Disorders of the Posterior Pituitary

Diabetes Insipidus

Syndrome of Inappropriate Antidiuretic Hormone (SAIDH)

Posterior Pituitary

Posterior pituitary hormones are actually produced in the hyopthalamus and only stored in the posterior pituitary

Posterior pituitary hormones

Antidiuretic hormone (ADH)

Oxytocin

The hormones secreted by the posterior pituitary are Antidiuretic hormone (ADH) (Also call vasopressin)and oxytocin.

ADH contributes to fluid balance by Controlling renal reabsorption of free water It also has potent vasoconstrictive properties.

Posterior PituitaryAntidiuretic hormone (ADH) (Also called vasopressin)

Disorders/diseases resulting from dysfunction

Excess: Syndrome of Inappropriate ADH secretion (SIADH)

Deficiency: Diabetes Insipidus

SIADHPosterior Pituitary Hypersecretion

SIADH - Syndrome of Inappropriate Hormone Secretion

ADH (anti-diuretic hormone) is a hormone made in the pituitary gland.

ADH does what the name says - it stops urination - diuresis

Slowing or stopping urine production leads to fluid retention.

That in turn causes a dilution of body sodium

SIADH - Syndrome of Inappropriate Hormone Secretion

Depending on the rapidity & the extent of the sodium drop, a battery of S/S appear.

Lethargy, weakness, & foggy thinking are common. Personality changes can happen.

Low sodium levels often make pt nauseated

If the situation is not corrected, seizures, coma, & even death can follow.

Syndrome of Inappropriate Antidiuretic Hormone Secretion - SIADHSIADH occurs when there is too much vasopression (ADH) with inappropriate water retention and decreased blood Na levelsResults from many different conditions and drugsMay be produced by certain tumors such as lung cancer or may result from chronic lung diseases. Medicines associated with SIADH include common meds as antidepressants, antianxiety agents, antipsychotic agents, seizure meds, and desmopressin (DDAVP)

Syndrome of Inappropriate Antidiuretic Hormone Secretion - SIADH

Results fromInability to produce & secrete dilute urineWater retentionIncreased extra cellular fluid volumeHyponatremia Diseases that affect the hypothalamus

Dx of SIADHThe following criteria should be fulfilled before a diagnosis of SIADH can be made:

persistent excretion of concentrated urine with no reason for ADH release

normal renal and adrenal function

no edema or hypovolaemia should be present

the urine osmolarity should be greater than the serum osmolarity

Physical Assessment of SIADHInitially, S/S are R/T retention of water.

Most common complaintsGI disturbances-loss of appetite, N,V

Nurse Weighs pt & documents any recent weight gainChecks pt extremities for presence of edema

Pt with SIADH have free water, not salt, that is retained & edema is not usually present due to intracellular free water

Assessment-Clinical Manifestations of SIADHWater retention, hyponatremia, & resulting fluid shifts have an effect on CNS function, especially when serum sodium level drops. Normal serum Na 135-145. S/S occur when serum Na level drops below 125, and especially below 115Clinical S/SLethargy, headaches, hostility, uncooperativeness, disorientationEarly sign -Change in LOCNeurological S/S can progress from lethargy and headaches to decreased responsiveness, seizures, and coma.Nurse assess deep tendon reflexes, which are often < or sluggishV/S changes-tachycardia associated with increased fluid volume & hypothermia associated with CNS disturbance

Normal Lab Values

serum osmolality (285-295 mOsm/kg)sodium (Na 135-145 mEq/L)

chloride (95-105 mEq/L)Urine osmolality - -24 hr specimen 500-800 mOsm/kg H20 -Random specimen: 50-1200 mOsm/kg/H20

Osmolality is measures in milliosmoles per kilogram of water (mOsm/kg). The major determinants of plasma osmolality are Na, glucose, & ureaUrine specific gravity1.003-1.0301.002-1.035High=dehydrationLow=diabetes insipidusconcerntrated urine > than 50-100 mOsm/kg with normal vascular volume and normal renal function

Lab Assessment in SIADHExtracellular fluid volume expansion affects electrolyte levels in the serum and the urine

Elevated urine sodium levels and specific gravity reflect an increased concentration of the urine

Serum sodium levels are decreased, often as low as 110 mEq/L (normal serum sodium 135-145 mEq/L) due to extracellular volume expansion and increased Na excretion

Fluid retention causes changes in both plasma and urine osmolality

Plasma osmolality is decreased, and the urine is hyperosmolar in relation to the plasma

Osmolality Urine osmolality -24 hr specimen 500-800 mOsm/kg H20Random specimen: 50-1200 mOsm/kg/H20 Osmolality is measures in milliosmoles per kilogram of water (mOsm/kg). The major determinants of plasma osmolality are Na, glucose, & urea.

