Acute Anemia
Anemia is characterized by a deficiency in the number of circulating red blood cells (RBCs), the amount of hemoglobin, or the percentage of packed RBCs in the blood, known as hematocrit. The World Health Organization (WHO) defines anemia as a hemoglobin level below 13 g/dL in males and below 12 g/dL in nonpregnant females. Anemia is classified into 2 main types: : Acute anemia: A sudden and rapid decrease in RBCs defines acute anemia, typically caused by hemolysis or acute hemorrhage. Chronic anemia: This type of anemia is characterized by a gradual decline in RBCs over time. Chronic anemia has various underlying causes, including iron or other nutritional deficiencies, chronic diseases, drug-induced factors, and other comorbid health issues. Please see StatPearls' companion resource, "Chronic Anemia," for further information on this type of anemia. While chronic anemia may initially be asymptomatic in mild cases, patients with acute anemia frequently present with symptoms of hemorrhagic shock, including tachycardia, hypotension, pallor, and altered mental status. The severity of shock is classified into 4 stages based on blood loss percentage, with increasing signs of hemodynamic instability as blood loss progresses. The evaluation of acute anemia primarily involves assessing its severity and identifying the source of bleeding; management focuses on stabilizing airway, breathing, and circulation (ABCs), stopping ongoing bleeding, and restoring blood volume.
