Authors: Aaron Donoghue, MD, Research Fellow, Divisions of Critical Care and Emergency Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA; Jill Baren, MD, Attending Physician, Division of Emergency Medicine, Children’s Hospital of Philadelphia, and Department of Emergency Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA.
Peer Reviewer: Steven M. Winograd, MD, FACEP, Attending Physician, Emergency Department, St. Joseph Medical Center, Reading, PA.
The most important skill for the emergency physician is airway management. The Manual of Emergency Airway Management by Ron Walls, MD, emphasizes that control of the airway is a defining skill of emergency medicine.1 No other commonly performed procedure has as immediate an effect on life and death as endotracheal intubation. Although challenging in all patients, the procedures of endotracheal intubation (ETI) and rapid sequence induction pose many particular challenges when performed in children. This article will begin by reviewing the existing literature describing the epidemiology of rapid sequence intubation (RSI) in children as well as its affect on survival. The pertinent aspects of pediatric anatomy and physiology will be reviewed. Finally, the various components of RSI in children— including equipment, techniques, medications, and rescue devices— will be discussed. —The Editor
Introduction and Epidemiology
The establishment and maintenance of a patent airway has been the initial step in resuscitation of both children and adults for as long as resuscitation guidelines have existed. ETI is considered by many the gold standard among interventions for the pediatric airway.
However, clinical evidence of the usefulness and efficacy of ETI in children is not supported completely by studies examining the technique and its outcomes.
This article will provide an overview of the anatomic, physiologic, pharmacologic, and procedural aspects of advanced pediatric airway management using ETI, RSI, and rescue techniques.
Pediatric ETI in the Prehospital Setting
Although many of the principles of pediatric ETI apply in all health care settings, ETI in the prehospital care setting has unique characteristics and has been the subject of intense controversy. In a landmark study by Gausche et al, prehospital care providers administered either ETI or bag valve mask (BVM) ventilation to children in need of respiratory support in an alternate day fashion. A total of 820 children were enrolled during a 33-month period. No difference was found in either survival or favorable neurologic outcome in children who underwent ETI compared with those who received BVM ventilation alone. The authors concluded that ETI conferred no benefit to critically ill children in the prehospital setting and resulted in significantly longer scene times.2 All children enrolled had short transport times to definitive medical care (mean 20 and 23 minutes for BVM vs ETI groups, respectively). Intubation success rates varied by age (56-67%) and were considerably lower than those observed in other studies.
Despite the limitations cited above, the Gausche study clearly affected the approach to pediatric prehospital airway management. The most recently published guidelines for Pediatric Advance Life Saving (PALS) included a change in wording regarding ETI use in children, stating that "ventilation via a properly placed tracheal tube is the most effective and reliable method of assisted ventilation," but that ETI "requires mastery of the technical skill to successfully and safely place a tube in the trachea, and it may not always be appropriate in the out-of-hospital setting . . ."3
Gausche’s findings contrasted with those of previous epidemiologic studies that evaluated prehospital ETI in the pediatric patient in cardiopulmonary arrest. In 1987, Losek and colleagues analyzed 114 children with out-of-hospital cardiac arrest, and found that in children younger than 18 months, successful ETI was a significant predictor of survival to hospital discharge.4 Ironically, the study also demonstrated a statistically significant decreased likelihood for ETI being attempted in children in the same age range. In 1999, Sirbaugh and colleagues conducted a prospective analysis of 300 children with out-of-hospital cardiac arrest and found that successful ETI was the only significant predictor for on-scene return of spontaneous circulation; however, ETI had no affect on survival.5
Use of RSI Medications in Children
The variability of successful outcomes from pediatric ETI use in the prehospital arena, as well as in the emergency department (ED), is due largely to the variability in success rates for tube placement and the occurrence of complications. Little data examining the effect of RSI medications on intubation success in the ED exist. A recently published prospective survey of 11 EDs that performed 156 pediatric intubations during a 16-month period showed that 72% percent of first attempts at ETI were successful overall, varying from 60% in children younger than 2 years to 85% for children ages 12 to 18 years.5 Intubation was more likely to be successful in children in whom RSI was performed (defined as the use of neuromuscular blockade [NMB] prior to intubation) when compared with ETI attempted with no medications or the use of sedative medications alone. In another recent retrospective review of ED patients, RSI was successful in 78% of cases with the first attempt when medications for RSI were applied according to a pre-established protocol.6 Easley and colleagues prospectively examined children who underwent ETI and found significant differences in medication use between children’s hospital EDs and non-children’s hospital EDs. They found that pediatric patients in non-children’s hospital EDs were more likely to be intubated without NMB agents or with no medications and also were more likely to experience complications or variances from practice guidelines.7 This study, however, did not examine or control clinical variables related to patients studied.
