Hypokalemia in the elderly
Introduction
Introduction to hypokalemia in the elderly Serum potassium levels <3.5mmol / L, the overall potassium is normal or reduced, known as hypokalemia. When the body's hypokalemia occurs, it will affect the heart's blood vessels, central nervous system, digestion, urinary and muscle systems. Many diseases can be accompanied by changes in blood potassium. The safe range of changes in blood potassium is very small. Whether it is caused by hypokalemia or hyperkalemia, it can cause severe dysfunction of the body and even stop the heart. It is one of the important factors for death of many diseases. . basic knowledge The proportion of sickness: 0.030% - 0.050% Susceptible people: the elderly Mode of infection: non-infectious Complications: arrhythmia paralytic ileus renal failure
Cause
The cause of hypokalemia in the elderly
(1) Causes of the disease
Drug factor (70%)
The improper use of diuretics leads to the imbalance of water, electrolytes and acid-base balance, which may be the most common cause of hypokalemia in the elderly. In the case of diabetic ketoacidosis, body potassium loss is often masked.
Electrolyte disturbance (25%)
There are many reasons for hypokalemia. In summary, there is no reduction in intake, excessive loss, and intracellular and extracellular metastasis leading to hypokalemia caused by imbalance of water, electrolytes, and acid-base balance.
(two) pathogenesis
Hypokalemia can weaken the depolarization of the cell membrane, affect the myoelectric conduction, leading to weakening of muscle paralysis and contractility; hypokalemia can lead to tubular vacuolar degeneration and metabolic alkalosis.
Prevention
Prevention of hypokalemia in the elderly
When the elderly infusion of potassium, it is necessary to pay attention to the speed of the liquid, should not be too fast, should closely observe the heart rate, pulse and blood pressure changes, and pay attention to the amount of urine, see the principle of urine potassium.
Complication
Complications of hypokalemia in the elderly Complications, arrhythmia, paralytic ileus, renal failure
Concurrent arrhythmia, paralytic ileus, renal failure and so on.
Symptom
Symptoms of hypokalemia in the elderly Common symptoms Tired potassium excretion isotonic urine polydipsia ambiguous metabolic low potassium rhabdomyolysis polyuria hypokalemia arrhythmia
Common symptoms of hypokalemia in the elderly are fatigue, confusion and weakening of muscles due to skeletal muscle function damage, severe hypokalemia can cause muscle paralysis, gastrointestinal smooth muscle can also be affected, showing no Dynamic intestinal paralysis, but rhabdomyolysis is rare.
The fatal manifestations of hypokalemia are those that affect heart function and cause a variety of arrhythmias, especially those with pre-existing heart disease or taking digitalis.
Chronic hypokalemia often causes interstitial nephritis and decreased tubular concentrating function, manifested as polyuria, secondary polydipsia and isotonic urine.
Examine
Examination of hypokalemia in the elderly
When clinically suspected hypokalemia, the following tests should be performed to determine the diagnosis.
1. Determination of serum potassium
Patients with hypokalemia have serum potassium <3.5mmol/L. Patients with acidosis or dehydration are deficient in potassium but serum potassium may not be low.
2. Determination of urinary potassium
Non-nephrotic potassium loss in patients with urinary potassium <20mmol / L, and renal potassium loss in patients with potassium more > 20mmol / L.
3. Blood pH determination
In patients with simple hypokalemia, the blood pH is often increased or normal, but renal tubular acidosis, severe diarrhea, diabetic ketotoxicosis and other patients with hypokalemia, blood pH is often reduced.
4. Plasma renin activity and aldosterone determination
Patients with decreased plasma renin activity and elevated aldosterone should consider primary aldosteronism; both should be considered for secondary aldosteronism; both are mostly caused by licorice extract .
Electrocardiogram has a more specific diagnostic value for hypokalemia: the earliest manifestations are ST segment depression, flat T wave, prolonged QT interval, and U wave, severe high potassium and even P wave high tip, QRS widening and room Ventricular block.
