The
information in this column is intended for informational
purposes only, and does not constitute medical advice or
recommendations by the author. Please consult with your
physician before making any lifestyle or medication changes, or if you
have any other concerns regarding your health.
AGE
OF TRANSFUSED BLOOD
& COMPLICATIONS AFTER SURGERY
Everyday,
thousands of people undergoing surgery will require transfusions with
lifesaving blood stored in hospital blood banks.
Because of the very small risk of passing
infections along to patients with blood transfusions, and because some
studies
have suggested that blood transfusions might depress immune function,
doctors
try to reserve blood transfusions only for those patients at greatest
risk of
complications, including death, from severe anemia.
However, it has long been known that blood,
which can be thought of as a living liquid human tissue, deteriorates
while
being stored, even under refrigerated conditions.
Although fresh blood can be stored for up to
42 days under optimal conditions, the levels of natural substances in
red blood
cells necessary for proper function begin to decline within few hours
after
collection from a donor. At
the same
time, the living cells within the donated blood continue to churn out
metabolic
waste substances that can have an adverse effect on very sick patients
receiving large volume blood transfusions.
Because
individual hospitals can never precisely predict how many blood
transfusions
will be required from one day to the next, blood banks need to keep a
small
surplus of blood products on hands at all times.
Since these products are highly perishable,
and can only be stored for a limited time before being discarded, most
blood
banks release their older stocks of blood for transfusion first, much
as your
neighborhood grocery store places the oldest containers of milk at the
front of
the shelf. Older
blood, in addition to
containing higher levels of potentially toxic metabolites, simply does
not take
up and unload life-sustaining oxygen as efficiently and as quickly as
fresh
blood does. Additionally,
the red blood
cells contained in older bags of blood are more fragile, and are more
easily
ruptured (also referred to as hemolysis), further reducing the
available number
of blood cells available following transfusion (the breakdown products
of
ruptured red blood cells can also be toxic to the liver and kidneys in
patients
with abnormal liver and kidney function).
A new research study, just published in the New England Journal
of Medicine, has cast further,
important, light on
this topic.
In
this study,
nearly 3,000 patients undergoing open-heart surgery were evaluated
after being
transfused with almost 9,000 units of blood that had been stored for 14
days or
less. The
complications and death rates for
this group of patients were then compared to a similar group of almost
11,000
open-heart surgery patients who had received “older” blood, which had
been
collected and stored for more than 14 days.
On average, blood given to the first group of patients was
about 11 days
old, while the blood transfused into the second group of patients was,
on
average, about 20 days old (the latter is still well within current
blood
storage and transfusion guidelines).
When
comparing
the clinical outcomes for these two otherwise matched groups of
patients, the
researchers found that the incidence of serious complications and risk
of death
were significantly higher among the patients receiving the “older”
blood. Specifically,
more patients receiving “older”
blood remained on a mechanical ventilator for 3 or more days than did
the
patients receiving “newer” blood (9.7% vs. 5.6%, respectively), and
these
patients were also more likely to suffer severe infections than the
patients
who received “newer” blood (4.0% vs. 2.8%, respectively). Similarly, the risk of
kidney failure, which
is associated with a high risk of death in critically ill patients, was
also
significantly higher in patients receiving “older” blood (2.7% vs. 1.6%
in
patients receiving “newer” blood, respectively).
Finally, and most importantly, the likelihood
of death within 1 year of surgery was also significantly higher among
the
patients receiving “older” blood than was observed in the patients
transfused
with “newer” blood (11.0% vs. 7.4%, respectively).
This
study is a
real eye-opener, because it suggests that significant increases in the
risk of
serious complications and death may be associated with transfusions of
even
relatively fresh blood, at least in patients undergoing major cardiac
surgery. Whether or
not the same degree
of adverse effects occur in patients undergoing other types of major
surgery
was not addressed by this study, although the mechanisms of
transfusion-associated illnesses and death are generally thought to be
similar
irrespective of the type of surgery, and are likely more related to the
number
and severity of co-existing illness within individual patients.
The
findings of
this study should generate further review of the current collection and
storage
guidelines for blood products, although the typically tight supply of
lifesaving blood products at most hospitals means that a significant
change in
the allowable duration of blood product storage is not likely to change
much at
all. At the same
time, I expect that
hospital blood banks will probably begin taking a closer look at which
patients
receive transfusions with “older” blood versus “newer” blood. A prudent approach, based
upon the results of
this study, would be to develop an algorithm whereby the sickest
patients would
automatically receive blood that has been stored for less than 14 days,
while
less seriously ill patients requiring blood transfusions would receive
the
“older” blood products.
OBESITY,
BLOOD
PRESSURE & HEART SIZE IN CHILDREN
As most of us
know, the incidence of obesity among both adults and children in the
developed
world has been skyrocketing. Obesity
has
long been known to be associated with a variety of life-shortening
conditions,
including high blood pressure, coronary artery disease, congestive
heart
failure, diabetes, stroke, liver disease and arthritis, among other
ailments.
Chronic high blood
pressure (hypertension), by itself, can lead to irreversible damage to
the
heart, brain, kidneys, retinas and other vital organs.
In the case of the heart, a chronically
elevated blood pressure causes the heart to have to work harder,
resulting in
progressive thickening of the heart’s main pumping chamber, the left
ventricle. Over
time, the enlarged and increasingly
stiff left ventricle can begin to fail, resulting in the development of
congestive heart failure (CHF).
Historically, CHF has been viewed as a disease of the
elderly, often
occurring after decades of poorly controlled hypertension, or after
heart
attacks have further damaged the left ventricle.
However, the rising incidence of obesity
among children has raised concerns that we may be on the cusp of an
epidemic of
early-onset obesity-related hypertension and coronary artery disease
among
young adults. A
timely new research
study in the Journal of Pediatrics confirms that
such an epidemic may be
just around the corner.
In this small
study, 44 obese and 22
non-obese children (average age was 8 years) were evaluated for blood
pressure
and left ventricular size. Not
surprisingly,
average blood pressure readings were significantly higher in the obese
children. In fact,
48% of the obese
children had documented episodes of hypertension during their daily
activities. Similarly,
the obese kids were found to
already have enlarged left ventricles, as measured by echocardiography.
This study reveals
the unpleasant truth that
pre-pubertal obese children are at markedly increased risk of
developing hypertension
and left ventricular enlargement (hypertrophy), and should raise alarm
bells
for any parent with an overweight or obese child.
The presence of confirmed high blood pressure
and left ventricular hypertrophy in these kids, and at an average age
of only 8
years, almost certainly means that these children will face an
extraordinarily high
future risk of hypertension-related ailments, and early death, unless
they are
able to shed their excess weight.
Disclaimer:
As always, my advice to readers is to seek the advice of your physician
before making any significant changes in
medications, diet, or level of physical activity.
