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Anaesthesia for elective ear, nose and throat surgery in children
Paediatrics
Anaesthesia for elective ear, nose and throat surgery in children
Preoperative assessment In addition to the standard components of a preoperative assessment (Anaesthesia and Intensive Care Medicine 2006; 7: 375–9), the following are particularly pertinent to paediatric ENT surgery: co-existing syndromes, recent upper respiratory tract infection (URTI), upper airway obstruction during sleep and bleeding diatheses. Any congenital, chromosomal or syndromic abnormalities should be specifically identified. Commonly encountered examples include children with Down’s syndrome, who often require middle ear surgery (which is more challenging as they have narrow external auditory canals) and adenotonsillectomy for obstructive sleep apnoea; patients with branchial arch abnormalities, who present for reconstructive ear surgery and may be extremely difficult to intubate; infants with cleft lips and/or palates, which may be isolated anomalies but may also be part of syndromes whose other features (particularly cardiac) may have an impact on the anaesthesia management. A history of active or recently resolved upper respiratory tract infection is commonly elicited in children scheduled for ENT surgery. Fitness for anaesthesia should be assessed on a case-bycase basis. Generally, a child with clear nasal secretions who is systemically well, with no associated fever or chest signs is considered fit for anaesthesia.1 A cough is a sign of increased airway irritability and portends an elevated risk of airway complications such as breath-holding, laryngospasm and desaturation. These risks are greater if the larynx is to be intubated or instrumented. Other risk factors for increased airway complications include nasal congestion, mucopurulent secretions and passive smoking. Children presenting for adenotonsillectomy typically experience varying degrees of upper airway obstruction (UAO) when sleeping. Preoperatively, a thorough assessment of the degree of obstruction should be obtained by history and examination (Table 1). The diagnosis is usually informal and subjective, based on parental reports of snoring, transient apnoeas, frequent nocturnal awakening and, in more severe cases, daytime somnolence or hyperactivity, behaviour problems and altered school performance. Most children will have histories consistent with only mild OSA. Examination may reveal obesity, adenoidal facies
Permendra Singh Simon Whyte
Abstract This review outlines anaesthetic considerations for commonly performed elective ear, nose and throat procedures, which constitute a major portion of the paediatric anaesthesia workload. Most routine surgery can be performed on a daycare basis, but careful preoperative assessment is vital to identify those patients who are unsuitable for daycare surgery owing to complications of their presenting illness (e.g. obstructive sleep apnoea; OSA) or other co-morbidities. Children undergoing middle ear surgery need special attention to prevent bleeding, hypothermia and postoperative nausea and vomiting (PONV). Adenotonsillectomy is most commonly performed to relieve the symptoms of OSA. The main anaesthetic concerns are analgesia, PONV, risk of postoperative haemorrhage and postoperative disposition. Daycare tonsillectomy involves careful patient selection and good communication with families regarding the postoperative phase and potential complications. Use of lasers is common in airway surgery; associated risks include airway fire and injury to the eyes of the patient and theatre staff.
Keywords adenotonsillectomy; daycare; elective; otolaryngology; paediatrics
Introduction Elective ear, nose and throat (ENT) surgery in American Society of Anesthsiology (ASA) stage 1 or 2 children takes place in almost every hospital. The anaesthetic challenges include appropriate selection of day-case patients, sharing the airway with the surgeon, managing postoperative nausea and vomiting (PONV) and patient and personnel safety issues surrounding the use of lasers.
Symptoms and signs suggestive of sleep-disordered breathing in children
Permendra Singh, MBBS, FRCA, is a Specialist Registrar in Anaesthesia. He obtained his medical degree from India and undertook his anaesthesia training in India and in the UK. He has completed a fellowship in paediatric anaesthesia at the British Columbia Children’s Hospital in Vancouver, Canada. Conflicting interests: none declared.
Daytime symptoms
Signs
Snoring
Daytime sleepiness
Obesity
Apnoea
Hyperactivity
Tonsillar hypertrophy
Arousals or wakening
Poor concentration
Mouth-breathing Failure to thrive
Enuresis
Simon Whyte, MBBS, FRCA, is a Paediatric Anaesthetist in Vancouver, Canada. He obtained his medical degree in 1994 from the University of Newcastle upon Tyne, and undertook his anaesthesia training in Durham, Middlesbrough and Liverpool. His research interests include perioperative long QT syndromes and advanced airway management in children. Conflicting interests: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 10:4
Night-time symptoms
Night sweats Difficult to rouse in the morning Table 1
186
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Paediatrics
to develop airway obstruction in the postoperative period, when the anaesthetic effects on upper airway tone and reflexes are still compromising the airway. The development of idiopathic pulmonary oedema following the relief of upper airway obstruction has also been reported. In severe OSA, the hypoxaemia and hypercarbia that result from the cyclical obstruction–hypoventilation– arousal sleep pattern in these children can produce a compensated respiratory acidosis and pulmonary hypertension. In end-stage disease, cor pulmonale and cardiac arrhythmias can result.
or obviously enlarged tonsils. A nasendoscopy may have detailed the degree of any adenoidal obstruction of the nasopharynx. Children with severe symptoms of OSA may have been assessed with overnight pulse oximetry, or formal polysomnography. Plans should be made preoperatively for children with OSA who have risk factors for postoperative complications (Table 2) to be monitored in a high-dependency setting for 24 hours postoperatively. A history of increased bruising or easy bleeding should be sought and investigated. Haemorrhage during or after adenotonsillectomy is an important complication (see below), whereas middle ear surgery can be rendered impossible by even small amounts of bleeding.
