Infection

22.2.1 Historical Perspective

Historically acute airway infection was a major cause of morbidity and mortality in children. Airway obstruction due to upper respiratory infections was an important cause of child death even in well-to-do families during the preantibiotic era. Diphtheria was a major public health problem until well into the 20th century. Pediatric tracheostomy was largely developed for the treatment of severe diphtheria and was a well-established technique by the early 20th century, but it remained a treatment of last resort as the mortality in children undergoing tracheotomy was so high. ¹ The decline in tracheostomy as a treatment for diphtheria was partly as a result of the availability of antitoxin but mainly because of the development of endotracheal intubation as a method of securing the airway. Childhood immunization has now almost eradicated diphtheria in western communities but it remains a significant disease in some parts of the world.

Tracheostomy remained in widespread use for epiglottitis until the 1970s when it was also replaced by endotracheal intubation ( ▶ Fig. 22.1), better medical treatment, and the improvements in pediatric intensive care unit (PICU) facilities that permit careful monitoring and early intervention for these children. ^{2,​ 3}

Modern intensive care techniques, better training of health care staff, and the ability to safely intubate and ventilate children have completely revolutionized the management of children with acute infective airway obstruction. Instead of undergoing acute or emergency tracheostomy (with its not insignificant mortality), children with critical airway obstruction due to infection are now generally intubated to secure the airway and kept on an intensive care unit until medical treatment such as systemic steroids or antibiotics lead to an improvement in the child’s condition and extubation becomes practical.

The role of the otolaryngologist in the management of these conditions has also changed. Pediatric intensive care physicians (intensivists) or pediatricians now manage most of these children. An otolaryngologist will often be required at initial intubation to provide the option of an emergency tracheostomy or to facilitate intubation using rigid bronchoscopy. Operative surgical airway intervention is only considered if there is a failure of medical treatment resulting in failure to extubate.

22.2.2 Acute Epiglottitis

Acute epiglottitis is a condition characterized by rapidly progressive airway obstruction due to swelling of the supraglottic larynx, usually associated with severe systemic infective illness. Children—typically aged 2 to 7 years, although the condition can occur at any age—presenting with epiglottis are toxic and febrile. They tend to lean forward, keep still, drool, and demonstrate inspiratory stridor and marked features of airway obstruction. ⁴

Presentation can be atypical, and because of the relative scarcity of the condition and concern about the airway, an otolaryngologist, as well as pediatric and intensive care or anesthetic staff, is best involved early in the sequence of care.

Since the Haemophilus Influenzae (B) vaccine was introduced in the early 1990s, epiglottitis has almost disappeared in children. ⁵ The vaccine is given in the first 6 months of life (see ▶ 2).

Acute epiglottitis still occurs in adults, and sporadic cases are reported in children, typically due to vaccine failure, which is rare, or in immunocompromised children. Children with immunosuppression–for example, those undergoing treatment with toxic chemotherapy agents–may also be at increased risk. Historically, more than 90% of cases were associated with infection with H. influenzae, but, especially in immunocompromised patients, epiglottitis is occasionally caused by a different organism.

Management of Acute Epiglottitis

If epiglottitis is suspected, the child should be intubated under as controlled and safe conditions as are possible. ⁶

The child should then be carefully monitored until his/her condition improves enough to permit extubation. Epiglottitis responds to intravenous antibiotics and extubation is normally possible after a few days. Further otolaryngological intervention is normally only required if an epiglottic abscess develops, in which case the systemic response to antibiotics will be poor and the laryngoscopic appearance of the epiglottis on the intensive care unit will become increasingly abnormal. If the epiglottis is tense and bulging due to an abscess, then simple transoral drainage is normally adequate.

22.2.3 Croup or Viral Acute Laryngotracheobronchitis

Although “croup” may be a general term used to describe stridor of infectious origin, historically including diphtheria and epiglottitis, the more common modern usage of the term is to describe viral acute laryngotracheobronchitis (ALTB).

