Volume 5, No. 8, September 2007
Abstract of the Month
Women's greater risk of dying after surgery: Transfusion-related immunosuppression
Women are more likely to die than men after surgery. A new study suggests it may be due to blood transfusion-related immunosuppression. Women tend to have lower hematocrit and hemoglobin than men and therefore are more likely to receive transfusions during surgery. Indeed, the study of Michigan Medicare patients found that women undergoing CABG were 3.4 times as likely to have received blood as men and generally received more units of blood (11.6 vs. 8.1), after accounting for factors such as age, race, and coexisting medical conditions. Patients who received transfused blood were nearly three times more likely to develop an infection than patients who did not (14.6 vs. 4.9 percent).
The prevalence of infection increased with the number of units (U) received during hospitalization from 13.6 percent for 1 to 4 U and 25.3 percent for 5 to 49 U to 30.8 percent for 50 to 99 U and 33.3 percent for 100 U or more. The risk of mortality attributable to female sex was 13.9 percent, but was no longer significant when adjusted for blood transfusion. Also, patients who received a transfusion were 5.6 times more likely to die within 100 days after surgery than those who did not receive a transfusion.
The risks of transmission of various infectious agents from allogeneic transfusion (from another individual with compatible blood type) are generally low. However, the presence of foreign leukocytes in donor blood may suppress the immune system of the recipient. Patients who have received nonleukoreduced blood are at increased risk of postoperative infections and multiorgan failure, explain the Michigan researchers.
The authors note that the United States has not adopted a universal leukoreduction policy and that by 2003, an estimated 70 percent of the nation's blood supply was leukoreduced. However, their findings were based on analysis of Medicare files of 9,218 Michigan patients hospitalized for CABG surgery from July 1, 1997 through September 22, 1998. The study was supported in part by the Agency for Healthcare Research and Quality (HS11540).
Rogers AM et al Allogeneic blood transfusions explain increased mortality in women after coronary artery bypass graft surgery December 2006 American Heart Journal 152, pp. 1028-1034
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd
=ShowDetailView&TermToSearch=17161047
OB/GYN CCC Editorial comment:
Postoperative infection is increased with allogeneic blood during surgery also
While most of our patients are not involved with CABG, per se, many of our inpatients are involved with other surgical procedures, e. g., cesarean delivery, vaginal delivery with repairs, or gynecologic surgery.
The immunosuppressive activity of allogeneic blood has been known since the studies on renal allograft survival were published in the 1970s. Increasing attention has been directed towards the impact of the immunosuppressive effect of allogeneic blood (particularly the leukocyte component) on postoperative infection, tumor recurrence, and nosocomial infection in critically ill patients. This phenomenon has been termed "transfusion-related immunomodulation" (TRIM).
Nosocomial infections
The evidence that postoperative infection is increased in patients receiving allogeneic blood during surgery is compelling, though not absolute, as are the data implicating the leukocyte as the "culprit".
In a review of the records of 416 consecutive patients undergoing coronary artery bypass at one medical center, the 64 patients developing postoperative pneumonia and/or wound infection received a significantly higher volume of allogeneic plasma than those not developing infection (mean ± SE: 957 ± 181 versus 321 ± 40 mL, respectively). However, on multivariate analysis, which included 25 confounding variables (eg, repeated surgery, endotracheal intubation, time on bypass pump), the association between infection and volume of infused allogeneic plasma was no longer statistically significant.
One study compared the incidence of postoperative infection in 50 patients receiving two or three allogeneic transfusions to that in 34 patients treated with autologous transfusions. Infection was much less frequent with autologous transfusions (three versus 32 percent).
Another report found that the incidence of postoperative infection was much lower in patients treated with leukocyte-depleted blood (two versus 23 percent with whole blood). Patients receiving whole blood had decreased natural killer cell function that may have contributed to the development of infection.
Several meta-analyses have been performed using slightly different approaches and have yielded conflicting results. Therefore, it is premature at this time to recommend routine use of leukocyte- depleted blood in order to diminish the risk of postoperative infections.
In summary, I am not suggesting that we abandon the successful use of leukoreduction to prevent complications of blood transfusion. Rather I submit that we need to be more circumspect each time we consider a transfusion in our post procedure patients. The risk of post procedure infection and even mortality need to be considered along with the other known risks of contamination with infectious agents, e. g., HIV, hepatitis, etc….when counseling our patients.
Other resources
HLA and ABO sensitization and desensitization in renal transplantation, UpToDate
http://www.uptodateonline.com/utd/content/topic.do?topicKey=renltran/6633
Leukoreduction to prevent complications of blood transfusion , UpToDate
http://www.uptodateonline.com/utd/content/topic.do?topicKey=transfus/4868
Taylor RW et al Red blood cell transfusions and nosocomial infections in critically ill patients. Crit Care Med. 2006 Sep;34(9):2302-8
Michalopoulos A et al Frequency, characteristics, and predictors of microbiologically documented nosocomial infections after cardiac surgery. Eur J Cardiothorac Surg. 2006 Apr;29(4):456-60
Shorr AF; Jackson WL Transfusion practice and nosocomial infection: assessing the evidence. Curr Opin Crit Care. 2005 Oct;11(5):468-72.
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OB/GYN
Dr. Neil Murphy is the Obstetrics and Gynecology Chief Clinical Consultant (OB/GYN C.C.C.). Dr. Murphy is very interested in establishing a dialogue and/or networking with anyone involved in women's health or maternal child health, especially as it applies to Native or indigenous peoples around the world. Please don't hesitate to contact him by e-mail or phone at 907-729-3154.
