Pediatric Croup Due to Omicron Infection Is More Severe Than Non-COVID Croup.

OBJECTIVE: Croup due to infection with the omicron variant of COVID is an emerging clinical entity, but distinguishing features of omicron croup have not yet been characterized. We designed a study to compare the clinical features of croup patients presenting to the pediatric emergency department pre-COVID pandemic with COVID-positive croup patients who presented during the initial omicron surge. METHODS: This was a retrospective observational cohort study of children 0 to 18 years old who presented to our urban, tertiary care pediatric emergency department with symptoms of croup. The study compared a cohort of croup patients who presented in the year before the onset of the COVID pandemic to a cohort of COVID-positive croup patients who presented during the initial omicron surge. The primary outcomes included illness severity and treatments required in the emergency department. The secondary outcome was hospital admission rate. RESULTS: There were 499 patients enrolled in the study, 88 in the omicron croup cohort and 411 in the classic croup cohort. Compared with the classic croup patients, omicron croup patients were more likely to present with stridor at rest (45.4% vs 31.4%; odds ratio [OR], 1.82; confidence interval [CI], 1.14-2.91) and hypoxia (3.4% vs 0.5%; OR, 7.22; CI, 1.19-43.86). Omicron croup patients required repeat dosing of inhaled epinephrine in the emergency department more often (20.4% vs 6.8%; OR, 3.51; CI, 1.85-6.70), and they were more likely to require respiratory support (9.1% vs 1.0%; OR, 10.18; CI, 2.99-34.60). Admission rates were significantly higher for omicron croup patients than for classic croup patients (22.7% vs 3.9%; OR, 7.26; CI, 3.58-14.71), and omicron croup patients required intensive care more frequently (5.7% vs 1.5%; OR, 4.07; CI, 1.21-13.64). CONCLUSIONS: Pediatric patients with omicron croup develop more severe disease than do children with classic croup. They are more likely to require additional emergency department treatments and hospital admission than patients with croup before the COVID pandemic.

When Stridor is Not Croup: A Case Report.

BACKGROUND: Croup is one of the most common causes of acute respiratory disorder in children. It presents as acute laryngeal symptoms in the context of viral infection. Treatment consists of systemic steroids and aerosolized adrenaline, after which the symptoms must resolve rapidly. There are many differential diagnoses, including neurological causes. In these cases, clinical presentation is atypical and the outcome can be less favorable. CASE REPORT: We present the cases of three children who presented with stridor, which was initially treated as croup but eventually turned out to have a neurological origin. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Clinicians need to be aware of the differential diagnoses of croup. We suggest a few key points to help emergency physicians manage these patients, including adequate use of monitoring and nasofibroscopy. Early identification is a key element in the effective management of certain rapidly progressive neurological diseases.

Croup as a Previously Unrecognized Symptom of COVID-19 in Infants.

Although the most common symptoms of coronavirus disease 2019 (COVID-19) in children are fever and cough, cases of croup associated with COVID-19 are reported in the literature and have increased sharply with the Omicron variant. We present severe acute respiratory syndrome coronavirus 2 as a viral agent in an infant presenting with croup.

Retrospective Evaluation of Return Rates in Pediatric Patients Treated With Inhaled Racemic Epinephrine for Croup.

OBJECTIVES: To determine if the length of observation (< 2 hours vs ≥ 2 hours) following treatment of croup with inhaled racemic epinephrine in the emergency department (ED) is associated with return rates (within 48 hours after treatment) in pediatric patients. METHODS: We conducted a retrospective review of patients' medical records from February 2010 through June 2018 for pediatric patients (male and female, ≤ 12 years of age) diagnosed with croup in the ED, treated with racemic epinephrine, and discharged from the ED. RESULTS: We evaluated patients observed for less than 1 hour, 1 to 2 hours, and greater than 2 hours to determine difference in return rates within 48 hours. For patients with mild croup symptoms, 2% observed for less than 1 hour returned; 5% observed for 1 to 2 hours returned, and 3% observed for greater than 2 hours returned. Of the patients with moderate croup symptoms, 29% observed for less than 1 hour returned, 20% observed for 1 to 2 hours returned, and 20% observed for greater than 2 hours returned. A majority who returned for follow-up were not retreated with racemic epinephrine. CONCLUSION: Based on our study results, we can conclude that observing patients following treatment of croup with inhaled racemic epinephrine in the ED for less than 2 hours did not increase their risk of deterioration or need to return. Our data did not show that a longer observation time resulted in lower return rates within 48 hours.

