Anemia: Why You Should Pay Attention

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Anemia: Why You Should Pay Attention


Anemia is extremely prevalent in all aspects of the world.  In Canada, the incidence is estimated at 20 per cent.  In those with chronic disease, the incidence approaches 60 per cent.  One study found that 87 percent of hospitalized patients became anemic during their hospital stay.

Anemia is an independent risk factor for hospital length of stay, morbidity, mortality, transfusion, acute kidney injury, and infection.  Anemia increases length of recovery following myocardial infarction, stroke, and intracranial hemorrhage.  Anemia portends a risk comparable to chronic kidney disease, and yet it is a modifiable risk factor even without transfusion.

The World Health Organization defines anemia as hemoglobin less than 130g/L in men and 120g/L in women.  The risks of anemia start to increase with any drop below these levels.  Unfortunately, we have become accustomed to seeing low hemoglobin and generally don’t start thinking about early intervention until the hemoglobin is less than 90g/L. 

Many recent publications have demonstrated improved patient outcomes, decreased hospital length of stay, decreased mortality, and decreased morbidity if anemia is actively managed early in a patient’s care.

However, transfusion is not the answer.  Every medical organization has advocated for a restrictive transfusion threshold for the past 30 years.  The current best practice is that transfusion is not indicated for hemoglobin greater than 70g/L except for specific circumstances including hypovolemia unresponsive to fluid resuscitation and evidence of active ischemia.  Even a single unit transfusion is associated with worse outcomes in all types of surgery!  One in every thirteen patients who receive a blood transfusion will be alloimmunized to some type of antibody, limiting future transfusions at best, and at worst resulting in death.  Transfusion also increases the risk of cancer recurrence in cancer surgery, and increases the future risk of developing Non-Hodgkin’s lymphoma later in life.  Infectious risk is largely thought of as transmission of viral or bacterial components, however patients receiving blood transfusions are also at risk of wound infection and implanted device complications.

So if anemia is a problem and transfusion isn’t the answer, what can be done?  The current best evidence suggests actively managing nutritional deficiencies, particularly in those with a compromised ability to absorb either iron or B12 enterally.  In fact, in centers where patients are routinely screened for iron and B12 deficiency, their transfusion rate is as low as one percent.

Hemoglobin is a late (lagging) measure of patient reserve.  By the time the hemoglobin is 70g/L or lower, the patient is often headed towards receiving a transfusion.  Alternatively, if iron stores are identified as being low early in a patient’s care and then corrected, transfusion can be avoided.  Iron stores are a leading measure of patient reserve. 

An iron deficient patient receiving intravenous iron will begin to generate reticulocytes within hours.  In fact one study randomized patients to either receive a blood transfusion or intravenous iron.  The group receiving intravenous iron had higher hemoglobin between day 7 and day 21 than the group receiving transfusion.  This effect persisted for the remainder of the 12 week study period.  When you are losing blood, you are actively losing iron.  For every 1 ml of blood lost, 0.5mg of iron is also lost.  If you have completely replete bone marrow, a one liter blood loss will result in complete depletion of iron stores.

Oral iron is still effective if the need is not acute.  Patients who have low ferritin and a low burden of other disease or inflammation generally respond well to oral iron.  If a patient has iron deficiency anemia and is started on an oral iron supplement, you can expect a 1g/L/d increase in hemoglobin.  Current recommendations are that after one month the patients’ hemoglobin should be rechecked.  If the hemoglobin has increased by 20g/L in one month, they are deemed responsive to oral iron and the therapy should be continued.  If the hemoglobin has not increased by this amount, they have failed oral iron therapy and should proceed to intravenous iron therapy. 

Additional information is available from the website.  If you or your department would like to learn more about patient blood management and improving anemia management, please contact Dr. Ryan Lett in the department of Anesthesiology or by e-mail at  The best practices in anemia management require a multidisciplinary approach.  Find out what you can do to improve patient care.

Submitted by:  Dr. Ryan Lett