Journal watch: Recent studies of note

Recent studies of note.

Paper summarizes best evidence on managing heart disease patients undergoing elective GI procedures

The latest evidence on the management of patients with atherosclerotic coronary disease undergoing elective endoscopic gastrointestinal procedures is summarized in a collaborative white paper by the American College of Cardiology and the American College of Gastroenterology.

The paper summarizes the evidence for risk of hemorrhagic and thrombotic events associated with elective endoscopic GI procedures in heart disease patients, particularly those with stents. The authors examined the potential risks of interrupting platelet-directed pharmacotherapy for five or more days before or after the procedure and offer advice on how to identify patients at highest risk. The paper was published in the Dec. 8, 2009 Journal of the American College of Cardiology.

A thienopyridine is the standard of care for platelet-directed pharmacotherapy with aspirin among patients with acute coronary syndrome or those undergoing percutaneous coronary intervention (PCI) and stent placement, the paper concluded. The authors recommended deferring elective endoscopic procedures in the first six to 12 months after PCI with drug-eluting stent insertion. Procedures scheduled beyond six months, especially if associated with high bleeding risk, could go forward five to seven days after thienopyridine drug cessation, and aspirin should be continued if possible.

Other evidence presented in the paper includes

  • Once hemostasis has been achieved after a procedure, a thienopyridine can be resumed with or without an initial oral loading dose, depending on risk for thrombosis and delayed bleeding. Continue platelet-directed pharmacotherapy for patients with a low risk for bleeding.
  • Bridging with anticoagulants is not supported by evidence. Eptifibatide is the only available platelet antagonist that could be used but evidence-based recommendations are not available.
  • Avoiding excessive tissue injury during procedures and using sound technical skills and good clinical judgment lowers the potential for complications associated with high-risk endoscopic procedures.

Bleeding risk after MI increases with number of antithrombotic agents given

The risk of bleeding increases with the number of antithrombotic agents used in patients with myocardial infarction, a recent study found.

Researchers studied more than 40,000 patients age 30 or older admitted to hospitals in Denmark between 2000 and 2005 for first-time myocardial infarction (MI). During a mean follow-up of 476.5 days, 4.6% of the patients were admitted with bleeding. The annual incidence of bleeding increased with the number of agents prescribed, with the highest risk in the groups taking aspirin plus vitamin K antagonist or triple therapy including clopidogrel. In addition, almost 38% of patients with nonfatal bleeding had recurrent MI or died during the study period compared with 18.4% without nonfatal bleeding. The results appeared in the Dec. 12, 2009 The Lancet.

The study also found that aspirin plus clopidogrel was associated with an increased risk of bleeding compared with aspirin alone, regardless of whether patients had percutaneous coronary intervention. Treatment with a vitamin K antagonist alone was not associated with an increased risk compared with aspirin alone, the authors said, but the result might be influenced by the fact that many participants taking vitamin K antagonists were already taking the drug at the time of MI.

The authors acknowledged the limitations of an observational study and noted that they had no knowledge of why physicians prescribed different combinations of antithrombotic agents. However, the findings suggest that a thorough individual risk assessment and careful consideration of the risk-benefit ratio precede any decision to prescribe triple or dual therapy with clopidogrel plus vitamin K antagonist, they concluded.

New estimates on cancer risk posed by CT scans

Two new studies warn of the cancer risk posed by computed tomography scans and suggest some risk-reduction strategies.

A retrospective cross-sectional study calculated the radiation doses delivered by computed tomography (CT) scans performed at four different California hospitals. Doses ranged from 2 millisieverts (mSv) for a routine head CT to 31 mSv for a multiphase abdomen and pelvis scan. Many of the scans provided more radiation than is usually assumed to be the case; the median dose for a routine abdomen and pelvis scan was 66% higher than the expected 8 to 10 mSv. Even within each type of study, the effective dose varied significantly within and among the hospitals. There was a mean 13-fold variation between the highest and lowest doses for each procedure.

Extrapolating from these data, researchers calculated cancer risks, including that one in 270 women who underwent CT coronary angiography at age 40 would develop cancer from the scan. Risks were lower for men than women, and higher for younger than older patients (20-year-olds faced double the risk, 60-year-olds only half). The study was published in the Dec. 14/28, 2009 Archives of Internal Medicine.

Another study in the same issue used risk models to calculate how many cancers could eventually be attributed to CT scans based on current scanning rates. Overall, they estimated that 29,000 future cancers could be caused by CT scans performed in the U.S. in 2007. Scans of the abdomen and pelvis contributed the most to the tally, and one-third of the cancers would be due to scans performed on patients between the ages of 35 and 54.

