FLUID AND ELECTROLYTE BALANCE.docx

FLUID AND ELECTROLYTE BALANCE.docx

• 1.
  FLUID AND ELECTROLYTEBALANCE ELECTROLYTES: ◦ These are also known as blood electrolytes. ◦ They includes Na+ , K+ , Ca2+ , Mg2+ , PO4, Cl- , and HCO3 - ◦ Electrolytes are anions or cation. Functions of the electrolytes: ◦ Maintenance of osmotic pressure and water distribution. ◦ Maintenance of the proper pH. ◦ Helps in nerve conduction. Regulation of the proper function of the heart and other muscle. Involvement in oxidation-reduction reactions. Cofactors for enzymes. ◦ Water constitutes approximately 60% of body weight in men and 55% in women. Approximately 2/3rd of body water is found in the intracellular fluid (ICF) and 1/3rd in the extracellular fluid (ECF). Of the ECF 80% is found within interstitial fluid and 20% within serum. Total body water is regulated by the renal action of Antidiuretic Hormone (ADH), Aldosterone, Atrial Natriuretic Peptide(ANP), and by thirst mechanism. ◦ Cell walls function as semipermeable membranes, with water movement from one compartment to the other being controlled by osmotic pressure WATER DEPLETION: ◦ Water depletion will occur if intake is inadequate or if there is excessive loss. Excessive loss of water through the kidney is unusual except in diabetes insipidus or overuse of diuretics. ◦ Patients with fever will lose water through the skin and ventilated patients will lose it through the lungs. Diarrhoea also causes water depletion.
• 2.
  ◦ Water lossis usually compensated by the thirst mechanism, but this may not occur in patients who are unconscious, have swallowing difficulties or are disabled. ◦ Severe water depletion may induce cerebral dehydration causing confusion, fits, coma and circulatory failure. ◦ The underlying cause for the water depletion should be identified and treated. ◦ Replacement water should be given orally, where possible, or by nasogastric tube, intravenously or subcutaneously with 5% dextrose in water or, in patients with associated sodium deficiency, isotonic saline is used. Hypotonic saline is sometimes used, where neurologic effects of hypertonicity are seen. WATER EXCESS: ◦ Water excess is usually associated with an impaired water excretion, that is caused by renal failure or the syndrome of inappropriate secretion of the antidiuretic hormone/arginine vasopressin (SIADH). ◦ This syndrome has several causes including chest infections and some tumours, particularly small cell carcinoma of the lung. ◦ Excess intake is rarely a cause of water excess since the healthy adult kidney can excrete water at a rate of up to 2 mL/min. ◦ Patients affected usually present with signs consistent with cerebral overhydration, although over several days, they may be asymptomatic. Hyponatremia is usually present. WATER AND ECF OSMOLALITY: ◦ If the body water content changes independent of the amount of solute, osmolality will be altered (the normal range is 282–295 mmol/kg of water). ◦ A loss of water from the ECF will increase its osmolality and result in the movement of water from the ICF to ECF. ◦ This increase in ECF osmolality will stimulate the hypothalamic thirst centers to promote a desire to drink while also stimulating the release of
• 3.
  vasopressin or ADH.ADH increases the permeability of the renal collecting ducts to water and promotes water reabsorption with consequent concentration of urine. ◦ If the osmolality of the ECF falls, there is no desire to drink and no secretion of ADH. Consequently, a dilute urine is produced which helps restore ECF osmolality to normal. SODIUM: Normal range: 135–145mmol/L. ◦ The body of an average 70 kg man contains approximately 3000 mmol of sodium. Most of this sodium is freely exchangeable and is extracellular. ◦ In contrast, the ICF concentration of sodium is only about 10 mmol/L. Each day approximately 1000 mmol of sodium is secreted into the gut and 25,000 mmol filtered by the kidney. The bulk of this is recovered by reabsorption from the gut and renal tubules. ◦ The principle role of Na is the regulation of serum osmolality as well as fluid and acid-base balance. ◦ The kidneys are the primary organs responsible for controlling body Na and water. HYPERNATRAEMIA: ◦ Hypernatraemia is an elevated sodium level in blood. ◦ It is defined as serum sodium concentration greater than 145mmol/L. Causes: ◦ Hypernatremia can result from water loss (most common) or sodium retention (rare). Causes of Water Loss: ◦ Inadequate intake of water: This is the most common cause of hypernatremia. Unable to take in water due to impaired thirst mechanism.
