Hyponatremia in the elderly

Introduction to hyponatremia in the elderly The normal value of blood sodium is 142mmol/L (135145mmol/L), and the sodium level below 135mmol/L is hyponatremia. Hyponatremia is a common electrolyte disorder in clinic. Sodium and water are closely related. Interdependent. The blood sodium concentration is lowered, and the osmotic pressure of plasma is also generally lowered, so hyponatremia is also called hyponatremia hypotonic syndrome. The plasma sodium concentration that should be clearly determined does not indicate the total amount of sodium in the body and the distribution of sodium in the body. The measured decrease in plasma sodium concentration is not sufficient to confirm sodium deficiency in the body. For example, in the case of dilute hyponatremia, the total amount of sodium in the body does not decrease, and sometimes even increases. However, since the increase of water in the whole liquid is more obvious than the increase of sodium than the increase of sodium, the plasma sodium concentration is lowered. . basic knowledge The proportion of illness: 0.005% Susceptible people: the elderly Mode of infection: non-infectious Complications: edema, epilepsy, coma

Causes of hyponatremia in the elderly

(1) Causes of the disease

Hyponatremia combined with extracellular fluid reduction, the cause is the same as dehydration; and the extracellular fluid is normal or increased, the cause is heart failure, cirrhosis, nephrotic syndrome, acute tubular nephritis, etc. In addition, vasopressin Syndrome of inappropriate ADH (SIADH), hypothyroidism, etc. may be a common cause of hyponatremia in the elderly that is easily overlooked.

(two) pathogenesis

The important mechanism is that the blood volume is too low, the secretion of ADH is too much or the effect is too strong, the aldosterone secretion is insufficient, the renal drainage function is seriously degraded, and the primary drinking water is excessive.

Prevention of hyponatremia in the elderly

Mainly the treatment of primary disease, improve heart, liver and kidney function, increase effective circulation, limit sodium intake, and proper use of diuretics is the key to prevent hyponatremia.

Elderly hyponatremia complications Complications, edema, epilepsy, coma

Can be complicated by cerebral edema, seizures, convulsions, coma and so on.

Symptoms of hyponatremia in the elderly Common symptoms: fatigue, nausea, hyponatremia, edema, lethargy, coma, renal failure, hematuria, urinary oliguria

Depending on the underlying disease and the degree and rate of hyponatremia, the sharp hyponatremia often shows significant neurological symptoms, more common in older women, mild hyponatremia (blood sodium > 125mmol / L) For fear of eating, nausea and other gastrointestinal symptoms; moderate hyponatremia (blood sodium <125mmol / L) manifested as headache, fatigue, lethargy and muscle spasm; severe hyponatremia (blood sodium <115mmol / L), then There are convulsions and coma, especially in the elderly with central nervous system lesions, and even localized neurological localization symptoms, while chronic mild hyponatremia often lacks symptoms, with volume loss, corresponding signs, due to water and sodium retention Common edema is caused, and SIADH edema is rare.

Examination of hyponatremia in the elderly

(1) Causes of the disease

Hyponatremia combined with extracellular fluid reduction, the cause is the same as dehydration; and the extracellular fluid is normal or increased, the cause is heart failure, cirrhosis, nephrotic syndrome, acute tubular nephritis, etc. In addition, vasopressin Syndrome of inappropriate ADH (SIADH), hypothyroidism, etc. may be a common cause of hyponatremia in the elderly that is easily overlooked.

(two) pathogenesis

The important mechanism is that the blood volume is too low, the secretion of ADH is too much or the effect is too strong, the aldosterone secretion is insufficient, the renal drainage function is seriously degraded, and the primary drinking water is excessive.

Diagnosis and diagnosis of hyponatremia in the elderly

Diagnostic criteria

Diagnosis of hyponatremia is not difficult, it is difficult to diagnose the cause of hyponatremia, usually blood sodium <120mmol / L has a substantial significance.

Etiology diagnostic program

Firstly, the plasma osmotic pressure is measured, and the plasma osmotic pressure is normal or increased, considering hypoglycemia (such as severe hyperlipidemia) or hyperglycemia due to diabetes (usually, blood glucose is higher than normal 5.56mmol / L can dilute blood sodium 1.6mmol / L); plasma osmotic pressure should be further judged according to extracellular fluid volume and effective blood volume, the extracellular fluid volume and effective blood volume are low, the serum BUN and Cr levels often increase, if Urine sodium <10mmol / L is extrarenal loss, if the urine sodium > 20mmol / L is lost by the kidney, or the use of diuretics, or salt-losing nephropathy, or aldosterone deficiency, according to the history is not difficult to identify, necessary to retest Urine potassium is more helpful to judge, as for the extracellular fluid volume is not low, if there is edema or third interstitial effusion, often heart, liver, kidney disease, or hypothyroidism, caused by Addison disease, at this time its urine sodium Level often <10mmol / L; if the urine sodium level is often > 20mmol / L, serum BUN and Cr levels are often increased, and severe oliguria, it is prompted by renal failure, if there is no edema, no extracellular fluid or effective blood volume For reducers, SIADH is often suggested, and the water load test is helpful for identification.

2. SIADH clinical diagnosis basis

1 urine can not reach the maximum dilution when the blood osmotic pressure is too low (even after water load), in most cases, the urine osmotic pressure is lower than the blood osmotic pressure;

2 blood BUN, Cr level is normal or low, GFR is normal;

3 After the liquid load (including the injection of physiological saline), the water is still stored in the body, the sodium is still discharged from the urine, and the hyponatremia is intensified;

4 limit water intake, can improve hyponatremia;

5 patients often edema, blood uric acid levels are low, blood potassium, HCO3-normal;

6 If blood uric acid is increased, blood potassium is abnormal or blood HCO3- is abnormal, it is often caused by other causes.

Differential diagnosis

Gastrointestinal disease

Vomiting, diarrhea drainage, loss of a large amount of digestive juice, is a common cause of clinical hyponatremia, should pay attention to identify gastrointestinal diseases with hyponatremia.

2. Acute and chronic renal disorders

Whether acute or chronic renal failure can cause renal concentrating and dilution dysfunction, water, sodium metabolism disorders, according to the history, urine sodium and urine routine examination, renal function test should be identified.

3. Renal tubular acidosis

This disease is caused by hypothalemia caused by renal tubular hydrogen secretion and back absorption of bicarbonate, which can be caused by hyperchloremia acidosis, alkaline urine, blood urea nitrogen and creatinine, serum potassium and sodium. Calcium, phosphorus reduction and alkaline phosphatase increase are diagnosed, and if necessary, ammonium chloride test is performed to determine the type.

4. Idiopathic hyponatremia

Often associated with a variety of chronic diseases of tuberculosis, cancer, malnutrition, old body decline, blood sodium reduction is mild, kidney concentration and dilution function is normal, but limiting water intake can not correct hyponatremia.

In addition, it should be distinguished from mental polydipsia, diabetic ketosis, hypothyroidism, Addison disease and antidiuretic hormone secretion syndrome, which can also cause hyponatremia.

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