A Trick for Difficult Intubation in a Micro Preemie

Several years ago, I was involved in a difficult intubation in a micro preemie. A micro preemie is a baby born weighing less than 1 pound, 12 ounces (800 grams) or before 26 weeks gestation. Micro preemies usually require intubation and prolonged care in the Neonatal Intensive Care Unit to manage immature lungs.

The actual technique of intubation for a micro premie can itself be problematic. Manipulating the laryngeal structures is difficult because the airway is so small compared to the intubator’s hands and equipment. In addition, a 2.5 endotracheal tube is extremely flexible and floppy. Here we discuss a technique for managing difficult intubation in a micro preemie as well as recommendations and precautions.

Micro Preemie Intubation Case Description

The baby was a 24 week micro preemie weighing 700 gm (1.5 lb.). The mother’s premature labor could not be stopped. The baby was delivered by Caesarian Section to minimize the risk of birth trauma. My anesthesia resident and I had administered a spinal anesthetic and the mother was stable, allowing me the ability to go to the infant warmer to see if I could assist with what appeared to be a difficult intubation.

The neonatologist was easily able to ventilate the baby with the NeoPuff. However, several attempts at intubation with a 2.5 ETT failed.

I could easily see the larynx when I tried. But the 2.5 tube was so flexible that it kept dropping into the posterior pharynx and entering the esophagus. Repositioning the head did not help. There was no pediatric stylet in the room. Precious minutes passed as we waited for a stylet and the pediatric GlideScope to come up from the main OR.

While we waited, I tried a new maneuver. I lifted the epiglottis with the Miller 0 blade. Being very gentle, I immediately rotated the blade 90 degrees to the left. This maneuver rotated the flange on the blade downward and gave me a shelf to support the tube.

Illustration of a technique for intubation in a micro preemie using direct laryngoscopy with a straight blade — Drawing demonstrating a technique for difficult intubation in a micro preemie by turning the Miller laryngoscope to the side. (a) Shows standard technique. (b) shows Miller blade rotated to the left to create a shelf that can support and guide a small, floppy endotracheal tube.

Next, I inserted the ETT on top of the slot on the Miller blade, rather than to the side as with the standard technique. With the ETT thus placed, the shelf provided by the blade flange supported the ETT and easily guided it directly between the cords.

Now intubated, we stabilized and transferred the baby to the NICU.

Micro Preemie Intubation

To be very clear, I am not recommending this as a new standard technique. I am suggesting this as a technique you could try when having difficulty intubating an infant. Here is an algorithm for difficult airway management of a newborn adapted from Johansen [1].

algorithm for management of a newborn infant with difficult airway, of use in intubation in a micro preemie

Micro Preemies Are High Risk Patients

All infants are at higher risk of airway complications, respiratory failure, and cardiovascular collapse due to their small size and the differences in anatomy and physiology from an adult. The micro preemie is in an especially high risk category, with little reserve when problems arise. In addition, until the micro preemie takes their first breath, lung compliance may be poor and mask ventilation therefore less effective. Margin for error is low.

Pediatric Respiratory Failure: A Peril In Young Children

Ventilation typically comes first in a resuscitation. However, when meconium is present, intubation to clear the larynx may be the first priority. Time is of the essence because a micro preemie can quickly become hypoxic. Hypoxia leads to bradycardia. Bradycardia worsens hypoxia and can quickly precipitate cardiac arrest.

The American Society of Anesthesiologists (ASA) closed claims analysis and the Pediatric Perioperative Cardiac Arrest (POCA) registry show that airway problems cause the majority of cases of cardiac arrest and brain death in pediatric patients, despite improvements such as monitoring of oxygenation, capnography, and anesthetic medications.

We thought we had prepared for this micro preemie birth with 2 neonatologists, and a staff anesthesiologist free to assist. I had watched the NICU nurse pre-check the laryngoscope blade, endotracheal tubes, neo-puff, and suction prior to surgery. What I didn’t do was check the equipment myself to make sure there was a pediatric stylet and an LMA.

Always Pre-Check Your Emergency Equipment

It was a mistake not to have a pediatric style that would fit a 2.5 ETT in the room. Fortunately we were easily able to ventilate the infant while we were working the problem — but that is never a given.

