Airway Skills 10:
Topical Anesthesia
Prepare the patient for awake intubation.
Consider awake intubation when the patient is breathing but needs to be intubated and has a condition or anatomic problem that may make rapid sequence intubation unsuccessful or dangerous. A blind approach may be used, combined with local anesthesia and analgesia. Examples of blind approach are using light-guided intubation, an intubating laryngeal mask airway, nasotracheal intubation, or retrograde intubation.
- Anesthetize the upper airway by ventilating the patient with oxygen administered through a nebulizer, such as is used for albuterol nebs in asthma therapy. Add 4 mL of 4% lidocaine and 2 mL of 0.25% phenlephrine (Neosynephrine) to the nebulizer. A single drop of 10% phenylephrine as is used to dilate pupils may be added instead of the 0.25% phenylephrine. It works best to have your pharmacy provide the solution ahead of time. Assist the patient's respirations. Phenylephrine dilates the pupils, so take care to avoid getting mist in the eyes. Even nasal drops may have this effect, so note the size of the pupils before and after administration.
Phenylephrine shrinks mucous membranes and makes the lidocaine more effective. Phenylephrine helps prevent bleeding and trauma to narrow passages. If systemically absorbed, as when inhaling a mist containing phenylephrine, it may raise blood pressure. Phenylephrine has little inotropic or chronotropic effects on the heart, however.
The same mixture of lidocaine and phenylephrine can be drawn into a small syringe and injected into the nares using mucosal atomization devices for spraying the nasal cavity and the pharynx. A 10% lidocaine spray may also be used; (PEDS) but beware of overdosing a child. A single spray contains 10 mg lidocaine.
When coughing is to be avoided, 4% or 2% lidocaine may be injected through the cricothyroid membrane.
- Airway topical anesthesia may be frightening to some patients. This is because it results in the loss of the ability to feel one's self breathe, swallow, and cough. Close observation is necessary. The loss of gag reflexes is also of concern.
Reference
Sanchez A, Trivedi NS, Morrison DE. Preparation of the patient for awake intubation in Airway management, principles and practice, Benumof JL, Ed. St. Louis, 1996, Mosby;159-182.