The Young Airway Prehospital assessment & management of pediatric respiratory distress

 

 
 
 

Michael F. Murphy, MD, FRCPC | From the June 2008 Issue | Saturday, July 26, 2008


Case presentation

A 12-year-old male is accidentally shot in the face by a friend with a 410 shotgun at a distance of about 5 yards. His friend assists him in walking about a half mile out of the woods and summons 9-1-1. The location is rural, with a 20-minute response time and a 30-minute travel time to a hospital. Air transport is not possible due to fog and rain.

When you arrive on scene, the patient is alert, talking and anxious (see photo). He's experiencing increasing difficulty swallowing. His initial vital signs include a pulse of 120, a blood pressure of 160/90, a respiratory rate of 24, and an oxygen saturation of 97% on room air. There's no stridor, and his voice is normal. A non-rebreather mask is applied, and his oxygen saturation increases to 100%.

His face is peppered with buckshot entry wounds on the left side, and there's a moderate degree of edema. The eyes are spared. There_s no neurological deficit. He can open his mouth, and there's no swelling apparent inside the mouth or deviation of any anatomical structures.

Your neck exam reveals full and painless range of C-spine motion. There's mild to moderate swelling of the left side of the neck. Examination of the chest reveals no obvious subcutaneous air, and the remainder of the physical examination is normal.

You start an 18-gauge IV with lactated Ringers in an antecubal area, and your crew packages the patient for transport to the hospital.

But what about his airway, which is likely to become obstructed? Should it be managed in the field? If his vitals deteriorate, how will you proceed?

Assessment of the pediatric respiratory system

Experience often lends providers a "sixth sense" about adult patient assessment. However, because pediatric care makes up just 10Ï20% of our prehospital patient population, many otherwise competent and experienced EMTs and paramedics often fear the assessment and care of critically ill or injured pediatric patients. (1) For this reason, we should rely on well-established and easily reproduced assessment tools for our pediatric cases.

The Pediatric Assessment Triangle (PAT) is a widely published and recognized tool to facilitate assessment of pediatric patients. The PAT relies on three key components -- appearance, work of breathing and circulation -- to quickly assess and triage patients into treatment categories of "sick" and "not sick." (2)

Appearance: How does the patient look? Is there acknowledgement of your presence? This first assessment is the most important aspect of the PAT.

A general impression of appearance quickly reflects adequacy of ventilation, oxygenation, brain perfusion and central nervous system (CNS) function. (1) This initial assessment enables you to quickly prioritize your airway-management plan.

Loud, boisterous crying is the best sound any prehospital provider can ever hear going into an unknown pediatric emergency. Conversely, a flaccid, unresponsive child with a fixed gaze should be considered seriously ill, requiring immediate action to ensure adequate ventilation and oxygenation.

TICLS -- which stands for tone, interactiveness, consolability, look/gaze, and speech/cry -- is a useful mnemonic for assessing the pediatric patient for oxygenation failure and CNS dysfunction. This tool expands the first leg of the PAT and reminds you to examine all aspects of the patient's appearance.

Utilizing the PAT appearance and TICLS assessment tools allows you to better detect subtle abnormalities than the more conventional AVPU (alert, voice, pain, unresponsive) scale. (1)

Work of breathing: Unlike the adult patient, a child's work of breathing is often a better assessment of oxygenation and ventilation status than breath sounds and respiratory rate. Work of breathing reflects the patient_s attempt to overcome abnormalities in respiratory function and the patient's ability to exchange gas. (2)

This doesn't mean breath sounds should not be auscultated in the pediatric patient; however, an evaluation of the work of breathing in pediatric patients will alert providers of imminent respiratory arrest before auscultation will.

During this leg of your assessment, the first step can often be accomplished without using a stethoscope. Abnormal, audible airway sounds can quickly alert providers to upper airway status. Snoring, difficulty swallowing secretions and a muffled voice (aka, "hot-potato" voice, as though the patient is rolling hot potato with their tongue) or hoarse voice are subtle indicators of upper airway obstruction.