Studies of prehospital ETI in children without the use of RSI or sedation medications also have yielded variable intubation success rates, ranging from 39-50% in infants to 71-90% in older children. Several studies have demonstrated significant differences in success of ETI among age groups, with infants and toddlers having lower success rates than older children.4,8,9 Results of one retrospective study of prehospital ETI in children showed that succinylcholine (SCh) was used by paramedics in 47% of cases, and that patients receiving SCh were more likely to be older, more likely to have been injured, and less likely to experience complications related to ETI.10 This variability in ETI success rates in the literature reflects the complexity of performing ETI on a heterogeneous group of patients in a variable and often uncontrolled setting.
The ability to perform ETI successfully in a pediatric patient begins with knowledge of the unique anatomic features in the head and neck, and a thorough familiarity with a child’s airway structures. Differences in technique, positioning, and equipment configuration and size all must be adapted to the unique anatomical considerations listed below.
Size. Airway structures are smaller and the field of vision with laryngoscopy is narrower in children.
Adenoidal Hypertrophy. This condition is common in young children leading to greater tendency to obstruct the nasopharynx; and greater risk for injury to adenoidal tissue with resultant bleeding in hypopharynx when laryngoscopy is performed.
Developing Teeth. Although young infants are edentulous, the underlying alveolar ridge contains developing tooth buds that are susceptible to disruption from laryngoscope trauma. Primary teeth in young children can be avulsed and/or aspirated easily.
Tongue. The tongue is large relative to the size of oropharynx in children.
Superior Larynx. Often referred to as being anterior, the laryngeal opening in infants and young children actually is located in a superior position to that of an adult. (In infants, the larynx is opposite C3-C4 as opposed to C4-C5 in adults.) A child’s normal anatomy makes the angle of the laryngeal opening with respect to the base of the tongue more acute and visualization more difficult.
Hyoepiglottic Ligament. The hyoepiglottic ligament connects the base of tongue to the epiglottis. This ligament has less strength in young children; therefore, a laryngoscope blade in the vallecula will not elevate the epiglottis as efficiently as in an adult.
Epiglottis. The epiglottis of children is narrow and angled acutely with respect to the tracheal axis; thus, the epiglottis covers the tracheal opening to a greater extent and can be more difficult to mobilize.
The narrowest point of the young child’s airway occurs at the level of the cricoid cartilage instead of at the level of the glottic opening itself.
The goal of head positioning for direct laryngoscopy is the alignment of the pharyngeal axis (PA), laryngeal axis (LA), and oral axis (OA). In adults, the alignment of the LA and PA often is optimized by the elevation of the occiput. In infants, the prominent occiput makes that maneuver unnecessary, and occipital elevation can potentially worsen the view of the glottic opening.11
An understanding of the unique physiologic features of children also is extremely important as a background for discussion of RSI in children.
Lung. Infants have fewer and smaller alveoli than young children, and their overall gas exchange surface area is disproportionately small. Surface area reaches proportions similar to adulthood by 8 years of age. Channels for collateral ventilation (pores of Kuhn and Lambert’s channels) are absent in infancy. The overall effect of those phenomena is a greater tendency for alveolar hypoventilation and for the development of atelectasis during a respiratory illness.12
Respiratory Mechanics. The pediatric thoracic skeleton is largely cartilaginous and much more compliant than the adult skeleton. Elastic recoil of the chest wall in the young child is essentially absent. A given change in thoracic pressure will result in a larger change in lung volume, similar to the physiology seen in an adult with emphysema. A given change in volume is associated with little or no change in pressure, so that a greater amount of work is required to generate a tidal breath.
The high compliance of the pediatric chest wall results in a closing volume (CV) (i.e., volume at which terminal bronchioles collapse because they are no longer supported by elastic recoil) that can be elevated with respect to functional residual capacity (FRC). If the already diminished elastic recoil is impaired (i.e., by supine positioning), CV can exceed FRC to a greater extent resulting in the absence of ventilation of some lung segments during normal tidal breathing. Therefore, young patients have a greater tendency for intrapulmonary shunting and hypoxemia with the positioning required for airway management.
