blood analysis

Low Potassium in Blood - Hypokalemia

Generality

Hypokalaemia (or hypokalaemia) is the reduction of potassium concentration in the blood.

This condition recognizes various causes, but generally depends on a lack of body reserves of potassium or an abnormal displacement of the same within the intracellular compartment.

The most frequent reasons behind low potassium in the blood are: kidney diseases, metabolic disorders, losses from the gastrointestinal tract, the use of some drugs (including diuretics and laxatives) and dialysis.

Hypokalaemia may be at the origin of arrhythmias, muscle weakness, hypotension, confusion, alkalosis (an imbalance in the pH of the blood, due to an excess of alkaline substances) and shallow breathing.

What's this

Potassium: what it is and main functions

  • Potassium is an essential mineral salt for our body. This element plays a role in maintaining hydro-saline balance and is the basis of important neuromuscular and cardiac functions.
  • In resting conditions, most of the potassium is found inside the cells (while sodium and calcium are concentrated mainly outside the cells). The existence of a gradient (induced by its high intracellular concentration and its low extracellular concentration) is necessary for the excitability of nerve fibers, muscle and cardiac cells . In other words, along with sodium and calcium, potassium maintains the electrical potential of cell membranes, necessary for the conduction of nerve impulses and muscle contraction .

    The intracellular potassium concentration is maintained by means of an active transport system (called sodium-potassium pump).

  • Potassium is introduced into the body with nutrition and, once absorbed in the intestine, passes into the blood; the kidneys intervene in the event that it is necessary to increase the excretion or reabsorption of the mineral. Depending on the needs of organs and tissues, then, to maintain its levels within the normal range, the organism can resort to the reserves of the element located inside the cells.
  • The elimination of potassium occurs mainly with urine, but a small amount can be disposed of with faeces.

Hypokalemia: definition

Hypokalaemia (or hypokalemia ) is defined as a serum potassium concentration equal to or less than 3.5 mEq / l .

This condition can result from a deficit of the total body deposits of the mineral, secondary to a reduced dietary intake or excessive losses with the urine or from the gastrointestinal tract.

Another frequent cause of hypokalemia is the abnormal displacement of potassium within the intracellular compartment.

It should be pointed out that hypokalemia can be multifactorial, ie the origin of this situation may depend on several mechanisms or etiologies, which occur simultaneously.

The causes can be exogenous or endogenous. In any case, the alteration of potassium homeostasis is dangerous and requires immediate medical intervention.

Why do you measure

The potassium test is indicated to verify the possible variation of the potassium . This analysis is often performed as part of routine analyzes to check the patient's general health.

Potassium is also evaluated in the presence of symptoms of hypokalaemia (such as arrhythmias, muscle weakness and tremors) or when the doctor suspects an acid-base or hydrosaline imbalance.

The potassium test is carried out at regular intervals in patients suffering from hypertension and kidney problems, dialysed or subjected to a therapeutic treatment based on diuretic drugs.

Often, this examination is associated with that of sodium, as these two parameters are closely related to each other (as the levels of potassium increase, those of sodium decrease).

Also certain pathologies (in particular: heart failure, arterial hypertension and kidney diseases) require regular monitoring of kaliemia, in order to identify any changes early.

Normal values

The blood potassium level is normally between 3.5 and 5.0 mEq / l. This value is influenced by several factors: hormones, blood pH, dietary intake, renal function and circadian rhythm.

In the presence of serum potassium concentrations less than 3.5 mEq / l, we speak of hypokalaemia (or hypokalemia). More in detail, this condition is defined:

  • Mild hypokalaemia : potassium values ​​between 3.0 and 3.5 mEq / l;
  • Moderate hypokalaemia : 2.5 - 3.0 mEq / l;
  • Severe hypokalaemia : <2.5 mEq / l.

Values ​​above 5.0 mEq / l indicate a hyperkalaemia (hyperkalemia) situation.

Low Blood Potassium - Causes

Low blood potassium may occur due to increased renal elimination. This phenomenon may depend on numerous congenital and acquired renal diseases, such as:

  • Renal tubular acidosis;
  • pyelonephritis;
  • Nephrotic syndrome;
  • Nephrogenic insipid diabetes;
  • Fanconi syndrome (characterized by dysfunction of the proximal renal tubules, which causes an excessive loss of potassium and other molecules through the urine);
  • Liddle syndrome (rare hereditary form of hypertension associated with decreased plasma levels of potassium, renin and aldosterone);
  • Bartter syndrome (characterized by hypokalemic alkalosis, elevated levels of plasma renin and aldosterone, arterial hypotension and vascular resistance to angiotensin II);
  • Gitelman syndrome (also known as hypokalaemia-familial hypomagnesemia).

Potassium loss can be caused by endocrine disorders associated with excess adrenal steroids, including:

  • Cushing syndrome;
  • Primary and secondary hyperaldosteronism;
  • Conn syndrome (pathology of the adrenal glands characterized by excessive production of the hormone aldosterone);
  • Rare renin-secreting tumors.

