Sorting the anaemias by cause
Anaemia means insufficient oxygen-carrying capacity, and the shared findings are the same regardless of cause: fatigue, pallor, tachycardia, dyspnoea on exertion, dizziness and cold intolerance. What differs is the mechanism, and the exam tests you on the teaching attached to each mechanism.
Iron deficiency anaemia is the most common worldwide and produces small, pale red cells. Causes include chronic blood loss from menstruation or gastrointestinal bleeding, poor dietary intake and malabsorption. Teaching centres on oral iron: take it on an empty stomach for best absorption, pair it with a source of vitamin C such as orange juice, expect dark green or black stools, prevent constipation with fluid and fibre, and use a straw for liquid preparations to protect tooth enamel. Children's supplements are a leading cause of poisoning and must be stored safely.
Vitamin B12 deficiency produces large, immature cells and, uniquely, neurological findings: paraesthesia in the hands and feet, ataxia, impaired proprioception and confusion. Pernicious anaemia is the autoimmune form in which intrinsic factor is absent, and clients who have had gastric surgery or ileal resection require lifelong intramuscular or intranasal B12 because oral replacement cannot be absorbed. Folate deficiency looks similar on the blood film but has no neurological signs, and it is a key pre-conception concern for preventing neural tube defects.
Aplastic anaemia is bone marrow failure affecting all three cell lines, so the client is simultaneously anaemic, thrombocytopenic and neutropenic. Anaemia of chronic kidney disease results from reduced erythropoietin and is treated with erythropoiesis-stimulating agents, which require iron stores to be adequate and carry a hypertension and thrombosis risk.
| Type | Cause | Distinguishing feature | Key teaching |
|---|---|---|---|
| Iron deficiency | Blood loss, poor intake | Microcytic, low ferritin | Iron with vitamin C, empty stomach, dark stools expected |
| Vitamin B12 | Lack of intrinsic factor, ileal disease | Macrocytic plus neuropathy | Lifelong injections after gastrectomy |
| Folate | Poor intake, alcohol use, pregnancy | Macrocytic, no neuropathy | Leafy greens, fortified grains, prenatal supplementation |
| Aplastic | Marrow failure, drugs, radiation | All cell lines low | Infection and bleeding precautions |
| Chronic kidney disease | Low erythropoietin | Normocytic with high creatinine | Erythropoietin therapy; monitor blood pressure |
Sickle cell disease and crisis management
Sickle cell disease is an inherited disorder in which haemoglobin S distorts red cells under stress, causing them to occlude small vessels. Triggers are the exam's favourite target: dehydration, hypoxia, infection, cold exposure, high altitude, strenuous exercise and emotional or physical stress. Teaching therefore emphasises generous fluid intake, avoiding extremes of temperature, prompt treatment of infection, up-to-date immunisations, and avoiding unpressurised flight and high altitude.
A vaso-occlusive crisis presents with severe pain, most often in the back, chest, abdomen and extremities, with swelling of hands and feet in young children. The management priorities are hydration with intravenous fluids to reduce blood viscosity, oxygen if hypoxic, and aggressive pain control, typically with intravenous opioids on a scheduled or patient-controlled basis rather than as-needed intramuscular doses. Warmth is applied to painful areas; cold is contraindicated because it causes vasoconstriction and worsens sickling.
Acute chest syndrome is the life-threatening complication to recognise: fever, chest pain, cough, hypoxia and a new pulmonary infiltrate. It requires urgent escalation, oxygen, antibiotics and often transfusion. Splenic sequestration in children presents with sudden splenomegaly, pallor and shock and is also an emergency.
Hydroxyurea reduces crisis frequency by increasing fetal haemoglobin. It suppresses the bone marrow, so blood counts are monitored, and it is teratogenic, so contraception counselling is required.
- •Triggers: dehydration, hypoxia, infection, cold, stress, altitude
- •Crisis care: fluids, oxygen, opioid analgesia, warmth
- •Never apply cold or restrict fluids during a crisis
- •Acute chest syndrome is an emergency
- •Hydroxyurea reduces crises but suppresses marrow
Platelets, neutrophils and precaution answers
Thrombocytopenia is defined as a platelet count under 150,000. Bleeding precautions begin below 50,000, and spontaneous bleeding including intracranial haemorrhage becomes a real risk below 20,000. Precautions include a soft toothbrush, electric razor, no rectal temperatures, suppositories or enemas, no intramuscular injections when avoidable, prolonged pressure after venipuncture, fall prevention, and avoiding aspirin and NSAIDs. Immune thrombocytopenic purpura is treated with corticosteroids and sometimes splenectomy.
Neutropenia is measured by the absolute neutrophil count, and a value under 500 represents severe risk. The single most important teaching is that fever in a neutropenic client is an emergency: obtain cultures and start broad-spectrum antibiotics without waiting. Because neutrophils produce the signs of inflammation, a neutropenic client may have a serious infection with no redness, no swelling and no purulence — a low-grade temperature may be the only clue.
Neutropenic precautions include meticulous hand hygiene, a private room, avoiding crowds, no fresh flowers or standing water, no raw or undercooked foods and thorough washing of fruit and vegetables, avoiding people with infections, and avoiding live vaccines. Filgrastim stimulates neutrophil production and commonly causes bone pain, which is expected rather than alarming.
Reinforce these patterns with our oncology and chemotherapy article, the blood transfusion guide and the infection control post, and then test yourself on the adult health and fundamentals question banks.
- •Platelets under 50,000: full bleeding precautions
- •Platelets under 20,000: spontaneous bleeding risk
- •ANC under 500: severe neutropenia, protective measures
- •Neutropenic fever: cultures then antibiotics immediately
- •No live vaccines, raw foods or fresh flowers when neutropenic