Accessory respiratory muscles in young children are composed of a lower percentage of slow-twitch muscle fibers and are more susceptible to fatigue compared with the diaphragm. Also, the architecture of the pediatric thorax (horizontal rib orientation with extensive cartilage composition) is such that intercostal and suprasternal muscles are recruited poorly to assist in respiratory effort.11
Airway. Airway diameter and length increase with age. The distal airway (bronchioles) lags in growth behind the proximal airway during the first few years of life. Pouseille’s law states that airway resistance is inversely proportional to the 4th power of the radius of the airway. Thus, young children have higher resistance to airflow at baseline in their lower airways, and a change in airway diameter of a given dimension will have a much more profound effect on airway resistance in a small child than in an older child or adult. Such a change can occur as a result of edema, obstruction, or excess secretions. Illnesses that affect the caliber of small airways (e.g., asthma and viral bronchiolitis) produce a disproportionate increase in work of breathing in infants and children.12
Cellular Oxygenation. Resting oxygen consumption in the newborn is twice that of an adult (6 mL/kg/min vs 3 mL/kg/ min). Oxygen consumption in infants is extremely sensitive to physiologic derangements, such as fever or hypothermia. At a neutral temperature (35°C), oxygen consumption is at a minimal level; either increasing or decreasing temperature results in dramatic increases in oxygen consumption. The oxyhemoglobin dissociation curve for young infants is shifted to the left (greater affinity for oxygen and poorer tissue oxygen delivery) by the presence of elevated amounts of fetal hemoglobin.12
The summary effects of the various respiratory physiologic phenomena described above are a greater tendency for hypoxemia and arterial desaturation. Benumof and colleagues constructed a theoretical model of oxyhemoglobin desaturation to demonstrate the time to critical desaturation of several classes of patients, including children.13 According to this model, a healthy 10-kg child will desaturate to 90% after approximately three minutes of apnea, much more quickly than healthy or even moderately ill adults.14 In a clinical study of elective surgery patients, Xue and colleagues found that the mean time to desaturation to 90% was 118 seconds in infants, 168 seconds in toddlers, and 248 seconds in children older than 3 years.15 The time required for the saturation to fall from 95% to 90% was significantly shorter in infants than older children as well (8 seconds compared with 16 seconds).15 Those findings occurred following a two-minute period of ventilation with 100% oxygen prior to neuromuscular blockade, a preoxygenation time in a separate clinical study determined to be optimal for minimizing risk of early desaturation.16 A search of the existing literature yielded no clinical data examining how quickly deoxygenation occurs in ill children, but it is logical to assume that it is more rapid than the range of two to three minutes described by those studies under ideal conditions.
Children have increased vagal tone when compared with that of older patients. In young children, laryngoscopy has a much greater tendency to produce vagally mediated bradycardia. Because children have a limited ability to vary stroke volume to maintain cardiac output, tachycardia is often the sole compensatory mechanism in low cardiac output states; therefore, vagally mediated bradycardia can have a significantly deleterious effect on cardiac output.11
Neonates in particular have significantly fragile cardiopulmonary adaptive mechanisms. Hypoxia is tolerated very poorly, and the response to desaturation often is paradoxical bradycardia. Additionally, neonatal respiratory control is immature and discoordinated, with newborns typically exhibiting periodic breathing (i.e., absence of respiratory effort for up to 15 seconds) for up to several weeks of life. Minute ventilation does not increase to a great enough extent in response to hypercarbia, so hypoxemia results in transient hyperventilation and actually progresses to respiratory depression as oxygen tension falls.
A wide range of equipment is available for ETI in adults and children, and there is considerable variability in the preferences of individual practitioners. This section will describe the range of equipment available and give general guidelines for equipment selection according to patient age. It is important to realize that the guidelines discussed below are imperfect. A range of sizes and types of laryngoscope blades, endotracheal tubes, and airway adjuncts should be available for use in each case of pediatric intubation so when an individual child deviates from standard guidelines, rapid adjustments can be made.
Laryngoscope. The two predominant types of laryngoscope blades used in pediatric airway management are the straight and the curved blades. Both types can be used successfully in children and adults depending upon operator experience. Most pediatric practitioners favor the use of straight blades when intubating young children because of the anatomical considerations discussed previously.
When properly applied, the tip of a straight laryngoscope blade rests underneath the tip of the epiglottis, and when upward force is applied, the blade physically lifts the epiglottis out of the way to expose the glottic opening.17 In contrast, the proper positioning of a curved blade is such that the tip lies in the vallecula, behind the epiglottis, and upward traction pulls the epiglottis up and exposes the glottic opening.17 The less acute angle of the epiglottis with respect to the anterior hypopharyngeal wall, creates a visual axis for the intubator that is obstructed to a greater degree by the epiglottis. A direct line of sight often is easier to achieve by lifting the epiglottis itself rather than by indirect force applied to the vallecula. This is why a straight blade often is preferred for ETI in young children. Additionally, the weak tensile strength of the hyoepiglottic ligament lessens the degree of traction on the epiglottis created by this force, and a curved blade may not afford the same degree of elevation of the epiglottis in a young child. Guidelines for the selection of sizes of blades according to patient age are listed in Table 1.
Guidelines for Laryngoscope Blade Selection
Endotracheal Tubes (ETTs). Like all other structures in the developing child, the caliber and conformation of the airway grows and develops with age. Endotracheal tubes (ETTs) exist in a wide range of sizes to accommodate the full spectrum of the pediatric age group from birth through adulthood.
