ResearchOutcome of children with life-threatening asthma necessitating pediatric intensive care

Objective: To report the outcome of children with life-threatening asthma (LTA) admitted to a university Pediatric Intensive Care Unit (PICU). Methods: Retrospective study between October 2002 and May 2010 was carried out. Every child with LTA and bronchospasm was included. Results: 30 admissions of 28 patients (13 M, 17 F) were identified which accounted for 3% of total PICU admissions (n = 1033) over the study period. The majority of patients were toddlers (median age 3.1 years). Few had past history of prematurity, lung diseases, or neuro-developmental conditions. Approximately half had previous admissions for asthma and one-forth with history of non-compliance to recommended treatment for asthma. One patient had parainfluenza virus and one had rhinovirus isolated. None of these factors were associated with need for mechanical ventilation (n = 6 admissions). Comparing with patients who did not receive mechanical ventilation, ventilated children had significantly higher PIM2 score (1.65 versus 0.4, p < 0.001), higher PCO2 levels (9.3 kPa versus 5.1 kPa, p = 0.01) and longer PICU stay (median 2.5 days versus 2 days, p = 0.03) The majority of patients received systemic corticosteroids, intravenous or inhaled bronchodilators. There was one pneumothorax but no death in this series. Conclusions: LTA accounted for a small percentage of PICU admissions. Previous hospital admissions for asthma and history of non-compliance were common. Approximately one quarters required ventilatory supports. Regardless of the need for mechanical ventilation, all patients survived with prompt treatment. Introduction Asthma is a very common childhood condition worldwide and in Hong Kong. Acute asthmatic attacks cause significant morbidity and account for a significant number of emergency department consultations and hospital admissions[1-4]. Most children admitted to the hospital because of acute asthma do not require intensive care treatment. Nevertheless, a small percentage of children with life-threatening asthma (LTA) would develop progressive respiratory failure refractory to treatment and require admission to the pediatric intensive care unit (PICU)[5-7]. In those who are admitted to the ICU, approximately 10 to 33% need intubation and mechanical ventilation, with a risk of worsening bronchospasm and hyperinflation, barotrauma, and cardiovascular depression[8,9]. If not promptly managed, severe asthmatic attacks may occasionally result in death[1-10]. The purpose of this study was to report the clinical pattern and outcome of all children with LTA and severe bronchospasm admitted to the PICU. Methods We retrospectively reviewed the medical records and analyzed data from all children with LTA admitted to the PICU of a tertiary care university hospital (Prince of Wales Hospital) in Hong Kong during the period October 2002 and May 2010. LTA was defined as all children with asthma who required ICU admission and care. The initial diagnosis was made clinically by the admitting physicians. Final diagnosis was confirmed on chart review and subsequent evaluations. The hospital provides PICU care to a catchment population of approximately 1.1 million. The following data were collected: age, sex, duration of admission, treatment of the LTA, clinical condition, blood gases, the incidence of barotrauma, and outcome. * Correspondence: ehon@hotmail.com 1 Department of Pediatrics, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong Full list of author information is available at the end of the article © 2010 Hon et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Hon et al. Italian Journal of Pediatrics 2010, 36:47 http://www.ijponline.net/content/36/1/47 Page 2 of 5 Respiratory viruses and bacterial pathogens were routinely screened for by standard examination of nasopharyngeal aspirate and cultures. The Pediatric Index of Mortality 2 (PIM2) score based on admission data was used as severity score[11]. Numerical data were compared with Mann Whitney U test and categorical data with χ2 or Fisher exact test. All comparisons were made two-tailed, and p-values less than 0.05 considered statistically significant. Results There were 30 admissions (13 boys and 17 girls; median age, 3.1 years; IQR 2.0 6.8 years; Table 1) with LTA which accounted for 3% of total PICU admissions (n = 1033) over a study period of 7 years and 8 months. Two male patients were admitted twice because of a recurrent episode of LTA. Indications for admission to the PICU were severe dyspnea, worsening or failure to improve on nebulized bronchodilators, and need for administration of intravenous salbutamol or mechanical ventilation. The decision for PICU admission was determined clinically together with blood gas as well as pulse oximetry parameters by the admitting physicians. In terms