Hypokalemia is a condition when the concentration of serum potassium is less than 3.5 mmol/l. Hypokalemia affects female and male equally. Patient who suffers from HIV, eating disorders and after bariatric surgery are easily predisposed to hypokalemia. Hospitalized patient may suffer from hypokalemia. Hypokalemia is the commonest electrolytes abnormalities in clinical practice. Hypokalemia is associated with acute gastrointestinal illness.
There are a few genetic disorders that are associated with hypokalemia such as, familial interstitial nephritis and Liddle syndrome. Familial hypokalemic periodic paralysis may also cause hypokalemia. The disorder may occur after exercise and high ingestion of sodium and carbohydrates. Patient should be advised to increase the intake of dietary potassium if thiazide diuretic and loop diuretic are administered.
The common causes of hypokalemia may include type I and type II renal tubular acidosis,poorly controlled diabetes ( osmotic diuresis), decreased intake of potassium mostly in anorexic, elderly and alcoholic, intracellular shift of potassium ( mostly due to drug intoxication such as toluene, caffeine and theophylline), hypokalemic periodic paralysis, excess of insulin, excess of beta adrenergic catecholamine due to beta agonist or acute stress, excess of glucocorticoids ( mostly due to exogenous steroids, Cushing syndrome and ectopic adrenocorticotrophic hormone), gastrointestinal loss of potassium ( due to laxative abuse, malabsorption, bulimia, radiation enteropathy, chemotherapy, diarrhea, vomiting, nasogastric tube, villous adenoma, fistulas and uretersigmoidoscopy) and renal potassium loss.
Renal loss of potassium is due to excess mineralocorticoids or specific intake of drugs. Excess mineralocorticoids occur as a result of Gitelman syndrome, cirrhosis, renin producing tumors, malignant hypertension, nephrotic syndrome, congestive heart failure, primary hyperaldosteronism, Bartter syndrome, renovascular hypertension, vasculitis, Liddle syndrome and exogenous mineralocorticoids ( due to intake of glycyrrhizic acid in licorice, steroids and carbenoxolone) Renal loss of potassium may also occur due to intake of drug such as aminoglycoside and amphotericin B.
Mild cases of hypokalemia (3.0-3.5 mmol/l) may present with no symptoms. In severe cases of hypokalemia , patient may present with neuromuscular symptoms and signs. These may include disorders of the smooth muscle and the skeletal muscle.
Defect in smooth muscle may present with constipation, ileus and gastrointestinal hypo motility. A defect in skeletal muscle is characterized by weakness to total paralysis which affects the proximal muscle more than distal muscle and lower limb more than upper limb. Necrosis of the skeletal muscle and cardiac muscle are common.
In severe case, respiratory muscle will also be affected which may lead to rhabdomyolysis and respiratory arrest. Patient may also suffer from renal abnormalities such as polydipsia, myoglobinuria, nocturia and polyuria. Besides that patient may also suffer and develop hyperglycemic states, hypotension, ventricular arrhythmias and cardiac arrest.
ECG in hypokalemic patient may reveal depression of the ST segment, inversion of T waves, flattening of the T waves, ventricular ectopic waves and the present of U waves. U waves are presented as small deflection after T waves . U waves commonly present in V2 and V3. Arrhythmias may associated with hypokalemia because hypokalemia may lead to increase in the resting potential of the myocytes. This will lead to an increase in the refractory period.
Imaging technique such as CT scan is useful to scan for any excess of mineralocorticoids in adrenal glands.
The common differential diagnoses of hypokalemia are thyrotoxicosis and spurious hypokalemia. Spurious hypokalemia occurs when blood with high white blood cell count able to stand at room temperature. The white blood cell count will extract the potassium ion from the plasma. In cases, where the serum potassium is more than 2.5 mmol/l, oral therapy is considered. This case is known as a non emergent hypokalemia with no cardiac manifestation present. The treatment of non emergent hypokalemia may include oral potassium chloride. If oral therapy is not feasible, then IV potassium should be given. Patient may not be able to take oral potassium chloride due to vomiting. It is important to monitor cardiac rhythm closely.
Patient may also present with co existing disorders such as phosphate deficiency and metabolic acidosis . In this cases, other forms of potassium salt such as potassium bicarbonate or phosphate may be considered.
In cases, where the serum potassium is less than 2.5 mmol/l, IV therapy is considered. This is known as an emergency condition. Here, serum magnesium level is monitored. Low serum magnesium level should be treated and replaced. It is hazardous to replace potassium while magnesium is low.
There are a few things need to be remember while treating hypokalemic patient. Aggressive treatment is considered in patient with diabetic ketoacidosis or currently under digitalis. In these cases, there will be an intracellular shift in potassium.
Patient with renal insufficiency, diabetic or elderly may require frequent check of serum potassium level. Potassium replacement therapy carries a high risk of hyperkalemia.
Certain types of medication may magnify the risk of hyperkalemia. This medication may include potassium sparing diuretics such as angiotensin converting enzyme inhibitor, spironolactone, amiloride and triamterene. Patient who currently receiving IV therapy may require regular potassium level checked and continuous cardiac monitoring.
Dietary supplementation is considered in case of mild hypokalemia ( 3.0- 3.5 mmol/l). The dietary supplementation may include bananas, raisins, dried apricots, oranges and prunes.
Patient with hypokalemia carries high morbidity and mortality rates due to cardiac arrhythmias. Hypokalemia can be resolved with no further action if the underlying causes are identified. These include removal of adrenal tumor, discontinuation of diuretics and resolution of diarrhea. The common complication of hypokalemia may include increase risk of digoxin toxicity and developing hyperkalemia during the course of treatments.
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