Hyponatremia – Symptoms , Causes, Treatment And Prevention

Can you imagine your food without salt? Just a pinch of salt is all that is required to make it tasty. Salt is not only for taste but an essential electrolyte which helps the body to function properly. But an excess of it could cause serious health issues.

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Hyponatremia is less salt or sodium in the blood and is more common with people who are in and out of hospitals. Also, it depends on how much water you drink to balance your sodium levels in the body. It could also be a symptom of an underlying major ailment.

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Excess water without sufficient sodium in the blood or below 135 mEq/L is hyponatremia. So to know how much salt you can add to your dinner and the right amount of water to drink with it, continue reading.

Lack of sodium in the body could cause the swelling of the cells and fluid retention. This leads to symptoms of nausea, headaches, fatigue, weakness, and confusions. In severe cases, hyponatremia can cause neurological disorders and fluid retention in the brain causing brain damage and coma.

SODIUM:

Sodium the major cause of hyponatremia is a chemical element. The single electron in the outer shell of sodium readily donates it to create positively charged sodium cation.

ECF:

This cation in the ECF or extracellular fluid is the main source for the osmotic pressure. Sodium cation is the major part of the ECF compartment volume. When these pressure and volume or increased or decreased it is called Natremia.

Sodium is the culprit for heart diseases. This is because of its increase it affects the blood pressure and causes fluid retention or swelling. But in optimum levels, it is an essential electrolyte for the body.

The cations of sodium carry an electric charge when dissolved in fluids like blood. Daily optimum consumption of sodium as per various research is 1500 mg only.

The main functions of Sodium:

• Helps to regulate the water around the cells
• Controls blood volume
• Regulates blood pressure
• Allows the muscles and nerves to work properly

Hypotonicity:

Sodium serum concentration below 135 mEq/L is called hyponatremia. Most of the hyponatremia patients have hypotonicity. It is the measure of the osmotic pressure vector-valued function. Diabetic patients who have accumulated exogenous effective osmoles and patients with pseudohyponatremia do not have hypotonicity with hyponatremia.

TYPES OF HYPONATREMIA:

Plasma or serum sodium concentration and serum osmolarity are normally maintained by precise control of homeostatic mechanisms like stimulation of thirst. Secretion of ADH or anti-diuretic hormone and the renal handling of filtered sodium also control the homeostatic mechanisms.

Types of hyponatremia depending on the TBS, TBW & ECF:

Hypovolemic hyponatremia:

TBW or total body water decreases along with the TBS or total body sodium to a greater extent. The ECF or the extracellular fluid volume is also decreased in this case.

Hypervolemic hyponatremia:

TBS and TBW increase with a marginal increase of ECF volume with the presence of edema or abnormal accumulation of liquid in tissues.

Euvolemic hyponatremia:

TBW increases but the TBS remains normal. The ECF volume is only marginally increased but without the presence of edema.

Redistributive hyponatremia:

In this case, the sodium is diluted because of the water shifts from the intracellular to the extracellular compartment. The TBW and TBS are unchanged. This is common with diabetics or for those administered with Mannitol.

Chronic hyponatremia:

When the sodium levels drop gradually for a period of time with fewer symptoms and complications are called chronic hyponatremia.

Acute hyponatremia:

This is the most dangerous condition of hyponatremia wherein the sodium levels drop drastically and rapidly. This, when not given emergent medical attention, could cause in fast brain swelling which results in coma or death.

Hyponatremic encephalopathy:

In case of very low sodium levels in the blood causes the swelling of the brain cells. This swelling results in increased pressure in the skull and causes hyponatremic encephalopathy.

Herniation of the brain will be caused due to the continuous pressure in the skull because it squeezes the brain across the internal structures of the skull. This causes brain stem compression, seizures, respiratory arrest, non-cardiogenic accumulation of fluid in the lungs.

Hyponatremic encephalopathy is usually fatal if not treated immediately on the symptoms.

Hyponatremia as per the sodium level in the blood:

The sodium in the blood is measured by the milliequivalents or millimoles of sodium reacting with one liter of water. The following are the sodium levels in the blood and their classifications.