Anaesthetic considerations: presence and severity of sleepdisordered breathing; potentially difficult airway; potential pulmonary hypertension; ventilation strategy; analgesic strategy; PONV prophylaxis; postoperative disposition; postoperative bleeding.
Common ENT procedures Myringotomy and tympanostomy tubes Anaesthetic considerations: this is usually performed as a daycase procedure; therefore, emphasis should be on adequate pain relief and quick recovery.
Preoperatively: the anaesthetist should gain a sense of how bad the child’s airway obstruction is during sleep, as this will reflect the potential airway obstruction on induction of anaesthesia. In a minority of patients, objective information will be available, in the form of results from overnight pulse oximetry or formal polysomnography. In the vast majority, however, an impression is gained from the subjective observations of parents. Important signs and symptoms are detailed in Table 1. Other preoperative enquiries should aim at eliciting any history suggestive of bleeding diathesis, risk factors for PONV and active or recent tonsillitis (which is a risk factor for postoperative haemorrhage). Sedative premedication is relatively contraindicated in patients with OSA, as it may compound upper airway obstruction during or even before induction. Analgesics such as paracetamol or a NSAID such as ibuprofen may be given preoperatively to these patients.3 Postoperative disposition should be agreed upon preoperatively. Children chosen for daycare should have good overall medical health; no central or obstructive sleep apnoea; a normal bleeding history and profile; adequate social circumstances; and should preferably live near the hospital.4
Preoperatively: assess for active or recent URTI (common). Many children undergo repeated operations and may have increased anxiety around or specific preferences for induction of anaesthesia. Analgesia with oral paracetamol (acetaminophen) and/or a non-steroidal anti-inflammatory drug (NSAID) is appropriate. Intraoperatively: the airway can be maintained either with a face mask or laryngeal mask airway (LMA) while the patient breathes spontaneously. A dose of ondansetron 0.15 mg/kg may be given intravenously (i.v.) to minimize PONV. Postoperatively: analgesic requirements are highly variable between children. Some may occasionally require intravenous opioid. Adenotonsillectomy This common procedure is performed on a daycare basis in many hospitals. OSA is now the commonest indication for adenotonsillectomy in children, although good-quality evidence of its efficacy is lacking.2 Careful patient selection and preoperative assessment is vital to avoid complications. Children with OSA are more prone
Intraoperatively: induction may be by either the inhalational or the intravenous route, though induction with propofol might be preferred in cases where there is no obvious airway obstruction to reduce the incidence of PONV. Fentanyl in a dose of 1–2 μg/kg may be given to provide intraoperative analgesia. A preformed south-facing oral RAE (Ring, Adair and Elwyn) tracheal tube or a reinforced LMA may be used to maintain the airway. A LMA is useful in the recovery phase since it can be left in place until the patient’s reflexes return, whereas an endotracheal tube raises the dilemma of extubation at a deep plane of anaesthesia versus awake extubation.5 The pros and cons of using a LMA are listed in Table 3. Attention has to be given to careful insertion of the operative mouth gag in either technique, ensuring that the airway device remains unobstructed. After insertion of the gag a manual check for ease of lung inflation should be performed before surgery begins. Children with significant OSA may have a compensated respiratory acidosis as a result of nocturnal hypercarbia, although this is likely to be far less common than in adults with OSA. Ventilating such patients to normocapnia will delay restitution of spontaneous ventilation at the end of the procedure.
Risk factors for postoperative complications in children with obstructive sleep apnoea undergoing adenotonsillectomy • Age younger than 3 years • Cardiac complications of OSA • Failure to thrive • Obesity • Prematurity • Recent respiratory infection • Craniofacial anomalies • Neuromuscular disorders OSA, obstructive sleep apnoea.
Table 2
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Paediatrics
tonsillectomy site; continued presence of blood in the vomitus should prompt the surgeon to look for primary bleeding at the operative site. Length of stay: protracted emesis and primary haemorrhage have the greatest incidence in the first 6 hours after surgery. Duration of postoperative stay in the hospital can vary, depending on the individual patient and the surgeon. Parents should be given clear written and verbal guidelines regarding when and how to seek medical assistance postoperatively.
Advantages and disadvantages of airway maintenance with a laryngeal mask airway during tonsillectomy Advantages
Easy to insert Allows for lighter level of anaesthesia Smoother emergence without tracheal stimulation
Disadvantages
May retract cephalad in the pharynx and obstruct surgical view Does not protect against secretions entering the glottic opening
Middle ear surgery: mastoidectomy, myringoplasty and cochlear implantation Anaesthetic considerations: minimize bleeding; PONV prophylaxis; potentially long surgery with attendant risks of pressure injuries and hypothermia; difficult airway access; facial nerve monitoring.
