Hypernatremia is a condition, characterized by increased levels of sodium in the blood, beyond 145 mmol/L. It is serious condition requiring prompt medical attention.
Individuals with hypernatremia in the initial stages suffer from lethargy, onset of edema, excitability, weakness and irritability. As the condition progresses to more advanced stages, there is onset of seizures and the patient can even enter the comatose stage. Severe symptoms are primarily experienced due to increase in level of serum sodium above 157 mEq/L. When the levels rise beyond 180 mEq/L in adults, then it can be a significant cause of mortality .
An elevated serum sodium level of greater than 145 mEq/L confirms the diagnosis of hypernatremia. Laboratory studies are indicated in such cases, which include determining levels of urea, creatinine, glucose, serum and urine electrolytes. In addition, 24 hour urine volume along with urine and plasma osmolality also needs to be determined.
Imaging studies such as MRI and CT scan of the brain are indicated if the patient has suffered head injuries or trauma or shows signs of central diabetes insipidus. Histologic findings are of no significance unless vital signs indicate presence of central diabetes insipidus.
Treatment of hypernatremia is based on 4 goals, including recognizing the symptoms, determining the underlying disease, correcting the disturbances in volume and correction of hypertonicity .
The sodium levels are gradually brought to normal because rapid correction of volume can get very dangerous. This is so because, the brain very readily adapts to the increased sodium concentration. As a result of this, when the sodium levels are rapidly brought to normal, then water can enter the brain cells causing them to swell and giving rise to conditions like cerebral edema and seizures which can turn life threatening and cause permanent damage to brain .
Chronic cases of hypernatremia with mild or no symptoms are corrected at rate of 0.5 mEq/L/h and a total of 8-10mEq/L should be given in 24 hour period. Diurertic therapy is indicated in patients suffering from nephrogenic diabetes insipidus. Several drugs such as clofibrate, chlorpropamide and carbamazepine are given to patients with central diabetes insipidus to increase the hormone arginine vasopressin .
The prognosis of hypernatremia is good, unless an underlying neurological condition is causing the condition. The rate of mortality associated greatly depends on the severity of the condition; with a rate of 40 to 70% seen in elderly patients with severe hypernatremia .
Inadequate intake of water is the major cause of hypernatremia, which can occur due to the following factors :
It has been estimated that, in the US, the incidence of hypernatremia amongst the hospitalized population is 0.3 to 5.5%. Research has pointed towards the fact that, more than 60% cases of hypernatremia are acquired. Very low incidence of 0.12 to 1.4% of hypernatremia is recorded upon hospital admission. Critically ill patients are also at high risk of contracting the disorder due to factors such as sedation, coma or ventilation.
A high mortality rate of 30 to 48% has been recorded in patients admitted to intensive care unit. Such patients had serum sodium levels of more than 150 mmol/L .
Patients admitted to hospital due to severe sepsis, were found to develop hypernatremia within the first 5 days of hospital admission. The basic reason behind this was the 0.9% of saline that was given during the first 48 hours, which led to an increase in sodium concentration.
Hypernatremia primarily occurs due to water loss or sodium gain that essentially results from various factors. Researchers and clinicians have strongly put forth the fact that hypernatremia is a water problem and majorly occurs due to the phenomenon of decrease in total body water. In view of this, conditions favoring such a type of event cause an increase in the sodium concentration, leading to hypernatremia.
Under normal physiologic conditions, thirst and release of arginine vasopressin are triggered by increase in fluid osmolality of body beyond 280 to 290 mOsm/L. This osmotic threshold is similar for conditions of thirst as well as release of arginine vasopressin hormone. When there is an increase in the osmolality, water is drawn from the cells, which causes dehydration of the neurons in the brain, known as tonicity receptors. Upon stimulation, signals are sent to parts of brain to trigger thirst and the simultaneous release of the hormone arginine vasopressin. Such sequence of events causes increased consumption of water and increased urinary concentration, thereby correcting the hypernatremic state .
Maintenance of proper fluid balance forms the basis of preventing hypernatremia. Replenishing for lost fluids after heavy physical activity or exercise should be done. Infants and children should be fed water after short intervals. Elderly patients who are critically ill or are unable to fetch water for themselves should be taken care of and given water in between intervals .
Hypernatremia is primarily caused due to significant decrease in total body water. Due to this reason, hypernatremia often corresponds with dehydration. Such a type of condition commonly strikes the infants, individuals with altered mental status and the elderly population. The reason being, in these groups of population, the thirst mechanism is intact but they are not in a position to ask for water or help themselves .
Definition: Hypernatremia is a condition, characterized by increased serum sodium level above 145 mmol/L. The condition is a common occurrence in the infant and elderly population. It has also been noted that, majority of hospitalized patients are also susceptible to acquire hypernetremia.
Cause: It practically occurs due to reduction in total body water and does not occur due to sodium homeostasis. Factors that induce water loss include excessive sweating, diarrhea, excess of mineral corticoid due to disease such as Conn’s syndrome, salt poisoning and excess secretion of water by kidney in disease conditions such as diabetes insipidius.
Symptoms: Symptoms of hypernatremia include persistent lethargy, undue fatigue, weakness, edema and neuromuscular excitability. In severe condition, individuals can experience seizures or can even enter the comatose stage.
Diagnosis: Determining the serum sodium levels forms the preliminary base of diagnostic profile. In addition, various laboratory studies such as measuring the glucose levels, serum and urine electrolytes, urea, creatinine, 24 hour urine volume and levels of plasma hormone arginine vasopressin are also required.
Treatment: Treatment of hypernatremia is geared towards normalizing the serum sodium levels by increasing the total body water. This is done by administration of water either orally or through intravenous route. However, water alone cannot be given and therefore, it given through dextrose or saline solution.