Enhanced recovery programs have been implemented perioperatively to reduce stress and restore baseline function at most of the hospitals in US. As a result, complications and length of stay have significantly reduced. The new trend of ERAS is gearing toward more patient-centric approach to improve longer term outcomes rather than functional recovery.
One element of the ERAS is to minimize anemia in patients coming for surgery. Preoperative anemia increases the severity and rate of postoperative anemia, and infection rate and potentially the length of stay. It may increases the need for transfusions for some surgeries that have significant blood loss. Iron therapy either by IV or PO and erythropoietin (EPO) have been pioneered as an alternative to correct anemia in some ERAS programs at hospitals such as Kaiser Permanente.
Although iron deficiency is the most common cause of anemia which accounts approximately 50% of anemic cases, there are often other causes such as congenital anemia, chronic kidney disease induced anemia, and cancer patients. Hence, we need to address the underlying cause and subsequently choose the appropriate iron replacement product to address specific needs of the patient. The other mistake we often make is that patients may not be anemic but have iron deficiency demonstrated by the microcytic red cells (mean corpuscular volume<80uL) when they come in for surgery. Iron deficient but non-anemic patients may experience fatigue or reduced exercise tolerance as iron is needed for optimal mitochondrial function essential for respiration and energy production. If we categorize anemic patients purely based on the cut-off level of Hgb>12(women) or>13 (man), the iron deficiency patients may be overlooked by the standard and likely become anemia after surgery and erythropoiesis would be compromised.
Serum ferritin is widely accepted as the gold standard to assess iron stores and the lower cut-off value <30ng/ml is used for diagnosis of ID. However, in the state of inflammation after surgery, with C-reactive protein>5mg/L, ferritin level between 30-100ng/ml may indicate the likelihood of absolute ID whereas ferritin>100ng/ml suggests iron sequestrations. Hence, if prior to surgery, patient’s ferritin level is less than 100ng/mL, iron therapy whether oral or IV may be considered.
TSAT (transferrin saturation) is another test that can be used together with ferritin to determine iron stores as it provides information on the availability of iron for tissue to utilize. If TSAT is less than 20% combined with ferritin level between 30-100ng/ml, it suggests that there is absolute iron deficiency which is not adequate to support normal erythropoiesis.
There are several guidelines on anemia management published so far. For example, the Kidney Disease Improving Outcomes provides guideline on anemia management for CKD patients. The guideline defines anemia for these group of patients as ferritin <100ng/mL and TSAT<20%. Iron therapy (either IV or oral) is recommended if TSAT <25% and ferritin is <200 ng/mL in CKD patients not on HD and <300 ng/mL in patients on HD. If patient is on ESA treatment and responsive to EPA or decreasing EPA is desired, iron therapy is recommended if TSAT<30% and ferritin <800ng/mL to promote erythropoiesis. The other common patient population we encounter is cancer patients, some guidelines recommends IV iron therapy for cancer caused anemia with Ferritin<800ng/mL if TSAT<40%. Chronic heart failure patients can also benefit from iron therapy e.g. ferric carboxymaltose to alleviate symptoms and improve exercise capacity.
The last group of patient population we take care of often are obstetric patients. They are usually iron deficient during pregnancy and may potentially lose significant amount of blood in postpartum. They are healthy and have normal erythropoiesic function. Hence, they can greatly benefit from the iron therapy to reduce the iron-limited erythropoiesis and thereby improve the recovery of postpartum such as reducing fatigue. This group of population would benefit greatly from iron supplement (PO). IV iron can be used as an alternative for patients who have scheduled cesarean section to boost iron stores.
As aforementioned, hemoglobin level can’t be used solely to assess anemia. Other lab tests such as ferritin and TSAT are more useful in providing information on iron stores. More patient-centric iron therapy should be applied to improve functional recovery and long-term outcome.
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