Recurrent Croup.

Croup refers to airway inflammation and edema leading to obstruction of the larynx, trachea, and bronchi. Croup is the most common cause of acute airway obstruction in young children. It is characterized by the onset of low-grade fever, barky cough, stridor, hoarseness, and respiratory distress. Croup is typically caused by a viral infection (viral croup) but can occur suddenly without a viral prodrome (spasmodic croup). Recurrent croup is defined as two or more episodes per year. Recurrent croup should be considered a symptom of an underlying structural or inflammatory airway abnormality and should prompt a work-up for the underlying cause.

Management and referral of acute laryngotracheitis - Croup: The New South Wales Neonatal and Paediatric Emergency Transport Service experience.

AIM: To evaluate the experience of NETS (The Newborn and paediatric Emergency Transport Service) New South Wales (NSW) with children referred with a provisional diagnosis of croup. To examine the adherence of referral hospitals to NSW Health policy guidelines and to establish criteria for the need to transfer and the level of escort required for a child with croup to a higher level of care. METHODS: A retrospective audit of all children with a provisional diagnosis of croup referred to NETS over the epoch: 2005-2015. The NETS database was searched for keywords: croup and laryngotracheitis. Demographics, retrieval characteristics and management strategies were collected. RESULTS: A total of 432 patients were identified. The number of children triaged to a medically led NETS team for transfer decreased (P < 0.001) whilst those transferred into more local regional or metropolitan hospitals (P < 0.001) increased. The number of adrenaline doses was not associated with intensive care admissions or the need for invasive ventilation. CONCLUSION: Medically led retrieval teams are not necessary for safe transfer of children with a provisional diagnosis of croup unless the airway is secured with an endotracheal tube. Transfer to more local hospitals for paediatric care should be considered and time allowed for medications to take effect prior to movement.

Heliox for croup in children.

