The stridulous infant
Respiratory distress in infants and small children is very common, particularly over the winter months, and is typically mild and self-limiting. A very small minority will need escalation to critical care support, however, when respiratory decompensation occurs and may be alarmingly rapid, needing urgent institution of ventilatory therapy. Many of these children will present to GPs or EDs with what appears to be non-specific malaise or upper respiratory tract symptoms, and identifying those with clinical features which may suggest significant pathology is often challenging.
1 Identify the signs and symptoms suggestive of impending respiratory failure
2 Have an awareness of the underlying pathologies
3 Outline a management plan for the stridulous infant
4 Prepare for emergency anaesthesia of the stridulous infant.
1C01; 2D01
An 18-month-old female infant presents to the ED in your district general hospital. She has a 2-day history of general non-specific malaise, has been pyrexial, and has not been feeding well. Her mother has brought her into the ED, as her breathing has become noisy, and she appears to be coughing and struggling for breath at times. She is previously well. You have been called down to review her from an airway and breathing perspective, as the ED doctor is concerned she may need anaesthetic support.
Severe airway or respiratory pathologies can often be detected on a focussed primary ABC survey, without going into detailed examination and investigation. This will allow prompt escalation and activation of senior and theatre support where necessary.
◆ A—airway: before starting to examine the patient, you may be struck by the noisy breathing from the end of the bed. Key elements to elicit are the respiratory phase, i.e. inspiratory or expiratory. Inspiratory noises can either be stertor or stridor; expiratory noises may be grunting or wheeze
• Stertor: is generated due to turbulent airflow through the supraglottic airway, typically due to partial obstruction from a hypotonic oropharynx, generally sounding like snoring. This is generally exclusively an inspiratory noise seen during sleep, which may be resolved by simple manoeuvres, like head and neck positioning, or, in extreme cases, with oropharyngeal or nasopharyngeal airways. Stertor in the awake patient is suggestive of significant upper airway obstruction
• Stridor: this should be considered an airway ‘red flag’ until proven otherwise. All practising anaesthetists will be most familiar with the high-pitched inspiratory noise of laryngospasm triggered due to an inadequate depth of anaesthesia. This inspiratory sound is triggered by high-velocity airflow through an airway narrowing between the glottis and the carina. There may be some expiratory component to the noise if the obstruction is severe. Irrespective of the aetiology, any infant with stridor requires an immediate anaesthetic assessment, with consideration for escalation to critical care
• Grunting: this end-expiratory noise is a compensatory mechanism for respiratory compromise, in which the patient partially closes their glottis during inspiration, effectively generating resistance to expiration and hence an intrinsic PEEP (sometimes referred to as auto-PEEP). This is a feature of failure of gas exchange, where either hypoxia or hypercarbia are stimulating the ventilatory drive, and can often be overcome by providing a small amount of external CPAP
• Wheeze: is not usually audible without a stethoscope but, if so, suggests a severe lower airway obstruction, with marked restriction to expiration. Patients have supranormal levels of intrinsic PEEP, and the RR will have a prolonged expiratory phase in order to facilitate an adequate carbon dioxide clearance.
Other assessment points in the airway examination include excluding the presence of foreign bodies, secretions, or blood, and identifying congenital abnormalities which may impact the airway patency, e.g. Pierre–Robin sequence, mucopolysaccharidoses, or cleft palate. Whilst these disorders may not immediately compromise the airway in isolation, in combination with any additional insult, e.g. a mild viral URTI, they may result in airway obstruction.
◆ B—breathing: similarly, a focussed primary breathing assessment may be performed from the end of the bed, prior to direct auscultation with a stethoscope. Key points to identify include:
• Rate: the RR varies with age and the concurrent state of the child. The RR in a newborn is around 40–60/min but may be 70–80/min when the child is upset. At 12–18 months, the normal RR will be 25–30/min, decreasing to 15–20/min for primary school-aged children and to adult values by teenage years. More important than the absolute rate itself is the trend over time, and many units use early warning charts to document the trends which give vital information on the progression. In response to an inadequate gas exchange, the RR will steadily increase, up to rates of 60–70 breaths/min which can only be sustained for a relatively short period of time, and will subsequently rapidly fall to hypopnoea, promptly followed by apnoea. Always determine that any fall in the RR is accompanied by a clinical improvement, as, if not, external ventilatory support is likely to be required urgently
• Work of breathing: an all-encompassing term that includes the presence of any, or all, of tracheal tug, intercostal indrawing, asymmetrical chest movement, subcostal recession, and abdominal paradoxical (see-saw) respiration. The presence of any of these clinical features is a compensatory mechanism to increase the negative intrathoracic pressure and increase the minute ventilation, as a result of an airway obstruction or an inadequate gas exchange due to pulmonary pathology. There is no single feature that is of more concern than the others, but rather the increasing magnitude of each and the presence of multiple signs point towards a marked increase in the work of breathing, which will often be accompanied by an increased RR, this situation being unsustainable in the longer term without external support.