The two most commonly applied rules for sizing of ETTs are the age-based rule and selection based upon body length (the Broselow-Luten tape). The age-based rule is:
[Age in years / 4] + 4 = ETT size.
King and colleagues found age-based rules predicted ETT size correctly within a range of 1 mm in 97.5% of patients.18 The Broselow-Luten tape selects the size of ETT based upon the length of the patient. The initial study of the validity of the Broselow-Luten tape found it to be more accurate than age-based selection criteria.19 A more recent study by Hofer and colleagues also found that the Broselow tape was more accurate (correct in 55% of patients) than the age-based rule (correct in 41%), but also found that the Broselow tape was prone to underestimating ETT size (in 39% of patients), whereas the age-based rule tended to overestimate (in 57% of patients).20 Another recent study found that there was no difference between the accuracy rates of the two methods, and that Broselow tape measurement and the age-based rule predicted the same size of ETT in 66% of patients.21
Another commonly quoted method for rapid estimation of ET size applied to children is that the diameter of a child’s airway is approximately the same diameter as his fifth digit. Two operating room-based studies have suggested that the rule is inaccurate; one study found that the width of the nail of the fifth digit was a more accurate predictor of ETT size than the diameter of the finger itself.18, 22
As mentioned above, the narrowest point in the airway of the young child occurs at the level of the cricoid cartilage, below the insertion of the vocal cords. In these patients, uncuffed endotracheal tubes are often the most appropriate tubes to achieve easy passage through the upper airway and the ability to ventilate effectively without excessive air leakage. At about 8 years of age, the conformation of the airway approximates that of an adult; older children most often require cuffed endotracheal tubes to achieve a good fit in the trachea. Deakers and colleagues studied 282 consecutive patients in a pediatric intensive care unit (PICU) setting comparing children with uncuffed and cuffed ETTs and found that there was no significant difference in the occurrence of post-extubation stridor or any significant long-term sequelae from airway problems.23 In a randomized study, Khine and colleagues found no significant difference in the incidence of post-extubation croup in children intubated with cuffed ETTs compared with those intubated with uncuffed ETTs.24 In children younger than 8 to 10 years of age, an uncuffed ET should be used, but current PALS recommendations state that "cuffed endotracheal tubes . . . may be appropriate under circumstances in which high inspiratory pressure is expected."25
Adjunctive Devices and Techniques
Oropharyngeal and Nasopharyngeal Airways. The use of oropharyngeal (OP) and nasopharyngeal (NP) airways in children can be a useful intermediate step in maintaining airway patency. The generous size of the child’s tongue and adenotonsillar tissue predisposes to upper airway obstruction, either from a diseased airway or during RSI when there is loss of airway and glottic tone. Both devices exist in a range of sizes suitable for all pediatric ages. The correct size of an OP airway for a patient can be estimated by the distance from the patient’s central incisors to the angle of the mandible; for NP airways, the correct size is estimated by the distance from the nare to the earlobe. OP airways, when properly positioned, tend to rest against the base of the tongue and can induce gagging and vomiting, so they should be used only in the unconscious patient.17
Cricoid Pressure. The technique of cricoid pressure initially was described by Sellick in 1961 as a technique to prevent aspiration of regurgitated gastric contents during anesthesia induction.26 It also prevents insufflation of air into the stomach with positive-pressure ventilation. The technique is performed by applying gentle pressure on the cricoid ring, displacing it backward to occlude the posterior esophagus. This technique has become common practice for airway management in children and adults. Caution should be maintained as several studies have shown that cricoid pressure commonly is done incorrectly or ineffectively and can cause undesired effects or complications. Those performing the maneuver should be trained to do so.
Current literature has not examined the use of cricoid pressure for RSI in the ill child specifically. The theoretical rationale for its use is very strong. As previously mentioned, desaturation with induction is common in ill children. The establishment of a safe oxygen reservoir followed by the use of medications to achieve intubating conditions rapidly to prevent desaturation often does not occur in pediatric patients. Often it is very necessary to support ill children with positive pressure ventilation (PPV) during RSI, and the prevention of gastric insufflation with cricoid pressure can be of great importance.
Laryngeal Manipulation Maneuvers. The technique of backward-upward-rightward pressure of the larynx—commonly referred to as BURP—was described initially by Knill and has been advocated as a technique that optimizes the view of the glottic opening in cases of difficult laryngoscopy.27 An assistant applies direct pressure on the thyroid cartilage, displacing it dorsally, upward toward the head, and 0.5-2.0 cm to the patient’s right. Takahata and colleagues found that the BURP maneuver performed better than simple cricoid pressure in improving glottic visualization in unexpected difficult laryngoscopy cases.28 External laryngeal manipulation (ELM) is a technique described initially by Benumof and colleagues in which the intubator uses his/her right hand to maneuver the laryngeal structures while maintaining his/her own line of sight with the airway opening.29 When an optimal position is found, the intubator signals an assistant to maintain that position of the larynx while the patient is intubated. This technique has been validated by Levitan and colleagues using videographic imaging in adults intubated by emergency medicine interns.30
Neither of these techniques has been studied in children but could be logically extrapolated to the pediatric patient if gentle external force is used; the amount of pressure needed to occlude or distort the pediatric airway is much less than that required in an adult.