• 4.
  ◦ Renal loss:Inappropriate excretion of water, often in the urine, which can be due to medications like diuretics or lithium or due to diabetes insipidus. ◦ GI loss: osmotic diarrhea (induced by lactulose, malabsorption). ◦ Insensible losses: excessive sweating may be due to exercise or warm climate. ◦ Water loss into cells: seizure, severe exercise, rhabdomyolysis. Causes of Increased Sodium Retention: ◦ Intake of a hypertonic fluid: ingestion of large quantities of sodium, ingestion of sea water. ◦ Mineralocorticoid excess: such as Conn’s syndrome or Cushing’s Syndrome. ◦ Secondary hyperaldosteronism associated with, for example, congestive cardiac failure, nephrotic syndrome, hepatic cirrhosis with ascites, or renal artery stenosis. ◦ Other causes : ◦ Diarrhea ◦ Vomiting ◦ Inappropriate IV fluids ◦ Renal failure Diuretics Examples of drugs known to cause hypernatraemia: -Lithium and phenytoin -Adrenocorticotrophic hormone -Anabolic steroids -Androgens -Corticosteroids -Lactulose -Estrogens
• 5.
  -Oral contraceptives -Sodium bicarbonate -Demeclocycline Symptoms: -Lethargy -excessivethirst -fatigue -Weakness -Irritability -edema. -Seizures -Confusion -coma HYPONATREMIA: ◦ Hyponatremia is defined as a serum sodium concentration of less than 135mmol/L. ◦ Hyponatremia is classified in adults according to serum sodium concentration, as follows : ◦ Mild: 130-134 mmol/L ◦ Moderate: 125-129 mmol/L ◦ Profound or severe: < 125 mmol/L ◦ Hyponatremia can be classified according to effective osmolality, as follows: ◦ Hypertonic hyponatremia: (Serum osmolality : >290 mOsm/kg) ◦ Isotonic hyponatremia: (Serum osmolality : 275-290 mOsm/kg) ◦ Hypotonic hyponatremia – typically considered true hyponatremia. (Serum osmolality: <275 mOsm/kg) ◦ Hypotonic hyponatremia can be further subclassified according to volume status, as follows:
• 6.
  ◦ Hypervolemic hyponatremia:TBW increases greater than an increase in total body sodium. ◦ Euvolemic hyponatremia: TBW increase with stable total body sodium. ◦ Hypovolemic hyponatremia: TBW decreases more than a decrease in total body sodium. Causes: ◦ Syndrome of inappropriate anti-diuretic hormone (SIADH). ◦ Heart, kidney and liver problems. ◦ Chronic, severe vomiting or diarrhea. ◦ Hormonal changes. ◦ Drinking too much water. ◦ Intensive physical activities • Certain drugs also cause hyponatraemia: Examples of drugs known to cause hyponatraemia: ◦ Amitriptyline and other tricyclic antidepressants ◦ Amphotericin ◦ Angiotensin converting enzyme inhibitors ◦ Carbamazepine ◦ Cisplatin ◦ Clofibrate ◦ Cyclophosphamide ◦ Diuretics ◦ Heparin ◦ Lithium
• 7.
  ◦ Miconazole ◦ NSAIDs ◦Opiates ◦ Tolbutamide ◦ Vasopressin ◦ Vincristine Symptoms: -Nausea and vomiting -Headache -Confusion -Loss of energy, drowsiness and fatigue -Restlessness and irritability -Muscle weakness, spasms or cramps -Seizures -Coma POTASSIUM: Normal range: 3.4-5.0mmol/L. ◦ The total amount of potassium in the body is 3000 mmol. ◦ About 10% of the body potassium is bound in red blood cells (RBCs), bone and brain tissue and is not exchangeable. ◦ The remaining 90% of total body potassium is free and exchangeable, being pumped in and out by Na/K-ATPase pumps. ◦ The normal daily dietary intake of potassium is of the order of 60–200 mmol. ◦ Major role is regulation of muscle and nerve excitability. Other roles include control of intracellular volume, protein synthesis, enzymatic reaction, and carb metabolism. HYPOKALEMIA: Low levels of potassium in blood usually below 3.4mmol/L is known as Hypokalemia.
