ATI Unit 12 Posterior Pituitary Disorders

Question 1

what does the posterior pituitary gland secrete and what does under- and oversecretion of this do?

Answer 1

• secretes vasopressin or ADH (antidiuretic hormone)
• oversecretion = SIADH (syndrome of inappropriate ADH) where you hold on to too much water and there’s little urine outpus
• undersecretion of ADH = diabetes insipidus, always too much urine output, hypotension, thirst

(both often result in fluid/electrolyte imbalances)

Question 2

what are the three types of diabetes insipidus

Answer 2

1) primary = hypothalamus or posterior pituitary messed up
2) nephrogenic = inherited problem in renal tubules (don’t react to vasopressin/ADH)
3) drug-induced = lithium carbonate (Lithium) or demeclocycline (Declomycin)

Question 3

what two drugs can induce diabetes insipidus?

Answer 3

1. lithium carbonate (Lithium)
   2) demeclocycline (Declomycin)
   - changes how kidneys respond to ADH

Question 4

so what are some assessments you want to check out with diabetes insipidus?

Answer 4

1. are they taking lithium or demeclocycline
2. is there anything cranial related: think tumors, trauma, cranial surgery, and infection (meningitis, encephalitis)
3. dehydration/decreased thirst response
4. people with renal failure/insufficiencies
5. are they using diuretics?
6. dysphagia/poor food intake

Question 5

subjective and objective findings of diabetes insipidus

Answer 5

Subjective

• polyuria (output of 4-20 L/day of dilute urine)
• polydipsia (excessive thirst, 2-20L/day)
• nocturia
• fatigue
• dehydration EVB thirst, weight loss, muscle weakness, headache, constipation, dizzinesss

Objective

• sunken eyes
• tachycardia
• hypotension
• loss of skin turgor
• dry mucous membranes

Question 6

Lab tests for diabetes insipidus

Answer 6

Urine (DILUTE)
Decreased urine…..
- urine specific gravity (less than 1.005)
- urine osmolality (less than 300 mOsm/L)
- pH
- Na+, K+
(as urine volume increases, osmolality decreases)

Serum (CONCENTRATED)
- increased everything (as serum volume decreases, osmolality increases)

Radioimmunoassay - decreased ADH

Question 7

using a water deprivation test for diabetes insipidus

Answer 7

• basically withhold fluids and see if urine still stay diluted despite this
• if postural hypotension, dizziness, tachycardia develop, STOP, patient is dehydrated

Question 8

using a vasopressin test for diabetes insipidus

Answer 8

• a subq vasopressin shot is given and if patient has diabetes insipidus, urine output after shot will be increased specific gravity
• differentiates nephrogenic from central DI

Question 9

if a patient has diabetes insipidus what’s a food to avoid?

Answer 9

caffeine - diuretic effect

Question 10

if a patient with DI develops constipation what foods would help?

Answer 10

bulk food and fruit juices

Question 11

what meds are given for DI?

Answer 11

1. ADH replacement agents (desmopressin acetate or DDAVP; aqueous vasopressin or Pitressin)
   - synthetic ADH
   - teachings: weight, I/O match, electrolytes, specific gravity
2. ADH stimulants - carbamazepine (Tegretol)
   - anticonvulsants stimulate release of ADH
   - monitor for thrombocytopenia (bruising, fever, sore throat)
3. vasopressin (Pitressin)
   - the hormone
   - can cause vasoconstriction so caution in clients with CAD
   - water intoxication: headache, confusion
   - lifelong therapy

Question 12

what weight gain should a client report?

Answer 12

greater than 0.9kg (2lb)

Question 13

what is the general change in the body that SIADH causes?

Answer 13

• posterior pituitary releasing too much ADH
• water is reabsorbed
• renin-angiotensin system blocked and sodium still secreted
  Leads too….
  water intoxification
  dilutional hyponatremia
  cellular edema (can cause decreased serum osmolality b/c of fluid shifts)

Question 14

so what are the risk factors in a patient with SIADH?

Answer 14

• malignant tumors like the oat-cell lung cancer can cause hypersecretion
• another is increased intrathoracic pressure like with positive pressure ventilation
  other: cranial trauma, meningitis, stroke, pain, stress, meds

NOTE
diuretics can further complicate sodium losses

Question 15

which meds can cause SIADH

Answer 15

• alcohol
• lithium carbonate
• phenytoin

Question 16

major assessments in SIADH

Answer 16

• bad bad: confusion lethargy and Cheyne-Stokes respiration mean impending crisis; when Na+ level drop further = seizures, coma, death
• manifestations of volume excess: hypertension, tachycardia, crackles in lung, distended neck beins, taut skin, intake > output

Question 17

Lab tests for SIADH

Answer 17

Urine (Concentrated)
increases specific gravity, Na+, osmolarity

Serum/Blood (DILUTE)

Question 18

what is the first priority in nursing care for SIADH

Answer 18

prevent further hemodilution

• restrict oral fluids 500-1000mL/day
• comfort measures includes mouth care, ice chips, lozenges, and staggered water intake for thirst

Question 19

nursing care for SIADH

Answer 19

a. flush tubes with NS not H2O to replace Na+ and prevent further hemodilution
- I/Os
- monitor for up BP, tachycardia, hypothermia
- weight daily (.9kg/2lbs = 1L of fluid)
- diuretic possible if fluid overload loop diuretic

Question 20

medications for SIADH

Answer 20

1) demeclocycline (Declomycin)
- tetracycline derivative
- may cause DI
- may take week
- monitor for yeast infection
- client rinse toothbrush with diluted 10% bleach solution and increase yogurt consumption

2) lithium carbonate
- blocks renal response to ADH
- poss DI
- monitor for lithium toxicity, tremors, ataxia, NVD
- monitor blood glugose

3) furosemide (Lasix)
- causes Na+ exretion may worsen dilutional hyponatremia (nausea, decreased appetite, vomitting)

4) administer hypertonic fluids
- SOB could mean heart failure

Question 21

what are the complications of SIADH

Answer 21

water intoxication, cerebral edema, severe hyponatremia

Question 22

what are the symptoms of water intoxication

Answer 22

lung crackes, distended neck beins, neuro status changes, edema, decreased urinary output

Question 23

what is CPM

Answer 23

central pontine myelinolysis
- condition from SIADH treatment characterized by nerve damage b/c of myelin sheath destruction in brainstem (pons); common cause is rapid change in Na+ levels in body (hyponatremia treated and levels rise too fast)

• when treating, monitor serum sodium levels and neuro status q2-4hrs