Childhood Anemia: An Overview Gao Ju MD, PhD Professor of Pediatrics Department of Pediatric Hematology/Oncology West China Second University Hospital, SU

Major Items Essentials of Hematology: An Brief Review Hematopoiesis  Hematological Features in Normal Children Childhood Anemia: An Overview Useful References and Websites

Fundamentals of Hematology

Cardiovascular system Blood is the fluid circulating constantly in the closed cardiovascular system (CVS). It consists of plasma  blood cells. Blood cells in turn include red cells, white blood cells  platelets. Cardiovascular system platelet red cell

Differs in cell morphology  functions WBC includes neutrophils, lymphocytes, monocyte, eosinophils  basophil. Differs in cell morphology  functions neutrophils monocytes eosinophils lymphocytes basophils

Blood: plasma  “formed elements”-blood cells

Hematopoiesis: the process of producing mature blood cells, among which circulating red cells are essential to oxygen carrying to tissues. Under normal physiologic conditions, the Production of blood cells (hematopoiesis) is kept in dynamic balance with the Destruction of blood cells (D=P).

Blood plays many important physiological functions Blood plays many important physiological functions. Among them, oxygen transport is the most important, which is essential to our survival. This is specifically carried out by Hb, the most abundant protein in red blood cells. 300 million Hb molecules in a single mature circulating red cell, comprising 97% of red cell dry weight

Humans are strict aerobic animals Humans are strict aerobic animals. We need oxygen for energy production and many other metabolic processes. Two molecules of ATP is produced from 1 molecule of glucose via anaerobic glycolysis, but 34 molecules of ATP could be produced from 1 molecule of glucose via tricarboxylic acid cycle (Krebs cycle ) . Mature red cells, anucleated and without mitochondria, are incapable of oxidative metabolism and destined to death up to their normal life span (100-120 days)

Blood O2 content = [1.34  Hb (SaO2/100)] + 0.003PO2 = 20.8ml Henry’s law : the amount of oxygen dissolved is proportional to the partial pressure. For each mmHg of PO2 there is 0.003 ml O2/dL (100ml of blood) Blood O2 content = [1.34  Hb (SaO2/100)] + 0.003PO2 = 20.8ml For the sake of efficient oxygen transportation, there must be a vehicle to carry oxygen from the lungs to peripheral tissues, instead of direct dissolution of O2 in water (plasma). Low oxygen solubility: oxygen dissolved in plasma could be as low as 0.13 mmol/L under maximal arterial oxygen partial tension. It could be as high as 8.6 mmol/L while bound to Hb under the same arterial oxygen partial tension—66-fold increase. Poor oxygen diffusibility In fact, 100 ml blood (Hct45%, equivalent of Hb15 g/L) can carry 20 ml of oxygen, while 100ml plasma can only carry 0.3 ml of oxygen.(60-fold difference)

Hb is JUST the right vehicle Molecular structure (Hb is a allosteric enzyme) The peculiar sigmoidal oxygen dissociation curve facilitates oxygen binding in lungs with higher oxygen tension, and promotes oxygen dissociation in peripheral tissues with lower oxygen tension.

Hematopoiesis  Hematological Features in Normal Children

Bone marrow, the organ of blood cell production Low-power field High-power field

Hematopoiesis in normal children Two distinct stages：fetal  postnatal hematopoiesis Fetal Hematopoiesis Mesenchymal Hematopoiesis Liver/Spleen Hematopoiesis Medullary Hematopoiesis

Postnatal Hematopoiesis Medullary Hematopoiesis Hematopoiesis in all bones before 5 years of age (red marrow). Yellow marrow increases gradually after 5-7 years. Hematopoiesis primarily concentrates in flat bones and proximal ends of long bones. Extra-Medullary Hematopoiesis Happens in case of increased demand for hematopoiesis (e.g., hemolysis, bleeding). Characterized by hepatosplenomegaly and presence of nucleated red cells in peripheral circulation.

Hb Switching during embryonic, fetal  postnatal life Actually, there are only 6 Hb during ontogeny, just because that some globin chains are present at different time period during development.