Chest palpation and auscultation and pulse oximetry are obviously part of the respiratory assessment but may yield little additional information, particularly if the child is crying or moving around, where oximetry also often fails to provide accurate data.
◆ C—circulation: a full examination of the cardiovascular system is essential in the management of any unwell infant, but, for the purposes of a rapid assessment of the child with a compromised respiratory function, it is unlikely to add further to the diagnostic process or planning management. Key points to detect on the primary survey are peripheral perfusion, usually measured by the CRT, with a refill time >2 s indicating an inadequate perfusion and >5 s indicating severe hypoperfusion. Similarly, the patient’s colour will gave a rapid indication of the general physiological state, with a pink child indicating an adequate perfusion and oxygenation, cyanosis indicating hypoxia, but usually in the presence of an adequate cardiac output (mostly related to congenital cyanotic heart disease), and a pale or mottled child indicating a critical problem with oxygenation and perfusion
◆ D—disability/neurology: assessing a formal GCS in an unwell infant is challenging and often inaccurate. Most reliable is to perform a neurological assessment on an AVPU scale:
• A: alert approximates to GCS 14–15
• V: response to a verbal stimulus is GCS 12–13
• P: response to a painful stimulus is GCS 9–11
• U: unconscious is GCS 8 or less.
You assess your patient in the ED. Your primary ABCD survey demonstrates that she has a loud inspiratory stridor and is drooling at the mouth. Her RR is 40–50 breaths/min, and she has a markedly increased work of breathing, signified by tracheal tug, intercostal indrawing, and abdominal paradoxical respiration. She appears peripherally warm and is flushed. She is slightly drowsy at times but is quite miserable and gets upset when you try to approach her and examine her. The nurses cannot get any monitoring on her and do not want to upset her with further attempts.
This patient has stridor with severe respiratory distress. Irrespective of the aetiology, this is a potentially life-threatening situation which requires a consultant review and may require high-risk emergency anaesthesia. The differential diagnosis for an upper airway obstruction includes:
◆ Foreign body: this should be a differential for any child (or adult) presenting with an acute airway obstruction. Often the history of foreign body ingestion will be absent in children, as it often occurs when they are unsupervised or playing with siblings. Features which suggest this diagnosis include an abrupt onset in an otherwise well child with no other symptoms. Any form of a viral prodrome is usually absent, although it cannot be excluded in the child who may have ingested a foreign body whilst having a concurrent URTI
◆ Croup: this is the commonest cause of an upper airway obstruction in children aged between 1 and 2 years. Also known as laryngotracheobronchitis, it is a viral infection causing inflammation of the upper airways, most often caused by parainfluenza viruses but may also be caused by other respiratory viruses such as adenovirus, respiratory syncytial virus (RSV), and influenza A. Key features in the presentation include a viral prodrome for 24–48 hours and the classical ‘barking cough’, though the patients are usually not systemically unwell otherwise
◆ Epiglottitis: this is the classical red alert condition which presents with an acute airway obstruction in stridulous infants which are systemically toxic. Patients are often drooling at the mouth, due to odynophagia. These patients are often quiet and prefer to be in the sitting position. Any attempt to lie the patient down for examination usually exacerbates the airway obstruction. The incidence of epiglottitis has significantly decreased over the last 10 years, as children are now routinely vaccinated against the causative agent Haemophilus influenzae. However, due to adverse publicity related to other vaccination schedules, some parents choose to withhold all vaccines from their children, and, as such, bacterial epiglottitis must remain on a differential diagnosis list
◆ Tracheitis: bacterial tracheitis can be considered the intermediate pathology between croup and epiglottitis. Patients usually present with the systemic features of bacterial infection, including pyrexia, tachycardia, and hypotension, and with the airway manifestations of croup such as the barking cough and stridor. Drooling may, or may not, be present. These patients can deteriorate rapidly if the airway obstruction reaches a critical stage
◆ Lower respiratory pathology: any severe lower respiratory pathology in an infant may compromise gas exchange, such that an increased work of breathing is present, which, on occasion, may be associated with a mild inspiratory stridor, due to high-velocity airflow through a relatively narrow airway. In this age group, common pathologies include viral pneumonias, which may be particularly severe, requiring prolonged ventilation, and caused by adenovirus, influenza (including H1N1), parainfluenza, and RSV. Bacterial pneumonia or congenital abnormalities, such as cysts, may also present in this age group.
