Anaemia Overview

Pathological ↓ in the haemoglobin concentration of blood, resulting in a ↓ oxygen carrying capacity, and is:

Epidemiology and Risk Factors

Anaemia in preoperative patients in Australia is:

  • Common
    • 6% of females
    • 2% of males
    • Risk ↑ with age
      16% of patients over 75.
  • Usually due to iron deficiency

Pathophysiology

Anaemia of inflammation occurs due to:

  • ↑ Erythrocyte phagocytosis
    Activated macrophages remove more red cells from circulation.
  • ↓ Erythropoiesis
    Cytokines inhibit erythropoiesis, and may ↓ EPO expression.
  • ↓ Iron availability
    Inflammation stimulates hepcidin release, which promotes iron trapping in marrow and erythrocytes.

Aetiology

Common Causes of Anaemia
Microcytic Normocytic Macrocytic
  • Iron deficiency anemia
  • Thalassemia
    • α-Thalassemia
      Mild-severe anaemia, depending on number of affected genes.
    • β-Thalassemia
  • Anaemia of inflammation
    • Renal insufficiency
    • Chronic disease
  • Haemorrhage
  • Haemolysis
  • Iron and B12/folate deficiency
  • Bone marrow disorder
    • Multiple myeloma
    • Bony metastases
  • Vitamin B12 deficiency
  • Folate deficiency
  • Liver disease
  • Drugs
    • Alcohol
    • Hydroxyurea
    • Methotrexate
    • Trimethoprim

Clinical Features

Haemolysis:

  • Infection
    • Viral haemorrhagic fever
    • Malaria
  • Extracorporeal circuit

Assessment

History:

  • Fevers
  • Travel

Exam:

  • Jaundice
  • Haemoglobinuria
Varying concentrations of haemoglobinuria

Investigations

Bedside:

Laboratory:

Red cell abnormalities and iron studies are covered in more detail under Erythrocytes and Iron Studies.

  • Blood
    • FBE
      • Hb
      • MCV
      • MCHC
      • RCC
    • Blood film
      • Haemolysis
      • Sickle cells
    • CRP
      Performed if ferritin is raised in a microcytic anaemia, to exclude reactive causes.
    • Iron studies
      • Ferritin
        Assesses degree of iron deficiency.
        • Only reliable in absence of acute inflammation
          Ferritin is an acute phase reactant
        • Normal range will depend on lab assay, but in general:
          • Severe: ⩽30μg/mL
          • Moderate: 30-50μg/mL
          • Mild: 50-100μg/mL
      • Transferrin saturation
        • <20% suggestive of iron deficiency
        • Useful in moderate ferritin deficiency
    • Bilirubin
    • Haemolysis screen
    • Coagulation screen
  • Stool
    • Faecal occult blood test

Coombs test is:

  • Also known as antiglobulin testing
  • A test for autoantibodies against circulating erythrocytes
  • Diagnostic of autoimmune haemolytic anaemia
    Also used in identifying transfusion-relevant antibody.
  • Performed either by:
    • Direct antiglobulin testing
      • Detects antibodies bound to erythrocytes.
      • Patient blood washed in saline to remove plasma and unbound antibodies
      • Reagent added to detect bound IgG
    • Indirect antibody testing
      • Patient plasma mixed with foreign erythocytes of known antigenicity
      • Reagent added to detect patient antibody bound to foreign cells

Haemolysis screen consists of:

  • Reticulocyte count
    ↑ Due to ↑ marrow turnover.
  • Blood film
    • Schistocytes
      Mechanically fragmented erythrocyte, favours intravascular mechanical haemolysis.
  • LDH
    Present in many cells and so not specific for haemolysis (as opoposed to other cellular destruction). Substantial ↑ (4-5× ULN) favours intravascular over extravascular haemolysis.
  • Haptoglobin
    Binds free haemoglobin, and is non-specific for intravascular vs. extravascular haemolysis. Acute phase reactant and so result may be equivocal in inflammatory states.
  • Free Hb
    ↑ Due to cellular destruction.
  • Bilirubin
    ↑ Due to haemoglobin metabolism. Classically ↑ conjugated bilirubin, although unconjugated may ↑ in concurrent hepatic impairment.

Imaging:

Other:

  • Endoscopy

Diagnostic Approach and DDx

Management

Resuscitation:

Specific therapy:

  • Pharmacological
    • Iron supplementation
      If iron deficient.
      • Oral
        • Common
        • Cheap
        • Significantly limited by:
          • Time
            May take ⩾3 months of therapy to be effective, and 6-9 months for equivalent effect of one IV replacement.
          • Absorption
            Highly variable.
          • Intake
          • Non-compliance
            Significant GI side effects.
        • 80mg elemental iron given every second day
          Daily administration down-regulates hepcidin, and reduces absorption.
      • IV
        Generally used if ferritin deficiency is severe, or moderate with low transferrin saturation.
        • Facilitate rapid repletion of stores
        • Requires local pathway to facilitate
        • Newer preparations have much lower incidence of anaphylaxis
          Include iron polymaltose and iron carboxymaltose.
    • EPO
      For renal anaemia without nutritional deficiency; generally requires nephrologist consultation.
    • Blood transfusion
  • Procedural
  • Physical

Supportive care:

Disposition:

Preventative:

Marginal and Ineffective Therapies

Anaesthetic Considerations

Patients should be assessed 4-6 weeks pre-operatively.

The principles of patient blood management are covered under Patient Blood Management.

Complications

Prognosis

Anaemia is an independent risk factor for:

  • Mortality
  • Morbidity
  • Hospitalisation
  • ↓ Quality of Life

Key Studies

References

  1. Tefferi A. Anemia in Adults: A Contemporary Approach to Diagnosis. Mayo Clinic Proceedings. 2003;78(10):1274-1280. doi:10.4065/78.10.1274