Benign multinodular goitre presenting as acute decompensated type two respiratory failure

Abstract

Acute airway obstruction is a life-threatening complication of benign goitre mostly occurring in cases of known progressing goitres. The index presentation of goitre with decompensated type two respiratory failure is an exceedingly rare and a diagnostically challenging presentation. We discuss the case of a woman in her 50 s, who had been diagnosed with asthma by her general practitioner, but during admission was found to have a large goitre with retrosternal extension causing critical tracheal compression. She presented with acute decompensated type two respiratory failure. We explore the diagnostic confounding posed by the patient’s background of asthma and describe the initial management of the patient with non-invasive ventilation by the emergency department. The diagnosis of upper airway obstruction was not apparent which is an interesting anomaly in this case. She underwent an emergency hemithyroidectomy and recovered with a resolution of her respiratory symptoms. Histology confirmed benign multinodular hyperplasia.

Background

Goitre is a relatively common diagnosis in the community with benign multinodular goitre being one of the most common pathologies. It is frequently asymptomatic and identified in a euthyroid patient presenting with a neck mass.

Benign goitres commonly cause chronic upper airway obstruction although this is often latent. A UK study looking at patients with symptomatic goitre with various aetiologies identified a 31% incidence of upper airway obstruction using flow-volume loops (n=144).¹ Patients were enrolled to this study from a single endocrine outpatient clinic and did not present acutely. It is far less common for benign goitres to present with acute airway obstruction. The incidence of such presentations is not well documented although studies estimate this to be around 0.6–1.3% with a notable predilection for female patients although this may reflect increased baseline incidence of goitre in women.^{2 3} Presentation of goitre with decompensated type two respiratory failure (T2RF) is even rarer with only a few cases reported in the literature including reports by Bakkar et al and Bayhan et al.^{4 5}

In most of these cases the patient had a prior diagnosis of goitre before presenting with respiratory failure. In this case report we describe a challenging case in which the initial presentation of benign multinodular goitre was decompensated T2RF.

Case presentation

A woman in her 50s presented to the emergency department with a 2-day history of worsening shortness of breath associated with a mild non-productive cough. The shortness of breath was minimally relieved by her salbutamol inhaler at home.

She had no smoking history but had a background of asthma diagnosed a few years ago in the community for which she was using a regular steroid inhaler. She described her asthma as mostly being triggered by changes in the weather. She experienced no prior hospitalisations for asthma but had noticed her breathing symptoms slowly worsening over the past few years despite inhaler therapy.

Medical history was significant for hypertension, spina bifida and associated hydrocephalus with a ventriculoperitoneal shunt in situ. The patient was mostly a wheelchair user although could mobilise a limited number of steps. Medication history included a buprenorphine patch for chronic pain.

On examination, she was speaking with incomplete sentences, was tachypnoeic and appeared unwell. The chest was quite on auscultation with a few scattered rhonchi.

Investigations

On presentation, the vital signs were: SpO2 85% on room air, blood pressure 209/101 mm Hg, heart rate of 95 beats per minute and she was afebrile. Her arterial gas on an FO2 of 28% showed acute decompensated T2RF with a pH of 7.19, pCO2 of 12.8 kPa and HCO3 of 27.8 mmol/L.

ECG showed sinus tachycardia. The chest X-ray interpretation was limited by poor inspiration and rotation (figure 1). There were some ill-defined opacifications in both lungs but no obvious focal pathology. Liat Covid and influenza A/B testing were negative.

Figure 1.

Admission portable chest X-ray.

She was managed in the emergency department as an exacerbation of asthma with back-to-back nebulisers and intravenous magnesium and steroid. She was deemed stable enough for a BiPap (bilevel positive airway pressure ventiallation) trial with resources available for immediate intubation if required. Serial arterial blood gas tests over the next few hours demonstrated sequential improvement with near resolution of respiratory failure. Within 6.5 hours, she was weaned off BiPap and transitioned to 2 L oxygen via nasal canulae.

As the patient had presented at 02:00, it was not until the subsequent morning that she was reviewed by the specialist respiratory team. At this point, she had been weaned off BiPap and mild inspiratory stridor was apparent on this review. The stridor was positional and improved in lateral position. A close neck examination demonstrated a goitre and she was clinically euthyroid. The patient described hearing these breathing noises intermittently during the past few months.

She underwent urgent CT imaging which demonstrated clear lung parenchyma but significant thyromegaly with retrosternal extension causing compression of the trachea to a length of approximately 2 cm below the level of the vocal cords (figure 2). The tracheal lumen was slit-like measuring only 2–3 mm.

Figure 2.

CT of the neck and thorax axial and sagittal views.

Treatment

An urgent anaesthetic review of the airway identified her as stable and not fulfilling the criteria for emergency intubation. Bedside fibreoptic bronchoscopy identified normal cord function and no other intra-tracheal pathology. Tracheostomy was deemed not feasible given the length of the narrow segment extending almost to the clavicle. She was transferred to ITU (intensive therapy unit) for monitoring while surgical consultation and planning were underway. Prednisolone (from her asthma management) was escalated to dexamethasone and nebulised epinephrine was added.

