The evaluation and management of acute, severe asthma

Inhalation of phosphine gas following a fire associated with fumigation of processed pistachio nuts

On December 10, 2009, a fumigation stack containing aluminum phosphide became soaked with rain water and caught fire at a pistachio processing plant in Kern County, California. Untrained plant personnel responding to the fire had exposure to pyrolysis by-products, particulates, and extinguisher ingredients. Ten workers taken for medical evaluation had respiratory and nonspecific systemic symptoms consistent with exposure to phosphine gas. Six of the 10 workers had respiratory distress, indicated by chest pain, shortness of breath, elevated respiratory rate, or decreased oxygen saturation. Recommendations are made for the management of similar illnesses and prevention of similar exposures.

Acute severe asthma: new approaches to assessment and treatment

The precise definition of a severe asthmatic exacerbation is an issue that presents difficulties. The term 'status asthmaticus' relates severity to outcome and has been used to define a severe asthmatic exacerbation that does not respond to and/or perilously delays the repetitive or continuous administration of short-acting inhaled beta(2)-adrenergic receptor agonists (SABA) in the emergency setting. However, a number of limitations exist concerning the quantification of unresponsiveness. Therefore, the term 'acute severe asthma' is widely used, relating severity mostly to a combination of the presenting signs and symptoms and the severity of the cardiorespiratory abnormalities observed, although it is well known that presentation does not foretell outcome. In an acute severe asthma episode, close observation plus aggressive administration of bronchodilators (SABAs plus ipratropium bromide via a nebulizer driven by oxygen) and oral or intravenous corticosteroids are necessary to arrest the progression to severe hypercapnic respiratory failure leading to a decrease in consciousness that requires intensive care unit (ICU) admission and, eventually, ventilatory support. Adjunctive therapies (intravenous magnesium sulfate and/or others) should be considered in order to avoid intubation. Management after admission to the hospital ward because of an incomplete response is similar. The decision to intubate is essentially based on clinical judgement. Although cardiac or respiratory arrest represents an absolute indication for intubation, the usual picture is that of a conscious patient struggling to breathe. Factors associated with the increased likelihood of intubation include exhaustion and fatigue despite maximal therapy, deteriorating mental status, refractory hypoxaemia, increasing hypercapnia, haemodynamic instability and impending coma or apnoea. To intubate, sedation is indicated in order to improve comfort, safety and patient-ventilator synchrony, while at the same time decrease oxygen consumption and carbon dioxide production. Benzodiazepines can be safely used for sedation of the asthmatic patient, but time to awakening after discontinuation is prolonged and difficult to predict. The most common alternative is propofol, which is attractive in patients with sudden-onset (near-fatal) asthma who may be eligible for extubation within a few hours, because it can be titrated rapidly to a deep sedation level and has rapid reversal after discontinuation; in addition, it possesses bronchodilatory properties. The addition of an opioid (fentanyl or remifentanil) administered by continuous infusion to benzodiazepines or propofol is often desirable in order to provide amnesia, sedation, analgesia and respiratory drive suppression. Acute severe asthma is characterized by severe pulmonary hyperinflation due to marked limitation of the expiratory flow. Therefore, the main objective of the initial ventilator management is 2-fold: to ensure adequate gas exchange and to prevent further hyperinflation and ventilator-associated lung injury. This may require hypoventilation of the patient and higher arterial carbon dioxide (PaCO(2)) levels and a more acidic pH. This does not apply to asthmatic patients intubated for cardiac or respiratory arrest. In this setting the post-anoxic brain oedema might demand more careful management of PaCO(2) levels to prevent further elevation of intracranial pressure and subsequent complications. Monitoring lung mechanics is of paramount importance for the safe ventilation of patients with status asthmaticus. The first line of specific pharmacological therapy in ventilated asthmatic patients remains bronchodilation with a SABA, typically salbutamol (albuterol). Administration techniques include nebulizers or metered-dose inhalers with spacers. Systemic corticosteroids are critical components of therapy and should be administered to all ventilated patients, although the dose of systemic corticosteroids in mechanically ventilated asthmatic patients remains controversial. Anticholinergics, inhaled corticosteroids, leukotriene receptor antagonists and methylxanthines offer little benefit, and clinical data favouring their use are lacking. In conclusion, expertise, perseverance, judicious decisions and practice of evidence-based medicine are of paramount importance for successful outcomes for patients with acute severe asthma.

Slow-responders to IV beta2-adrenergic agonist therapy: defining a novel phenotype in pediatric asthma

OBJECTIVES

While aerosolized administration of beta(2)-adrenergic receptor (beta(2)-AR) agonists is the mainstay of treatment for pediatric asthma exacerbations, the efficacy of intravenous (IV) delivery is controversial. Failure to demonstrate improved outcomes with IV beta(2)-AR agonists may be due to phenotypic differences within this patient population. Our hypothesis is that children who respond more slowly to IV beta(2)-AR agonist therapy comprise a distinct phenotype.

METHODS

Retrospective chart review of all children admitted to the ICU for status asthmaticus who were treated with IV terbutaline between December 2002 and September 2006.

RESULTS

Seventy-eight children were treated with IV terbutaline according to guidelines that adjusted the dose by clinical asthma score. After examining the histogram of duration of terbutaline infusions, a 48-hr cutoff was chosen to define responsiveness. Thirty-eight (49%) children were slow-responders by this definition. There were no significant differences in baseline asthma severity or severity on admission between the slow-responders and responders. Slow-responders required significantly higher total doses of IV terbutaline, higher maximum administration rates, and had longer ICU and hospital length of stay.

CONCLUSION

There were significant differences in outcomes between the responders and slow-responders without differences in acute or chronic illness severity. Other factors may have lead to slower response to IV beta(2)-agonist therapy.

Dyspnea

When evaluating a dyspneic patient in the office, a quick initial assessment of the airway, breathing, and circulation, while gathering a brief history and focused physical examination are necessary. Most often, an acute cardiopulmonary disorder, such as CHF, cardiac ischemia, pneumonia, asthma, or COPD exacerbation, can be identified and treated. Stable patients who improve can be sent home, but those in acute distress with unstable or impending unstable conditions need to be transferred emergently to definitive care. Because of the difficult logistics involved in attempting to work up an outpatient for new onset of SOB, some patients will need to be transferred to the nearest ED for a definitive diagnosis.

Protocol-based titration of intravenous terbutaline decreases length of stay in pediatric status asthmaticus

Although frequently used to treat status asthmaticus in children, intravenous (IV) terbutaline has not been shown to decrease hospital length of stay (LOS). We theorized that this lack of demonstrable benefit resulted from variations in dosing and titration, rather than the drug per se, and that intensive care unit (ICU) LOS would be shortened by the administration of terbutaline according to a protocol incorporating a quantitative assessment of severity of illness. We prospectively treated 20 consecutive children with status asthmaticus with IV terbutaline according to a protocol that titrated the dose based on a clinical asthma score, the Modified Pulmonary Index Score (MPIS). Data were compared to a historic cohort of the previous 20 consecutive ICU patients with status asthmaticus who were treated with IV terbutaline prior to initiation of the protocol. Patients who received terbutaline by standardized protocol had significantly shorter ICU LOS (3.5 +/- 1.1 vs. 5.0 +/- 2.0 days, P = 0.01), shorter hospital LOS (5.5 +/- 1.3 vs. 8.3 +/- 2.7 days, P < 0.01), and reduced hospital charges ($19,298 +/- $10,516 vs. $26,528 +/- $12,328, P = 0.04). The method of administration of IV terbutaline significantly influenced ICU length of stay and hospital charges.