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
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 15-20 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
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 15-20 L of water. Hypothyroidism. Syndrome of Inaapropriate Secretion of ADH (SIADH). Fluid and Electrolyte Disorders
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
Fluid and Electrolyte Disorders
Fluid and Electrolyte Disorders
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 10-20 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
Fluid and Electrolyte Disorders
Fluid and Electrolyte Disorders
Fluid and Electrolyte Disorders