The next morning she underwent uncomplicated emergency right-extended hemithyroidectomy using awake fibre optic intubation. The following day, she underwent a dynamic airway assessment which identified no complications such as tracheomalacia and she was extubated. This was followed by an uneventful postoperative recovery. Histology identified features of multinodular thyroid hyperplasia with no evidence of malignancy.

Outcome and follow-up

At 2 months follow-up the patient had recovered well and reported complete resolution of her breathing symptoms. She no longer required any inhaler therapy following hemithyroidectomy. Ultrasound at 6 months showed no residual tissue in the right thyroid bed and normal appearances of the left thyroid lobe.

Pulmonary function testing at 3 months follow-up showed no airflow limitation and a normal vital capacity. The patient had not undergone any previous testing for comparison.

Discussion

The incidence of goitre causing acute airway obstruction is not defined. A Hong Kong study identified an incidence of 0.6% for acute upper airway obstruction in patients with benign nodular goitre undergoing thyroid surgery (n=1115).² All patients were elderly women and required emergency airway interventions. Başoğlu et al report 1.3% of patients with benign multinodular goitre undergoing thyroid surgery at their centre required emergent airway management for airway obstruction (n=993).³ 11 out of 13 cases were women.

Presentation of goitre with decompensated T2RF is even rarer. A few cases have been reported in the literature but in the majority of these cases there was a prior diagnosis of goitre before the patients presented with respiratory failure.⁴ In some cases where goitre caused acute T2RF there was a clear precipitant such as cardiac bypass surgery.⁶

The differential of acute decompensated T2RF is broad. In the assessment of respiratory distress, stridor is a key sign that directs the physician to the upper airway. It is noteworthy that, in similarity to our case, other published cases in which goitre caused T2RF also do not mention stridor in the clinical presentation.^4–6 This suggests a potentially dangerous pattern in which airflow limitation to critical levels causing hypercapnia may result in inaudible airway noises analogous to the scenario in which a non-wheezing silent chest can be mistaken for improved airflow in a hypercapnic asthmatic patient.

Retrosternal extension is a common mechanism and is likely a result of the limited retrosternal space precipitating tracheal obstruction. This observation suggests that goitre in cases of critical respiratory distress may not be as readily appreciable on the examination. In addition, opioids such as the buprenorphine patch that can depress ventilation may have contributed to this patient presenting with acute decompensated T2RF.

However, the pathophysiology of acute airway obstruction in a patient with goitre may involve multiple mechanisms including acute bleeding, tracheal mucosal oedema and secretion retention.⁷ This may be secondary to direct tracheal compression from the goitre or as a result of intercurrent acute viral upper respiratory tract viral infection that leads to decompensation in an already obstructed airway. This pathophysiology provides further rational for adjuvant treatment with corticosteroids and nebulised epinephrine. Moreover, malacia of the upper airway structures can lead to dynamic airway compromise. Tracheomalacia, although poorly understood, is hypothesised to be more common in longstanding goitres and can present with post-thyroidectomy airway obstruction although in our patient postoperative dynamic airway testing showed no evidence of this.⁸

There are no specific guidelines for the emergency perioperative management of the airway in cases of compressive goitre despite how non-straightforward these situations can be. Tracheostomy may be limited by the length of the compressed trachea. Although our patient was initially monitored in the ITU, the decision was made that intubation in the ITU should be avoided if possible and that the theatre was the safest location. This was partly because the CT imaging could not safely identify any extent of haemorrhage associated with the goitre.

BiPap is usually not indicated in fixed upper airway obstruction as although it may theoretically improve ventilation, the clinical priority is to establish a structurally safe airway. As in the case reported by Bakkar et al, our experience demonstrated BiPap ventilation, under close observation, as a possible temporising adjunct in the perioperative management of these patients, especially in out-of-hours presentations when the necessary complex theatre team may not be readily available.⁴

Learning points.

• Although they more commonly present with chronic respiratory symptoms, obstructive upper airway pathologies including goitre should be considered in the differential of acute decompensated type two respiratory failure (T2RF).

• Differentiating between life-threatening reactive airway disease and critical upper airway obstruction is challenging, especially in a patient with a silent chest. The clinical finding of stridor may be the only differentiating factor although it can be inaudible in critical airflow limitation or a fatiguing patient.

• This highlights the importance of physical upper airway examination including the thyroid and trachea in patients presenting with T2RF especially those without a history of chronic lung disease or those with an equivocal lung auscultation.

• The emergency management of the airway in these patients is not straightforward when theatre is not available immediately. Tracheostomy and out-of-theatre intubation may not be safe.

• Non-invasive ventilation, although not routinely indicated in fixed upper airway obstruction, may have a role as a short-term temporising adjunct.

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