Parenteral Iron Replacement after Bariatric Surgery.
Authors: Varma Seema , Baz Walid , Badine Edgar , Terjanian Terenig , Forte Frank , Dai Qun 
Published: October 2019

Abstract
Background: Malabsorptive bariatric procedures such as Roux-en-Y gastric bypass (REY) and biliopancreatic diversion/duodenal switch (BPD/DS) expose the patient to significant metabolic effects, most commonly iron deficiency. Optimal replacement and monitoring strategies remain undetermined. Further, there are no data regarding parenteral iron replacement after bariatric surgery. We evaluated bariatric surgery patients who received parenteral iron replacement therapy at our hematology center.
Methods: We performed a retrospective cohort analysis and reviewed the medical records of 165 patients who received parenteral iron from 5/04 to 6/07. 42 bariatric surgery patients were identified. The type of bariatric procedure and menstrual status of patients were compared. ANOVA, Chi-square and t-tests were used for statistical analysis.
Results: The average age for the groups was similar; 40 years. There were only 2 men (4.76%) and 40 women, 32 (76%) of whom were of menstrual age and 8 (24%) were post-menopausal. 8 women were found to have other factors contributing to the anemia (7 with menorrhagia and 1 with celiac disease).
Roux-en-Y gastric bypass (REY) versus biliopancreatic diversion/duodenal switch (BPD/DS) and menstruating women versus men and postmenopausal women All Patients n=42 Roux-en-Y n=23 Bilio-pancreatic diversion/Duodenal switch n=17 p value Menstrual women n=24 Men and post-menopausal women n=10 p value *p value significant. Mean hemoglobin gm/dl 8.1(95% CI 7.738–8.638) 8.5 7.5 0.02 * 7.8 8.4 0.26 Mean ferritin level ng/ml 5.4(95% CI 3.3–7.5) 6.2 3.9 0.33 4.13 7.77 0.2106 Median time to parenteral iron therapy 42.5months 48 months 43 months 0.32 37.5 months 54 months 0.008* Need for additional parenteral iron treatments 24/42(57%) 11/23(47%) 13/17 (76.4%) 0.001* 15/24(62.5%) 7/10(70%) 0.062 Number of anemia-related hospitalizations 14/42 (33.3%) 4/23 (17.39%) 10/17(58.8%) 0.01* 12/24(50%) 2/10(20%) 0.00033*
Patients in the BPD/DS group had significantly lower hemoglobins (p=0.02) at the time of presentation, lower ferritin levels, and required subsequent parenteral iron treatments after initial resolution of anemia (p=0.001). The above parameters were not influenced by menstrual status. The number of anemia related hospitalizations was significantly higher in menstrual women (p=0.00033) and also in the BPD/DS group. Also, menstrual women required parenteral iron replacement earlier than men or postmenopausal women (p=0.008).
Conclusion: A considerable number of patients develop severe, symptomatic iron deficiency anemia within 1–4 years after bariatric surgery and need parenteral iron replacement after oral iron therapy has failed. Malabsorption plays a significant role in the development of iron deficiency, and the greater the degree of malabsorption resulting from the bariatric procedure the more the likelihood of recurrence of iron deficiency. Menstrual women are at a higher risk due to continual iron losses and tend to require intravenous replacement earlier. Bariatric surgery patients who do not respond to oral iron therapy should be referred early for parenteral iron replacement, especially after malabsorptive procedures, particularly in women of child-bearing age. In order to maintain quality of life and prevent anemia related complications, close monitoring and early iron replacement are crucial, and the follow-up should be indefinite even after repletion of iron stores and resolution of anemia.