• 8.
  Causes: ◦ Insufficient consumptionof potassium: ◦ Anorexia nervosa, dental problems and dysphagia. ◦ Excessive loss of potassium: Vomiting, diarrhea and excessive perspiration. ◦ Alcoholism. ◦ Diabetic ketoacidosis ◦ Elevated insulin. ◦ Hypomagnesaemia ◦ Hypothermia ◦ Thyrotoxicosis Symptoms: ◦ The patient with moderate hypokalemia may be asymptomatic. ◦ Symptoms of severe hypokalemia include: ◦ Muscle weakness ◦ Hypotonia (weak muscle tone) ◦ Paralysis ◦ Depression, confusion ◦ Arrhythmias ◦ Fatigue ◦ Vomiting ◦ Constipation ◦ Hypertension ◦ Hyperglycemia
• 9.
  HYPERKALEMIA: ◦ Hyperkalemia isdefined as elevated level of potassium greater than 5.0mmol/L in blood. Causes: -AKI and chronic renal failure -Acidosis -Tumor lysis syndrome -Cirrhosis -Diabetic ketoacidosis , Renal tubular acidosis -High potassium diet, Intravenous potassium supplement -Malnutrition, fasting, exercise -Hypoparathyroidism, Addison’s disease -Blood transfusion. Drugs causing hyperkalemia: Angiotensin converting enzyme inhibitors ,Antineoplastic agents (cyclophosphamide, vincristine) ,Non-steroidal anti-inflammatory drugs ,β- adrenergic receptor blocking agents ,Cyclosporine, Digoxin (in acute overdose) Diuretics -potassium sparing (amiloride, triamterene, spironolactone), Heparin Isoniazid, Lithium ,Penicillins (potassium salt), Potassium supplements, Tetracycline. Symptoms: -Nausea, Vomiting, diarrhea -Malaise -Palpitations -Muscle weakness -Mild breathlessness CALCIUM: Normal range : Calcium(total): 2.12-2.60 mmol/L Calcium (ionised): 1.19-1.37 mmol/L
• 10.
  ◦ The bodyof an average man contains about 1 kg of calcium and 99% of this is bound within bone. ◦ Calcium is present in serum bound mainly to the albumin component of protein (46%), complexed with citrate and phosphate (7%), and as free ions (47%). Only the free ions of calcium are physiologically active. ◦ Calcium metabolism is regulated by 1,25- dihydroxycholecalciferol (vitamin D) and by parathyroid hormone (PTH). HYPERCALCEMIA: • Hypercalcemia is an elevated serum calcium levels. Causes: ◦ Primary hyperparathyroidism ◦ Multiple myeloma and carcinomas ◦ Thyrotoxicosis ◦ vitamins A and D intoxication ◦ acute renal failure , renal transplantation and acromegaly. ◦ Certain drugs like- Thiazide diuretics, lithium, tamoxifen and calcium supplements. ◦ Hypophosphatemia Symptoms: Fatigue Depression Confusion Anorexia Nausea Vomiting Constipation Pancreatitis Increased urination Insulin resistance
• 11.
  HYPOCALCEMIA: ◦ Hypocalcemia isdefined as low levels of calcium in blood. Causes: ◦ Severe malnutrition ◦ Hypoalbuminaemia ◦ Hypoparathyroidism ◦ Pancreatitis ◦ Those that cause vitamin D deficiency, for example, malabsorption, reduced exposure to sunlight, liver disease and renal disease. ◦ Certain drugs like-bisphosphonates, phenytoin, phenobarbital, aminoglycosides , phosphate enemas, calcitonin, cisplatin, mithramycin and furosemide. Symptoms: ◦ Tetany ◦ Paresthesias or Tingling ◦ Muscle spasms: Muscle twitching and cramping ◦ CNS symptoms: Anxiety, Hallucinations , Confusion ,Irritability. ◦ Cardiovascular symptoms: Bradycardia, Ventricular arrhythmias, Congestive heart failure. ◦ Pulmonary symptoms: Laryngeal or Bronchospasm. PHOSPHATE : Normal range: 0.80 – 1.44 mmol/L ◦ About 85% of body phosphate is in bone, 15% in ICF and only 0.1% in ECF. ◦ Its major function is in energy metabolism. Most phosphate ions are covalently bound to organic molecules such as lipids(phospholipids),
• 12.
