Analysis of anterior soft tissue thickness using ultrasonogram, body mass index and neck circumference in predicting difficult intubation

Abstract

INTRODUCTION AIRWAY ASSESSMENT: The purpose of undertaking airway assessment is to diagnose the potential for difficult airway for: a. Optimal patient preparation b. Proper selection of equipment and technique, and c. Participation of personnel experienced in the difficult airway management. This usually leads to a successful airway management. On the other hand, determining that the airway is normal, avoids time consuming, invasive, and potentially more traumatic methods of securing the airway, from being adopted. The essential components of airway assessment are history taking, general examination of the patient and specific tests/indices to predict difficult airway. Previous anesthesia records may reveal a documented history of difficult airway. History of previous surgery, burns, trauma or tumor in and around the oral cavity, neck or cervical spine should be asked. A general examination of the patient should include recognition of anatomic factors that cause difficult laryngoscopy and intubation. This requires a disciplined, complete examination. The anesthesiologist must understand and identify pathologic and physiologic factors that may impair laryngoscopy and intubation. Carrying out assessment tests/indices of difficult airway should follow a general examination and if time permits, try to use more than one assessment method to increase the accuracy of airway assessment. DIFFICULT AIRWAY: Difficult airway clinical situation in which a conventionally trained anesthesiologist experiences difficulty with face mask ventilation of the upper airway, difficult tracheal intubation (or) both. ULTRASONAGRAM TO MEASURE THE PRETREACHEAL SOFT TISSUE THICKNESS: Patient shifted to ultrasongram room and measures the pretreacheal soft tissue thickness at three levels: 1. Vocal cords (Zone I), 2. Thyroid isthmus (Zone II), 3. Suprasternal notch (Zone III). NECK CIRCUMFERENCE: Measured in cm at the level of thyroid notch. BODY MASS INDEX: Body mass index is the body weight in kilograms over height in meters squared. AIM OF STUDY: The aim of the study is to analyse pretracheal soft tissue using ultrasonagram, body mass index and neck circumference in predicting intubation difficulties. METHODOLOGY: It was a prospective, double blinded study conducted in Department of Anaesthesiology, Madras Medical College-GGH. 200 adult patients satisfying inclusion criteria were enrolled in this study. Inclusion Criteria: 1. Elective adult surgical patient requiring general endotracheal anaesthesia. 2. Males and Females. 3. ASA Physical Status 1-2. 4. Age 18 years of age and older. 5. Who have given valid informed consent. Exclusion Criteria: The patients with following conditions are not included in this study. 1. Patients not satisfying inclusion criteria. 2. Patients requiring special techniques for intubation such as rapid sequence induction. 3. Patients intubated prior to surgery. 4. Patients with severe cardiovascular, hepatic or renal disease, mental illness. 5. Are unconscious or very severely ill. 6. Need for nasal intubation. Materials : 1. Macintosh laryngoscope - current standard Device. 2. High frequency (7.5mhz) Ultrasound machine. 3. Weighing machine calibrated to 1 Kg. 4. Measuring tape calibrated to 0.5 cm. 5. Goniometer. SUMMARY: This study was conducted in the Department of Anaesthesiology, Madras Medical College, Chennai-3. 200 patients were selected randomly and after taking history, airway assessment, anterior soft tissue thickness using ultrasound, Body mass index and neck circumference taken up for the study. After analysing the statistical data it is found that the anterior soft tissue thickness using ultrasound, Body mass index and neck circumference, significantly predicted the difficult intubation. CONCLUSION: It can be concluded that the anterior soft tissue thickness using ultrasound, Body mass index and Neck circumference, significantly predicted the difficult intubation and can be an important aid for the anaesthesiologist.