Anaesthesia for complex airway surgery in children

Anaesthesia for complex airway surgery in children Vimmi Oshan FRCA Robert WM Walker DCH FRCA

Communication between surgeon and anaesthetist is paramount. A spontaneous ventilation technique is the preferred initial technique and allows for diagnosis of dynamic airway obstruction. Anaesthetic techniques for airway surgery must take into account the modes of ventilation and anaesthesia, and the need for surgical access. Anaesthetic techniques may be dictated by coexisting medical problems. Dexamethasone and nebulized epinephrine are essential parts of the anaesthetic technique and recovery plan.

Vimmi Oshan FRCA Specialist Registrar in Paediatric Anaesthesia Royal Manchester Children’s Hospital Manchester UK Robert WM Walker DCH FRCA Consultant Paediatric Anaesthetist Royal Manchester Children’s Hospital Oxford Road Manchester M13 9WL UK Tel: þ44 (0)1617011263 Fax: þ44 (0)1617014875 E-mail: [email protected] (for correspondence)

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The successful management of children undergoing operative procedures for complex congenital and acquired airway anomalies requires a high level of skill and cooperation between surgeon and anaesthetist.1 This article will review first the more common airway pathologies requiring intervention, and then will review the anaesthetic techniques that can be used in their management.

Upper airway pathology

damage resulting in cyst formation. Often, the period of intubation is relatively short, but after a delay of several months, biphasic stridor develops with the concomitant signs of upper airway obstruction. Biphasic stridor always necessitates intervention and these children should undergo bronchoscopy and surgical marsupialization of the cysts using microlaryngeal instruments as a matter of urgency (Fig. 1). Supraglottic cysts are very rare and are also treated by marsupialization.

Laryngomalacia Laryngomalacia is the most common congenital cause of upper airway obstruction.2 The presentation is usually within 2 weeks of birth with inspiratory stridor which is made worse by feeding and lying supine. The condition is caused by collapse of the supralaryngeal structures during inspiration. Short aryepiglottic folds, redundant arytenoid tissue, and a long curled epiglottis characterize the condition. This may be diagnosed and assessed in the outpatient department by flexible nasendoscopy. Many children require no treatment with the condition worsening for 6–9 months and then abating. Those with severe progressive or atypical symptoms should be formally assessed by rigid bronchoscopy under general anaesthesia. This also allows examination for a second lesion which occurs in 20–30% of cases. Only 5–10% require surgical treatment. This includes division of the aryepiglottic folds, resection of excess arytenoid tissue, and suspension of the prolapsing epiglottis. This can be performed using a ‘cold steel’ approach using microlaryngeal equipment or using a carbon dioxide laser.

Subglottic cysts Subglottic cysts are an increasingly common cause of airway obstruction in children. All of these children have had a period of tracheal intubation at birth, and this has caused mucosal

Respiratory papillomatosis Juvenile onset respiratory papillomatosis is an unpredictable disease that can spread throughout the respiratory tree. It is characterized by multiple squamous papillomatous lesions of viral origin which in the juvenile form of the disease have a predilection for the true vocal cords and the anterior commisure. The presentation will vary depending on the site of the papllomata. Lesions on the true vocal cords and the anterior commisure cause hoarseness, whereas widespread disease may present more slowly with dyspnoea on exertion or on occasion severe respiratory distress. The human papilloma virus, typically type 6 and 11, are responsible for this disease which affects children usually between the ages of 2–5 yr, but the onset can be at any age. There is unfortunately no cure for recurrent respiratory papillomatosis and many treatment modalities have been tried over the years ranging from steroids, podophylin, radiation, ultrasound, and acyclovir, but to no avail. Current management is based on a conservative surgical approach aimed at improving symptoms but limiting scarring and damage to the laryngeal structures. This is done by repeat debulking of the lesions by a microdebrider technique or by carbon dioxide laser. The latter technique is used less often recently because of the higher risk of scarring.

doi:10.1093/bjaceaccp/mks058 Advance Access publication 11 December, 2012 Continuing Education in Anaesthesia, Critical Care & Pain | Volume 13 Number 2 2013 & The Author [2012]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: [email protected]

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Key points

Matrix reference 2D02; 3D00

Anaesthesia for complex airway surgery

Distal seeding of the papilloma is possible and anaesthetic techniques involving tracheal intubation have been implicated in this. Therefore, a ‘tubeless’ technique would be ideal.

