Neonatal hyponatremia

Introduction to neonatal hyponatremia Serum sodium below 130mmol / L is called hyponatremia, hyponatremia can be divided into: 1 sodium hyponatremia. 2 diluted hyponatremia. 3 consumptive hyponatremia. It is a clinical syndrome caused by sodium deficiency and/or water retention due to various reasons. The total amount of body fluids and body sodium can be reduced, normal or increased. Normal serum sodium is mainly regulated by the kidney under the action of vasopressin and aldosterone. Neonatal kidney regulation is poor, prone to sodium metabolism disorders. basic knowledge The proportion of illness: 0.005% Susceptible people: children Mode of infection: non-infectious Complications: hypotonic dehydration shock coma neonatal seizures

Causes of neonatal hyponatremia

(1) Causes of the disease

1. Physiological characteristics

The sodium in the human body is mainly present in the extracellular fluid, and the intracellular fluid content is very small. The daily sodium requirement of the full-term newborn is about 1-2 mmol/kg, and the premature infant is about 3-4 mmol/kg. The daily intake of water and sodium. It is not constant. The maintenance of normal serum sodium is accomplished by the combination of anti-diuretic hormone (ADH), aldosterone, diuretic hormone (atrial natriuretic peptide) and sympathetic nervous system, and appropriate reduction of sodium and water excretion. The kidney is an important organ that regulates the balance of water, electrolytes and acid-base. The younger the child, the more immature the regulatory function of the kidney.

(1) low glomerular filtration rate (GFR): neonatal glomerular filtration rate (GFR) is lower than that of adults, full-term children reach the human level at 1 to 2 years old (according to unit body surface area), premature delivery Children with lower GFR do not reach full-term infants until 40 weeks of gestation, so they cannot tolerate excessive water and electrolyte loads.

(2) Ingestion of water: Although the newborn can dilute the urine to reach the human level (30-50 mOsm/L) after 1 week of birth, the water excretion rate is slow due to low GFR, and edema and low are prone to occur when the intake of water is too high. Sodiumemia.

(3) Low renal enrichment function: Kidney concentrating function in term infants and premature infants is very low, because renal tubular epithelial cells have low response to ADH, and the concentration gradient of short medullary sac and renal medulla hypertonic zone is low, even in In the case of water loss, the urine can only be concentrated to 600-700 mOsm/L (1400 mOsm/L for adults), so the amount of water required to excrete the same amount of solute is more than that of adults, and the neonatal non-dominant water loss is relatively large. When the water intake is insufficient or the water loss is increased, it is easy to exceed the limit of the renal concentration function, and metabolite retention and hypertonic dehydration occur.

(4) poor regulation function: full-term children are positive sodium balance for growth, because plasma aldosterone is higher, distal renal tubules reabsorb more sodium; but when sodium load increases, kidney sodium is low, easy to Sodium sulphate, the adrenal cortex of premature infants has low response to plasma renin and distal renal tubules to aldosterone, and its Na+-K+-ATPase (sodium pump) has low ability to actively transport sodium, poor sodium retention capacity, and basic sodium excretion. More amount, easy to lose sodium; if the daily sodium intake is less than 2mmol / kg, hyponatremia can occur, when the sodium intake of 3mmol / kg, serum sodium can reach full-term children and adults, and premature infants The ability to divert blood from the near-medullary nephron to the sodium-deficient cortical nephron is very low, and it is also prone to sodium, hypernatremia or extracellular fluid expansion. In addition, the neonatal non-dominant water loss is relatively high. Large, hypertonic dehydration is prone to occur when the amount of water is insufficient. Due to the above physiological characteristics, the newborn does not actively adjust the ability to ingest water and salt. Therefore, neonates, especially premature infants, are more likely to have electrolyte imbalance.

2. Common causes

(1) Insufficient intake: fasting children, critically ill children, feeding difficulties in premature infants, reduced sodium intake, can cause hyponatremia.

(2) Increase in loss:

1 Gastrointestinal tract loss: diarrhea, surgical drainage, etc.

2 urinary sodium loss: diuretic, acute renal failure, polyuria.

3 mineralocorticoid deficiency: Adrenal insufficiency caused by various causes, such as congenital adrenal hyperplasia, aldosterone deficiency.

4 skin is lost.

5 pseudo aldosterone deficiency: distal renal tubules and collecting ducts do not respond to aldosterone.

(3) Water retention: excessive water intake or excretion disorders can cause dilute hyponatremia.

1 excessive water intake: oral or intravenous supplemental salt or low salt solution too much.

2 renal drainage disorders: acute renal failure.

3 congestive heart failure.

(4) Redistribution in the body: In hypokalemia, the intracellular fluid loses potassium, and the sodium in the extracellular fluid enters the cell, which lowers the blood sodium.

(two) pathogenesis

Relative or absolute sodium deficiency (excessive water) is characteristic of sodium loss and dilute hyponatremia. In the case of sodium deficiency hyponatremia, total body sodium and intracellular and extracellular volume are reduced, and effective circulating blood volume is Lower, sodium is less than water, the total amount of body sodium in normal hyponatremia can be reduced or increased, which is related to sodium intake; total body fluid and intracellular, external fluid capacity increase, effective circulation Normal or increased blood volume, but decreased in congestive heart failure, water is proportional to more than sodium, and urinary sodium excretion is related to effective circulating blood volume. When the effective circulating blood volume is reduced, except for those who lose sodium by renal pathway, Urine sodium is often <10 ~ 20mmol / L, the effective circulating blood volume caused by the loss of sodium by the renal pathway and the above-mentioned effective circulating blood volume is normal or increased, the urine sodium is often >20mmol / L.

Serum sodium is the main factor determining the osmotic pressure of extracellular fluid. In addition to pseudo-hypernatremia, elevated plasma osmotic pressure (hyperglycemia) or normal (hyperlipidemia and hyperproteinemia), hyponatremia is accompanied by hyponatremia. There is hypotonic syndrome, plasma osmotic pressure can be increased when azotemia, because urea is an ineffective osmotic solutes, effective plasma osmotic pressure [ 2 × serum sodium (mmol / L) serum glucose (mg / dl) / 18 or patients Plasma osmotic pressure-BUN/2.8] (normally 270-285 mOsm/L) is still low, hyponatremia reduces ECF osmotic pressure, ICF osmotic pressure is relatively high, and water moves from ECF to ICF, causing cells, especially brain nerve cells. Swollen, producing a series of neurological symptoms such as irritability, lethargy, lethargy, coma and convulsions. After a certain period of time (within 24 hours), brain cells adapt to hypotonic state by discharging N+, K+, Cl- and/or Combining these ions with intracellular proteins reduces the osmotic pressure of brain cells, removes water from brain cells, reduces cerebral edema, partially or completely restores the original volume, and relieves symptoms, so the severity of symptoms and the rate and extent of plasma osmotic pressure decrease directly. Related but muscle and other Tissue cells do not have this adaptation.

Neonatal hyponatremia prevention

The sodium in the human body is mainly present in the extracellular fluid. The daily sodium requirement for full-term neonates is 1 to 2 mmol/kg, and the premature infants are 3 to 4 mmol/kg or higher.

Because newborns, especially premature infants, have a low ability to regulate water, electrolytes, and acid-base balance, edema and hyponatremia are prone to occur when too much water is ingested. Therefore, premature infants should control excessive intake of water.

Prevention of hyponatremia should begin with pregnancy care:

1. Pregnant mothers with high blood pressure using a diuretic or low-salt diet can affect neonatal hyponatremia.

2. Active prevention and treatment of gastrointestinal abnormalities such as diarrhea after birth.

3. Prevention of asphyxia, ischemia, hypoxic encephalopathy, cerebral hemorrhage and other diseases.

4. Prevention and treatment of kidney diseases, so as to avoid renal drainage disorders, low response to aldosterone, renal dysfunction and so on.

5. It is necessary to prevent hyponatremia caused by excessive intake of water caused by iatrogenic or improper feeding and too low sodium intake.

The sodium in the human body is mainly present in the extracellular fluid. The daily sodium requirement for full-term neonates is 1 to 2 mmol/kg, and the premature infants are 3 to 4 mmol/kg or higher. Neonates, especially premature infants, regulate water and electrolytes. The ability to balance with acid and alkali is low, and edema and hyponatremia are prone to occur when too much water is ingested.

Prevention of hyponatremia should start from the health care during pregnancy, and the use of diuretics or low-salt diet in pregnant mothers can affect hyponatremia caused by neonates. Active gastrointestinal tract abnormalities such as diarrhea should be actively prevented after birth. Prevention of asphyxia, ischemia, hypoxic encephalopathy, cerebral hemorrhage and other diseases; prevention and treatment of kidney diseases, so as to avoid renal drainage disorders, low aldosterone response, renal dysfunction, etc.; to prevent iatrogenic or improper feeding water intake Excessive, hyponatremia caused by too little sodium intake.

Neonatal hyponatremia complications Complications hypotonic dehydration shock coma neonatal seizures

Concurrent hypotonic dehydration, blood pressure drop, shock, brain cell edema, coma or convulsions.

Symptoms of neonatal hyponatremia Common symptoms Extracellular fluid reduces dehydration limbs chills children before sputum depression water retention drowsiness antidiuretic hormone (A... irritability, blood pressure, drop shock

Symptoms can occur when serum sodium is lower than 125mmol/L. The main manifestations are hypotonic dehydration, decreased extracellular fluid, blood concentration, eye sockets, anterior sac depression, poor skin elasticity, cold limbs, decreased blood pressure, and severe shock. In severe acute hyponatremia, such as blood sodium below 115mmol / L can occur brain cell edema, irritability, lethargy, coma or convulsions, but chronic hyponatremia cerebral edema is not obvious, dilute hyponatremia When the disease occurs, the extracellular fluid increases, the blood is diluted, the osmotic pressure is lowered, the blood pressure is not lowered, and the edema is not obvious.

Antidiuretic hormone abnormal secretion syndrome (SIADH): pituitary dysfunction, antidiuretic hormone (ADH) in asphyxia, hypoxic ischemic encephalopathy, infection, meningitis, intracranial hemorrhage, cardiopulmonary dysfunction, mechanical ventilation, etc. Increased secretion, causing water retention and dilute hyponatremia, clinical manifestations similar to hyponatremia, but edema is not obvious, SIADH diagnosis based on:

1 blood sodium is lower than 130mmol / L.

2 plasma osmotic pressure decreased, <280mOsm / L.

3 The urine osmotic pressure is increased, and the urine osmotic pressure cannot be reduced to less than 100 mOsm/L during the dilution test.

Examination of neonatal hyponatremia

Serum sodium <130mmol / L, may have increased blood sugar, or hyperlipidemia or hyperproteinemia; may have elevated serum creatinine, hypokalemia, urine sodium <10 ~ 20mmol / L, can also be >20mmol / L If there is kidney damage, there may be urine protein or microscopic hematuria.

According to clinical needs, X-ray examination, B-ultrasound examination, electrocardiogram and CT examination can be done.

Diagnosis and diagnosis of neonatal hyponatremia

diagnosis

According to the clinical manifestations and serum sodium determination can be diagnosed, hyponatremia may have acid-base metabolism disorders, should be noted, in addition, should also be determined with hyponatremia with hypotension or water retention caused by dilute hyponatremia disease.

Differential diagnosis

Asphyxia, hypoxia, hypovolemia (frequent blood draw), high intrathoracic pressure (air leak, positive pressure ventilation), cardiopulmonary dysfunction, infection, intracranial hemorrhage, hypoxic ischemic encephalopathy, meningitis, pneumonia, surgery After the treatment, the baroreceptor is stimulated, causing the increase of ADH secretion, the increase of renal tubular water reabsorption and the elimination of sodium, so that hyponatremia occurs, but it needs to be distinguished from the true ADH secretion abnormal syndrome (SIADH). SIADH can only be diagnosed if hyponatremia is associated with normal blood volume, heart, kidney, adrenal gland, normal thyroid function, continued loss of urinary sodium and maximum dilution of urine, although hypoxia and craniocerebral injury can directly stimulate the hypothalamus. SIADH occurs, but it is very rare in newborns to reach this diagnostic criteria. In addition, acute renal failure, congenital nephritis or kidney disease can also occur with water retention.

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