|Year : 2019 | Volume
| Issue : 4 | Page : 312-315
Anaesthetic management of an infant with tracheomalacia scheduled for computed tomography angiography: A challenge
Manpreet Kaur, Sana Y Hussain
Department of Anaesthesiology, Pain Medicine and Critical Care, All India Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||4-Apr-2019|
Dr. Manpreet Kaur
Department of Anaesthesiology, Pain Medicine and Critical Care, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
Tracheomalacia is characterised by collapse of the tracheal wall with respiration. Computed tomography angiography (CTA) can be utilised for evaluation of airway abnormalities but providing sedation/anaesthesia for CTA in such a case carries the risk of airway catastrophe. We describe the anaesthetic management of an infant who had tracheomalacia with >90% collapse in lower two third of the intrathoracic trachea as diagnosed on videobronchoscpy and was scheduled for CTA.
Keywords: Airway, bronchomalacia, CT angiography, general anaesthesia, sedation, tracheomalacia
|How to cite this article:|
Kaur M, Hussain SY. Anaesthetic management of an infant with tracheomalacia scheduled for computed tomography angiography: A challenge. Indian J Anaesth 2019;63:312-5
|How to cite this URL:|
Kaur M, Hussain SY. Anaesthetic management of an infant with tracheomalacia scheduled for computed tomography angiography: A challenge. Indian J Anaesth [serial online] 2019 [cited 2020 Apr 1];63:312-5. Available from: http://www.ijaweb.org/text.asp?2019/63/4/312/255468
| Introduction|| |
Tracheomalacia is defined as dynamic reduction in luminal diameter or cross-sectional area by 50% during expiration., It is characterised by an abnormally compliant trachea with dynamic collapse during the respiratory cycle or when coughing. It has an incidence of 1:2100 children. Primary tracheomalacia is due to impaired maturation or deficient cartilaginous rings and/or decreased tone of the trachealis muscle and is frequently associated with comorbidities, such as craniofacial abnormalities, tracheo-oesophageal fistula, etc. Secondary tracheomalacia is due to localised compression of the normal tracheal cartilage by vessel, mass, infection, or prolonged tracheostomy. Computed tomography angiography (CTA) is utilised for simultaneous evaluation of mediastinal, vascular, lung, and airway abnormalities. Administering sedation/anaesthesia for CTA in such a patient has potential risk of airway catastrophe. We describe the anaesthetic management of an infant with tracheomalacia with >90% collapse of the lower two third of the intrathoracic trachea, who was scheduled for CTA.
| Case History|| |
A 1-year-old boy [7.5 kg, 76 cm] with congenital tracheomalacia was scheduled for CTA. Child was breast fed and his perinatal period was uneventful. At the age of 1 month, he developed sudden bluish discoloration of the body associated with crying, which recurred a month later. Symptoms became worse with bronchodilator nebulisation. Child had a history of recurrent lower respiratory tract infection (LRTI) which resolved with intravenous antibiotics and steroids. He never required mechanical ventilation. He was on regular follow up for noisy breathing, cough, LRTI, and blue spells. His preferential sleep posture was supine with no associated noisy breathing. On auscultation, he had no adventitious sounds when quiet but added sounds were heard when he cried. Chest radiograph revealed mediastinal widening (probably due to enlarged thymus) and left-sided airway opacities [Figure 1]a and [Figure 1]b. Videobronchoscopy revealed trachea collapsing >90% in lower two third with expiration, left main bronchus collapsing with expiration. Echocardiography showed left atrial enlargement. Cardiac and neurological evaluations for apnoeic spells revealed no abnormality. All standard monitors were applied including electrocardiogram, pulse oximeter, blood pressure, and end-tidal CO2. His vital signs were: heart rate 140/min; blood pressure 76/40 mm Hg, respiratory rate 22/min, and saturation 99% on room air. Paediatric difficult airway cart with all adjuvants and alternatives to laryngoscopy and supraglottic airway devices was kept ready. Plan A was to maintain spontaneous ventilation during anaesthesia and plan B or the backup plan was to intubate the trachea with 4 mm or smaller endotracheal tube [as tracheal stent] using Propofol (2–3 mg/kg) and Atracurium (0.5 mg/kg) followed by controlled ventilation. The child was administered 0.07 mg of glycopyrrolate, 0.5 mg of midazolam, and 8 of ketamine intravenously. A top up dose of 2 mg of ketamine was administered. Supplemental oxygen was administered using a face mask at a rate of 4 L/min. The procedure lasted for 10 min. Intraoperative vitals remained stable. There was no airway obstruction or oxygen desaturation and the saturation remained between 97% and 99%. No other complications occurred during or after the procedure. CTA revealed brachiocephalic trunk abutting midtrachea at T2/T3 level [Figure 2].