Normal sodium levels are 135 – 145 mEq/L

Serum sodium levels of 130 – 135 mEq/L is called mild hyponatremia

Moderate hyponatremia is between 125 = 129 mmol/L or millimoles per liter

Severe hyponatremia is anything below 125 mmol/L

Different hyponatremia as per the volume of the body fluid status and tonicity:

Low tonicity hyponatremia:

When the sodium ions in the blood are less than the prescribed level is called low tonicity hyponatremia. As per the volume of the fluids in the low tonicity hyponatremia are classified as follows:

Low volume hyponatremia:

This kind of hyponatremia is due to diarrhea, diuretics, sweating, and vomiting.

High volume hyponatremia:

Both sodium and the water increases in this case. The sodium increase leads to hypervolemia and the increase in water content leads to hyponatremia.

Normal Volume hyponatremia:

This is divided into two classes:

Dilute urine:

Due to the reasons of hypothyroidism, adrenal insufficiency or drinking of too much water or beer, the urine is diluted causing normal volume hyponatremia.

Concentrated urine:

This is caused by SIADH or syndrome of inappropriate antidiuretic hormone or ADH secretion.

False and True hyponatremia:

False hyponatremia or pseudo hyponatremia:

The ECF is diluted by excess proteins and lipids. The TBW and the TBS are unchanged. This is common with hypertriglyceridemia or high cholesterol patients and those with multiple myeloma or cancer cells.

This is also known as hypertonic or artificial hyponatremia. The lab tests show low sodium levels but there is no hypotonicity. This is because or resorption of water by molecules such as glucose in diabetic patients or mannitol. In isotonic hyponatremia, the sodium measurement error is due to the high blood triglyceride levels. Paraproteinemia occurs when an excess of protein or lipids are present.

True hyponatremia:

The most common type of hyponatremia is the hypotonic hyponatremia. This is the commonly called hyponatremia.

SYMPTOMS OF HYPONATREMIA:

Symptoms of hyponatremia depend on the underlying ailment and the severity of it and due to other causes. Symptoms can also vary from person to person depending on their body conditions.

Common symptoms of hyponatremia:

• Muscle weakness and pains with spasms or cramps
• Digestive issues like vomiting, diarrhea, and nausea
• Dizziness with imbalance and instability
• Having trouble to concentrate and being confused
• Even after a good night’s sleep feeling lethargy, fatigue and having low energy
• Increased irritability and having frequent mood changes with restlessness
• Short-term memory loss
• Symptoms due to severe hyponatremia:
• Increased falls due to interference in bone metabolism
• Altered posture and gait
• Reduced attention
• Brain swelling and coma

COMPLICATIONS OF HYPONATREMIA:

Complications of hyponatremia are more common with pregnant women and elderly people. The main reason for this is the effect of women’s sex hormones on the body’s ability to balance sodium levels.

A retrospective study on the elderly hyponatremia patients by Brouns found that the hyponatremia is the risk factor for hospital admission. This resulted in longer hospital stay and 3 months mortality. Complications related to hyponatremia therapy included osmotic demyelination syndrome and fluid overload.

Other major complications of hyponatremia include:

• Rhabdomyolysis
• Seizures
• Permanent neurologic sequelae relating to the ongoing seizures or cerebral edema
• Respiratory arrest
• Death

CAUSES OF HYPONATREMIA:

Hyponatremia is caused because of low sodium in the blood. There are several causes to the low level of sodium including the underlying ailment.

Some factors which increase the risk of low blood sodium

• Old age
• Living in a high temperature or warmer climate
• Primary polydipsia which is a condition that makes you drink water too much because of excessive thirst.
• Cushing’s syndrome which causes high cortisone levels
• Amphetamine known as Ecstasy when consumed is linked to serious cases of hyponatremia

Dehydration:

Diarrhea, chronic or severe vomiting and other causes of dehydration results in loss of electrolytes like sodium and also increases the antidiuretic hormone levels causing hyponatremia.

Restrictive diets:

The increase of diets and excess consumption of water with it and eating more of hydrating foods like fruits and vegetables which are low in sodium.

Very hard physical activities:

People taking part in marathons, ultramarathons, triathlons, long-distance races, high-intensity activities are prone to hyponatremia.

