What are the indications for administering iron infusion to an inpatient?

Indications for Inpatient Iron Infusion

Intravenous iron infusion should be administered to hospitalized patients with iron deficiency anemia who have intolerance to oral iron, inadequate response to oral supplementation, conditions impairing iron absorption, or when rapid correction is required before surgery. 1, 2, 3

Primary Indications for IV Iron in Hospitalized Patients

Failure or Intolerance of Oral Iron

• Patients who cannot tolerate oral iron due to gastrointestinal side effects (nausea, constipation, diarrhea occurring in 8-12% of patients) should receive IV iron. 1, 2
• Patients who fail to achieve hemoglobin increase of 1 g/dL within 2 weeks of oral supplementation or lack ferritin improvement within one month despite adherence warrant IV iron therapy. 1, 2

Malabsorption States

• IV iron is indicated when oral absorption is impaired, including active inflammatory bowel disease, post-bariatric surgery (particularly procedures disrupting duodenal absorption), and celiac disease. 1, 2
• In inflammatory bowel disease, hepcidin upregulation from inflammation blocks gastrointestinal iron absorption and reduces bioavailability from iron stores, making oral therapy ineffective. 1

Anemia of Chronic Disease

• Patients with chronic inflammatory conditions where ferritin <100 µg/L with transferrin saturation <20% and C-reactive protein >5 mg/L should receive IV iron, as oral iron is ineffective due to hepcidin-mediated blockade. 1

Chronic Kidney Disease

• IV iron is indicated in non-dialysis dependent CKD patients with iron deficiency anemia who have intolerance or unsatisfactory response to oral iron. 3
• Consider IV iron when transferrin saturation ≤20% and ferritin ≤100 ng/mL in CKD patients. 2

Perioperative Management

• Preoperative IV iron should be administered to anemic surgical patients (particularly colorectal surgery) to achieve target hemoglobin of 130 g/L, as this reduces morbidity and need for blood transfusion. 1
• Timing depends on surgical urgency; 1-1.5 g typically restores iron stores and can be given in single or divided doses, with mean hemoglobin increase of 8 g/L over 8 days. 1

Severe or Symptomatic Anemia

• Patients with severe symptomatic anemia requiring rapid correction should receive IV iron rather than waiting for slower oral supplementation response. 1, 2

Ongoing Blood Loss Exceeding Absorption

• When gastrointestinal blood loss exceeds intestinal iron absorption capacity (e.g., angiodysplasia), IV iron is necessary as oral supplementation will be insufficient. 4

Heart Failure with Iron Deficiency

• IV iron is indicated in adult patients with heart failure (NYHA class II/III) and iron deficiency to improve exercise capacity, even without anemia. 3
• Dosing is based on weight and hemoglobin level, with maintenance doses at 12,24, and 36 weeks if ferritin <100 ng/mL or ferritin 100-300 ng/mL with transferrin saturation <20%. 3

Diagnostic Criteria for Iron Deficiency

• Absolute iron deficiency: serum ferritin <30 µg/L (most sensitive and specific test). 1
• Functional iron deficiency in inflammation: ferritin <100 µg/L with transferrin saturation <20% and CRP >5 mg/L. 1
• Hepcidin measurement is more reliable than transferrin saturation in critically ill patients with variable inflammation. 1

Safety Considerations

• Modern IV iron formulations (ferric carboxymaltose, iron sucrose, ferric gluconate) have low serious adverse reaction rates of approximately 38 per million administrations, with moderate-to-severe reactions affecting <1% of patients. 1, 5
• Resuscitation facilities must be available, and patients should be monitored for at least 30 minutes after infusion completion. 3
• Most reactions are complement activation-related pseudo-allergy rather than true IgE-mediated anaphylaxis; mild reactions can be managed by stopping and restarting at slower rate. 1
• High molecular weight iron dextran carries higher risk than non-dextran formulations. 1

Important Caveats

• Do not administer IV iron when ferritin is normal or elevated (>300 µg/L without inflammation), as this is potentially harmful and not indicated. 1
• Check serum phosphate levels in patients requiring repeat courses within 3 months, as ferric carboxymaltose can cause hypophosphatemia in 50-74% of patients. 3, 5
• Avoid measuring ferritin for 8-10 weeks after IV iron infusion, as levels will be falsely elevated. 1
• IV iron should not be combined with erythropoietin in most settings. 1