Table 3
Preoperatively: assess for bleeding diatheses and risk factors for PONV.
Estimated total intravascular blood volume should be calculated for each child (neonates, 90 ml/kg; infants, 80 ml/kg; children, 70 ml/kg) and blood loss should be closely monitored. Isotonic intraoperative fluids should be given and the intra venous cannula kept in situ postoperatively in case of primary haemorrhage. Analgesic strategies for adenotonsillectomy are the subject of ongoing confusion and controversy. Concern has arisen over the use of NSAIDs because of their antiplatelet effect and the potential risk of increased bleeding. A Cochrane review of this issue concluded that there is no evidence that NSAIDs cause bleeding that increases the need to return to theatre and that, moreover, PONV is reduced when NSAIDs are used.6 Long-acting opioids also cause concern because they may contribute to ongoing airway obstruction postoperatively. It is assumed – without much evidence to support or refute it – that children with OSA will exhibit the same increased sensitivity to the central nervous system depressant effects of opioids seen in adults with OSA. For these reasons, long-acting opioid use should be minimized as far as possible in children undergoing adenotonsillectomy for upper airway obstruction. Tramadol may cause fewer episodes of postoperative desaturation than morphine.7
Intraoperatively: control of bleeding allows the surgeon to operate through the microscope in a bloodless field. Avoid hypertension and hypercarbia. Preservation of the facial nerve is attained by use of facial nerve monitoring and requires neuromuscular function. If neuromuscular block is needed to facilitate smooth intubation, choose a dose and an agent that ensures the return of function before the need for neuromuscular monitoring arises. Long duration of surgery means that hypothermia is a risk. Temperature monitoring and methods to prevent heat loss are recommended. Airway access is difficult during the surgery, demanding meticulous attention to securing airway devices and breathing circuit connections and to preventing disconnections. Dural breach is a possible complication during middle ear surgery that needs careful attention in the form of antibiotic cover and vigilant postoperative observation. Prevention of PONV: middle ear surgery is associated with a high risk of PONV. Single-agent prophylaxis with ondansetron 0.15 mg/kg is always indicated and dual therapy (dexamethasone 0.15 mg/kg and ondansetron 0.05 mg/kg) should be given if other risk factors are present.8 Other strategies to mitigate the risk include good hydration, the use of total intravenous anaesthesia and avoidance of long-acting opioids. Avoidance of graft displacement: when the middle ear has been closed by a myringoplasty, termination of N2O will result in negative middle ear pressure being applied to the graft. Avoiding the use of N2O or switching it off about 20 minutes before the ear is closed avoids the pressure on the newly applied graft.
Postoperatively: patients should be recovered on their side in a head-down position until fully awake. Fluids should be prescribed postoperatively for maintenance until the child has resumed drinking. Paracetamol and NSAIDs should be given regularly for postoperative pain, combined with codeine (if required) in patients with no or mild OSA. Persistent vomiting and poor oral intake are the most common causes of unscheduled overnight admission after daycare adenotonsillectomy. Intraoperative administration of i.v. ondansetron 0.05 mg/kg and dexamethasone 0.15 mg/kg are given to prevent PONV.8 If the child has postoperative vomiting despite antiemetic prophylaxis then maintenance intravenous fluid therapy should be continued and rescue antiemetics given from a different pharmacological class from those used for prophylaxis. Post-tonsillectomy haemorrhage can be life threatening. This affects about 1–2% of children in the first 24 hours, although only about 0.06% need general anaesthesia for haemostasis.9 Close watch should be kept for bleeding, dehydration and hypovolaemia. Vomiting can lead to exacerbation of bleeding from the
ANAESTHESIA AND INTENSIVE CARE MEDICINE 10:4
Postoperatively: ongoing prevention or control of PONV and timely analgesic interventions are the main considerations, along with wound observation for bleeding and cerebrospinal fluid leakage. Surgery for congenital ear defects Anaesthetic considerations: congenital ear defects may be associated with Treacher Collins syndrome or Goldenhar syndrome, in which either the first or the second branchial arch derivatives 188
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Paediatrics
develop abnormally. These syndromes can pose difficulty with tracheal intubation (see pages 201–6, in this issue). The children present for single- or multi-stage reconstructive ear surgery, and for insertion of temporal screws to enable attachment of boneanchored hearing aids.
a nticipated degree of difficulty in maintaining an airway during anaesthesia, whether the patient can and/or should be intubated, and whether a spontaneously ventilating technique is required. Infective pathologies, such as laryngeal papillomatosis, require regularly repeated surgery, and past anaesthetic records are a valuable source of information. Obstructing airway pathologies in neonates and infants, such as congenital cysts or laryngo- or tracheomalacia, are extremely challenging to manage and justify critical care-level monitoring postoperatively.
Preoperatively: clarify the nature and components of the underlying syndromes. Focused evaluation of the affected organ systems should be based on syndrome components. Thorough evaluation of the airway is mandatory to evaluate potential difficulty with bag–valve–mask ventilation (severe mandibular hypoplasia can make this very difficult), laryngoscopy and LMA insertion. Review the previous anaesthetic records when available, and formulate airway management plans accordingly. Anticholinergic agents can be administered at this time to reduce airway secretions.
