11.8 Preop Anaemia Flashcards

1
Q

A patient scheduled for primary elective total knee replacement is found to be anaemic, with a
haemoglobin level of 90 g/litre.

a) What perioperative consequences may be associated with preoperative anaemia? (5 marks)

A

> > Cancellation and, therefore, **
delayed treatment.

> > Increased length of hospital stay,
increased length of ICU stay, increased
all-cause morbidity and mortality.

> > Increased risk of cardiac events,
including myocardial infarction.

> > Increased risk of respiratory, *
urinary and wound infections.

> > Increased risk of thromboembolic events.*

> > Delayed wound healing.

> > Increased need for autologous
blood transfusion and its risks.

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2
Q

b) What physiological adaptations occur to offset the effects of anaemia? (6 marks)

A

> > Increased oxygen extraction by
tissues thus reducing SvO2.

Brain and heart already have hig
h extraction ratios and so are unable to
compensate further.

> > Increased cardiac output:
as a response to reduced systemic vascular
resistance due to decreased blood viscosity,
and also sympathetic response to hypoxia.

> > Redistribution of cardiac output to
areas of high demand such as
brain and heart.

> > Rightward shift of oxygen dissociation curve
due to increased 2,3DPG,
thus reducing the affinity of
haemoglobin for oxygen,
favouring oxygen
offloading at tissues.

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3
Q

c) Describe perioperative events that may worsen the effects of the anaemia. (4 marks)

A

Increased oxygen requirement:
» Shivering.

> > Pain.

> > Stress response.

> > Fever.*

Reduced oxygen delivery:

> > Hypoxaemia due to inadequate
oxygen therapy, failure to adequately
manage the airway, basal atelectasis,
thromboembolic event,
hypoventilation due to drug effects.

> > Reduced cardiac output *
due to anaesthetic agents.

> > Blood loss due to surgery.

> > Reduced erythropoiesis**
due to inflammatory response.

> > Hypothermia causing leftward shift*
of oxygen dissociation curve.

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4
Q

d) What further blood tests may help in the classification of this anaemia? (5 marks)

A

> > Iron. Lack causes microcytic anaemia.

> > Folate. Lack causes macrocytic anaemia.

> > B12. Lack causes macrocytic anaemia

> > Reticulocyte count.
Low count may indicate problem with bone marrow,
whereas high number may indicate premature haemolysis of red blood cells.

> > Red cell distribution.
Represents a variety in red blood cell
sizes due to a
range of different causes of anaemia.

> > Iron concentration.

> > Total iron binding capacity.
An indirect measure of the amount of
transferrin present in the blood.
Will be raised in iron deficiency anaemia,
low in anaemia of chronic disease.

> > Transferrin saturation.
Will be low in iron deficiency anaemia
but high in
anaemia of chronic disease.

> > Serum ferritin. Deficiency indicates lack of iron.

> > Urea and electrolytes.
May indicate an underlying cause
such as renal
dysfunction.

> > Liver function tests.

> > Inflammatory markers.
May support a diagnosis of
anaemia of chronic disease.

> > Haptoglobin levels.
Reduced level suggests
intravascular haemolysis.

> > Lactate dehydrogenase.**
Released with cell breakdown;
therefore an
indicator of haemolysis.

> > Free plasma haemoglobin.
Indicative of intravascular haemolysis.

> > Tests for haemoglobinopathies

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