Discussion:
In this prospective observational study, we noted that the number of cases with AVB were higher in the months of November-December 2019. The common symptoms included rapid breathing, cough, and fever. The common findings at admission were tachypnea, chest retractions, respiratory failure, low SpO2, wheezing, and crepitations. RSV and rhinovirus are most commonly detected. The extra-pulmonary manifestations were described in 25% cases in form of encephalopathy, transaminitis, shock, AKI, myocarditis, MODS, and ARDS. More than 1/3rdcases needed PICU admission and common treatment included oxygen support (nasal prong oxygen, CPAP, of HFNC), mechanical ventilation, nebulization (3% saline, adrenaline, and salbutamol), vasoactive drugs, and steroids. One-third cases also received intravenous antibiotics. The mortality rate observed to be 8%.
The impact of AVB on the health of young children is huge and approximately 2-3% of infants require hospitalization due to AVB4. Characteristically, in a winter month a child presents with 2-4 days history of low-grade fever, rhinorrhea, nasal congestion; and symptoms of lower respiratory tract involvement (cough, tachypnea); increased respiratory effort (grunting, nasal flaring, and intercostal, subcostal, or supraclavicular retractions); and inspiratory crackles and expiratory wheezing on auscultation4,10.
Despite the high burden of disease, there is lack of effective treatment for AVB. None of the commonly practised modalities shown to shorten the disease course or hastens the resolution of symptoms of AVB leaving the clinicians to go for supportive therapy in form of heated humified oxygen, adequate hydration, and respiratory monitoring for improvement or worsening. With supportive treatment, majority of infants with AVB do well. The American Academy of Pediatrics published clinical practice guidelines based on Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system to standardize the diagnosis and management of AVB18. As per the guidelines, the suspicion of AVB should be based on the history and physical examination. There is no need of routine radiographic, laboratory studies, and viral testing. The supplemental oxygen is needed if oxyhemoglobin saturation (SpO2) falls below 90%. Intravenous or nasogastric fluids to be administered to maintain adequate hydration. Epinephrine, short-acting β2-agonists, systemic glucocorticoids, chest physiotherapy, and antibiotics are not recommended for the treatment of AVB. Nebulization with hypertonic saline may be used as it improves symptoms of mild-to-moderate AVB, if length of stay is >3 days18.
Due to tertiary care referral hospital, commonly the infants with severe illness are referred with respiratory failure, higher rates of extra-pulmonary complications (25%), more cases required PICU admission (36.4%), and mechanical ventilation (23%), vasoactive drugs (14%); and had higher mortality (8%).
PICU admission is needed in 15-25% of children with AVB. About 25-40% of those admitted to PICU require endotracheal intubation and mechanical ventilation which is associated with various complications including ventilator induced lung injury, infection, airway trauma, vocal cord dysfunction, need for prolonged sedation, and overall a financial burden to the family19-22. Various non-invasive modes of oxygen delivery are being increasingly used including CPAP, HFNC, non-invasive positive pressure ventilation (NPPV), and bilevel positive airway pressure (BiPAP) which may obviate the need for invasive mechanical ventilation and complications related to it23-27. The infants deteriorating on non-invasive modes of oxygen delivery required intubation and mechanical ventilation because of apnea, severe lower airway disease, or ARDS and usually need a shorter mechanical ventilation (<5 days)3, 28. Appropriate sedation and analgesia should be provided to infants with AVB. There is substantial variability in diagnosis and management of infants with AVB in different PICUs22.
In index study, 36.4% cases needed PICU admission. Underlying comorbidity; presence of chest retractions, respiratory failure, and lower oxygen saturation at admission; presence of shock; and need of mechanical ventilation were independent predictors of PICU admission on multivariate analysis.
In AVB, the use of antibiotics does not lead to change in course or outcome and are not routinely recommended4,18. Despite these facts, antibiotics has been used in AVB inappropriately. Papenburg et al29 noted that about 25% infants with AVB were given antibiotics, 70% of them had no documented bacterial co-infection, and 38% received macrolides. Therefore, efforts are needed to reduce inappropriate and unnecessary use of antibiotics in AVB.
With the availability of molecular techniques, it has been possible to identify viruses causing AVB. The most common viruses identified are RSV (50-80%), rhinovirus (5-25%), PIV (5-25%), hMPV (5-10%), coronavirus (5-10%), adenovirus (5-10%), and influenza (1-5%)4,11,30,31. The proportion of virus causing AVB differ according to geographical location and time of the year. The clinical features of AVB caused by different viruses are generally indistinguishable. However, it has been noted that AVB caused by rhinovirus may be less severe and associated with shorter duration of hospitalization than RSV4,32. Also, there are not much differences in response to medical treatment among infants with AVB caused by different viruses4. The reported rates of co-infection varied widely among different studies ranging from 6% to more than 30%4,32,33. Few studies noted greater severity of disease, longer hospital stay, more severe hypoxemia, and greater risk of relapse in children with co-infection32,34,35; whereas, other studies showed no difference on disease severity and outcome in those with co-infection33,36-38. In index study, atleast one virus was isolated in 74% cases with RSV and rhinovirus as commonest. One-fifth cases had co-infection with >1 virus. However, isolation of virus or co-infection was not associated with any differences in clinical features, complications, treatment, PICU needs, and outcome.
The strengths of this study include prospective study with large sample size. All the enrolled cases underwent viral testing which is important to determine etiology but did not have much significance in determining disease severity, prognosis, and short-term outcome. The details of treatment, intensive care needs, and outcome has been described. The predictors of PICU admission were determined. The limitations included single centre study and lack of long-term follow-up.