Management of Acute Asthma

							Management of Acute
     Asthma


        Ri 李佳舫
     Date: 12/24/2007
                  Asthma
• Chronic Inflammatory disorder of bronchi
  characterized by Episodic, reversible
  bronchospasm resulting from an
  exaggerated bronchoconstrictor response
  (hyperreactivity) to various stimuli (allergy)
• Hyperreactivity  obstruction of airways,
  severity widely variable in the same
  individual
• Affects 10% of children & 5%-7% adults
                                       Allergen
                   Macrophage/
                   dendritic cell                      Mast cell


                   Th2 cell                                            Neutrophil

                                                  Eosinophil
                    Mucus plug
                                                       Epithelial shedding
                                    Nerve activation


                                                                              Subepithelial
                                                                              fibrosis
                                    Plasma leak
                                                                             Sensory nerve
                                     Oedema                                  activation
                 Vasodilatation                                               Cholinergic
Mucus            New vessels                                                  reflex
hypersecretion
Hyperplasia                                                    Bronchoconstriction
                                                               Hypertrophy/hyperplasia

   Asthma airway obstruction, hyperinflation, and airflow limitation
   Airway remodeling: Subepithelial fibrosis, Sm m. hypertrophy, submucosal gl
            hypertrophy, airway wall thickening
       Emergency Department
           Management
• History:
 -- Recent ER visit, current oral corticosteroid use
  AE
 -- Previous resp. failure, progressive worsening
 of symptoms, seizures with asthma attacks
  severe, potentially fatal asthma
        Emergency Department
            Management
• PE:
 -- Resp. distress at rest, difficulty in speaking in
 sentences, diaphoresis, agitation
 -- RR>28, HR>110, pulse paradoxus>25 mmHg
 -- Use of accessory muscles  severe airflow
 obstruction
 -- Presence of SCM / suprasternal retractions 
 impairment in lung function
Asthma Attack Evolution




               CHEST / 125 / 3 / MARCH, 2004
Thorax 2007;62;447-458
Thorax 2007;62;447-458
Thorax 2007;62;447-458
            ICU Management
• P’t simply require additional time for resp.
  function to improve
• In the past, mainstay of Rx for p’t progressing to
  resp. failure from asthma was intubation and
  mechanical ventilation
• Alternatives to intubation
   – NIPPV (Noninvasive Positive Pressure Ventilation)
   – Inhaled general anesthetics
   – Continuation of pharmacotherapy

                                    CHEST / 125 / 3 / MARCH, 2004
                    NIPPV
• Potentially beneficial effects result from
  – Reduction in the increased work of breathing
  – Decrease in inspiratory threshold load
• Demonstrated significant reductions in
  PaCO2 early in p’t with AA
• Improved lung function and decreased
  hospitalization rate


                                 CHEST / 125 / 3 / MARCH, 2004
                    NIPPV
• Successful use: first identified p’t as high
  risk, p’t education, coordination with
  breathing circuit
• If with only marginal improvement,
  removal may precipitate rapid deterioration
• Initial ventilator setting:
  – PEEP= 5 cmH2O
  – Pressure support= 8 cmH2O


                                CHEST / 125 / 3 / MARCH, 2004
                      NIPPV
• With largest possible ETT
• Mechanical ventilation follows
  cardiorespiratory collapse in approximately
  20% of episodes
  – Pulmonary hyperinflation, hypovolemia, sedation
   Slowly bagging (Apnea test), intravascular fluid
    supplement, sedation for synchronization of p’t with
    ventilation
• If p’t not improve with slow manual
  bagging tension pneumothorax s/b
  considered
                                     CHEST / 125 / 3 / MARCH, 2004
    Sedatives and
Neuromuscular Blockers
          • Usually concurrent
            opiate, morphine or
            fentanyl, is required for
            adequate sedation
          • Avoid NM blocker in p’t
            with asthma
             – Post-paralytic myopathy
          • Can be avoided if
            adequate sedatives and
            analgesics are given

                   CHEST / 125 / 3 / MARCH, 2004
       Take Home Message
• Determine the severity of attack gauge
  the response to treatment
• Initial Rx with oxygen, nebulised β-agonist
  and oral corticosteroid is sufficient
• NIPPV or ventilator may be required prior
  to treatment to optimize therapeutic
  outcome
Thank you for the attention!