Pharmacology
Fluids and Electrolytes
Question 91 of 180
Regarding potassium replacement, which of the following statements is INCORRECT:
Answer:
Potassium supplements are seldom required with the small doses of diuretics given to treat hypertension; potassium-sparing diuretics e.g. spironolactone (rather than potassium supplements) are recommended for prevention of hypokalaemia due to diuretics such as furosemide or the thiazides when these are given to eliminate oedema.Potassium Supplements
Pharmacology / Fluids and Electrolytes
Last Updated: 26th March 2019
Indications
Compensation for potassium loss is particularly necessary:
- in those taking digoxin or antiarrhythmic drugs, where potassium depletion may induce arrhythmias
- in patients in whom secondary hyperaldosteronism occurs, e.g. renal artery stenosis, cirrhosis of the liver, nephrotic syndrome, and severe heart failure
- in patients with excessive losses of potassium in the faeces, e.g. chronic diarrhoea associated with intestinal malabsorption or laxative abuse
Other groups which may be prone to hypokalaemia include:
- the elderly who frequently take inadequate amounts of potassium in the diet (although this must be balanced with the risks of renal insufficiency)
- patients on long-term drug therapy with drugs known to cause hypokalaemia e.g. corticosteroids, or diuretics
Administration
Potassium salts may be given by mouth to prevent deficiencies or to treat established deficiencies of mild or moderate degree. Potassium salts cause nausea/vomiting and poor compliance is a major limitation to their effectiveness.
In established hypokalaemia, larger oral or intravenous doses may be required; hypokalaemia is frequently associated with chloride depletion and metabolic alkalosis and this must also be corrected.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