After examination, you suspect your patient has croup, bacterial tracheitis, or epiglottitis. The patient’s increased work of breathing and stridor persist. You are concerned that she looks like she is becoming exhausted and may need invasive respiratory support. Your consultant will attend shortly, and, in the interim, you need to outline a management plan.
This patient will be managed based on the progress of the clinical condition and response to interventions. It is unlikely that any specific investigation will influence management in the acute situation; however, they may direct subsequent intensive care management.
◆ Blood tests: FBC or biochemistry will not affect how the patient’s airway is managed. They will likely be required once the acute situation has been stabilized, but it would be generally inadvisable to embark upon blood sampling at this stage. Blood gases may inform the stage of respiratory decompensation, but careful consideration must be given to this. Arterial sampling is not likely to be possible, and, whilst venous or capillary sampling is used routinely in paediatric and neonatal care, the sampling procedure is likely to cause great distress which may also exacerbate airway compromise. If these samples are taken, they provide no information on the oxygenation state of the patient but give a reasonable indication of the carbon dioxide retention and acid–base status
◆ Radiology: similarly, the acute airway management is unlikely to be immediately influenced by chest radiograph imaging; however, it may be useful to detect a severe pneumonia or pneumothorax (which may result from a ruptured congenital cyst), prior to intubation. Plain film imaging purely for airway assessment is unhelpful, though, if performed for other reasons, it may be possible to denote the ‘steeple sign’ of a narrowed upper airway in croup or a swollen epiglottis on a lateral neck film
◆ Microbiology: samples from nasal swabs, respiratory secretions, and blood cultures will inform on appropriate antimicrobial therapies and the duration of treatment. Taking any of these samples in the awake child with a compromised airway will exacerbate the problem and should be deferred until the airway is secured.
This patient needs to be managed in an operating theatre by a consultant anaesthetist, ideally one with recent paediatric experience, if available. Where resources allow, this patient’s anaesthesia would ideally be performed by at least two anaesthetists. The full theatre team, including the operating department practitioner and theatre nurses, must be present. Due consideration to alerting an ENT surgeon should be given, and, where a local service exists for an ENT surgeon with paediatric experience, they should be requested to be present for the induction of anaesthesia in severe cases. Anecdotes exist of ENT surgeons from tertiary paediatric units attending a district general hospital in an emergency manner for airway support, though this is very dependent on local resources. The receiving PICU should be notified as early as possible, as the patient will need retrieval to the ICU, once the airway has been secured.
The full range of anaesthetic equipment for anaesthetizing an 18-month-old child must be present, as per AAGBI recommendations. Emergency drugs should be prepared in advance, including atropine and adrenaline; boluses of fluid and agents to maintain anaesthesia and muscle relaxation, once the airway has been secured, must be immediately to hand. A selection of laryngoscope blades and tracheal tubes should be selected by the operator. It is inappropriate to suggest that one profile of laryngoscope blade is superior to another for this situation, but the most important factor is that the intubating anaesthetist has familiarity with the blade selected. A MacIntosh blade may be perfectly suitable, there being no obligation to use a straight blade in this or any other paediatric patient. If an ENT surgeon is available, a paediatric tracheostomy tray will be required in theatre. The utility of fibreoptic scopes is likely to be limited in a small airway with inflammation, secretions, or other abnormality, but more anaesthetists would be comfortable using this in a difficult airway situation as a rescue device, so it is reasonable to have one on standby. The external diameter of a paediatric bronchoscope limits the tracheal tube size that can be used, with the following approximate guidelines:
◆ A 2.2 mm scope: no suction channel, minimum tracheal tube internal diameter (ID) 3.0 mm
◆ A 2.8 mm scope: no suction channel, minimum tracheal tube ID 4.0 mm
◆ A 4 mm scope: usually with suction ports, minimum tracheal tube ID 5.0 mm.
This infant’s respiratory function has deteriorated, with impending respiratory exhaustion, intermittent apnoeas, decreasing stridor (a sign of reduced airflow), and drowsiness. You have transferred the patient to theatre, still sitting on her mother’s lap, and a full theatre team and an adult ENT surgeon have been requested and will attend urgently. The PICU retrieval team are mobilizing but will take 90 min till arrival in your unit.
Whilst awaiting the arrival of the full theatre team and senior anaesthetic and ENT support, you may consider some non-invasive therapies before progressing to anaesthesia and intubation.
