PRONE POSITIONING, INHALED NO MAY AID OXYGENATION IN ARDS

In patients with respiratory failure, early use of both prone positioning and inhaled nitric oxide (NO) improves oxygenation, a new study suggests. The two therapies appear to work synergistically and may optimize gas exchange in patients with acute respiratory distress syndrome (ARDS).

Johannigman et al evaluated the short-term effects of prone positioning and inhaled NO, alone and combined, in 16 patients with ARDS. Each patient was studied under four conditions:

• Mechanical ventilation; placement in the supine position.

• Mechanical ventilation plus inhaled NO (1 part per million [ppm]); placement in the supine position.

• Mechanical ventilation; placement in the prone position.

• Mechanical ventilation plus inhaled NO (1 ppm); placement in the prone position.

Compared with ventilation in the supine position, both prone positioning and inhaled NO increased the ratio of arterial oxygenation to inspired oxygen concentration (Pao2 /FIo2). Fourteen patients (87.5%) responded to prone positioning; the average increase in Pao2/FIo2 was 33%. Ten patients (62.5%) responded to inhaled NO (average increase, 14%). Fifteen patients (94%) responded to the combination of prone positioning and inhaled NO (average increase, 59%). Intracardiac shunt, pulmonary vascular resistance, and mean pulmonary artery pressure were also affected by patient positioning and inhaled NO administration (Table 1).

The authors note that they consider the use of prone positioning and inhaled NO to be adjunctive therapies for patients refractory to conventional therapy, and they point out that their study was not designed to evaluate long-term outcome.

Johannigman JA, Davis K Jr, Miller SL, et al. Prone positioning and inhaled nitric oxide: synergistic therapies for acute respiratory distress syndrome. J Trauma. 2001;50:589-596.

NON– Q- WAVE MI INCIDENCE RISES

The sharp declines in both the incidence of and mortality from myocardial infarction (MI) appear to be confined to Q-wave infarctions. Researchers from the University of Massachusetts Medical School have found that during the last two decades, the incidence of non–Q-wave MI has risen sharply and mortality has remained constant.

Furman et al examined 5,832 residents of Worcester, Massachusetts, who suffered first MIs between 1975 and 1997. They found that the incidence of Q-wave MI declined by more than one third in that time but the incidence of non–Q-wave MI almost doubled. The case-fatality rate for Q-wave MI decreased from about 24% to approximately 14%, while that for non–Q-wave MI remained unchanged at roughly 12%.

Increased use of thrombolysis and other therapies to treat MIs with ST-segment elevation is believed to be responsible for the encouraging decline in Q-wave MI fatalities.

However, some investigators have raised concern that it might have increased the incidence of non–Q-wave MIs by rapidly opening occluded coronary arteries and preventing Q-wave generation. To examine this possibility, the authors excluded from their analysis those patients who were given thrombolysis; even with this exclusion, the incidence of non–Q-wave MI rose over time. Furman and colleagues therefore concluded that non–Q-wave MI represents an ever-widening segment of overall MI incidence and that further understanding of how to address non–Q-wave MI is of paramount importance.

Furman M, Dauerman H, Goldberg R, et al. Twenty-two year (1975-1997) trends in the incidence, in-hospital and long-term case fatality rates from initial Q-wave and non–Q-wave myocardial infarction: a multi-hospital, community-wide perspective. J Am Coll Cardiol. 2001;37:1571-1580.

VACCINE AGAINST PNEUMOCOCCAL DISEASE IS EFFECTIVE, UNDERUSED

Despite the availability of a vaccine against Streptococcus pneumoniae, more than 60,000 cases of invasive pneumococcal disease still occur in this country every year. Some groups—including young children, the elderly, and black patients—remain disproportionately affected by this disorder. More than half of all cases, however, could be avoided if current vaccination guidelines were followed more closely.

Robinson et al used data from the nine-state Active Bacterial Core Surveillance/ Emerging Infections Program Network to identify cases of invasive pneumococcal disease. They found that in 1998 the overall incidence of invasive disease in this sample was 23.2 cases per 100,000 people; this translates to an estimated 62,840 cases in the United States each year.

Incidence per 100,000 people was highest at the extremes of age: 166.9 in children younger than 2 years and 59.7 among adults 65 years or older. As a result, 53% of all cases were found to occur in these two groups. Incidence also depended on race: 49.7 in blacks compared with 19.7 in whites.

Among patients ages 18 to 64 years, 59% had at least one condition that has been identified by the Advisory Committee on Immunization Practices (ACIP) as an indication for pneumococcal vaccination. Because the case-fatality rate for these patients was more than twice what it was for age-matched patients without an ACIP indication, the authors urge that a greater effort be made to vaccinate all appropriate patients. This should significantly reduce the incidence of the disease.

Robinson KA, Baughman W, Rothrock G, et al. Epidemiology of invasive Streptococcus pneumoniae infections in the United States, 1995-1998: opportunities for prevention in the conjugate vaccine era. JAMA. 2001;285:1729-1735.

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