Stridor (a high-pitched, audible sound on inspiration) is a particularly sinister finding in pediatric patients with acute airway disorders and heralds total obstruction that's often insurmountable by bag-mask ventilation. Croup, bacterial infections, foreign bodies, edema or bleeding can all result in upper-airway obstructions, which are clearly audible on work of breathing assessment. (2)

Grunting, like the pursed-lip expiration in adults with chronic obstructive pulmonary disease, provides a degree of positive pressure to be maintained throughout the expiratory phase and may be thought of as "auto-PEEP" (positive end-expiratory pressure). This maneuver enables you to stent open small airways and alveoli facilitating gas exchange. (2)

Pediatric patients who have an acute respiratory disorder and exhibit grunting are usually already moderately or severely hypoxic, reflecting poor gas exchange. Conditions most often associated with grunting in children include pneumonia and pulmonary edema. (1) Additional signs of increased work of breathing include displaying the sniffing position while breathing; the tripod position; retraction of the sternal notch, supraclavicular areas and intercostals spaces (a sign seen more in children than adults due to the pliability of their tissues); head bobbing; and nasal flaring.

The sniffing position is when the patient spontaneously flexes their neck slightly forward and extends their head up and back in order to open a partially obstructed upper airway. The tripod position is when the patient has an erect torso and their arms planted firmly on a horizontal surface to maximize the mechanical advantage of the accessory muscles of respiration in the neck and chest. Head bobbing is typically in response to the child's use of accessory muscles and the attempt to produce maximal negative intrathoracic pressure for inspiration.

The Silverman-Anderson Index is an assessment scoring system that evaluates five parameters of work of breathing and assigns a numerical score for each parameter (see Table 1, p. 60). Each category is scored as "0" for normal, "1" for moderate impairment or "2" for severe impairment. Parameters assessed are retractions of the upper chest, lower chest and xiphoid; nasal flaring; and expiratory grunt. (3) Normally functioning children should have a cumulative score of 0, whereas critically ill and severely depressed children will have scores closer to 10.

The last physical assessment tool used to evaluate work of breathing should be auscultation of the lower airways with a stethoscope. Because a child's chest is so small, stethoscope placement differs slightly from auscultation of an adult's chest. The transmission of sounds from areas distant from the stethoscope can be a problem when assessing breath sounds in small children. For this reason, place the stethoscope bell near the armpit to maximize transmitted breath sounds. (4)

Wheezing, the movement of air through partially blocked smaller airways, is the most common lower airway sound heard in children with respiratory compromise. Initially, wheezing is heard only on exhalation and upon auscultation with a stethoscope. But as the degree of obstruction increases, it may be heard in both inspiration and expiration, and may even be audible to the naked ear.

Once a patient becomes extremely fatigued, airflow velocity begins to fatigue and wheezing may attenuate and disappear, a pre-arrest finding. Therefore, it's necessary to treat wheezing aggressively in the early stages before the increased work of breathing leads to fatigue and respiratory arrest. (1)

Circulation: The goal is to determine the adequacy of cardiac output. (1) Key findings in the distressed child are related to signs of poor oxygenation, such as peripheral or central cyanosis. Bluish tinting to the skin and/or mucous membranes reflects significant hypoxemia. Corrective action regarding airway management and optimal oxygenation must be made a priority.

Beyond the PAT

EMS providers must also consider respiratory effort and rate when assessing the pediatric airway (see Table 2). Tachypnea is often the first manifestation of respiratory distress in children. (4) Irrespective of cause, rapidly breathing children will eventually tire and respiratory arrest will ensue.

Slow respiratory rates in acutely ill children, often associated with a disorder of mentation or decreased level of consciousness, is a particularly ominous sign. (4) Be alarmed if an acutely ill child has a slowing respiratory rate. Do not assume slowing rates equal improvement.

Lastly, diagnostic equipment can be very helpful in assessing the child's respiratory system (including the upper airway). In children, pulse oximetry readings above 94% saturation are generally considered acceptable. A reading below 90% during administration of 100% oxygen is an indication for immediate intervention with assisted ventilations.

However, crews must be cautious not to discount or disregard symptoms or signs of respiratory distress in a child simply because the pulse oximetry reading is above 94%. This is because children in respiratory distress or failure can maintain acceptable oxygen saturation levels by increasing work of breathing and respiratory rate until the point of respiratory arrest, particularly if supplementary oxygen is being administered. Thus, pulse oximetry should always be used in conjunction with work of breathing assessment.

Anatomical&physiological factors

The fundamental priorities of prehospital pediatric airway management are: optimizing oxygenation, ventilation and airway protection. Decisions regarding airway management must be made rapidly, and the course of action selected should be designed to minimize error.

The anatomical development of the child in general, and the lungs in particular, along with associated changes in the maturing physiology, must be taken into consideration in pediatric airway management. Another factor frequently underemphasized is that, excluding congenital anomalies, children are remarkably consistent from one to another.

