Severe hypokalemia – a case history

In health, plasma potassium concentration is maintained within the approximate range of 3.5-5.0 mmol/L. Hypokalemia, a very common electrolyte disturbance – present in up to 20 % of hospitalized patients – is diagnosed if plasma potassium is less than 3.5 mmol/L. 

Although mild hypokalemia is often asymptomatic, a greater degree of hypokalemia can result in signs and symptoms that reflect the importance of maintaining normal plasma potassium concentration for normal neuromuscular transmission and electrical conduction within heart muscle (myocardium). 

Severe hypokalemia (usually defined as plasma potassium <2.5 mmol/L) is associated with symptomatic effect on neuromuscular function that can range from mild muscle weakness and associated fatigue to severe paralysis affecting all four limbs. Involvement of cardiac or respiratory muscle can result in life-threatening arrhythmia or respiratory failure. A case history of severe hypokalemia was recently published. 

The patient was a 26-year-old professional bodybuilder in previous good health who was in the habit of misusing drugs (anabolic steroids, growth hormone, etc.) to improve muscle bulk. In preparation for a competition he decided for the first time to take the loop diuretic frusemide to remove excess water, a strategy apparently used by some bodybuilders to improve muscle definition. 

He took 2 × 80 mg tablets 24 and 48 hours before the competition; the diuretic effect resulted in a weight loss of 6 kg by the morning of the competition. The day after the competition he felt unusually tired and slept during the day. On waking he was unable to move his arms and legs and had palpitations. He was fortunately able to call for the help of his neighbor who arranged immediate ambulance transfer to hospital. 

On admission his plasma potassium was just 1.6 mmol/L and ECG showed characteristic signs of hypokalemia. Treatment with potassium supplements was quickly initiated and over the next 7 hours his condition improved and plasma potassium rose to 3.9 mmol/L. The next morning he was discharged from hospital in good health. 

In discussion of the case history the authors briefly review the many causes and potentially fatal consequences of severe hypokalemia. In this case the cause of hypokalemia was excessive loss of potassium in urine due to the potassium-wasting diuretic, frusemide. Hypokalemia is a well-documented adverse effect of this, and other commonly prescribed “potassium-wasting” diuretic drugs.