ADH Disorders (DI & SIADH)

Question 1

What happens to cells when blood is hypernatremic?

Answer 1

Cells shrink

Question 2

What happens to cells when blood is hyponatremic?

Answer 2

Cells swell

Question 3

What is ADH’s response to increased plasma osmolality or to decreased circulating fluid volume?

Answer 3

Increased ADH secretion from posterior pituitary–> Decreased water excretion–> increased water retention–> increased circulation fluid volume–> decreased ADH

Question 4

What is the body’s thirst response to increased plasma osmolality or to decreased circulating fluid volume?

Answer 4

Increased thirst –> increased fluid intake –> increased water retention–> increased circulating fluid volume –> decreased thirst

Question 5

Another term for ADH

Answer 5

Vasopressin

Question 6

What does SIADH stand for?

Answer 6

Syndrome of Inappropriate ADH

Question 7

What happens in SIADH?

Answer 7

There is an overproduction of ADH which causes excess water reabsorption. This has a dilutional effect on serum sodium levels. Cells swell as fluid shifts into intracellular spaces.

Question 8

What is the most common cause of SIADH?

Answer 8

Ectopic ADH production from lung cancer cells

Question 9

What kind of disorder is occurring when lung cancer cells secrete ADH?

Answer 9

This is an example of a paraneoplastic disorder. The vasopressin is secreted by a tumor.

Question 10

Why does diabetes insipidus occur?

Answer 10

There is an underproduction of ADH

Question 11

What are the 2 causes of DI?

Answer 11

1. Neurogenic causes
2. Nephrogenic causes

There are also psychogenic causes

Question 12

What is an example of a neurogenic cause of DI?

Answer 12

Head trauma, especially trauma to the pituitary

Question 13

What is the most common cause of drug-induced nephrogenic DI?

Answer 13

Lithium

Question 14

What is the pathology behind nephrogenic DI?

Answer 14

There may be adequate ADH levels in the blood, but the kidneys do not respond

Question 15

What is the pathophysiology behind SIADH?

Answer 15

Increased ADH–> increased water reabsorption in the renal tubules –> increased intravascular fluid volume–> Dilutional hyponatremia & decreased serum osmolality

Question 16

What serum level of sodium causes severe symptoms of SIADH?

Answer 16

<100-115 mEq/L

Question 17

What are the clinical manifestations of SIADH?

Answer 17

Depend on severity & rate of onset of hyponatremia, but S/S of hyponatremia:

• Muscle cramping
• Dyspnea
• Fatigue
• Neurologic symptoms: dulled sensorium, confusion, lethargy
• GI symptoms: impaired taste, anorexia

Question 18

What are 2 priority nursing problems for SIADH patients?

Answer 18

1. Fluid volume excess

2. Risk for injury (due to altered mental status r/t hyponatremia)

Question 19

What are nursing interventions for SIADH patients?

Answer 19

Assess for S/S fluid volume overload
Monitor I&Os; daily weights
Monitor LOC & changes in mental status
Restrict fluids as ordered
Administer IVF per order (closely monitor rate)
Administer meds as ordered (not 1st line treatment)
Support patient & family

Question 20

What is the immediate goal when caring for a patient with SIADH?

Answer 20

To restore normal fluid volume & osmolality

Question 21

Generally, how is drug therapy used in SIADH patients?

Answer 21

Only used in patients with chronic SIADH. Sometimes diuretics are used; sometimes demeclocycline (which blocks the effects of ADH) is used

Question 22

If an SIADH patient has severe symptoms and/or severe hyponatremia (<120 mEq/L), what IVF do they receive?

Answer 22

Hypertonic NS (3-5%) IV VERY SLOWLY over hours to days to prevent abrupt fluid shifts within the brain cells

Question 23

What is the pathophysiology of diabetes insipidus?

Answer 23

Decreased ADH –> decreased water reabsorption in renal tubules–> decreased intravascular fluid volume –> increased serum osmolality (hypernatremia) AND excessive urine output

Question 24

Describe the onset & nature of neurogenic (“central”) causes of DI.

Answer 24

Usually abrupt onset
Has the most severe signs & symptoms
If caused by head trauma
It is self-limiting meaning it will resolve on its own, but the symptoms need to be treated.

Question 25

Describe the onset & nature of nephrogenic causes of DI.

Answer 25

Less abrupt onset & less severe symptoms than central DI

Question 26

What are the characteristics of a DI patient’s urine?

Answer 26

They would produce 5-20 L/day (polyuria)
Very low specific gravity (<1.010); very diluted
Very low urine osmolality

Question 27

What are the characteristics of a DI patient’s blood?

Answer 27

High osmolality/very concentrated (300 mOsm or greater)

Question 28

Clinical manifestations of DI

Answer 28

1. Polyuria (5-20 L/day)
2. Polydipsia (extreme thirst as a mechanism to dilute their very concentrated blood)
3. Fatigue (unable to sleep due to nocturia)
4. Weakness

Question 29

2 priority nursing problems for DI

Answer 29

1. Fluid volume deficit

2. Risk for injury (altered mental status r/t hypernatremia)

Question 30

What is the expected range for urine specific gravity?

Answer 30

1.010-1.030

Question 31

What is the expected range for serum osmolality?

Answer 31

270-290 mOsm

Question 32

What is the expected serum sodium level?

Answer 32

135-145 mEq/L

Question 33

Nursing care for deficient fluid volume in DI patients

Answer 33

Administer IVFs
Pharmacotherapy
I&Os; daily weights
Monitor labs (urine specific gravity, serum osmolality, serum sodium)
Notify HCP if increase in urine volume w/decreased specific gravity

Question 34

Drug therapy for neurogenic DI

Answer 34

Desmopressin (DDAVP), which is synthetic ADH

Question 35

What routes can desmopressin be administered?

Answer 35

Nasal spray, PO, IV, SQ