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Syndrome of Inappropriate Antidiuresis.

Syndrome of inappropriate antidiuresis (SIAD) results from excessive secretion of vasopressin (antidiuretic hormone) or increased response by the kidneys to vasopressin. Many factors can increase patients' risk for developing SIAD, including pulmonary diseases, cancer, neurologic conditions, general anesthesia, surgery, nausea, pain, and stress (Cuesta, Garrahy, & Thompson, 2016; Quinn, 2016; Spasvoski et al., 2014). SIAD is characterized by hyponatremia with a normal fluid volume. Normally, when the serum becomes hyponatremic and hyposmolar, secretion of vasopressin is suppressed and more water is excreted in the urine to correct the problem. In SIAD, the urine continues to be relatively concentrated despite low serum osmolarity. Patients with SIAD have low serum sodium and lower output of relatively concentrated urine. Patients with hyponatremia often do not have obvious symptoms; instead, subtle signs often occur, including gait disturbances, falls, and cognitive changes (Cuesta et al., 2016; Spasvoski et al., 2014).

Treatment of SIAD is determined by the severity of hyponatremia. Mild (sodium 130-135 mEq/L) or moderate (sodium 125-129 mEq/L) hyponatremia usually is treated first with fluid restriction (Cuesta et al., 2016; Quinn, 2016; Spasvoski et al., 2014). Fluid restriction is often difficult for patients to tolerate and is not always successful (Cuesta et al., 2016; Spasvoski et al., 2014).

Another treatment option is tolvaptan (Samsca[R]), a vasopressin receptor antagonist. Although use of tolvaptan results in increased serum sodium, research has not confirmed tolvaptan reduces mortality or morbidity (Cuesta et al., 2016; Spasvoski et al., 2014). Treatment with hypertonic saline (3%) is restricted for profound hyponatremia (sodium <125 mEq/L) or hyponatremia with significant symptoms. Correcting hyponatremia too rapidly can lead to cerebral osmotic demyelination and increase risk for permanent brain damage (Spasvoski et al., 2014).

Case Study

Henrietta James is a 75-year-old woman who underwent a wedge resection for non-small cell lung cancer 2 days ago. The laboratory reports her serum sodium is 128 mEq/L. The nurse suspects SIAD.


1. Which of the following in Mrs. James' history increases her risk for SIAD?

a. Cancer only

b. Cancer and surgery only

c. Cancer, surgery, and pain, only

d. Cancer, surgery, pain, and female sex

2. Which nursing measure is most important for initiation with this patient?

a. Seizure precautions

b. Fall precautions

c. Bedrest

d. Cardiac monitoring

3. The nurse reports the sodium value to the healthcare provider. Which orders should the nurse expect to receive for this patient?

a. Fluid restriction

b. Infusion of 3% saline

c. Increasing sodium intake

d. Serial serum sodium only

Answers with Rationale

1. C - Cancer, surgery, and pain increase the risk for developing SIAD. Female sex does not increase the risk for SIAD.

2. B - Hyponatremia may cause subtle gait and cognitive changes, and increase the risk for falls. Profound hyponatremia may cause seizures, but seizures are not likely with moderate hyponatremia. Bedrest is not necessary. Cardiac dysrhythmias other than tachycardia are not common in hyponatremia.

3. A - Fluid restriction is the treatment of choice for moderate hyponatremia caused by SIAD. Infusion of 3% saline is reserved for profound hyponatremia and hyponatremia with severe symptoms. Moderate hyponatremia should be treated, not merely observed. Increasing sodium intake alone is not a recommended treatment.


Cuesta, M., Garrahy, A., & Thompson, C.J. (2016). SIAD: Practical recommendations for diagnosis and management. Journal of Endocrinological Investigation, 39(9), 991-1001. doi:10.1007/s40618016-0463-3

Quinn, L. (2016). The endocrine system. In H. Craven (Ed.), Core curriculum for medical-surgical nursing (5th ed.) (pp. 311-350). Pitman, NJ: Academy of Medical-Surgical Nurses.

Spasovski, G., Vanholder, R., Allolio, B., Annane, D., Ball, S., Bichet, D., ... Nagler, E. (2014). Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrology, Dialysis, Transplantation, 29(Suppl. 2), i1-i39. doi:10.1093/ndt/gfu040

Cynthia A. Frazer, MS, RN, CMSRN[R], CNE, is Chair, MSNCB Test Development Committee, and Associate Professor, Department of Associate Degree Nursing, Eastern Kentucky University, Richmond, KY.
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Title Annotation:Preparing for CMSRN[R] Certification
Author:Frazer, Cynthia A.
Publication:MedSurg Nursing
Geographic Code:1USA
Date:Sep 1, 2017
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