Albumin--does the bell toll for thee?

White blood cell-containing allogeneic blood transfusion, postoperative infection and mortality: a meta-analysis of observational 'before-and-after' studies

BACKGROUND AND OBJECTIVES

An association of white blood cell (WBC) reduction with decreased mortality was reported by one observational, before-and-after study. A meta-analysis was undertaken to examine whether this finding is supported by all the evidence currently available from before-and-after studies, and whether these studies support an association of WBC reduction with a decreased risk of postoperative infection.

MATERIALS AND METHODS

Observational, before-and-after studies were retrieved that reported on postoperative infection and/or mortality between January 1997 and June 2003. Six studies met the criteria for meta-analysis. Unadjusted summary odds ratios (ORs) of postoperative infection or mortality in patients transfused after (compared with before) WBC reduction were calculated across the studies if the hypothesis of homogeneity was not rejected. Adjusted summary ORs were calculated across three studies that had reported multivariate analyses.

RESULTS

There was an unadjusted association of WBC reduction with a decreased risk of postoperative infection [summary OR = 0.93; 95% confidence interval (95% CI), 0.88-0.99; P < 0.01] that did not persist following adjustment for confounding factors (summary OR = 0.94; 95% CI, 0.85-1.04; P > 0.05). There was neither an unadjusted nor an adjusted association of WBC reduction with decreased mortality (summary OR = 0.94; 95% CI, 0.71-1.23; P > 0.05; and OR = 0.92; 95% CI, 0.80-1.05; P > 0.05, respectively).

CONCLUSIONS

An association of WBC reduction with decreased mortality was not detected across the results available from all before-and-after studies. An unadjusted association of WBC reduction with a decreased risk of postoperative infection exists, but this was not detected across the three studies that reported multivariate analyses.

Comparison of the effects of a 50% exchange-transfusion with albumin, hetastarch, and modified hemoglobin solutions

We compared the hemodynamic effects of replacing 50% of the blood volume of anesthetized rats with an equal volume of five solutions: human serum albumin (HSA), hetastarch, unmodified hemoglobin, diaspirin-crosslinked hemoglobin, and o-raffinose-crosslinked hemgolobin. Control rats were exchange-transfused with their own blood. HSA and hetastarch caused a severe reduction in systemic vascular resistance (SVR), hypotension, and acute renal failure immediately after the exchange-transfusion. Unmodified and diaspirin-crosslinked hemoglobins caused comparable and severe increases in SVR, whereas vasoconstriction induced by o-raffinose-crosslinked hemoglobin was minimal. The increased SVR induced by all hemoglobin solutions resolved over a 2-day period as the hemoglobin was cleared from plasma. Body weight was monitored for 5 days after the exchange transfusion as a measure of the relative long-term efficacy of the exchange solutions tested and increased substantially in control rats (that received blood). Rats that received both crosslinked hemoglobin solutions gained a comparable amount of weight as the control group. By contrast rats that received HSA, hetastarch and unmodified hemoglobin failed to gain weight or lost weight over the same period. In summary: i) HSA and hetastarch are relatively ineffective as resuscitative fluids when administered after the loss of a large volume of blood; ii) diaspirin-crosslinked hemoglobin causes severe vasoconstriction, comparable in intensity to that induced by unmodified hemoglobin; iii) o-raffinose-crosslinked hemoglobin induces minimal vasoconstriction; iv) the vasoactive effects of all hemoglobin solutions are reversible. We conclude, that of all solutions tested, both the short- and long-term effects of an exchange-transfusion with whole blood are most closely reproduced by an exchange with o-raffinose-crosslinked hemoglobin.

Universal leukocyte reduction

Leukocyte reduction of blood components, in the United States, is generally reserved for conditions in which a clinical indication has been documented. There is no evidence that either Creutzfeldt-Jakob disease or variant Creutzfeldt-Jakob disease are transmitted by transfusion in humans or that leukocyte reduction of blood components could reduce their transmission. A number of adverse outcomes following transfusion are alleged to be the result of white blood cells. At this point in time, there are insufficient clinical data to justify the universal leukocyte reduction of blood components.