  proteins, carbohydrates (DNA,RNA),andATP. Mineralization of bone and teeth. ◦ Serum phosphate levels are regulated by vitamin D and Parathyroid hormone (PTH). ◦ HYPERPHOSPHATAEMIA: ◦ Hyperphosphatemia is abnormally elevated level of phosphate in blood. Causes: ◦ Hypoparathyroidism, Chronic renal failure, Tumour lysis, severe haemolysis. Symptoms: ◦ Ectopic calcification, Secondary hyperparathyroidism, renal osteodystrophy, Azotemia. ◦ Anorexia, nausea, vomiting, muscular weakness, hyperactive reflexes, tetany, and tachycardia. HYPOPHOSPHATEMIA: ◦ Hypophosphatemia is low level of phosphate in blood. Causes: ◦ Refeeding syndrome. ◦ Respiratory alkalosis ◦ Alcohol abuse ◦ Malabsorption ◦ Hyperexcretion of phosphate in the urine (phosphaturia). Symptoms: ◦ General debility, anorexia, anaemia, muscle weakness and wasting and some bone pain and skeletal wasting. ◦ Confusion, delirium and coma
• 13.
  MAGNESIUM: Normal range: 0.7–1.00mmol/L ◦ Magnesium is an essential cation, found primarily in bone, muscle and soft tissue. ◦ About 1% of the total body content is in the ECF. ◦ As an important cofactor for numerous enzymes and ATP. ◦ It is critical in energy requiring metabolic processes, protein synthesis, membrane integrity, nervous tissue conduction, muscle contraction, hormone secretion. ◦ Regulates heart contractility, Relaxes skeletal and smooth muscle, Regulates blood pressure, Regulates calcium, and cleans the bowel. HYPERMAGNESEMIA: ◦ Hypermagnesemia is elevated level of magnesium in blood. Causes: ◦ Renal insufficiency and excess magnesium administration, such as magnesium containing laxatives, antacids. ◦ Hemolysis ◦ Diabetic ketoacidosis, adrenal insufficiency, hyperparathyroidism and lithium intoxication. Symptoms: ◦ Weakness ◦ Hypotension ◦ Vomiting, nausea ◦ Altered mental functioning. HYPOMAGNESAEMIA: ◦ Hypomagnesaemia is low level of magnesium in blood.
• 14.
  Causes: ◦ Excessive gastro-intestinallosses, renal losses, surgery, trauma, infection, malnutrition and sepsis. ◦ Alcoholism, Diuretic use. ◦ Antibiotics (i.e. aminoglycosides, amphotericin, pentamidine, gentamicin, tobramycin) ◦ Certain drugs like – Cisplatin, amphotericin B and ciclosporin ◦ Excess calcium, Increased levels of stress, Excess saturated fats, Excess coffee or tea intake, Insufficient water consumption, Excess salt, Excess sugar intake. Symptoms: ◦ Weakness ◦ Irritability ◦ Tetany, delirium ◦ Convulsions ◦ Confusion ◦ Anorexia ◦ Nausea, vomiting ◦ Paresthesia ◦ Cardiac arrhythmias. CHLORIDE: Normal range: 96-106 mmol/L. ◦ Most abundant anion in the ECF and is important in maintenance of acid- base balance. ◦ Its absorption is coupled with bicarbonate secretion. Hypochloremia is caused due to metabolic alkalosis or acidosis caused by
• 15.
  organic or otheracids, CRF, fasting, prolonged diarrhea or vomiting, and diuretic therapy. ◦ Hyperchloremia can be due to Na water retention, ARF, dehydration, excess Cl administration. CHLORIDE: Normal range: 96-106 mmol/L. ◦ Most abundant anion in the ECF and is important in maintenance of acid- base balance. ◦ Its absorption is coupled with bicarbonate secretion. Hypochloremia is caused due to metabolic alkalosis or acidosis caused by organic or other acids, CRF, fasting, prolonged diarrhea or vomiting, and diuretic therapy. ◦ Hyperchloremia can be due to Na water retention, ARF, dehydration, excess Cl administration.