RIZKY PUTRI AUSHIVA

Assessment Before AirwayManagement

Introduction

Since the original case series describing physical features associated with difficult direct laryngoscopy and difficult tracheal intubation (DTI), several upper airway diagnostic screening tests have been proposed.

Definitions and incidence of airway difficulty

Risk Factors

Several studies have identified risk factors associated with management of the difficult airway. Knowledge of these could help plan management and play an important role in airway assessment.

Risk Factors

1. Mask Ventilation2. Laryngeal Mask Airways3. Video Laryngoscopes4. Difficult Mask Ventilation & Difficult

Laryngoscopy5. Age6. Cricothyroidotomy7. Neuromuscular Blocking Agents

1.Mask Ventilation

Five independent risk factors for difficult mask ventilation were found using multivariate analysis, including age greater than 55 years, body mass index (BMI) greater than 26 kg m2, presence of a beard, lack of teeth, and a history of snoring.

2. Laryngeal Mask Airways

Failure occurred in 1.1% of the population and was associated with significant hypoxia, hypercapnia, or airway obstruction. Forty-two percent presented with inadequate ventilation related to a cuff leak. Independent risk factors for failed uLMA in this study were surgical table rotation, male sex, poor dentition, and increased BMI.

3. Video Laryngoscopes

The risk factors for GlideScope failure were altered neck anatomy, presence of a surgical scar, radiation changes, or the presence of a mass.

4. Difficult Mask Ventilation & Difficult Laryngoscopy

Independent risk factors were found, including age of 46 years or older, BMI of 30 kg/m2 or greater, male sex, Mallampati class III and IV, neck mass or radiation, limited TMD, sleep apnea, presence of teeth, presence of a beard, thick neck, limited cervical spine mobility, and limited jaw protrusion.

5. Age

The incidence of DTI was less in young adults compared with their older cohorts; the metrics associated with DTI, such as thyromental distance, cervical spine movement, interincisor distance & grade of dentition, decreased with age, whereas the Mallampati score, cervical spine rigidity & the ratio of Arne greater than 11 increased with age.

6. Cricothyroidotomy

A study examining the accuracy of percutaneous identification of the cricothyroid membrane in female obese and nonobese patients found that misidentification of the cricothyroid membrane was more likely in obese patients, particularly those with increased neck circumference.

7. Neuromuscular Blocking Agents

There was a steady decrease in the use of neuromuscular blocking agents over the period of the study, yet the frequency of DTI remained relatively unchanged. It was also found by multivariate analysis that patients who received nondepolarizing neuromuscular blocking agents were at greater risk of DTI than those who received depolarizing NBA.

Patient Factors

An expert panel found that patient factors were the most frequent causal and contributory factors (77%) of airway complications. Certain patient factors have been found to be associated with difficult airway management and are, therefore, worth identifying in the preoperative airway assessment.

Patient Factors

1. Cervical Spine Limitation2. Obesity3. Acromegaly4. Pregnancy5. Thyroid Hypertrophy

1. History of the previous difficult tracheal intubation

It was found that 24% (21%–28%) of patients who had previously experienced difficulty with direct laryngoscopy and tracheal intubation also experienced difficulty with tracheal intubation on another occasion.

Previous failed tracheal intubation by direct laryngoscopy was a strong predictor for future failed intubation.

2. Cervical Spine Limitation

Movement of the cervical spine is an important component of direct laryngoscopy and tracheal intubation. The best position for direct laryngoscopy requires 35 neck flexion & face plane extension to 150. The Mallampati test, thyromental distance & mouth opening are all impaired by cervical spine limitation, which suggests the importance of adequate neck movement when trying to predict DTI.

3. Obesity

The methodology and size of this study lend credibility to this result, which shows a high BMI as a weak but statistically significant predictor of difficult and failed intubation.

4. Acromegaly

Acromegaly is associated with macroglossia, enlarged and distorted laryngeal anatomy, and prognathism. The incidence of DTI in patients with acromegaly is 4 to 5 times higher than people without acromegaly.

5. Pregnancy

In this study, risk factors included a maternal age of 35 years or older, weight of 90 to 99 Kg, and the absence of active labor.

6. Thyroid Hypertrophy

Palpable goiter, endothoracic goiter, thyroid malignancy, and airway deformation were not found to be specific predictors of DTI; however, MMP class 3 and 4, interdental distance less than 35 mm, TMD less than 6.5 cm, cervical spine limitation less than 80, short neck, and retrognathia were significantly reliable predictors of DTI.

Limitation of airways test in emergency medicine, intensive care and pediatrics DTI in the intensive care unit (ICU) is associated with high

mortality. An intubation score has been developed and independently validated in a multicenter trial. The score is based on patient, pathology, and operator factors. Called the MACOCHA score, factors and weighted scores include Mallampati class III and IV (5 points), apnea syndrome (obstructive) (2 points), cervical spine limitation (1 point), opening mouth less than 3 cm (1 point), coma (1 point), hypoxia (1 point), and anesthesiologist nontrained (1 point). The 12-point score has limits of zero (easy) and 12 (very difficult).

Risk factors in Pediatric in this study included children undergoing cardiac and oromaxillofacial surgery, ASA physical status II and IV, Mallampati class III and IV, and children with a low BMI.

Summary

Assessment of the airway is an important component of preparing patients for safe airway management. Improving the prediction of difficult airways can be achieved by adopting objective assessment. Review of the literature suggests that bedside airway tests are very poor predictors of airway difficulty.

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