Indian J Pediatr (2010) 77:1417–1423 DOI 10.1007/s12098-010-0189-8
REVIEW
Management of Status Asthmaticus in Children Sunil Saharan & Rakesh Lodha & Sushil K. Kabra
Received: 21 July 2010 / Accepted: 18 August 2010 / Published online: 8 September 2010 # Dr. K C Chaudhuri Foundation 2010
Abstract Asthma is a common chronic inflammatory disorder of the airways characterized by recurrent wheezing, breathlessness, and coughing. Acute exacerbations of asthma can be life-threatening; annual worldwide estimated mortality is 250,000 and most of these deaths are preventable. While most of the acute exacerbations can be managed successfully in the emergency room, few children have severe exacerbations requiring intensive care. Mainstay of treatment for status asthmaticus are inhaled β2 agonist and anticholinergic agents, oxygen along with corticosteroids. Children who do not respond well to initial treatment require parenteral β2 agonist and magnesium. Rarely, sick children need parenteral aminophylline infusion and mechanical ventilation. Guidelines for diagnosis, treatment, ventilator management and supportive care for status asthmaticus in children are discussed in the protocol. Keywords Children . Status asthmaticus . Respiratory distress
Introduction Asthma is a chronic inflammatory disorder of the airways characterized by recurrent episodes of wheezing, breathlessness, and coughing, particularly at night or in the early morning. Episodes of bronchoconstriction are associated with airflow obstruction within the lung that is often reversible either spontaneously or with treatment. Asthma S. Saharan : R. Lodha (*) : S. K. Kabra Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 10029, India e-mail:
[email protected]
is a common problem worldwide, with an estimated 300 million affected individuals [1]. Global prevalence of asthma ranges from 1% to 18% of the population in different countries [1]. Annual worldwide deaths from asthma have been estimated at 250,000 with no correlation of mortality with prevalence [1]. In India, as per ISSAC phase three study, there was increase in asthma prevalence in 6–7 year age group from 6.2 to 6.8% and in 13–14 year age group there was decrease in asthma prevalence from 6.7 to 6.4% [2]. There are no data regarding incidence of acute asthma exacerbation in children in India. In the United States, as per 2005 National Center for Health Statistics estimates, asthma prevalence was 22.5 million (7.7% of population) and exacerbations included approximately 15 million outpatient visits, 2 million emergency room visits and 500,000 hospitalizations over 1 year [3]. In our pediatric emergency service, approximately 4% of all visits are for acute asthma (unpublished data). Of these children, only 5–10 children (4 is considered moderate status asthmaticus while patient with score 7 and above should be admitted to the ICU [11]. Oxygen saturation should be closely monitored, preferably by pulse oximetry. Oxygen saturation in children should normally be greater than 95%, and oxygen saturation less than 92% is a good predictor of the need for hospitalization [12]. Complicating factors such as pneumonia, atelectasis, pneumothorax, or pneumomediastinum should be identified early. Chest Radiography Chest radiographs should be obtained in children with first time wheeze, clinical evidence of parenchymal disease or those requiring admission to PICU. Radiographs have a limited role in the management of status asthmaticus but may be indicated when there is suspected air leak, pneumonia, or the underlying cause of wheezing is in doubt [13].
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Blood Gas Arterial blood gas measurements should be obtained in all children at baseline and subsequently as indicated. The patient should continue on supplemental oxygen while the measurement is made. A PaO2 45 mm Hg) indicates the presence of respiratory failure [13]. The decision to intubate an asthmatic child should be made on clinical grounds. Arterial blood gas measurement is useful to assess pulmonary gas exchange and pulse oximetry is not a reliable measure of adequate ventilation. Usually in children with status asthmaticus, hypocarbia is present early and normalization of CO2 with persistent respiratory distress may indicate impending respiratory failure. Frequent blood gas measurements are required in intubated children in order to follow clinical progress.