The general sequence for medication administration to facilitate RSI in children consists of three types of drugs given in rapid succession:
• Sedatives; and
• Neuromuscular blocking agents.
Multiple agents exist for use in RSI, and the benefits and risks of each are discussed below. Preferences vary among practitioners. Current PALS guidelines do not support the use of any uniform approach to drug selection.3 Familiarity with multiple drugs for pediatric RSI is important for anyone who frequently manages ill children.
Vagolytics. Atropine. The rationale for the use of atropine as a premedication for pediatric RSI is to alleviate the risk of vagal-mediated bradycardia that may occur during laryngoscopy. A dose of 0.02 mg/kg (minimum dose 0.1 mg, maximum 1 mg) is given as an initial bolus prior to sedation or paralysis. Doses of less than 0.1 mg have been associated with paradoxical bradycardia.
Results from numerous studies in the anesthesia literature have suggested that atropine premedication before laryngoscopy in healthy children undergoing surgery is not necessary due to an exceedingly low incidence of bradycardia in those patients.31,32 Comparable data are lacking regarding the emergently ill child. One study of critically ill children who underwent protocol-based RSI by flight paramedics found an association between the omission of atropine and the occurrence of bradycardia during RSI, although this phenomenon was observed only in two patients.33 Although high quality data to support the routine use of atropine in all RSI events are lacking, many emergency medicine practitioners use it in children younger than 8-10 years.34
Sedatives. Barbiturates (Thiopental). Thiopental is the most commonly used barbiturate for RSI. It has a rapid onset (peak effect at 10-20 seconds) and brief duration of action (5-30 minutes). Thiopental decreases cerebral metabolic activity and thus, lowers cerebral blood flow, making it advantageous for use in the patient with increased intracranial pressure (ICP). It also has inherent anticonvulsant effects and may be beneficial when used in a child with seizures who requires ETI. Recommended dosing ranges from 2 to 8 mg/kg intravenously. Like all barbiturates, thiopental is a peripheral vasodilator and a myocardial depressant. It can lower blood pressure and impair cardiac contractility and should not be used in the hypoperfused or hypotensive child.35
Benzodiazepines (Midazolam). Midazolam has sedative, amnestic, anticonvulsant, and anxiolytic properties. Its time of onset following intravenous administration ranges from 60-90 seconds, and its duration of activity is similar to thiopental (5-30 minutes). Midazolam can be given by multiple routes. Recommended dosing is 0.1-0.3 mg/kg intravenously.
The hemodynamic side effect profile of midazolam is similar to, but much milder than, that of the barbiturates. Midazolam can lower systemic vascular resistance and blood pressure, and can be disadvantageous in the hypovolemic patient, although these effects are observed less commonly than with thiopental. Paradoxical agitation can occur in children following midazolam administration in rare instances.35
One study of midazolam dosing for RSI found that 56% of children were given induction doses less than the commonly recommended dose of 0.1 mg/kg. The mean dose of midazolam given to all children was 0.08 mg/kg (+/- 0.04 mg/kg).36
Opioids (Fentanyl). Fentanyl is a fast-acting narcotic (peak effect 1-2 minutes, duration 30-40 minutes), which produces analgesia, sedation, and euphoria. It does not result in systemic histamine release as other opioids do, and as a result is less likely to produce hypotension. Recommended dose range is 1-3 mcg/kg intravenously.
Fentanyl does have sympatholytic effects and can cause a transient decrease in heart rate.35 The effect of fentanyl on ICP is not well known in children. There is evidence that fentanyl blunts the hemodynamic response to laryngoscopy, which is desirable in patients with known or suspected increased ICP.37,38 Conversely, there is one known case report that describes an increase in ICP in a head-injured child following the administration of fentanyl.39 Chest wall rigidity is a rare side effect of fentanyl that has been observed in multiple case reports40-44; prevention of this effect is best accomplished by either slow administration or simultaneous use of a neuromuscular blockade.
Ketamine. Ketamine is a rapidly acting agent (onset within a few seconds, duration 10-20 minutes) that produces analgesia, dissociative anesthesia, and amnesia. The dissociative state of sedation produced by ketamine is unique among the agents discussed here; patients can continue to have their eyes open and even to speak. Additionally, ketamine is unique among induction agents in that airway reflexes and respiratory drive are well preserved. A recent pilot study of children receiving ketamine for procedural sedation found no detectable hypoxemia or hypercapnea in any patient, suggesting that significant subclinical respiratory depression does not occur.45 Ketamine also has inherent bronchodilator properties and is recommended as a component of RSI of patients in status asthmaticus.46 Recommended doses range from 1-3 mg/kg intravenously. Ketamine also can be given intramuscularly at increased doses (3-5 mg/kg).
