High sodium in the blood, hypernatremia

Gastroepato

1 case. One patient, host of a nursing home, comes to our attention very dehydrated and with high sodemia. The patient is in a coma and has not been fed in the last days. We try to understand if it is a stroke or something else. From the first investigations performed hypotension and a high sodiemia.
2 case. Another clinical case. Another elderly patient, who is disabled for senile dementia, a few days is torpid fever and poorly cooperative: refuses food, drink a few sips of water, sweat constantly. Performs laboratory investigations. After a few minutes he calls us the laboratory that requires repeating the blood sample for having found a sodiumemia of 164 mmol / l and a high hematocrit of 54: loss of water free from sweat due to fever. We repeat the test but in the meantime infuse 5% glucose solution to 500 ml but the patient would need another 2.5 liters of water that, however, should be reinfused very slowly to avoid the opposite risk of excessive hydration with swelling of the brain cells (see hypernatremia 2): after a short time the laboratory confirms the result, this time of 161 mEq / l because we were already administering water and glucose for a few minutes. The veins are scarce and collapsed because the pressure is very low; the conditions are very critical and the patient, after the usual resistance of the resuscitator who wants to be sure of intubating her, always comatose for sepsis and with hyperpyrexia, goes into resuscitation after a central venous access has been found on the femoral vein, a cm of the pulsation of the femoral artery.
3 case. A 70-year-old man after a stroke, dysphagia presents and takes just gelled food and water gel. He is hospitalized. Sodiemia of 170 mmol / L. We calculate the osmolarity and the anionic gap, we give glucose solutions. The sodiemia is lowered to 161 mmol / L, but does not go further. The patient in fact also suffers from chronic renal failure, and time maintaining therapy with high-dose furosemide. As the volume has been restored, we add outosemide. We obtain normalization of diuresis and the sodiemia falls within the ranges.

Definition of hypernatremia

Sodium plasma concentration (Na +)> 145 mmol / l. Since sodium and the accompanying anions are the main effective osmolytes of extracellular fluid (extracellular fluid, ECF), it is a condition of hyperosmolality. The water moves into the extracellular space to maintain the osmotic balance, causing a contraction of the intracellular fluid volume intracellular fluid, ICF)
Epidemiology
Incidence
• 0.2% of patients admitted to general practice or surgery have or develop hypernatremia
• Age
• Infants and the elderly are the most frequently affected

Pathogenetic mechanism

General mechanisms
Hypernatremia may primarily be due to a primitive increase in Na + or a water deficit
Appropriate response to hypernatremia
Increased intake of water stimulated by thirst
Excretion of a minimal volume of highly concentrated urine reflecting arginine-vasopressin (AVP) secretion in response to an osmotic stimulus
Most cases of hypernatremia is the result of a loss of water
In children the most common cause is diarrhea
In the elderly, the causes include fever, medication and infirmity

The degree of hyperosmolality is typically mild unless access to water is limited, for example, to:

- Children
- Subjects with physical handicaps
- Patients with changes in mental status
- Post-operative patients layout-grid-mode: line ">
- Intubated patients in intensive care
- Altered mechanism of thirst

Primitive hypodipsia (lack of thirst)

Rare disease that depends on:
• It is generally the result of damage to hypothalamic osmoreceptors that control thirst
• Associated with an alteration of the osmotic regulation of AVP secretion
• It may be due to a large number of pathological changes, such as granulomatous diseases, vascular occlusions and tumors
• Essential hypernatremia
• A subtype of hypodipsic hypernatremia
• Does not respond to forced water intake
• It appears due to a deficit of specific osmoreceptors causes the non-osmotic release of AVP
• The haemodynamic effects of the water load lead to the suppression of AVP and the excretion of diluted urine

Causes of the loss of free water

The source of water loss is renal or extra-renal

Causes renal

• Drug-induced diuresis
- Loop diuretics interfere with the countercurrent mechanism
- Determines the iso-osmotic diuresis of the solutes
- Causes a decrease in the tonicity of the medullary interstitial space and an alteration of the renal concentration capacity
• Osmotic diuresis
- Organic solutes not reabsorbed into the tubular lumen alter the osmotic reabsorption of the water
- Leads to the loss of water with excess of Na + and K +
- The most frequent causes of osmotic diuresis are hyperglycemia and glycosuria in poorly controlled diabetes mellitus
- The intravenous administration of mannitol and the increase in endogenous urea production (high protein diet) may also lead to osmotic diuresis
• Insipid diabetes (DI)
- Hypernatremia secondary to non-osmotic urinary water loss
- DI central (CDI)
• Characterized by an alteration of AVP secretion: the most common cause is the destruction of the neurohypophysis
- OF nephrogenic (NDI)
• It derives from the resistance of the target organ (kidney) to the actions of the AVP
• Congenital NDI is a recessive trait linked to the X chromosome due to mutations of the gene for the V2 receptor
• Mutations in the autosomal aquaporin-2 gene may also result in NDI
• The aquaporin-2 gene encodes the water channel protein whose insertion into the membrane is stimulated by the AVP

Causes extrarenal

• Evaporation from the skin and the respiratory tract (insensitive losses)
• Losses from the gastrointestinal tract (eg, diarrhea)

Symptoms and signs

The main symptoms are neurological
As a consequence of hypertonicity, water leaks from the cells and this leads to a contraction of the intracellular fluid volume in the brain. The severity of clinical manifestations is related to the rapidity and magnitude of the increase in the plasma concentration of Na +. Chronic hypernatremia is generally less symptomatic than acute hypnathremia

Symptoms

They are characterized by alteration of the mental state with weakness, neuromuscular irritability, focal neurological deficit, occasionally coma or epileptic seizures. The patient, if conscious, presents polyuria or thirst. Patients with polydipsia from CDI (central diabetes insipidus) prefer ice water. Patients with history of excessive sweating, diarrhea or osmotic diuresis present with signs and symptoms of volume depletion and have orthostatic hypotension.

Differential diagnosis

Insensitive losses of free water
Increased in case of fever, with exercise, heat exposure, severe burns, mechanically ventilated patients. The concentration of Na + of the sweat decreases with the profuse sweating which increases the loss of water without solutes

Gastrointestinal loss of free water

Diarrhea is the most common cause of water loss. Osmotic diarrhea (induced by lactulose, sorbitol or carbohydrate malabsorption) and viral gastroenteritis result in a loss of water that exceeds that of Na + and K + (secretory diarrhea (eg, cholera, carcinoid, VIPoma). twice the sum of the concentrations of Na + and K +) is similar to the plasma, with a contraction of extracellular fluid volume and a plasma concentration of normal Na + or hyponatraemia.

Diuresis induced by drugs
Loop diuretics

Osmotic diuresis

It means that the water is expelled with the urine because it follows a solute. A very frequent cause of osmotic diuresis is the condition of hyperglycemia with glycosuria in poorly controlled diabetes mellitus.

Other causes

• Intravenous administration of mannitol
• Increased endogenous urea production (high protein diet)

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Link on topic: Il sistema urinario Il paziente con azotemia alta Il paziente che urina poco Il sedimento urinario, la cilindruria Il paziente senza sodio Il paziente con potassiemia elevata Il paziente con potassiemia bassa La perdita di albumina nelle urine,