Evaluation of different bedside clinical predictors in estimating difficult laryngoscope and intubation in head and neck cancer surgery patients

INTRODUCTION

Malignant or benign tumors of the cervicomaxillofacial region have a high level of difficulty for the anesthesiologist due to the high density of structures in a relative restricted area and due to the operating room being shared with the surgical team. Among all the types of surgical interventions, those related to the oro-maxillo-facial area have the highest incidence of possibly difficult intubation.  This is the reason why it is extremely important to have a thorough preoperative, clinical and imagistic assessment in order to set out the instrumentation strategy of the airways.  The anatomical and physiological changes of patients with head and neck cancer make difficult the management of airway during the perioperative period. The first major responsibility for the anesthesia professional is to provide adequate ventilation and oxygenation by securing the patient’s airway. Preoperative assessment of the patient’s airway facilitates the anesthetists to predict the ease of visualizing the glottis and to perform intubation easily.

Management of the difficult airway is one of the most relevant issues and core competency for practicing anesthetists.^1,2 Maintaining a patent airway is must for adequate oxygenation and ventilation and failure to do so, even for a brief period of time can be life threatening. Difficult airway management can result in patient harm from relatively minor problems such as oral trauma up to an increased risk of aspiration, hypoxia, cerebral damage and death from inability to oxygenate.³ Appropriate management of the difficult airway constitutes an important place in the prevention of mortality and morbidity associated with anesthesia. Failure to assess for and identify potential difficulty, or the application of poor judgment in management planning, may contribute to a poor outcome.^4,5

The term “difficult airway” covers a spectrum ranging from problems in ventilating a patient’slung with a face mask or supraglottic airway to problems in intubating and extubating a patient’s trachea. A recent guideline update defines the difficult airway as an airway for which an experienced practitioner anticipates or encounters difficulty with facemask ventilation, tracheal intubation, or supraglottic airway use or recognizes the need for an emergency surgical airway.⁶ The prevalence of difficult laryngoscopy (inability to visualize any portion of the vocal cords after multiple attempt at laryngoscopy) has been reported to range between 5% and 20%, and a variety of physical examination tests have been used to estimate its presence.^6-9 Difficult endotracheal intubation is defined as endotracheal intubation requiring multiple attempts.^9,10,14 The incidence of failed intubation is approximately 1 in 1000 and the incidence of cannot intubate cannot ventilate is approximately 1 in 2800–20,000.^9,10

Among the strategies proposed to decrease morbidity and mortality related to difficult tracheal intubation (DTI), the role of its predictors remains a matter of debate.⁹ Several clinical signs have been identified as predictors of difficult laryngoscopy or difficult tracheal intubation (DTI). These include the Mallampati score, the Thyromental Distance (TMD), Upper Lip Bite Test (ULBT), Sterno-Mental Distance (SMD), Ratio of height to Thyromental distance (HRTMD), and Inter Incisor Distance (IID). However, the sensitivity, specificity, positive and negative predictive values of these signs is a matter of debate and it requires set-up based investigation.¹⁵

Aim and Objectives:

·        “Evaluation of different bedside clinical predictors in estimating difficult laryngoscopy and intubation in head and neck cancer surgery patients ”  Head and neck cancer surgeries like cancer of oral cavity and buccal mucosa cancers

·         Primary Objective: To calculate the prevalence of difficult airway laryngoscopy and intubation ( Cormack and lehane laryngoscopy score of I, II, III,IV ) and intubation difficulty score

·        Secondary objective: To estimate of predictive value of different clinical parameters

