Electrolyte Disturbaces - Hyponatremia and Hypernatremia

Electrolyte Imbalances

Dr Hussain Azhar

Nature’s Water Balance

Topic Outline

Important Electrolytes

• Sodium

• Potassium

• Calcium

• Acid Base Disturbances

We’ll Discuss:

• Main causes of excess and deficiency

• Clinical Features

• Management

Water and Electrolyte Balance

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Sodium

Hyponatremia

Sodium

N Engl J Med 2000; 342:1581-1589 May 25, 2000

Normally, the extracellular-fluid and intracellular-fluid compartments make up 40 percent and 60 percent of total body water, respectively

With the syndrome of inappropriate secretion of antidiuretic hormone, the volumes of extracellular fluid and intracellular fluid expand

Water retention can lead to hypotonic hyponatremia without the anticipated hypo-osmolality in patients who have accumulated ineffective osmoles, such as urea (ARF / CRF)

A shift of water from the intracellular-fluid compartment to the extracellular-fluid compartment, driven by solutes confined in the extracellular fluid, results in hypertonic (translocational) hyponatremia e.g. hyperglycemia

Sodium depletion (and secondary water retention) usually contracts the volume of extracellular fluid but expands the intracellular-fluid compartment e.g. diarrhea

Hypotonic hyponatremia in sodium-retentive states involves expansion of both compartments, but predominantly the extracellular-fluid compartment e.g. nephrotic syndrome

Hypotonic hyponatremia due to water retention in association with sodium gain and potassium loss e.g. CCF treated with diuretics)

Hyponatremia

UNa> 20FENa> 1%

Una < 20FENa< 1%

DIFFERENTIAL DIAGNOSIS OF HYPONATREMIA BASED ON CLINICAL ASSESSMENT OF EXTRACELLULAR FLUID VOLUME (ECFV)

Hyponatremia

• Clinical Features– Asymptomatic– Mild and chronic state:

• Headache, nausea, vomiting, muscle cramps, lethargy, restlessness, disorientation, and depressed reflexes

– Severe and rapidly developing state:• Seizures, coma, permanent brain damage,

respiratory arrest, brain-stem herniation, and death

Effects of Hyponatremia on the Brain and Adaptive Responses

N Engl J Med 2000; 342:1581-1589 May 25, 2000

Work up for Hyponatremia

Work up for Hyponatremia

• Plasma Osmolality• Volume Status ( if Hypotonic Hyponatremia)

• Urinary Osmolality

• Glucocorticoids and Thyroid levels

Treatment of Hyponatremia

1. Treatment of underlying cause

2. Correction of Hyponatremia• Asymptomatic : slow correction

• Symptomatic : rapid but controlled correction

(Maximum Rate of Correction: < 10 meq / L / day)

Formulas for Use in Managing Hyponatremia and Characteristics of Infusates

N Engl J Med 2000; 342:1581-1589 May 25, 2000

Practical Exercise

• A 58-year-old man with small-cell lung carcinoma presents with severe confusion and lethargy. Clinically, he is euvolemic, and he weighs 60 kg. The serum sodium concentration is 108 mmol per liter, the serum potassium concentration is 3.9 mmol per liter, serum osmolality is 220 mOsm per kilogram of water, the serum urea nitrogen concentration is 5 mg per deciliter , the serum creatinine concentration is 0.5 mg per deciliter and urine osmolality is 600 mOsm per kilogram of water

Answer

• Formula:

• The estimated volume of total body water is 36 liters (0.60 × 60)

• The retention of 1 liter of 3 percent sodium chloride is estimated to increase the serum sodium concentration by 10.9 mmol per liter ([513 – 108] ÷ [36 + 1]=10.9).

• The initial goal is to increase the serum sodium concentration by 5mmol per liter over the next 12 hours.

• Therefore, 0.46 liter of 3 percent sodium chloride (5 ÷ 10.9), or 38 ml per hour, is required.

Summary : Correction of Hyponatremia

Hypovolemic Hypotonic Hyponatremia

Euvolemic Hypotonic Hyponatremia

Hypervolemic Hypotonic Hyponatremia

1. Volume Replacement 1. Symptomatic:• 3% Saline +

furosemide

1. Water Restriction

2. Isotonic Saline 2. Diuretics and V2 antagonists

3. Half normal saline (after isotonic saline)

2. Asymptomatic • Water restriction• Isotonic saline• Demeclocycline• Fludrocortisone•Selective V2 antagonist

3. Hypertonic saline rarely

4. Dialysis

Osmotic Demyelination Syndrome

• The neurologic complications of chronic hyponatremia present in a stereotypical biphasic pattern that has been called the osmotic demyelination syndrome

• Patients initially improve neurologically with correction of hyponatremia, but then, 1 to several days later, new, progressive, and sometimes permanent neurologic deficits emerge e.g. quadriplegia, dysphagia, dysarthria etc.

