Hypokalaemia: common things occur commonly - a retrospective survey

Abstract

Objectives: To define the causes of hypokalaemia in an unselected adult population.

Design: Retrospective survey of biochemistry database.

Setting: District general hospital in southwest Scotland.

Participants and main outcome measures: There were 187,704 measurements of urea and electrolytes in 2010. Sixty-one patients had serum potassium <2.5 mmol/L on at least one occasion.

Results: Average age of the patients was 71 (range 33-99) years. The most common causes were diarrhoea and/or vomiting (51% of cases), diuretic therapy (47%), nutritional causes including poor dietary intake, re-feeding syndrome and inadequate potassium supplementation when patients were nil by mouth (37%). In 25% of patients a transient and profound fall in serum potassium appeared to coincide with their acute illness. Acute alcohol intoxication and/or alcohol withdrawal were prominent features in 11% of patients. More than one cause was commonly present. There were no cases of Bartter's, Gitelman's or Liddle's syndromes or of hypokalaemic periodic paralysis in this study.

Conclusions: Severe hypokalaemia <2.5 mmol/L occurs at least once a week in a district general hospital with a catchment population of around 150,000, suggesting there may be around 300 cases a week in the UK (population around 50,000,000). Diuretics, vomiting and diarrhoea are commonly implicated as are nutritional causes, acute illness and alcohol. Bartter's, Gitelman's, Liddle's syndrome and hypokalaemic period paralysis are all extremely uncommon.

Figure 1

Mechanisms of potassium re-absorption and secretion in the principal cell and intercalated cell of the cortical collecting duct (Source: Kumar and Clark 2010)

Figure 2

Causes of severe hypokalaemia in southwest Scotland 2010

Figure 3

Overview of potassium homeostasis

Figure 4

Potassium regulation by the proximal and distal nephron of the kidney

Figure 5

Causes of hypokalaemia

Figure 6

Mechanism of hypokalaemia in diarrhoea and vomiting

Figure 7

Importance of serum bicarbonate in evaluation of hypokalaemia

Figure 8

Mechanism of hypokalaemia with diuretic therapy

Figure 9

Importance of serum bicarbonate in evaluation of hypokalaemia; DKA=diabetes ketoacidosis