|Figure 1: (a) Chest radiograph showing mediastinal widening. (b) Videobronchoscopy showing trachea collapsing >90% in lower two third with expiration, left main bronchus collapsing with expiration|
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|Figure 2: CTA showing brachiocephalic trunk abutting mid trachea at T2/T3 level (right anterior compression of the trachea)|
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| Discussion|| |
Diagnosing tracheomalacia is very difficult due to a broad spectrum of nonspecific respiratory complaints, such as harsh chronic cough, central wheeze, dyspnoea, gasping, stridor, feeding difficulties, blue spells, and recurrent respiratory tract infection. The patient had noisy breathing, cough, LRTI, and blue spells. High intrathoracic pressures during crying can result in airway collapse in a child with tracheomalacia which is otherwise prevented by normal rigid tracheal cartilage. Excessive airway collapse can result in impaired ability to expel secretions and hence recurrent respiratory infections as in the index patient. Middle and distal tracheal segment tracheomalacia is associated with an expiratory noise, especially with intrathoracic obstruction. The patient had no adventitious sound on lying at rest but had expiratory noise on crying. Intrathoracic tracheal lumen is determined by difference between intrathoracic and intraluminal airway pressures. Thus, the tracheal lumen dilates during inspiration and narrows during expiration in a spontaneously breathing patient. As the transmural pressure across the airway wall (intraluminal–pleural) was low during quiet breathing, there were no abnormal breath sounds at rest. However, crying resulted in marked increase in pleural and led to noisy breathing. The elevated intraalveolar pressure ultimately would serve to reduce tracheal collapse as intraluminal pressure would be higher in the trachea, barring a more distal obstruction.
Bronchoscopy is gold standard for rapidly diagnosing dynamic airway changes during all respiratory phases. It was done in our patient a few weeks back in a paediatric bronchoscopy suite using 0.5 mg of midazolam IV. Prediction of airway dynamics by laryngobronchoscopy (LB) does not correlate with the severity of malacia. This is because LB is done in a spontaneously breathing patient without muscle relaxation or positive pressure ventilation which reduces the degree of malacia. On the other hand, general anaesthesia with instruments suspending tongue and epiglottis makes real dynamic view impossible. (1) Thus, it is important to have neither over- nor undersedation present when assessing a patient for dynamic central area collapse, as it could affect the findings. Oversedation would underestimate, while under sedation would overestimate the presence of malacia in the of absence of simultaneous measurement of transmural pressures. Thus, LB has low sensitivity (46.1%) and positive predictive value (42.9%) for compressive tracheomalacia as it is difficult to assess an extrinsic pathology while evaluating from inside the airway. Arterial lumen is determined by pulsatility but tracheobronchial tree collapsibility is determined by phases of respiration. As the beating vessel had minor variation in the lumen, a persistent airway collapse was observed in the index patient. Hence, it is difficult to ascertain the presence of an external compression in patients with collapsible airway.
Both rigid and flexible bronchoscopy require sedation. Inadequate sedation induces vigorous respiratory efforts, some narrowing of intrathoracic trachea on forced expiration, and overestimates the severity of tracheomalacia. While heavy sedation may jeopardise the safety. This would necessitate positive pressure ventilation and mask the tracheomalacia by limiting the extent of dynamic collapse. The collapse from tracheomalacia can be decreased with positive pressure ventilation due to reduced gradient between the intrathoracic and intratracheal pressures (decreased transmural pressure). As symptomatic tracheobronchomalacia can result in airway obstruction during general anaesthesia, we opted for mild sedation without suppressing spontaneous ventilation. Besides, the duration of CTA is short. With deep sedation and on induction of general anaesthesia, the airway can become obstructed wherein an endotracheal tube with controlled ventilation is needed to keep the airway patent which was our Plan B. The gradient between the intrathoracic and intratracheal pressures is reduced with positive pressure ventilation making the tracheal collapse less likely. Continuous positive airway pressure (CPAP) and intermittent positive pressure ventilation provides distending pressure preventing airway to close during exhalation and thus improves respiratory mechanics. Thus, CPAP decreases expiratory resistance by opening the tracheal lumen, improves the expiratory flow, and increases the lung volumes. Our goal was to avoid tracheal manipulation during anaesthesia and maintain adequate spontaneous respiration. Hence, we chose ketamine as it maintains tone of tracheobronchial tree, has limited effects on ventilatory function, and procedure was of short duration. Dexmedetomidine infusion has been used in a few case reports but has a potential for haemodynamic compromise if used as a sole agent. We also did not have an infusion pump in computed tomography suite. Another important aspect is that inhalational induction with sevoflurane may be risky as sevoflurane has bronchodilator effect and can potentially make airway more collapsible. Neuromuscular blockers have to be used judiciously as they can relieve airway collapse in tracheomalacia but can worsen the mechanical obstruction like mediastinal mass or foreign body. Extubation is even more challenging and trachea should be left intubated after the intrapleural–intratracheal pressure relationship has normalised.
To conclude, it is important to understand the subtle airway dynamics in tracheomalacia to avoid airway catastrophe. Careful selection and titration of drugs is important during short diagnostic procedures as both oversedation and undersedation can not only compromise safety but also lead to underestimation and overestimation of malacia, respectively.
Consent for publication
Written Informed consent for publication was obtained from the child's guardians.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]