ALTB is a respiratory infection that affects children of all ages but mostly in the 6-month to 3-year age group with a peak in the second year of life when 5% of children develop one or more episodes of ALTB. The commonest infective agents are parainfluenza virus types 1 to 3, but other organisms such as respiratory syncytial virus (RSV) can be implicated. There is a 1.4:1 male preponderance. The classic features include a pyrexial illness, stridor, and a characteristic barking cough. As the mucosa of the larynx and trachea become more edematous with progressive infection, airway obstruction leads to worsening inspiratory stridor with eventual fatigue and respiratory failure.

Management of Acute Laryngotracheobronchitis

Children with ALTB are mainly treated by pediatric general medical specialists or by emergency care doctors without involving the otolaryngologist. Most will respond quickly to corticosteroids (systemic and inhaled). ⁷ Oral dexamethasone at a dose of 0.4 mg/kg is very effective. Nebulized adrenaline can bring about dramatic symptom relief. Children with mild-to-moderate croup no longer require admission to hospital if home circumstances are good and the parents can arrange rapid transport should the child deteriorate.

Because most children with this condition do respond to medical treatment, the subset of children requiring intubation may have an alternative diagnosis (bacterial tracheitis, coexistent subglottic stenosis, foreign body). It is sensible to undertake the intubation in the operating room with an otolaryngologist present and with bronchoscopy and tracheostomy equipment available should an emergency airway be needed. The diagnosis is usually obvious at laryngoscopy ( ▶ Fig. 22.2). The child is intubated and the tube left in place for several days until the edema and inflammation resolve, allowing extubation. Ear, nose, and throat (ENT) follow-up is not required in cases of uncomplicated croup.

22.2.4 Bacterial Tracheitis (Pseudomembranous Croup)

Secondary bacterial infection of a larynx and trachea already affected with viral croup can lead to much more severe inflammation with the production of mucopus and the formation of inflammatory exudates and pseudomembranes within the tracheal lumen. ⁸ The causative agents include Staphylococcus aureus, Streptococcus pneumonia, and Streptococcus pyogenes. Although this is a much rarer disease than viral croup, 2% of children admitted to hospital with croup have bacterial tracheitis. ⁹ Bacterial tracheitis is now a commoner condition than acute epiglottitis. ¹⁰

The clinical picture is generally worse than that associated with viral croup with pyrexia and increasing tracheal obstruction from the exudates. ¹¹

Patients will be toxic from bacterial infection with high white cell counts and a raised C-reactive protein.

Otolaryngological input may be required both at intubation and on occasion for therapeutic endoscopy to remove debris, sloughing, and necrotic mucosa from the airway.

22.2.5 Recurrent Respiratory Papillomatosis

This is a viral condition in adults and children (juvenile onset recurrent respiratory papillomatosis [JORRP]) characterized by exophytic, usually multiple, lesions on the mucosal surface of the aerodigestive tract ( ▶ Fig. 22.3). The larynx is mainly affected, with a particular predilection for squamocolumnar mucosal junctions.

Etiology of Juvenile Onset Recurrent Respiratory Papillomatosis

The virus is thought to be transmitted at birth by direct contact with infected secretions in the birth canal. The mode of transmission is probably more complex than this ¹² as babies born by Caesarian section can be affected, and there is almost certainly transplacental transmission of the virus as well. The traditionally quoted susceptibility factors for RRP are as follows:

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  First-born children.

  
  
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  Maternal genital warts.

  
  
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  Young maternal age.

  
  
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  Vaginal delivery.

  
  
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  Low maternal socioeconomic status.

Often, however, none of these applies.

HPV contamination of the birth canal is common (25% of pregnant women) yet JORRP is rare, approximately 1 in 25,000 children, so host susceptibility factors must come into play. In the case of children born to mothers with genital warts, HPV   deoxyribonucleic acid (DNA) has been found in one-third to one half of aerodigestive tract swabs of these babies but very few, 1 in 400, develop JORRP. At one time, particularly in the United States, caesarean section was recommended for expectant mothers with genital warts but current evidence does not support this as a protective measure against JORRP. Despite recent work on human leukocyte antigen polymorphisms that may help to identify pregnancies where the infant is at particular risk, this host susceptibility is currently unpredictable. ^{13,​ 14}

The widespread availability and uptake of HPV vaccination in girls (and in some cases in boys) in many western countries is likely to bring about a big reduction in the incidence of JORRP as this cohort of girls enter their reproductive years. ¹⁵ Vaccination was introduced as a protective measure against the development of carcinoma of the uterine cervix, where HPV has a crucial etiological role, but a reduction in the prevalence of genital tract HPV contamination—especially with types 6 and 11 where the quadrivalent vaccine against subtypes 6, 11, 16, and 18 is used—may make JORRP a condition that ENT surgeons see even more rarely in years to come.

