Fluids and Electrolytes Disorders PDF

Fluids and Electrolytes Disorders  1.Water  The average water content of the human body varies 40-75% of total body weight  Water is the solvent for all processes in the human body  It transports nutrients to cells and removes waste products by way of urine ...

Fluids and Electrolytes Disorders  1.Water  The average water content of the human body varies 40-75% of total body weight  Water is the solvent for all processes in the human body  It transports nutrients to cells and removes waste products by way of urine  Water  Water is located in intracellular and extracellular compartments  Extracellular can be subdivided into plasma and interstitial cell fluids.  The concentrations of ions within cells and in plasma are maintained both by energy- consuming active transport processes and by diffusion processes.  Plasma Osmolality  Osmolality is defined as the number of particles in per kilogram of water  Plasma osmolality is maintained between 280 and 295 mOsm/Kg  Plasma osmolality can be measured by the freezing point depression or estimated by the following equation:  POSM= 2(Na)mmol/L+(glucose(mg/dL)/20)+(BUN(mg/dL)/3)  Plasma Osmolality  Osmolal gap is the difference between the measured osmolality and the calculated osmolality.  The osmolal gap indirectly indicates the presence of osmotically active substances other than sodium, urea, or glucose, such as ethanol, methanol, ethylene glycol, lactate or may results from artificial decrease in the serum sod secondary to severe hyperlipidemia or hyperprotinemia  Urine osmolality  Urine osmolality depends on the state of hydration  Urine osmolality is the best measure of urine concentration  ADH is the main determinant of urine concentration  Dehydrated…..small amount of concentrated urine  Clinical significant of osmolality 1. Water load: ⚫ As excess water intake (eg. In polydipsia) begins to lower plasma osmolality, both ADH (hormone secreted by the posterior pituitary gland and acts on the cells of the collecting ducts in the kidney) and thirst are suppressed, so water is not reabsorbed, causing a large volume of dilute urine to be excreted. ⚫ So, hypoosmolality and hyponatremia usually occur in patients with impaired renal excretion of water.  Clinical significant of osmolality 2. Water Deficit:  As deficit of water begins to increase plasma osmolality, both ADH secretion and thirst are activated.  Thirst is the major defense against hyperosmolality and hypernatremia.  Regulation of blood volume  Regulation of both sodium and water are inter- related in controlling blood volume  Blood volume is determined by the amount of water and Na ingested and lost (by urine or GI) 1. The renine-angiotensin-aldosterone system responds primarily to a decreased blood volume via enhancing Na retention which in turn enhance water retention. Therefore ACE inhibitors and Spiranolactone………….used in case of increased blood volume 2. ADH  2.Elyctolytes (Sodium)  Normal range of serum sodium (136-145mmol/L)  Sodium is the main cation in ECF  Regulation of plasma sodium depends on: 1. Intake of water in response to thirst as stimulated or suppressed by osmolality 2. Excretion of water, largely affected by ADH release in response to osmolality or blood volume 3. Blood volume status which affects sod excretion through aldosterone, angiotensin II and ANP.  Clinical applications (Sodium) 1. Hyponatremia:serum level less than 135mmol/L Euvolemic Hyponatremia Hypervolemic Hypovolemic Causes: 1. Increased sod. loss  Hypoadrenalism  Potassium deficiency  Diuretic use  Salt-losing nephropathy  Prolonged vomiting or diarrhea  burns  (Sodium- hyponatremia) 2. Increased water retention: (hypervolemic)  Renal failure (Acute or Chronic)  Nephrotic syndrome  Hepatic cirrhosis  Congestive heart failure 3. Water imbalance:  Excess water intake  SIADH  Clinical applications (Sodium)  Classification oh hyponatremia by osmolality: 1. With low osmolality:  Increased sodium loss  Increased water retention 2. With normal osmolality:  Increased nonsodium cations (lithium, severe hyperkalemia, hypermagnesemia, hypercalcemia), pseudohyponatremia 3. With high osmolality: (hyperglycemia, mannitol infusion) Clinical applications (Sodium)  Symptoms of hyponatremia: 1. Between 125-130…..GI symptoms 2. Below 125 …neuropsychiatric symptoms including: nausea, vomiting, headache, decreased level of consciousness, and (if severe) seizures and coma, respiratory arrest and death.