PrimeCuts: This Week in the Journals

December 29, 2008

118px-times_square_ball.jpgCommentary by Sam Rougas MD, PGY-3 

Faculty Peer Reviewed

With the holiday season upon us, it seems we are always scrambling to find that perfect last minute gift for our loved ones. So, in the spirit of the season, here is a gift to those poor souls in the CCU. The New York Times commented on a recent study published in JAMA about the correlation between a lack of sleep and heart disease. It seems that patients who slept seven hours a night were less likely to develop coronary artery calcification than those who slept only five hours a night. While the study does show a relationship, the authors are quick to point out that there is no guarantee that it is causal. In any case, if an attending is wondering why you’re sleeping overnight, just say you’re keeping the census down.

Speaking of cardiology, ever wonder why some MI patients, despite optimum medical management with aspirin and Plavix develop cardiac complications and others do not? Well, the New England Journal of Medicine did. As it turns out, the answer may lay in the metabolism of clopidogrel and the CYP liver enzymes. Clopidogrel is a prodrug that must be metabolized in the liver to its active metabolite. Thus the presence of specific alleles may reduce the effectiveness of the medication. One study looked at genes that are known to be involved in the metabolism of clopidogrel in a group of French patients who had suffered either a STEMI or NSTEMI one year earlier. Patients with at least two CYP2C19 loss of function alleles had worse clinical outcomes than those without the allele, especially amongst patients who received PCI. It appears the mechanism of action of this allele is both quantitative and qualitative, meaning that there is not only less active metabolite, but also the active metabolite is less active. This was confirmed in a separate trial that took 162 healthy subjects and exposed them to clopidogrel. Patients with reduced function CYP2C19 had lower platelet inhibition and less active metabolite.  While this information is unlikely to change management in the emergency room immediately, it ultimately may affect dosing strategies among patients known to have this genetic variant.

As the saying goes, “an ounce of prevention is worth a pound of cure.” Never has this proven more true as in cancer prevention. In fact, cancer prevention either via screening or supplementation has captured the public’s attention. Several observational studies have hinted that vitamins may be a cancer prevention gold mine. However, there have been few randomized trials to back this up. In keeping with this, JAMA published two articles specifically regarding prostate cancer prevention, although they looked at all types of malignancies. The first trial, which compared vitamin E, selenium, and combination therapy among males aged 55 or over (50 or over if they were African American) found no reduction in the incidence of prostate cancer or total cancer. In fact, there was a non-statistically significant increase in prostate cancer among patients who only took vitamin E. Similar results were found in the second trial comparing vitamin E, vitamin C, and a combination among a group of male physicians aged 50 and over, though there was not a trend toward increased prostate cancer in the vitamin E group in this study. Nevertherless, while pessimists lamented the fact that the incidence of prostate cancer was not reduced, optimists were quick to point out that there were no reported cases of scurvy in the treatment group.

Most interns can rattle off the bacteria responsible for community acquired pneumonia on command, but what about the viruses? In Chest this month, researchers in Canada used highly sensitive nucleic acid amplification tests (NATs) to determine the incidence of viral pneumonia in the community. This study differed from the usual cohort of tests that are used including serology or direct antigen tests. Of the 193 patients enrolled in the study, only about 40% of the patients had any pathogen identified. Nearly 50% of those patients had an isolated bacterial infection and 30% had an isolated viral infection. The remaining patients had a combination of viral and bacterial pathogens. Among the viral infections, the most common included influenza A and B, human metapneumoviras, and RSV. While the paper does not offer information regarding the clinical utility of NATs in a hospital setting it does provide important information regarding the prevalence of common viral infections.

Now that it is college football bowl season, people are excited about the big showdown at Ohio State University. Researchers there pitted the heavily favored BiPAP machine against the more conventional CPAP machine in patients with obstructive sleep apnea and heart failure. The results which were published in CHEST revealed that after three months, BiPAP increased left ventricular ejection fraction by nearly 8% more than CPAP. Measurements of the apnea/hypopnea index (AHI) revealed no change in events between the two treatment modalities suggesting that BiPAP may be the better option6. However, fans of CPAP were quick to point out that only 24 patients were enrolled in the trial and more studies are necessary to draw definitive conclusions.

On a lighter note, the British Medical Journal published a Christmas special that compared ancient Homeric warfare to the modern emergency room. In the Iliad, a commander often would oversee the battle while specific generals fought specific battles. For example Agammemnon led the armies, while Hector and Achilles went toe to toe. In the ER, there is an attending (Agamemnon) overseeing the entire unit while the internal medicine/surgery docs fight there own specific battles. While this article has no clinical utility, it may provide the most important message of all . . . at the end of the day, were all just trying to get out alive. Happy Holidays folks.

 

Image courtesy of Wikimedia Commons

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