In pediatric patients from one to two years of age, the principal difference between the adult and pediatric airway is size. (5) For patients younger than one, the relative proportions of some structures vary from the adult proportions. In fact, most descriptions of the "pediatric" airway in the purest sense focus on this latter age group.

The age group from two to eight years represents a transition to the adult airway and, in fact, more closely resembles the adult airway than the infant's. Besides size, the most obvious difference between the adult and pediatric airway is its position in the neck. The pediatric airway is described as "anterior," when in reality it's more superior, the glottic opening lying higher, at approximately the level of C-2 or C-3, as opposed to C-6 in the adult. This position places the glottic opening at the base of the proportionally larger and predominantly intra-oral tongue. Because the airway may become "hidden" up high behind the tongue on laryngoscopy, this position is often referred to as "anterior."

All airways are anterior in the sense that they're palpable externally, but the pediatric airway is also more superior. The relatively larger intra-oral tongue exacerbates this position.

The epiglottis is also proportionally larger in the child than the adult. The ligamentous connection between the base of the tongue and the epiglottis isn't as strong as it is in the adult, making elevation of the proportionally larger epiglottis by manipulation of the vallecular space with a curved blade more difficult. For this reason, and because the large tongue is more difficult to remove from the field of vision with the curved blade, a straight blade is preferred for the first year or two of life when these changes are most pronounced. A straight blade can be inserted past the epiglottis to lift it up out of the field of vision.

The narrowest portion of the child's airway is at the level of the cricoid ring, as compared with the adult, in which the narrowest portion is at the level of the vocal cords. The significance of this anatomical variation is that, in the adult patient, endotracheal tube size is less critical, because a low-pressure cuff can be inflated to ensure adequate fit.

In the child, the size is more critical because an uncuffed tube is used and therefore the largest possible tube is inserted to ensure the largest internal diameter possible. A smaller tube reduces ventilatory ability, and a tube that is too large can cause pressure ischemia and necrosis of the tracheal mucosa with resultant subglottic stenosis. At approximately eight years of age, this variation normalizes and cuffed tubes are appropriate.

Two anatomic variations preclude blind naso-tracheal intubation in the child younger than eight to 10 years of age. The first is the presence of adenoidal tissue, which is frequently hypertrophied. This tissue can easily be injured, resulting in copious bleeding. Second, the angle of approach that a nasally introduced endotracheal tube must take to find its way into the glottis is much more acute in a child than an adult, so the success rate of the procedure is unsatisfactory.

The optimal position for alignment of the tracheal, pharyngeal and oral axis for bag-valve mask ventilation (BVM) or intubation is the sniffing position. In the adult, optimal axis alignment is accomplished by flexion of the neck on the chest (usually accomplished by placing a towel or other support beneath the occiput) and hyperextension of the head at the atlanto-occipital joint.

In most children, it's unnecessary to provide support to flex the neck because of their proportionally large occiput. Slight extension of the head at the atlanto-occipital joint (not hyperextension, which can actually cause obstruction) is all that's necessary.

To achieve the sniffing position in small infants, it's sometimes necessary to balance the disproportionate occipital size by placing a support under the shoulders. The older child and adolescent are positioned similar to the adult.

In all ages, once positioned, if an imaginary horizontal line can be drawn traversing the external auditory canal and passing anterior to the shoulders, correct positioning has been obtained (see Figure 1).

Proper BVM technique is particularly important in pediatric patients, whose crisis is often driven by a primary respiratory problem. They are more frequently hypoxemic than their adult counterparts and are subject to more rapid oxyhemoglobin desaturation, so BVM (Sellick's is maintained during BVM to prevent one from inflating the stomach and enhancing the risk of regurgitation and aspiration) is frequently required during the pre-oxygenation and paralysis phases of rapid sequence intubation (RSI) to achieve and maintain adequate O2 saturation.

As in adults, oral and nasopharyngeal airways are important adjuncts to BVM.

Because of the miniscule size of the cricothyroid membrane in the child, surgical cricothyrotomy is contraindicated. Needle cricothyrotomy is the procedure of choice for small children.

A combination of physiological factors decrease the ability to pre-oxygenate the pediatric patient as efficiently as the adult patient. The first and most important isthat the pediatric patient metabolizes oxygen twice as quickly as the adult (6 mL/kg versus 3 mL/kg).

Because of the lack of elastic lung recoil of the pediatric patient_s chest, the child also possesses a proportionally smaller FRC -- the lung volume measured when all forces in the chest are in equilibrium. This latter effect is especially exacerbated in the supine position.

