| Literature DB >> 28074820 |
Arindam Choudhury1, Nishkarsh Gupta2, Rohan Magoon1, Poonam Malhotra Kapoor1.
Abstract
The difficult airway (DA) is a common problem encountered in patients undergoing cardiac surgery. However, the challenge is not only just establishment of airway but also maintaining a definitive airway for the safe conduct of cardiopulmonary bypass from initiation to weaning after surgical correction or palliation, de-airing of cardiac chambers. This review describes the management of the DA in a cardiac theater environment. The primary aims are recognition of DA both anatomical and physiological, necessary preparations for (and management of) difficult intubation and extubation. All patients undergoing cardiac surgery should initially be considered as having potentially DA as many of them have poor physiologic reserve. Making the cardiac surgical theater environment conducive to DA management is as essential as it is to deal with low cardiac output syndrome or acute heart failure. Tube obstruction and/or displacement should be suspected in case of a new onset ventilation problem, especially in the recovery unit. Cardiac anesthesiologists are often challenged with DA while inducing general endotracheal anesthesia. They ought to be familiar with the DA algorithms and possess skill for using the latest airway adjuncts.Entities:
Mesh:
Year: 2017 PMID: 28074820 PMCID: PMC5299825 DOI: 10.4103/0971-9784.197794
Source DB: PubMed Journal: Ann Card Anaesth ISSN: 0971-9784
Common airway assessment parameters and their implication
| Test | Difficulty in managing |
|---|---|
| Teeth | Difficult insertion of laryngoscope |
| Ability to protrude mandibular teeth anterior to maxillary teeth (upper lip bite test)[ | Determines subluxation of thyromental joint and important for laryngoscopy. Inability to do so (Class III) indicates difficult laryngoscopy and intubation |
| Class I: Lower incisors can bite the upper lip above the vermilion line | |
| Class II: Lower incisors can bite the upper lip below the vermilion line | |
| Class III: Lower incisors cannot bite the upper lip | |
| Interincisor distance (mouth opening) | Preferably >3 cm minimum mouth opening should be at least more than the flange of the laryngoscope blade or LMA thickness for successful management |
| Mallampati classification (sitting position, maximum mouth opening, and protrusion of the tongue) | Assesses oropharyngeal space and a class more than III indicates difficult intubation |
| Class I: Soft palate, fauces, uvula, and pillars seen | |
| Class II: Soft palate, fauces, and uvula seen | |
| Class III: Soft palate and base of uvula seen | |
| Class IV: Soft palate not visible | |
| Palate anatomy | No cleft (laryngoscope blade may enter the cleft)/narrowing or high arching (less space to insert or laryngoscope blade) |
| Thyromandibular distance | At least 6 cm for tongue to fit into mandibular space. A lower distance may make larynx anterior and difficulty expected |
| Submandibular compliance | Decreased compliance makes laryngoscope manipulation difficult |
| Length of neck (the distance from the suprasternal notch to the mentum, measured with the head fully extended on the neck with the mouth closed)[ | Short neck (<12 cm) reduces the ability to align airway axes |
| Neck thickness (at the level of the thyroid cartilage)[ | Increased neck circumference may indicate difficult intubation |
| Neck movements (required to alignment of oral, pharyngeal axis for intubation) can be measured using a goniometer or a rough visual estimate[ | A range of neck movement (including both flexion and extension) <80° may make intubation difficult |
Figure 1Midline long-axis ultrasonogram of the lower airway (extrathoracic) depicting the cricothyroid membrane (vertical arrow)
Figure 2(a) A customizable difficult airway cart with contents of a drawer; (b) cart with fiberoptic bronchoscope cradle and video display unit attached to the cart
Figure 3Various supraglottic airway devices in evolution (a) Classic laryngeal mask airway (1st generation), (b) Proseal laryngeal mask airway (2nd generation), (c) iGel and (d) Baska airway (3rd generation)
Figure 4Various video laryngoscopes in use today easing many difficult airway management
Suggested content of an ideal difficult airway cart
| DA cart contents |
|---|
| Face mask - all sizes |
| Airways - different sizes |
| SGADs (e.g., LMAs - all sizes, ILMA of assorted sizes) |
| Laryngoscope (at least two sets) including video laryngoscopes [ |
| Magill’s forceps (two sizes) |
| Suction catheters (all sizes) |
| Bougies or intubating stylets |
| ETTs (all sizes) |
| ILMAs |
| Flexible fiberoptic laryngoscope |
| Tracheostomy kit (e.g., Ciaglia Rhino PCT kit) (equipment suitable for emergency) |
| Retrograde intubation equipment (invasive airway access) |
| Basic medications and LAs |
| ETTs securing tapes |
| Exhaled CO2 (EtCO2) detection devices |
| Tube exchangers with O2 insufflation facility |
PCT: Percutaneous tracheostomy, ILMAs: Intubating laryngeal mask airways, LMA: Laryngeal mask airway, LA: Local anesthetic, SGAD: Supraglottic airway devices, DA: Difficult airway, ETT: Endotracheal tube
Different reflexes and regional airway blocks to be given before awake intubation
| Reflex | Nerve blocked |
|---|---|
| Gag | Glossopharyngeal nerve (internal or external approach) |
| Laryngeal closure reflex | Internal branch of superior laryngeal nerve (near greater cornua of hyoid bone) |
| Cough reflex | Internal branch of superior laryngeal nerve and recurrent laryngeal nerve (transtracheal injection of LA) |
| Cardiovascular reflex response (hypertension, tachycardia, and bradycardia) | Laryngeal and glottis receptors supplied by glossopharyngeal and vagus nerves |
| Palatine nerves and anterior ethmoidal nerve innervate the nasal cavity | Cotton soaked in LA is passed is placed for 5-15 min |
LA: Local anesthetic
Figure 5Algorithmic approach to physiologic and anatomic difficult airway followed at our department (adapted partly from American Society of Anesthesiologist Difficult Airway Algorithm, 2013)