Treatment The mainstays of treatment for status asthmaticus are as discussed below (Figs. 1, 2 and 3). General Children with status asthmaticus admitted to the PICU require IV access, continuous pulse oximetry and cardiorespiratory monitoring. Sedation should be strictly avoided during exacerbations of asthma in the nonintubated children because of the respiratory depressant effect of anxiolytic and hypnotic drugs [14, 15]. For children who require mechanical ventilation, it is preferable to have an arterial and central venous access. Fluid Poor fluid intake, increased loss of insensible fluids and vomiting may cause dehydration in the asthmatic child. Fluid replacement should be aimed towards restoration of euvolemia; isotonic fluid like normal saline or Ringer’s lactate should be used to correct the dehydration. Fluid balance should be monitored carefully to avoid overhydration as this may precipitate pulmonary edema. Once euvolemia is restored, maintenance intravenous fluids should be started. Careful attention should be paid to serum potassium values, which may decrease because of use of β2 receptor agonists. Antibiotics Antibiotics are not routinely indicated in children with status asthmaticus; these should be used in children with evidence of bacterial infection as indicated by high fever, purulent secretions, consolidation on X ray film or very high leucocyte counts. Oxygen Oxygen should be administered by nasal cannulae, by mask, or rarely, by head box in some infants in order to achieve arterial oxygen saturation of 95%. Oxygen therapy
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Table 1 Assessment of severity of acute asthma-Becker asthma score [11] Score
Respiratory rate (per min)
Wheezing
I/E ratio
Accessory muscle use
0 1 2 3
50
None Terminal expiration Entire expiration Inspiration and entire expiration
1:1.5 1:2 1:3 >1:3
None 1 site 2 sites 3 sites or neck strap muscle use
should be titrated using pulse oximetry to maintain satisfactory oxygen saturation [16]. β2 agonists β2 receptor agonists remain the mainstay of therapy in status asthmaticus. They can be administered via the inhaled, intravenous, subcutaneous, or oral routes. Salbutamol and terbutaline are generally preferred due to relative β2-selectivity. In a recent study by Qureshi et al., there was no difference in clinical asthma score in children with moderate to severe asthma exacerbations after Fig. 1 Protocol on approach to children with status asthmaticus
treatment with racemic salbutamol when compared with lev-salbutamol [17]. For children who need more frequent doses of β2 agonist, continuous nebulization appears to be superior to intermittent doses [18–20]. The usual dose of continuous salbutamol nebulization is 0.15–0.5 mg/kg/hr, or 10– 20 mg/hr. The continuous nebulization system requires use of an infusion pump to deliver the medication at a constant rate to the nebulizing chamber; this rate equals the rate of nebulization. However, in the absence of a system to
Child with acute asthma exacerbation Clinical assessment (Pulmonary index score), pulse oximetry Pulmonary index score 1. Respiratory rate
CXR and ABG if indicated 2. Wheezing 3. Inspiration/ expiration ratio 4. Accessory muscle use
Assessment of severity of status asthmaticus
Admit to PICU if Becker asthma score ≥7 Comfortable environment IV access Maintain euvolemia
Supportive care
Continuous cardio-respiratory monitoring Avoid sedation Monitor potassium Antibiotics, if indicated
Management
Medications
If ventilated -arterial and central venous access
Ventilation
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Fig. 2 Medications for treatment of children with status asthmaticus
Medications
β 2 agonist
Anticholinergic agents
Salbutamol continuous nebulization0.15-0.5 mg/kg/hr, or 10-20 mg/hr Salbutamol MDI (100 mcg) 4-8 puffs Subcutaneous Terbutaline-0.01 mg/kg/dose (max 0.3 mg), may be repeated q 20 -30 min for total 3 times
Ipratropium bromide 125-500 mcg (if nebulized) administered every 20 min for up to three doses then every 4-6 hrs
Corticosteroids
Hydrocortisone 10 mg/kg IV stat Then 5 mg/kg IV q 6 hr Switch to PO Prednisolone 1-2 mg/kg/d when stable
Terbutaline -loading dose 10 mcg/kg IV over 10 min followed by 0.1-10 mcg/kg/min
Other medications Magnesium- 50 mg/kg/dose over 30 min or infusion at a rate of 10-20 mg/kg/hr, can repeat once or twice after 4-6 hrs Theophylline- loading dose of 5-7 mg/kg infused over 20 min followed by 0.5-0.9 mg/kg/hr Ketamine- 1 mg/kg/hr, titrated to effect Vecuronium- 0.1 mg/kg/hr, titrated to effect
deliver continuous nebulization, back-to-back nebulization of salbutamol in doses of 0.15 mg/kg could be used. During weaning from continuous salbutamol inhalation, children should be switched to intermittent salbutamol nebulization. In some children MDI may be used; usually four to eight puffs per dose, with each puff delivering 100 mcg. There is Ventilation
Non-invasive ventilation
Non-invasive positive pressure ventilation
Invasive ventilation
Volume control mode VT 10–12 mg/dL). Serum magnesium levels should be regularly monitored, when facility is available. Refer to Fig. 2 for the use of medications. Mechanical Ventilation (Fig. 3) Indications for intubation in children with status asthmaticus include cardiopulmonary arrest, severe hypoxia, or rapid deterioration in mental state. Intubation and mechanical ventlation are considered in a child who responds poorly to initial therapy and shows a rising PCO2. Child must be preoxygenated with 100% oxygen and hypotension should be anticipated. A cuffed endotracheal tube with the largest diameter appropriate for the age of the child should be used [32]. Histamine-producing agents, such as morphine or atracurium, must be avoided. Ketamine is a preferred induction agent in patients with severe asthma due to its bronchodilatory action. Rapid sequence intubation should proceed with a sedative or anesthetic, atropine (if indicated) and followed by a rapid-acting muscle relaxant.