Hemodynamically, ketamine increases heart rate, mean arterial pressure, and cardiac output. The mechanisms for those changes are not well understood. Ketamine has been recommended as an induction agent for patients with hypovolemia, septic shock, or cardiac tamponade, even though there may be a theoretical risk of the myocardial depression when catecho-lamine stores are depleted.46 One recent case series evaluated PICU patients receiving ketamine for procedural sedation; 88% of the patients in the survey were American Society of Anesthesia-class 3 or greater for their present illness (severe systemic disease), and no adverse outcomes attributable to ketamine were reported.47 No specific data on hemodynamic parameters were included in the study.
Ketamine increases ICP, intraocular pressure, and intragastric pressure. It is not recommended for use in the head-injured patient or the patient at risk for elevated ICP. Emergence reactions characterized by delirium or agitation have been associated with ketamine; evidence that the concurrent use of benzodiazepines reduces this side effect is mixed.46,48 Ketamine stimulates salivary and tracheobronchial secretions, so the concurrent use of atropine is recommended in older patients for whom atropine premedication for RSI would not be indicated otherwise. Laryngospasm is an uncommon side effect that has been linked to ketamine use secondary to sensitized laryngeal reflexes. In a systematic review of ketamine use in children, Green et al reported an overall incidence of two cases of laryngospasm in 11,589 patients (0.017%).49,50 In the context of RSI, this is only significant in rare cases where simultaneous neuromuscular blockade is not being used.
Etomidate. Etomidate is a rapidly acting sedative that reaches peak effect within a few seconds of IV administration. It is a pure hypnotic sedative, with no inherent analgesic properties. The side effect profile is very favorable, with minimal hemodynamic effects demonstrated in laboratory and clinical studies. The hemodynamic stability associated with etomidate has made it a favored agent for use in adults with pre-existing cardiac disease. Etomidate also lowers cerebral blood flow and ICP without changing mean arterial pressure, making it an advantageous agent in the patient with increased ICP or a head injury.46 Recommended dosing is 0.3 mg/kg intravenously.
Etomidate has been associated with adrenocortical suppression when administered as a continuous infusion. One randomized trial in adults found that adrenal suppression was detectable for 12 hours following a single dose of 0.3 mg/kg of etomidate for RSI, but cortisol levels remained normal in those patients, and no clinically significant effects were noted.51 Myoclonus is a common side effect that has been noted with etomidate use; this should not be a significant concern when accompanied by a neuromuscular blockade for RSI.46
Two case series have been published that specifically examine the use of etomidate for RSI in children.52,53 A total of 189 patients were retrospectively reviewed; no evidence of clinically significant adrenal suppression was noted, and only four patients had clinically significant hypotension. None were thought to be related to etomidate administration. At present, no prospective data exist for the use of etomidate in pediatric RSI.
Propofol. Propofol is an intravenous hypnotic agent that is used widely in anesthesia practice. It has a very rapid onset (within seconds) and a brief duration of activity (5-10 minutes) when given as a bolus of 1 to 2 mg/kg intravenously. It has significant myocardial depressant effects and lowers blood pressure and respiratory drive.46 Long-term use of propofol infusion in children has been associated with severe metabolic acidosis,54 although a recent cohort of PICU patients receiving propofol infusion for a median of 16.5 hours showed no incidence of acidosis.55 The combination of an unfavorable hemodynamic profile and high cost have made propofol an uncommon agent for use in RSI for children.
The choice of sedatives for RSI are plentiful and the most variable among all the medications used in RSI. The agent selected should depend upon the individual patient’s underlying pathophysiology after a careful analysis of the risks and potential complications of each agent. In a multihospital survey by Sagarin et al, etomidate was the most commonly used agent among children undergoing RSI (42%), followed by thiopental (22%), midazolam (18%), and ketamine (7%).56
Neuromuscular Blocking Agents (NMB)
Succinylcholine (SCh). Succinylcholine is the most widely used NMB for RSI in all categories of patient age and diagnosis. It has a rapid onset (20-60 seconds) and brief duration of action (5-10 minutes) when given in recommended doses of 1 to 2 mg/kg intravenously. It also has been used effectively when given by the intramuscular and intraosseous routes.
SCh has several important and well-described side effects. Bradycardia has been noted to occur with SCh, particularly when repeated doses are required for paralysis. This is due to the structural similarity between SCh and acetylcholine, and readily is prevented by premedication with atropine. Although there are no well-designed studies documenting the relationship between succinylcholine use and bradycardia, children appear to be prone to bradycardia. Therefore, many airway experts have recommended making atropine an essential step in RSI in children when using SCh.
