Clinical Briefs

Hypoxemia Improves Efficiency of Supplemental Home Oxygen Prescribing

For patients who have resting hypoxemia, supplemental home oxygen (HO2) provides significant survival benefits and remains the only intervention proven to prolong the life of patients with COPD. Implementation of HO2 is costly, ranging from about $2000-6000 per year, totaling more than $1 billion annually for our nation. Ferro and associates postulated that use of a clinical pathway for identification and HO2 treatment of hypoxemic patients would improve the efficiency of HO2 prescribing.

Study subjects were all patients from the VA medical center of Albany New York, who had been referred for evaluation of need for HO2 in 1988-1989, 1990-1991, and 1992-1994. The last time period was immediately following implementation of a pathway for HO2 in this VA hospital system.

Patients needed to demonstrate a PaO2 of less than 55 (or < 60 with evidence of end-organ hypoxia), or oxygen saturation corresponding to that level of hypoxemia (SaO2 < 80% = PaO2 < 55).

The screening protocol to identify potential candidates for HO2 included any patient with an FEV1 less than 1000, impaired diffusing capacity, or abnormal lung volume; all these patients were sent for oximetry. Prior to the study, prescriptions for HO2 were written on a standard prescription, but the intervention included a customized form requiring checking a box documenting compliance with specific prescribing criteria, including plans for follow-up oximetries if patients failed to meet prescribing criteria.

In the year following the clinical pathway institution, there was a 25% decrease in the number of patients treated. Perhaps surprisingly, the total number of deaths decreased during this year, because of fewer deaths from advanced COPD. Ferro et al demonstrate that use of a clinical pathway can improve efficiency of HO2 use.

Ferro TJ, et al. J Clin Outcomes Man 1999;6(6):27-33.

Oral Androstenedione and Adaptations to Resistance Training in Young Men

Many young men ingest chemicals that they believe, sometimes correctly, enhance muscularity and strength. Androstenedione (ADSTE) is a testosterone precursor produced by the adrenals and converted into testosterone by 17-betahydroxysteroid dehydrogenase, an enzyme diffusely distributed throughout body tissues. ADSTE of plant origin has been marketed and is viewed by some as a natural anabolic steroid alternative. To date, no studies have been done in men to assess the effect of ADSTE on plasma testosterone, though a single small trial in women found substantial increases in testosterone following ADSTE ingestion.

In this study, 20 healthy young men consumed either ADSTE or placebo and had blood sampling for effect on free and total testosterone, LH, and FSH. Additionally, men were enrolled in a resistance exercise training program for eight weeks, using weight lifting three days per week.

Single-dose ingestion of ADSTE resulted in a prompt (within 1 hour) and sustained increase in plasma ADSTE, but had no measurable effect on free or total testosterone, LH, or FSH. Similarly, long-term (8 weeks) use of ADSTE produced no significant effect on testosterone. Additionally, no effect, either positive or negative, was seen upon strength or muscle mass.

Unfortunately, ADSTE use was associated with a significant reduction in HDL as well as an elevation of plasma estrogens estradiol and estrone, which have been associated with gynecomastia, as well as other health risks.

King and colleagues conclude that ADSTE does not provide testosterone enhancement or bolster muscular strength or mass, yet does induce other potentially deleterious changes.

King KS, et al. JAMA 1999;281:2020-2028.

Dietary Hydrogenated Fats on Serum Lipoprotein Cholesterol Levels

Trans-fatty acids are present in meat and dairy products as a result of bacterial fermentation that occurs in ruminant animals. They are also produced during the processing of vegetable oils by hydrogenation, which has been used to convert vegetable oils that are liquid at room temperature to a more solid or semisolid status. Products like margarine have been widely embraced by the American public in an effort to reduce calories and saturated fat, when compared with using butter. There has been the suggestion that trans-fatty acids are detrimental to serum lipids when compared to cis-fatty acids. The current study evaluated the effect of a variety of forms of margarine and vegetable shortening with diverse levels of trans-fatty acids when substituted for butter in controlled diets.

Men and women older than age 50 (n = 36) who were ostensibly healthy other than having modest elevations of LDL cholesterol (> 130 mg/dL) were fed controlled experimental diets for periods of 35 days. In each diet, 30% of calories were from fat; types of fat substituted included soybean oil, semiliquid margarine, soft margarine, shortening, stick margarine, and butter.

Dietary fat substitution with agents containing the lowest amounts of trans-fatty acids (i.e., soy and semiliquid margarine) were associated with the most favorable changes in LDL, VLDL, and the total cholesterol: HDL cholesterol ratio. Lichtenstein and associates conclude that the current recommendations to consider both the content of trans-fatty acids and saturated fat in dietary planning are appropriate.

Lichtenstein AH, et al. N Engl J Med 1999;340:1933-1940.