Clinical Presentation of Juvenile Onset Recurrent Respiratory Papillomatosis

Presentation is usually with hoarseness, typically in school-age children. A small number of children may present with stridor. Younger children can be affected, and in these cases, the course tends to be more aggressive with a poorer prognosis. It is thought that the virus remains dormant in the laryngeal epithelium for several years before giving rise to the typical warty lesions. Viral particles are widely distributed in the epithelial cells even after thorough removal of the excrescences, making for the characteristic tendency for multiple recurrences.

Treatment of Juvenile Onset Recurrent Respiratory Papillomatosis

Various techniques are described, including a carbon dioxide (CO₂) laser, which for many years was the mainstay of treatment but has the disadvantages of causing heat damage to surrounding tissue, a tendency to scarring, the logistic difficulties of setting up the equipment and ensuring staff are appropriately trained, and the very small risk of airway fire.

Most units nowadays use the microdebrider ( ▶ Fig. 22.7). This is a suction device containing a high-speed rotating blade. The orifice of the hand-piece is swept along the free margin of the lesion in a “brushing” movement until normal tissue is exposed. If the papillomas are very extensive, it may be wise to do some initial débridement with an ET tube in place until the airway is safe. Careful liaison with a skilled pediatric anesthesiologist is essential.

Some surgeons favor the Coblator (ArthroCare), but it will cause thermal damage to adjacent tissue and is not widely used.

Some children manage with 6-monthly or even annual endoscopies, whereas some may need surgery as often as every few weeks. The course is variable and periods of rapid growth can be followed by periods of relative quiescence. It is the authors’ practice to arrange a repeat surgery date at each endoscopy and to instruct parents to get in touch quickly should the child become hoarse, and urgently should the child develop stridor, so that earlier admission can be expedited.

Adjuvant Medical Treatment for Recurrent Respiratory Papillomatosis

Various adjuvant medical treatments have been suggested. The evidence base for most is poor. Cidofovir, interferon, acyclovir, ribavirin, mumps vaccine, and indole-3-carbinol have been used with varying enthusiasm.

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  Photodynamic therapy works on the principle of making specific target tissues susceptible to therapeutic intervention by prior administration of a photosensitive drug and is now rarely used.

  
  
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  Cidofovir is the most often used contemporary adjuvant therapy, and even though reviews of cidofovir efficacy appear to demonstrate an improvement in outcome in a significant proportion overall, a double-blind randomized controlled trial indicates that there is no benefit over normal saline. ¹⁶ The apparent benefit of cidofovir may result from the necessary frequent debulking at the time of injection. There is some evidence to question the safety of cidofovir, and as it acts by becoming incorporated in DNA, there is real worry about its potential to facilitate malignant tissue change. ^{17,​ 18,​ 19} There is increasing interest in the therapeutic potential of the HPV vaccine (Gardasil [Merck]) and many surgeons are now recommending it for children with established JORRP. ^{20,​ 21}

Prognosis of Juvenile Onset Recurrent Respiratory Papillomatosis

JORRP is usually confined to the larynx but runs a variable course, and may become quiescent as the child progresses through adolescence. ²²

In particularly aggressive cases, the virus spreads to the tracheobronchial tree with the potential for fatal airway obstruction. These children need frequent and demanding surgery, including potassium titanyl phosphate (KTP) laser excision if disease needs to be removed from hard-to-access sites in the tracheobronchial tree and may warrant adjuvant therapy. Extension to the small airways and ultimately the alveoli results in cavitating cystic lesions in the chest and may be fatal.

Squamous carcinoma of the bronchus has been reported and in this respect JORRP can be regarded as a premalignant condition, albeit the risk is very small.