BACKGROUND: Croup is an acute viral respiratory infection with upper airway mucosal inflammation that may cause respiratory distress. Most cases are mild. Moderate to severe croup may require treatment with corticosteroids (the benefits of which are often delayed) and nebulised epinephrine (adrenaline) (the benefits of which may be short-lived and which can cause dose-related adverse effects including tachycardia, arrhythmias, and hypertension). Rarely, croup results in respiratory failure necessitating emergency intubation and ventilation. A mixture of helium and oxygen (heliox) may prevent morbidity and mortality in ventilated neonates by reducing the viscosity of the inhaled air. It is currently used during emergency transport of children with severe croup. Anecdotal evidence suggests that it relieves respiratory distress. This review updates versions published in 2010, 2013, and 2018. OBJECTIVES: To examine the effect of heliox compared to oxygen or other active interventions, placebo, or no treatment on relieving signs and symptoms in children with croup as determined by a croup score and rates of admission and intubation. SEARCH METHODS: We searched CENTRAL, which includes the Cochrane Acute Respiratory Infections Group Specialised Register, MEDLINE, Embase, CINAHL, Web of Science, and LILACS, on 15 April 2021. We also searched the World Health Organization International Clinical Trials Registry Platform (apps.who.int/trialsearch/) and ClinicalTrials.gov (clinicaltrials.gov) on 15 April 2021. We contacted the British Oxygen Company, a leading supplier of heliox. SELECTION CRITERIA: Randomised controlled trials (RCTs) and quasi-RCTs comparing the effect of heliox in comparison with placebo, no treatment, or any active intervention(s) in children with croup. DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane. Data that could not be pooled for statistical analysis were reported descriptively. MAIN RESULTS: We included 3 RCTs involving a total of 91 children aged between 6 months and 4 years. Study duration was from 7 to 16 months, and all studies were conducted in emergency departments. Two studies were conducted in the USA and one in Spain. Heliox was administered as a mixture of 70% heliox and 30% oxygen. Risk of bias was low in two studies and high in one study because of its open-label design. We did not identify any new trials for this 2021 update. One study of 15 children with mild croup compared heliox with 30% humidified oxygen administered for 20 minutes. There may be no difference in croup score changes between groups at 20 minutes (mean difference (MD) -0.83, 95% confidence interval (CI) -2.36 to 0.70) (Westley croup score, scale range 0 to 16). The mean croup score at 20 minutes postintervention may not differ between groups (MD -0.57, 95% CI -1.46 to 0.32). There may be no difference between groups in mean respiratory rate (MD 6.40, 95% CI -1.38 to 14.18) and mean heart rate (MD 14.50, 95% CI -8.49 to 37.49) at 20 minutes. The evidence for all outcomes in this comparison was of low certainty, downgraded for serious imprecision. All children were discharged, but information on hospitalisation, intubation, or re-presenting to emergency departments was not reported. In another study, 47 children with moderate croup received one dose of oral dexamethasone (0.3 mg/kg) with either heliox for 60 minutes or no treatment. Heliox may slightly improve Taussig croup scores (scale range 0 to 15) at 60 minutes postintervention (MD -1.10, 95% CI -1.96 to -0.24), but there may be no difference between groups at 120 minutes (MD -0.70, 95% CI -1.56 to 0.16). Children treated with heliox may have lower mean Taussig croup scores at 60 minutes (MD -1.11, 95% CI -2.05 to -0.17) but not at 120 minutes (MD -0.71, 95% CI -1.72 to 0.30). Children treated with heliox may have lower mean respiratory rates at 60 minutes (MD -4.94, 95% CI -9.66 to -0.22), but there may be no difference at 120 minutes (MD -3.17, 95% CI -7.83 to 1.49). There may be a difference in hospitalisation rates between groups (odds ratio 0.46, 95% CI 0.04 to 5.41). We assessed the evidence for all outcomes in this comparison as of low certainty, downgraded due to imprecision and high risk of bias related to an open-label design. Information on heart rate and intubation was not reported. In the third study, 29 children with moderate to severe croup all received continuous cool mist and intramuscular dexamethasone (0.6 mg/kg). They were then randomised to receive either heliox (given as a mixture of 70% helium and 30% oxygen) plus one to two doses of nebulised saline or 100% oxygen plus nebulised epinephrine (adrenaline), with gas therapy administered continuously for three hours. Heliox may slightly improve croup scores at 90 minutes postintervention, but may result in little or no difference overall using repeated-measures analysis. We assessed the evidence for all outcomes in this comparison as of low certainty, downgraded due to high risk of bias related to inadequate reporting. Information on hospitalisation or re-presenting to the emergency department was not reported. The included studies did not report on adverse events, intensive care admissions, or parental anxiety. We could not pool the available data because each comparison included data from only one study. AUTHORS' CONCLUSIONS: Given the very limited available evidence, uncertainty remains regarding the effectiveness and safety of heliox. Heliox may not be more effective than 30% humidified oxygen for children with mild croup, but may be beneficial in the short term for children with moderate croup treated with dexamethasone. The effect of heliox may be similar to 100% oxygen given with one or two doses of adrenaline. Adverse events were not reported, and it is unclear if these were monitored in the included studies. Adequately powered RCTs comparing heliox with standard treatments are needed to further assess the role of heliox in the treatment of children with moderate to severe croup.

Not All Stridor Is Croup.

BACKGROUND: Emergency providers often attribute stridor to croup in pediatric patients. However, even in children who are having other symptoms of a viral etiology, several other causes need to be considered. CASE: A 6-month-old term male without significant past medical history presented to the emergency department with stridor with likely underlying laryngospasm. He was initially ascribed the diagnosis of croup and was discharged home after receiving steroids and racemic epinephrine. However, he returned hours later after a seizure event at home. A thorough evaluation revealed an ionized calcium of 0.49 mmol/L, and further history revealed the patient was being fed a coconut water-based homemade solution for several months. He was subsequently found to have rickets and delay in milestone achievement. Awareness of hypocalcemia as a possible cause of laryngospasm is important because of the potential life-threatening effects of critically low calcium. Hypocalcemia should be included in the differential diagnosis of any child who presents with stridor, especially if lacking other symptoms of a viral illness.

