Killer Asthma


Vol. 15 •Issue 13 • Page 8
Killer Asthma

How to Treat ‘Shake-In-Your-Boots’ Asthma Patients

Years ago, while interning at a university medical center in Philadelphia, Mark Siegel, MD, witnessed security guards bringing an agitated patient into the emergency room. Left alone momentarily, the man promptly stood up and defecated on the examining table, Siegel recalled. He was then secured with four-point leather restraints.

“It turned out the man had status asthmaticus and was severely hypoxic,” Siegel, now a pulmonologist at Yale University School of Medicine, New Haven, Conn., told colleagues at the just-completed American Thoracic Society conference in Atlanta.

Agitation and combativeness only add to the imposing task of treating patients with life-threatening episodes of airway narrowing, often called status asthmaticus. What makes these attacks so dangerous is they often do not respond well to standard medical treatment. Every year, acute, severe asthma causes 5,000 deaths, one to two .million ER visits and 450,000 hospital ad.missions, according to the Department of Health and Human Services.

“They are the ‘shake-in-your-boots’ patients,” Colleen Lum Lung, RN, MSN, CPNP, declared at a recent asthma and allergy conference. “We see it primarily in patients who don’t get routine medical care,” mainly the uninsured who seek treatment in hospital emergency rooms.

Symptoms include mucus plugs that block airflow into air passages, causing atelectasis, hyperinflation of air sacs with CO2, increased airway resistance, decreased flow rates, increased work of breathing, and V/Q mismatch, Lum Lung said.

Previous near fatal attacks, recent discharge from hospital, inconsistent adherence to therapy, denial, and delay in seeking medical care mark those at highest risk of dying.

COMMON PROBLEMS

The elderly, the impoverished, females, blacks and Hispanics comprise most cases of severe asthma, but children are not immune.

“It’s a common problem” in the PICU at Alfred I. duPont Hospital for Children .in Wilmington, Del., according to James .Hertzog, MD.

“Patients most at risk include those who have had other episodes of status asthmaticus, prior ICU admissions for asthma, a .history of tracheal intubation, or a recent history of increasing steroid use,” explained Hertzog, an intensivist in duPont Hospital’s Department of Anesthesiology and Critical Care Medicine.

Warning signs of a severe asthma attack include a pulsus paradoxis greater than 20. “Asthma causes air trapping in the lungs. That can restrict blood flow in the heart, making it harder to pump blood out,” Hertzog reasoned.

Never underestimate asthma severity, delay treatment or under-use corticosteroids, Lum Lung urged. And fine-tune your patient assessment skills. Many patients in danger of a serious asthma attack have a pensive look. Ask them to count to ten to see if they get the words out clearly or if they can only whisper. Nasal flaring during inspiration is a good indicator. Curiously, though, wheezing is the least sensitive indicator. “Beware the quiet chest,” she warned.

RESORTING TO INTUBATION

When a patient presents to the ER with status asthmaticus, inhaled therapy “is really the cornerstone of our initial approach,” Hertzog emphasized. “It’s usually routine to start inhaled albuterol and give repeated treatments over an hour. It’s practically the same as continuous treatment with albuterol.”

Many steps occur between administering inhaled therapy and resorting to intubation and mechanical ventilation, but, as a general rule, when a patient becomes so fatigued respiratory failure is imminent, Hertzog brings out the ventilator. He weighs the decision carefully though.

“Ventilating an asthmatic can be a frightening and challenging situation,” he ob.served. “You do it before the situation becomes uncontrolled. They may be acidotic, borderline hypoxemic. There is a fine line between how soon is too soon and how late is too late.”

USUALLY COMBATIVE

Pediatric patients present special challenges because they are usually combative, making tracheal intubation a real effort, Hertzog told ADVANCE. “We usually use sedative anesthetics and neuromuscular blocking agents,” he explained. “We need people who are comfortable administering those medications.”