Intraoperatively: deaths resulting from the use of medical lasers have been associated with upper airway surgery, when the tracheal tube has been ignited. Since nitrous oxide is a better oxidizing agent than oxygen, an inspired oxygen concentration below 30% in nitrogen or helium is recommended. Laser-resistant tracheal tubes can be used, but are not available for very small infants. These are constructed of a flexible stainless-steel spiral, with twin distal cuffs that are filled with saline. Alternatively, conventional polyvinylchloride (PVC) tubes may be wrapped with adhesive metal tape. Oxygen insufflation without resorting to tracheal intubation can be useful to provide a clear view of an unobstructed glottis. For satisfactory insufflation technique, an adequate depth of anaesthesia is vital to avoid adverse events such as coughing, bucking and laryngospasm. Topical lidocaine sprayed on the cords is essential for the success of this technique. If the depth of anaesthesia is too great the patient may become apnoeic or develop cardiovascular instability. Careful titration of propofol and remifentanil infusions can be used for this procedure, although volatile anaesthetics have traditionally been used. Other standard laser precautions should be observed: the patient’s eyes should be taped shut and covered with moist gauze pads. Any exposed facial hair on the patient (e.g. eyebrows) should be coated with aqueous lubricating jelly to make it non-combustible. During lower airway surgery, the laser fibre tip should be kept in constant view, and should be activated only when clear of the bronchoscope or tracheal tube. Only the person using the laser should activate it; it should be placed in standby mode whenever it is not in active use. The operating theatre should be designated a ‘laser controlled area’ and warning signs placed at all entry points. While the laser is in use, windows should be covered and doors secured to prevent injury to passers by. All personnel in the theatre should wear appropriate eye protection.
Intraoperatively: anaesthesia for short operations can be maintained with a LMA, but the anaesthetist must have a plan for managing the airway in an emergency. In case of anticipated difficult intubation and for long operations involving ear reconstruction, endotracheal intubation should be the first choice for securing the airway. Lengthy operations require usual attention to fluid and electrolyte balance, glucose homeostasis, thermoregulation and pressure area care. Invasive arterial monitoring is appropriate. Postoperatively: ongoing management of pain, PONV if present and maintenance of fluid balance. Laser surgery of the larynx The laser (light amplification by stimulated emission of radiation) has been used in ENT surgery since the introduction of the carbon dioxide laser for laryngeal surgery. Table 4 shows the commonly used lasers for airway surgery. Anaesthetic considerations: the details of the airway pathology for which laser therapy is indicated must be appreciated. Laser safety protocols should be followed. Postoperative disposition should be planned. Preoperatively: the anatomical location of the lesion, degree of airway obstruction and its nature – fixed/dynamic/both – should be evaluated. This information will help determine the
Postoperatively: the location and level of postoperative care is determined by the patient’s age and pathology. Bleeding and oedema are typically minimal after laser surgery and obstructive symptoms often show immediate improvement. ◆
Characteristics of lasers used for airway surgery Laser medium
Colour
CO2 Nd:YAG KTP Argon
Far infrared Near infrared Green Blue/green
Wavelength (nm)
Tissue penetration (mm)
10,600 1064 532 488/515
< 0.25 2–6 0.5–2.0 0.5–2.0
References 1 Tait AR, Malviya S. Anesthesia for the child with an upper respiratory tract infection: still a dilemma? Anesth Analg 2005; 100: 59–65. 2 Lim J, McKean M. Adenotonsillectomy for obstructive sleep apnoea in children. Cochrane Database Syst Rev 2003 (Issue 1) Art. No. CD003136. 3 Mather SJ, Peutrell JM. Postoperative morphine requirements, nausea and vomiting following anaesthesia for tonsillectomy. Comparison of intravenous morphine and non-opioid analgesic techniques. Paediatr Anaesth 1995; 5: 185–8.
KTP, potassium titanyl phosphate; Nd:YAG, neodymium-doped yttrium aluminium garnet.
Table 4
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Paediatrics
7 Hullett BJ, Chambers NA, Pascoe EM, Johnson C. Tramadol vs morphine during adenotonsillectomy for obstructive sleep apnea in children. Paediatr Anaesth 2006; 16: 648–53. 8 Carr A. Guidelines on the prevention of postoperative vomiting in children. London: Association of Paediatric Anaesthetists of Great Britain & Ireland, 2008. 9 Crysdale WS, Russel D. Complications of tonsillectomy and adenoidectomy in 9409 children observed overnight. CMAJ 1986; 135: 1139–42.
4 Reiner SA, Sawyer WP, Clark KF, Wood MW. Safety of outpatient tonsillectomy and adenoidectomy. Otolaryngol Head Neck Surg 1990; 102: 161–8. 5 Parry M, Glaisyer HR, Bailey PM. Removal of LMA in children. Br J Anaesth 1997; 78: 337–8. 6 Cardwell M, Siviter G, Smith A. Non-steroidal anti-inflammatory drugs and perioperative bleeding in paediatric tonsillectomy. Cochrane Database Syst Rev 2005 (Issue 2) Art. No. CD003591.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 10:4
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Crown Copyright © 2009 Published by Elsevier Ltd. All rights reserved.