…...  Hyponatremia (treatment)  Hypervolemic hyponatremia: 1. Water restriction 2. Sodium restriction and use of diuretic (with monitoring) 3. Correction of the underlying conditions (CHF, Cirrhosis….)  Hypovolemic hyponatremia: Water and Na administration  Acute hyponatremia  Acute hyponatremia may be treated with saline infusion and I.V Furosemide  Severe symptoms: 100 mL of 3% NaCl infused intravenously over 10 minutes × 3 as needed  Mild to moderate symptoms, in patients at low risk for herniation: 3% NaCl infused at 0.5–2 mL/kg/h Medications-induced hyponatremia many medications may precipitate  hyponatremia (eg, antipsychotics, antidepressants, antiepileptic drugs, diuretics Clinical applications (Sodium)  Hypernatremia:  Causes: 1. Excess water loss (MORE COMMON THAN Na increase):  Diabetes insipidus  Renal tubular disorders  Prolonged diarrhea 2. Decreased water intake 3. Increased intake or retention  Increase aldosterone  Sod. Bicarbonate excess Hypernatremia  Clinical applications (Sodium)  Hypernatremia related to urine osmolality: 1. Urine osmolality700  Loss of thirst  GI loss of fluids  Excess intake of sodium Treatment of Hypernatremia  Treatment (Fluid replacement)  Establish documented onset (acute, < 24 h; chronic, >24h)  In acute hypernatremia, correct the serum sodium at an initial rate of 2-3 mEq/L/h (for 2-3 h) (maximum total, 12 mEq/L/d).  Measure serum and urine electrolytes every 1-2 hours  Perform serial neurologic examinations and decrease the rate of correction with improvement in symptoms  Chronic hypernatremia with no or mild symptoms should be corrected at a rate not to exceed 0.5 mEq/L/h and a total of 8-10 mEq/d (eg, 160 mEq/L to 152 mEq/L in 24 h).  If a volume deficit and hypernatremia are present, intravascular volume should be restored with isotonic sodium chloride prior to free-water administration.  Once hypernatremia is corrected, efforts are directed at treating the underlying cause of the condition (hypokalemia and hypercalcemia as a cuse of diabetes insipidus + administration of ADH)  2. Potassium  Potassium is the major intracellular cation in the body  Functions of potassium in the body include regulation of neuromuscular excitability, contraction of the heart, ICF volume.  Normal range of serum pot.(3.4-5.0 mmol/L)  2. Potassium  The kidneys are important in the regulation of potassium balance, initially, the proximal tubules reabsorb nearly all the potassium  Then under the effect of aldosterone, additional pot. is secreted into the urine in exchange for sod. in the distal tubule and the collecting ducts.  2. Potassium (Clinical applications)  Hypokalemia:  GI loss: 1. Vomiting and diarrhea 2. Malabsorption 3. Large doses of laxatives  Renal loss: 1. Diuretics 2. Coffee and alcohol 3. Hypomagnesaemia 4. Acute leukemia  Cellular shift: 1. Alkalosis 2. Insulin overdose Medication-induced hypokalemia  Drugs that can cause hypokalemia include the following:  Diuretics (carbonic anhydrase inhibitors, loop diuretics, thiazide diuretics): Increased collecting duct permeability or increased gradient for potassium secretion can result in losses  Methylxanthines (theophylline, aminophylline, caffeine)  Verapamil (with overdose)  Quetiapine (particularly in overdose)  Ampicillin, carbenicillin, high-dose penicillins  Bicarbonate  Antifungal agents (amphotericin B, azoles, echinocandins) [16, 17]  Gentamicin  Cisplatin  Ephedrine (from Ephedra; banned in the United States, but available over the Internet)  Beta-agonist intoxication  Symptoms of hypokalemia K level less than 3 mmol/L… - weakness, fatigue - Muscle weakness, cramps or paralysis - Constipation - Hallucination, psychosis, depression Severe hypokalemia leads to bradycardia, muscle paralysis ---respiratory failure and arrhythmia  Treatment 1. Severe: K