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Course: Oncology Nursing

Topic: Nursing Management of

Oncological Emergency- SIADH

The Nurses International Community

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Module Goals

Learners will be able to:

Explain the underlying pathophysiology of SIADH.
Describe the scope of the problem including the incidence, etiology and risk factors for this oncologic emergency.
List the clinical manifestations that are associated with this emergency situation.
Explain the nursing assessment for SIADH including relevant diagnostic tests.
Characterize the nursing interventions and supportive care important to address this problem in a timely and effective manner.

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Syndrome of Inappropriate Antidiuretic Hormone(SIADH)

Syndrome of inappropriate antidiuretic hormone (SIADH) is a group of symptoms that develop when there is too much antidiuretic hormone (ADH) in the body.
Results from the inappropriate production and secretion of antidiuretic hormone (ADH also known as arginine vasopressin) which results in:

Water retention/ intoxication,
Hyponatremia and hypoosmolality

Canadian Cancer Society, 2021

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Incidence of (SIADH)

Approximately 67% of SIADH cases are reported to be caused by cancer.
The majority of which (70%) are linked to small cell carcinoma of the lung.
Head and neck cancers are responsible for only 1.5% of SIADH cases, however, the majority of these cases have the histology of small cell carcinoma.

Yoo et al., 2008

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Causes of (SIADH)

Cancer Care Nova Scotia, 2014

SIADH can be caused by the ectopic production of ADH by tumour tissue.
Small cell lung cancer is most often associated with SIADH.
Less common malignancies associated with SIADH include:

Breast
Carcinoid tumours
Head and neck
Duodenal
Esophageal
Pancreatic
Non-small cell lung cancer
Neuroblastoma
Ovarian
Prostate
Thymoma

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Causes of (SIADH)

Cancer Care Nova Scotia, 2014

Other possible causes of SIADH include cytotoxic chemotherapy and agents, including:

Cisplatin
Cyclophosphamide
Ifosfamide
Imatinib
Melphalan
Tricyclic antidepressants
Vinca alkaloids (Vinblastine, Vinorelbine, Vincristine, and Vindesine)

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Pathophysiology of SIADH

SIADH consists of:

Hyponatremia
Inappropriately elevated urine osmolality (greater than 100 mosm/kg)
Decreased serum osmolality in an euvolemic patient (no clinical signs of volume depletion of extracellular fluids)
Hyponatremia severity is based on the following levels:

Mild: 130–134 meq/L
Moderate: 125–129 meq/L
Profound: less than 125 meq/L

Tasler & Bruce, 2018

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Review Question:

Which is the most common cause of SIADH in a cancer patient? (Select the correct answer).

Cancer of head and neck
Small cell carcinoma of lungs
Breast cancer
Duodenal Cancer

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Sign and Symptoms of SIADH

Tasler & Bruce, 2018

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Sign and Symptoms of SIADH

Cancer Care Nova Scotia, 2014

Early symptoms of SIADH can include:

Abdominal cramping
Anorexia
Ataxia
Diarrhea
Difficulty concentrating
Headache
Vomiting
Irritability
Lethargy
Muscle cramps and weakness
Nausea
Oliguria
Thirst

Early signs include:

Hypoactive reflexes

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Signs and Symptoms of SIADH

Cancer Care Nova Scotia, 2014

Severe hyponatremia (serum sodium < 125 mmol/L) has serious and potentially life threatening consequences, particularly if onset is rapid (within 1-3 days), including:

Confusion
Hallucinations
Delirium
Seizures
Decerebrate posturing
Coma
Respiratory arrest

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What would the nurse do?

Mr. Mehra has a lung carcinoma. He has been treated with the chemotherapy drug called cyclophosphamide. During his hospital stay his serum sodium level was found to be <135 mmol/L. The nurse suspects that he could develop SIADH. What are the early sign and symptoms a nurse would assess for? (Select all that apply).