The transient muscle fasciculations that precede paralysis with SCh administration can be of clinical significance in cases of increased ICP, eye injury, and increased intragastric pressure; these fasciculations can be minimized through premedication with a defasciculating dose of vecuronium (0.01 mg/kg). SCh can cause a transient increase in serum potassium levels, averaging 0.5 mEq/L. That increase can be exacerbated in certain patients, including those with crush injuries or patients with denervating disorders or congenital skeletal muscle myopathies; the use of SCh in those patients has been associated with life-threatening hyperkalemia and cardiac arrest.
In the late 1980s and early 1990s, a series of cases of unexpected hyperkalemic cardiac arrest was reported in apparently healthy children who had received SCh for airway management. A total of 36 reported cases were described, and all of those children were found on subsequent workup (or autopsy) to have previously undiagnosed myopathic disorders, Duchenne’s muscular dystrophy most common among them. Based upon those findings, the Food and Drug Administration’s Advisory Committee for Anesthetic and Life Support Drugs recommended a labeling revision for SCh at its meeting in 1992. The new label states that routine use of SCh in children should be avoided and alternative agents (nondepolarizing NMBs) used except in specific circumstances, including patients with laryngospasm or a full stomach, or when intramuscular use is needed secondary to IV access being difficult or absent.57
Succinylcholine, however, remains in widespread use in children for RSI despite the labeling change. A survey of anesthesiologists in the United Kingdom performed soon after the labeling change showed that 86% of anesthesiologists continued to use it routinely in their pediatric patients.58 In the previously cited multihospital survey by Sagarin and colleagues, SCh was the NMB used in 91% of patients who underwent RSI.56 The fact that the speed of onset of SCh is unparalleled by other agents is well-recognized, and when a given clinical situation is dominated by the need for very fast onset of intubating conditions, SCh remains the arguable drug of choice.
Vecuronium. Vecuronium is a nondepolarizing NMB of intermediate duration (30-60 minutes). At recommended doses of 0.1-0.2 mg/kg IV, its time of onset ranges from 90-120 seconds. Increasing the dose of vecuronium (doses of 0.3-0.4 mg/kg) can shorten the time of onset but results in prolonged periods of neuromuscular blockade. One anesthesia study found that younger children were more resistant to paralysis by vecuronium and required higher dosing.
Koller and colleagues compared 0.3 mg/kg of vecuronium with 1 mg/kg of SCh in healthy adults undergoing elective surgery and found no significant difference in intubating conditions at 60 seconds following NMB administration.59
Rocuronium. Rocuronium is a rapid-onset NMB with a shorter duration of action than other nondepolarizing agents. Results of studies of adults have demonstrated onset of paralysis at 60-90 seconds and a duration of action of 20-30 minutes following IV administration of recommended doses of 0.6 mg/kg.
Stoddart and colleagues compared 0.6 mg/kg of rocuronium and 1 mg/kg of SCh in healthy children undergoing elective surgery and found no significant difference in intubating conditions at 60 seconds following NMB administration; there were significant differences in the time of onset and duration of paralysis as measured by train-of-four monitoring.60 Cheng and colleagues performed a similar study of intubating conditions 60 seconds following NMB administration, comparing 1.5 mg/kg of SCh with rocuronium at doses of 0.6 mg/kg and 0.9 mg/kg; they found that the higher-dose of rocuronium was no different than SCh at those doses, but that 0.6 mg/kg of rocuronium resulted in less favorable intubating conditions compared with SCh.61
Other Nondepolarizing NMBs
Pancuronium. Pancuronium is among the oldest of the nondepolarizing NMBs. Its time of onset is 1.5-3 minutes following an IV dose of 0.1 mg/kg, and its duration of action is longer than vecuronium or rocuronium (40-60 minutes). Pancuronium has inherent anticholinergic effects and frequently results in increases in heart rate.
Mivacurium. Mivacurium is a short-acting NMB with a time of onset of 75-90 seconds and a brief duration of action (10-20 minutes). Studies comparing mivacurium and SCh in children have shown that paralysis occurs more slowly with mivacurium, but still in a time frame suitable for RSI.62 Rapid injection of mivacurium can result in histamine release, resulting in tachycardia and hypotension in some cases. Recommended dosing is 0.2-0.3 mg/kg.63
Atracurium and cis-Atracurium. Atracurium and cis-atracurium are moderately short-acting NMBs with times of onset of 90-120 seconds and duration of activity of 30-45 minutes. These agents are distinctive in that their elimination from the body occurs through non-specific ester hydrolysis and Hoffman degradation; thus, they are advantageous in the setting of pre-existing hepatic and/or renal disease (the other agents above are metabolized through either renal or hepatic elimination pathways). Recommended dosing is 0.6 mg/kg for atracurium and 0.1 mg/kg for cis-atracurium.63
Lidocaine. Lidocaine has been advocated as a useful adjunct to RSI in patients with increased ICP. Its theoretical benefit is a reduction of the sudden and potentially harmful increase in blood pressure and cerebral blood flow that results from laryngoscopy and tracheal suctioning.64,65 Data on its usefulness in this regard are mixed. A recent systematic review concluded that there is no evidence of improved neurologic outcome from premedication with intravenous lidocaine prior to RSI.66 An operating room-based study by Splinter found that intravenous lidocaine had no effect on the heart rate and blood pressure changes induced by laryngoscopy and ETI in children, and that these changes were more pronounced with increasing age.67 At recommended doses of 1 to 2 mg/kg, there is minimal risk of toxicity in the pediatric patient, and still it is used routinely by many practitioners.35 Recommended timing of the dose is 2 to 3 minutes prior to laryngoscopy.
