The technical definition of anemia is “decreased red blood cell mass,” which is difficult to measure. As a practical matter, anemia is defined as a hemoglobin level below the normal reference range. The World Health Organization (WHO) defines anemia using hemoglobin levels as follows:
- Men <13.0 g/dL
- Women <12.0 g/dL
- Pregnant women <11.0 g/dL
Blood loss from any cause may result in anemia, which may be acute, chronic, or acute on chronic. The distinction between acute and chronic blood loss anemia is crucial, because acute blood loss anemia contributes substantially to severity of illness classification—impacting revenue, quality and performance metrics, and pay-for-performance measures—whereas chronic blood loss anemia contributes very little to severity.
Chronic blood loss anemia is most often the result of chronic gastrointestinal bleeding, and the cause should be specifically identified if possible. Acute blood loss anemia is associated with acute or subacute GI bleeding, trauma, or surgery. Anemia occurring in these situations may seem to be a self-evident, intrinsic consequence of acute blood loss, but it is a separate identifiable condition that contributes independently to patient risk and severity of illness. It needs to be identified and clearly documented as “acute blood loss anemia” to be properly coded and classified.
The definition of acute blood loss anemia depends on the patient acutely losing enough blood to become anemic (see WHO criteria above) or to become significantly more anemic if there is preexisting chronic anemia of any cause. The development of anemia and its severity are the pathophysiologic basis for the greater severity of illness associated with the diagnosis of acute blood loss anemia.
The amount of blood loss, whether it was expected, or the need for transfusion is not definitive; the only definitive criterion is whether or not the patient becomes anemic. Blood transfusion is not required to substantiate the diagnosis of acute blood loss anemia, but if a transfusion is necessary, acute blood loss anemia is almost certainly present and should be documented.
For example, suppose a 50-year-old former professional football player has knee replacement surgery. His preop hemoglobin level is 16.2 g/dL, dropping to 13.5 g/dL after surgery and stable at discharge. Even though his hemoglobin level decreased 2.7 g/dL, he didn't have acute blood loss anemia because he didn't become anemic.
Next consider the case of a 30-year-old mother of 3 who undergoes a transvaginal hysterectomy for a prolapsed uterus. Her hemoglobin level is 12.5 g/dL before surgery and 11.2 g/dL after surgery. Her hemoglobin level dropped only 1.3 g/dL, but she became anemic due to acute blood loss, which should be documented.
What about patients with preexisting chronic anemia? In this situation, the clinician must decide at what point a decrease in hemoglobin level is significant enough to warrant a diagnosis of acute blood loss anemia. While there are no definitive standards, the following criteria may be useful:
- transfusion given,
- development of symptoms related to anemia,
- high-risk clinical circumstances, and/or
- a decrease in hemoglobin level of 1.0 to 2.0 g/dL (keeping in mind that a small drop is more significant if the patient has a lower baseline).
Take, for example, a 72-year-old woman with diabetes, osteoporosis, chronic systolic heart failure, stage 4 chronic kidney disease, and anemia of chronic disease, with a baseline hemoglobin of 10.2 g/dL, who requires open reduction and internal fixation for left femoral neck fracture. Hemoglobin level is 9.0 g/dL on postop day 1 and 8.5 g/dL on day 2; it then remains stable for the next 2 days. She has no anemia symptoms and does not require a transfusion. In this case a diagnosis of acute blood loss anemia would be warranted, based on the drop in hemoglobin of 1.7 g/dL over 2 days postop, requiring monitoring to assess the need for transfusion if anemia progressed. In addition, a hemoglobin of 8.5 g/dL represents a significant risk to this patient, given her age, chronic heart failure, and chronic kidney disease.
Surgeons often mistakenly believe that the diagnosis of acute blood loss anemia is detrimental when their quality of care is measured. However, the code for acute blood loss anemia is not classified as a complication of care. The confusion arises from the diagnosis of “postop hemorrhage” or “hemorrhage due to surgery,” which is coded as a significant complication. In fact, omitting the diagnosis of acute blood loss anemia may actually harm quality scores because severity of illness will not be adequately recorded.
In summary, making a distinction between acute and chronic blood loss anemia is important. Acute blood loss anemia is defined as acute blood loss from any cause sufficient to result in anemia or significantly worsen preexisting chronic anemia. It is crucial to recognize and document acute blood loss anemia because the condition is a significant indicator of severity of illness impacting revenue, quality and performance metrics, and pay-for-performance measures. Acute blood loss anemia is not classified as a complication of care, but a diagnosis of “postop hemorrhage” or “hemorrhage due to surgery” is.