Subglottic haemangioma Subglottic haemangiomas are vascular anomalies due to endothelial hyperplasia. These children are asymptomatic at birth but develop biphasic stridor between the ages of 2 –6 months. The initial phase or proliferative phase lasts up to a year, and during that time, symptoms increase. After that, the haemangioma starts to regress, the involution phase, with decreasing symptoms over the following 2 –5 yr. There are a number of treatments available for this condition, and the selection of the most suitable treatment depends on the age of the child, the degree of subglottic narrowing, and the extent of the haemangioma. Small unilateral lesions can be treated by laser ablation and more recently by an open excision. A tracheostomy as a means of providing a safe airway while waiting for natural regression is often used when more than 50% of the airway is lost. Medical therapy can be via either systemic or intralesional steroids, or more recently by the administration of propranolol, which by its action on vasoactive endothelial growth factor encourages involution of the haemangioma. Non-circumferential haemangiomas can be treated by an open surgical excision with success. Should this approach be used, there will be a need for a period of postoperative intubation to splint the airway and good postoperative intensive care and sedation is essential for the success of this technique. Circumferential haemangiomata are now treated with propranolol as a first-line treatment.

Tracheomalacia This is a poorly understood condition presenting early in life due to the ‘softness’ of the tracheal cartilages, causing collapse of a portion of the airway.3 The condition may present with coughing or expiratory stridor, frequent infections, or ‘dying spells’. It may

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Subglottic stenosis Subglottic stenosis can be congenital or acquired due mainly to intubation trauma. Patients present with stridor (which may be biphasic), breathlessness, or recurrent infections. In patients with a severe narrowing, the treatment will initially be a tracheostomy to bypass the obstruction and then at a later stage a laryngotracheal reconstruction. In this procedure, a wedge of cartilage from a costal cartilage is slotted anteriorly into a vertical incision made in the cricoid cartilage to increase the airway lumen. Some stenotic lesions may also require a posterior cartilage wedge. After surgery, the airway is assessed and if the patency is adequate, the tracheostomy decannulated at 3–6 months. Success rates are in the region of 80–90% for this surgery.

Laryngeal clefts This rare problem results from failure of development of the posterior cricoid lamina or the septum between the trachea and the oesophagus. The presentation is often feeding difficulties and choking on feeds, with or without stridor, recurrent chest infections, and cyanotic spells. Laryngeal clefts are subdivided into four grades. Grade 1 is a cleft down to the cricoid cartilage, grade 2 down to and including the cricoid cartilage, grade 3 is a cleft below the cricoid cartilage but above the sternal notch, and grade 4 is the one which extends intrathoracically. Treatment is usually conservative for grade 1 clefts, but grades 2 –4 require surgical management. Grades 2 and 3 can be managed by endoscopic repair. Management of grade 4 clefts require management in a cardiothoracic centre and repair on cardiopulmonary bypass (Fig. 2).

Continuing Education in Anaesthesia, Critical Care & Pain j Volume 13 Number 2 2013


Fig 1 View of subglottic cysts in an infant before surgical treatment.

be primary (where the tracheal rings are thought to be soft), or secondary, when there is extrinsic compression, for example, due to vascular compression or due to a trachea oesophageal fistula. Many cases are self-limiting, but in severe cases, there are a range of medical and surgical options ranging from continuous positive airway pressure (CPAP) to aortopexy, or tracheostomy to stent the trachea. Internal stenting to reinforce the internal structure of the airway can be used for tracheal and bronchial segments.4 These self-expanding stents are made of metal mesh (nickel–titanium alloy) and can be placed bronchoscopically or radiologically. The unexpanded stent is placed on an inflatable balloon catheter and placed exactly in the airway under bronchoscopic or radiological control. They are then expanded by inflating the balloon catheter to the recommended diameter. Uncovered mesh will be epithelialized to some extent. Complications of stenting can be serious and include displacement and granuloma formation causing airway obstruction. Removal of stents may be necessary and can be hazardous. Recent work has shown that both aortopexy and tracheal stents are effective treatments in the management of tracheomalacia. However, although aortopexy is associated with early postoperative complications, tracheal stents are associated with a higher failure rate and more severe morbidity and mortality.5


Fig 2 A laryngeal cleft type III.