Confirmation of Endotracheal Tube Placement
Confirming that an endotracheal tube has been placed in the trachea is necessary following every intubation. Several clinical signs, such as the presence of breath sounds, visible rise of the chest wall, absence of sounds over the epigastrium, and condensation within the tube lumen often are relied upon at the bedside. Current PALS recommendations, however, recognize that those signs can be unreliable, and have mandated that exhaled carbon dioxide detection be employed in all patients.25
End Tidal Carbon Dioxide (ETCO2). ETCO2 detection is the most common way to confirm proper endotracheal tube placement. Several types of ETCO2 detectors are available commercially. Most EDs will have disposable colorimetric devices, which register exhaled CO2 by a change in color of a piece of paper in a plastic chamber, but some use capnography, which digitally displays the exact partial pressure of exhaled CO2 with or without a waveform.
Results from several studies have supported the specificity and sensitivity of ETCO2 in infants and children. In the patient in full cardiopulmonary arrest, the absence of pulmonary blood flow may limit the amount of carbon dioxide in the alveoli, making ETCO2 prone to false- negative results. A study by Bhende and colleagues found that the specificity of ETCO2 detection was slightly worse in the arrested patient.68
Esophageal Detection Devices. The imperfect specificity of ETCO2 in the arrested patient has led to the development of alternative devices to confirm endotracheal tube placement. The principle behind the use of the esophageal detection device (EDD) relies upon the collapsibility of the esophagus compared with that of the cartilage-reinforced trachea. EDDs function by aspirating air from the endotracheal tube by negative pressure (e.g., use of a syringe-like device or a semirigid plastic bulb that reinflates when squeezed). If negative pressure is applied to a tube in the trachea, the reinforced trachea will resist collapse and the EDD will fill with air, confirming that the tube is in the trachea. Conversely, negative pressure applied to a tube in the esophagus will collapse the esophagus around the end of the tube and result in slow or incomplete filling of the EDD with air.
EDDs have been shown to be accurate in older children.69 Some studies have shown their accuracy to be poor in children younger than one year of age and when used with uncuffed endotracheal tubes.70,71 One recent operating room-based study by Sharieff and colleagues examined the accuracy of a self-inflating bulb-type EDD in children weighing fewer than 20 kg intubated with uncuffed endotracheal tubes and found an overall sensitivity of 97-100% and a specificity of 94-96%.72 Currently, no recommendations exist for the routine use of EDDs in children.
Rescue Devices in Pediatric Airway Management
Laryngeal Mask Airway. The laryngeal mask airway (LMA) is a device designed to secure the airway in the unconscious patient. It consists of a teardrop-shaped inflatable cuff surrounding a fenestrated latex window that faces the glottic opening when properly positioned. The device is inserted blindly into the open mouth of the patient and advanced until resistance is felt, at which point the cuff is inflated. Studies of the use of the LMA by various medical personnel have shown that it is easy to place and rarely associated with significant complications.73,74 LMAs are made in a range of sizes that are appropriate for all ages from neonate to adult.
It is important to remember that LMAs do not isolate the esophagus from the trachea; when properly placed, the apex of the cuff sits just above the entrance to the esophagus. Thus, patients with an LMA in place may not be protected from aspiration to the same extent as when an endotracheal tube is in place. One recent meta-analysis of data on LMA use in the operating room found that aspiration is uncommon and occurred with comparable frequency in patients with BVM ventilation alone.75 Currently, PALS does not recommend the use of LMAs in children as a result of limited data comparing their use with ETI and BVM ventilation in the resuscitation of children;25 nonetheless, they are used widely in operating room settings, EDs, and by some prehospital care systems.
Management of the pediatric airway is a skill that is critical in the emergency department. A thorough understanding of a child’s anatomy and access to and knowledge of the appropriate equipment and pharmacologic adjuncts enable the ED physician to secure the airway in a timely efficient manner that optimizes the patients outcome. No other skill is as important for the ED physician.
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