The reason why you should not give normal saline in SIADH is because it can worsen hyponatremia which is low sodium levels by causing water retention and diluting of the blood as the persons kidneys are already retaining water as a result of excessive ADH.
In SIADH, your body retains water as a result of the inappropriate release of antidiuretic hormone ADH which leads to hyponatremia.
Giving normal saline in SIADH will lower the serum sodium even more.
The most serious complication of SIADH is hyponatremia which causes your body to retain too much water and leads to a dilution of sodium in your blood.
Other serious complications that can occur from SIADH are brain swelling and brain damage that can lead to seizures, confusions, hallucinations, coma and even death if your sodium levels drop too rapidly.
And other complications such as respiratory failure and brain herniation can occur with SIADH although they are less common.
The 4 patterns of SIADH are types A, B, C and D and each are characterized by a distinct pattern of arginine vasopressin secretion across a range of plasma osmolalities.
Type A SIADH is characterized by secretion of AVP that is unregulated, independent of plasma osmolality, leading to severe hyponatremia.
Type B SIADH involves elevated basal secretion of AVP despite normal regulation by osmolality, with AVP secretion occurring at lower plasma osmolalities than normal.
Type C SIADH is failure to suppress AVP at plasma osmolalities below the osmotic threshold, resulting in inappropriately high AVP levels even at low plasma osmolalities.
Type D SIADH is when you have low or undetectable AVP levels and potentially due to a gain of function mutation of the V2 receptor, which may be more appropriately termed syndrome of inappropriate antidiuresis.
SIADH is also known as syndrome of inappropriate antidiuretic hormone secretion.
SIADH is a condition in which your body produces too much antidiuretic hormone also known as ADH and is also known as vasopressin.
The ADH is what helps your kidneys retain water, and leads to low sodium levels also known as hyponatremia well as excessive fluid accumulation.
The causes of SIADH include central nervous system disorders, brain tumors, meningitis, encephalitis, lung cancer such as small cell lung carcinoma, certain medications such as vincristine, cyclophosphamide and vasopressin, hypothyroidism and in some cases SIADH may be caused by something that is unknown.
The symptoms of SIADH include headaches, vomiting and nausea, confusion, disorientation, seizures in severe cases, low blood pressure and swelling also known as edema.
Diagnosis of SIADH include blood tests to check for low sodium levels in the blood also known as hyponatremia, urine tests to check for sodium levels and concentrated urine, and blood pressure tests to check for normal or low blood pressure.
Treatment for SIADH include fluid restriction, diuretics also known as water pills, salt tablets in severe cases and medications to suppress the ADH production such as demeclocycline.
And in some cases it you have a brain tumor the brain tumor will be removed.
Complications of SIADH include seizures, coma and brain damage.
Most people with SIADH recover fully although if the underlying cause of SIADH is not treated it can be life threatening.