of risk factors, 'smoker(s) at home' were present in 5 of the admissions, 'history of atopy in 1 st degree relative' in 11 admissions, and 'personal history of atopy' in 20 admissions. Few had past history of prematurity (n = 4 admissions), lung diseases (1 neonatal pneumothorax, 1 pneumonia, 1 chronic lung disease, and 4 recurrent bronchiolitis), neuro-developmental condition (Rasmussen's encephalitis plus epilepsy × 2 admissions). Half had previous admissions for asthma and one-fourth with history of non-compliance to recommended treatment for asthma. In the ventilated group, three patients were on inhaled corticosteroid but compliance to corticosteroid was reportedly poor in two. In the non-ventilated group, 9 patients were on inhaled corticosteroid. One patient also received oral montelukast. Poor-compliance to asthma management was reported in 5 patients. One patient had parainfluenza virus and one had rhinovirus isolated. None of these factors were associated with need for mechanical ventilation which was required in 6 patients. Ventilator modes included Synchronized Intermittent Mandatory Ventilation (SIMV) or Pressure Regulated Volume Control mode (PRVC), with low Positive End-Expiratory Pressure (PEEP) and low inspiratory to expiratory (I:E) ratios. Comparing with patients who did not receive mechanical ventilation, ventilated children had significantly higher PIM2 score (1.65 versus 0.4, p < 0.001), higher first PaCO2 levels measured at PICU (9.3 kPa versus 5.1 kpa, p = 0.01) and longer PICU stay (median 2.5 days versus 2 days, p = 0.03) but no differences in other factors evaluated in Table 1. These patients received systemic corticosteroids and intravenous or inhaled bronchodilators. Some received intravenous magnesium sulphate. There was one pneumothorax but no death in this series. A 7-year-old girl with asthma but no previous asthma hospitalization, presented with sudden dyspnoea following a 2-day history of blocked nose and cough. Her private practitioner prescribed inhaled and oral bronchodilators. However, dyspnoea was not relieved and chest radiograph at the emergency department revealed left apical pneumothorax, which was drained with a chest drain. CT scan of the thorax showed subcutaneous emphysema, pneumomediastinum, and pneumothorax. Her symptoms resolved at the PICU following corticosteroid and inhaled salbutamol. Mechanical ventilation was not required. The chest drain was removed three days later. Regardless of mechanical ventilation, all had very brief PICU stays (median 2 days; range, 1 to 7 days). Furthermore, there did not appear to be any increase in incidence of PICU admissions for LTA between 2003-2009 (median 2% of PICU admissions; Table 2). Discussion Incidence of PICU admissions Asthma is a common disease and its frequency of occurrence sometimes detracts from its potential seriousness[12]. Severe asthma in children is a frequent cause of hospital and pediatric ICU admissions in reported series[12-14]. Globally, morbidity and mortality associated with asthma have increased over the last 2 decades[1,2,4]. This increase is attributed to increasing urbanization and undertreatment of asthma especially among the high risk pediatric population with low-socioeconomic class[15]. Despite advancements in our understanding of asthma and the development of new therapeutic strategies, the morbidity and mortality rates due to asthma reportedly increased between 1980 and 1995[2,4,13]. In the United States, the mortality rate due to asthma has increased in all age, race, and sex strata. From 1975-1993, the number of deaths nearly doubled in people aged 5-14 years[2]. In Hong Kong, data about severe asthma hospitalizations are lacking. In a previous study, we reported that asthma accounts for approximately 10% of general pediatric admissions[3]. In the present study, the admission rate was only 3% of PICU admissions. It appears that LTA is a relative uncommon cause of PICU admission in our locality. The reason for this is unknown. It might reflect that treatment received at the emergency department is prompt and effective to halt PICU admission[6]. PICU treatment Status asthmaticus is severe asthma that does not respond well to immediate care and is a life-threatening medical emergency[5]. Ensuing respiratory failure results Hon et al. Italian Journal of Pediatrics 2010, 36:47 http://www.ijponline.net/content/36/1/47 Page 3 of 5 Table 1: Clinical data of children with status asthmaticus admitted to PICU Case Total (n = 30) Ventilated (n = 6) Non-ventilated (n = 24) P* Male (%) 13 (0) 5 (75) 8 (40) 0.06 Median age (IQR), yr 3.1 (2.0-5.4) 3.3 (2.0-5.5) 3.1 (1.9-6.8) 0.84 Median (IQR) PIM2, % 0.50 (0.30-1.00) 1.65 (1.45-1.95) 0.4 (0.3-0.5) < 0.001 Relevant risk factors Family history of atopy 12 1 11 0.36 Prematurity < 36 weeks (%) 4 (14) 0 (12) 4 (15) 0.57 History of chronic lung disease, bronchiolitis, p