The significance of potassium levels in a hospital population

Abstract

The present study was undertaken to investigate whether the abnormal potassium levels denned by deviations from our reference range were associated with clinical disease. Reference ranges were determined on heparinized samples from more than 200 blood donors. The potassium range obtained was 3.0-4.2mmol/1 with a mean of 3.6 and a standard deviation of 0.3. This reference range was thought to be skewed to the left. Therefore further blood samples were collected into tubes containing lithium heparin (as were the original blood samples), sodium heparin and plain tubes. The results from the lithium and sodium heparin agreed and were identical to the original data. The serum potassium from the plain tubes was on an average 0.7mmol/1 higher. Hence the range of 3.0-4.2 was taken as an acceptable biological range. More than 100 consecutive abnormal potassium levels were investigated. The precision of the method is ± 0.1mmol/1. Therefore even small deviations from the reference range were considered abnormal. Of these, 68% were in the hyperkalaemic range and 32% in the hypokalemic range. The most common cause of hyperkalaemia was an over zealous replacement of potassium by either oral or parenteral routes of administration. Renal insufficiency and the use of potassium sparing diuretics were other notable causes of hyperkalaemia. Hypokalaemia was most commonly due to diarrhoea or a combination of vomiting and diarrhoea. The other prominent cause was inadequate replacement of potassium with diuretic therapy. It appears that a closer liaison between clinician and pathologist is necessary and that potassium levels be monitored when replacement therapy is considered.