Iron Deficiency and Gastric Bypass Surgery
A 30-year-old woman with a history of gastric bypass 2.5 years ago is now pregnant and has severe iron-deficiency anemia. She received IV iron after failing oral iron. Post delivery, her anemia resolved. What is the algorithm for follow-up and how often do I transfuse her with IV iron?
Sapna Patel, MD
Iron-deficiency anemia is a common complication of gastric bypass and is more pronounced in menstruating females. There is also a risk of other micronutrient deficiencies, such as vitamin B12 and calcium deficiencies. These require correction in their own right.
It is important to know what type of bypass surgery was performed, because patients with a Roux-en-Y gastric bypass are at greater risk for low levels of ferritin vs those with a biliopancreatic diversion. Severe iron deficiency during pregnancy is described and often requires parenteral iron for correction. There is some evidence that the addition of vitamin C to an oral iron-replacement regimen enhances iron absorption, although this is by no means a long-term solution.
The cardiovascular effects of long-standing anemia have been well illustrated in patients with chronic kidney disease, and it is essential to correct any anemia to normal levels in patients after gastric bypass. However, simply correcting the hemoglobin is not sufficient and an adequate iron status is imperative. There are no strict guidelines, although serum ferritin (measure of iron stores) should be kept between 400 and 1000 mcg/L. Iron sucrose, a ferric-hydroxide sucrose complex, is readily available and has a low side-effect profile especially when administered correctly. The World Health Organization recommends the following formula for determining the dose required:
Requirement in mg of iron = 0.66 x body weight (kg) x [100- (Hb in g/dL x 100/14.8)]
Serum ferritin and transferrin saturation (above 20% at least) should only be checked 1 month after each iron dose and, once stable, every 3 months. Finally, it is important to minimize menstrual losses in female patients and correct B12 and folate deficiencies, too.