22.3 Injury and Stenosis of the Larynx and Upper Trachea

Although major trauma to the larynx and trachea can result in immediate and dramatic loss of function, injury to the upper airway more usually results in a slower process of mucosal tearing, edema, or necrosis, with healing and the formation of fibrous repair tissue. This process of scarring in a hollow tube such as the trachea tends to narrow the lumen, “cicatrization” ( ▶ Fig. 22.4). This is the etiology of the majority of the cases of acquired airway stenosis that present to the pediatric otolaryngologist.

There are several potential causes, but by far the commonest etiology of trauma to the larynx and trachea that results in airway stenosis is intubation and the use of ET tubes, that is, iatrogenic laryngotracheal stenosis.

22.3.1 Mechanisms of Injury to the Larynx and Trachea

Chemical Injury

Caustic ingestion remains a significant problem in young children. Although generally the more significant effects are seen in the pharynx and esophagus, mild chemical burns of the supraglottis are not uncommon in cases of caustic ingestion, and any child with a history of suspected caustic ingestion who is undergoing an endoscopy of the esophagus and stomach should have a careful assessment of the larynx and trachea under the same general anesthetic. Ingestion of cleaning agents was a significant public health problem in years gone by, but better product labeling, safer packaging, child-proof lids, and increased parental awareness have made for much less frequent admissions of children with caustic burns.

Thermal Injury

Inhalational burns in the pediatric airway are thankfully rare but are potentially serious. With inhalation of steam from hot liquids, significant thermal energy can be transmitted to the soft tissue of the upper airway and this tends to cause more serious laryngeal injury than hot dry gases. Laryngospasm helps to prevent burns distal to the glottis, but the supraglottis is at risk and the resulting edema may cause life-threatening airway obstruction in the acute phase. Long-term stenosis of the pediatric airway after inhalational burns is relatively uncommon.

Laser Injury

Significant long-term iatrogenic injury may be caused to the developing larynx by therapeutic use of the laser in the pediatric airway. The most commonly used laser in airway surgery worldwide is the CO₂ laser.

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  The major advantage of laser surgery is that it offers a relatively bloodless technique allowing endolaryngeal ablation of tissue (including stenosis, webs, granulations, subglottic cysts, hemangiomas) without immediate injury to surrounding tissues. The initial postoperative results can be impressive, and with judicious use, the CO₂ laser can be a very useful tool.

  
  
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  The major disadvantage is that the tissue surrounding the operated area suffers a significant degree of submucosal thermal injury, not always apparent at the time of surgery. This can lead to long-term scarring, webbing, and stenosis. On occasions, the airway obstruction resulting from iatrogenic scarring can be more problematic than the original pathology.

Laser surgery carries the risk of airway fire, although this is extremely rare. Safety precautions such as the use of “laser safe” ET tubes, wet swabs, protection of tissues outside the operative field, eye-protection for staff, and appropriate training, including refresher courses for all operating room personnel, are essential.

In the last decade, laser airway surgery has become a far less popular treatment modality amongst pediatric otolaryngologists. The microdebrider (see below) is increasingly popular. Some surgeons now use the Coblator (see ▶ 18) with good effect in the larynx and trachea, although this is not without risk of causing mucosal burns.

Blunt External Trauma

The infantile larynx lies at a higher level in the neck than the adult larynx, and blunt injuries are relatively less likely. The cartilaginous skeleton is softer, more elastic, and less likely to fracture as a result of a direct impact. ²⁴

Significant injury is generally associated with high velocity accidents, particularly a blow from the handlebars of a motorcycle or bicycle, or a horse-rider striking a fence. Although children are less likely to be involved in a high-speed accident than adults, neck injury associated with motorized vehicle including snowmobiles and quad bikes is becoming more common in children. Fortunately, significant injury is rare with very few blunt neck injuries involving the larynx.

Severity of injury can range from minor contusions to complete laryngotracheal disjunction, which can be fatal (Box 22.1 ²⁵).

Management of Blunt Laryngeal Injuries

The management of blunt laryngeal injuries ^{26,​ 27,​ 28} can thus be summarized as follows:

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  Recognize the injury:

  
  
  
  
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    Suspect significant injury to the larynx and trachea with any of the following:

    
    
    
    
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      History of significant force of impact to the anterior neck.

