SIADH & DI

What is SIADH?

a condition where ADH is overproduced or released despite normal/low plasma osmolarity, leading to water retention and dilutional hyponatremia

What does ADH normally do?

Increases permeability of the renal distal tubule and collecting duct, causing water reabsorption into circulation.

What happens when ADH is too high?

fluid retention, low plasma osmolality, increased GFR, and dilutional hyponatremia

What electrolyte imbalance is caused by SIADH?

dilutional hyponatremia (low sodium)

What are the main features of SIADH?

fluid retention, serum hypoosmolality, dilutional hyponatremia, concentrated urine

Which population is most commonly affected by SIADH?

older adults

What is the most common cause of SIADH?

Cancer, especially small cell lung cancer.

is SIADH self-limiting or chronic?

it may be self-limiting with head trauma or drugs, but chronic when caused by tumors or metabolic diseases

does ADH impact electrolytes other than sodium?

no it only effects water balance

What are the nursing concerns in SIADH?

monitoring sodium , kidney function, LOC, blood pressure, and respiratory status for fluid overload

What pulmonary complication may occur in SIADH?

fluid in the lungs —> crackles, noisy breathing, SOB, heart overstretching from fluid overload

what are early clinical manifestations of SIADH?

low urine output, increased body weight, thirst, dyspnea on exertion, fatigue

What are signs of mild hyponatremia in SIADH?

muscle cramping, irritability, and headache

What happens when serum sodium drops below 120 mEq/L?

Severe symptoms:

• vomiting

• abdominal cramps

• muscle twitching.

What happens as plasma osmolality and serum sodium decline further?

cerebral edema —> lethargy, confusion, seizures, coma

What diagnostic studies confirm SIADH?

simultaneous urine and serum osmolality tests

What lab findings support SIADH diagnosis?

serum sodium <135 mEq/L, serum osmolality <280, urine specific gravity >1.030

What does it mean if serum osmolality is much lower than urine osmolality?

the body is excreting concentrated urine despite dilute serum 

What is the normal range of urine specific gravity?

1.005-1.035

What does a low urine specific gravity mean?

dilute urine

What does a high urine specific gravity mean?

concentrated urine

What nursing interventions are key for SIADH?

strict I&Os, daily weights, fluid restriction, assess breath sounds, monitor for crackles, shortness of breath, and signs of fluid volume overload

How do urine and serum osmolality typically compare in SIADH?

they are opposite- serum is dilute, urine is concentrated

What key signs should nurses monitor for in SIADH patients?

Low urine output with high specific gravity, sudden weight gain without edema, decreased serum sodium, seizures, headache, vomiting, and decreased neurologic function.

What daily monitoring is essential for SIADH patients?

Intake and output, vital signs, heart and lung sounds, and daily weights

What should be done with medications that stimulate ADH release?

they should be avoided or discontinued

What is the initial treatment if SIADH is mild and serum sodium is >125 mEq/L?

fluid restriction of 800-1000 mL/day

What should improve as serum sodium and osmolality normalize?

symptoms, weight loss, and overall clinical status

How can nurses help patients cope with fluid restriction discomfort?

provide frequent oral care and distractions to reduce thirst

Which diuretic may be used in SIADH to promote diuresis?

loop diuretics (Lasix/furosemide)

What must serum sodium be before loop diuretics are used in SIADH?

at least 125 mEq/L

What supplements might patients on loop diuretics require?

potassium, calcium, magnesium

Which antibiotic can be used to block ADH’s effect on renal tubules?

demeclocycline

What is the effect of demeclocycline?

Blocks ADH’s action on renal tubules, producing more dilute urine.

What nursing precautions are important if the patient has altered sensorium or seizures?

initiate seizure and fall precautions

Why should the HOB be flat or no more than 10 degrees in SIADH?

to promote venous return, increase left atrial filling, and reduce ADH release

What nursing care helps maintain mobility and skin integrity in SIADH?

frequent turning, positioning, and range-of-motion exercises

How is severe hyponatremia (<120 mEq/L with neurologic symptoms) treated?

small amounts of IV hypertonic saline (3% NaCl)

How fast should sodium correction occur in SIADH?

No more than 8–12 mEq/L in the first 24 hours.

Why must sodium be corrected slowly in SIADH?

To prevent osmotic demyelination syndrome (permanent brain damage).

In severe cases, how much may fluids be restricted?

500 mL/day

Which vasopressor receptor antagonists are approved in the U.S. for SIADH?

conivaptan (IV) and Tolvaptan (PO)

What do vasopressor receptor antagonists do?

block ADH activity to treat euvolemic hyponatremia

Who should not receive conivaptan or tolvaptan?

Patients with liver disease (they worsen liver function).

What comfort measures can help patients with chronic SIADH reduce thirst?

Ice chips and sugarless chewing gum.

What education should SIADH patients receive?

Signs/symptoms of fluid and electrolyte imbalances, especially sodium and potassium.

What is the cause of Diabetes Insipidus (DI)?

deficient production/secretion of ADH or decreased renal response to ADH

Does DI involve insulin problems?

no, DI is unrelated to insulin or blood glucose

what imbalance results from decreased ADH in DI?

increased urine output and increased plasma osmolality

What are the hallmark symptoms of DI?

polydipsia (excessive thirst) and polyuria (excessive urination)

How much urine may a DI patient excrete per day?