Anaesthesia for elective ear, nose and throat surgery in children
Preoperative assessment In addition to the standard components of a preoperative assessment (Anaesthesia and Intensive Care Medicine 2006; 7: 375–9), the following are particularly pertinent to paediatric ENT surgery: co-existing syndromes, recent upper respiratory tract infection (URTI), upper airway obstruction during sleep and bleeding diatheses. Any congenital, chromosomal or syndromic abnormalities should be specifically identified. Commonly encountered examples include children with Down’s syndrome, who often require middle ear surgery (which is more challenging as they have narrow external auditory canals) and adenotonsillectomy for obstructive sleep apnoea; patients with branchial arch abnormalities, who present for reconstructive ear surgery and may be extremely difficult to intubate; infants with cleft lips and/or palates, which may be isolated anomalies but may also be part of syndromes whose other features (particularly cardiac) may have an impact on the anaesthesia management. A history of active or recently resolved upper respiratory tract infection is commonly elicited in children scheduled for ENT surgery. Fitness for anaesthesia should be assessed on a case-bycase basis. Generally, a child with clear nasal secretions who is systemically well, with no associated fever or chest signs is considered fit for anaesthesia.1 A cough is a sign of increased airway irritability and portends an elevated risk of airway complications such as breath-holding, laryngospasm and desaturation. These risks are greater if the larynx is to be intubated or instrumented. Other risk factors for increased airway complications include nasal congestion, mucopurulent secretions and passive smoking. Children presenting for adenotonsillectomy typically experience varying degrees of upper airway obstruction (UAO) when sleeping. Preoperatively, a thorough assessment of the degree of obstruction should be obtained by history and examination (Table 1). The diagnosis is usually informal and subjective, based on parental reports of snoring, transient apnoeas, frequent nocturnal awakening and, in more severe cases, daytime somnolence or hyperactivity, behaviour problems and altered school performance. Most children will have histories consistent with only mild OSA. Examination may reveal obesity, adenoidal facies
Permendra Singh Simon Whyte
Abstract This review outlines anaesthetic considerations for commonly performed elective ear, nose and throat procedures, which constitute a major portion of the paediatric anaesthesia workload. Most routine surgery can be performed on a daycare basis, but careful preoperative assessment is vital to identify those patients who are unsuitable for daycare surgery owing to complications of their presenting illness (e.g. obstructive sleep apnoea; OSA) or other co-morbidities. Children undergoing middle ear surgery need special attention to prevent bleeding, hypothermia and postoperative nausea and vomiting (PONV). Adenotonsillectomy is most commonly performed to relieve the symptoms of OSA. The main anaesthetic concerns are analgesia, PONV, risk of postoperative haemorrhage and postoperative disposition. Daycare tonsillectomy involves careful patient selection and good communication with families regarding the postoperative phase and potential complications. Use of lasers is common in airway surgery; associated risks include airway fire and injury to the eyes of the patient and theatre staff.
Keywords adenotonsillectomy; daycare; elective; otolaryngology; paediatrics
Introduction Elective ear, nose and throat (ENT) surgery in American Society of Anesthsiology (ASA) stage 1 or 2 children takes place in almost every hospital. The anaesthetic challenges include appropriate selection of day-case patients, sharing the airway with the surgeon, managing postoperative nausea and vomiting (PONV) and patient and personnel safety issues surrounding the use of lasers.
Symptoms and signs suggestive of sleep-disordered breathing in children
Permendra Singh, MBBS, FRCA, is a Specialist Registrar in Anaesthesia. He obtained his medical degree from India and undertook his anaesthesia training in India and in the UK. He has completed a fellowship in paediatric anaesthesia at the British Columbia Children’s Hospital in Vancouver, Canada. Conflicting interests: none declared.
Daytime symptoms
Signs
Snoring
Daytime sleepiness
Obesity
Apnoea
Hyperactivity
Tonsillar hypertrophy
Arousals or wakening
Poor concentration
Mouth-breathing Failure to thrive
Enuresis
Simon Whyte, MBBS, FRCA, is a Paediatric Anaesthetist in Vancouver, Canada. He obtained his medical degree in 1994 from the University of Newcastle upon Tyne, and undertook his anaesthesia training in Durham, Middlesbrough and Liverpool. His research interests include perioperative long QT syndromes and advanced airway management in children. Conflicting interests: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 10:4
Night-time symptoms
Night sweats Difficult to rouse in the morning Table 1
186
Crown Copyright © 2009 Published by Elsevier Ltd. All rights reserved.
Paediatrics
to develop airway obstruction in the postoperative period, when the anaesthetic effects on upper airway tone and reflexes are still compromising the airway. The development of idiopathic pulmonary oedema following the relief of upper airway obstruction has also been reported. In severe OSA, the hypoxaemia and hypercarbia that result from the cyclical obstruction–hypoventilation– arousal sleep pattern in these children can produce a compensated respiratory acidosis and pulmonary hypertension. In end-stage disease, cor pulmonale and cardiac arrhythmias can result.
or obviously enlarged tonsils. A nasendoscopy may have detailed the degree of any adenoidal obstruction of the nasopharynx. Children with severe symptoms of OSA may have been assessed with overnight pulse oximetry, or formal polysomnography. Plans should be made preoperatively for children with OSA who have risk factors for postoperative complications (Table 2) to be monitored in a high-dependency setting for 24 hours postoperatively. A history of increased bruising or easy bleeding should be sought and investigated. Haemorrhage during or after adenotonsillectomy is an important complication (see below), whereas middle ear surgery can be rendered impossible by even small amounts of bleeding.
