|
LITERATURE
MONITOR: A REVIEW
OF RECENTLY PUBLISHED
CLINICAL ARTICLES
BREATHING
PATTERNS PREDICT HEART FAILURE OUTCOME
Daytime oscillatory breathing
patterns are common among patients with chronic heart failure, and they
appear to be associated with a poor outcome and an increased prevalence
of ventricular arrhythmias, according to a report in a recent issue of Circulation.
Power spectral analysis was applied to 30-minute recordings of respiration in 74 patients with stable chronic heart failure. Heart rate and blood pressure were monitored continuously, and peripheral chemosensitivity was measured by inducing transient hypoxia (via nitrogen inhalation).
Oscillatory breathing--rises and falls in ventilation with apnea (Cheyne-Stokes respiration) or without apnea (periodic breathing)--were found in 22 and 27 patients, respectively. These respiratory patterns were significantly associated with more advanced heart failure symptoms, impaired autonomic balance, and increased chemosensitivity.
Over half the patients with either Cheyne-Stokes respiration (53%) or periodic breathing (52%) had nonsustained ventricular tachycardia, compared with only 10% of those with normal respiratory patterns. The two-year survival rate was lower in patients with oscillatory respiratory patterns (67%) than in patients with normal breathing patterns (96%), the researchers found.
Eight patients with reproducible oscillatory breathing received 100% oxygen delivered via face mask for 20 minutes. Oxygen exposure abolished the oscillations in seven of the patients, but breathing abnormalities resumed within 20 minutes when the patients again breathed room air. Similarly, dihydrocodeine administration decreased peripheral chemosensitivity by 42%, and this fall correlates with improvement in the respiratory pattern. Thus, "modulation of peripheral chemosensitivity could be a therapeutic option in [chronic heart failure] patients with cyclical breathing," the researchers noted.
The patients with Cheyne-Stokes respiration and the patients with periodic breathing were not significantly different in terms of clinical parameters, autonomic indices, or peripheral chemosensitivity. The researchers hypothesized that these oscillatory breathing patterns "represent two aspects of the same phenomenon (which could be referred to as cyclical respiration), with similar pathophysiologic mechanisms involved." In fact, some of the patients alternately showed Cheyne-Stokes respiration or periodic breathing on consecutive visits.
Ponikowski P, Anker SD, Chua
TP, et al. Oscillatory breathing patterns during wakefulness in patients
with chronic heart failure: clinical implications and role of augmented
peripheral chemosensitivity. Circulation. 1999;100:2418-2424.
PNEUMONIA
IN THE ELDERLY: WHICH DRUGS ARE BEST?
Three antimicrobial regimens
can markedly decrease 30-day mortality in elderly patients hospitalized
with pneumonia, researchers reported in a recent issue of the Archives
of Internal Medicine. "These findings suggest that opportunities
exist to dramatically improve the quality of care for hospitalized elderly
patients with pneumonia by modifying existing initial antimicrobial prescribing
practices," the researchers noted.
The findings are based on medical records from 12,945 Medicare recipients who were hospitalized with pneumonia. The study population was divided into subgroups based upon whether they lived in the community before hospitalization (9,751) or were admitted from a long-term care facility (3,194 subjects). Patients who were initially treated with a nonpseudomonal third-generation cephalosporin served as the reference group.
When all patients were evaluated, three regimens were found to substantially lower 30-day mortality:
- A nonpseudomonal third-generation cephalosporin plus a macrolide reduced mortality by 26%.
- A second-generation cephalosporin plus a macrolide provided a 29% reduction.
- A fluoroquinolone alone produced a 36% reduction.
However, only 15% of the overall group were initially treated with one of these regimens. When community-dwelling patients alone were considered, only initial therapy with a nonpseudomonal third-generation cephalosporin plus a macrolide was independently associated with lower 30-day mortality; the other two antimicrobial regimens were associated only with a trend toward improved survival. Among the patients in the long-term care subgroup, no regimen was proved to lower mortality, but there was a trend toward improved survival in those given a fluoroquinolone alone or a second-generation cephalosporin plus a macrolide.
Interestingly, 30-day
mortality increased by 77% among patients treated with a ß-lactam/ß-lactamase
inhibitor plus a macrolide; this increase remained significant in both
patient subgroups. Although the cause of this increased risk could not
be determined from the data in this study, the researchers believe the
finding "raises concerns for use of this regimen."
Gleason PP, Meehan TP, Fine
JM, et al. Associations between initial antimicrobial therapy and medical
outcomes for hospitalized elderly patients with pneumonia. Arch Intern
Med. 1999;159:2562-2572.