◆ Oxygen: at all times, there should be attempts to provide supplemental oxygen to this patient. This should be delivered at high flow, without fear of respiratory depression from carbon dioxide retention. A careful balance must be achieved between attempting to deliver oxygen and upsetting the patient further, and hence increasing their oxygen demand. Ideally, a reservoir bag–mask, held in the vicinity of the patient’s mouth and nose, often by the mother, will provide some oxygen supplementation. If the patient is sleeping or drowsy, it may be possible to apply the mask and/or nasal cannulae without disturbing the patient. Wherever possible, avoid manually ventilating the patient with a bag–valve–mask, as, in the situation of a partially occluded airway, most of this ventilated gas is likely to enter the stomach and subsequently impede diaphragmatic excursion
◆ Adrenaline: adrenaline nebulizers are a very effective treatment for croup, typically delivered as 5 mg of adrenaline in 5 mL of saline via standard nebulizers. This often results in a prompt resolution of croup-related stridor; however, the effect is often short-lived, and this may need repeating. More than 3–4 nebulizers over 1–2 hours suggest progressive disease that may require invasive support
◆ Bronchodilators: agents, such as salbutamol or ipratropium, are likely to have little effect on upper airway obstruction.
◆ Steroids: this is the mainstay of management in croup and usually results in the resolution of symptoms within 6 hours, which may avoid the need for intubation if adrenaline nebulizers are delivered in the interim period. The specific agent and route is unimportant, as long as a corticosteroid is administered early in the patient’s admission. This may be oral prednisolone, IV or oral dexamethasone, or IV hydrocortisone. The combination of early steroids and adrenaline nebulizers mitigates the need for intubation in around 98% of patients with croup
◆ Antibiotics: often at this stage in the management, the differentiation between a bacterial or viral aetiology has not been completed, and it is appropriate to cover all patients who show signs of sepsis with airway obstruction with antibiotics. These are best delivered intravenously; however, the same caveats apply in that the airway should not be risked purely for the purposes of IV cannulation for the administration of antibiotics. A third-generation cephalosporin, usually ceftriaxone, will provide adequate cover for Haemophilus influenzae and for the common pathogens for bacterial tracheitis, typically Gram-positive cocci.
An infant with a compromised stridulous airway will typically receive an inhalational induction of anaesthesia. There is growing experience using propofol TIVA for small children with airway obstructions, the benefits including a sustained delivery of anaesthetic and a rapid titratability and reversibility, even when the airway is compromised; however, this technique should be reserved for experts practising regularly with TIVA in children. Inhalational induction will be performed in the operating theatre, with the surgical team scrubbed in the event that an emergency surgical airway is required—there are few anaesthetists who possess up-to-date skills in performing surgical airways in children. Questions that are often raised include the following.
IV access should be established at a time when this will cause minimal upset to the child. It may be that, early in the admission, a topical local anaesthetic, such as Emla®, can be applied, and cannulation can be performed in the awake patient by a skilled operator. Often concerns that this will cause undue upset defers cannulation attempts, till the patient is anaesthetized, but this should be a priority once the induction has started, and attempts to secure the airway must not be performed without IV access. In the event of a severe deterioration on induction in a patient with poor venous access, an immediate deferral to intraosseus access should occur.
If the patient is maintaining an airway, whilst sitting on the mother’s lap or similar, one should consider commencing the inhalational induction in this position. Attempts to separate the child from her mother or position on an operating table are likely to cause upset and exacerbate the airway occlusion. Oxygen and sevoflurane can be gently introduced into the atmosphere around the patient’s face, by a cupped hand or breathing circuit without a face mask, progressing to the application of the mask, and taking the child from the mother as the induction progresses. A full explanation of details to the parent and a briefing of the primary plan and backup plan to the theatre team must be explicit before commencing induction.
Once an adequate depth of anaesthesia has been achieved, IV access obtained, and full monitoring established, laryngoscopy should proceed by the most experienced anaesthetist present. Adjuncts, such as a bougie, may be required, and significant downsizing of the tracheal tube should be anticipated, even when the larynx appears normal, in the case of bacterial tracheitis or tracheal stenosis. Once the airway is secured, the patient should have anaesthesia maintained, muscle relaxation, and preparation for transfer to the regional PICU.
Summary
Management of the stridulous infant is challenging for any anaesthetic team, and a high risk of patient harm exists if these cases are managed without meticulous preparation. Early recognition of a significant respiratory compromise and an impending ventilatory failure is vital, triggering a team response to prepare the necessary anaesthetic equipment and requesting support from additional staff from surgery and anaesthetics. Any interventions must be carefully balanced against worsening the airway compromise, with the ultimate aim of securing a safe airway prior to patient transfer.