              1. Mallampati grading

              2. Interincisor distance ( > 2 fingers )

              3. Thyromental distance

              4. Jaw protrusion

              5. Sternomental distance

              6. Upper lip bite test

 Reviewer of literature

Honarmand A  et al (2015) conducted a prospective study that  total 600 patients participated in this study. NC, NC/TMD and RHTMD were measured, and ULBT and MMT were performed and recorded. The laryngoscopy view was graded according to Cormack and Lehane’s scale (CLS) and difficult laryngoscopy was defined as CLS grades 3 and 4. Accuracy of tests in predicting difficult laryngoscopy was assessed using the area under a receiver-operating characteristic curve. The area under the curve in ULBT and RHTMD were significantly larger than that in TMD, NC and MMT. No statistically significant differences were noted between TMD, NC and MMT (all P > 0.05) (ULBT = RHTMD > NC/TMD > TMD = NC = MMT). RHTMD (>22.7 cm) exhibited the highest sensitivity (sensitivity = 64.77, 95% confidence interval [CI]: 53.9–74.7) and the most specific test was ULBT (specificity = 99.41%, 95% CI: 98.3–99.9). RHTMD and ULBT as simple preoperative bedside tests have a higher level of accuracy compared to NC/TMD, TMD, NC, MMT in predicting a difficult airway.

Dhanger S  et al (2016) conducted a study that to determine the incidence of difficult intubation in the Indian population and also to determine the diagnostic accuracy of bedside tests in predicting difficult intubation. Total 200 patients belonging to age group 18–60 years of American Society of Anesthesiologists I and II, scheduled for surgery under general anesthesia requiring endotracheal intubation were enrolled. Patients with upper airway pathology, neck mass, and cervical spine injury were excluded from the study. An attending anesthesiologist conducted preoperative assessment and recorded parameters such as body mass index, modified Mallampati grading, inter-incisor distance, neck circumference, and thyromental distance (NC/TMD). After standard anesthetic induction, laryngoscopy was performed, and intubation difficulty assessed using intubation difficulty scale on the basis of seven variables. Among the 200 patients, 26 patients had difficult intubation with an incidence of 13%. Among different variables, the Mallampati score and NC/TMD were independently associated with difficult intubation. Receiver operating characteristic curve showed a cut-off point of 3 or 4 for Mallampati score and 5.62 for NC/TMD to predict difficult intubation.  The diagnostic accuracy of NC/TM ratio and Mallampatti score were better compared to other bedside tests to predict difficult intubation in Indian population.

Nagarkar R  et al (2019)  conducted a  retrospective review of the medical record of 500 patients operated from January 2008 to December 2013. Patients were reviewed for a mode of airway management, a total length of post-operative hospital stay (PLOS), and incidence of elderly patients in the total number of head and neck cancer surgeries posted for various diagnostic and definitive treatments.  Total 500 patients, 462 patients (92.4%) underwent nasal intubation, of which 320 underwent fiberoptic (FO) intubation (64%), 7 underwent tracheotomies after completion of surgery (1.4%), and 3 underwent at the beginning of surgery (0.6%). The remaining 38 patients (7.6%) underwent oral intubation.  Nasotracheal intubation using fiberoptic bronchoscopy is the most preferred technique for the management of a difficult airway. Efficient airway management during the perioperative period significantly reduces the post-operative length of hospital stay and morbidity.

Vaibhavi Hajariwala,  et al (2020) conducted a study that all patients, 18 to 60 years of age, ASA physical status I, II and III and diagnosed with head and neck cancer were assessed for difficult airway by using following predictors: Modified Mallampati(MMT) classification. Jaw protrusion (Calder’s test). Thyromental distance (TMD). Mobility of cervical spine. Atlanto occipital joint extension. Cormack and Lehane grading. Sensitivity, specificity and positive predictive value of MMT, jaw protrusion and thyromental distance were calculated. The incidence of difficult intubation was 27.17% in our study. Sensitivity of MMT was 86.4 % and specificity was 91.4 %. Sensitivity of the jaw protrusion test was 90.9 % and specificity was 87.14%. Thyromental distance had sensitivity of 45.5 % and specificity of 60%. Combination of MMT and jaw protrusion were better predictors for this study. Accurate prediction of difficult airway is crucial especially in head and neck cancer patients. Use of different predictors along with ultrasonography for the prediction of difficult intubation should be taken into consideration in recent anaesthesia practice.

