Diabetes insipidus

Introduction

Diabetes insipidus (DI) is a condition which causes frequent urination. The reduction in production or release of ADH results in fluid and electrolyte imbalance caused by increased urinary output. Depending on the cause, Diabetes insipidus may be transient or life long condition. In its clinically significant forms, diabetes insipidus is a rare disease.

 

 

Definition

Diabetes insipidus (DI) is a group of conditions associated with a deficiency of secretion of anti-diuretic hormone characterized by the chronic excretion of abnormally large volumes (more than 50 mL/kg) of dilute urine.
 

Incidence

The true prevalence of DI is unknown, but it is usually underdiagnosed because the symptoms and signs are benign and many patients ignore them or are unaware of them. It commonly occur in older adults.
 

Types

• · Central (neurogenic) DI: it occurs when any lesion of the hypothalamus or posterior pituitary interferes with ADH synthesis, transport or release.
• · nephrogenic DI: it results from the decreased renal response to ADH despite presence of adequate ADH.
• · Primary polydipsia(dispogenic DI): excessive water intake caused by structural lesion in thirst center or psychologic disorder.
• · Gestational DI.
• Causes
• · Central (neurogenic) DI: Multiple causes include brain tumour, head injury, brain surgery, CNS infections.
• · nephrogenic DI: Caused by lithium therapy, renal damage, or hereditary renal disease.
• · Primary polydipsia(dispogenic DI): excessive water intake caused by structural lesion in thirst center or psychologic disorder.

Pathophysiology
The decrease in ADH results in fluid and electrolyte imbalances caused by increased urinary output and increased plasma osmolality. Tubular reabsorption of water reduces due to decreased tubular permiabilityto the water. This results in excessive urination which affects activities of daily living and interrupts sleep when nocturia occurs. Distended bladder leads to back flow of urine and hydronephrosis may develope as a complication. This will eventually leads to renal insufficiency.
Serum osmolality increases due to excessive urine output. Serum sodium level elevates in order to compensate for the fluid loss. severe thirst develops by osmoreceptor stimulation in response to the hypernatrmia. Patent intakes fluid to replace the loss. If hypernatremia persists restlessness, reduction in reflexes and seizures may develope. Cardiac output decreases and tachycardia develops if fluid volume is not restored. It will lead to hypotension and finally to hypovolemic shock.
 

Clinical manifestations

• Diabetes insipidus is characterized by increased thirst and increased urination. The primary character of DI is polyuria, excretion of large quantities of urine ( 5-20L per day)with a very low specific gravity(less than 1.005) and urine osmolality of < 100mmol/kg. In partial DI urine output may be lower(2-4L per day).
• Polydipsia (excessive intke of fluids) is also a characteristic feature of DI. Patient compensate for fluid loss by drinking great amount of water. The patient with central DI favours cold or iced drinks. Nocturia occurs due to frequent tendency to urinate which interrups sleep of the patient.
• Central DI usually occurs suddenly with excessive fluid loss. DI usually has a triphastic pattern: the acute phase with abrupt onset of polyuria, an interphase where urine volume apparently normalizes, and a third phase where DI is permanent.
• If fluid loss is not compensated, severe fluid volume de ficit results. This deficit is manifested by weight loss, hypotension, tachycardia with decreased cardiac output, poor tissue turgor, irritability, mental dullness. Hypovolemic shock may develop if fluid volume is not restored.

Diagnostic studies

• · Complete history collection regarding cause and origin of Diabetes Insipidus. Hourly intake and output should be recorded.
• · Physical examination: frequent monitoring of vital signs, body weight, skin turgor, level of consciousness are necessary.
• · Urine specific gravity less than 1.005 indicates Diabetes Insipidus.
• · Urine osmolality less than 100mmol/kg indicates Diabetes Insipidus..
• · Serum osmolality greater than 295mmol/kg indicates Diabetes Insipidus.

