Anaemia

                                                                                                ANAEMIA

Anaemia is defined as a haemoglobin concentration in blood below the lower limit of the normal range for the age and sex of the individual . In adults , the lower extreme of the normal haemoglobin is taken as 13.0 g / dl for males and 11.5 g / di for females . Newborn infants have higher haemoglobin level and , therefore , 15 g / dl is taken as the lower limit at birth , whereas at 3 months the lower level is 9.5 g / dl . Although haemoglobin value is employed as the major parameter for determining whether or not anaemia is present , the red cell counts , haematocrit ( PCV ) and absolute values ( MCV , MCH and MCHC ) provide alternate means of assessing anaemia .

Pathophysiology of Anaemia

Subnormal level of haemoglobin causes lowered oxygen – carrying capacity of the blood . This , in turn , initiates compensatory physiologic adaptations such as :

increased release of oxygen from haemoglobin ;

increased blood flow to the tissues ;

maintenance of the blood volume ; and

redistribution of blood flow to maintain the cerebral blood supply .

Eventually , however , tissue hypoxia develops causing impaired functions of the affected tissues . The degree of functional impairment of individual tissues is variable depending upon their oxygen requirements . Tissues with high oxygen requirement such as the heart , CNS and the skeletal muscle during exercise , bear the brunt of clinical effects of anaemia .

Clinical Features of Anaemia

The haemoglobin level at which symptoms and signs of anaemia develop depends upon 4 main factors :

  1. The speed of onset of anaemia : Rapidly progressive anaemia causes more symptoms than anaemia of slow onset as there is less time for physiologic adaptation .
  2. The severity of anaemia : Mild anaemia produces no symptoms or signs but a rapidly developing severe anaemia ( haemoglobin below 6.0 g / dl ) may produce significant clinical features .
  3. The age of the patient : The young patients due to good cardiovascular compensation tolerate anaemia quite well as compared to the elderly . The elderly patients develop cardiac and cerebral symptoms more prominently due to associated cardiovascular disease .
  4. The haemoglobin dissociation curve : In anaemia , the affinity of hemoglobin for oxygen is depressed as 2,3 BPG in the red cases . As a result , oxyhaemo globin is dissociate ne readily to release free oxygen for cellular use causing a shift of the oxyhaemoglobin dissociation curve to the right .

SYMPTOMS .

In symptomatic cases of anaemia , the presenting features are : tiredness , easy fatiguability , generalised muscular weakness , lethargy and headache . In older paling the may be symptoms of cardiac failure , angina pectoris , intermittent claudication , confusion and visual disturbances .

SIGNS .

A few general signs common to all types of anaemias are as under :

  1. Pallor . Pallor is the most common and characteristic sign which may be seen in the mucous membranes , conjunctivae and skin .
  2. Cardiovascular system . A hyperdynamic circulation may be present with tachycardia , collapsing pulse , cardiomegaly , midsystolic flow murmur , dyspnoea on exertion , and in the case of elderly , congestive heart failure .
  3. Central nervous system . The older patients may develop symptoms referable to the CNS such as attacks of faintness , giddiness , headache , tinnitus , drowsiness , numbness and tingling sensations of the hands and feet .
  4. Ocular manifestations . Retinal haemorrhages may occur if there is associated vascular disease or bleeding diathesis .
  5. Reproductive system . Menstrual disturbances such as amenorrhoea and menorrhagia and loss of libido are some of the manifestations involving the reproductive system in anaemic subjects .
  6. Renal system . Mild proteinuria and impaired concentrating capacity of the kidney may occur in severe anaemia .
  7. Gastrointestinal system . Anorexia , flatulence , nausea , constipation and weight loss may occur . In addition to the general features , specific signs may be associated with particular types of anaemia which are described later together with discussion of specific types of anaemias .

 

Classification of Anaemias

Several types of classifications of anaemias have been proposed . Two of the widely accepted classifications are based on the pathophysiology and morphology

PATHOPHYSIOLOGIC CLASSIFICATION .

Depending upon the pathophysiologic mechanism , anaemias are classified into 3 groups :

  1. Anaemia due to blood loss . This is further of 2 types :
  2. Acute post – haemorrhagic anaemia
  3. Anaemia of chronic blood loss

II . Anaemia due to impaired red cell formation . A disturbance due to impaired red cell production from various causes may produce anaemia . These are as under :

  1. Cytoplasmic maturation defects
  2. Deficient haem synthesis : iron deficiency anaemia
  3. Deficient globin synthesis : thalassaemic syndromes .
  4. Nuclear maturation defects

Vitamin B12, and / or folic acid deficiency : megaloblastic anaemia

  1. Haematopoietic stem cell proliferation and differentiation abnormality e.g.
  2. Aplastic anaemia
  3. Pure red cell aplasia
  4. Bone marrow failure due to systemic diseases ( anaemia of chronic disorders ) e.g.
  5. Anaemia of inflammation / infections , dissemi nated malignancy
  6. Anaemia in renal disease
  7. Anaemia due to endocrine and nutritional deficiencies ( hypometabolic states ) 4. Anaemia in liver disease
  8. Bone marrow infiltration e.g.
  9. Leukaemias
  10. Lymphomas
  11. Myelosclerosis
  12. Multiple myeloma
  13. Congenital anaemia e.g.
  14. Sideroblastic anaemia
  15. Congenital dyserythropoietic anaemia

The term hypoproliferative anaemias is also used to denote impaired marrow proliferative activity and includes 2 main groups : hypoproliferation due to iron deficiency and that due to other hypoproliferative disorders ; the latter category includes anaemia of chronic inflammation / infection , renal disease , hypo metabolic states , and marrow damage .

III . Anaemia due to increased red cell destruction ( haemolytic anaemias ) . This is further divided into 2 groups :

  1. Intracorpuscular defect ( hereditary and acquired ) .
  2. Extracorpuscular defect ( acquired haemolytic anaemias ) .

MORPHOLOGIC CLASSIFICATION . Based on the red cell size , haemoglobin content and red cell indices , anaemias are classified into 3 types :

  1. Microcytic , hypochromic : MCV , MCH , MCHC are all reduced e.g. in iron deficiency anaemia and in certain non – iron deficient anaemias ( sideroblastic anaemia , thalassaemia , anaemia of chronic disorders ) .
  2. Normocytic , normochromic : MCV , MCH , MCHC are all normal e.g. after acute blood loss , haemolytic anaemias , bone marrow failure , anaemia of chronic disorders .
  3. Macrocytic : MCV is raised e.g. in megaloblastic anaemia due to deficiency of vitamin B12 or folic acid .