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 :
- 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 .
- 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 .
- 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 .
- 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 :
- Pallor . Pallor is the most common and characteristic sign which may be seen in the mucous membranes , conjunctivae and skin .
- 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 .
- 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 .
- Ocular manifestations . Retinal haemorrhages may occur if there is associated vascular disease or bleeding diathesis .
- 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 .
- Renal system . Mild proteinuria and impaired concentrating capacity of the kidney may occur in severe anaemia .
- 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 :
- Anaemia due to blood loss . This is further of 2 types :
- Acute post – haemorrhagic anaemia
- 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 :
- Cytoplasmic maturation defects
- Deficient haem synthesis : iron deficiency anaemia
- Deficient globin synthesis : thalassaemic syndromes .
- Nuclear maturation defects
Vitamin B12, and / or folic acid deficiency : megaloblastic anaemia
- Haematopoietic stem cell proliferation and differentiation abnormality e.g.
- Aplastic anaemia
- Pure red cell aplasia
- Bone marrow failure due to systemic diseases ( anaemia of chronic disorders ) e.g.
- Anaemia of inflammation / infections , dissemi nated malignancy
- Anaemia in renal disease
- Anaemia due to endocrine and nutritional deficiencies ( hypometabolic states ) 4. Anaemia in liver disease
- Bone marrow infiltration e.g.
- Leukaemias
- Lymphomas
- Myelosclerosis
- Multiple myeloma
- Congenital anaemia e.g.
- Sideroblastic anaemia
- 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 :
- Intracorpuscular defect ( hereditary and acquired ) .
- 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 :
- 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 ) .
- Normocytic , normochromic : MCV , MCH , MCHC are all normal e.g. after acute blood loss , haemolytic anaemias , bone marrow failure , anaemia of chronic disorders .
- Macrocytic : MCV is raised e.g. in megaloblastic anaemia due to deficiency of vitamin B12 or folic acid .