Diagnosis
Diagnosis and differential diagnosis of hypokalemia in the elderly
Diagnostic criteria
According to medical history, clinical manifestations, electrocardiogram changes and blood potassium levels, usually potassium levels of 3.0 ~ 3.5mmol / L for mild hypokalemia, 2.5 ~ 3.0mmol / L for moderate hypokalemia <2.5mmol / L for severe hypokalemia, low potassium for more than 1 week for chronic hypokalemia, understanding of urinary potassium, urinary chloride levels and blood pressure and blood acid-base metabolism contribute to the cause of the diagnosis, usually low The urinary potassium excretion in patients with potassium is >20mmol/L, which often indicates excessive loss of urinary potassium. If conditions permit, it is more meaningful to measure intracellular potassium. Clinically, erythrocyte potassium is often measured, which can reflect potassium indirectly and calculate erythrocyte potassium. (KRBC) formula is as follows:
KRBC=100×(KWB-KS)/PCV+KS
In the formula, KWB: whole blood potassium (mmol/L); KS: serum potassium (mmol/L); PCV: blood cell volume (%).
Differential diagnosis
1. Primary aldosteronism
Clinically, hypertension and hypokalemia are the main manifestations, and periodic paralysis, hand and foot spasm, aldosterone in plasma and urine are significantly increased, plasma renin and angiotensin activity are decreased. The disease is due to adrenal cortical spheroid tumor or Hyperplasia, caused by massive secretion of aldosterone, can be diagnosed according to the above characteristics and laboratory tests, but should be noted that patients with essential hypertension should be differentiated from hypokalemia due to the application of potassium-sparing diuretics or chronic diarrhea. Hypertension, renal artery stenosis patients with secondary aldosterone increased with hypokalemia.
2. Cortisol
For adrenal hyperplasia or tumor caused by excessive secretion of cortisol, patients with central obesity, hypertension, purple lines and acne, often accompanied by hypokalemia and metabolic alkalosis, elevated urinary 17-hydroxycorticosteroids, Plasma cortisol increased and diurnal secretion rhythm disappeared, and typical diagnosis is not difficult.
3.17-hydroxylase deficiency and 11-hydroxylase deficiency
Lack of 17-hydroxylase can lead to insufficient synthesis of glucocorticoids (cortisol) and sex hormones, and 11-hydroxylase deficiency only causes disorder of cortisol synthesis, both of which can cause increased compensatory secretion of ACTH, making deoxycortical Ketone (mineral corticosteroid) synthesis and secretion, leading to high blood pressure, hypokalemia, 17-hydroxylase deficiency patients also have insufficient sex hormone synthesis, so male and female secondary sexual development disorders, and 11-hydroxylation Enzyme deficiency is accompanied by excessive androgen secretion, so female patients appear masculine, male patients have precocious puberty, can be identified.
4. Renal tubular acidosis
In addition to type IV, other types of type 3 (type I, type II, type III) have marked hypokalemia, hyperchloremia and metabolic acidosis, while urine is alkaline (urinary pH is above 6). ), often accompanied by blood sodium, calcium, phosphorus, etc., urine routine examinations are often no abnormal findings.
5. Hypokalemia periodic paralysis
Family history, often in diet, alcoholism, sleep after strenuous exercise or wake up in the morning, more men than women, limbs often start from the lower limbs, bilateral symmetry, each episode lasts for hours or even days, soft, reflex disappears, but the feeling is normal, the electrocardiogram can be seen with low potassium changes, the disease should be differentiated from primary aldosteronism, the latter can also appear periodic sputum, periodic sputum is not all hypokalemia, also Patients with normal or hyperkalemia can be seen.
6. Hereditary diseases
It is characterized by hereditary diseases characterized by hypokalemia. For example, Bartter syndrome is autosomal recessive. Due to the defect of potassium transport in renal tubules, a large amount of potassium is lost. In addition to hypokalemia, aldosterone secretion is increased. Should be differentiated from primary aldosteronism; Fanconi syndrome is also autosomal recessive, is a functional defect of renal proximal convoluted tubules, a variety of substances back absorption disorders, manifested as amino acid urine, diabetes, proteinuria, potassium , sodium, calcium, phosphorus are reduced, and often accompanied by metabolic acidosis; Liddle syndrome is a hereditary disease, which is an increase in sodium absorption in the renal distal convoluted tubules, resulting in increased potassium excretion, clinical manifestations in addition to hypokalemia There are also hypertension, metabolic alkalosis, decreased plasma renin activity, and a significant decrease in aldosterone levels in blood and urine.
In addition, some rare tumors can also show hypokalemia, such as renal tumors are tumors of the glomerular cells of the renal glomeruli, a large amount of renin secretion leads to hypokalemia; islet vaso-intestinal peptides, secreting a large number of vasodilators Peptide (VIP), which can cause severe hypokalemia due to massive watery diarrhea; colon and rectal villus adenoma, which secrete a large amount of potassium in the mucus, and a large amount of mucus can cause hypokalemia.