Was there a pediatric stylet in our cash cart? Yes. But in that moment of excitement, and with a stable patient, none of the 2 neonatologists, 1 anesthesiologist, 1 obstetrician, and 1 NICU nurse caring for the baby thought to ask for the crash cart — another error.

Make sure your anesthetizing locations have the correctly sized emergency equipment that you need for the types of patients cared for in that area. You can easily overlook tiny stylets and infant sized supraglottic airways unless you look for them. Test to make sure your (hopefully rarely used) pediatric laryngoscope batteries are working and that the laryngoscope blade light functions.

You don’t always need a stylet. An average infant would take a size 3 to 3.5 ETT, which is usually stiff enough to not flop downwards during intubation. With micro preemie intubation, size 2.5 ETTs are quite soft and often very flexible.

Every time you use a stylet, make sure that it does not protrude from the end of the ETT. Any stylet can seriously damage or tear the fragile trachea during insertion. Also ensure that you can easily remove the stylet by test sliding it in and out before placement.

photo of stylet protruding past endotracheal tube tip — **Serious tracheal damage can occur if a stylet protrudes past the tip of the endotracheal tube**

Practice emergency scenarios with your crash cart, and with emergency communication, before you need it.

Choice of Endotracheal Tube

Intubation of a micro preemie is challenging. The laryngeal anatomy of a micro premie is extremely small, very soft, and anatomically quite different than an adult.

photo demonstrating the anatomical differences of infant, toddler and adult larynxes to illustrate challenge of intubation in a micro preemie — The infant larynx is anatomically very different in shape and size than in the older child or adult. It’s much softer and more easily compressed and deformed. Edema causes significantly more obstruction.

Newborns come in different sizes.

Recommendations for ETT sizes rely in weight:

2.5 mm internal diameter (I.D) for < 1000 gm
3 mm I.D. for 1000 – 2000 gm
3.5 mm I.D. for > 2000 gm

Micro preemies usually take a size 2.5 mm endotracheal tube (ETT).

Choosing the correct size can be tricky as elasticity in the glottis can allow a larger endotracheal tube to be placed than the anatomy indicates [2]. Too large a tube can cause injury in the post glottic plane. After 40 weeks this elasticity disappears and injury from too large a tube occurs in the subglottic region. Multiple attempts easily cause bleeding and swelling of delicate tissues.

Be precise with depth placement to avoid inadvertent extubation or mainstem intubation, with the added risk of pneumothorax from over pressurizing a single lung. The American Academy of Pediatrics / American Heart Association Textbook of Neonatal Resuscitation recommends the 7, 8, 9 rule. Add 6 cm to the baby’s weight.

Depth of ETT (add 6 cm to baby’s weight in kg)

1 kg infant: 7 cm
2 kg infant: 8 cm
3 kg infant 9 cm

It’s imperative to verify breath sounds and recognize that formulas are guidelines and not absolutes. Flexion and extension of the baby’s head will raise and lower the tube tip in the trachea. As a result, mainstem intubation and extubation can occur at any time. Placement should be reverified every time you reposition the baby.

Some providers now recommend starting with videolaryngoscopy (VL) for micro preemie intubation, to start prepared for difficult intubation. [2] Videolaryngoscopy in infants and small children can itself be tricky. For a discussion of caveats for use of the Glidescope in pediatric patients see:

Intubating With a Pediatric Glidescope

Unfortunately, there’s not always a videolaryngoscope, or a small enough pediatric VL blade, available when you need one. Always be prepared for standard laryngosocopy.

Intubation of any patient can become a difficult intubation with little warning. Having a few tricks up one’s sleeve is helpful.

May The Force Be With You

Christine E. Whitten MD
author: Anyone Can Intubate: A Step-by- Step Guide, 5th Edition
&
Pediatric Airway Management: A Step-by-Step Guide

References

The Airway Jedi

Tips and tricks on intubation, airway management, anesthesia and safe patient care

A Trick for Difficult Intubation in a Micro Preemie

Micro Preemie Intubation Case Description