Anaesthetic techniques Preoperative preparation

Anaesthetic management General principles During normal circumstances, flow through the airway is laminar and follows the principles of the Hagen –Poiseuille law which states that the flow rate is directly proportional to the pressure gradient and cross-sectional area of the airway. A small reduction in the radius of the airway will cause a huge decrease in flow as flow relates to the fourth power of the radius (Fig. 3). For example, in quiet breathing, a reduction in airway radius from 2 to 1 mm would result in at least a 16-fold reduction in flow. However, flow through a narrowed airway in an infant soon becomes turbulent and under these circumstances, flow occurs in both axial and radial directions. A higher pressure difference is therefore needed to maintain a given flow rate during turbulent flow. The relationship between driving pressure and flow in turbulent flow is alinear: ˙ 2. In order to double the flow rate under turbulent condiDP a V tions, the pressure difference must be more than doubled. Therefore, infants and children who present with stridor and signs of upper airway obstruction can have significant narrowing of the upper airway. The anaesthetic technique must take the potentially severe narrowing of the airway into account and the potential difficulty either manually ventilating the patient or placing a tracheal tube. Spontaneous respiration and the maintenance of spontaneous respiration throughout the technique for children with upper airway obstruction have much to be recommended. This technique maintains a degree of muscle tone and this helps enormously to maintain gas exchange allowing the anaesthetist time. This enables the surgeon to perform a diagnostic bronchoscopy assessing both pathology and any dynamic obstruction before any required operative surgery. However, there are a few circumstances where this technique may not be feasible such as those children with severe neurological conditions or lower respiratory disease and alterations to the technique become necessary.

A ‘drying’ agent is useful such as oral atropine (20 mg kg21) or oral glycopyrrolate (50 mg kg21). The use of a sedative agent must be carefully considered. Fasting times should be 2 h for clear fluid, 4 h for breast milk, and 6 h for food and formula milk. However, in the emergency situation, there may be a pressing need to improve the airway and respiratory status and this will override the fasting period. In this situation, some precautions can be taken against the ‘full’ stomach, such as a degree of head-up tilt, the use of prokinetic agents, and the passage of a naso- or orogastric tube after induction. The use of cricoid pressure and the rapid sequence induction has no place in this scenario, although preoxygenation is always useful. There are essentially three basic techniques to discuss.

Inhalation induction and maintenance with a volatile agent This is the most commonly used technique and uses maximal oxygen usage and a volatile which also has useful bronchodilatory effects.6 The induction is performed using sevoflurane in 100% oxygen. An i.v. cannula can then be placed. The induction may be prolonged due to the compromised airway, but with time and patience and modest amounts of CPAP, the airway can be maintained and the child deepened to a level where the airway can be sprayed with topical local anaesthetic, usually lidocaine (3 –5 mg kg21). If the child is too light, at this point coughing, desaturation, and laryngospasm may complicate the induction. This can be avoided by ensuring the child is at a deep level of anaesthesia. After this, a nasopharyngeal airway can be placed and the child continues to breathe oxygen and high levels of sevoflurane to maintain anaesthesia. Any periods of apnoea commonly seen during a sevoflurane induction can be treated by gentle stimulation and CPAP. Taking over ventilation, other than a few supportive breaths is better avoided or the respiratory drive may be taken away completely. This technique has the advantage that the child essentially can


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The initial agreed plan between surgeon and anaesthetist should recognize the principles of continual oxygenation and anaesthesia and the need for surgical access and both may have to compromise depending on the situation. For example, clearing respiratory papillomatosis with a tracheal tube in place is not possible and may cause seeding of the papillomata throughout the airway. Similarly, there are times when oxygenation is compromised that necessitate intubation and the surgeon may be forced to work around it. Rescue plans are also worth considering as it is not always possible to intubate patients with tight stenotic lesions. The Storz ventilating bronchoscope may rescue many situations and this may be the instrument of choice if the lesion is intrathoracic. In higher, extrathoracic airway lesions, a tracheostomy may be the preferred rescue option to initially secure the airway before proceeding, for example, subglottic stenosis or large subglottic haemangioma.


