Thrombocytosis is a high platelet count >400/450 × 10 9 It may be secondary to a myeloproliferative disorder or another pathological process. Causes You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here

Thrombocytopenia is a low platelet count below 150 × 10 9 The causes of a low platelet count can be grouped according to reduced production, decreased survival or sequestration in the spleen. Causes Reduced production ● Aplastic anaemia ● Drugs, e.g. tolbutamide, alcohol, cytotoxic agents ● Viral infections, e.g. EBV, CMV ● Myelodysplasia ● Bone marrow infiltration, e.g. carcinoma, leukaemia, myeloma, myelofibrosis ● Megaloblastic anaemia…

Polycythaemia is an increase in red cell concentration above the normal limit, usually accompanied by a corresponding increase in haematocrit and haemoglobin concentration. Polycythaemia can be ‘real’ due to a true increase in red cell concentration or ‘apparent’ due to low plasma volume (e.g. dehydration). Primary polycythaemia (polycythaemia vera) is due to a neoplasm of the myeloid cells whilst secondary polycythaemia is due to raised erythropoietin…

Leucopenia is a reduction in circulating white blood cells. The normal range is 4–11 × 10 9 In practice, the commonest form is neutropenia – a deficiency of neutrophil granulocytes. Neutropenia may be selective or part of a pancytopenia. Causes Neutropenia You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log…

Leucocytosis is an increase in the absolute count of circulating white blood cells. The normal range is 4–11 × 10 9 It may involve any of the types of white cells, but a polymorphonuclear leucocytosis, i.e. neutrophilia, is the most common. Causes Neutrophilia Physiological ● Neonates ● Exercise ● Pregnancy ● Childbirth ● Lactation ● Stress Bacterial infection, e.g. acute appendicitis, pyelonephritis Acute non-infective inflammation…

Disorders of clotting can present with an increased tendency to clotting (thrombophilia) or a decreased ability to form clots and therefore an increased risk of bleeding. Causes Increased clotting Congenital ● Factor V Leiden deficiency ● Protein C deficiency ● Protein S deficiency ● Antithrombin III deficiency Acquired ● Malignancy ● Pregnancy ● Infection ● Prolonged immobility ● Autoimmune: anti-phospholipid syndrome (can be related to SLE)…

Anaemia is defined as a haemoglobin concentration of <13.5 g/dL in men and <11.5 g/dL in women. Classification of anaemia according to red cell indices is useful because specific investigations can be tailored accordingly. Causes Microcytic (MCV <80 fL) ● Iron deficiency ● Anaemia of chronic disease ● Thalassaemia (more common in certain groups) Normocytic (MCV 80–95 fl) ● Acute blood loss ● Haemolytic anaemia ●…

Blood urea is a useful test of renal function. However, other factors such as liver failure, dehydration and protein breakdown may alter levels of blood urea. The normal level of blood urea is 2.5–7.8 mmol However, values may be lower in pregnancy and the newborn, and in the elderly, values may be slightly increased due to lack of renal concentration. Causes You’re Reading a Preview Become…

Respiratory alkalosis is a common disorder in critically ill patients. It occurs when carbon dioxide is lost via excessive pulmonary ventilation (↑ pH, ↓ p CO 2 ). Compensatory mechanisms are: ■ ↓ HCO 3 − by bicarbonate buffer system ■ ↑ H + by kidneys (slow process – may take several days). Causes (any cause of hyperventilation) Central nervous system ● Pyrexia ● Pain ●…

Respiratory acidosis is caused by CO 2 retention due to inadequate pulmonary ventilation (↓ pH, ↑ pCO 2 ). Compensatory mechanisms are: ■ ↑ HCO 3 − by bicarbonate buffer system ■ ↓ H + by kidneys (can take several days). Causes (any cause of hypoventilation) (all causes of respiratory acidosis require urgent assessment) Impaired gaseous exchange ● Chronic obstructive pulmonary disease ● Alveolar disease, e.g.…

Metabolic alkalosis is caused by an increase in HCO 3 − or decrease in H + (↑ pH,↑HCO 3 − ). Compensatory mechanisms are: ■ ↑ pCO 2 by hypoventilation (limited by hypoxia) ■ ↓ HCO 3 − by kidneys. Causes You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in…

Metabolic acidosis is caused by increased production of hydrogen ions from metabolic causes or from excessive bicarbonate loss (pH ↓, HCO 3 − ↓). Compensatory mechanisms are: ■ ↓ pCO 2 by hyperventilation ■ ↓ H + by kidneys (unless in renal failure). Causes (all causes of metabolic acidosis require urgent assessment) Excessive production of h + ● Diabetic ketoacidosis ● Lactic acidosis secondary to hypoxia,…

The normal range of serum magnesium is 0.7–1.0 mmol Hypomagnesaemia refers to a serum level below 0.7 mmol Causes You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here

Hypocalcaemia is a serum calcium of <2.1 mmol/L (normal range 2.1–2.6 mmol/L) with an ionised fraction <0.8 mmol Causes Associated with high serum phosphate ● Chronic renal failure ● Hypoparathyroidism ● Rhabdomyolysis ● Phosphate therapy You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here

Hypercalcaemia is a serum calcium >2.62 mmol/L (normal range 2.1–2.6 mmol/L). It may be an asymptomatic laboratory finding. Symptoms usually become apparent with levels >3.50 mmol Causes ● Malignancy ■ Solid tumour with lytic bony metastases, e.g. Ca breast, bronchus ■ Solid tumours with humoral mediation, e.g. inappropriate PTH secretion with carcinoma of the bronchus, carcinoma of the kidney ■ Multiple myeloma ● Hyperparathyroidism (primary, secondary,…

The normal serum sodium level is 135–145 mmol Hyponatraemia refers to serum sodium levels of <135 mmol/L, and serum sodium of <120 mmol/L is considered severe. Causes Hypovolaemic ● Gastrointestinal losses ● Diarrhoea ● Vomiting ● Enterocutaneous fistula ● Renal sodium losses ● Diuretics ● Osmotic diuresis (e.g. hyperglycaemia) ● Renal failure ● Other sodium losses ● Burns ● Ascites ● Crush injuries ● Peritonitis You’re…

The normal serum sodium level is 135–145 mmol Hypernatraemia refers to a serum sodium level >145 mmol Causes Decreased water intake ● Confusion You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here

Hypokalaemia is a reduced blood level of potassium <3.5 mmol Causes You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here