Management and outcomes of patients presenting to the emergency department with croup: Can we identify which patients can safely be discharged from the emergency department?

AIM: Croup is a major cause of emergency department (ED) presentations, but there remains a paucity of evidence to guide clinical decision-making around which patients require admission. We aimed to describe the clinical characteristics, management and outcomes of patients presenting to the ED with croup and to identify characteristics associated with a need for further intervention. METHODS: We conducted a retrospective cohort study of all patients presenting to the ED of a tertiary paediatric hospital with croup between 2011 and 2016. Patients were included if they received two doses of nebulised adrenaline in the ED and were aged between 6 months and 6 years. Baseline characteristics, vital signs 2 h post-second dose of nebulised adrenaline, management and outcomes were recorded. RESULTS: A total of 5045 patients presented to ED with croup during the study period, 112 of whom received two doses of nebulised adrenaline within the ED. Of these patients, half were discharged home and half admitted to hospital. None of the discharged patients went on to require further intervention, and 19% of admitted patients received further interventions. Age and history of a chronic medical condition were associated with a need for further intervention. Of the vital signs, abnormal heart rate, fever and stridor were associated with a need for further intervention. CONCLUSIONS: Only 19% of patients admitted following two doses of nebulised adrenaline in the ED required further interventions. Older patients without a chronic medical condition who have a normal heart rate, temperature and no stridor may be suitable for outpatient management.

Heliox for croup in children.