Fig 3 The Hagen– Poiseuille law states that under conditions of laminar flow, where r is the radius of a tube, P1 2P2 the pressure decrease between points 1 and 2, n the viscosity of the gas, and l the length of the tube. Doubling the radius increases the flow 16 times.

Total i.v. anaesthesia and spontaneous respiration Propofol and remifentanil infusions can be used as an alternative to the above technique to provide anaesthesia for airway surgery.7 The induction can be carried out with a gaseous induction or an i.v. bolus of propofol (1–5 mg kg21). Patients breathe 100% oxygen via the anaesthetic circuit, and after induction infusions of propofol (dose range 12 up to 30 mg kg21 h21) and remifentanil (dose range 0.1 –0.2 mg kg21 min21) started. The initial dose of propofol is given over 3–5 min to maintain spontaneous respiration if possible. Apnoea is managed by CPAP and gentle assisting of respiration. Hypotension and bradycardia may occur with the higher range of these infusion rates. The infusions are titrated to the respiratory rate aiming for a rate of 10 –15 bpm in older children and roughly half normal respiratory rate in younger children and infants. The rate of remifentanil should be adjusted by 0.05 mg kg21 min21 increments to attain the desired respiratory rate and the propofol infusion rate is adjusted depending on BIS monitoring or patient movement. Lidocaine topical spray is applied to assist the bronchoscopy and reduces the incidence of coughing and laryngospasm. This technique has a similar complication profile to the volatile technique, although some studies suggest a higher incidence of unwanted movement. There is possibly a slightly higher rate of apnoea with this technique but this is offset by the antitussive effects of remifentanil and the reduction in upper airway reflexes provided by propofol.

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High-frequency jet ventilation Subglottic jet ventilation techniques via transglottal cannulas are used in adult practice; however, in paediatric practice, the size of a cannula of even 2– 3 mm is impractical and barotrauma and air trapping are risks. A supraglottic superimposed high-frequency jet ventilation technique has been described which uses total i.v. anaesthesia and muscle relaxation to aid airway surgery.8 This technique, however, is not common practice in the UK.

Postoperative care After surgery to the airway in a small infant or child, close observation is essential to pick up worsening airway obstruction due to either swelling or retained secretions. It is good practice to administer dexamethasone intraoperatively to reduce postoperative swelling (dose 250–500 mg kg21) and use topical 1:10 000 epinephrine during surgery. Nebulized epinephrine (1:1000, 3–5 ml) can be used after operation to improve the airway swelling, and a second dose of i.v. dexamethasone can be given 12 h later. Good nursing care is essential, maintaining a clear upper airway and alerting the anaesthetist if the patient is going downhill. The recovering child must be stable before the anaesthetist embarks on further cases. If after epinephrine, dexamethasone, good care, and suctioning the airway is not adequate, the patient should be intubated and ventilated for a short period and extubation attempted later. It may be that intubation and postoperative ventilation forms part of the plan, and if this is the case, the tracheal tube size should be carefully chosen to avoid additional swelling and the patient adequately sedated to avoid excessive movement of the tracheal tube. Extubation may take place in the operating theatre after a further bronchoscopic examination.