The authors of the studies and an accompanying editorial offered a number of solutions to this problem, including standardized protocols (such as have been applied to mammography), fewer multiple series examinations, dose reduction and registration, and greater use of American College of Radiology accreditation and criteria. The experts also called for a reduction in the number of inappropriate and unnecessary CT scans.

Rapid screening, decolonizing can reduce surgical-site infections from S. aureus

Hospitals can lower the number of surgical-site infections acquired in their facilities by rapidly screening and decolonizing nasal carriers of non-methicillin-resistant Staphylococcus aureus at admission, a new study found.

In a randomized, double-blind, placebo-controlled trial, researchers screened 6,771 Dutch patients upon admission to one of five hospitals from October 2005 through June 2007. Of the 917 patients with positive nasal swabs for S. aureus who were enrolled in the intention-to-treat analysis, 808 had a surgical procedure done. Five hundred and four patients were decolonized with mupirocin nasal ointment and chlorhexidine gluconate soap, and 413 patients were given placebo. The study was published in the Jan. 7 New England Journal of Medicine.

In the mupirocin-chlorhexidine group, the rate of S. aureus infection was 3.4%, compared with 7.7% in the placebo group (relative risk, 0.42; 95% CI, 0.23 to 0.75). Mupirocin-chlorhexidine appeared most effective for deep surgical-site infections, with 0.9% of patients infected in the treatment group versus 4.4% in the placebo group (RR, 0.21; 95% CI, 0.07 to 0.62). All-cause, in-hospital mortality didn't differ between the two groups, but time to onset of nosocomial infection was shorter in the placebo group (P=0.005). Mean duration of hospitalization was also significantly shorter in the treatment group (crude estimate, 12.2 vs. 14.0 days; P=0.04). The number of S. aureus carriers who would need to be screened to prevent one hospital-acquired S. aureus infection was 250; the number needed to treat was 23.

The study results indicate that S. aureus decolonization has a preventive effect, reducing the risk of hospital-associated S. aureus infection by nearly 60%, the authors said. An important aspect of the study was use of real-time polymerase chain reaction assay to detect nasal carriage of S. aureus, which allowed targeted treatment to start within 24 hours—i.e., before patients were exposed to risk factors for hospital-acquired S. aureus, they noted. Also important was the decontamination of skin as well as nasal passages, and continuation of treatment for five days, even when surgery was done during the course of treatment, they said. Treatment was repeated three and six weeks after admission for patients still in the hospital, they said.

S. aureus is responsible for a minority (approximately 20% to 30%) of surgical-site infections, albeit an important subgroup of them, an editorialist noted.

The study results suggest using prophylaxis for S. aureus carriers who will undergo surgical procedures associated with a high risk of harmful outcomes if an infection develops at the site—i.e., open-heart surgery, or any procedure in which a foreign body is placed, he said. Immunosuppressed patients should also use prophylaxis, the editorialist said.

Chlorhexidine-alcohol superior to povidone-iodine for surgical-site antisepsis

Cleaning patients' skin with chlorhexidine-alcohol before surgery is about 41% more protective against surgical-site infection than using povidone-iodine, a study found.

In a prospective, randomized trial, researchers assigned patients undergoing clean-contaminated surgery at one of six hospitals to preoperative chlorhexidine-alcohol skin scrub (409 patients), or povidone-iodine scrub and paint (440 patients). The former had their skin scrubbed with an applicator containing 2% chlorhexidine gluconate and 70% isopropyl alcohol, and the latter were scrubbed and painted with an aqueous solution of 10% povidone-iodine. The trial, published in the Jan.7 New England Journal of Medicine, was conducted between April 2004 and May 2008.

The chlorhexidine-alcohol group had a surgical-site infection rate of 9.5%; the rate for the povidone-iodine group was 16.1%, a significant difference (relative risk, 0.59; 95% confidence interval, 0.41 to 0.85; P=0.004). The former was more protective against superficial incisional infections (4.2% vs. 8.6%, RR, 0.48; 95% CI, 0.28 to 0.84; P=0.008) and deep incisional infections (1% vs. 3%, RR, 0.33; 95% CI, 0.11 to 1.01; P=0.05), though not organ-space infections (4.4% vs. 4.5%) or sepsis from surgical-site infection. Kaplan-Meier estimates also showed a significantly longer time to infection after surgery in the chlorhexidine-alcohol group (P=0.004).

The superior protection of chlorhexidine-alcohol is due mostly to its efficacy in reducing rates of superficial and deep incisional infections caused mainly by gram-positive skin flora, the authors said. Two-thirds of surgical-site infections are confined to the incision, they added, so “optimizing skin antisepsis before surgery could result in significant clinical benefit.” An editorialist agreed, saying the accumulated evidence from this and other studies suggests chlorhexidine-alcohol should replace povidone-iodine as the standard for preoperative surgical scrubs.