BACKGROUND: Croup is an acute viral respiratory infection with upper airway mucosal inflammation that may cause respiratory distress. Most cases are mild. Moderate to severe croup may require treatment with corticosteroids (from which benefits are often delayed) and nebulised epinephrine (adrenaline) (which may be short-lived and can cause dose-related adverse effects including tachycardia, arrhythmias, and hypertension). Rarely, croup results in respiratory failure necessitating emergency intubation and ventilation.A mixture of helium and oxygen (heliox) may prevent morbidity and mortality in ventilated neonates by reducing the viscosity of the inhaled air. It is currently used during emergency transport of children with severe croup. Anecdotal evidence suggests that it relieves respiratory distress.This review updates versions published in 2010 and 2013. OBJECTIVES: To examine the effect of heliox compared to oxygen or other active interventions, placebo, or no treatment, on relieving signs and symptoms in children with croup as determined by a croup score and rates of admission and intubation. SEARCH METHODS: We searched CENTRAL, which includes the Cochrane Acute Respiratory Infections Group's Specialised Register; MEDLINE; Embase; CINAHL; Web of Science; and LILACS in January and February 2018. We also searched the World Health Organization International Clinical Trials Registry Platform (apps.who.int/trialsearch/) and ClinicalTrials.gov (clinicaltrials.gov) on 8 February 2018. We contacted British Oxygen Company, a leading supplier of heliox (BOC Australia 2017). SELECTION CRITERIA: Randomised controlled trials (RCTs) and quasi-RCTs comparing the effect of heliox in comparison with placebo or any active intervention(s) in children with croup. DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane. We reported data that could not be pooled for statistical analysis descriptively. MAIN RESULTS: We included 3 RCTs with 91 children aged between 6 months and 4 years. Study duration was from 7 to 16 months; all studies were conducted in emergency departments in the USA (two studies) and Spain. Heliox was administered as a mixture of 70% heliox and 30% oxygen. Risk of bias was low in two studies and high in one study due to an open-label design. We added no new trials for this update.One study of 15 children with mild croup compared heliox with 30% humidified oxygen administered for 20 minutes. There may be no difference in croup score changes between groups at 20 minutes (mean difference (MD) -0.83, 95% confidence interval (CI) -2.36 to 0.70). The mean croup score at 20 minutes postintervention may not differ between groups (MD -0.57, 95% CI -1.46 to 0.32). There may be no difference between groups in mean respiratory rate (MD 6.40, 95% CI -1.38 to 14.18) and mean heart rate (MD 14.50, 95% CI -8.49 to 37.49) at 20 minutes. The evidence for all outcomes in this comparison was of low quality, downgraded for serious imprecision. All children were discharged, but information on hospitalisation, intubation, or re-presenting to emergency departments was not reported.In another study, 47 children with moderate croup received one dose of oral dexamethasone (0.3 mg/kg) with either heliox for 60 minutes or no treatment. Heliox may slightly improve croup scores at 60 minutes postintervention (MD -1.10, 95% CI -1.96 to -0.24), but there may be no difference between groups at 120 minutes (MD -0.70, 95% CI -4.86 to 3.46). Children treated with heliox may have lower mean Taussig croup scores at 60 minutes (MD -1.11, 95% CI -2.05 to -0.17) but not at 120 minutes (MD -0.71, 95% CI -1.72 to 0.30). Children treated with heliox may have lower mean respiratory rates at 60 minutes (MD -4.94, 95% CI -9.66 to -0.22), but there may be no difference at 120 minutes (MD -3.17, 95% CI -7.83 to 1.49). There may be no difference in hospitalisation rates between groups (OR 0.46, 95% CI 0.04 to 5.41). We assessed the evidence for all outcomes in this comparison as of low quality, downgraded due to imprecision and high risk of bias related to open-label design. Information on heart rate and intubation was not reported.In the third study, 29 children with moderate to severe croup received intramuscular dexamethasone (0.6 mg/kg) and either heliox with one to two doses of nebulised saline, or 100% oxygen with one to two doses of adrenaline for three hours. Heliox may slightly improve croup scores at 90 minutes postintervention, but may have little or no difference overall using repeated measures analysis. We assessed the evidence for all outcomes in this comparison as of low quality, downgraded due to high risk of bias related to inadequate reporting. Information on hospitalisation or re-presenting to the emergency department was not reported.The included studies did not report on adverse events, intensive care admissions, or parental anxiety.We could not pool the available data because each comparison included data from only one study. AUTHORS' CONCLUSIONS: Due to very limited evidence, uncertainty remains about the effectiveness and safety of heliox. Heliox may not be more effective than 30% humidified oxygen for children with mild croup, but may be beneficial in the short term for children with moderate to severe croup treated with dexamethasone. The effect may be similar to 100% oxygen given with one or two doses of adrenaline. Adverse events were not reported, and it is unclear if these were monitored in the included studies. Adequately powered RCTs comparing heliox with standard treatments are needed to further assess the role of heliox in the treatment of children with moderate to severe croup.

Croup: Diagnosis and Management.

Croup is a common respiratory illness affecting 3% of children six months to three years of age. It accounts for 7% of hospitalizations annually for fever and/or acute respiratory illness in children younger than five years. Croup is a manifestation of upper airway obstruction resulting from swelling of the larynx, trachea, and bronchi, leading to inspiratory stridor and a barking cough. Many patients experience low-grade fevers, but fever is not necessary for diagnosis. Less commonly, stridor can be associated with acute epiglottitis, bacterial tracheitis, and foreign body airway obstruction. Laboratory studies are seldom needed for diagnosis of croup. Viral cultures and rapid antigen testing have minimal impact on management and are not routinely recommended. Radiography and laryngoscopy should be reserved for patients in whom alternative diagnoses are suspected. Randomized controlled trials have demonstrated that a single dose of oral, intramuscular, or intravenous dexamethasone improves symptoms and reduces return visits and length of hospitalization in children with croup of any severity. In patients with moderate to severe croup, the addition of nebulized epinephrine improves symptoms and reduces length of hospitalization.

Prognostic factors and importance of recognition of adult croup.

OBJECTIVES: Croup, or laryngotracheobronchitis, is a common disease in childhood. On the other hand, to our knowledge, there are only 14 cases in six English literatures describing adult croup (AC). The clinical features of AC have not been well known. METHODS: We conducted a retrospective analysis of medical records of 18 patients with AC during the period from 2008 to 2016. RESULTS: None of the 18 patients required an urgent airway intervention. Univariate analysis indicated that the duration of symptoms was significantly longer in patients with cough (p < .01) and younger patients (age < 60, p = .037). The duration of subglottic edema was significantly longer in female (p = .035), patients with high levels of CRP (≥1 mg/dL, p = .049), and patients with cough symptom (p = .035). CONCLUSIONS: Female, young age (<60 years), the symptom of cough, and high levels of CRP should be recognized as signs of prolonged AC. It is important to confirm the diagnosis of AC by laryngoscopic examination, which also help to avoid airway intervention.