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Goals of ventilation in status asthmaticus are to maintain adequate oxygenation, permissive hypercarbia and adjusting minute ventilation (peak pressure, tidal volume, and rate) in order to maintain an arterial pH of >7.2. Typically slow ventilator rates with prolonged expiratory phase, minimal end-expiratory pressure, and short inspiratory time are used in order to minimize dynamic hyperinflation and air trapping. The use of positive end-expiratory pressure in the asthmatic patient receiving mechanical ventilation is controversial [33]. For older children, one may begin with volume control mode using settings of VT of 5–6 mL/kg, RR approximately half of the normal for age, I: E ratio of 1:3 and PEEP of 2–3 cm of H2O. In infants, pressure controlled ventilation may be used with PIP adjusted to achieve adequate ventilation; the settings of rate, I:E ratio and PEEP are same as above. Tracheal extubation should be attempted as soon as possible. Most frequent complications with ventilation in these children are hypotension, oxygen desaturation, pneumothorax/subcutaneous emphysema, and cardiac arrest [34]. If hypotension and/or hypoxemia do not rapidly respond to fluid administration and alteration in ventilatory pattern, a tension pneumothorax must be considered. Analgesia, Muscle Relaxants, Inhalational Anesthetics Sedation in the asthmatic children is generally not indicated except in some children who are excessively anxious (not hypoxemic or hypercarbic) or intubated children. Sedation should be used only in the closely monitored setting. Mechanically ventilated children require heavy sedation and sometimes muscle relaxants to avoid tachypnea, ventilator asynchrony and to reduce the risk of sudden cough-induced pulmonary barotrauma. Ketamine is a good choice because it provides sedation and bronchodilation with minimal respiratory depression [35]. Ketamine by continuous infusion is the first choice for sedation, usually combined with intermittent or continuous administration of benzodiazepines. Usual ketamine dosing is 1 mg/kg/hr and is adjusted to achieve sufficient sedation. However, ketamine may lead to excessive bronchial secretions. Among opiates, fentanyl is preferred because morphine causes histamine release, which may exacerbate bronchospasm. Vecuronium is a commonly used meuromuscular blocking agent with starting dose of 0.1 mg/kg/hr titrated to achieve adequate paralysis. Inhaled general anesthetics are indicated when other measures have failed [36]. Helium Oxygen Therapy For children who are not improving with conventional therapy or children who are receiving high-pressure mechanical ventilatory support, heliox may be a reasonable adjunct therapy [37]. Kim et al. demonstrated greater clinical improvement in children treated with continuous salbutamol delivered by heliox than those
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treated with oxygen alone delivered salbutamol [38]. In systematic reviews of heliox for asthma [39, 40] and in another prospective, randomized, double-blind, crossover study of heliox in 11 nonintubated children with severe asthma [41], heliox failed to show an effect on respiratory mechanics or dyspnea scores. Leukotriene Modifiers There are little data to suggest a role for leukotriene modifiers in acute asthma [42, 43]. Noninvasive Mechanical Ventilation Noninvasive positivepressure ventilation (NIPPV) is an alternative to conventional mechanical ventilation in children with status asthmaticus. In a crossover trial between NIPPV and standard therapy in children with status asthmaticus, NIPPV group had reduced work of breathing and dyspnea as compared to the standard therapy group [44]. NIPPV should be tried prior to the institution of conventional mechanical ventilation in these children [45]. Chest Physiotherapy Chest physiotherapy (CPT) should only be considered in children with clear segmental or lobar atelectasis. In all other populations of children with status asthmaticus, CPT has no therapeutic benefit and is not recommended as part of routine management in the critically ill patient with status asthmaticus.
Outcome Mortality rates for children with severe status asthmaticus vary in different areas with overall mortality being very low. With improvement in ventilatory strategies, the availability of more selective bronchodilating agents, the prognosis has improved significantly. Nearly all asthma deaths occur in those children who suffer a cardiopulmonary arrest prior to arrival for emergency hospital care. Improved outpatient management strategies are necessary to eliminate asthma related deaths in children.
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