Clinical case A 2-month-old, 4 kg child born at 28 weeks presented with worsening biphasic stridor and upper airway obstruction causing respiratory distress and feeding difficulties. The child was taken to theatre as an emergency despite being fasted only 3 h for breast milk. The infant was anaesthetized in theatre with full monitoring, preoxygenated, and an inhalation induction with 100% oxygen and sevoflurane performed. I.V. access was then achieved. It took some 12 –15 min on 8% sevoflurane to achieve a deep level of anaesthesia and at that point, the larynx was sprayed with lidocaine and a nasopharyngeal airway passed. Anaesthesia was maintained by flooding the pharynx with 100% oxygen and 8% sevoflurane. The infant had occasional periods of apnoea which responded to gentle



control their own depth. If they lighten they breathe more and if they deepen they breathe less. This technique can be used for almost all ages and sizes of patients, but in older patients, supplementation with i.v. agents may be necessary. The disadvantages of this technique are that CO2 monitoring is difficult and monitoring of respiration must be done by direct vision of the patient and of the monitor to ensure patency of the airway. CO2 monitoring can be done by intermittent placement into the trachea of a catheter such as a small Cook airway exchange catheter to ensure that carbon dioxide levels are not too high. Environmental pollution is another problem with this technique. However, this simple technique if performed well can solve a multitude of difficult problems and can be maintained to allow surgery on a variety of conditions already mentioned.

Potential benefits of this technique are unobstructed surgical access, the ability to assess dynamic airway function, the ability to achieve deep anaesthesia which is not airway-dependent, and the lack of environmental pollution.


Declaration of interest None declared.

References 1. Myer CM, III, Cotton RT, Shott SR, eds. The Pediatric Airway: An Interdisciplinary Approach. Philadelphia: JP Lippincott Company, 1995 2. Bruce IA, Rothera MR. Upper airway obstruction in children. Paediatr Anaesth 2009; 19 (Suppl. 1): 88– 99 3. Austin J, Ali T. Tracheomalacia and bronchomalacia in children: pathophysiology, assessment, treatment and anaesthesia management. Paediatr Anaesth 2003; 13: 3 –11 4. Filler RM, Forte V, Chait P. Tracheobronchial stenting for the treatment of airway obstruction. J Pediatr Surg 1998; 33: 304– 11 5. Valerie EP, Durrant AC, Forte V, Wales P, Chait P, Kim PC. A decade of using intraluminal tracheal/bronchial stents in the management of tracheomalacia and/or bronchomalacia: is it better than aortopexy. J Pediatr Surg 2005; 40: 904–7 6. Richards SD, Kaushik V, Rothera MR, Walker R. A tubeless anaesthetic technique for paediatric laryngeal laser surgery. Int J Pediatr Otorhinolaryngol 2005; 69: 513–6 7. Malherbe S, Whyte S, Singh P, Amari E, King A, Ansermino JM. Total intravenous anesthesia and spontaneous respiration for airway endoscopy in children—a prospective study. Paediatr Anaesth 2010; 20: 434–8 8. Mausser G, Friedrich G, Schwarz G. Airway management and anesthesia in neonates, infants and children during endolaryngotracheal surgery. Paediatr Anaesth 2007; 17: 942– 7

Please see multiple choice questions 9– 12.


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stimulation and rigid bronchoscopy commenced. Bronchoscopy revealed significant subglottic cysts as seen in Figure 1 and the decision was made to marsupialize them. The suspension laryngoscope was then placed and the microscope brought in. The infant continued to breathe sevoflurane between 6% and 8% to maintain oxygenation and anaesthesia. A small amount of 1:10 000 epinephrine (0.5 ml) was sprayed subglottically and then using microlaryngeal instruments, the cysts drained and marsupialized. After this, the infant became apnoeic for a short time and a tracheal tube, size 3.0, was inserted by the ENT surgeon. After spontaneous respiration commenced again, the tube was removed and the subglottis and the rest of the airway checked. The infant was given dexamethasone 1 mg during the procedure and another 0.5 ml of 1:10 000 epinephrine was sprayed into the subglottis before awakening. The infant woke up after 5 min and was looked after in the recovery room for an hour during which the infant received a prophylactic epinephrine nebulizer (dose 3 ml 1:1000), but otherwise recovered well. The infant was looked after in the high dependency unit for 24 h before discharge to the ward.