Laryngeal mask airway for surfactant administration in neonates: a practical guide

Indications

Thresholds for treatment will vary and need to be customized to individual institutional practices. General guidelines include:

1. Requiring non-invasive respiratory support (i.e. continuous positive airway pressure, high flow nasal cannula or non-invasive ventilation)
2. Weight ≥ 1250 grams (limited by size of currently available LMAs)
3. Clinical diagnosis of RDS (grunting, retracting, nasal flaring)
4. Requiring FiO2 ≥ 22%

Thresholds for treatment must take into account multiple factors, including exposure to prenatal steroids, gestational age, time since birth, FiO2 requirement, PaCO2, clinical symptoms and chest radiographic findings.

The goal of LMA surfactant administration is to intervene early enough in the course of RDS to avoid need for intubation and mechanical ventilation while avoiding unnecessary procedures in infants who would be successful on NIV alone.

Intervening early in the course of disease is important. Sub- analysis of the Roberts trial found that infants enrolled at a lower FiO2 and an earlier age were more likely to avoid intubation⁸. These findings were likely due to timing of the intervention in relation to progression of atelectasis. When considering FiO2 requirement, is it the trend, as opposed to the absolute value, that is most important, as this is an indirect marker for degree of atelectasis. Decreasing FiO2 indicates improvement and further time on NIV alone is prudent. Increasing FiO2 or worsening clinical symptoms indicate worsening atelectasis and LMA surfactant should be given to interrupt the progression. General guidelines include:

Contraindications

Contraindications include an etiology for respiratory distress other than RDS (such as congenital diaphragmatic hernia, pulmonary hypoplasia, hypoxic-ischemic encephalopathy, meconium aspiration syndrome, pneumonia), severe apnea despite caffeine administration, major congenital anomaly and/or abnormality of the airway or lungs. Presence of a pneumothorax is a relative contraindication.

In the case of high oxygen requirement, severe respiratory acidosis and/or significant atelectasis on chest radiograph, LMA surfactant is unlikely to be sufficient and would result in an unnecessary procedure and delay implementing appropriate treatment. In these cases, it is recommended to proceed directly to intubation and treatment with surfactant through an endotracheal tube.

The necessary equipment is discussed below. Products listed serve as examples of what is available and not intended to be an all-inclusive list or to promote a specific product. Providers should adapt the equipment to what is available or obtainable at their institution.

Necessary equipment includes:

Laryngeal Mask Airway (LMA)

LMAs fall under the category of supraglottic airway devices (SAD). Several companies manufacture SADs, with the LMA brand being the oldest and most widely recognized. In this practical guide, LMA will be used in the generic sense, referring to the category of SADs, rather than to a specific manufacture or device.

LMAs available for use in neonates differ in size, shape, re-use designation (single- use versus reusable), and cuff characteristics (inflatable versus non-inflatable). Examples of LMAs available and their characteristics are shown in Figure 1.

A study comparing LMA devices tested in a manikin model found the iGel^® (Intersurgical^®) to be superior⁹.

CO2 detector

Use of a CO2 detector during placement of the LMA allows for instantaneous feedback regarding proper positioning of the LMA over the trachea. CO2 detection methods are shown in Figure 2 and include:

1. Capnography: CO2 detection displayed as a waveform and digital value
2. Colorimetric: CO2 detection indicated by color change

The mask of the LMA rests in the posterior pharynx at the bifurcation of the tracheal and esophagus. Therefore, proper placement is crucial to ensure surfactant is directed into the trachea. If the mask is not fully over the tracheal opening, CO2 will still be detected, but surfactant will leak into the esophagus. Use of capnography dramatically improves “fine-tuning” of device placement. Compared to a colorimetric CO2 detector, which has subtle color change variance with the amount of CO2 detected, capnography allows the provider to subtly advance and retract the LMA to optimize mask placement over the tracheal opening.

Adapter

Use of an adapter allows for continuous positive end-expiratory pressure (CPAP) to be delivered without interruption throughout the entire procedure.

Note: The procedure can be performed without an adapter, but CPAP will be disconnected during administration of surfactant resulting in possible loss of functional residual capacity (FRC). Adapter options are shown in Figure 3 and include:

1. “T” adapter: Surfactant syringe attaches to side port, CO2 detector attaches to anterior hub
2. “Y” adapter: Surfactant administration occurs through one limb, CO2 detector attaches to second limb of the “Y” piece

If using a “Y” adapter, additional equipment is need and includes:

1. 8F Feeding tubeAllows for instillation of surfactant to the distal end of the LMA, thereby reducing the potential for air bubbles to develop in the body of the LMA during surfactant administration
2. ScissorsNecessary to cut the feeding tube to the proper length to administer surfactant to the distal end of the body of the LMA
3. Tape measureNecessary to measure the proper length to cut the feeding tube
4. Catheter adapter (aka Christmas tree adapter)Necessary to attach the syringe containing the surfactant to the feeding tube

Use of a “T” adapter is preferable as it allows for the syringe containing surfactant to be directly connected to the adapter and eliminates the need for the 4 additional items needed when using a “Y” adapter.

Ventilation device

Use of a ventilation device allows for PEEP to be given during the procedure, which is crucial for avoiding loss of FRC and potential de-recruitment of the lungs. A ventilation device also allows for PPV to be used to distribute the surfactant and to provide rescue breaths if desaturation or bradycardia were to occur.

1. T-piece resuscitator
2. Ambu bag (self-inflating, anesthesia bag)

Use of a T-piece resuscitator or anesthesia bag is preferable as PEEP is continuously maintained, even if PPV is not being administered. In contrast, when using a self-inflating ambu bag, PEEP is only administered when a positive pressure breath is delivered, therefore PPV breaths must be given throughout the procedure to maintain PEEP.

