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MI risk after orthopedic surgery, and more.


MI risk higher after total hip, knee replacement

Patients who have total hip or total knee replacement surgery are at higher risk for myocardial infarction (MI) afterward, according to a recent study.

Researchers performed a retrospective cohort study using data from national registries in Denmark to compare the timing of MI in patients who had total knee or total hip replacement with that of matched controls. Patients who had a primary total knee or total hip replacement surgery from Jan. 1, 1998 through Dec. 31, 2007 were each matched by age, sex and geographic region with three controls who had not had surgery. Controls and patients were all followed for acute MI. Hazard ratios (HRs) were calculated and adjusted for disease and medication history. The study results were published in the Sept. 10 Archives of Internal Medicine.

A total of 95,227 patients were included in the study, 66,524 who had total hip replacement and 28,703 who had total knee replacement. They were matched with 286,165 controls. Total hip patients had a mean age of 71.9 years, and 39.6% were men; total knee patients had a mean age of 67.2 years, and 37.6% were men.

Within the first two weeks after surgery, total hip patients and total knee patients had a higher risk for MI compared with controls (adjusted HRs, 25.5 and 3.09, respectively). Total hip patients continued to have an elevated risk two to six weeks after surgery (adjusted HR, 5.05), but risk in total knee patients did not differ from controls after two weeks had passed. Total hip patients had an absolute six-week risk for MI of 0.51%, compared with 0.21% in total knee patients.

The authors noted that they did not have data on other risk factors for acute MI, such as body mass index and smoking; inpatient use of anticoagulant medications; or use of general anesthesia, among other limitations. However, they concluded that compared with controls, patients who undergo total hip or total knee replacement surgery have a much higher risk for acute MI within the first two postoperative weeks.

“Risk assessment of [acute] MI should be considered during the first 6 weeks after THR surgery and during the first 2 weeks after TKR surgery,” the authors wrote.

An accompanying commentary pointed out that cardiac risk is higher in general after surgery and said that physicians must actively work to decrease that risk. “It is important for physicians caring for patients in the perioperative period to recognize the potential for cardiac morbidity and mortality and then appropriately use the armamentarium of medical therapies we now have to reduce cardiac risk, prevent perioperative MIs, and prevent cardiac deaths,” the commentary author wrote.

Stroke severity affects accuracy of hospital rankings

Ratings of hospitals' stroke care are more accurate when stroke severity is included as a factor, a recent study found.

Researchers used data from 782 hospitals participating in Get With The Guidelines-Stroke to compare two hospital ranking systems—one that included scores on the National Institutes of Health Stroke Scale (NIHSS) and one that used just claims data to evaluate hospitals based on patients' 30-day mortality after stroke. Scores and other data for more than 125,000 Medicare beneficiaries who had an ischemic stroke between April 2003 and December 2009 were used.

The study was published in the July 18 Journal of the American Medical Association.

In total, 14.5% of the patients died within 30 days of their strokes, including 5.8% who died during hospitalization. The model that used NIHSS scores to adjust for stroke severity showed significantly better discrimination than the one that didn't (C statistic, 0.864). Of the hospitals that the no-NIHSS model rated as having “worse than expected” mortality, more than 50% were reclassified as having “expected” mortality when the severity score was included.

Overall, more than 40% of the hospitals that were in the top or bottom 5% under the no-NIHSS model would move out of those categories when NIHSS was considered. When the top and bottom 20% were assessed, about one-third of the hospitals would change ranking categories after inclusion of NIHSS.

Study authors noted that Medicare is currently considering a measure assessing 30-day mortality after ischemic stroke, and “this study suggests that inclusion of admission stroke severity may be essential for optimal ranking of hospital[s].”

In order to implement such a system, more hospitals will need to collect severity data, however, since an NIHSS score was recorded for only 50% of ischemic stroke patients during the study period.

If severity is not considered, hospitals may be tempted to turn away or transfer patients with more severe strokes, the authors said. Claims data alone may be effective for assessing hospitals' care for heart failure, myocardial infarction and pneumonia patients, but this study's findings show that ischemic stroke is different, they concluded.

An accompanying editorial suggested that factors other than mortality should also be considered in hospital rankings, since functional outcomes are extremely important to stroke patients.