Blood Flashcards
(98 cards)
What is the definition of anaemia
A low level of haemoglobin in the blood
This is the result of an underlying disease and is not the disease itself
The prefix an- means without
The suffix -aemia refers to blood
What is haemoglobin
A protein found in red blood cells.
It picks up oxygen in the lungs and transports this to the cells of the rest of the body
How is anaemia diagnosed
Low haemoglobin on blood test (normal: F 120-165, M 130-180)
Then look at mean cell volume (MCV) to determine the size of the red blood cells (normal: F 80-100, M 80-100)
How is anaemia categorised
Based on the size of the red blood cell (MCV)
Microcytic: low MCV so small RBCs
Normocytic: normal MCV so normal sized RBCs
Macrocytic: large MCV so large RBCs
What are the causes of microcytic anaemia
TAILS
T- Thalassaemia A- Anaemia of chronic disease I- Iron deficiency anaemia L- Lead poisoning S- Sideroblastic anaemia
What are the causes of normocytic anaemia
3As and 2Hs
Acute blood loss Anaemia of chronic disease Aplastic anaemia Haemolytic anaemia Hypothyroidism
What are the causes of macrocytic anaemia
Macrocytic anaemia can be megaloblastic or normoblastic
Megaloblastic anaemia is the result of impaired DNA synthesis preventing the cell from dividing normally. Rather than dividing it keeps browning into a larger abnormal cell. This is caused by a vitamin deficiency
Megaloblastic:
- B12 deficiency
- Folate deficiency
Normoblastic:
- Alcohol
- Reticulocytosis (usually from haemolytic anaemia or blood loss)
- Hypothyroidism
- Liver disease
- Drugs such as azathioprine
What are the symptoms of anaemia
Tiredness SOB Headaches Dizziness Palpitations Worsening of other conditions such as angina, heart failure or peripheral vascular disease
What are the signs of anaemia
Generic:
- pale skin
- conjunctival pallor
- tachycardia
- raised respiratory rate
Signs of specific causes of anaemia:
- Koilonychia: spoon shaped nails, can indicate iron deficiency
- Angular chelitis: can indicate iron deficiency
- Atrophic glossitis: a smooth tongue due to atrophy of the papillae and can indicate iron deficiency
- Brittle hair and nails: can indicate iron deficiency
- Jaundice occurs in haemolytic anaemia
- Bone deformities occur in thalassaemia
- Oedema, hypertension and excoriations on the skin can indicate chronic kidney disease
How is anaemia investigated
Bloods:
- Haemoglobin
- MCV
- B12
- Folate
- Ferritin
- Blood film
Further investigations:
- Oesophago-gastroduodenoscopy (OGD) and colonoscopy to investigate for a GI cause of unexplained iron deficiency anaemia. (On urgent cancer referral for suspected GI cancer)
- Bone marrow biopsy may be required if the cause is unclear
What is the clinical relevance of iron absorption
Iron is mainly absorbed in the duodenum and jejunum. It requires the stomach acid to keep the iron in the soluble ferrous (fe2+) form. When the acid drops it changes to the insoluble ferric (fe3+) form. Therefore, medications that reduce stomach acid such as PPI can interfere with iron absorption. Conditions that result in inflammation of the duodenum or jejunum such as coeliac disease or Crohn’s disease can also cause inadequate iron absorption.
What are the causes of iron deficiency anaemia
Blood loss (most common cause in adults)
Dietary insufficiency (most common cause in growing children)
Poor iron absorption
Increased requirements during pregnancy
Be suspicious of a GI tract cancer, oesophagitis and gastritis are the most common causes of GI tract bleeding. Inflammatory bowel disease (Crohn’s and Ulcerative colitis) should also be considered.
How does iron travel in the body
Travels as ferric ions (Fe3+) bound to a carrier protein called transferrin.
What is TIBC
Total iron binding capacity basically means the total space on the transferrin molecules for the iron to bind. Therefore, total iron binding capacity is directly related to the amount of transferrin in he blood.
How is iron deficiency testing understood
If measure the iron in the blood, and then the total iron binding capacity (TIBC) of the blood, can calculate the proportion of the transferrin molecules that are bound to iron. This is called the transferrin saturation and is expressed as a percentage.
The formula is:
Transferrin saturation = serum iron/ total iron binding capacity
Ferritin is the form iron takes when it is deposited and stored in cells. Extra ferritin is released from cells in inflammation, such as with infection or cancer. If ferritin in the blood is low it is highly suggestive of iron deficiency. If ferritin is high then this is difficult to interpret and is likely to be related to inflammation rather than iron overload. A patient with normal ferritin can still have iron deficiency anaemia, particularly if hey have reasons to have high ferritin such as infection.