Anaesthetic considerations: presence and severity of sleepdisordered breathing; potentially difficult airway; potential pulmonary hypertension; ventilation strategy; analgesic strategy; PONV prophylaxis; postoperative disposition; postoperative bleeding.
Common ENT procedures Myringotomy and tympanostomy tubes Anaesthetic considerations: this is usually performed as a daycase procedure; therefore, emphasis should be on adequate pain relief and quick recovery.
Preoperatively: the anaesthetist should gain a sense of how bad the child’s airway obstruction is during sleep, as this will reflect the potential airway obstruction on induction of anaesthesia. In a minority of patients, objective information will be available, in the form of results from overnight pulse oximetry or formal polysomnography. In the vast majority, however, an impression is gained from the subjective observations of parents. Important signs and symptoms are detailed in Table 1. Other preoperative enquiries should aim at eliciting any history suggestive of bleeding diathesis, risk factors for PONV and active or recent tonsillitis (which is a risk factor for postoperative haemorrhage). Sedative premedication is relatively contraindicated in patients with OSA, as it may compound upper airway obstruction during or even before induction. Analgesics such as paracetamol or a NSAID such as ibuprofen may be given preoperatively to these patients.3 Postoperative disposition should be agreed upon preoperatively. Children chosen for daycare should have good overall medical health; no central or obstructive sleep apnoea; a normal bleeding history and profile; adequate social circumstances; and should preferably live near the hospital.4
Preoperatively: assess for active or recent URTI (common). Many children undergo repeated operations and may have increased anxiety around or specific preferences for induction of anaesthesia. Analgesia with oral paracetamol (acetaminophen) and/or a non-steroidal anti-inflammatory drug (NSAID) is appropriate. Intraoperatively: the airway can be maintained either with a face mask or laryngeal mask airway (LMA) while the patient breathes spontaneously. A dose of ondansetron 0.15 mg/kg may be given intravenously (i.v.) to minimize PONV. Postoperatively: analgesic requirements are highly variable between children. Some may occasionally require intravenous opioid. Adenotonsillectomy This common procedure is performed on a daycare basis in many hospitals. OSA is now the commonest indication for adenotonsillectomy in children, although good-quality evidence of its efficacy is lacking.2 Careful patient selection and preoperative assessment is vital to avoid complications. Children with OSA are more prone
Intraoperatively: induction may be by either the inhalational or the intravenous route, though induction with propofol might be preferred in cases where there is no obvious airway obstruction to reduce the incidence of PONV. Fentanyl in a dose of 1–2 μg/kg may be given to provide intraoperative analgesia. A preformed south-facing oral RAE (Ring, Adair and Elwyn) tracheal tube or a reinforced LMA may be used to maintain the airway. A LMA is useful in the recovery phase since it can be left in place until the patient’s reflexes return, whereas an endotracheal tube raises the dilemma of extubation at a deep plane of anaesthesia versus awake extubation.5 The pros and cons of using a LMA are listed in Table 3. Attention has to be given to careful insertion of the operative mouth gag in either technique, ensuring that the airway device remains unobstructed. After insertion of the gag a manual check for ease of lung inflation should be performed before surgery begins. Children with significant OSA may have a compensated respiratory acidosis as a result of nocturnal hypercarbia, although this is likely to be far less common than in adults with OSA. Ventilating such patients to normocapnia will delay restitution of spontaneous ventilation at the end of the procedure.
Risk factors for postoperative complications in children with obstructive sleep apnoea undergoing adenotonsillectomy • Age younger than 3 years • Cardiac complications of OSA • Failure to thrive • Obesity • Prematurity • Recent respiratory infection • Craniofacial anomalies • Neuromuscular disorders OSA, obstructive sleep apnoea.
Table 2
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Paediatrics
tonsillectomy site; continued presence of blood in the vomitus should prompt the surgeon to look for primary bleeding at the operative site. Length of stay: protracted emesis and primary haemorrhage have the greatest incidence in the first 6 hours after surgery. Duration of postoperative stay in the hospital can vary, depending on the individual patient and the surgeon. Parents should be given clear written and verbal guidelines regarding when and how to seek medical assistance postoperatively.
Advantages and disadvantages of airway maintenance with a laryngeal mask airway during tonsillectomy Advantages
Easy to insert Allows for lighter level of anaesthesia Smoother emergence without tracheal stimulation
Disadvantages
May retract cephalad in the pharynx and obstruct surgical view Does not protect against secretions entering the glottic opening
Middle ear surgery: mastoidectomy, myringoplasty and cochlear implantation Anaesthetic considerations: minimize bleeding; PONV prophylaxis; potentially long surgery with attendant risks of pressure injuries and hypothermia; difficult airway access; facial nerve monitoring.
