Length of Red Cell Unit Storage and Risk for Delirium After Cardiac Surgery
BACKGROUND:
The time that red cell units are
stored before transfusion may be associated with postoperative
complications, although the evidence is conflicting. However, the
association between the length of red cell unit storage and
postoperative delirium has not been explored. We hypothesized that the
length of storage of transfused red cell units would be associated with
delirium after cardiac surgery.
METHODS:
We conducted a case-control study in which patients undergoing coronary artery bypass, valve, or ascending aorta surgery
with cardiopulmonary bypass at Johns Hopkins from 2005 to 2011 were
eligible for inclusion. Patients were excluded if they did not receive
red cell units, received >4 red cell units during hospitalization,
received any transfusion after the first postoperative day, or received
red cell units that were not exclusively stored for ≤14 days or >14
days. Eighty-seven patients met transfusion-related inclusion criteria
and developed postoperative delirium. Controls who did not develop
delirium were selected from the same source population of eligible
patients and were matched 1:1 based on age (± 5 years), 2- to 2.5-year
band of date of surgery, and surgical
procedure. For each patient, we calculated the average storage duration
of all transfused red cell units. The primary outcome was odds of
delirium in patients who were transfused red cell units with exclusive
storage duration >14 days compared with that of ≤14 days. Secondary
outcomes were odds of delirium with each increasing day of average red
cell unit storage duration. We used conditional multivariable regression
to test our hypotheses.
RESULTS:
In conditional
multivariable analysis of 87 case-control pairs, there was no difference
in the odds of patients developing delirium if they were transfused red
cell units with an exclusive storage age >14 days compared with that
≤14 days (odds ratio [OR] 1.83; 95% confidence interval, 0.73-4.58,
P=0.20). Each additional day of average red cell unit storage beyond 14
days was associated with a 1.01- to 1.13-fold increase in the odds of
postoperative delirium (OR, 1.07; P=0.03). Each additional day of
average storage beyond 21 days was associated with a 1.02- to 1.23-fold
increase in the odds of postoperative delirium (OR, 1.12; P=0.02).
CONCLUSIONS:
Transfusion
of red cell units that have been stored for >14 days is not
associated with increased odds of delirium. However, each additional day
of storage >14 or 21 days may be associated with increased odds of
postoperative delirium in patients undergoing cardiac surgery.
More research is needed to further characterize the association between
delirium and storage duration of transfused red cell units.
