"This is the first study to show that even mildly abnormal levels (of red blood cells) could be detrimental in elderly men undergoing major surgery," said Dr. Wen-Chih Wu of the Providence Veterans Affairs Medical Center and Brown University in Rhode Island.
A new study by researchers at the Providence Veterans Affairs Medical Center and The Warren Alpert Medical School of Brown University shows that older men, above the age of 65, whose red blood cell counts are even slightly out of the normal range are at higher risk of death and heart problems after major surgery.
Most surgical patients get a routine blood screening called a hematocrit to measure the number of red blood cells before they are operated upon. A reading that is too low points to anemia, while too high a reading is a sign of a condition called polycythemia. Elderly patients are more prone to both conditions. The elderly 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 post-operative heart attacks and other cardiac complications.
The new study found that the optimal hematocrit (a measure of red blood cells) for men over 65 was between 39 percent and 53.9 percent, and for every point above or below that normal range, a person's risk of dying within 30 days of non-heart-related surgery increased by 1.6 percent. That means someone with a preoperative hematocrit of 30 had a 14.4 percent higher risk of death than someone with a normal hematocrit level.
"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," said Dr.Wu. "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 pre-operative anemia and polycythemia and their effects on 30-day post-operative 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 non-cardiac surgery. These surgeries, which ranged from total knee replacements to prostate surgeries to hernia repairs, took place between 1997 and 2004 in 132 Veterans' Affairs Medical Centers across the United States.
Researchers used patients' pre-operative 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.
The result was a 1.6 per cent increase in the risk of death for every percentage point of deviation from the normal range for hematocrit levels.
Such an observational study does not reveal any cause-and-effect relationships between low or high hemocrit values and risk of side-effects after surgery, the researchers noted.