Table 3
Preoperatively: assess for bleeding diatheses and risk factors for PONV.
Estimated total intravascular blood volume should be calculated for each child (neonates, 90 ml/kg; infants, 80 ml/kg; children, 70 ml/kg) and blood loss should be closely monitored. Isotonic intraoperative fluids should be given and the intra venous cannula kept in situ postoperatively in case of primary haemorrhage. Analgesic strategies for adenotonsillectomy are the subject of ongoing confusion and controversy. Concern has arisen over the use of NSAIDs because of their antiplatelet effect and the potential risk of increased bleeding. A Cochrane review of this issue concluded that there is no evidence that NSAIDs cause bleeding that increases the need to return to theatre and that, moreover, PONV is reduced when NSAIDs are used.6 Long-acting opioids also cause concern because they may contribute to ongoing airway obstruction postoperatively. It is assumed – without much evidence to support or refute it – that children with OSA will exhibit the same increased sensitivity to the central nervous system depressant effects of opioids seen in adults with OSA. For these reasons, long-acting opioid use should be minimized as far as possible in children undergoing adenotonsillectomy for upper airway obstruction. Tramadol may cause fewer episodes of postoperative desaturation than morphine.7
Intraoperatively: control of bleeding allows the surgeon to operate through the microscope in a bloodless field. Avoid hypertension and hypercarbia. Preservation of the facial nerve is attained by use of facial nerve monitoring and requires neuromuscular function. If neuromuscular block is needed to facilitate smooth intubation, choose a dose and an agent that ensures the return of function before the need for neuromuscular monitoring arises. Long duration of surgery means that hypothermia is a risk. Temperature monitoring and methods to prevent heat loss are recommended. Airway access is difficult during the surgery, demanding meticulous attention to securing airway devices and breathing circuit connections and to preventing disconnections. Dural breach is a possible complication during middle ear surgery that needs careful attention in the form of antibiotic cover and vigilant postoperative observation. Prevention of PONV: middle ear surgery is associated with a high risk of PONV. Single-agent prophylaxis with ondansetron 0.15 mg/kg is always indicated and dual therapy (dexamethasone 0.15 mg/kg and ondansetron 0.05 mg/kg) should be given if other risk factors are present.8 Other strategies to mitigate the risk include good hydration, the use of total intravenous anaesthesia and avoidance of long-acting opioids. Avoidance of graft displacement: when the middle ear has been closed by a myringoplasty, termination of N2O will result in negative middle ear pressure being applied to the graft. Avoiding the use of N2O or switching it off about 20 minutes before the ear is closed avoids the pressure on the newly applied graft.
Postoperatively: patients should be recovered on their side in a head-down position until fully awake. Fluids should be prescribed postoperatively for maintenance until the child has resumed drinking. Paracetamol and NSAIDs should be given regularly for postoperative pain, combined with codeine (if required) in patients with no or mild OSA. Persistent vomiting and poor oral intake are the most common causes of unscheduled overnight admission after daycare adenotonsillectomy. Intraoperative administration of i.v. ondansetron 0.05 mg/kg and dexamethasone 0.15 mg/kg are given to prevent PONV.8 If the child has postoperative vomiting despite antiemetic prophylaxis then maintenance intravenous fluid therapy should be continued and rescue antiemetics given from a different pharmacological class from those used for prophylaxis. Post-tonsillectomy haemorrhage can be life threatening. This affects about 1–2% of children in the first 24 hours, although only about 0.06% need general anaesthesia for haemostasis.9 Close watch should be kept for bleeding, dehydration and hypovolaemia. Vomiting can lead to exacerbation of bleeding from the
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Postoperatively: ongoing prevention or control of PONV and timely analgesic interventions are the main considerations, along with wound observation for bleeding and cerebrospinal fluid leakage. Surgery for congenital ear defects Anaesthetic considerations: congenital ear defects may be associated with Treacher Collins syndrome or Goldenhar syndrome, in which either the first or the second branchial arch derivatives 188
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Paediatrics
develop abnormally. These syndromes can pose difficulty with tracheal intubation (see pages 201–6, in this issue). The children present for single- or multi-stage reconstructive ear surgery, and for insertion of temporal screws to enable attachment of boneanchored hearing aids.
a nticipated degree of difficulty in maintaining an airway during anaesthesia, whether the patient can and/or should be intubated, and whether a spontaneously ventilating technique is required. Infective pathologies, such as laryngeal papillomatosis, require regularly repeated surgery, and past anaesthetic records are a valuable source of information. Obstructing airway pathologies in neonates and infants, such as congenital cysts or laryngo- or tracheomalacia, are extremely challenging to manage and justify critical care-level monitoring postoperatively.
Preoperatively: clarify the nature and components of the underlying syndromes. Focused evaluation of the affected organ systems should be based on syndrome components. Thorough evaluation of the airway is mandatory to evaluate potential difficulty with bag–valve–mask ventilation (severe mandibular hypoplasia can make this very difficult), laryngoscopy and LMA insertion. Review the previous anaesthetic records when available, and formulate airway management plans accordingly. Anticholinergic agents can be administered at this time to reduce airway secretions.