Water deprivation test:

Use to find cause of polyuria. All fluids are withheld for 8 to 16 hours. During the test patient’s blood pressure, weight and urine osmolality are assessed hourly. ADH is administered IV or subcutaneously and urine osmolality is measured one hour later. In central DI the rise in urine osmolality after vasopressin exceeds 9%. In nephrogenic DI there is no response to ADH.

Treatment

Goal: maintenance of fluid and electrolyte balance.

Pharmacological management.

• · Fluid replacement: hypotonic saline is administered intravenously.
• For central diabetes Insipidus-

Hormone replacement:

• Desmopressin acetate(DDAVP) can be administered orally,intravenously or as nasal spray.
• Aqueous vasopressin( pitressin)
• Vasopressin tenate
• Chlorpropamide( diabinese)
• Carbamazepine (tegretol)

For nephrogenic diabetes insipidus-

• Dietary measures: limiting sodium intake to less than 3 g per day help to reduce urine output.
• Thiazide diuretics: they are able to slow glomerular filtration rate and allows the kidney to reabsorb more water. E.g. hydrochlorothiazide (hydroDiuril), chlorothiazide (Diuril).
• Indomethacin (indocin).

 

Nursing diagnosis

1. Fluid volume deficit related to excessive urinary output as manifested by increased thirst and weight loss.
2. Sleeping pattern disturbances, insomnia related to nocturia as manifested by verbalization of patient about interrupted sleep
3. Activity intolerance related to fatigue and frequent urination as manifested by weakness and fatigue of the patient.
4. Anxiety related to course of disease and frequent urination as manifested by verbalization of anxious questions.
5. Ineffective coping related to frequent urination as manifested by verbalization of negative feeling by the patient.
6. Risk for complications related to excessive loss of fluid from the body as manifested by hypotension and weight loss.
7. Knowledge deficit regarding management of diabetes insipidus as manifested by verbalization of doubts by the patient.

Interventions

1. Fluid volume deficit related to excessive urinary output as manifested by increased thirst and weight loss.
Ø Assess the fluid level of the patient
Ø Monitor vital signs frequently
Ø Restrict oral fluid intake.
Ø Administer hypotonic saline intravenously.
Ø Administer medications if ordered.
 
2. Disturbed sleeping pattern, insomnia related to nocturia as manifested by verbalization of patient about interrupted sleep.
Ø Assess the sleeping pattern of the patient
Ø Give psychological support.
Ø Advice the patient to restrict oral fluids
Ø Provide calm and quiet environment.
 
3. Activity intolerance related to fatigue and frequent urination as manifested by fatigue and weakness of the patient.
Ø Assess the activity status of the patient
Ø Give psychological support to the patient.
 
4. Anxiety related to course of disease and frequent urination as manifested by verbalization of anxious questions.
Ø Assess the anxiety level of the patient.
Ø Explain the patient about the disease and treatment.
Ø Provide calm and quiet environment.
Ø Divert the attention of the patient by talking about different matter.
 
5. Ineffective coping related to frequent urination as manifested by verbalization of negative feeling by the patient.
Ø Assess the coping ability of the patient
Ø Explain the patient about the disease and treatment
Ø Give psychological support.
 
6.Risk for complications related to excessive loss of fluid from the body as manifested by hypotension and weight loss.
Ø Assess the fluid volume of the patient
Ø Monitor vital signs frequently.
Ø Take immediate measures to restore fluid volume such as IV fluid therapy
Ø Administer medications as ordered.
 
7. Knowledge deficit regarding management of diabetes insipidus as manifested by verbalization of doubts by the patient
Ø Assess the knowledge level of the patient.
Ø Explain the management of diabetes insipidus to the patient.
 
Summary
Diabetes insipidus cause frequent urination, even at night, which can disrupt sleep. Patient feels excessive thirst by the stimulation of osmoreceptor response. Because of the excretion of abnormally large volumes of dilute urine, patient may quickly become dehydrated if do not drink enough water. It can be treated with fluid replacement and hormone replacement therapy.

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