Hematological features in normal children RBCs and Hb RBCs at birth: (500-700)1012/L Hb at birth: 150-220g/L 2-3 months after birth(nadir: physiologic anemia) RBCs 300 1012/L Hb 110g/L Reticulocytes Within 3 days after birth: (0.04-0.06) 1012/L 1 week after birth: (0.005-0.15) 1012/L 1 month after birth: (0.02-0.08) 1012/L 5 month after birth: same as that in adults

Types of Hb WBC count HbF at birth: 75%。 HbF at 4 month:20%。 HbF at 1 year of age:5%。 HbF at 2 years of age: 2%。 WBC count At birth: WBC 15000-20000/l. During infancy: 10000/l. After 8 years of age: same as that in adult. HbA(22): 95%~97% HbA2(22): 2%~3% HbF(22): 1%

WBC differential count- two cross-overs At birth, neutrophil predominates. The first cross-over occurs at 4-6 days after birth. Then， lymphocytes predominates during infancy (65%) and neutrophils account for 35%. The second cross-over happens during 4-6 years of age. After that, neutrophils predominate again. Platelete (10-30) 109/L, same as that in adult

WBC differentials during childhood 4-6days 4-6 yrs Lymphocyte 0.3 0.4 0.5 0.6 0.7 neutrophils WBC differentials during childhood

Childhood anemia with different underlying diseases Anemia: An Overview Childhood anemia with different underlying diseases -Illustrative photos

Definition of Anemia Literally, anemia means “without blood” . Physiologically, anemia refers to any state of reduced red cell mass (RCM). Clinically, anemia is defined as a reduction of RBC count, Hb concentration or hematocrit in unit volume of peripheral blood compared to a normal group (Keep in mind these are all measures of concentration). According to WHO criteria, anemia is defined as Hb conc. lower than 95 percentile of norm.

Anemia is best defined by the decrease in the body's total red cell mass (RCM)

Functionally, anemia is best characterized by Hb concentration below normal, given the fact that Hb is the primary vehicle for oxygen transportation. Practically, anemia is said to be present when Hb is lower than 110g/L for children aged 6 months to 6 years; or lower than 120 g/L for children aged 6-14 years at sea level , according WHO diagnostic criteria(1972)(lower than 95 percentile of normal values)

Normal Hb concentration at different ages

Red Blood Cells: Adult Reference Ranges Measurement (units) Men Women Hemoglobin (gm/dL) 13.6-17.2 12.0-15.0 Hematocrit (%), HCT 39-49 33-43 Red cell count (106/μL) 4.3-5.9 3.5-5.0 Reticulocyte count (%) 0.5-1.5 Mean cell volume (μm3), MCV 82-96 Mean corpuscular hemoglobin (pg), MCH 27-33 Mean corpuscular hemoglobin concentration (gm/dL) - MCHC 33-37 RBC distribution width, RDW 11.5-14.5

Summary Anemia per se is NOT an independent disease entity，but rather a clinical syndrome , or constellation of clinical manifestations. In order to diagnose anemia, there must be normal Hb reference values (gender-specific, age-specific, race-specific and region-specific), although they are arbitrary cutoff points with a 95% confidence interval. Hb, expressed as g/L (concentration) is just a relative number. Its value is affected by many factors, such as measuring method, altitude, hemoconcentration and hemodilution.

Diagnostic criteria of anemia WHO (1972)(at sea level) 6 month to 6 years of age: <110g/L 6-14 years of age: <120g/L Neonates less than 7 days: <145g/L There is a overlapping between Hb distribution curves in normal and anemic populations. 

Severity degrees of anemia Mild: Hb 90-120g/L，RBC 3-41012/L Moderate: Hb 60-90g/L，RBC 2-31012/L Severe: Hb 30-60g/L，RBC 1-21012/L Very severe: Hb <30g/L，RBC < 11012/L

Classification of anemia Morphological classification Emphasizes the importance of direct microscopic observation of red cells morphology. May suggest a clue of anemia etiology. Subdivides anemia into normocytic-normochromic, microcytic-hypochromic  macrocytic anemias, based on RBC indeces.

(Normocytic Normochromic Anemia) （MCV=80-96；MCHC=33-35） Acute bleeding Hemolytic anemia Extrinsic defects：immune and non-immune mediated. Intrinsic defects：membrane, enzyme, globin. Bone marrow failure syndromes Aplastic anemia, pure red cell aplasia

(Normocytic Normochromic Anemia) （MCV<80fl；MCHC=330g/L) Iron deficiency anemia, IDA Thalassemia Anemia of chronic disease，ACD Sideroblastic anemia

Microcytic Hypochromic Anemia （MCV<80fl；MCHC <330g/L）

Macrocytic Normochromic Anemia （MCV>96；MCHC=33-35） Megaloblastic Anemia Folate deficiency Cobalamin deficiency Combination of the above two Non-Megaloblastic Macrocytic Anemia

Macroovalocyte in peripheral circulation Megaloblastic nucleated red cells (megaloblast) sometimes could be seen

Neutrophil hypersegmentation of neutrophil nucleus：important clue to diagnosis and sometimes macrothrombocytes could be identified

Pathophysiological Classification Fosters an understanding of the disease process in kinetic terms. Reticulocyte count: most suitable starting point in kinetic approach Reticulocytosis (Ret%2%-3%, or absolute Ret100,000/mm3 Ret counts are most helpful if extremely low (<0.1%) or  3% (100,000/mm3 total). But anemia could be due to more than one mechanisms.