      
      
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      Loss of voice, stridor, dysphagia or odynophagia.

      
      
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      Bruising around the neck or chest.

      
      
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      Loss of palpable laryngeal landmarks or obvious palpable fracture.

      
      
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      Surgical emphysema or free air on plain X-rays.

      
      
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      The airway may seem stable on initial presentation but can rapidly deteriorate with the onset of mucosal swelling.

  
  
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  Investigate:

  
  
  
  
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    Flexible nasoendoscopy is extremely useful in cooperative children.

    
    
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    Plain X-rays are of limited use as children’s cartilage is not calcified but you may identify free air and also injury to the adjacent cervical spine.

    
    
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    The best investigation of the injured larynx is computed tomography (CT) scanning. This may not be practical if there is significant concern about impending airway obstruction.

  
  
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  Secure the airway:

  
  
  
  
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    Where there is airway obstruction or significant concern, make the airway safe with an ET tube or a tracheostomy.

    
    
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    Simple edema and submucosal hematoma can be treated by intubation, whereas major disruption of the laryngeal skeleton (such as cricotracheal separation) can be worsened by standard intubation techniques.

    
    
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    The best approach is to examine and secure the airway using rigid endoscopy and then decide on the need for tracheostomy and/or immediate laryngeal repair under the same anesthetic.

Intubation Trauma

History

Intubation trauma is a significant cause of laryngotracheal morbidity in children. Long-term ventilation for premature neonates, who earlier would almost certainly not have survived, started in the 1960s, and with it came a huge increase in intubation-related stenosis in the pediatric airway. At the time, permanent tracheostomy was the only effective available intervention. In the 1980s, pioneers including Cotton, Seid, and Zalzal started to report novel surgical techniques to treat subglottic stenosis so as to remove tracheostomies from affected children or to avoid tracheostomy altogether. At the same time, a greater understanding of the causes of intubation injury and of the dangers of prolonged, ill-fitting, and inappropriate tubes contributed to by pioneer workers such as Benjamin and Lindholm changed neonatal intensive care unit (NICU) practice. The risk of subglottic stenosis is now very much reduced, but the increasing number of extremely premature and medically complex neonates and children surviving NICUs means that more children are intubated and ventilated in large children’s hospitals, and the laryngotracheal consequences of intubation injury continue to present to the pediatric otolaryngologist. ²⁹

Pathogenesis/ Mechanism of Injury

Mucosal injury can be caused by either of the following:

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  The endotracheal intubation itself.

  
  
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  The continued presence of a tube in the lumen of the airway.

Emergency or repeated intubation is more likely to result in airway trauma. The physical process of intubation may cause a breach in the mucosal surface, which leads to ulceration with the potential for scarring and cicatrization. On rare occasions, intubation can cause more significant acute injury including arytenoid dislocation or a tracheal tear.

The presence of the ET tube in the airway, particularly if it is too “snug” a fit, leads to edema and then ischemia of the mucosa. Modern tubes tend to be made of material that causes minimal tissue reaction. The early “red rubber” tubes were especially liable to cause stenosis, and there is some evidence that repeated contact between the tube and the mucosa during respiratory cycles may predispose to injury. Ischemia leads to mucosal ulceration and the formation of granulation tissue. The healing processes after ulceration then leads to fibrosis, deposition of scar tissue, and narrowing of the lumen of the airway.

Severe stenosis is becoming far less common as medical care of very sick babies improves, but pediatric otolaryngologists are increasingly seeing evidence of mucosal ischemia giving rise to vesicular “cobblestone” reactions in the subglottic mucosa (subglottic cysts; ▶ Fig. 22.6). These may be large enough to obstruct the airway when the child is extubated and probably represent an early stage in the evolution of subglottic stenosis. The larger cysts may need surgical debulking by marsupialization or using the microdebrider ( ▶ Fig. 22.7).

Trauma from the ET tube can also cause inflammatory swellings on the mucosal surface of the vocal cords ( ▶ Fig. 22.8, ▶ Fig. 22.9). A large solitary lesion can project into the lumen of the glottis: “intubation granuloma.” These will usually settle when the tube is removed but may be large enough to warrant endoscopic removal.

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