The Kidneys are mainly responsible for maintaining the concentration of body fluids within this range of osmolality.

When the plasma osmolality becomes abnormal, changes in the level of antidiuretic hormones (ADH) cause the kidneys to conserve or increase the excretion of water to return the osmolality to normal

Posterior Pituitary hypersecretion - SIADH

Symptoms - fluid retention low serum osmolality (normal285-295 mOsm/kg)

dilutional low sodium (normal Na 135-145 mEq/L)

low chloride (normal95-105 mEq/L)Causes-Diseases effect the hypothalmus

pneumonia TB positive pressure ventilationTraumaconcerntrated urine (> than 50-100 mOsm/kg) with normal vascular volume and normal renal function

muscle cramps & weaknesscerebral edema, lethargy, anorexia, headache, seizures, coma.

AIDsdelirium tremensEctopic ADH secreting tumor

SIADH - Diagnostic TestsBlood & Urine tests

Must have low serum sodium

low plasma osmolality level

Inappropriated concentrated urine (increased urine osmolality level)These tests indicate excess of body water relative to the amount of body sodium.In other words, ADH is inappropriately holding onto too much water.Important to eliminate other causes of a low sodium level, such as hypothyroidism or adrenal insufficiency, before settling on a dx of SIADHRx- removing the offending drug or tumor, & treat the underlying condition.

Posterior Pituitary: SIADH,DI*Affect kidneys ability to concentrate urine*

Measured by urine specific gravityMeasures number and size of particles

Normal: 1.003 - 1.030High = dehydrationLow = Diabetic Insipidus 1.001-1.005

Concentrated urine: SIADHDilute urine: DI

Posterior pituitary: SIADHADH excess = water intoxication

water is reabsorbed, so assess forincreased blood volume, fluid retentionconcentrated urine, low urine outputdilutional hyponatremia (same Na, more H20)muscle cramps and weaknessanorexia, n/v, irritable, confused, disorient, seizure

SIADH and HyponatremiaHyponatremia- a lower than normal concentration of sodium in the blood

Caused by inadequate excretion of water of by excessive water in the circulating bloodstream

In a severe case the pt may experience water intoxication, with confusion and lethargy, leading to muscle excitability, convulsions, and coma.

Treatment: Fluid and electrolyte balance may be restored by IV infusion of a balanced solution or a fluid restricted diet.

SIADHDiagnosis & Treatment

Diagnosis measure urine volumeand osmolality

TreatmentIf Na280mmol/kgSG>1005low BUN, creatinine, Hb, Hct.

Lasix if Na

SIADHDiagnostic StudyHyponatremiaDecreased plasma osmolalityUrine sodium and urine osmolality elevatedElevated ADH levels++++++Normal renal, adrenal, & thyroid functionsNursing Assessment

Headache,Personality change, Confusion,Irrritability, Dysarthria(difficult, poorly articulated speech), Lethargy,Impaired memory

Restless, weakness, fatigue, gait disturbances

Weight gain+++++

SIADH TreatmentWater Restriction is the cornerstone of treatment

Decreased water intake allows serum sodium level to rise normally.

The maximum amount of water that pt with SIADH are allowed to drink is just slightly more that the amount of urine they produce

Pt must have regular serum sodium measurements to ensure that the water restriction has been effective

Dehydration- The most concerning potential side effect from treatment is dehydration.

SIADH treatmentRestrict fluid intake (800-1000 cc/day)Daily weight Strict I & OMonitor urine specific gravity0.9 NS infusion(to raise the serum Na level if water intoxication is severe) Monitor for hyponatremia Lasix may be admin to block circulatory overloadDrugs-demeclocyclin HCL & lithium-may be admin to block renal response to ADH, intereferes with action of ADHDrugs - Phenytoin - inhibits ADH releaseSurgery & Chemo -to remove or destroy neoplasms that may be the underlying cause of this syndrome

SIADH treatment

Demeclocycline (Declomycin)Lithium

Used for: Excess secretion of ADH or SIADHAction:Inhibits ADH action in kidneyBlocks renal response to ADH, interferes with action of ADHTherapeutic outcome:Decreased urine specific gravity

