Novel therapies for children with severe asthma

Acute respiratory failure

Acute respiratory failure is common in critically ill children, who are at increased risk of respiratory embarrassment because of the developmental variations in the respiratory system. Although multiple etiologies exist, pneumonia and bronchiolitis are most common. Respiratory system monitoring has evolved, with the clinical examination remaining paramount. Invasive tests are commonly replaced with noninvasive monitors. Children with ALI/ARDS have better overall outcomes than adults, although data regarding specific therapies are still lacking. Most children will have some degree of long-term physiologic respiratory compromise after recovery from ALI/ARDS. The physiologic basis for respiratory failure and its therapeutic options are reviewed here.

Safety and clinical findings of BiPAP utilization in children 20 kg or less for asthma exacerbations

PURPOSE

To investigate safety and clinical findings of bilevel positive airway pressure (BiPAP) utilization in children 20 kg or less for asthma exacerbations.

METHODS

Retrospective and prospective descriptive analysis of 165 enrolled subjects with moderate and severe asthma exacerbations who weighed 20 kg or less and who received BiPAP treatment at a large, urban children's hospital pediatric emergency department (PED).

RESULTS

Age was 0.6-8.27 years (mean 3.7 years, SD 1.6 years). None exhibited worsening hypoxia, pneumothorax, or death. Four progressed to intubation after significant period on BiPAP. Overall, BiPAP subjects showed improvement in pediatric asthma score (PAS). BiPAP initiation PAS range was 8-15 (mean 12.1, SD 1.6); BiPAP termination or 4 h PAS mean was 6.3 (SD 2.2); delta PAS showed improvement mean 5.8 (SD 2.4). Seventy-one had trial off BiPAP in PED for clinical improvement; seven were restarted. PED BiPAP duration range was 30-720 min (mean 210 min, SD 158 min); total hospitalization BiPAP duration was 1-90 h. Ninety-nine (60%) subjects were admitted to the PICU and continued BiPAP for 0-47 h (mean 6.6 h, SD 8.6 h). Fifty-seven (35%) required ward admission; none were transferred to PICU. Nine (5%) were discharged home from the PED; none returned within 72 h.

CONCLUSIONS

BiPAP utilization in acute pediatric asthma exacerbations for patients 20 kg or less is safe and may improve clinical outcomes. These findings warrant future prospective investigation of BiPAP efficacy in pediatric asthma patients.

Targeting the airway smooth muscle for asthma treatment

Asthma is a complex respiratory disease whose incidence has increased worldwide in the last decade. Currently there is no cure for asthma. Although bronchodilator and anti-inflammatory medications are effective medicines in some asthmatic patients, it is clear that an unmet therapeutic need persists for a subpopulation of individuals with severe asthma. This chronic lung disease is characterized by airflow limitation, lung inflammation, and remodeling that includes increased airway smooth muscle (ASM) mass. In addition to its contractile properties, the ASM also contributes to the inflammatory process by producing active mediators, which modify the extracellular matrix composition and interact with inflammatory cells. These undesirable functions make interventions aimed at reducing ASM abundance an attractive strategy for novel asthma therapies. The following three mechanisms could limit the accumulation of smooth muscle: decreased cell proliferation, augmented cell apoptosis, and reduced cell migration into the smooth muscle layer. Inhibitors of the mevalonate pathway or statins hold promise for asthma treatment, because they exhibit anti-inflammatory, antimigratory, and antiproliferative effects in preclinical and clinical studies, and they can target the smooth muscle. This review will discuss current knowledge of ASM biology and identify gaps in the field to stimulate future investigations of the cellular mechanisms that control ASM overabundance in asthma. Targeting ASM has the potential to be an innovative venue of treatment for patients with asthma.

Emergency presentation and management of acute severe asthma in children

Acute severe asthma is one of the most common medical emergency situations in childhood, and physicians caring for acutely ill children are regularly faced with this condition. In this article we present a summary of the pathophysiology as well as guidelines for the treatment of acute severe asthma in children. The cornerstones of the management of acute asthma in children are rapid administration of oxygen, inhalations with bronchodilators and systemic corticosteroids. Inhaled bronchodilators may include selective b2-agonists, adrenaline and anticholinergics. Additional treatment in selected cases may involve intravenous administration of theophylline, b2-agonists and magnesium sulphate. Both non-invasive and invasive ventilation may be options when medical treatment fails to prevent respiratory failure. It is important that relevant treatment algorithms exist, applicable to all levels of the treatment chain and reflecting local considerations and circumstances.

Experience with use of extracorporeal life support for severe refractory status asthmaticus in children

Introduction

Severe status asthmaticus (SA) in children may require intubation and mechanical ventilation with a subsequent increased risk of death. In the patient with SA and refractory hypercapnoeic respiratory failure, use of extracorporeal life support (ECLS) has been anecdotally reported for carbon dioxide removal and respiratory support. We aimed to review the experience of a single paediatric centre with the use of ECLS in children with severe refractory SA, and to compare this with international experience from the Extracorporeal Life Support Organization (ELSO) registry.

Methods

All paediatric patients (aged from 1 to 17 years) with primary International Classification of Diseases (ICD)-9 diagnoses of SA receiving ECLS for respiratory failure from both the Children's Healthcare of Atlanta at Egleston (Children's at Egleston) database and the ELSO registry were reviewed.

Results

Thirteen children received ECLS for refractory SA at the Children's at Egleston from 1986 to 2007. The median age of the children was 10 years (range 1 to 16 years). Patients generally received aggressive use of medical and anaesthetic therapies for SA before cannulation with a median partial pressure of arterial carbon dioxide (PaCO₂) of 130 mmHg (range 102 to 186 mmHg) and serum pH 6.89 (range 6.75 to 7.03). The median time of ECLS support was 95 hours (range 42 to 395 hours). All 13 children survived without neurological sequelae. An ELSO registry review found 64 children with SA receiving ECLS during the same time period (51 excluding the Children's at Egleston cohort). Median age, pre-ECLS PaCO₂ and pH were not different in non-Children's ELSO patients. Overall survival was 60 of 64 (94%) children, including all 13 from the Children's at Egleston cohort. Survival was not significantly associated with age, pre-ECLS PaCO₂, pH, cardiac arrest, mode of cannulation or time on ECLS. Significant neurological complications were noted in 3 of 64 (4%) patients; patients with neurological complications were not significantly more likely to die (P = 0.67).

Conclusions

Single centre and ELSO registry experience provide results of a cohort of children with refractory SA managed with ECLS support. Further study is necessary to determine if use of ECLS in this setting produces better outcomes than careful mechanical ventilation and medical therapy alone.