Hyponatremia hypertonic

Hyponatremia is very common in hospitalized patients and is defined as a serum sodium concentration below 136 mEq/L (136 mmol/L). Clinical signs and symptoms appear at concentrations below 120 mEq/L (120 mmol/L) and typically consist of agitation, fatigue, headache, muscle cramps, and nausea. With profound hyponatremia (less than 110 mEq/L [110 mmol/L]), confusion, seizures, and coma maybe seen. Because therapy is also influenced by volume status, hyponatremia is further defined as (1) hypertonic hyponatremia (2) hypotonic hyponatremia with an increased ECF volume (3) hypotonic hyponatremia with a normal ECF volume and (4) hypotonic hyponatremia with a decreased ECF volume.16... 

Hypertonic hyponatremia is usually associated with significant hyperglycemia. Glucose is an osmotically active agent that leads to an increase in TBW with little change in total body sodium. For every 60 mg/dL (3.33 mmol/L) increase in serum glucose above 200 mg/dL (11.1 mmol/L), the sodium is expected to decrease by approximately 1 mEq/L (1 mmol/L). Appropriate treatment of the hyperglycemia will return the serum sodium to normal.15... 

Hypertonic saline is obviously hypertonic and provides a significant sodium load to the intravascular space. This solution is utilized very infrequently given the potential to cause significant shifts in the water balance between the ECF and the ICF. It is typically considered to treat patients with severe hyponatremia who have symptoms attributable to low serum sodium. 

Treatment of hyponatremia involves the use of hypertonic saline. However, care is required since correction at rates in excess of 1 mEq/l/h may result in central pontine myelinolysis (CPM) [5], Symptoms of CPM include progressive weakness leading to quadriparesis, pseudobulbar palsy and altered mental status. CPM is often fatal and is characterized neuropathologically by demyelinating lesions in the central pons. 

Depending on serum osmolality, hyponatremia is classified as isotonic, hypertonic, or hypotonic (Fig. 78-1). 

Enemas may contain water, salts, soap, mineral detergent (docusate potassium), or hypertonic (sorbitol, sodium phosphate-biphosphate) fluids. These are convenient and generally safe for short-term use. Many of these solutions irritate the mucosa and may produce excessive mucus in the stool. Excessive use of these enema products may result in water intoxication and hyponatremia. 

In mild cases of hyponatremia, treatment typically focuses on water restriction (< 800 mL/day) however this approach suffers from poor patient compliance due to thirst brought on by increasing serum osmolality.1,10 In cases of extreme hyponatremia, infusions of hypertonic saline are used to elevate serum sodium concentrations. Loop diuretics (e.g., furosemide) are often used as an adjunct to such treatment to offset potential volume overload.1 Hypertonic saline therapy is also suboptimal, as it carries a risk of overly rapid adjustment of plasma sodium levels, which can result in the rapid shift of water from brain tissue to the vascular space, triggering neural demyelination that can result in seizures, coma, quadriplegia, and even death.1... 

Adding an isotonic solution to the extracellular fluid (ECF) does not change intracellular volume. Adding a hypertonic solution to the ECF decreases cell volume, whereas adding a hypotonic solution increases it (Table 78-1). Hypernatremia and hyponatremia can be associated with conditions of high, low, or normal ECF sodium and volume. Both conditions are most commonly the result of abnormalities of water metabolism. 

Accurate control of the serum sodium is a major difficulty in the setting of severe hyponatremia. The administration of an amount of hypertonic saline calculated to raise the sodium to mildly hyponatremic concentrations can result in serum sodium in the normonatremic or even hypematremic range. The serum sodium should not be allowed to raise more that 12 mmol/1 over the first 24 hours, and even less over each subsequent 24-hour period. It is clear that an amount of saline calculated to raise the serum sodium by a given amount affects individuals differently. This makes frequent monitoring of serum sodium mandatory. 

Depletional hyponatremia (excess loss of Na ) is almost always accompanied by a loss of ECF water, but to a lesser extent tlian the Na loss. Hypovolemia is apparent in the physical examination (orthostatic hypotension, tachycardia, decreased skin turgor). Loss of isosmotic or hypertonic fluid is the cause and this can occur through renal or extrarenal losses. If urine Na is low (generally <10 mmol/L), the loss is extrarenal (see Figure 46-2) because the kidneys are properly retaining filtered Na in response to increased aldosterone (stimulated by the hypovolemia and hyponatremia). Causes of extrarenal loss of Na" in excess of H2O include losses from the gastrointestinal tract or skin (see Figure 46-2). 

Diuretics are used widely for the treatment of hypertension see Chapter 32), and loop diuretics appear to lower blood pressure as effectively as Na+-CL symporter inhibitors e.g., thiazides and thiazide-hke diuretics) while causing smaller perturbations in the Upid profile. However, the short elimination half-lives of loop diuretics render them less useful for hypertension than thiazide-type diuretics. The edema of nephrotic syndrome often is refractory to other classes of diuretics, and loop diuretics often are the only drugs capable of reducing the massive edema associated with this disease. Loop diuretics also are employed in the treatment of edema and ascites of hepatic cirrhosis however, care must be taken not to induce encephalopathy or hepatorenal syndrome. In patients with a drug overdose, loop diuretics can be used to induce a forced diuresis to facilitate more rapid renal elimination of the offending drug. Loop diuretics, combined with isotonic saline administration to prevent volume depletion, are used to treat hypercalcemia. Loop diuretics interfere with the kidney s capacity to produce a concentrated urine. Consequently, loop diuretics combined with hypertonic saline are useful for the treatment of hfe-threatening hyponatremia. Loop diuretics also are used to treat edema associated with chronic renal insufficiency. Most patients with ARE receive... 

Treatment of hyponatremia. Treatment depends on the cause, the patient s volume status, and most important, the patient s clinical condition. Caution Avoid overly rapid correction of the sodium, because brain damage (central pontine myelinolysis) may occur if the sodium is increased by more than 25 mEq/L in the first 24 hours. Obtain frequent measurements of serum and urine sodium levels and adjust the rate of infusion as needed to inorease the serum sodium by no more than 1-1.5 mEq/h. Arrange consultation with a nephrologist as soon as possible. For patients with profound hyponatremia (serum sodium < 110 mEq/L) accompanied by coma or seizures, administer hypertonic (3% sodium chloride) saline, 100-200 mL. 

Care must be taken in the use of hypertonic saline infusions to avoid rapid shifts in sodium level. The nurse should be aware of the length of time hyponatremia has been present and the severity of symptoms. If symptoms are severe and hyponatremia is acute over less than 48 hours, sodium supplement may be infused rapidly to avoid complications of the low sodium levels. Frequent sodium level determinations should reveal an increase of up to 2 mEq/L over 3-4 hours to a maximum of 15 mEq/day. If the sodium level has been low for more than 48 hours. 4... 

Others have proposed that the symptoms result from cellular water intoxication, itself a result of hyponatremia. The salutary but transient effect of mannitol administration is invoked in support of that concept. Hypertonic mannitol withdraws water from the intracellular space into the extracellular space, thereby at least temporarily restoring the sodium balance in the... 

Fluid balance In two patients undergoing transurethral resection, the bladder was irrigated with large volumes of mannitol 5%, which was absorbed and caused pulmonary edema and severe hyponatremia (serum sodium 99 and 97 mmol/1) [63 ]. Hypertonic saline increased the serum sodium concentration and plasma volume expansion corrected hypotension one patient also required positive-pressure ventilation and intravenous noradrenaline. Both recovered completely. 

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