2-20 Liters/day

What is the urine specific gravity in DI?

very low (<1.005)

what is urine osmolality in DI?

<100 mOsm/kg

What happens to serum osmolality in DI?

increased due to hypernatremia

What serum sodium finding is common in DI?

hypernatremia

What are the most common causes of DI?

Tumors, CNS infections, and head injury

What mnemonic is often used to remember DI?

“dry inside” (too much water lost)

What are some early clinical manifestations of DI?

excessive thirst, nocturne, fatigue, generalized weakness

What CNS complications can uncorrected hypernatremia in DI cause?

brain shrinkage and intracranial bleeding

what happens to urine and serum concentration in DI?

urine = very dilute, serum = very concentrated

what vital sign changes occur with severe dehydration in DI?

hypotension, tachycardia, possible hypovolemic shock

what CNS manifestations may occur from hypernatremia in DI?

irritability, mental dullness, coma

What is the triphasic pattern of central DI after intracranial surgery?

1. acute phase with polyuria

2. interphase with normalized urine output

3. permanent central DI (10-14 days post op)

Is central DI from head trauma usually permanent?

no, it is often self limiting

what is the emergency concern in DI?

severe dehydration and low fluid balance

What nursing assessments are critical in DI?

LOC, vital signs, I&Os, daily weights, serum labs, hourly urine specific gravity

What treatment may be needed in DI?

hormone replacement therapy (desmopressin for central DI) and IV fluids

Why would ECG monitoring be helpful in DI?

to watch for electrolyte-related cardiac effects, especially from hyponatremia

What is the main diagnostic test for central DI?

the water deprivation test

What is measured before a water deprivation test?

body weight, urine osmolality, volume, and specific gravity

How long is water withheld during a water deprivation test?

8-12 hours

What medication is given after the water deprivation period in central DI testing?

DDAVP (desmopressin), given subcutaneously or nasally

How does urine osmolality change in central DI after DDAVP is given?

it dramatically increases while urine volume significantly decreases

What alternative test can help distinguish central DI from nephrogenic DI?

measuring ADH levels after giving an analog of ADH (desmopressin)

What are the main management goals in DI?

early detection, adequate hydration, and patient teaching for self-management

What is the clinical goal of DI management?

maintaining fluid and electrolyte balance

What are the cornerstones of central DI treatment?

fluid replacement and hormone therapy

What IV solutions are commonly used in acute DI?

IV hypotonic saline or D5W

What must be monitored if IV glucose solutions are given for DI?

serum glucose (to prevent hyperglycemia and glycosuria) which can worsen fluid loss

What vital signs and parameters should be monitored frequently in acute DI?

BP, HR, urine output, LOC, and specific gravity (sometimes hourly)

What ongoing assessments are important in DI patients?

signs of acute dehydration, intake and output records, and daily weights

What is the hormone replacement of choice for central DI?

desmopressin (DDVAP)

What is another ADH replacement drug for central DI?

aqueous vasopressin

Why is hormone therapy ineffective in nephrogenic DI?

because the kidneys cannot respond to ADH

What is the mainstay of treatment for nephrogenic DI?

low-sodium diet and thiazide diuretics to reduce the flow of ADH-sensitive nephrons

What drug may be prescribed if a low-sodium diet and thiazides are not effective in nephrogenic DI?

indomethacin, an NSAID

How does indomethacin help in nephrogenic DI?

in increases renal responsiveness to ADH

What vital sign assessments are important after pituitary surgery?

monitor vital signs, assess peripheral pulses, and watch for orthostatic hypotension

How often should neurologic and cognitive status be assessed after pituitary surgery?

hourly for the first 24 hours, then every 4 hours

What specific neuro checks should be done post-pituitary surgery?

LOC, orientation, speech, extremity strength, and reflexes

What eye-related assessments are needed after pituitary surgery?

monitor field of vision, visual acuity, extra ocular movements, and pupillary response. Notify HCP if there are any changes

what should you monitor on the surgical dressing after pituitary surgery?

type and amount of drainage; notify HCP for excessive bleeding or CSF drainage

How is CSF drainage detected from a “moustache” dressing?

test clear drainage with a urine dipstick for glucose and protein

What glucose level in drainage suggests a CSF leak?

greater than 30 mg/dL

Why is a CSF leak dangerous after pituitary surgery?

it indicates an open connection with the brain and increases the risk for meningitis

What symptom may indicate CSF in the sinuses post-surgery?

persistent, severe generalized or supraorbital headache (usually resolves within 72 hours)

What position should the patient be kept in after pituitary surgery?

HOB at least 30 degrees; maintain bedrest

What respiratory interventions are encouraged after pituitary surgery?

deep-breathing exercises and incentive spirometer use

What activities should the patient avoid to prevent increased ICP after pituitary surgery?

vigorous coughing, sneezing, blowing the nose, bending over, and straining at stool

What dietary teaching should be included for patients after pituitary surgery?

encourage a high-fiber diet and stool softeners to prevent constipation and straining