MKSAP: 52-Year-Old Woman With Osteoarthritis Of The Right Hip

A 52-year-old woman undergoes perioperative evaluation. She has osteoarthritis of the right hip since sustaining injuries in a motor vehicle accident 15 years ago and is scheduled for elective hip arthroplasty in the next few months. Medical history is otherwise notable for type 2 diabetes mellitus. She is up to date on routine health care. Her last menstrual period was 5 weeks ago. Medications are ibuprofen and metformin.

On physical examination, vital signs are normal. She has painful and limited range of motion in the right hip.

Laboratory studies:

Hemoglobin 10 g/dL (100 g/L)
Mean corpuscular volume 81 fL
Platelet count 223,000/µL (223 × 109/L)
Creatinine 1 mg/dL (88.4 µmol/L)
Hemoglobin A1c 7.5%

Which of the following is the most appropriate test to perform next?

A. Hemoglobin electrophoresis
B. Iron studies
C. Vitamin B12 level
D. No further evaluation

MKSAP Answer and Critique

The correct answer is B. Iron studies.

Iron studies should be performed next. Preoperative anemia is associated with increased perioperative mortality in patients with cardiovascular disease; it is also a significant predictor for perioperative blood transfusion, which itself is associated with postoperative morbidity. The common causes for preoperative anemia are iron deficiency, vitamin B12 deficiency, chronic inflammatory disease, and chronic kidney disease. The hemoglobin level should be measured in the setting of signs or symptoms of anemia or surgery with a large expected blood loss at least 4 weeks before the surgery date. If anemia is identified, laboratory testing should begin with an assessment of iron status. Transferrin saturation less than 15% (or serum ferritin level less than 15 ng/mL [15 µg/L]) is consistent with iron deficiency anemia and should be treated with oral iron. If the response to oral iron is suboptimal because of patient adherence and surgical scheduling, intravenous iron should be used. Iron deficiency in this patient could be attributable to menstrual blood loss, occult gastrointestinal blood loss from NSAID-induced gastritis, or colon cancer. Evaluation and correction of the cause of iron deficiency anemia should take place before elective surgery.

Hemoglobin electrophoresis is useful to detect genetic hemoglobinopathies such as sickle cell disease or thalassemia, which are associated with lifelong anemia unlikely to present for the first time at this patient’s age. These conditions could be suspected with examination of a peripheral blood smear.

Vitamin B12 deficiency is less common than iron deficiency in most patients scheduled to undergo orthopedic surgery, and it is typically associated with macrocytic anemia, which is not present in this patient.

Ignoring this patient’s anemia is not appropriate, considering the increased risk of perioperative allogeneic transfusion, which carries its own risks and is avoidable if the anemia is treated beforehand.

Key Point

• Patients scheduled for elective surgery who have anemia should be evaluated for iron deficiency; preoperative management of iron deficiency anemia includes oral iron replacement and evaluation to determine the source of blood loss.

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