Intubation  How to intubate intensive care patients

It is important that all physicians working in intensive care have at least rudimentary abilities at endotracheal intubation. Further, you must be aware of the potential problems that occur in the aftermath of intravenous induction of anesthesia and application of positive pressure ventilation. Below is a description of the process of intubation:

1.   Head positioning: this is the single most important aspect from a nursing point of view. Do not remove the pillow. The correct position for the head is “sniffing the morning air”, with the neck slightly flexed and the head extended. One places a pillow under the head and neck but NOT under the shoulders. This allows a straight line of vision from the mouth to the vocal cords.

2.    The laryngoscope (size 3 for a woman, size 4 for a man) is introduced into the right hand side of the mouth (it is held by the left hand). The tongue is swept to the left and the tip of the blade is advanced until a fold of skin / cartilage is visualized at twelve o’ clock. This is the epiglottis, and this sits over the glottis (the opening of the larynx) during swallowing. 

3.   The tip of the blade is advanced to the base of the epiglottis, known as the vallecula, and the entire laryngoscope is lifted upwards and outwards. This flips the epiglottis upwards and exposes the glottis below. An opening is seen with two white vocal cords forming a triangle on each side. Behind this there is a darkened recess, the trachea, and tracheal rings are often visible. Occasionally, the whole larynx cannot be visualized, this may be due to poor head position (readjust it) or an “anterior larynx. To improve visibility, the assistant can press down on the larynx (external laryngeal compression. If this fails to allow visualization of the larynx, then you are in a difficult position. If you have a partial view, you can slide a gum elastic bougie under the epiglottis and between the cords, and thread the endotracheal tube (ett) over it. If you have no view, an attempted blind intubation is worthwhile (but don’t cause airway trauma by recurrent attempts): slide the ett under the epiglottis and point upwards – it should enter the larynx.

4.    The tip of the endotracheal tube is advanced through the vocal cords and once the cuff has passed through, one stops advancing. The tube is secured at this level and the cuff inflated.

5.    The cuff is inflated until the air leak (around the cuff) is abolished; no more, no less. Too high a cuff pressure will necrose the tracheal mucosa (by cutting off its circulation) and cause a tracheal stricture.

6.   Endotracheal intubation is confirmed by the presence of bilateral breath sounds and end tidal carbon dioxide measurement. Be careful that you have not advanced too far: a normal male rarely requires a tube to be advanced more than 23cm, a female 21cm.

7.   The tube may be secured in a variety of ways (tape is becoming increasingly popular), all that is important is that it is held tightly, and can not slide up and down the trachea. It is preferable to secure the tube to the upper jaw (the maxilla) than to the lower one (the mandible) as this moves up and down.

8.   It is usual to insert a nasogastric tube for gastric suctioning and feeding at the same time as intubation takes place.

9.   It is worthwhile to suction out the lungs below the level of the tube following intubation, and collect  specimen of mucus for microbiology.

10. The ett is connected to the ventilator via a catheter mount.

Giving Drugs to Assist Intubation

The administration of drugs is determined by the clinical situation: awake patients require hypnosis and neuromuscular blockade. Hypotension is a contraindication to some anesthesia induction agents.

When giving anesthesia patients for emergency surgery, anesthesiologists use a process called a “rapid sequence induction”. The objective is to secure the airway rapidly and prevent soiling of the lungs with gastric contents.

The patient goes asleep with the aid of an intravenous induction agent: thiopental, propofol or etomidate. These cause hypnosis and amnesia. They have a common problem in that they cause peripheral vasodilatation (propofol>thio>etomidate), and cause a drop in the blood pressure.

To rapidly intubate the larynx, it is important to have a high degree of muscle relaxation very quickly. The drug used for this is succinylcholine. This agent acts by causing every muscle in the body to contract, and subsequently relax. The result of this is the sudden release of a lot of potassium into the bloodstream. Succinylcholine is contraindicated if there is hyperkalemia, as it may cause cardiac arrest.

The Procedure of Rapid Sequence Induction / "Crash" Intubation

Preparation:

Drugs: thio/ propofol/ etomidate/ midazolam, succinyl choline, atropine, ephedrine/phenylephrine.

Endotracheal tubes: a variety of sizes available and cut and checked (to make sure that the cuff is intact -–ie. Not punctures)

Laryngoscopes – 2 functioning laryngoscopes with a variety of blades.

Suction – on and under the pillow.

A Gum elastic bougie – to railroad the ETT is there is difficulty in placing the ett.

An intravenous cannula, with a free-flowing drip

Monitoring:

blood pressure, ECG, pulse oximetry, end tidal CO2 (if available).

Assistant:  this person must be familiar with the RSI process and be able to apply cricoid pressure. The cricoid cartilage is the ring felt below the larynx. If this is displaced posteriorly, because it is circular shaped and solid, it compresses and closes the oesophagus (which lies behind it). This prevents passive regurgitation of gastric contents.

Induction:

The patient is preoxygenated for a full three minutes, to wash all of the nitrogen out of the lungs and create a reservoir of O2.

Thiopental or etomidate is administered, cricoid pressure is applied, followed by succinylcholine (never ever give this first).

The patient is asleep when the eyelash reflex is lost, and relaxed when fasciculation stops.

The patient is intubated, the cuff inflated and the tube secured. Cricoid pressure is not released until the intubator is happy that the tube is correctly placed.

Not all critically ill patients will tolerate a standard rapid sequence induction. Classically these patients are intubated for failure to ventilate or oxygenate, and they are usually hypoxemia and acidotic (respiratory and metabolic). Other problems that may influence the outcome of intubation are:

Hypotension  hypovolemia: absolute due to hemorrhage or third space fluid loss, relative due to compensation, which may be exposed when there is a loss of vascular tone. 

Critically ill patients are often drowsy, acidotic, hypotensive and dehydrated. Even a small amount of peripheral vasodilatation (with propofol) may expose/unmask intravascular dehydration and send the blood pressure spiraling downwards.

Hypnotic agents and neuromuscular blockers are not always necessary: at a cardiac arrest, or with an obtunded patient, the patient can be intubated without difficulty. Additionally, it is often necessary to use other techniques to relax the patients airway for intubation:

Options:

1.       Awake intubation +/- local anesthesia applied topically.

2.       Sedation with midazolam +/- local anesthetic.

3.       Midazolam + succinylcholine

4.       Ketamine + succinylcholine (small babies).

5.       Thiopental or propofol + succinylcholine

6.       Etomidate + succinylcholine

It is essential that all resuscitative agents are available following intubation. Always have an ampule of phenylephrine or ephedrine at hand.

Copyright Patrick Neligan 2001-2002

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