Alemayehu T, et al (2022) conducted a study that to assess the magnitude and predictors for difficult laryngoscopy and intubation among surgical patients who underwent elective surgery under general anesthesia with endotracheal intubation at Tikur Anbessa Specialized Hospital from February 1 to March 30, 2019. An institutional based cross sectional study was conducted from February 1 to March 30, 2019 on patients who underwent elective surgery under general anesthesia with endotracheal intubation. Data on socio-demographic characteristics, preanesthetic airway assessment and laryngoscopic view were collected. Data were analyzed by SPSS Version 20.0. Chi- square test, binary logistic regression and multivariate analysis were performed. Tables and texts were used to present data. A p value less than 0.05 was considered as statistically significant. The magnitude of difficult laryngoscopy, difficult intubation, and failed intubation were 12.2%, 6.1%, and 0.67%, respectively. Upper Lip Bite Test (ULBT) had a higher sensitivity (90.2%) and negative predictive value of 85.3%. Mallampati had a sensitivity of 45.8% and negative predictive value of 86% in predicting difficult laryngoscopy. Mallampati grade, thyromental distance and ratio of height to thyromental distance (HRTMD) have also showed greater sensitivity (69.6%, 58.3% and 47.8%, respectively) when compared to other tests in predicting difficult intubation. Mallampati class, upper lip bite test (ULBT) and inter-incisor distance (IID) are independent predictors for difficult laryngoscopy (p < 0.05). Furthermore, Mallampati class, Thyromental distance and ratio of height to thyromental distance (HRTMD) are identified as independent predictors of difficult intubation (p < 0.001). Mallampati class, Thyromental distance and Ratio of height to Thyromental distance (HRTMD) can predict the probability of difficult endotracheal intubation in adult patients. Whereas, Mallampati class and upper lip bite test (ULBT) predicts higher probability for difficult laryngoscopy.

Materials and Methods:

Study Setting:

•      The study will be conducted in Department of Anaesthesiology, King George’s Medical University, Lucknow in various operation theaters after getting clearance from the ethical committee, Research Cell, KGMU, Lucknow. 

Study Design: 

Prospective longitudinal study

Study Duration:

–     One year

Sample collection – 100 cases

On the basis of previous study, The sample size (n) = 2 (Zα/₂ + Z _[1-β])² × σ²/( μ1�’μ2)², assuming 0.05 level significance (Z_α/2 =1.96), and 90% power (Z _[1-β])=1.28) was 29.13 . In this study we will enroll 49 patients in each group of the study.

2 (Zα/₂ + Z _[1-β])² × σ²

n=

      (μ1�’μ2)²

2 (1.96 + 1.28)² ×40.5²

n=

    (68.75-34.38)²

n=100

•      Inclusion Criteria:

o   Patient of either sex, Age group of 18-65 years

o   ASA I or II or III

o   Oral cavity cancers

o   Buccal mucosa cancers

o   Taken radiotherapy

 Exclusion Criteria:

o   Patient Refusal

o   Previously operated for same disease

o   Pateints having stiff joint syndrome

o   Body mass index ( BMI > 35)

o   Haemodynamically unstable

METHODOLOGY:

After taking approval from the Institutional Ethics Committee and Informed Consent for the procedure from the patients, patients who are posted for elective  of  head and neck cancer surgeries like cancer of oral cavity , buccal mucosa cancers, cancer of nasopharynx, cancer of thyroid, cancer of parotid

         After completing proper valid history and general examination of patients, airway assessment of the patients was done by using following methods

l  Modified mallampati grading

l   Jaw protrusion (Calder’s test).

l   Thyromental distance.

l  Mobility of cervical spine.

l   Atlanto- occipital joint extension. 

Incase any change by inter-observer variability.To avoid this variability, all the predictors were assessed by same professor . It was assessed by asking the patient to seat comfortably and to open the mouth and protrude the tongue and told the patient to keeps their head in natural position without any phonation . the view than graded as following;

Modified Mallampati Grading

l  Class I: Soft palate,fauces, uvula and  both anterior and posterior pillars visualized

l  ClassII: Soft palate,uvula,fauces visualize but pillars not visualized.

l  Class III: Soft palate and the base of uvula visualized

l  Class IV:Only hard palate visible.