Serum iron varies significantly throughout the day with higher levels in the morning and after eating iron containing meals. On its own it is not a useful measure.
TIBC can be used as a marker for how much transferrin is in the blood. It is an easier test to perform than measuring transferrin. Both TIBC and transferrin levels increase in iron deficiency and decrease in iron overload.
Transferrin saturation gives a good indication of the total iron in the body. In normal adults it is ~30%, however if there is less iron in the body transferrin will be less saturated and is iron levels of up transferrin will be more saturated. It can temporarily increase after eating a meal rich in iron or taking iron supplements so a fasting sample gives the most accurate results.
Acute liver damage can increase serum ferritin, serum iron, transferrin saturation and can decrease TIBC, due to the liver being a large store of iron
What are the normal ranges in iron deficiency anaemia
Serum ferritin 41-400ug/L
Serum iron 12-30umol/L
TIBC 45-80umol/L
Transferrin saturation 15-50%
How is iron deficiency managed
New iron deficiency without a clear cause should be investigated with suspicion. This involves doing an OGD and a colonoscopy to look for cancer of the GI tract.
Management involves treating the underlying cause and correcting the anaemia. The anaemia can be treated in three ways depending on severity.
- Blood transfusion: this will immediately correct eh anaemia but not the underlying iron deficiency and also carries risks
- Iron infusion eg cosmofer: there is a very small risk of anaphylaxis but it quickly corrects the iron deficiency. Should be avoided in sepsis s iron “feeds” the bacteria
- Oral iron eg ferrous sulfate 200mg TDS: Slowly corrects the iron deficiency. Can cause constipation and black stools. It is unsuitable when malabsorption is the cause of the anaemia.
When correcting iron deficiency anaemia with iron you can expect the haemoglobin to rise by ~10g/L per week
What is an acute transfusion reaction
Acute reactions occur within 24 hours of transfusion and include:
- Acute haemolytic,
- Febrile non-haemolytic
- Allergic
- Transfusion related acute lung injury (TRALI)
What is a delayed transfusion reaction
Delayed reactions occurdays to weeks after the transfusion and include:
- Delayed haemolytic transfusion reactions
- Transfusion associated graft versus host disease
- Post transfusion purpura
What is the aetiology of the 4 types of acute transfusion reactions
Acute haemolytic:
- Usually the result of ABO red-cell incompatibility
- Caused by clerical error resulting in mistransfusion
Allergic:
-Hypersensitivity reactions to allergens in the transfused component
Febrile non-haemolytic transfusion:
-Considered to be immune-mediated, although the mechanism appears to be multifactorial
Transfusion related acute lung injury (TRALI):
-Occurs as a result of granulocyte activation in the pulmonary vasculature, resulting in increased vascular permeability
What is the aetiology of the 3 types of delayed transfusion reactions
Delayed haemolytic transfusion reactions:
-Generally non-preventable, and the result of an anamnestic antibody response to non-ABO red cell antigens
Transfusion-associated graft-versus-host disease:
-Primarily observed in immunodeficient patients in which transfused white cells react with recipient antigens
Post transfusion purpura:
-Occurs as a result of prior sensitisation to foreign platelet antigen, usually during pregnancy
What is the pathophysiology of acute haemolytic type transfusion reaction
Typically result from ABO incompatibility.
The presence of preformed recipient antibodies to donor antigens results in complement activation, leading to intravascular haemolysis and its associated severe acute inflammatory cascade, which may ultimately progress to disseminated intravascular coagulation, shock and/or acute renal failure
What is the pathophysiology of allergic type transfusion reaction
Typically manifests as urticaria caused by a hypersensitivity reaction to allergen proteins in donor plasma.
In the most severe form, anaphylaxis (IgE mediated) may occur.
In IgA deficient patients, an anaphylacticoid (since non-IgE mediated) can occur as a result of anti-IgA antibodies in the recipient interacting with donor IgA
What is the pathophysiology of febrile non-haemolytic type transfusion reaction
May result in part from interaction between recipient antibodies directed against leukocytes present in the red-cell or plately unit transfused.
The formation of antigen-antibody complexes may result in complement binding and release of endogenous pyrogens.
May also result from the transfusion of proinflammatory substances inclusing cytokines, complement fragments and lipid compounds that are contained in the transfused unit’s plasma supernatant