NEW PROGRAM
IMPROVES ACUTE ASTHMA CARE
An emergency department asthma
program achieved sustained improvements in clinical indicators of acute
asthma care, a new study has found. "Success in changing clinical practice
may have important financial and clinical research implications, in addition
to the primary goal of improving care," the study authors suggested
in a recent issue of the Annals of Emergency Medicine.
Because previous studies have shown poor compliance with recommendations made by the National Institutes of Health's National Asthma Education Program, the researchers designed a guideline-centered acute asthma care program for use in an urban teaching hospital. Before the program was initiated, the hospital had low compliance with the following national guidelines: documentation of peak expiratory flow rate, prompt ß-agonist administration, and timely administration of corticosteroids.
The study population included almost 200 adult patients (ages 18 to 64 years) who presented to the emergency department with acute asthma; the care given to 51 patients who presented during the month before initiation of the program was compared with that provided to 145 patients treated during three separate months after the program's initiation.
Following the program's start, documentation of initial peak expiratory flow rate increased fourfold, and documentation of response to therapy rose threefold. In addition, the time to ß-agonist administration decreased significantly. Although the percentage of patients who received systemic corticosteroids did not change during the study period, the doses were given approximately 34 minutes sooner after the program was launched.
Furthermore, the median length of stay in the emergency department decreased by 58 minutes; there was also a trend toward decreased inpatient admission. No increase in four-week relapse rates was noted.
The program's success "has prompted development of a hospital-wide asthma quality improvement program, an adult asthma critical pathway, and several asthma research initiatives," according to the researchers. The impact of the program on resource utilization and cost was not evaluated in this study.
Emond SD, Woodruff PG, Lee
EY, et al. Effect of an emergency department asthma program on acute asthma
care. Ann Emerg Med. 1999;34:321-325.
SPUTUM
INDUCTION CAUSES OXYGEN DESATURATION
A transient but self-reversing
oxygen desaturation is found in asthmatic patients, smokers, and even in
healthy subjects when sputum is induced by hypertonic saline inhalation.
Although the procedure is well-tolerated in all three populations, the findings,
recently published in Chest, suggest that hypoxemic patients require
SaO2 monitoring during sputum induction.
Inhalation of hypertonic saline
has been proposed as a noninvasive alternative to bronchoscopy when secretions
and inflammatory cells must be collected from the airways of asthmatic
patients or smokers. However, this procedure induces bronchoconstriction
in patients with bronchial hyperreactivity. In addition, its safety in
smokers and its effects on SaO2 in both asthmatic patients and smokers
have not been evaluated.
The study population consisted of 14 lifetime nonsmokers with bronchial asthma, 14 patients with a history of five to 80 pack-years of smoking, and a control group of nine healthy lifetime nonsmokers. All of the study subjects inhaled a nebulized solution of 3% hypertonic saline for five minutes and were encouraged to expectorate sputum into a container at any time during and at the end of each session. The inhalation was continued until a reliable sample of sputum was obtained or until a maximum of 30 minutes had passed. The asthmatics were pretreated with 200 µg inhaled albuterol, and pulmonary function was continuously monitored during the induction procedure.
No significant between-group differences in the mean fall in FEV1 were found after saline solution inhalation: 1.36% in asthmatic patients (after the administration of albuterol), 7.58% in smokers, and 0.05% in healthy subjects. Interestingly, none of the asthmatic patients developed excessive bronchoconstriction, as had been feared. However, the researchers noted that one of the smokers (who had a smoking history of 60 pack-years) experienced severe bronchoconstriction, with a fall in FEV1 of 20.1%. This condition rapidly reversed itself following albuterol inhalation.
All three groups showed a significant fall in SaO2 during the induction procedure compared with baseline values, but there were no significant between-group differences in the mean magnitude of this decline: 6.0% in asthmatics, 5.3% in smokers, and 6.0% in healthy subjects. All subjects experienced recovery of SaO2 within five minutes after cessation of the procedure. Furthermore, the groups had similar mean durations of the overall sputum induction procedure, of the mild-to-moderate desaturation, and of the severe desaturation.
The most common side effects
were slight nausea with retching and an unpleasant, salty taste. However,
"no subject developed sufficiently severe side effects to warrant
premature interruption of the procedure," the researchers noted.
Castagnaro A, Chetta A, Foresi
A, et al. Effect of sputum induction on spirometric measurements and arterial
oxygen saturation in asthmatic patients, smokers, and healthy subjects.
Chest. 1999;116:941-945.
|
|
