WEDNESDAY, Sept. 3, 2003 (HealthDayNews) -- Kidneys and other organs may suffer more damage than previously believed during the blood dilution that's routinely done on patients having coronary artery bypass surgery.
That warning comes from a Duke University Medical Center study in the September issue of the Annals of Thoracic Surgery.
This moderate dilution of blood is done to place the bypass patients on the heart-lung machine during their surgery. To prime the machine's pump, surgeons add fluid -- usually a saline solution -- to fill the machine's tubing and pumping chambers.
That added fluid dilutes the patient's blood and lowers the percentage of oxygen-carrying red blood cells in the blood, a measurement known as hematocrit. Normal hematocrit is about 36 percent to 40 percent but, during bypass surgeries, hematocrit may range from 22 percent to 26 percent. Lower percentages often occur at certain points of the surgery.
It's been believed that moderate dilution of the blood protects the kidneys from damage. But this study of more than 1,400 bypass patients found that blood dilution to the lower levels of accepted hematocrit is associated with measurable kidney damage.
"Using hematocrit as a tool to assess a patient's anemia, we found that the lowest hematocrit achieved during the bypass procedure was significantly associated with acute kidney damage. Furthermore, we found the risk to kidneys increases as a patient's body weight increases," study leader Dr. Mark Stafford-Smith says in a news release.
"This is the first report highlighting the association of hemodilution during bypass surgery with acute injury to the kidneys. Our findings question the wisdom of tolerating the lowest levels of hematocrit during bypass surgery," Stafford-Smith says.
He recommends surgeons pay more attention to shortening the bypass circuit or use smaller diameter tubing to reduce levels of blood dilution.
More information
Here's where you can learn more about coronary artery bypass surgery.
