June 12, 2007
Red Cells Count
Study Shows Pre-Op Hematocrit Affects Post-Op Outcomes
Elderly men with even slightly abnormal red blood cell counts have a higher risk of dying or having a serious cardiac event after major surgery, according to a new study conducted by researchers at the Providence Veterans Affairs Medical Center and The Warren Alpert Medical School of Brown University. Results are published in JAMA.
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PROVIDENCE, R.I. [Brown University] — Men over 65 with even slightly abnormal red blood cell counts – either too low or too high – are at greater risk of postoperative death or cardiac events following a major noncardiac surgery, according to a new study by researchers at the Providence Veterans Affairs Medical Center and The Warren Alpert Medical School of Brown University.
Elderly patients are at risk for abnormal hematocrit values, or the number of red cells in the blood. These red cell counts are often too low, causing anemia, or too high, a sign of a condition called polycythemia. Elderly people are more prone to both anemia and polycythemia because they are more likely to have health problems that affect red blood cells, such as kidney disease, gastrointestinal bleeding, malnutrition or cancer. The elderly are also more likely to have heart disease, which makes them more vulnerable to the stresses of surgery and puts them at greater risk of postoperative heart attacks and other cardiac complications.
But results from this new study, published in the June 13 issue of JAMA, are the first to show that even slightly abnormal preoperative red cell counts can have serious postoperative consequences. The results also bring new meaning to hematocrit tests: Even though virtually all patients get this screening before major surgery, doctors had little guidance on how to interpret test results that fall just outside the normal range.
“Even though hematocrit tests are nearly universal before elective surgery, doctors don’t have a reliable yardstick for gauging a normal or a mildly abnormal result. So the test, on many occasions, is not very helpful,” said Wen-Chih Wu, M.D., lead author of the JAMA article, assistant professor of medicine at The Warren Alpert Medical School of Brown University, and staff cardiologist at the Providence Veteran Affairs Medical Center. “One of my biggest hopes for this research is that it eventually helps doctors better interpret hematocrit test results to improve patient outcomes.”
Wu and his colleagues set out to evaluate the prevalence of preoperative anemia and polycythemia and their effects on 30-day postoperative outcomes for veterans. Wu and his team mined data from the Veterans Affairs National Surgical Quality Improvement Program to conduct their work, looking at medical data of 310,311 veterans aged 65 or older who underwent major noncardiac surgery. These surgeries, which ranged from total knee replacements to prostate surgeries to hernia repairs, took place between 1997 and 2004 in 132 Veteran Affairs Medical Centers across the United States.
Researchers used patients’ preoperative hematocrit screening results and a review of the scientific literature on hematocrit values to put patients into one of three categories: anemic (hematocrit values of less than 39 percent), normal (hematocrit values of between 39 and 54 percent) and polycythemic (hematocrit values of 54 percent or higher). Then, from each point deviation from normal, researchers estimated increases in the risk of death or cardiac events – mainly heart attack and cardiac arrest – 30 days after surgery.
Results were clear: For every percentage point of hematocrit deviation from the normal range, death and cardiac event rates rose by 1.6 percent. This increase in risk was significant and steady. For example, a patient with a preoperative hematrocrit value of 30 percent has a 14 percent increased risk of death 30 days after surgery while a patient with a preoperative hematrocrit value of 24 percent has a 24 percent increase in their risk of dying.
“We found that, in older men facing surgery, even a mild case of anemia or polycythemia can pose a problem,” Wu said. “The risk of death or a serious cardiac event started when hematrocrit values were 51 percent and higher – values that were previously considered normal.”
Wu said it was too early to tell if changes in medical care before or during surgeries – such as blood transfusions or iron supplements – could improve outcomes for the elderly with anemia. Right now, Wu and his team are currently studying the impact of different treatment options for the elderly with these low red blood cell counts.
Until those results are in, the current findings give doctors a better yardstick for measuring normal hematocrit values: “Some doctors may have different definitions of what a normal hematrocrit result is for a patient facing surgery. By looking at postoperative outcomes, this study redefined the concept of normal hematrocrit values. For elderly patients about to undergo major surgery, maintaining a normal red blood cell count may be beneficial.”
The research team from The Warren Alpert Medical School of Brown University included Charles Eaton, M.D., professor of family medicine and director of the Center for Primary Care and Prevention at Memorial Hospital of Rhode Island; Roy Poses, M.D., clinical associate professor of medicine; Satish Sharma, M.D., associate professor of medicine and chief of cardiology at the Providence Veterans Affairs Medical Center; Michael Vezeridis, M.D., professor of surgery and staff physician, Providence Veterans Affairs Medical Center; and Peter Friedmann, associate professor of medicine and community health, and director of the Program to Integrate Psychosocial and Health Services at Providence Veterans Affairs Medical Center.
Other members of the research team included Georgette Uttley, former surgical nurse at the Providence Veterans Affairs Medical Center; Tracy Schifftner and William Henderson with the Denver Veterans Affairs Medical Center and the University of Colorado Health Sciences Center; and Shukri Khuri, M.D. with the VA Boston Healthcare System and Harvard Medical School.
The U.S. Department of Veterans Affairs funded the research.
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