Hypokalaemia may occur even when gastrointestinal potassium losses occur, as in the case of:

  • Chronic diarrhea;
  • He retched;
  • ileostomy;
  • Villous adenoma of the colon;
  • Biliary or intestinal fistula;
  • Ulcerative colitis;
  • Gastro-enteric tract neoplasms;
  • Ingestion of ion exchange resins (drugs that bind potassium and greatly reduce absorption).

As for the diet, the following conditions may predispose to hypokalemia:

  • Insufficient dietary intake of potassium (<1g / day);
  • Magnesium deficiency (reduced intake or increased loss);
  • Anorexia;
  • Malabsorption syndromes;
  • Alcoholism.

Another cause of low values ​​of potassium in the blood is the increase in the displacement of the same element from the blood to the cells (transcellular passage). This can occur in the event of:

  • Glycogenesis during total parenteral nutrition or enteral hyperalimentation (which stimulates insulin secretion);
  • Insulin therapy;
  • States of hyperinsulinemia;
  • Thyroid hyperactivity (hyperthyroidism);
  • Stimulation of the sympathetic nervous system (especially with β2-agonists that increase potassium cellular uptake);
  • Respiratory alkalosis;
  • Periodic hypokaliem paralysis (Westphal's disease).

The reduction of plasma potassium can also occur due to the ingestion of substances such as glycyrrhizin (present in licorice and used in the manufacture of chewing tobacco), dialysis and the intake of certain drugs.

The medicines that most commonly cause hypokalemia include:

  • Diuretics, particularly those potassium-dispersing;
  • Laxatives (especially when abused);
  • Amphotericin B;
  • Penicillin at high doses;
  • Theophylline (both acute and chronic intoxication);
  • ACTH and corticosteroids.

Possible associated symptoms

Mild hypokalemia is asymptomatic, while the moderate form typically determines:

  • Asthenia (fatigue) and easy fatigue;
  • Anorexia;
  • Weakness and muscle cramps;
  • Sensation of heavy legs;
  • Constipation and / or paralytic ileum.

A lack of potassium in severe blood can cause:

  • polyuria;
  • Rhabdomyolysis;
  • Confusional state
  • Breathing difficulties;
  • Tachycardia;
  • Cardiac arrhythmias up to cardio-circulatory arrest;
  • Decreased osteotendinous reflexes up to the (rare) ascending paralysis of the flaccid type.

Cardiac arrhythmias are common in hypokalaemia, especially in patients with pre-existing cardiac conditions and / or in digital therapy (cardiotonic drug).

How to measure it

For the potassium test it is necessary to undergo a simple blood test.

Preparation

No special preparation rules are required before undergoing potassium testing.

Fasting is recommended, although not necessary. However, it is necessary to remember to tell the doctor which type of drug therapy you are following, as many medicines can influence the outcome of the analysis.

Interpretation of Results

Hypokalaemia may depend on many causes; among the most frequent there are tubular renal disorders, metabolic disorders, losses from the gastrointestinal tract and dialysis.

Among the reasons of low potassium in the blood must also be remembered the taking of drugs, such as diuretics and laxatives.

Low Potassium in Blood: Possible Causes

Renal and gastrointestinal losses

  • Renal tubular disorders and other nephropathies
  • Prolonged diarrhea and vomiting
  • Villous adenoma of the large intestine
  • Nephrogenic insipid diabetes

Transcellular passage / Cell potassium uptake

  • Insulin therapy
  • Alkalosis (respiratory)
  • Periodic hypokaliem paralysis (Westphal's disease)

drugs

  • Diuretics
  • Laxative abuse
  • Licorice
  • Steroids

Other conditions

  • Endocrine diseases : hyperaldosteronism and Cushing's syndrome
  • Dialysis
  • Diet : reduced potassium intake or magnesium deficiency, anorexia and alcoholism
  • Burns and profuse sweating

How to control low potassium in the blood

The therapeutic approach depends on the severity of hypokalemia and the triggering cause.

A very important role for potassium intake is played by the diet . To increase the levels of this element when they are too low, it is possible to intervene by modifying one's eating habits, making more room for the many potassium-rich foods, starting with fruit and vegetables, and limiting cooking salt .

Potassium is found in numerous foods, but some of them are particularly rich in this mineral. There is no real diet for hypokalemia, but it is possible to include some of the most potassium-rich foods in your food plan, such as: fresh fruit (bananas, apricots and kiwis) and dried (hazelnuts, chestnuts and prunes), vegetables (beets, spinach and zucchini), fish (smoked salmon, sardines, trout and mackerel) and legumes (borlotti beans and chickpeas).

When the diet is not enough, specific dietary supplements can be used on the advice of your doctor, to be taken for a few weeks.

Regarding the pharmacological approach, mild forms of hypokalemia are generally treated with oral potassium chloride administration .

Instead, potassium is administered intravenously in the following situations:

  • The potassium level is dangerously low and / or the patient continues to lose too much mineral salt;
  • Oral supplements are not effective;
  • Low potassium levels cause abnormal heart rhythm.

The addition of triamterene or spironolactone to therapy may be helpful in patients treated with diuretics, which become hypokalaemic sporadically. This approach must be avoided, however, in the presence of renal insufficiency, diabetes or other interstitial renal diseases.

If the potassium deficiency is rather severe, hospitalization may be necessary: ​​in these cases, in fact, the help of the doctor is very important.