PRE-ANAESTHETIC AIRWAY ASSESSMENT AS A PREDICTOR OF DIFFICULT INTUBATION IN ADULT SURGICAL PATIENTS AT AHMADU BELLO UNIVERSITY TEACHING HOSPITAL, ZARIA

Abstract

Difficult intubation is a challenge to the anaesthetist as it comes with great consequences and
the ability to predict it allows for adequate preparation. This study was carried out to determine
the prevalence of difficult intubation in adult surgical patients in Ahmadu Bello University
Teaching Hospital, Zaria. It was also done to determine the ability to predict difficult intubation
using the following preoperative airway screening tests in isolation and combination with the
‘L-E-M-O-N’ airway assessment score.
It was a cross sectional study in which 160 consecutive patients (69 males and 91 females)
between the ages of 18-65 years scheduled for elective surgical procedures under general
anaesthesia were assessed using the individual predictors of the ‘L-E-M-O-N’ airway
assessment scoring system. The presence or absence of the ‘look’ features of facial trauma,
large incisors, beard/moustache and a large tongue were noted. The inter-incisor gap (IIG),
hyomental distance (HMD) and thyromental distance (TMD) were evaluated with the fingers
of the assessor using the 3-3-2 rule. The Mallampati score, presence or absence of neck
obstruction and degree of neck mobility were assessed. The predictors were also combined in
the ‘L-E-M-O-N’ airway assessment score with a minimum score of zero and maximum of 10.
The laryngeal view from direct laryngoscopy was graded using the Cormack and Lehane (CL)
classification. Cormack and Lehane grades III and IV were considered difficult visual
laryngoscopy (DVL).
The prevalence of difficult intubation using the CL classification was found to be 8.1%. The
“Look” features of Facial trauma, large incisors and presence of beard/ moustache had
sensitivities and positive predictive values of 0%. These features had specificities of 99.1%,
96.6% and 92.5% respectively. The sensitivity, specificity and the positive predictive value
respectively of the other features were: large tongue (15.3%, 99.3 %,66%); IIG (38.4%, 92.5%,
31.3%); HMD (61.5%,83.7%,25%);TMD (46%,87.7%,25%), Mallampati (15.9%,
96.6%,28.8%), neck obstruction (23%,98.5%,20%) and neck mobility (30.8%, 93.9%, 30.8%).
A combination of the predictors of the ‘L-E-M-O-N’ score showed that as the mean ‘L-E-M
O-N’ score of the patients increased the likelihood of having DVL also increased. This was
found to be statistically significant (p value 0.001).
It was concluded that the airway assessment clinical tests used in the ‘L-E-M-O-N’
airway scoring system were poor predictors of difficult intubation when used singly, but when
combined to give the ‘L-E-M-O-N’ score the ability to predict a difficult intubation is greatly
increased, which implies that it is able to successfully stratify the risk of difficult intubation
pre -operatively.