Under similar pre-oxygenating conditions, the child sustains a significantly shorter period of oxygen saturation above 90% than the adult. The clinical implication is that a child may desaturate during the RSI procedure, and the provider must anticipate this and be prepared to initiate BVM ventilation with cricoid pressure.

Pediatric ventilation requires smaller tidal volumes, higher rates and size-specific equipment. The pediatric airway is particularly amenable to positive pressure ventilation, even in the presence of upper airway obstruction.

In pediatric airway management, identification and use of size-appropriate equipment is crucial. For this reason, standardized age and size-appropriate systems, such as the Broselow-Luten Color Coded systems (shown on the cover photo), are recommended.

Advanced airway management

Because inadequate oxygenation and ventilation have been identified as primary contributors to preventable mortality, it would seem intuitive that successful endotracheal intubation (ETI) would mitigate these deaths. Thus, ETI has become the gold standard in prehospital airway management.

However, considerable controversy exists as to whether pediatric patients requiring ETI should have it performed in the field or deferred until hospital arrival. Studies have shown higher rates of complication and failure in children than in adults, and one prospective, pseudo-randomized trial showed no demonstrable advantage in survival outcome following ETI compared with a group managed via BVM. (6-10)

Despite controversy, the indications for ETI of adults and children in an emergency remain: failure to maintain adequate oxygenation, failure to maintain adequate ventilation (CO2 removal), failure to protect the airway, the need for neuromuscular blockade or the anticipated clinical course. (5) So even though there may not be a compelling reason to intubate the trachea at a given point in your care of a patient, prehospital providers must continually evaluate the risk of an insidiously progressive condition advancing to the point when intubation would become more hazardous or physically impossible.

The best example in prehospital care relates to the transport environment, such as in the opening case. GroundEMS providers should consider whether future patient positioning in a helicopter will severely limit access to the head and neck, and thus the airway.

Once the decision to intubate is made, you must decide how to proceed. First responders and basic rescuers are typically limited to basic upper-airway adjuncts and BVM ventilation. Intermediate rescuers may employ supraglottic devices, such as the Laryngeal Mask Airway (LMA), the Combitube and the King LT Airway, to facilitate bag ventilation and provide some element of airway protection. For these personnel, the decision is typically a simple one: Will the victim tolerate insertion of the device?

ALS providers capable of endotracheal intubation who do not use neuromuscular blocking agents have limited options available to them beyond BVM ventilation and direct laryngoscopy intubation.

Once the child is intubated, the endotracheal tube (ETT) must be secured at the mouth, and since head and neck movement translates into ETT movement, a cervical collar or other device should be employed.

In infants, small movements are capable of dislocating the ETT into the esophagus, emphasizing the importance of head and neck immobilization. Securing the ETT at the mouth is traditionally done by taping the tube to the cheek or by using commercial devices.

Drug dosage& selection

A significant problem in the management of pediatric emergencies is the timely and accurate delivery of medications. The use of color-coded resuscitation aids for drug dosing and estimating ETT size in children precludes many of these problems, including having to estimate weight and remember and calculate drug doses.

One particular drug worthy of special mention when used with children is succinylcholine. Because the drug is rapidly distributed into extracellular water, and children have a relatively larger volume of extracellular fluid than adults, the recommended dose of succinylcholine is higher in children. (5)

In 1993, the FDA, in conjunction with pharmaceutical companies, revised the package labeling of succinylcholine after reports arose of hyperkalemic cardiac arrests due to the drug's administration to patients with previously undiagnosed neuromuscular disease. However, the initial advisory warnings continue to recommend succinylcholine for emergency or full-stomach intubation in children.

Case wrap-up

Because the 12-year-old patient's respiratory status was kept stable, the patient's airway did not require further field management.

On arrival at the emergency department (ED), the patient was unable to swallow secretions, had a muffled voice, was complaining of occasional air hunger and refused to lie flat. The attending emergency physician (a family practitioner) was unwilling to intubate the patient without anesthesia or surgery back-up available at the hospital. The weather had cleared, so air evacuation was requested.

When the air medical transport team arrived 20 minutes later, the patient's condition was unchanged. The flight crew elected to progressively sedate the young patient and proceeded with a sedation-assisted direct-vision intubation prior to transport. He was sedated and paralyzed for the duration of the transport and arrived at the Level 1 trauma center in stable condition. He was weaned and extubated on the sixth hospital day, and the remainder of his recovery was uneventful.