Pathophysiologically, there are TWO and JUST two mechanisms responsible for anemia development Decreased RBC Production Increased RBC Loss or Destruction

Water level in a reservior: an analogy Inflow=Outflow  Outflow  Inflow 120g/L 60g/L 60g/L Water level in a reservior: an analogy

Reduced RBC Production: Decreased Inflow Bone marrow failure : aplastic anemia Inadequate supply of hematopoietic materials Impaired hemoglobin synthesis: IDA Impaired DNA synthesis: folate/Cobalamin deficiency Increased RBC loss or destruction: increased outlow Loss( hemorrhage): acute v chronic; internal v external Destruction (hemolysis): acute v chronic; intravscular v extravascular

Compensation to Anemia: An Analogy Clinical manifestations Compensation to Anemia: An Analogy 400km CD CQ Task 60 p；loads 60p CQ 400km CD Task 60 p；loads 30p CQ 400km CD Task 60 p；loads 4p

Anemia can adversely affect multiple organ systems, with symptoms and signs occuring when oxygen carrying capacity of the blood is unable to meet the oxygen requirements of body tissues

The clinical presentations are determined by The underlying disease leading to anemia Hemolysis: jaundice and hemoglobulinuria Iron deficiency: pica and CNS symptoms VitB12 deficiency: motor and mental delay or regression The degree and rapidity of anemia Mild versus Severe Acute versus Chronic The adequacy of the body’s compensatory responses Tachypnea, tachycardia, increases capillary pulsation Right shift of the Oxygen-Dissociation curve

Compensatory mechanisms to anemia Redistribution of blood flow Skin vasoconstriction: pallor Renal vasoconstriction Diversion of blood to vital organs (heart, brain) Hemodilution due to increased plasma volume in case of chronic anemia, with reduced viscosity and facilitated blood flow Increased RBC DPG production and right shift of the oxygen-dissociation curve, and ease of Hb oxygen release in peripheral tissues

Opening of pulmonary and peripheral capillaries Increased cardiac contractility and heart rate, with resultant cardiac output Compensatory erythroid hyperplasia

Anemia: Stepwise Diagnostic Approaches Is there anemia INDEED? Pallor and other symptoms Hb reduction How about the degree? Hb measurement What is the underlying cause(s)? Clinical presentations Specific lab investigations

Diagnostic flowchart of anemia: an illustration Anemia Diagnosis Diagnostic flowchart of anemia: an illustration In the majority of clinical circumstances, the definite diagnosis of anemia relies heavily on clinical reasoning  relevant lab investigations

Anemia: Therapeutic Principles Etiological Therapy Management of the underlying disease Iron, folate or cobalamin supplementation Symptomatic and supportive therapy Component transfusion Stem cell transplantation

Anemia: Summary Anemia: Hb reduction in unit volume of peripheral blood compared to normal. NOT independent disease entity. Classifications:Morphological and pathophysiological. Mechanisms: Decreased RBC Production or Increased RBC Loss or Destruction. Diagnostic approach: Three-Steps.

Key Websites & References Irvin JJ and Kirchner JT. Anemia in children. Am Fam Physician. 2001;64(8):1379－1386. Understanding anemia, by Ed Uthman, MD, http://web2.airmail.net/uthman/unanemia/unanemia_ch1.html Blood cells and the CBC. http://web2.airmail.net/uthman/blood_cells.html Anemia: pathological consequences, classification and clinical investigation. http://web2.airmail.net/uthman/anemia/anemia.html http://www.hematologyatlas.com/principalpage.htm http://www.mcl.tulane.edu/classware/pathology/Krause/Krause.html http://www.bloodline.net/link_web_resources

http://web2.airmail.net/uthman/unanemia/unanemia_ch1.html

Atlas of hematology http://www.hematologyatlas.com/

BLOODLINE.net http://www.bloodline.net/

Our Team-Pediatric Hematology/Oncology

Reach me if you have any questions 高举 Gao Ju, MD, PhD. Director. Pediatric Hematology/Oncology, West China Second University Hospital, Sichuan University Tel:028-85501723(O) E-mail: gaoju651220@126.com