Intraoperatively: deaths resulting from the use of medical lasers have been associated with upper airway surgery, when the tracheal tube has been ignited. Since nitrous oxide is a better oxidizing agent than oxygen, an inspired oxygen concentration below 30% in nitrogen or helium is recommended. Laser-resistant tracheal tubes can be used, but are not available for very small infants. These are constructed of a flexible stainless-steel spiral, with twin distal cuffs that are filled with saline. Alternatively, conventional polyvinylchloride (PVC) tubes may be wrapped with adhesive metal tape. Oxygen insufflation without resorting to tracheal intubation can be useful to provide a clear view of an unobstructed glottis. For satisfactory insufflation technique, an adequate depth of anaesthesia is vital to avoid adverse events such as coughing, bucking and laryngospasm. Topical lidocaine sprayed on the cords is essential for the success of this technique. If the depth of anaesthesia is too great the patient may become apnoeic or develop cardiovascular instability. Careful titration of propofol and remifentanil infusions can be used for this procedure, although volatile anaesthetics have traditionally been used. Other standard laser precautions should be observed: the patient’s eyes should be taped shut and covered with moist gauze pads. Any exposed facial hair on the patient (e.g. eyebrows) should be coated with aqueous lubricating jelly to make it non-combustible. During lower airway surgery, the laser fibre tip should be kept in constant view, and should be activated only when clear of the bronchoscope or tracheal tube. Only the person using the laser should activate it; it should be placed in standby mode whenever it is not in active use. The operating theatre should be designated a ‘laser controlled area’ and warning signs placed at all entry points. While the laser is in use, windows should be covered and doors secured to prevent injury to passers by. All personnel in the theatre should wear appropriate eye protection.
Intraoperatively: anaesthesia for short operations can be maintained with a LMA, but the anaesthetist must have a plan for managing the airway in an emergency. In case of anticipated difficult intubation and for long operations involving ear reconstruction, endotracheal intubation should be the first choice for securing the airway. Lengthy operations require usual attention to fluid and electrolyte balance, glucose homeostasis, thermoregulation and pressure area care. Invasive arterial monitoring is appropriate. Postoperatively: ongoing management of pain, PONV if present and maintenance of fluid balance. Laser surgery of the larynx The laser (light amplification by stimulated emission of radiation) has been used in ENT surgery since the introduction of the carbon dioxide laser for laryngeal surgery. Table 4 shows the commonly used lasers for airway surgery. Anaesthetic considerations: the details of the airway pathology for which laser therapy is indicated must be appreciated. Laser safety protocols should be followed. Postoperative disposition should be planned. Preoperatively: the anatomical location of the lesion, degree of airway obstruction and its nature – fixed/dynamic/both – should be evaluated. This information will help determine the
Postoperatively: the location and level of postoperative care is determined by the patient’s age and pathology. Bleeding and oedema are typically minimal after laser surgery and obstructive symptoms often show immediate improvement. ◆
Characteristics of lasers used for airway surgery Laser medium
Colour
CO2 Nd:YAG KTP Argon
Far infrared Near infrared Green Blue/green
Wavelength (nm)
Tissue penetration (mm)
10,600 1064 532 488/515
< 0.25 2–6 0.5–2.0 0.5–2.0
References 1 Tait AR, Malviya S. Anesthesia for the child with an upper respiratory tract infection: still a dilemma? Anesth Analg 2005; 100: 59–65. 2 Lim J, McKean M. Adenotonsillectomy for obstructive sleep apnoea in children. Cochrane Database Syst Rev 2003 (Issue 1) Art. No. CD003136. 3 Mather SJ, Peutrell JM. Postoperative morphine requirements, nausea and vomiting following anaesthesia for tonsillectomy. Comparison of intravenous morphine and non-opioid analgesic techniques. Paediatr Anaesth 1995; 5: 185–8.
KTP, potassium titanyl phosphate; Nd:YAG, neodymium-doped yttrium aluminium garnet.
Table 4
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7 Hullett BJ, Chambers NA, Pascoe EM, Johnson C. Tramadol vs morphine during adenotonsillectomy for obstructive sleep apnea in children. Paediatr Anaesth 2006; 16: 648–53. 8 Carr A. Guidelines on the prevention of postoperative vomiting in children. London: Association of Paediatric Anaesthetists of Great Britain & Ireland, 2008. 9 Crysdale WS, Russel D. Complications of tonsillectomy and adenoidectomy in 9409 children observed overnight. CMAJ 1986; 135: 1139–42.
4 Reiner SA, Sawyer WP, Clark KF, Wood MW. Safety of outpatient tonsillectomy and adenoidectomy. Otolaryngol Head Neck Surg 1990; 102: 161–8. 5 Parry M, Glaisyer HR, Bailey PM. Removal of LMA in children. Br J Anaesth 1997; 78: 337–8. 6 Cardwell M, Siviter G, Smith A. Non-steroidal anti-inflammatory drugs and perioperative bleeding in paediatric tonsillectomy. Cochrane Database Syst Rev 2005 (Issue 2) Art. No. CD003591.
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