Summary

Respiratory assessment and airway management in the pediatric patient present many challenges, including differences in equipment sizes and drug dosing, anatomical variation that continuously evolves as development proceeds from infancy to adolescence, and the stress of resuscitating a critically ill child.

During the emotional mix of a pediatric resuscitation, it's easy to get sidetracked by co-existing confounding issues. Therefore, the importance of methodically working your way through airway evaluation and management cannot be overstressed. Assessment is the key to gathering critical evidence of a pediatric patient's respiratory status or warning of impending respiratory arrest.

Michael F. Murphy, MD, FRCPC (EM), FRCPC (ANES), is certified as a specialist by the Royal College of Physicians and Surgeons of Canada in both emergency medicine and anesthesiology. He's the professor and chair of anesthesia and professor of emergency medicine at Dalhousie University, and the clinical chief of anesthesia at the Capital District Health Authority in Halifax, Nova Scotia. He's also a founding faculty member of "The Difficult Airway Course: Emergency" and "The Difficult Airway Course: EMS." Contact him atmurphymf1@gmail.com.

Michael Keller, BS, NREMT-P, is a curriculum faculty member with Gaston College, Department for EMS Education in Dallas, N.C., a member of Lincoln County (N.C.) EMS and a national faculty member for "The Difficult Airway Course: EMS."

Robert Luten, MD, is professor of pediatrics and emergency medicine at the University of Florida, Shands Jacksonville, and former president of the Society for Pediatric Emergency Medicine. He's the author and principal instructor of the pediatric section of the National Emergency Airway Management course.

Colby J. Rowe, EMT-P, FP-C, CIC, is a paramedic supervisor, flight paramedic, and the continuing education and training coordinator at Stony Brook University Medical Center EMS on Long Island, N.Y. He's also a national faculty member of "The Difficult Airway Course: EMS" and an adjunct faculty in the Emergency and Disaster Management concentration at Stony Brook University.

Mary Beth Skarote, NREMT-P, is an emergency response and recovery coordinator for Wake Forest University Baptist Medical Center, Winston-Salem, N.C.; a paramedic with Davidson County (N.C.) EMS; president for North Carolina Association of Paramedics; and one of the original faculty for "The Difficult Airway Course: EMS."

References

1.AmericanAcademy of Pediatrics: Pediatric Education for Prehospital Professionals. Jones & Bartlett:Boston,Mass., 2000. pp. 2Ï35.

2. Caroline N: Emergency Care in the Streets. Jones & Bartlett:Boston,Mass., 2008. p. 41.

3. Institute for Continuing Education. www. ceu.org/cecourses/981117/ch11b.htm

4. Bledsoe B, Porter R, Cherry R: Paramedic Care: Principles & Practice. Pearson Prentice Hall:Upper Saddle River,N.J., 2006. p. 59.

5. Walls RM, Murphy MF, Luten RC (eds): Manual of Emergency Airway Management. Harvard Medical School: Boston,Mass., 2004. pp. 212Ï281.

6. Aijian P, Tsai A, Knopp R, et al: "Endotracheal intubation of pediatric patients by paramedics." Annals of Emergency Medicine. 18(5):489Ï494, 1989.

7. Vilke GM, Steen PJ, Smith AM, et al: "Out-of-hospital pediatric intubation by paramedics: The San Diego experience." Journal of Emergency Medicine. 22(1):71Ï74, 2002.

8. Brownstein D, Shugerman R, Cummings P, et al: "Prehospital endotracheal intubation of children by paramedics." Annals of Emergency Medicine. 28(1):34Ï39, 1996.

9. Gausche M, Lewis RJ, Stratton SJ, et al: "Effect of out-of-hospital pediatric endotracheal intubation on survival and neurological outcome: A controlled clinical trial." JAMA. 283(6):783Ï790, 2000.




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Related Topics: Patient Care, Airway and Respiratory, Medical Emergencies, Patient Management, Jems Features

 

Michael F. Murphy, MD, FRCPC

Michael F. Murphy, MD, FRCPC, is professor and chair of the Department of Anesthesia, Dalhousie University. He is a professor of Emergency Medicine at Dalhousie University, the district chief of anesthesiology for the Capital District Health Authority, and an attending physician in Emergency Medicine at Queen Elizabeth II Health Sciences Centre in Nova Scotia. He's also a founding faculty member of The Difficult Airway Course: EMS. Contact him at murphymf1@gmail.com.

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