Less than 135mEq/L is considered low in a normal adult patient. The normal range is generally 135-145 mEq/L.
Cerebral edema and increased intracranial pressure in brain tissue stimulate receptors in the brain causing nausea and vomiting.
Early signs of hyponatremia include decreased level of consciousness with severity of symptoms increasing as hyponatremia progresses.
Confusion and lethargy are often associated with decreased level of consciousness attributed to decreased excitability of CNS tissues due to decreased sodium levels. Always assess the patient’s history to establish a baseline normal level of functioning. Check for a medical alert bracelet on the patient for the possibility of diabetes.
Both hyponatremia and hypernatremia may result in seizures and eventually coma as neuromuscular synapses are unable to fire appropriately. A severe manifestation results in coma.
Decreased muscle strength often manifests as decreased or absent deep tendon reflexes. Any patient with muscle weakness should have their airway status monitored. Patients with decreased LOC also are at risk for aspiration.
Loop and thiazide diuretics can precipitate hyponatremia as well as low levels of other body electrolytes. A health care provider may reduce their dosages.
Patients with fluid excess, especially exhibiting signs of increased intracranial pressure are given Mannitol (Osmitrol), an osmotic diuretic which causes excretion of only free water. This medication decreases fluid volume and results in increased osmolarity of the plasma.
Patients presenting in a non-acute (<48 hours), asymptomatic presentation with findings of hypervolemic hyponatremia may be placed on a fluid restriction and need their underlying condition addressed. Patients with psychogenic polydipsia are often given this treatment.
Acutely hyponatremic patients with serum sodium <130 mEq/L who are asymptomatic, are usually treated with a 50 mL bolus of 3 percent saline (ie, hypertonic saline) to prevent the serum sodium from falling further. However, do not give hypertonic saline if the hyponatremia is already autocorrecting due to a water diuresis. Autocorrection can be suspected if the cause of hyponatremia has been reversed, urine output has increased, and the urine is dilute.
Patients with fluid deficit hyponatremia will often be given a small volume hypertonic solution such as 3% IV saline. These solutions increase the osmolarity of the plasma and shift fluid from the ICF to the ECF.
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