What is Hyponatremia?
Hyponatremia is a potentially life-threatening condition in which the sodium concentration in a person's blood drops dangerously low. It is one of the most common electrolyte imbalances, especially among the elderly. There are three classes of hyponatremia: hypovolemic, hypervolemic and euvolemic. Hypovolemic hyponatremia occurs when the liquid part of our blood, called plasma, is depleted due to significant fluid losses (i.e. severe vomiting or diarrhea). Hypervolemic hyponatremia is kind of the opposite. This occurs when we become overloaded with fluid, so much so that the sodium in our blood becomes extremely diluted. Increased fluid retention may be caused by vital organ failure, such as our heart or lungs. Euvolemic hyponatremia is the result of a condition called syndrome of inappropriate antidiuretic hormone or SIADH. With SIADH, our body produces too much of the hormone that promotes fluid retention and subsequent low sodium concentration.
Classifying hyponatremia is the first step in treating it. If it's due to hypovolemia, or "low-volume," it will usually improve with an intravenous infusion of saline (a sterile mixture of salt and water). Treating hypervolemic and euvolemic hyponatremias is a little more complicated, though. The goal is to rid the body of the excess fluid. Conventional treatments have included restricting a patient's fluid intake and/or medications, such as diuretics and lithium. A new class of drugs has also shown promise for treating these conditions. Called vasopressin receptor antagonists, or "vaptans," these medications work directly on the body's vasopressin hormone system and affect blood and fluid volume.
Hyponatremia, either present upon or acquired during admission, is extremely serious in elderly patients. Research has shown a significant correlation between the condition and an increase in mortality risk, both during hospitalization and after discharge. There is also a link between hyponatremia and length of stay. Longer hospital stays mean higher healthcare costs. That's bad news for everyone, not just the patient.
Older adults with depression are actually at higher risk for developing hyponatremia. The link is due to a class of antidepressant drugs called selective serotonin reuptake inhibitors, or SSRIs. These medications work by increasing the concentration of the brain chemical serotonin. Researchers theorize that this jump in serotonin may precipitate a rise in anti-diuretic hormone and increase potential for fluid retention. Hyponatremia can develop after a few days of taking SSRIs, though in some cases, it occurs months later.
Risk of Fractures
Hyponatremia is a serious condition all by itself, but did you know that it can actually increase the risk of bone fractures in the elderly? Researchers from Belgium studied more than 500 elderly patients with bone fractures due to incidental falls. They found that hyponatremia was a factor in almost 10 percent of these cases. The imbalance of electrolytes can affect our central nervous system and lead to gait dysfunction, altered mental status and muscle weakness---all of which increase the risk of falls.