Page 39 - Essential Haematology

Chapter 2 Erythropoiesis and anaemia / 25

features can be considered under four major

Table 2.3 Normal adult red cell values.
headings.
Male Female 1 Speed of onset Rapidly progressive anaemia
Haemoglobin (g/dL) 13.5 – 17.5 11.5 – 15.5 causes more symptoms than anaemia of slow
onset because there is less time for adaptation in
Haematocrit (PCV) 40 – 52 36 – 48 the cardiovascular system and in the O 2 dissocia-
(%)
tion curve of haemoglobin.
Red cell count 4.5 – 6.5 3.9 – 5.6 2 Severity Mild anaemia often produces no symp-

12
( × 10 /L) toms or signs but these are usually present when
Mean cell 27 – 34 the haemoglobin is less than 9 – 10 g/dL. Even
haemoglobin severe anaemia (haemoglobin concentration as

(MCH) (pg) low as 6.0 g/dL) may produce remarkably few
symptoms, however, when there is very gradual
Mean cell volume 80 – 95
onset in a young subject who is otherwise healthy.
(MCV) (fL)

3 Age The elderly tolerate anaemia less well than
Mean cell 30 – 35 the young because of the effect of lack of oxygen

haemoglobin on organs when normal cardiovascular compen-
concentration
(g/dL) sation (increased cardiac output caused by
increased stroke volume and tachycardia) is
Reticulocyte count 50 – 150 impaired.
9
( × 10 /L)
4 Haemoglobin O 2 dissociation curve Anaemia,
in general, is associated with a rise in 2,3 - DPG
PCV, packed cell volume.
in the red cells and a shift in the O 2 dissociation
curve to the right so that oxygen is given up more

readily to tissues. This adaptation is particularly
cythaemia (see p. 208 ); conversely, an increase in
marked in some anaemias that either aff ect red
plasma volume (as with splenomegaly or pregnancy)
cell metaboism directly (e.g. pyruvate kinase defi -
may cause anaemia even with a normal total circu-
ciency which causes a rise in 2,3 - DPG concentra-
lating red cell and haemoglobin mass.
tion in the red cells) or that are associated with
After acute major blood loss, anaemia is not
a low affinity haemoglobin (e.g. Hb S) (Fig. 2.9 ).

immediately apparent because the total blood
volume is reduced. It takes up to a day for the
plasma volume to be replaced and so for the degree Symptoms
of anaemia to become apparent (see p. 412 ).

Regeneration of the haemoglobin mass takes sub- If the patient does have symptoms these are usually

stantially longer. The initial clinical features of shortness of breath, particularly on exercise, weak-
major blood loss are therefore a result of reduction ness, lethargy, palpitation and headaches. In older
in blood volume rather than of anaemia. subjects, symptoms of cardiac failure, angina pec-
toris or intermittent claudication or confusion may
be present. Visual disturbances because of retinal
Clinical f eatures of a naemia haemorrhages may complicate very severe anaemia,

The major adaptations to anaemia are in the cardio- particularly of rapid onset.
vascular system (with increased stroke volume and
tachycardia) and in the haemoglobin O 2 dissocia-
Signs
tion curve. In some patients with quite severe
anaemia there may be no symptoms or signs, These may be divided into general and specifi c.

whereas others with mild anaemia may be severely General signs include pallor of mucous membranes
incapacitated. The presence or absence of clinical which occurs if the haemoglobin level is less than