The incidence and prevalence of asthma in children is on the rise. Though there is no such data is available in India, but some clinicians report the incidence of about 25% in children. Asthma is a chronic disease, delay in diagnosis, failure to recognize risk factors / avoid triggers and inappropriate therapy can lead to progressive disease and frequent acute exacerbations, often severe. Treatment of acute severe asthma is a challenging task for pediatricians. Understanding the patho-physiology of the disease and action of currently available drugs is essential for optimal treatment of asthma. Asthma is characterized by airflow limitation and hyper responsiveness to a variety of triggers. It is primarily a chronic inflammatory disease. Hence, therapy should be directed towards treating chronic inflammation, thereby preventing acute exacerbations. The use of reliever medicines should be minimized to need based; as and when there is bronchospasm. Acute severe asthma / Near fatal asthma / Status asthmaticus are progressively worsening attacks unresponsive to appropriate treatment with B2 agonists and theophylline leading to respiratory failure

Risk Factors:

90% of the severe attacks of asthma are present in known asthmatics. There are some risk factors which can anticipate severe attacks in asthmatics

• Chronic steroid dependent asthma
• Poor compliance
• Poor recognition of severity of attack
• Sedation
• Over-reliance on B2 agonists
• Delayed use of systemic steroids
• Repeated ED visits in prior 3 days
• Sudden onset respiratory distress
• Prior PICU admission
• Prior mechanical ventilation
• Prior respiratory arrest
• Seizures, Encephalopathy

It is of utmost importance to ask the patient / parents about these high risk factors; sudden deterioration and treatment given.

Physical Signs:

The clinician should do a quick assessment of a patient with acute severe asthma, to look for signs of hypoxia / hypercarbia (respiratory failure) i.e., use of accessory muscles, air entry, presence or absence of wheezing, pulses paradoxus (> 10 mm of Hg in children), cyanosis, altered sensorium, diaphoresis and evidence of air leak syndromes.

Investigations:

Investigations are done to help in assessing the severity of attack and not for the diagnosis.

1. X-ray chest is suggested in suspected foreign body, air leak syndromes or pneumonia.
2. ABG should be done to assess the gas exchange abnormalities.
3. Peak Flow Rate / Spirometry. These should be avoided in acute severe asthma as forced expiration can worsen airway obstruction due to dynamic collapse of smaller airways.
4. CBC has no value in management of acute severe asthma.

Acute severe asthma:

Too dyspneic to speak / feed, RR> 50/min, HR> 150/min, SaO2 90% at 60% FiO2.

• Oxygen 8 litres / min
  
• Nebulized Salbutamol and Ipratropium bromide
  
• Tab. Prednisolone or IV Hydrocortisone or IV Methyl Prednisolone
  
  

If the child improves repeat Nebulization 1-3 hourly, continue steroids and hospitalize in ward. If there is no improvement give SQ Epinephrine, hospitalize consider. Aminophylline infusion, IV Magnesium sulphate bolus over 30 minutes and / or IV Terbutaline. An ABG and X-ray chest should be considered.

Life threatening features

1. Altered sensorium, hypotonia, poor tidal volume, severe retraction, head bobbing consider SQ Epinephrine sor SQ Terbutaline.
2. Silent chest, SaO2 90% on 60% oxygen consider IV Aminophylline bolus and then infusion or Terbutaline bolus over 10 minutes and then infusion.
3. HR> 180 / minute, ST changes consider IV Magnesium sulphate.

Indications for PICU admission:

• Altered sensorium
  
• Use of accessory muscles
  
• Pulses paradoxus> 10 mm Hg
  
• Cyanosis
  
• Air leak
  
• Metabolic Acidosis
  
• PaO2 <60, PaCO2> 40 with dyspnea and wheeze
  
• ECG abnormalities

Supportive Care:

• Oxygen inhalation
  
• Hydration
  
• On ventilator restrict fluids and watch for SIADH
  

Follow up Plan:

• Identifying risk factors and eliminating
  
• Identifying triggers and eliminating if possible
  
• Effective long-term anti-inflammatory treatment
  
• A written plan for future acute attacks

Inhaled drugs

• Salbutamol
  Selective B2 agonist
  Nebulization dose 0.15 mg / kg q4hr.
  Minimum dose Infants – 1.25 mg
  1-5 years 2.5 mg
  5 years 5.0 mg
  Back to back/continuous nebulization in severe cases. It should be diluted in normal saline and not in water.
  Adverse effects Irritability, tremors, tachycardia, hypokalemia. It is not contraindicated in cardiac patients.



• Ipratropium bromide
  Anticholinergic: It works best in severe asthma, where progressively proximal airways are involved. It is also useful in GERD, post nasal drip, emotions precipitated asthma.
  Dose - <1 year – 250 mcg
  >1 year – 500 mcg
  Adverse effects: Same as Salbutamol

Injectable Drugs

• Injectable B adrenergics


• Adrenaline 0.01 ml of 1 : 1000 / kg body weight SQ safe.
  
• Terbutaline 0.005 0.01 mg / kg body weight SQ
  
• Contraindicated in patients with history of cardiac arrhythmia
  
• Terbutaline Infusion


• Loading dose of 10 mcg / kg and infusion rate of 2 10 mcg / kg / hr.
  
• Monitor HR, ECG, Serum Potassium.
  
• Decrease Aminophylline Infusion by half when using Terbutaline infusion.
  
• Aminophylline Infusion


• Loading dose of 5 6 mg / kg and infusion rate of 0.5 1.2 mg / kg / hr.
  
• Monitor HR, ECG, Drug levels
  
• Monitor for adverse effects Gastritis, vomiting, tachyarrhythmias, irritability, seizures.
  
• Steroids


• Oral Prednisolone 2 mg / kg stat, then 0.5 / 1.0 mg / kg body weight q6h.
  
• IV Hydrocortisone 10 mg / kg stat, then 5 mg / kg body weight q6h.
  
• IV Methyl Prednisolone 2 mg / kg stat, then 1 mg / kg body weight q6h.
  
Parenteral steroids have no added benefits over oral preparations. Dexamethasone is avoided due to longer adrenal suppression and water retention


• Magnesium Sulphate
  
• It reduces the availability of free calcium in cytoplasm, decreases excitability of of smooth muscle, stabilizes mast cells, inhibits histamine release and reduces . superoxide production by PMNs
  
• Doses 25 50 mg / kg / dose IV slowly over 20 minutes (maximum 2 gms). May be repeated.
  
• Monitor levels if frequent doses or infusion is needed.

Mahapedicon 2005 - Conference Abstracts.Pediatric Oncall [serial online] 2006 [cited 15 July 2006(Supplement 7)];3. Available from:
http://www.pediatriconcall.com/fordoctor/Conference_abstracts/
MAH_PEDICON2006/acute_severe_asthma.asp