Analysis - Nursing Diagnosis - SIADH1. Fluid Volume Excess R/T compromised regulatory mechanism, excess ADH

2. High Risk for Injury R/T an altered level of consciousness, confusion, & the possibility of seizures

3. Altered Nutrition: Less than Body Requirements R/T an inability to ingest or digest food or absorb nutrients because of biologic factors (ex-anorexia, N/V)

4. Altered Thought Processes R/T physiologic changes within the central nervous system

Planning & ImplementationPlanning: Pt GoalsThe primary goal is that the pts fluid balance will be restored

Interventions to treat SIADH (Pt Care Plan) consists ofRestriction water intakeUsing diuretics to promote the excretion of waterAdministering drugs that interfere with the action of ADHReplacing lost sodiumFluid RestrictionAny excessive free water intake will further dilute the serum sodium concentrationStrict I&O, daily weights, guides the determination of the degree of fluid restriction necessary. A wt gain of 2 pounds (or 1 Kg) or more per day or a gradual increase during several days is cause for concern.A 1 Kg weight increase is equivalent to 1000ml fluid retention (1Kg = 1 L)

Planning & ImplementationDrug TherapyDiuretics are sometimes used to treat pt with SIADH, to rid the body of excessive fluid, especially if CHF results from fluid overload

If diuretics are used, be aware of potential effect of electrolyte losses; sodium loss can be potentiated, which further contributes to the clinical picture of SIADHHypertonic saline (3% NaCl) may be used to treat SIADH Helps correct serum sodium levelRaises Na osmolality in the blood Removes excess intracellular fluidCells shrink in hypertonic solution

IV saline is given cautiously because it may contribute to the fluid overload already present & precipitate an episode of CHF.

If the pt needs routine IV fluids, the MD orders a solution in saline (5% dextrose in saline) rather than a solution in water.

Planning & ImplementationHigh Risk for InjuryPromote safetyMonitor pt neuro statusSubtle Changes, such as muscle twitching before neuro S/S progress to seizures or coma. Check LOC to time, place, & person because disorientation may be present. Confusion is another neuro sign. Nurse reduces environmental stimuli & explain interventions in simple terms.

Flow sheets contain ongoing info about LOC, motor & sensory neuro assessment, & pertinent lab data helpful in detecting trends.

Decreased LOC and seizures are complications of the low serum sodium level R/T SIADH

Nursing issuesMonitoring fluid balance(s/s fluid retention):

Cardiac problems (water reabsorbed so >bld volume):

Neurological problems (headache seizures,cerebral edema, coma,):

Energy limitations (muscle cramps, weakness):

Allied health problems (anorexia):

Risk for injury: (confusion, muscle tremors, etc.)

Nursing issuesFluid Volume Excess R/T inability to excrete water

Hyponatremia with plasma hypo-osmolality

Weight gain

Potential for InjuryInstitute seizure precautions and safety measuresReorient confused pt

Prevent complications of immobility

Recognize decreased gastric motility due to hyponatremia, combined with fluid restriction and decreased mobility - >constipation

Diabetes InsipidusPosterior Pituitary

Diabetes InsipidusUncommon syndrome of posterior pituitary hypofunction

S/SIncreased thirst - polydipsiaIncreased urination - polyruia

Results from ADH (Vasopression) deficiency, which prevents the kidneys from reabsorbing waterInability to conserve water

Posterior pituitary : DIDiabetes insipidus: to pass through

Decreased ADH = diuresis

Water is lost, so assess for:Kidneys produce large amts of dilute urine (5L-10L in 24hrs)low urine specific gravity (1.001-1.005)polyuria (>urine output), polydipsia (>thirst)fluid deficitweight loss, turgor,dehydration, hypotension, constipation, shock

Posterior Pituitary hyposecretionDiabetes InsipidusSymptoms-Thrist & polyuria 5 - 20L/day

SG < 1005 Urine osmol < 100 mmol/L

Se osmol > 295 mmol/kg

Nocturia

Weakness=> weight loss, hypotension, tachycardia, constipation, shock.

Sleep deprivation-due to interrupted by need to drink fluids & urinate

Urine specific gravity low (1.001-1.005)

Urine osmolality decreased (50-200 mOsm.kg)

Urine less concentrated than plasma

Plasma osmolality elevated (>295 mOsm/kg)

Hypernatremia in blood

Diabetes InsipidusEtilogyFamilial or idiopathic

Head injury

Neuorsurgery

Damage to the hypothalamic areas that produce ADHCauseLesion of hypothalmus interferes with ADH synthesis/transport/release

brain tumourpituitary/cranial surgery head trauma CNS infection vascular disease.

