Treatment of status asthmaticus

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Treatment of status asthmaticus

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Reference

• REVIEW SERIES
• The pulmonary physician in critical care
  12 Acute severe asthma in the intensive care
  unit
• Thorax 20035881-88
• Clinical review Severe asthma
• Critical Care 2002,630-44
• Pathogenesis and management of status asthmaticus
  in adults (2006 UpToDate )
• Mechanical ventilation in adults with status
  asthmaticus (2006 UpToDate)

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Status asthmaticus

• Severe attacks of asthma poorly responsive to
  adrenergic agents and associated with signs or
  symptoms of potential respiratory failure

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Treatment

• Administration of oxygen
• ß2-agonists (by continuous or repetitive
  nebulisation)
• Systemic corticosteroids
• Subcutaneous administration of epinephrine or
  terbutaline should be considered in patients
• not responding adequately to continuous
  nebulisation,
• unable to cooperate,
• Intubated patients not responding to inhaled
  therapy.
• Intubated and mechanically ventilated
• based mainly on clinical judgment
• should not be delayed once it is deemed necessary
• should be appropriately sedated
• Permissive hypercapnia, increase in expiratory
  time, and promotion of patient-ventilator
  synchronism

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Inhaled ß2-agonists

• Continuous or repetitive nebulisation of
  short-acting ß2-agonists
• the most effective means of reversing airflow
  obstruction
• More effective and induces less hypokalaemia when
  delivered by the inhaled route
• Salbutamol (albuterol) is the most frequently
  used agent because of its potency, duration of
  action (four to six hours) and ß2-selectivity
• 2.5 mg (0.5 ml) in 2.5 ml normal saline by
  nebulisation continuously or every 1520 min
  until a significant clinical response is achieved
  or serious side effects appear
• Intravenous administration should be considered
  in patients who have not responded to inhaled or
  subcutaneous treatment, in whom respiratory
  arrest is imminent

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Corticosteroids

• Should begin much earlier, at the first sign of
  loss of asthma control
• Early treatment with adequate doses of
  corticosteroid improves outcome
• Reduce mortality
• Controversy about the optimal dose of
  corticosteroid
• No particular advantage of the intravenous over
  the oral route provided there is reliable
  gastrointestinal absorption

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Ipratropium

• Ipratropium bromide has a mild additional
  bronchodilating effect when added to ß agonists
  that may only be significant in severe asthma
• Ipratropium bromide 0.5 mg by nebulisation every
  14 hours, combined with salbutamol

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Aminophylline

• The addition of aminophylline does not add to the
  bronchodilating effect of optimal doses of ß
  agonists
• Not recommended as a first line drug in acute
  asthma management
• Its inclusion as a second line agent is still
  debated

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Subcutaneous epinephrine and terbutaline

• Should be considered in patients
• not responding adequately to continuous nebulised
  salbutamol
• unable to cooperate
• intubated patients not responding to inhaled
  therapy
• 0.30.4 ml of a 11000 solution subcutaneously
  every 20 min for 3 doses

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Mechanical ventilation

• Cardiopulmonary arrest and deteriorating
  consciousness are absolute indications for
  intubation and assisted ventilation
• Hypercapnia, acidosis, and clinical signs of
  severe disease at presentation may not require
  immediate intubation before an aggressive trial
  of conventional bronchodilator therapy
• Conversely, progressive deterioration with
  increasing distress or physical exhaustion may
  warrant intubation and mechanical ventilation
  without the presence of hypercapnia

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Mechanical ventilation

• Correction of the hypoxemia is one of the first
  priorities
• To avoid further significant increase of lung
  hyperinflation
• Decrease of VE
• Increase of expiratory time
• Decrease of resistance
• Controlled hypoventilation (Permissive
  hypercapnia (PaCO2 does not exceed 90 mmHg) with
  an associated acidosis (pH 7.27.15) )
• Decreasing either the tidal volume or the
  respiratory frequency, or both
• The recommended strategy to reduce lung
  hyperinflation
• Pressure-controlled ventilation seems more
  appropriate to maintain airway pressure
  especially in status asthmaticus

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Mechanical ventilationInitial ventilator settings
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Mechanical ventilationSedation
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Mechanical ventilationNeuromuscular-blocking
agents

• Lessens the patient -ventilator asynchronism
• Lowers the risk for barotrauma
• Reduce oxygen consumption and dioxide production,
  and reduces lactate accumulation
• Disadvantages myopathy, excessive airways
  secretions, histamine release (atracurium), and
  tachycardia and hypotension (pancuronium).
• Currently the use of paralytics is usually
  recommended only in those patients who cannot
  adequately be controlled with sedation alone

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THERAPEUTIC OPTIONS IN THE NON-RESPONDING PATIENT

• Manual compression
• Mucolytics
• Inhalational anaesthetic agents
• Helium
• Magnesium sulphate
• Leukotriene inhibitors
• Platelet activating factor (PAF) inhibitors
• Nitric oxide (NO)

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Manual compression

• Hyperinflation is relieved by manual compression
  of the chest wall during expiration
• Has not been fully evaluated by a controlled
  clinical study in humans

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Mucolytics

• Chest physiotherapy and mucolytics have no proven
  benefit
• Bronchoscopic lavage with locally applied
  acetylcysteine may be used to help clear impacted
  secretions in selected refractory patients but
  its routine use is not advocated

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Inhalational anaesthetic agents

• Halothane, isoflurane, and sevoflurane are potent
  bronchodilators in asthmatic patients receiving
  mechanical ventilation who have failed to respond
  to conventional ß adrenergic agents
• Sevoflurane, a halogenated ether, is largely
  devoid of cardiorespiratory side effects and may
  be the preferred agent

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Helium

• A mixture of helium and oxygen (heliox) may
  reduce the work of breathing and improve gas
  exchange because of its low density that reduces
  airway resistance and hyperinflation
• However, the benefits are marginal and the
  concentration of inspired oxygen is consequently
  decreased
• The use of heliox to prevent intubation has not
  been studied
• But dyspnoea scores were improved in one study,
  possibly by reducing the work of breathing

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Magnesium sulphate

• Early anecdotal reports suggested benefit from
  intravenous magnesium sulphate, which has been
  inconsistently supported by randomised studies
• A significant benefit was recently observed in
  children receiving intravenous magnesium sulphate
  (40 mg/kg) during acute asthma attacks

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• Leukotriene inhibitors
• relatively minor role
• Platelet activating factor (PAF) inhibitors
• attenuate the late response in asthma but have
  limited clinical efficacy
• Nitric oxide (NO)
• weak bronchodilator effect.
• It dilates pulmonary arteries
• When inhaled, may improve ventilation/perfusion
  matching