Excess drinking of water:

Drinking excess of water for various reasons results cause low sodium by increasing the kidney’s ability to excrete water. Sodium is lost by sweat during endurance activities.

Hormonal imbalances:

Hormonal imbalances occur by the following ailments:

Addisons’s disease:

Adrenal gland insufficiency is called Addison’s disease which affects the adrenal gland’s ability to produce hormones. These hormones help maintain the body’s balance of sodium.

Thyroid disorder:

If your thyroid level is too low then the sodium level will also be of the lower level and cause hyponatremia.

SIADH:

Syndrome of inappropriate anti-diuretic hormone or SIADH can retain water in our body. This alters the sodium levels and causes hyponatremia.

Causes of hyponatremia by volume of fluid:

The low tonicity of sodium ions are categorized as per the volume of the fluid volume and the causes of each category include:

The high volume of fluid:

The high water content causes hyponatremia and the sodium content causes hypervolemia. The following are the major causes:

• Congestive heart failure
• Liver cirrhosis
• Kidney failure due to nephrotic syndrome
• Excessive drinking of fluids
• Normal volume:
• SIADH
• Hypothyroidism
• Lack of ACTH which is an important part of the hypothalamic-pituitary-adrenal axis which is produced in response to biological stress.
• Pregnancy time physiologic changes
• Beer potomania or excessive drinking of beer which is poor in electrolytes and solutes

Low Volume:

• Hypovolemia which causes vomiting and severe diarrhea
• ADH release due to diuretic use
• Addisons disease
• Congenital adrenal hyperplasia
• Pancreatitis
• EAH or exercise-associated hyponatremia
• MDMA or the use of ecstasy

Renal insufficiency:

Acute or chronic renal insufficiency may cause the inability of the patients to excrete adequate amounts of free water. This accumulates to form hyponatremia.

Elders in the hot climate:

Two studies conducted by Giordano and Huwyler that hyponatremia in elders increases during the summer months and the rate of it compared to winter months is nearly up to 2 % increase in the summer months.

Certain medications:

• water pills or diuretics
• Antidepressants
• Painkillers

Taking some medications like the above alters the hormonal and kidney process which are responsible for keeping the sodium concentrations within the healthy norm range.

PATHOPHYSIOLOGY OF HYPONATREMIA:

The pathophysiology involves the functional changes of the sodium serum in the narrow range of the fluid compartments and their sub-compartments. With the increased fluid intake, the hypothalamic-renal feedback is overwhelmed. This causes the ADH or anti-diuretic hormone to be always turned on causes the receptors in the kidney to be open even without any signal from the ADH to open. ADH is increased though there is no normal stimulus.

DIAGNOSIS OF HYPONATREMIA:

Hyponatremia can be caused by various reasons and will be different from person to person. Hence the doctor will ask about your medical history. Also the symptoms and the from when you are experiencing those symptoms. A physical examination will be done.

Physical examination:

Physical findings will help to ascertain the severity of hyponatremia and to what category it fits.

Neurological physical examination:

• Focal or generalized seizure activity
• Level of alertness ranging from being alert to the stage of coma
• Signs of brainstem herniation or problems and pain in the spinal cord discs.
• Unilateral and dilated pupil
• Abnormal or decerebrate posturing
• Sudden severe hypertension and respiratory arrest
• Variable degrees of cognitive impairment like:
• Short-term memory loss
• Confusion and depression
• Orientation to person, place or time

Physical examination for hydrate status:

Some patients with signs of hyponatremia could show signs of hypovolemia or hypervolemia. This could be checked by the hydrated status of physical examination.

• Diminished skin turgor pressure or hydrostatic pressure
• Dry mucous membranes
• Tachycardia is a condition when the heart beats faster without giving time to pump blood.
• Orthostasis is a condition when the blood pressure drops drastically when someone gets up from sitting or lying down position.

All these four conditions confirm the presence of hypovolemic hyponatremia because of excessive loss of body fluids with the replacement of inappropriately dilute fluids.