Association of croup with asthma in children: A cohort study.

Asthma and croup are common inflammatory airway diseases involving the bronchus in children. However, no study has reported the effects of urbanization, sex, age, and bronchiolitis on the association of croup and its duration with asthma development. We used the Taiwan Longitudinal Health Insurance Database (LHID) to perform this population-based cohort study; here, the cluster effect caused by hospitalization was considered to evaluate the association between croup and asthma development and the risk factors for asthma in children of different age groups. We evaluated children with croup aged <12 years (n = 1204) and age-matched control patients (n = 140,887) by using Cox proportional hazards regression analysis within a hospitalization cluster. Of all 142,091 patients, 5799 (including 155 with croup [419 per 1000 person-y] and 5644 controls [106 per 1000 person-y]) had asthma during the 5-year follow-up period. During the 5-year follow-up period, the hazard ratios (HRs [95% CIs]) for asthma were 2.10 (1.81-2.44) in all children with croup, 2.13 (1.85-2.46) in those aged 0 to 5 years, and 2.22 (1.87-2.65) in those aged 6 to 12 years. Children with croup aged 7 to 9 years had a higher HR for asthma than did those in other age groups. Boys with croup had a higher HR for asthma. The adjusted HR for asthma was 1.78 times higher in children with croup living in urban areas than in those living in rural areas. In conclusion, our analyses indicated that sex, age, bronchiolitis, and urbanization level are significantly associated with croup and asthma development. According to our cumulative hazard rate curves, younger children with croup should be closely monitored for asthma development for at least 3 years.

Recurrent croup and persistent laryngomalacia: Clinical resolution after supraglottoplasty.

OBJECTIVES: To determine if children with recurrent croup (RC) and persistent laryngomalacia (LM) clinically improve after supraglottoplasty (SGP). MATERIAL AND METHODS: Retrospective chart review cohort at tertiary care children's hospital consisting of patients diagnosed with LM and RC that underwent SGP from July 2011 to August 2014. Clinical history, demographics, clinical outcomes, and operative complications were reviewed. Specifically, the episodes of croup requiring systemic steroids were compared pre- and post-SGP with statistical analysis. RESULTS: Out of 107 patients undergoing SGP for LM, 6 patients (5.6%) were diagnosed with RC. Mean age at first croup episode was 11.5 months. Mean age at SGP was 4.3 years. Mean number of emergency department visits was 3.2 (range 2-6 visits) prior to SGP. Mean number of episodes of croup requiring systemic steroids before and after SGP was 9.8 vs. 0.2 (p=0.003). Mean length of followup after SGP was 30.5 months (range 18-46 months). There were no surgical postoperative complications. CONCLUSIONS: This is the first series to describe the clinical resolution of croup episodes in children with LM corrected by SGP. Recurrent croup should be added among other conditions associated with late-onset or persistent laryngomalacia.

Croup.

INTRODUCTION: Croup is characterised by the abrupt onset, most commonly at night, of a barking cough, inspiratory stridor, hoarseness, and respiratory distress due to upper airway obstruction. It leads to signs of upper airway obstruction, and must be differentiated from acute epiglottitis, bacterial tracheitis, or an inhaled foreign body. Croup affects about 3% of children per year, usually between the ages of 6 months and 3 years, and 75% of infections are caused by parainfluenza virus. Symptoms usually resolve within 48 hours, but severe upper airway obstruction can, rarely, lead to respiratory failure and arrest. METHODS AND OUTCOMES: We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of treatments in children with mild croup and moderate to severe croup? We searched: Medline, Embase, The Cochrane Library, and other important databases up to November 2013 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). RESULTS: We found 19 studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. CONCLUSIONS: In this systematic review we present information relating to the effectiveness and safety of the following interventions: corticosteroids (dexamethasone, intramuscular and oral), nebulised budesonide, oral prednisolone, heliox, humidification, and nebulised adrenaline (racemate and L-adrenaline [ephinephrine]).