• Most patients with the osmotic demyelination syndrome survive, and those with persistent deficits can be diagnosed with magnetic resonance imaging

SIADH: Euvolemic Hypotonic Hyponatremia

• Main causes:

1. CNS disorders: Trauma, Tumor, Hemorrhage, Stroke, Infections

2. Pulmonary Disorders: Infections, cancers, mechanical ventilation

3. Cancers: Lung, Pancreas, Prostate, Renal, Leukemia

4. Drugs: Antidepressants, Antipsychotics, Carbamazepine

5. Others: Pain, Stress, Postoperative, Pregnancy, Hypokalemia

Diagnosis of SIADH

1. Hyponatremia [Na] < 136 mEq / L

2. Decreased Serum Osmolality < 280 mOsm / kg

3. Increased Urine Osmolality > 150 mOsm / kg

4. Absence of cardiac, liver, renal disease

5. Normal Thyroid and Adrenal function6. Urinary sodium > 20 mEq / L

Treatment of SIADH

1. Treatment of underlying cause

2. Free water restriction

3. Hypertonic saline +/- furosemide

4. Demeclocycline or Lithium

5. V2 Vasopressin Receptor Antagonist: Conivaptan

Hypernatremia

Hypernatremia

Extracellular-Fluid and Intracellular-Fluid Compartments under Normal Conditions and during States of Hypernatremia.

Pure water loss reduces the size of each compartment proportionately e.g. Diabetes Insipidus

Hypertonic sodium gain results in an increase in extracellular fluid but a decrease in intracellular fluid e.g. hypertonic bicarbonate infusion

Hypotonic sodium loss causes a relatively larger loss of volume in the extracellular-fluid compartment than in the intracellular-fluid compartment e.g. vomiting

Normal Condition

Potassium loss in addition to hypotonic sodium loss further reduces the intracellular-fluid compartment e.g. osmotic diuresis

Effects of Hypernatremia on the Brain and Adaptive Responses

N Engl J Med 2000; 342:1493-1499 May 18, 2000

Clinical Features of Hypernatremia

• Common symptoms in infants include hyperpnea, muscle weakness, restlessness, a characteristic high-pitched cry, insomnia, lethargy, and even coma.

• Convulsions are typically absent

• Intense thirst may be present initially, but it dissipates as the disorder progresses

• The level of consciousness is correlated with the severity of the hypernatremia

•  Muscle weakness, confusion, and coma are sometimes manifestations of coexisting disorders rather than of the hypernatremia itself.

Formulas for Use in Managing Hypernatremia and Characteristics of Infusates

N Engl J Med 2000; 342:1493-1499 May 18, 2000

Causes of Hypernatremia

Causes of Hypernatremia

Hypovolemic Hypernatremia

Euvolemic Hypernatremia

Hypervolemic Hypernatremia

1. Extra Renal Losses 1. Cental Diabetes Insipidus

1. Hypertonic saline infusion

2. Renal Losses 2. Nephrogenic Diabetes Insipidus

2. Mineralocorticoid excess

Work up of Hypernatremia

• Urinary Osmolality

• Urinary Sodium

• Volume status

Work up of Hypernatremia

Treatment of Hypernatremia

Treatment of Hypernatremia

Hypovolemic Hypernatremia

Euvolemic Hypernatremia

Hypervolemic Hypernatremia

1. Extra Renal Losses 1. Cental Diabetes Insipidus

1. Hypertonic saline infusion

2. Renal Losses 2. Nephrogenic Diabetes Insipidus

2. Mineralocorticoid excess

1. Restore access to water2. Replace Volume3. Calculate and give Free Water Deficit

DesmopressinNa restriction + Thiazide

Dextrose water + furosemide*

*furosemide-induced diuresis is equivalent to one-half isotonic saline solution

Treatment of Hypernatremia

•  Managing the underlying cause may mean:– Stopping gastrointestinal fluid losses; – Controlling pyrexia, hyperglycemia, and

glucosuria;– Withholding lactulose and diuretics;– Treating hypercalcemia and hypokalemia; – Moderating lithium-induced polyuria; or – Correcting the feeding preparation

• A 76-year-old man presents with a severe obtundation, dry mucous membranes, decreased skin turgor, fever, tachypnea, and a blood pressure of 142/82 mm Hg without orthostatic changes. The serum sodium concentration is 168 mmol per liter, and the body weight is 68 kg.

Practical Exercise: Pure Water Loss

• The estimated volume of total body water is 34 liters (0.5 × 68).

• According to formula 1,

the retention of 1 liter of 5 percent dextrose will reduce the serum sodium concentration by 4.8 mmol per liter ([0–168] ÷ [34+1]= – 4.8).

• The goal of treatment is to reduce the serum sodium concentration by approximately 10 mmol per liter over a period of 24 hours. Therefore, 2.1 liters of the solution (10 ÷ 4.8) is required.

• With 1.5 liters added to compensate for average obligatory water losses over the 24-hour period, a total of 3.6 liters will be administered for the next 24 hours, or 150 ml per hour.

Answer

Nature’s Water and Electrolyte Balance