11.8 Preop Anaemia Flashcards
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)
> > 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.
b) What physiological adaptations occur to offset the effects of anaemia? (6 marks)
> > 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.
c) Describe perioperative events that may worsen the effects of the anaemia. (4 marks)
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.
d) What further blood tests may help in the classification of this anaemia? (5 marks)
> > 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