The physical examination results which confirm hypervolemic hyponatremia due to excess retention of sodium and free water include:

• Pulmonary rales or abnormal lung sounds
• S3 gallop or a third heart sound which is normal in young age but critical when older
• An elevated JVP or the jugular venous distension is the best sign of venous hypertension or right-sided heart failure. JVP is visualized in the neck that is higher than normal.
• Peripheral edema or excess water swelling
• Ascites or abnormal accumulation of fluid in the abdomen

Patients who are not diagnosed or both hypovolemia and hypervolemia are considered to have euvolemic hyponatremia which is characterized by the following etiologies:

• Hypothyroidism
• Cortisol deficiency
• SIADH
• Exogenous free water load

Muscle-related signs like weakness, cramping pain or tenderness could be of a rare case of Rhabdomyolysis.

Blood & Urine Tests:

Then the doctor will prescribe blood check the sodium level in the blood and urine.

Even if there is no low sodium level in the blood the doctor may ask you to take a metabolic panel test. This will give details of all the electrolytes in the body including sodium. If there is an abnormal sodium level, the doctor will ask you to have your urine tested. The result will help the doctor to determine the cause of your low blood sodium.

• If the blood sodium is low and urine sodium is high it means that your body is losing too much sodium.
• If your body and urine sodium is low it shows that your intake of sodium is less and you have too much water in your body.

Differential diagnoses of hyponatremia:

All the underlying ailments like heart failure and other should be diagnosed according to their symptoms and physical examination.

Recently a serum peptide known as copeptin is used in the evaluation of hyponatremia. A recent study on 106 patients found that copeptin is the C terminal portion of provasopressin and is released in equimolar amounts with vasopressin or ADH. The study confirms that copeptin could be a useful marker in the differential diagnosis of hyponatremia.

Imaging studies:

Imaging studies may be required depending on the underlying etiology of the hyponatremia. These include:

Chest x-ray for patients with congestive heart failure

CT scan of the head for patients with altered mental status to eliminate any other underlying cause present.

TREATMENT OF HYPONATREMIA:

Treatment of hyponatremia should be based on the underlying cause. Correcting hyponatremia too quick or too slow is dangerous. 3 5 normal saline is the only rapid partial correction recommended for those with serious symptoms. Some prehospital care depending on the underlying ailment could be given with care.

The common treatment for hyponatremia:

• Adjusting the dosage of diuretics
• Cutting fluid intake for patients with SIADH and high volume hyponatremia with a low salt diet
• Taking medications for headaches, nausea, seizures and other symptoms
• Treating underlying ailments
• Infusing an IV or intravenous sodium solution

Fluids for different stages of hyponatremia:

Mild & asymptomatic hyponatremia:

It is treated with an adequate solution of salt and protein with fluid restriction starting at 500 ml per day of water with adjustments depending on their serum sodium levels. 1200 – 1800ml per day long-term fluid restriction will maintain the person in a symptom-free condition.

Moderate & symptomatic hyponatremia:

This could be treated by raising the serum sodium level by 0.5 to 1 mmol/L for every hour to a total of 8 mmol per liter during the first day. Furosemide could be used and 0.9 % saline could replace sodium and potassium losses.

Severe symptomatic hyponatremia:

3 % or 1-2nk/kg IV in 3-4 hours hypertonic saline may dilute dieresis and fall in the serum sodium. Caution should be taken when used in those with an expanded extracellular fluid volume.

Medications to hyponatremia:

Scientific experts differ on the mediations to hyponatremia. There is evidence of medicines more effective than the fluid restriction in high volume hyponatremia. They are Vaptans like Conivaptan which is a vasopressin receptor antagonists.

PREVENTION OF HYPONATREMIA:

After sodium, water places the important part in hyponatremia. But on many studies across the world, on a typical day, women should drink 2.2 liters of fluids and men should drink 3 liters.

The perfect sign of being adequately hydrated is your urine will be pale yellow or clear and you won’t feel thirsty often. Never drink more than 1 liter of water in an hour. Monitor your intake of water during exercises or hard physical activities. It is also important to increase the fluid intake in the following conditions:

• Warm weather
• In high altitude
• When pregnant or breastfeeding
• Vomiting, diarrhea or having a fever

The treatments to hyponatremia are very less and the underlying conditions could make it worse. Hence a proper lifestyle with a balanced diet and with awareness of the signs and symptoms will help you in a long way. Proper water intake and maintaining sodium levels appropriately at all times will keep you away from hyponatremia.

 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4192979/