Sickle cell disease and haemoglobinopathies Flashcards Preview

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Flashcards in Sickle cell disease and haemoglobinopathies Deck (65)
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1

What is normal adult haemoglobin

HbA

2

describe what chains the haemoglobin is made out of

2 alpha
2 beta

3

How many molecules of haem are in an adult haemoglobin

4 haem molecules

4

define haemoglobinopathies

Abnormalities
affecting the globin chains

5

What are the two main groups of haemoglobinopathies

- Sickling syndromes
- Thalassaemias

6

What is sickle cell disease charactersied by

- the presence of HbS

7

What happens in sickle cell disease

- vaso-occlusion/infarction - abnormal shape red blood cell blocks the normal circulation and causes vascular occulsion
- haemolysis - abnormal red cells are easily destroyed by the epithelial system

8

Describe the precipitating factors of sickle cell disease

◦ Hypoxia
◦ HbS Concentration / dehydration
◦ Acidosis

9

What does the presence of haemoglobin S do

- causes polymerisation - causes the red cell to sickle - this is reversible

10

what are the characteristics of sickle cell disease

- Painful crises
- Systemic vasculopathy
- End organ damage
- Reduced life expectancy

11

What mutation causes HbS

- point mutation
- substitution of glutamate by valine in position 6 in the Beta globin chain

12

How is sickle cell anaemia passed on

- autosomal recessive - two people both have to have it to give someone a chance of getting it
- carriers are asymptomatic

13

How do you diagnose sickle cell disease

Clinical
- family history
- recurrent pain

Lab
- anaemia
- haemolysis - high bilirubin, high LDH, raised reticulocytes and undetectable haptoglobin
- blood film - sickle cells
- haemoglobin electrophoreiss/sickle solubility test

14

How does the sickle solubility test work

- Place the red cells in an acidic medium
- Negative - if you can see the lines behind the tube
- Positive if you cannot see lines behind the tube

15

What are the emergency presentations of sickle cell disease

- Pain/acute painful crisis
- acute deterioration of anaemia
- sequestration
- aplastic crisis
- overwhelming sepsis
- acute chest sydnrome
- stroke
- fat embolism sydnrome/multi organ failure
- renal impairment
- priapism
- acute visual loss

16

What is the most common cause for patients presenting to hospital with sickle cell anaemia

- acute painful crisis

17

what are the precipitating factors of an acute painful crisis

- infections
- skin cooling
- dehydration
- deoxygenation
- stress

- in up to 50% there is no obvious precipitator

18

How do people present with acute painful crisis in sickle cell anaemia in hospital

• Rapid onset of bone pain; bone marrow infarction
• Variable severity and duration; hours to weeks
• Fever, bone tenderness +/- swelling, hypertension, tachycardia,
tachypnoea

19

How do you manage acute acute painful crisis in sickle cell anaemia

- deliver an analgesia within 30 minutes from presentation
- parental opiate analgesia often required
- re-assess and repeat as necessary

anticipate and treat pre-emptively
- nausea/vomiting = anti emetics
- pruritus = anti histamines
- constipation = laxatives

20

When a patient presents with acute painful crisis in sickle cell anaemia what should you investigate

- temperature
- vital signs
- fluid intake
- analegesia
- sedation/urinary retention/restlessness
- FBC and reticulocytes
- U and E and liver function test
- LDH
- CRP
- blood cultures
- CXR
- always look for precipitating factors

21

What is acute chest syndrome in painful crisis in sickle cell anaemia

All ages; commonest cause of death in adults (25% of all deaths)
- 2nd most common cause of hospitalisation

22

How do you define acute chest syndrome

- Acute illness associated with respiratory symptoms and a new infiltrate on a CXR

23

What are the precipitating factors on acute chest syndrome (sickle cell disease)

- Surgery/anaesthesia
- pregnancy

24

What can acute chest syndrome increase

- increased risk of chronic lung disease
- increased risk of death

25

describe the pathophysiology of acute chest syndrome (sickle cell disease)

increase in
- infection
- asthma
- hypoventialtion

This causes hypoxia, inflammation and acidosis
which casues vasooclusion within the pulmonary microvasculature which causes hypoxia, inflammation and acidosis and so on

- fat embolism and pulmonary thrombi can also cause vasoocclusiion within the pulmonary microvasculature

26

What is the acute management for acute chest syndrome (sickle cell disease)

- adequate analgesia
- incentive spirometry
- reduces ACS in patients admitted with VOC (5% v 42%)
- oxygen therapy
- value of NIV even in the absence of severe hypoxia

Fluid management
Antibiotics

Transfusion
- value of TUT in mild ACS
- Exchange Transfusion (ExTx) gen recommended for moderate/severe ACS
- if ExTx cannot be readily offered give a transfer to a place where they can do it

27

What is an exchange transfusion

remove the patients own blood and replace it with normal

28

patients who are homozoygous HbSS tend to ...

- splenic auto-infarction from a very young age = leads to functional asplenia

29

by what age do people who have sickle cell anaemia homozygously are asplenia (sickle cell disease)

Majority <3 years

30

What does not having a spleen put you at risk of (sickle cell disease)

Pneumococcal, Meningococcal & Haemophilus influenzae