After deciding to intubate and ventilate, caregivers have a variety of options. “The bottom line is to find a mode least likely to cause high inflating pressures and barotrauma,” he said.

To avoid barotrauma, some clinicians will use a volume-control mode, he said, “but the concern there is that peak inspiratory pressure is not controlled, so people who use it use relatively low tidal volumes, usually 6 to 8 ml per kilo. Most like pressures less than 35 to 40 cm/H2O.”

Many practitioners are using pressure-control mode these days to protect against high peak inspiratory pressures, “but the downside of that mode is that with changing compliance, minute ventilation may vary,” he added.

INTUBATION INDICATIONS

Obvious indications for intubation in this patient population include apnea, hypopnea and cardiopulmonary arrest, Melissa K. Brown, RRT, told therapists at the AARC International Congress last year in San Antonio.

Beyond these, however, “the indications for mechanical ventilation have changed dramatically,” she said.

For instance, intubation and mechanical ventilation may be warranted if a patient has severe dyspnea and respiratory acidosis, that is a PaCO2 >55 mm Hg and pH <7.28, unrelieved by aggressive medical therapy. Altered mental status and other signs of clinical deterioration may also indicate a need for mechanical ventilation.

On the other hand, hypoxia and increasing hypercapnia alone are not sufficient to justify intubation, Brown said. Remember: intubation is risky. About 18 percent of ventilated asthma patients suffer tension pneumothoraces, according to one report, and many others contract nosocomial pneumonia.

The endotracheal tube is a “pathway for pathogens,” Brown, of Sharp Mary Birch Hospital for Women, San Diego, Calif., reminded her listeners.

ALTERNATIVES

Non-invasive ventilation is one possible alternative to mechanical ventilation in cases of severe asthma.

Continuous positive airway pressure (CPAP) decreases airway resistance, causes bronchodilation and rests the inspiratory muscles, among other benefits, Brown explained. On the down side, CPAP makes it hard to deliver aerosolized medications and “not all patients will wear masks,” she said. “Some find them claustrophobic.”

Many clinicians today try BiPAP before intubating the patient, depending on the severity of the case, Hertzog added.

“We don’t have great experience with it, but there is some encouraging evidence it can adequately ventilate in certain circumstances,” he said. “Certainly it can avoid tracheal intubation and its associated risks. It’s more comfortable for patients. However, it may be insufficient. If you do BiPAP, you need ready access to facilities for tracheal intubation, should the patient deteriorate.”

HELIUM-OXYGEN

Helium-oxygen mixtures, delivered either when the patient is breathing spontaneously or through an endotracheal tube, also beckon as an alternative to mechanical ventilation. Barach first described the technique in 1935.

With a density lower than nitrogen and oxygen, helium-oxygen mixtures can reduce work of breathing by increasing expiratory flow, may prevent respiratory muscle fatigue and can help stave off respiratory failure in non-intubated patients who are given standard oxygen therapy, Brown pointed out.

Helium-oxygen mixtures do not “interact with any other gas in the body,” she said. “They just buy us time until the other therapies kick in.”

Brown said she has treated asthmatics successfully with as little as 40% helium (60% O2) and cited one 1999 study documenting positive results with only 20% helium (80% O2).

The usefulness of helium/oxygen mixtures rests solely on how much supplemental O2 a patient needs, Herzog stressed. “You can’t use more than about 30 to 40 percent oxygen in the mixture,” he said. “More than that defeats the purpose. But that percentage may not be enough oxygen for some patients.”

With any treatment, the earlier begun, the better the outcome. Patient education can literally make the difference between life and death. “Providers need to craft a written personal management plan,” Lum Lung concluded. “It should include specific dosages of prednisone and criteria for when to introduce or increase the prednisone dosage. It should also contain criteria to indicate when a patient should immediately phone the doctor.”

You can reach Michael Gibbons at mgibbons@merion.com.

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