Additional equipment

1. Suction
2. Stethoscope

Rescue Equipment

Appropriately sized equipment should be readily available to convert to bag-mask ventilation or intubation if significant desaturation or bradycardia were to occur.

1. Mask
2. Intubation supplies

It is recommended to create an “LMA Surfactant Supply Kit” containing the supplies and procedure guidelines (Figure 4).

A flowchart of the procedure is shown in Figure 5.

Preparation

Premedication with a 24% sucrose solution and atropine (0.02 mg/kg IV over 1 minute) is recommended, but not required. Late preterm and term infants often benefit from a dose of lorazepam (0.05- 0.1 mg/kg IV).

Position the infant in the bed similar to positioning for intubation. Swaddle, while maintaining visualization of the chest, and have a provider dedicated to holding and observing the infant during the procedure. Maintain appropriate body temperature.

Position the infant supine, with the body straight, a shoulder roll in place, and head midline in the “sniffing” position. Proper positioning is essential for proper placement of the LMA. Aspirate stomach contents (NG/OG can remain in place). The NIV interface is left in place but can be removed if it interferes with placement of the LMA. Of note, the infant will not be receiving PEEP through the nasal device as the LMA will occlude the trachea, rather, PEEP will be delivered through the LMA. Attach the adapter to the proximal end of the LMA. Attach the CO2 detector to the adapter. If the LMA has a cuff, slightly inflate the cuff (just enough so the cuff is not completely collapsed, as this will help ensure the tip does not curl with placement).

Placement

Standing behind the infant’s head, open the mouth and grasp the tongue with the left hand. Insert the LMA with the right hand, using the index finger to guide the LMA along the curvature of the hard palate. Gentle pressure may be required initially as the cuff tends to grasp the tongue, but will insert easily once past the tongue. Advance the LMA until CO2 is detected and resistance to further advancement is felt. On larger infants, the index finger may not be long enough to fully advance the LMA. Further advancement can occur by holding the body of the LMA between the thumb and index finger. Once resistance is felt and CO2 detected, the mask is in the pharyngeal “pocket”. Once in the pocket, slightly advance and then slowly retract the LMA. This maneuver places the tip of the mask in the esophagus and upon retraction, captures the epiglottis and holds it against anterior wall, maintaining the epiglottis in the open position. Optimize placement over the tracheal opening by optimizing CO2 detection and while subtle adjustments (advancement and retraction) are made with the LMA. Once optimized, hold the LMA in place and attach the ventilation device to the CO2 detector.

Initiate ventilation and confirm proper positioning indicated by the CO2 detector and listening for bilateral breath sounds. If breath sounds and CO2 detection are not optimized, subtly readjust the LMA. If subtle re-adjustments do not result in proper positioning, remove the LMA (deflate cuff prior to removal if using an LMA with an inflatable cuff), stabilized the infant and repeat LMA placement. Placement attempts should be limited to 30 seconds.

Surfactant administration

Once proper placement of the LMA is achieved, administer surfactant in 2 ml aliquots. Administer the next aliquot once surfactant had cleared from the LMA, as determined subjectively by feel if using bag ventilation, SaO2 ≥ 94% and heart rate ≥100 beats per minute (bpm). If using PPV, surfactant has usually clears within 3-4 breaths. After administration of the last aliquot, continue PEEP and/or PPV until SaO2 ≥ 94% and heart rate ≥100 bmp. Remove the LMA (if using an LMA with an inflatable cuff, deflate cuff prior to removal).

Place infant back on NIV and adjust as needed. Verify proper OG/NG placement and readjust or replace if needed. Aspirate stomach contents, noting amount aspirated relative to amount administered (gastric aspirate is an imprecise indicator, as all of the surfactant may not have been aspirated and/or the gastric aspirate may represent gastric secretions or other medications in addition to surfactant, but relative amount does provide an estimate of potential leakage around the cuff). Return the infant to their normal position in the bed.

Physiologic stability

During the procedure, if SpO2 < 75% or heart rate <100 bpm, the procedure should be interrupted and PPV administered via the LMA or a mask until Sp02 > 94% and heart rate > 100 bpm. If the infant does not respond satisfactorily, appropriate therapy, which may include intubation and mechanical ventilation, should be instituted to achieve stable cardiopulmonary function.

Repeat dosing

If the LMA is positioned too high or too deep in the pharynx, the cuff will not form a seal and surfactant will leak into the esophagus. After the procedure, if there is a large percentage of the dose aspirated from the stomach and a lack of clinical response (i.e. lack of decrease in FiO2/ respiratory support requirement within the first minutes after instillation), the procedure may be repeated immediately through the LMA.

After the initial procedure, if additional doses of surfactant are deemed necessary by the clinical provider, additional doses may be given through the LMA at the appropriate time.

Complications

While placement and surfactant administration through an LMA generally results in minimal fluctuation in physiologic parameters, bradycardia, hypoxia, hypotension and/or hypertension may occur and should be anticipated. The infant should be continuously monitored and personnel skilled in bag- mask ventilation and intubation should be present at the bedside.

Since the LMA rests in the posterior pharynx and surfactant is administered above the glottis (as compared to administration via an endotracheal tube which is delivered below the vocal cords), laryngospasm is a potential complication. In animal and human trials^8,10-14 and in clinical experience, laryngospasm has not be reported. However, because it is a theoretic risk, a muscle relaxant and personnel skilled in intubation should be readily available.

Provider training

In the Roberts trial⁸, providers had minimal or no prior experience placing an LMA. Training occurred by reviewing the procedure on a manikin. Successful placement of the LMA was achieved in < 35 seconds and on the first attempt in the majority of patients¹⁵. Providers stated they felt comfortable with the procedure after 2 experiences.