Nebulised hypertonic saline solution for acute bronchiolitis in infants.

Background: Airway oedema (swelling) and mucus plugging are the principal pathological features in infants with acute viral bronchiolitis. Nebulised hypertonic saline solution (≥ 3%) may reduce these pathological changes and decrease airway obstruction. This is an update of a review first published in 2008, and updated in 2010, 2013, and 2017.

Objectives: To assess the effects of nebulised hypertonic (≥ 3%) saline solution in infants with acute bronchiolitis.

Search Methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, MEDLINE Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE Daily, Embase, CINAHL, LILACS, and Web of Science on 13 January 2022. We also searched the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) and ClinicalTrials.gov on 13 January 2022.

Selection Criteria: We included randomised controlled trials (RCTs) and quasi-RCTs using nebulised hypertonic saline alone or in conjunction with bronchodilators as an active intervention and nebulised 0.9% saline or standard treatment as a comparator in children under 24 months with acute bronchiolitis. The primary outcome for inpatient trials was length of hospital stay, and the primary outcome for outpatients or emergency department (ED) trials was rate of hospitalisation.

Data Collection And Analysis: Two review authors independently performed study selection, data extraction, and assessment of risk of bias in included studies. We conducted random-effects model meta-analyses using Review Manager 5. We used mean difference (MD), risk ratio (RR), and their 95% confidence intervals (CI) as effect size metrics.

Main Results: We included six new trials (N = 1010) in this update, bringing the total number of included trials to 34, involving 5205 infants with acute bronchiolitis, of whom 2727 infants received hypertonic saline. Eleven trials await classification due to insufficient data for eligibility assessment. All included trials were randomised, parallel-group, controlled trials, of which 30 were double-blinded. Twelve trials were conducted in Asia, five in North America, one in South America, seven in Europe, and nine in Mediterranean and Middle East regions. The concentration of hypertonic saline was defined as 3% in all but six trials, in which 5% to 7% saline was used. Nine trials had no funding, and five trials were funded by sources from government or academic agencies. The remaining 20 trials did not provide funding sources. Hospitalised infants treated with nebulised hypertonic saline may have a shorter mean length of hospital stay compared to those treated with nebulised normal (0.9%) saline or standard care (mean difference (MD) -0.40 days, 95% confidence interval (CI) -0.69 to -0.11; 21 trials, 2479 infants; low-certainty evidence). Infants who received hypertonic saline may also have lower postinhalation clinical scores than infants who received normal saline in the first three days of treatment (day 1: MD -0.64, 95% CI -1.08 to -0.21; 10 trials (1 outpatient, 1 ED, 8 inpatient trials), 893 infants; day 2: MD -1.07, 95% CI -1.60 to -0.53; 10 trials (1 outpatient, 1 ED, 8 inpatient trials), 907 infants; day 3: MD -0.89, 95% CI -1.44 to -0.34; 10 trials (1 outpatient, 9 inpatient trials), 785 infants; low-certainty evidence). Nebulised hypertonic saline may reduce the risk of hospitalisation by 13% compared with nebulised normal saline amongst infants who were outpatients and those treated in the ED (risk ratio (RR) 0.87, 95% CI 0.78 to 0.97; 8 trials, 1760 infants; low-certainty evidence). However, hypertonic saline may not reduce the risk of readmission to hospital up to 28 days after discharge (RR 0.83, 95% CI 0.55 to 1.25; 6 trials, 1084 infants; low-certainty evidence). We are uncertain whether infants who received hypertonic saline have a lower number of days to resolution of wheezing compared to those who received normal saline (MD -1.16 days, 95% CI -1.43 to -0.89; 2 trials, 205 infants; very low-certainty evidence), cough (MD -0.87 days, 95% CI -1.31 to -0.44; 3 trials, 363 infants; very low-certainty evidence), and pulmonary moist crackles (MD -1.30 days, 95% CI -2.28 to -0.32; 2 trials, 205 infants; very low-certainty evidence). Twenty-seven trials presented safety data: 14 trials (1624 infants; 767 treated with hypertonic saline, of which 735 (96%) co-administered with bronchodilators) did not report any adverse events, and 13 trials (2792 infants; 1479 treated with hypertonic saline, of which 416 (28%) co-administered with bronchodilators and 1063 (72%) hypertonic saline alone) reported at least one adverse event such as worsening cough, agitation, bronchospasm, bradycardia, desaturation, vomiting and diarrhoea, most of which were mild and resolved spontaneously (low-certainty evidence).

Authors' Conclusions: Nebulised hypertonic saline may modestly reduce length of stay amongst infants hospitalised with acute bronchiolitis and may slightly improve clinical severity score. Treatment with nebulised hypertonic saline may also reduce the risk of hospitalisation amongst outpatients and ED patients. Nebulised hypertonic saline seems to be a safe treatment in infants with bronchiolitis with only minor and spontaneously resolved adverse events, especially when administered in conjunction with a bronchodilator. The certainty of the evidence was low to very low for all outcomes, mainly due to inconsistency and risk of bias.