Anaemia
Introduction
Anaemia is common and increases with age. It is a condition in which the absolute number of red cells in the circulation in abnormally low and is defined as a haemoglobin < 13g/dL in men and < 12g/dL in women. Red cells function by transporting oxygen bound to haemoglobin from the lungs to the tissues. Anaemic patients have impaired oxygen supply tissues and the symptoms of anaemia, what ever the cause, is secondary to tissue hypoxia.
Anaemia is independently associated with increased risk of morbidity and mortality and transfusion, which has it's own risks.
Anaemia is a finding not a diagnosis. Once identified the underlying cause needs to be sought. Evaluation of anaemia is a common problem in clinical practice and is frequently referred to the ED. The evaluation may be straightforward in an otherwise healthy individual with a single cause of anaemia, but in many cases the cause is not readily apparent and multiple conditions may be contributing, several of which are sinister. The anaemic patient is doing at least one of three things;
Bleeding
Not producing enough red cells
Destroying red cells
Causes of Anaemia
Bleeding
Acute haemorrhage of any cause
NB: Acutely bleeding patients may initially have a normal FBC including Hb
Chronic haemorrhage of any cause
Causes Iron Deficiency Anaemia, the most common cause of anaemia.
Hypochromic (↓MCHC) microcytic (↓MCV) anaemia.
↓ Serum Iron + Ferritin, ↑TIBC
Typically chronic gastrointestinal, menstruation or urinary tract losses but can be secondary to any chronic bleeding.
Fe deficiency anaemia can also occur with dietary deficits or decreased Fe absorption.
Decreased Red Cell Production
Megaloblastic Anaemia i.e. MCV
Usually due to B12 or Folate Deficiency resulting in impaired DNA synthesis in RBCs
Folate Deficiency = Dietary
B12 Deficiency = Autoimmune malabsorption a.k.a Pernicious anaemia
Marrow Failure
Aplastic anaemias = Pancytopaenia due to failure of marrow stem cells.
Causes = idiopathic, inherited, infections, irradiation, drugs
Red cell aplasia due to decreased or absent red cell precursors in the marrow
Infiltration of bone marrow e.g. metastatic cancer
Myelodysplastic Syndromes
Primarily occur in the elderly. Abnormal marrow stem cells produce dysfunctional RBCs. 1/3 go on to develop CLL
Anaemia of Chronic Kidney Disease
Decreased renal erythropoietin production = decr RBC production
Increased Red Cell Destruction
Usually normochromic (MCHC) + normocytic (MCV), ↑ LDH.
Lysis in the circulation = ↑ Bilirubin.
Lysis in reticuloendothelial system = Splenomegaly
Inherited Haemolytic Anaemias
e.g. Sickle Cell Anaemia, Thalassaemia, Hereditary spherocytosis, G6PD deficiency
abnormally structured RBCs are destroyed prematurely
Acquired Haemolytic Anaemia
Most are autoimmune and idiopathic. Other causes include malignancy, infection and some drugs
Microangiopathic Haemolytic Anaemia (MAHA)
i.e. non immune haemolysis. Usually increased RBC destruction due to abnormalities of the microvasculature
e.g. Disseminated intravascular coagulation (DIC), haemolytic uraemic syndrome (HUS), vasculitits, HELLP syndrome, thrombotic thrombocytopaenia purpura (TTP).
Mechanical Haemolysis
e.g. mechanical trauma with artificial heart valves, malaria, other infections.
Anaemia of Chronic Disease has complex pathophysiology and is likely due to a combination of decreased RBC production and decreased survival. Usually a mild to moderate normochromic normocytic anaemia.
Clinical Features
The severity of symptoms and signs relate to anaemia depend on several factors such as rate of development, extent of anaemia present, age of patient and the presence of comorbidities.
Symptoms
Patients with chronic, stable or insidiously developing anaemia may have no symptoms or signs
Fatigue, lethargy, weakness, orthostatic symptoms, syncope
Shortness or breath, palpitations, chest pain
Symptoms of underlying cause
PR bleeding, menorrhagia
Malignancy - altered bowel habit, weight loss, night sweats, bone pain.
Signs
Pallor - skin, lips, conjunctiva, mucous membranes
Acute haemorrhage - signs of haemorrhagic shock, postural hypotension, PR/PV bleeding etc
Those with anaemia of insidious onset are normovolaemic
May have signs of hyperdynamic circulation e.g. tachycardia, ejection systolic flow murmur or high output cardiac failure as a response to tissue hypoxia
Signs of underlying cause
Fe Def anaemia = glossitis, angular stomatitis, koilonychia (spoon nails)
Haematological abn = hepatosplenomegaly, lymphadenopathy, bone pain
Haemolysis = jaundice, splenomegaly
Sickle Cell = SOB, chest pain, hypoxia in chest crisis, bone pain
Clinical Investigations
Bedside
VBG
Immediate approximation of Hb result. Allows you to start looking for source of anaemia, planning for transfusion etc.
Signs of hypovolaemic shock —> acidosis, high lactate, low HCO3 + Base excess
POCUS
Guide resuscitation/identify sites of heamorrhage in shocked patients
ECG
Patients with pre-existing IHD may present with chest pain + acute coronary syndrome in setting of tissue hypoxia secondary to anaemia
Faecal Occult Blood
Rule in test only. Not used to rule out GI losses in someone with anaemia. May guide disposition planning in ED
Laboratory
FBC
Hb, WCC + Diff, Platelets, MCV, MCHC, Hct, Blood Film
U&E + LFTs + TFTs
? CKD, ↑ Bilirubin in haemolysis, Thyroid dysfunction as a cause.
Coagulation Studies
? coagulopathy as a cause of bleeding, ? bone marrow failure
Other specialist tests are not routinely ordered by EM but include;
Iron Studies (Serum Iron, Transferrin Sats, TIBC), B12, Folate, Ferritin
Reticulocyte count, EPO levels,
Bone marrow aspirate
Radiology
Choice of radiological investigation, if any, should be dictated by what the underlying cause of anaemia is thought to be.
Other
OGD + Colonoscopy
Chronic GI losses are a common cause of Fe Deficiency anaemia. The diagnosis is made by direct visualisation
Management + Disposition
Initial Resuscitation
Ensure adequate oxygenation
Find and control bleeding.
Fluid resuscitation if shocked. Fluid of choice is blood if evidence of haemorrhage.
Correct coagulopathy
Specific Treatment
Seek and treat the cause
A restrictive strategy (transfuse >7g/dL) is usually appropriate but risk stratify according to physiological reserve (e.g. age, co-morbidities especially cardiac) and predicted cause of illness (e.g. risk of bleeding) to determine threshold for transfusion
Supplement nutrition as indicated
Iron (PO or Infusion), B12, Folic Acid
Disposition
Those patients who are unwell or whose Hb is <7g/dL will require Medical/Haematology admission for treatment and work up
Those patients who are asymptomatic or mildly symptomatic with an acceptable Hb may be worked up as an outpatient and monitored closely by their GP
References
Capellina D. Anemia in Clinical Practice-Definition and Classification: Does Hemoglobin Change With Aging? Semin Hematol. 2015 Oct;52(4):261-9
Murray L, Little M. Ch 13.1 Anaemia; Haemotology Emergencies. Textbook of Adult Emergency Medicine. 4th Edition
George J et al. Diagnostic approach to suspected TTP, HUS, or other thrombotic microangiopathy (TMA). www.Uptodate.com
This blog was written by Dr Deirdre Glynn and was last updated on April 11th 2022