Oliguria
Muscle cramp
Abdominal crap
Nausea/vomiting

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Diagnosis of SIADH

Cancer Care Nova Scotia, 2014

Assessment:

History:

Perform health history
Questions about the symptoms

Physical and neurological exams:

Check the coordination and how well the patient’s muscles and reflexes are working

Investigation:

Electrolytes
Urea
Creatinine
Serum osmolality
Urine osmolality
Urine sodium

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Diagnosis of SIADH

Diagnosis of hyponatremia alone is not sufficient to diagnose SIADH
Essential features include:

Decreased effective serum osmolality (<275 mOsm/kg of water)
Urine osmolality >100 mOsm/kg of water during hypotonicity
Clinical euvolemia (no evidence of volume depletion or excessive volume of extracellular fluid)
Urinary sodium >40 mmol/L with normal dietary salt intake and normal thyroid and adrenal function

Cancer Care Nova Scotia, 2014

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Management of SIADH

Rapid treatment is indicated for symptomatic patients with severe hyponatremia that is known to have developed acutely (within the last 48hrs):

3% Hypertonic Saline IV infusion: Increase serum sodium by 1-2 mmol/L per hour (for the first 3-4 hours, then reduce correction rate to <0.5 mEq/L per hour)
Sodium correction should not exceed 8-10 mmol/L in 24 hrs or 18-25 mmol/L in 48 hrs*
A central IV line is required for infusions longer than 6h

Cancer Care Nova Scotia, 2014

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Management of SIADH

Patients with hyponatremia of unknown duration and non specific or absent symptoms require more cautious management

Modest correction of serum sodium by 0.5-1.0 mmol/L per hour via 0.9% saline infusion
Sodium correction should not exceed 8 mmol/L in 24 hrs and 18 mmol/L in 48 hrs
Consider use of salt tabs, loop diuretics

Rapid correction of serum sodium may cause osmotic demyelination characterized by lethargy, affective changes, mutism, dysarthria, spastic quadraparesis and pseudobulbular palsy

Cancer Care Nova Scotia, 2014

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Nurse’s Role in SIADH

Tasler & Bruce, 2018

Be aware of specific cancers and regimens that may predispose patients to hyponatremia.
Assess patients for:

Changes in mental status, irritability, headache, confusion, tremors, restlessness, nausea and vomiting, fatigue, and weakness.
Patients may present with a low urine output without hypovolemia.
Laboratory tests will show low sodium levels and decreased serum osmolality (less than 235 mosm/L).

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Nurse’s Role in SIADH

Tasler & Bruce, 2018

Nurse requires:

Close monitoring of intake and output
Maintaining fluid restriction
Daily weight check
Hemodynamic monitoring, and
Conducting frequent neurologic checks
Monitoring of serum sodium ( as often as every 2-3 hrs) is indicated to avoid rapid or over correction

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Nurse’s Role in SIADH

Tasler & Bruce, 2018

Emotional and supportive care

Educate patients and caregivers on:

The side effects of their treatment regimens
Specific cancers and regimens that may predispose patients to hyponatremia
Recognition of sign and symptoms/ prompt reporting
Fluid restrictions
High sodium diet
Monitor I/O and daily weight check

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Red Flags

Rapid correction of serum sodium may cause osmotic demyelination characterized by lethargy, affective changes, mutism, dysarthria, spastic quadraparesis and pseudobulbular palsy.
Clinical management of SIADH in-volves slowly normalizing patients’ sodium level during 24–48 hours. Replacing it too quickly can result in death.

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Case Study/Critical Thinking Question/What would the nurse do?

Miss Mina is a nurse who is looking after a cancer patient who suddenly developed SIADH. The patient is getting treated with 3% hypertonic saline to correct the hyponatremia and sign and symptoms of SIADH. What interventions are part of the nurse’s role while caring the patient? (Select all that apply).

Monitor Intake output
Daily weight check
Fluid restriction
Hemodynamic monitoring

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References

Canadian Cancer Society (2021). Syndrome of inappropriate antidiuretic hormone. Retrieved from: https://www.cancer.ca/en/cancer-information/diagnosis-and-treatment/managing-side-effects/syndrome-of-inappropriate-antidiuretic-hormone/?region=on

Yoo, M., Bediako, E. O., & Akca, O. (2008). Syndrome of inappropriate antidiuretic hormone (SIADH) secretion caused by squamous cell carcinoma of the nasopharynx: case report. Clinical and experimental otorhinolaryngology, 1(2), 110–112. https://doi.org/10.3342/ceo.2008.1.2.110

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References

Cancer Care Nova Scotia (2014). Guidelines for the Management of Oncologic Emergencies in Adult Patients – Full Version. © Crown copyright, Province of Nova Scotia.

Tasler, T., Bruce, S. D. (2018).Hyponatremia and SIADH: A Case Study for Nursing Consideration.Clinical Journal of Oncology Nursing.Volume 22, Issue 1 Retrieved from:https://cjon.ons.org/cjon/22/1/hyponatremia-and-siadh-case-study-nursing-consideration

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