Prolonged postoperative desaturation in a child with Down syndrome and atrial septal defect.

We report prolonged desaturation in a child with Down syndrome (DS) and atrial septal defect due to undiagnosed interstitial lung disease. An 18-month-old child with DS was scheduled for bilateral lens aspiration for cataract. The child had atrial septal defect and hypothyroidism. He also had delayed milestones and hypotonia with episodes of recurrent respiratory tract infection necessitating repeated hospitalization. Preoperative evaluation was unremarkable. General anaesthesia and controlled ventilation using proseal laryngeal mask airway was instituted. He had uneventful intraoperative period. In the postoperative period, the child had desaturation 1 hour after surgery on discontinuation of oxygen supplementation by face mask, which improved with oxygen therapy. Supplemental oxygen via face mask was continued and weaned off over several days. On further evaluation, the child was diagnosed as having interstitial lung disease. He improved and discharged from the hospital 15 days after the surgery with room air saturation of 90%.

INTRODUCTION

Down syndrome (DS) is the commonest congenital abnormality. Anaesthesia in DS carries a higher risk due to mental retardation, hypothyroidism, cardiao-respiratory, airway abnormalities and postoperative pulmonary complications.[1] Though subpleural cysts are common with lung hypoplasia, interstitial lung disease (ILD) is not a common entity in DS.[2] ILD is characterized by impaired gas exchange and diffuse infiltrates by imaging.[3] We report a case of prolonged postoperative desaturation in a child with DS due to undiagnosed ILD.

CASE REPORT

An 18-month-old, 7 kg, male child with Down syndrome was scheduled for bilateral lens aspiration. Comorbidities included atrial-septal defect (ASD), hypothyroidism, delayed milestones and hypotonia with episodes of recurrent respiratory tract infection (RTI) necessitating repeated hospitalization. Preoperatively, he had no signs and symptoms of RTI and congestive cardiac failure (CHF) with heart rate of 90/min and respiratory rate of 20/min. Chest radiograph revealed cardiomegaly with normal lung fields. Echocardiography (ECHO) showed ostium secundum and sinus venosus types of ASD with increased pulmonary blood flow, volume overloaded right ventricle and normal biventricular function.

The child was premedicated with oral promethazine and intravenous access was established after application of eutectic mixture of local anaesthetics (EMLA) cream. In the operating room, electrogardiogram leads and non-invasive blood pressure were applied. Room air oxygen saturation (SpO2) was not recorded due to constant movement of the child. Anaesthesia was induced with fentanyl 2 mg/kg and thiopentone sodium 5 mg/kg. Oxygen saturation was 98% with 100% oxygen. After achieving muscle paralysis with atracurium 0.5 mg/kg, proseal laryngeal mask airway (PLMA) 1.5 was inserted. Paracetamol suppositories 250 mg and topical 2% lignocaine gel was administered. Anaesthesia was maintained with O2, air (FiO2 – 0.5) and sevoflurane (MAC 0.8). Intraoperative SpO2 was between 97% and 99%. The duration of surgery was 40 minutes. Ringer lactate was administered accordingly. At the end of surgery, after reversal of neuromuscular blockade, PLMA was removed when the child became awake and shifted to recovery room for oxygen supplementation by face mask and monitoring.

After 1 hour, the child desaturated (SpO2 - 70%) on discontinuation of oxygen supplementation which improved with oxygen supplementation via face mask. Respiratory obstruction and CHF was ruled out as there was no tachycardia, tachypnea, hypotension, or hypercarbia. Next day, due to high-grade fever (101°F), with the suspicion of bronchiolitis, antibiotics (IV Cefotaxim) were started empirically and further management (salbutamol nebulization, steam inhalation, oxygen supplementation) was done in paediatric ward. A high-resolution computed tomography (HRCT) chest revealed features of ILD [Figure 1]. Oxygen therapy by face mask was gradually weaned off over 12 days (room air SpO2 - 90%) and the child was discharged after 15 days.

Figure 1

HRCT chest. Axial CT sections (a and b) of thorax in lung window showing scattered areas of ground glass attenuation involving both upper and lower lobes with areas of air trapping (arrow)

Children with DS are predisposed to recurrent RTI due to relative immune deficiency, chronic aspiration and presence of congenital heart disease (CHD).[4] Incidences of airway obstruction, stridor and postoperative atelectasis are also significantly higher especially in the presence of preoperative RTI.[1] Postoperative fever in our patient could be due to preoperative subclinical RTI.

There is always a controversy regarding selection of endotracheal tube and supraglottic air device in children with recent or recurrent RTI with varied results. Tait et al. compared laryngeal mask airway (LMA)

with endotracheal tube (ETT) in children with upper respiratory tract infection (URTI) and suggested that LMA is equally acceptable regarding airway complications perioperatively.[5] Von Ungern et al. showed higher incidence of laryngospasm, desaturation and cough with the use of LMA in children with recent URTI compared to healthy children.[6]

We preferred PLMA over ETT to reduce intubation and extubation response as our child had ASD. In our experience, PLMA in children with recurrent RTI did not increase airway complications in comparison to ETT.

Yamaki et al. found alveolar hypoplasia, overdistension of air spaces, interstitial emphysema and alveolar septitis as principal factors for postoperative respiratory failure in DS.[7] The smaller alveolar surface area with loss of capillary surface area may aggravate pre-existing pulmonary hypertension. In our patient, ASD and increased pulmonary blood flow lead to back pressure changes and interstitial thickening with the development of pulmonary pathology. ILD may be seen in children with chronic chest infection and aspiration.[8] Recurrent RTI in our patient might have predisposed the development of ILD.

ILD in children comprises a large and heterogeneous group of disorders characterized by diffuse infiltrates, restrictive functional defect with defective gas exchange.[9] Paediatric ILD has been associated with high morbidity and mortality with poor outcome in infants and young children.[3]

Pulmonary hypertension is the single greatest predictor of mortality in children with ILD.[3] Histological patterns of paediatric ILD differs from the adult one. Correlation between clinical, radiological and pathological finding is required for definitive classification and prognosis.[3]

Chest radiograph usually has characteristic reticulo-nodular or honey comb pattern, but it may be normal despite clinical impairment as was in our patient. HRCT chest is better and describes the extent and distribution of the disease. In the present case association of ILD as the principal cause of low saturation was confirmed only after HRCT.

In the present case, though ILD caused low SpO2, the severity and prolonged desaturation was also contributed by atelectasis after general anaesthesia and fever. If preoperative low room air saturation would have been recorded in this case, it would have definitely prompted us to investigate further.

In conclusion, in the present case prolonged postoperative desaturation occurred due to undiagnosed ILD. In the DS patient, recording of preoperative room air saturation may help to have suspicion of ILD.