1. Unit I – Problem 1 – Clinical Fluid & Electrolyte Disorders
Kingdom of Bahrain Arabian Gulf University College of Medicine and Medical Sciences
Unit I – Problem 1 – Clinical
Fluid & Electrolyte Disorders
Prepared by: Ali Jassim Alhashli
Based on: Kaplan Step 2 CK Internal Medicine

2. Fluid and Electrolyte Disorders
Hyponatremia:
Definition: it is a low sodium level >135 mEq. 90% of sodium is extracellular.
Etiology:
Increased free water retention.
Urinary loss of sodium.
Serium osmolality = (2 x sodium) + BUN/2.8 + glucose/18
When BUN and glucose are normal → you can use the following equation = (2 x sodium) + 10
Clinical presentation:
It varies from mild confusion and forgetfulness to seizures and coma. Notice that symptoms generally do not appear unless serum sodium level is > 125 mEq.
Symptoms depend mainly on how fast the level of sodium drops:
An acute drop in the level of sodium by points will result in seizures and coma.
While the drop of the same amount but very gradually will be sustained by the patient with no symptoms!
Treatment:
Mild hyponatremia (e.g. patient has no symptoms): fluid restriction.
Moderate hyponatremia: normal saline (0.9% NaCl) + loop diuretic (e.g. furosemide). Saline will provide sodium while the diretic will cause free water loss.
Severe hyponatremia (e.g. seizures or coma): 3% hypertonic saline and V2-receptor antagonists.
Notice that sodium level must no be corrected rapidly otherwise this will result in central pontine myelinolysis. Correct sodium level by 0.5 mEq/hour equal to a total of 12 mEq/24 hours.
Fluid and Electrolyte Disorders

3. Fluid and Electrolyte Disorders
Hyponatremia (continued):
Specific etiologies of hyponatremia:
Pseudohyponatremia:
Hyperglycemia: sodium level will drop 1.6 mEq/L for each 100 mg/dL increase in blood glucose above normal. When blood glucose level is increased this will cause shift of water outside the cell.
Hyperlipidemia: simply this a lab artifact.
Hypervolemia hyponatremia: this occurs in conditions in which there is increased free water retention due to secretion of ADH from posterior pituitary gland:
Congestive Heart Failure (CHF).
Nephrotic syndrome with low albumin level.
Liver cirrhosis.
Renal insufficiency.
Hypovolemic hyponatremia: this occurs when there is loss of sodium with body fluid loss and the patient replaces it with free water:
GI losses: vomiting and diarrhea.
Skin losses: burns and sweating.
Diuretics.
Adrenal insufficiency (Addison’s disease).
ACE inhibitors.
Euvolemic hyponatremia:
Psychogenic polydypsia: doesn’t occur unless patient drinks L of water.
Hypothyroidism.
Syndrome of Inaapropriate Secretion of ADH (SIADH).
Fluid and Electrolyte Disorders

4. Fluid and Electrolyte Disorders
Hyponatremia (continued):
SIADH:
Definition: increased secretion of ADH from posteror pituitary gland.
Etiology:
CNS disease: trauma, tumor, stroke or infection.
Pulmonary disease: pneumonia, TB, asthma or pulmonary embolism.
Neoplastic disease: lung cancer and cancers of pancreas, duodenum or thymus.
Medications: SSRIs, tricyclic antidepressants, haloperidole, vincristine and carabmazepine.
Diagnosis:
Decreased urine output.
Increased urine osmolality.
Increased urine sodium.
Increased ADH level.
Treatment:
Mild cases: fluid restriction.
Severe cases: hypertonic saline.
Hypernatremia:
Definition: it is increased serum sodium level (<145 mEq).
Loss of body fluids with no replacement with free water: sweating, burns and diarrhea.
Transcellular shift: rhabdomyolysis and seizure stimulate increased uptake of water by muscles resulting in hypernatremia.
Renal causes: central diabetes insipidus, nephrogenic diabetes insipidus, osmotic diuresis (DKA, non-ketotic hyperosmolar coma, mannitol, diuretics).
Clinical manifestations: mainly neurologic ranging from lethargy and weakness to seizures and coma.
Diagnosis: mainly aiming to differentiate between central and nephriogenic DI by water deprivation test.
Treatment: normal saline but keep attention NOT to correct sodium by < 12mEq/24 hours otherwise causing cerebral edema.
Central DI: vasopressin.
Nephrogenic DI: diuretics.
Fluid and Electrolyte Disorders

5. Fluid and Electrolyte Disorders

6. Fluid and Electrolyte Disorders

7. Fluid and Electrolyte Disorders
Hypokalemia:
Definition: it is low serum potassium level (>3.5 mEq). 95% of potassium is intracellular.
Etiology:
GI losses: vomiting and diarrhea.
Transcellular shift: alkalosis, increased level of insulin.
Urinary loss: diuretics, Conn syndrome (↑aldosterone), low magnesium (because normally magnesium decreases urinary loss of potassium).
Clinical manifestations:
Muscle weakness and when the condition is severe there might be paralysis.
Most serious complication being fatal arrhythmias.
Diagnosis:
Most important diagnostic test to be done is ECG to look for the presence of arrhythmia. Hypokalemia is associated with flattening of T-wave and presence of U-wave (a wave that occurs after the T-wave and represents purkinje fiber repolarization).
Treatment:
Potassium replacement by IV infusion (maximum of mEq/hour compared to 0.5 mEq/hour when replacing sodium in hyponatremia).
Notice that rapid replacement of potassium can result in fatal arrhythmias.
Hyperkalemia:
Definition: it is high serum potassium level (<5.5 mEq).
Transcellular shift: acidosis or insulin deficiency.
Increased intake (oral or IV) usually accompanied by impaired excretion.
Pseudohyperkalemia: hemolysis, mechanical trauma during venepuncture.
Rhabdomyolysis.
Decreased urinary excretion: ESRD, adrenal insufficiency and potassium-sparing diuretics (spironolactone and amiloride).
Clinical manifestations: most important being fatal arrythmias.
Diagnosis: ECG looking for peaked T-wave with short QT-interval.
Treatment: calcium gluconate/chloride, resonium, glucose+insulin infusion, sodium bicarbonate → if all of these fail to correct hyperkalemia → dialysis.
Fluid and Electrolyte Disorders

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10. Fluid and Electrolyte Disorders