Heliox for croup in children.

BACKGROUND: Croup is thought to be triggered by a viral infection and is characterised by respiratory distress due to upper airway inflammation and swelling of the subglottic mucosa in children. Mostly it is mild and transient and resolves with supportive care. In moderate to severe cases, treatment with corticosteroids and nebulised epinephrine (adrenaline) is required. Corticosteroids improve symptoms but it takes time for a full effect to be achieved. In the interim, the child is at risk of further deterioration. This may rarely result in respiratory failure necessitating emergency intubation and ventilation. Nebulised epinephrine may result in dose-related adverse effects including tachycardia, arrhythmias and hypertension and its benefit may be short-lived. Helium-oxygen (heliox) inhalation has shown therapeutic benefit in initial treatment of acute respiratory syncytial virus (RSV) bronchiolitis and may prevent morbidity and mortality in ventilated neonates. Heliox has been used during emergency transport of children with severe croup and anecdotal evidence suggests that heliox relieves respiratory distress. OBJECTIVES: To examine the effect of heliox on relieving symptoms and signs of croup, as determined by a croup score (a tool for measuring the severity of croup).To examine the effect of croup on rates of admission or intubation (or both), through comparisons of heliox with placebo or any active intervention(s) in children with croup. SEARCH METHODS: We searched CENTRAL 2013, Issue 10, MEDLINE (1950 to October week 5, 2013), EMBASE (1974 to November 2013), CINAHL (1982 to November 2013), Web of Science (1955 to November 2013) and LILACS (1982 to November 2013). In addition, we searched two clinical trials registries: the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) and clinicaltrials.gov (searched 12 November 2013). SELECTION CRITERIA: Randomised controlled trials (RCTs) and quasi-RCTs comparing the effect of helium-oxygen mixtures with placebo or any active intervention(s) in children with croup. DATA COLLECTION AND ANALYSIS: Two review authors independently identified and assessed citations for inclusion. A third review author resolved disagreements. We assessed included trials for allocation concealment, blinding of intervention, completeness of outcome data, selective outcome reporting and other potential sources of bias. We reported mean differences for continuous data and odds ratios for dichotomous data. We descriptively reported data not suitable for statistical analysis. MAIN RESULTS: We included three RCTs with a total of 91 participants. One study compared heliox 70%/30% with 30% humidified oxygen administered for 20 minutes in children with mild croup and found no statistically significant differences in the overall change in croup scores between heliox and the comparator. In another study, children with moderate to severe croup were administered intramuscular dexamethasone 0.6 mg/kg and either heliox 70%/30% with one to two doses of nebulised saline, or 100% oxygen with one to two doses of nebulised racaemic epinephrine for three hours. In this study, the heliox group's croup scores improved significantly more at all time points from 90 minutes onwards. However, overall there were no significant differences in croup scores between the groups after four hours using repeated measures analysis. In a third study, children with moderate croup all received one dose of oral dexamethasone 0.3 mg/kg with heliox 70%/30% for 60 minutes in the intervention group and no treatment in the comparator. There was a statistically significant difference in croup scores at 60 minutes in favour of heliox but no significant difference after 120 minutes. It was not possible to pool outcomes because the included studies compared different interventions and reported different outcomes. No adverse events were reported. AUTHORS' CONCLUSIONS: There is some evidence to suggest a short-term benefit of heliox inhalation in children with moderate to severe croup who have been administered oral or intramuscular dexamethasone. In one study, the benefit appeared to be similar to a combination of 100% oxygen with nebulised epinephrine. In another study there was a slight change in croup scores between heliox and controls, with unclear clinical significance. In another study in mild croup, the benefit of humidified heliox was equivalent to that of 30% humidified oxygen, suggesting that heliox is not indicated in this group of patients provided that 30% oxygen is available. Adequately powered RCTs comparing heliox with standard treatments are needed to further assess the role of heliox in children with moderate to severe croup.