Thyromental Distance :  This is used to measure and determine the proper alignment of pharyngo-laryngeal axis and how is tongue placed in submadibular fossa. It is the  distance between mentum and thyroid notch and this is measured while patient keeps their head fully extended. If thyromental distance is >6.5 cm than airway is normal and if <6.5 cm then suggestive of difficult airway

The other predictor also used like jaw protrusion ( calder’s test ) , in this predictor we  asked to patients to protrude their mandible as far as they can. Depending on this

l  CLASS A:-  the lower incisors can be protruded beyond the upper incisors

l  CLASS B:-the lower incisors can be advanced only to the level of the upper incisors

l  CLASS C:- the lower incisors cannot reach the level of upper incisors

Class B and Class C were considered as a difficult airway  if inter incisors gap between upper and lower incisors is 4.5 cm or more than this is normal and if this distance is less than 3.5 cm then this is predicted as a difficult airway

Extension at atlanto-occipital joint was also considered as a predictor of difficult airway

 Difficult intubation :-  Modified mallampati class III and class IV

                                       Jaw protrusion class B and class C

Thyromental distance <6.5 cm

Every patient with mallampati class IV and mouth opening less than one finger were prepared for the awake fiber optic intubation done

Kept patients nil per oral for atleast 8 hours before surgery

Written and explained consent was taken from patient and attendant on the day of surgery in the pre operative room

 PROCEDURE:-

On arrival in the operative room, two 18G IV line one in left and anther in right hand placed and IV fluid Ringer lactate was started and standard monitoring equipment will be attached (electrocardiogram lead II and lead V5, pulse oximeter, and noninvasive blood pressure) and baseline vital parameters such as heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), respiratory rate (RR), oxygen saturation (SpO2) will be recorded just before anesthesia .

patients were premedicated with injection glycopyrrolate 0.004 mg/kg ,injection midazolam 0.5 mg. Patients with mallampati class IV and mouth opening less than one finger were prepared for the awake fiber optic intubation done

Patient is preoxygenated with 100% for 3-4 minutes. Anesthesia will be induced with injection propofol 1.5 mg/kg, and injection fentanyl 1mcg/kg intravenously. After conforminhg that patient is properly ventilated by checking bilateral chest rise , the muscle relaxant injectin succinylcholine 2 mg /kg was given and ventilatedtill fssciculations faded. Supplemental  high flow oxygen at 10 liters / minutes given to all patients to maintain oxygention throughout the laryngoscopy for intubation. Patients who werw presented with mallampati class I, II and III direct laryngoscopy was done and view of larynx was graded according to Cormack and Lehane grading as given below;-

u Grade I: Visualisation of entire glottis.

u Great II: Visualisation of posterior commissure  only.

u Grade III: Visualisation of epiglottis only.

u Grade IV: Only soft palate seen.

All the vitals parameters like Spo2 , NIBP,  EtCO2, heart rate  was closely monitored throughout the surgical procedure.  During laryngoscopy , we were assisst the alignment of airway pathway by giving BURP  maneuver ( backward, upward, rightward pressure) and also can assist by using stylet , bougie in oral intubation and magill’s forceps in nasal intubation. Cormack and lehane  grading was done before giving tha BURP maneuver

Distribution of patients among different airway predictors

Predictive Te                             Class/Grade                            No. of Patients

MMT                                            Class I                                        

Class II                                         

Class III                                       

Class IV                                         

Jaw Protrusion                            Class A                                           

Class B                                          

Class C                                           

Thyromental Distance              ≥ 6.5 cm                                           

< 6.5 cm    

Table 2: Distribution of patients according to laryngoscopy view (92 patients)

S.No.            Predictive Test                                Cormack and Lehane Grading

Class III and IV                            Class I and II

1                          MMT

(8 Class IV patients

were not graded)

Class III (25)                                        

Class I and II (67)                               

2                  Jaw Protrusion

(8 MMT Class IV patients

were not graded)

Class B and C (29)                                               

Class A (63)                                

3             Thryomental Distance                                                                                                  

<6.5 cm (38)                       

(4 patients were not graded)

≥ 6.5 cm (54)

(4 patients were not graded)                

Statistical analysis

Data will be analyzed by Student’s t-test (paired and unpaired), one-way analysis of variance, and Fisher’s test using SPSS (23.0). Results will be reported as mean, standard deviation, and range values. A P value of less than 0.05 will be considered statistically significant.

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