ENDOTRACHEAL INTUBATION: A COMPARISON OF INTRAVENOUS ESMOLOL AND LIDOCAINE

Abstract

Laryngoscopy and tracheal intubation often elicit a haemodynamic response which
could be deleterious in patients with cardiovascular and intracranial pathology.
Lidocaine and esmolol are two of several agents used by anaesthetists to attenuate this
response. Lidocaine is the agent commonly used by anaesthetists practicing in most
developing countries like Nigeria as it is cheap, while esmolol has been used in parts of
North America, Europe and Asia. The effect of esmolol on the pressor response is yet
to be evaluated in an African population. The aim of this study was to evaluate and
compare the effectiveness of these two drugs in attenuating the haemodynamic changes
which accompany laryngoscopy and endotracheal intubation in an adult Nigerian
population at the Lagos University Teaching Hospital (LUTH).
Ninety (90) ASA physical status class 1 and 2 adult patients undergoing elective
surgical procedures under general anaesthesia were included in this randomised, single
blind, placebo controlled study. The effectiveness of 2mg.kg -1 of esmolol administered
two minutes before laryngoscopy was compared with intravenous lidocaine 1.5mg.kg
1 given three minutes before laryngoscopy in attenuating the pressor response to
laryngoscopy and endotracheal intubation. The patients were randomly assigned by
blind balloting to one of three groups, Esmolol (E), Lidocaine (L), and Control(C).
Group E patients had 2mg.kg -1 of intravenous esmolol made up to 20mls, given two
minutes before laryngoscopy and intubation. Group L patients had 1.5mg.kg -1 of
lidocaine made up to 20mls, administered intravenously 3 minutes before laryngoscopy
and intubation, while those in the control group were given a placebo of 20mls of 0.9%
saline 3 minutes before laryngoscopy.
Anaesthesia was induced with 4mg.kg -1 of 2.5% thiopentone sodium and tracheal
intubation facilitated with 1.5mgkg-1 suxamethonium chloride in all three groups. Heart
rate (HR), systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Mean
Arterial Pressure (MAP) and Rate pressure product(RPP) were recorded as baseline,
immediate post-intubation, 1, 3, 5 and 10minutes after laryngoscopy and intubation.
Readings of HR, SBP, DBP, MAP and RPP were compared with baseline values and
among each group.
All patients showed post-intubation increases in haemodynamic variables but to
varying degrees. The mean heart rate increased by 19.1%, 25.7% and 41.4% in groups
E, L and C respectively. SBP increased by 13.3%, 21.6% and 26.9%, DBP by 16.2%,
34.5% and 46.1%, MAP by 12.2%, 19.1% and 30.2% and RPP by 28.1%, 45.8% and
78.7% in groups E, L and C respectively.
The post-intubation rise in heart rate (HR) was significantly less in both treatment
groups (p<0.05) compared to the control group, but more in the esmolol group. There
was also a significantly lower increase in SBP post-intubation in the esmolol group
(p<0.05), but not in the lidocaine group (p>0.05). The changes in DBP and MAP were
significantly less in both treatment groups compared to the control group. Both
treatment techniques showed significance in attenuating the post-intubation rise in RPP
(P<0.05) but this was more in the esmolol group.
These findings demonstrated that both drugs in the doses used in this study, attenuated
the pressor response to laryngoscopy and intubation to varying degrees. As observed in
similar studies conducted in non-African patients, intravenous esmolol was statistically
superior to intravenous lidocaine for attenuating the haemodynamic response to
laryngoscopy and intubation. There were no complications attributable to the use of
either drug recorded during the course of the study.