Diabetes InsipidusEtilogyDrug Related

Ethanol & Phenytoin (Classification: Antiarrhythmic, Anticonvulsant): Inhibit ADH secretion

Lithium (Classification: Antimanic) & Demeclocycline(Classification:anti-infective-Tetracycline): Inhibit ADH action in kidney

4 Types of Diabetes Insipidus1) Neurogenic -also known as central hypothalamic pituitaryneurohypophysealCaused by a deficiency of the Antidiuretic hormone, vasopressin

2) Nephrogenic-also known asVasopressin - resistantCaused by insensitivity of the kidneys to the effect of the antidiuretic hormone, vasopressin

3) Gestagenic-also known as GestestionalCaused by a deficiency of the antidiuretic hormone, vasopressin, that occurs only during pregnancy

4) Dipsogenic, a form of primary polydipsis

Caused by Abnormal thirst and theExcessive intake of water or other liquids

Diagnosis & RxDiabetes InsipidusDiagnosis D.I.History and examination

Water deprivation test (see next slide)

Vasopressin challenge test (see next slide)

24 hours urine

High sodium in blood

MRI of pituitary, hypothalmus and skull to see damaged areas

TreatmentIntravenous fluids Hypertonic saline IV-Extracellular solution to pull fluid from outside the cell to inside the cell

Vasopressin SC/IM/IV, nasal prep

Long term DDAVP (Desmopression) nasal prep. (analog ADH)

Diagnosis - Fluid Deprivation Test (To identify cause of polyuria)Baseline VS, then check hourly-allows RN to detect changes, esp postural hypotensin & tachycardia

Deprive pt of fluid-Observe for compliance with fluid restriction

Hourly- urinary output, specific gravity, & osmololity

Urine test results determine whether testing can proceed. Testing can proceed if urinary osmolality stabilized for 3 samples and 3% wt loss is noted

Dx- Vasopressin challenge Order for 5 Units of aqueous vasopressin scContinue hourly urinary measurements

Vasopressin triggers and ongoing assessment detects Changes in urinary specific gravity and osmolality

Specific gravity & osmolality decrease with primary and secondary diabetes insipidus

No response is seen with nephrogenic diabetes insipidue

Diabetes insipidus treatmentVasopressin (Pitressin) : is ADHClassification: Hormone (antidiuretic)Uses: Treatment of central diabetes insipidus sue to deficient antidiuretic hormone. Route/Dose: IM, sc, nasal sprayNsg Implications:replace fluid: saline and glucosemonitor I & Ocheck specific gravityobserve electrolytesMonitor adverse reactions-abdominal cramps, angina, MI

Diabetes insipidus treatmentDesmopressin (DDAVP)Classification: Hormone (andiuretic)Indication: Management of primary nocturnal eneuresis unresponsive to other treatment modalitiespo, sc, IV, IntranasalAction: An anologue of naturally occuring vasopressin (antiuretic hormone). Primary action is enhanced reabsorption of water in the kidneysTherapeutic Effects: Prevention of nocturnal enuresis. Maintenace of appropriate body water content in diabetes insipidus. Nsg Implication: Monitor urine & plasma osmolality & urine volume frequently. Assess pt for symptoms of dehydration (excessive thirst, dry skin & mucous membranes, tachycardia, poor skin turgor) Weigh pt daily & assess for edema

Observe for Water Intoxication with all agentsADH excess = water intoxication

water is reabsorbed, so assess forincreased blood volume, fluid retentionconcentrated urine, low urine outputdilutional hyponatremia (same Na, more H20)muscle cramps and weaknessanorexia, n/v, irritable, confused, disorient, seizure

Diabetes InsipidusFluid Volume Deficit R/T inability to conserve water

Thirst, dry mucous membranes

Decreased skin turgor

Hypotension, tachycardia

Hemoconcentration, plasma hyperosmolality, hypernatremia

Increased urine output

Dilute urine-monitor specific gravity

Nursing IssuesFluid and electrolyte imbalance: R/T >diuresis,monitor urine and plasma osmolaritymonitor specific gravity (usually will be low with >diuresis)monitor urine volume (usually will be high 5-10L in 24 hr)Therapy successful when urine output and specific gravity begin to return to normalmonitor s/s dehydration weight pt daily & assess for edema Fluid volume deficitNurse will monitor for hypotension, constipation, shock

Sleeping problems:R/T nocturia & increased thirstEducation: