Obstructive retrosternal goitre mimicking severe bronchial asthma in pregnancy

Abstract

Acute airway obstruction in pregnancy remains a challenge to manage. Failure of appropriate and timely airway management may lead to maternal morbidity and mortality such as aspiration pneumonitis or worst hypoxaemic cardiopulmonary arrest. ¹ As pregnancy may exacerbate asthma attacks, parturient presenting with wheezing or shortness of breath will commonly be treated as suffering from an asthmatic attack. ² However, it is important to note other possible differential diagnoses. Thyroid disease is relatively common in women of childbearing age. The thyroid gland undergoes several changes during pregnancy, which may lead to altered function as well as gland enlargement and cause upper airway obstruction and symptoms similar to a bronchial asthma attack. ^{3 4} With that in mind, we report a case of a parturient with long-standing goitre in her second trimester who presented to our institution with acute respiratory symptoms and cardiopulmonary arrest.

Background

This case report highlights the management challenges encountered in a parturient presenting with upper airway obstruction secondary to a retrosternal goitre, which is a rare entity, with only one previously published case report. It also serves to remind that not all women of childbearing age who presents with shortness of breath are due to a bronchial asthma attack. This is also the first reported case in which acute hypoparathyroidism occurred after thyroidectomy in pregnancy.

Case presentation

A 32-year-old parturient presented in her second trimester with a history of goitre and a 2-week history of cough. Her medical history was significant for a benign goitre, which was diagnosed 3 years ago, and bronchial asthma, which was diagnosed during her second pregnancy 3 years back. Salbutamol inhaler was prescribed then, and her asthmatic condition improved after delivery. She was gravida three with two living children. For the presenting complaint, she was treated with oral antibiotics by a nearby health clinic for presumed pneumonia, but her symptoms worsened. She developed shortness of breath with audible wheeze and was admitted to a nearby hospital. She was treated as having an acute exacerbation of bronchial asthma secondary to pneumonia. Systemic and inhaled corticosteroids, as well as bronchodilators, were initiated along with intravenous antibiotics.

Her care was transferred to our medical centre. On arrival at our emergency department (ED), she was unable to speak in full sentences and very tachypnoeic. Clinically, audible wheeze was heard with low saturation of 70%, and she was cyanosed before the cardiopulmonary arrest. A cycle of cardiopulmonary resuscitation was performed, followed by intubation of the trachea with an endotracheal tube (ETT). Examination of her chest postintubation revealed symmetrical chest expansion and occasional rhonchi with equal air entry was heard on auscultation. A diffusely enlarged thyroid gland was palpated measuring around 8 cm, which was more prominent on the left side (figure 1). There was no bruit on auscultation. Initial chest radiograph showed bilateral perihilar consolidative changes with the presence of air bronchograms, obscuring the mediastinum with normal cardiac silhouette suggestive of pneumonia (figure 2). Her initial full blood count revealed a white cell count of 20 300/µL with neutrophil-predominance suggestive of bacterial infection. Her thyroid function test showed subclinical hyperthyroidism (free thyroxine, 14.55 pmol/L; thyroid-stimulating hormone, 0.04 uIU/mL). Rest of her other blood investigations were unremarkable. Diagnosis of acute exacerbation of bronchial asthma secondary to community-acquired pneumonia was reaffirmed.

Figure 1.

Lateral view of the neck preoperatively, showing compressive goitre (arrow).

Figure 2.

Chest radiograph in anteroposterior view showing bilateral perihilar consolidative changes with the presence of air bronchogram.

In the intensive care unit (ICU), she responded well to the inhaled bronchodilators, systemic and inhaled corticosteroids, and antibiotics. Weaning from mechanical ventilation started on the third day of ventilation. However, with reduced sedation and more frequent triggered spontaneous supported breaths generated, the ICU team noticed that she frequently had bronchospasms with rhonchi heard on auscultation. There was also prolonged expiratory phases with variable expired tidal volumes seen and carbon dioxide retention observed on the arterial blood gases. These episodes improved with increased sedation, and without the need for bronchodilators. CT of the neck and thorax was performed to exclude upper airway obstruction. The CT scan of the neck and thorax showed extensive consolidation of the left lung suggestive of an infective aetiology, as well as a heterogeneously enlarged left thyroid lobe with retrosternal extension 3.6 cm below the manubrium sternum. It was compressing the trachea, with the narrowest diameter of trachea measuring 0.4 cmx1.8 cm and the compression was extending distal to the endotracheal tube (figures 3 and 4).

Figure 3.

CT thorax on lung window axial view showing extensive consolidation of the left lung suggestive of an infective aetiology.

Figure 4.

CT thorax on soft tissue axial view showing mass effect of retrosternal goitre on the trachea, with the narrowest diameter of trachea measured 0.4 cmx1.8 cm which was distal to the endotracheal tube.

She was subsequently nursed in lateral positions that resulted in decrease tracheal compression with improvements in ventilator parameters. Improvements of expired tidal volumes were seen with fewer bronchospasm episodes were evident. The carbon dioxide retention resolved as well. After 5 days of mechanical ventilation, a repeat chest radiograph performed showed significant improvement of the perihilar consolidative changes. Despite this, the ICU team encountered difficulties in weaning as she was still unable to be nursed in the supine position. In addition, with the reduced sedation rate, variable expired tidal volumes continued to be observed with prolonged expiratory phases. Thus, the ICU team concluded that external compression of the trachea was present beyond the ETT close to the carina.

After a multidisciplinary team meeting followed by a family conference with the patient’s husband, we proceeded with a total thyroidectomy performed by the endocrine surgical team and direct laryngoscopy with rigid bronchoscopy examination by the otorhinolaryngologist. Direct laryngoscopy with rigid bronchoscopy examination showed anterior–posterior long segment narrowing of the upper airway secondary to external compression (figure 5). Intraoperative findings revealed cystic multinodular goitre with a haemorrhagic cyst, extending retrosternally causing compression of the trachea. Bilateral recurrent laryngeal nerves were identified and preserved with the aid of a nerve monitoring device. A repeated direct laryngoscopy with rigid bronchoscopy examination immediately after thyroidectomy showed resolution of the tracheal narrowing. There is no evidence of laryngomalacia (figure 6). The total thyroidectomy specimen weighed 129 g, and the histopathology report showed thyroid nodular hyperplasia with no evidence of malignancy (figure 7). A haemorrhagic parathyroid gland was included as well.

Figure 5.

Fibre-optic endoscopic view showing significant external anterior compression causing narrowing of the of the thoracic trachea (#) beyond the endotracheal tube tip (*).

Figure 6.

Direct telescopic view after total thyroidectomy. The narrowing of the cervical and thoracic trachea is no longer visualised. Some mucosal changes are seen secondary to prolong endotracheal intubation.

Figure 7.

Gross specimen of the resected thyroid gland showing a large retrosternal component.

Outcome and follow-up

Postoperatively in ICU, sedation was weaned, there was no recurrence of bronchospasms and airway obstruction episodes. She was extubated successfully the very next day without any airway complications. In the early postoperative period, the patient developed persistent hypocalcaemia, which required multiple doses of intravenous calcium gluconate. She was transferred out to general ward following stable levels of serum calcium. There was no hoarseness of voice. A fetal detail scan performed by a feto-maternal consultant showed no abnormalities. She was safely discharged home with oral calcium carbonate, calcitriol and thyroid hormone supplementation. During her subsequent follow-up at the combined obstetric and surgical clinic, her serum calcium and thyroid function remain stable within normal ranges. She safely delivered a healthy baby girl weighing 2.62 kg at 38 weeks.

DISCUSSION

Acute airway obstruction in pregnancy remains a challenge to manage. Failure of appropriate and timely airway management may lead to maternal morbidity and mortality such as aspiration pneumonitis or even hypoxaemic cardiopulmonary arrest.¹ As bronchial asthma has an incidence of 3%–12% among parturient, presentations with wheezing is likely to be diagnosed as an asthma attack.⁴ In our case report, the patient presented acutely with strong clinical evidence of an asthma attack; therefore, she was treated as such. Despite instituting initial standard therapy for acute exacerbation of bronchial asthma in ED, her presenting clinical presentation persisted and led to witnessed hypoxaemic cardiopulmonary arrest. It was immediately attended to with cardiopulmonary resuscitation and intubation of the trachea with an ETT without any difficulty. Thus, severe life-threatening asthma was diagnosed.

The thyroid gland undergoes several changes during pregnancy, which may lead to altered function as well as gland enlargement.³ Iodine loss in pregnancy is increased as a result of increased glomerular filtration rate during pregnancy.⁵ Therefore, thyroid gland size may increase by 20%–30% during pregnancy.⁶ Occasionally, it may cause tracheal compression symptoms; however, it very rarely causes life-threatening airway compression requiring surgical decompression.⁷ In our case report, there was clinical evidence of an anterior neck swelling on presentation. About 3 months prior to conceiving, she sought medical attention for the goitre. As she was euthyroid and without compressive symptoms, she opted for not to be operated at that point when the surgeon suggested it. Subsequently, at antenatal follow-up, issues were not raised regarding the goitre. With this history and as there were no problems encountered during endotracheal intubation, airway compression from the goitre was not considered as a differential diagnosis initially.

Radiological imaging may identify the cause for the sudden increase in the thyroid gland. Ultrasonography of the thyroid gland may help to assess the size of the goitre, characterise the thyroid nodules as well as to look for suspicious features.⁴ However, it poorly detects the degree of tracheal stenosis or the retrosternal component. Ultrasonography of the thyroid was done for our patient which showed an enlarged heterogeneous thyroid gland measuring 4.0 cm x 8.3cm x 6.3 cm with a possible retrosternal component. Following the ultrasound of the goitre with changes observed from the ventilator, we suspected an upper airway compression from the retrosternal goitre. A large goitre usually follows a progressive course of enlargement, with multitudes of symptoms. However, they may also present acutely with acute respiratory distress. As she presented with acute upper airway symptoms, we suspected a sudden enlargement of her thyroid gland due to a respiratory tract infection.⁵ However, an acute bleed into a cyst in multinodular goitre or malignancy could not be ruled out.

Subsequently, CT scan of the neck and thorax was done to identify the retrosternal extension of the thyroid gland and to detect the presence of tracheal stenosis. Because of her difficult ventilation caused by frequent acute changes to her measured ventilation parameters, we opted not to proceed with MRI despite knowingly it is safer for the fetus. CT of the neck and thorax delivers a radiation dose of <0.1 rad to the fetus. As a shield was applied, the radiation dose would be <1% of the maximal allowed dose to which the fetus can be exposed.⁷ Consent from her husband detailing the risk of CT scan to the fetus was taken. Informed consent for the imaging to be done was taken from her husband.

In stable patients, flow volume loop examination would be able to assess upper airway obstruction. As it is a dynamic study, it will provide quantitative information concerning the air flow both during inspiration and expiration. It is also able to quantify the severity of the tracheal stenosis.⁷ The suspicion of tracheal compression was raised when flow volume loops were observed on the ventilator graphics by the ICU team showed variable expired volume. However, because of our patient’s situation, we proceeded with a more definitive approach by direct laryngoscopy and rigid bronchoscopy examination to assess the degree of tracheal compression and to look for evidence of upper airway oedema. This is because pregnancy-related changes may cause capillary engorgement and oedema of the mucosa throughout the respiratory tract, further compromising her airway.¹ We also elected to perform a second look bronchoscopy before closing the thyroidectomy wound. Tracheostomy was avoided as there was no evidence of tracheomalacia. As there was no significant upper airway oedema, we were able to extubate her the following morning after the surgery.

Thyroid surgery is always indicated when patients present with severe airway compression secondary to goitre.⁸ Thyroid surgery in parturient carries a higher risk of endocrinological and general complications compared with a non-parturient. In a cross-sectional study performed on over 201 parturient who underwent thyroid and parathyroid surgeries, the fetal and maternal complications were 5.5% and 4.5%, respectively.⁶ There are only a handful of case reports where thyroidectomy was performed in a parturient who had airway compromise. Hypoparathyroidism associated with pregnancy is extremely rare and is usually the result of the previous thyroidectomy.⁷ In our patient, she developed significant hypocalcaemia in the postoperative period likely due to transient acute hypoparathyroidism. This is possibly due to vascular compromise to the parathyroid glands.⁹ Transient hypoparathyroidism occurs in 6.9% to 46% of thyroidectomies.⁹ This is the first reported case in which acute hypoparathyroidism occurred after thyroidectomy in pregnancy. Timely management with calcium and calcitriol supplementation prevented further complications from hypocalcaemia. As in our case, most cases of retrosternal goitre can be successfully removed without resorting to a midline sternotomy.⁸ Despite an initial delay in arriving at the diagnosis, our patient had a good outcome due to effective planning following detection. Successful communication among clinicians of a multidisciplinary team allowed for the development of a detailed plan before surgery.

In conclusion, acute airway obstruction in the setting of pregnancy is a rare and unique dilemma, both at arriving at the diagnosis and its subsequent management. Goitre causing an upper airway obstruction should be a differential diagnosis of parturient presenting with dyspnoea and wheezing. This case illustrated that even an asymptomatic euthyroid goitre of moderate size in parturient might cause acute airway obstruction and catastrophic outcomes to both mother and fetus if inadequately managed. A multidisciplinary approach and timely surgery were critical to the successful management of this patient.

Patient’s perspective.

When I was in the intensive care unit (ICU), I could not remember much, but I was told by my husband that I was sedated and treated while the doctors looked for the cause of my breathing difficulty. My husband informed me that the ICU team looked after me very well. The doctors were very concerned about me, and they are competent in doing the job to keep me safe. I am happy that the surgery went smoothly as after the surgery, I was informed by my husband regarding the potential complications that may arise. I am grateful that my baby is safe.

In conclusion, I am thankful as this medical centre has many experienced and responsible doctors and nurses. They really care about my health not just in the hospital but even until now. Thank you very much to all the doctors and nurses involved.

Learning points.

• Acute airway obstruction in the setting of pregnancy is a rare and unique dilemma, both at arriving at the diagnosis and its subsequent management.

• Goitre causing an upper airway obstruction should be a differential diagnosis of parturient presenting with dyspnoea and wheezing.

• Direct visualisation of the airway determines the severity of airway compromise and the need for definitive airway management.

• Thyroid surgery is always indicated when patients present with severe airway compression secondary to goitre, but it carries a higher risk of complications in the parturient. A multidisciplinary approach and timely surgery are critical to the successful management of similar cases.