Fluid and Electrolyte Imbalance PDF

FLUID BODY COMPOSITION: FLUID AND ELECTROLYTE IMBALANCE DR MOHD ZAHIR AMIN BIN MOHD NAZRI EMERGENCY PHYSICIAN UMMC  The Composition of the Human Body 19/10/2009 2 Body fluid compartment Body Fluid Content Infants: 73% or more water (low b...

FLUID BODY COMPOSITION: FLUID AND ELECTROLYTE IMBALANCE DR MOHD ZAHIR AMIN BIN MOHD NAZRI EMERGENCY PHYSICIAN UMMC  The Composition of the Human Body 19/10/2009 2 Body fluid compartment Body Fluid Content Infants: 73% or more water (low body fat, low bone mass) Adult males: ~60% water Adult females: ~50% water (higher fat content, less skeletal muscle mass) Water content declines to ~45% in old age Fluid Compartments Total body water = 40 L (60% body wt) 1.Intracellular fluid (ICF) compartment: 2/3 or 25 L in cells 2.Extracellular fluid (ECF) compartment: 1/3 or 15 L Plasma: 3 L Interstitial fluid (IF): 12 L in spaces between cells Other ECF: lymph, CSF, humors of the eye, synovial fluid, serous fluid, and gastrointestinal secretions  Total body water Extracellular fluid (ECF) Volume = 40 L Volume = 15 L 60% body weight 20% body weight Intracellular fluid (ICF) Interstitial fluid (IF) Volume = 25 L Volume = 12 L 40% body weight 80% of ECF Interstitial fluid or tissue fluid is a solution that bathes and surrounds the tissue cells. The interstitial fluid is found in the interstices- the spaces between cells (also known as the tissue spaces) Composition of Body Fluids 1. Water: the universal solvent 2. Solutes: nonelectrolytes and electrolytes Nonelectrolytes: most are organic Do not dissociate in water: e.g., glucose, lipids, creatinine, and urea Composition of Body Fluids Electrolytes Dissociate into ions in water; e.g., inorganic salts, all acids and bases, and some proteins The most abundant (most numerous) solutes Have greater osmotic power than nonelectrolytes, so may contribute to fluid shifts Determine the chemical and physical reactions of fluids Electrolyte Concentration Osmolality = concentrations of solutes in fluid Expressed in moles per Liter (mmol/L) Also expressed in milliequivalents per liter (mEq/L), a measure of the number of electrical charges per liter of solution Calculated serum osmolality=2[Na]+glucose+urea (all mmol/L) Normal Se Osm : 285-295mOsm/kg Electrolyte Concentration For single charged ions (e.g. Na+), 1 mEq = 1 mOsm For bivalent ions (e.g. Ca2+), 1 mEq = 1/2 mOsm Extracellular and Intracellular Fluids Each fluid compartment has a distinctive pattern of electrolytes ECF All similar, except higher protein content of plasma Major cation: Na+ Major anion: Cl–, HCO3– ICF: Low Na+ and Cl– Major cation: K+ Major anion: HPO42–, protein Extracellular and Intracellular Fluids Proteins, phospholipids, cholesterol, and neutral fats make up the bulk of dissolved solutes 90% in plasma 60% in IF 97% in ICF  Blood plasma Interstitial fluid Intracellular fluid Na+ Sodium K+ Potassium Ca2+ Calcium Mg2+ Magnesium HCO3– Bicarbonate Cl– Chloride HPO42– Hydrogen phosphate SO42– Sulfate Figure 26.2 Distribution of electrolytes in the body CATIONS (mmol/l) ECF ICF Na 135-150 10-14 K 3.5-5.0 140-150 Ca 2.15-2.55 7-10 Mg 0.7-0.9 40 ANIONS (mmol/l) Cl 98-107 3-4 HCO3 22-26 7-10 Protein 1.2 4 HPO4 0.85-1.45 4 Fluid Imbalance Effective Circulating Volume Effective circulating volume is the part of the ECF that is effectively perfusing the tissues. Methods od assessing effective circulating volume: Clinical parameters: HR, BP, JVP Non invasive measurement of IVC diameter by US Invasive measurement of CVP or PCWP can be used for more critically ill pt Fluid Volume Deficit (Hypovolemia, Isotonic Dehydration) Common Causes Hemorrhage Vomiting Diarrhea Burns Diuretic therapy Fever Impaired thirst Clinical Manifestations Signs/Symptoms Weight loss Thirst Changes in pulse rate and BP Weak, rapid pulse Decreased urine output Dry mucous membranes Poor skin turgor Clinical examination: Skin pinch test falls back instantly - normal 2 - 4 sec - moderate 4 -6 sec - severe Capillary refill press finger on gums above an upper tooth if it takes longer than 2 seconds for blood to return - dehydration Treatment/Interventions (FVD) Fluid Management Mild to moderate dehydration. Correct with oral fluid replacement. Oral rehydration therapy – Solutions containing glucose and electrolytes. e.g., Pedialyte, Rehydralyte, ORS, IV therapy – Type of fluid ordered depends on the type of dehydration and the clients cardiovascular status. Fluid Volume Excess (FVE) Common Causes: Congestive Cardiac Failure (CCF) Early Renal Failure IV therapy Excessive sodium ingestion ADH Corticosteroid Clinical Manifestations Signs/Symptoms Increased BP Bounding pulse Venous distention Pulmonary edema Dyspnea Orthopnea (difficulty breathing when supine) Crackles Treatment/Interventions (FVE) Drug therapy Diuretics may be ordered if renal failure is not the cause. Restriction of sodium and saline intake Serum osmolality Normal se osmolality (Se Osm) = 285-295 mOsm/kg. calculated and measured se osm are within 10mOsm/kg of each other. An osmolar gap more than 10 mOsm/kg suggest of unmeasured osmotically active substances e.g. alcohol, acretoneand mannitol Calculated Se Osm (mOsm/kg) = 2 [Na+]+ glucose+ urea (all in mmol/L) Urine osmolality: average is about 500-800 mOsm/kg. Se Osm of 384 mOsm/kg produces stupor. Se Osm of >400 mOsm/kg may have grand mal seizures Se Osm of >420 mOsm/kg are fatal. Causes of increased/decreased osmolality Increased osmolality (Hyperosmolality) Decreased osmolality (hypoosmolality) Dehydration Sodium loss (diuretic use or low salt diet) Diabetes insipidus Hyponatraemia Hyperglycaemia Adrenocortical insufficiency Hypercalcaemia SIADH Hypernatraemia Excessive water ingestion/replacement Alcohol ingestion Electrolyte imbalance Hyponatremia ( 125 mmol/l) are usu asymptomatic – may have N&V Major symptoms occur when (Se Na < 125 mmol/l), esp when hypoNa occurs acutely Physical findings are of a neurological nature. Varying degrees of cognitive impairment to focal or generalized seizures. Hyponatremia ( 190mmol/L usu indicate long-term salt ingestion [Na] level > 170mmol/L usu indicate DI [Na] level > 150-170 mmol/L usu indicate dehydration Hypernatremia (>150mmol/L) Interventions/Treatment Drug therapy Euvolumia pt: Water repletion with hypotonic fluid 0.45%(HS) or D5%. Hypovolemia with tachycardia and hypotension (should receive fluid resuscitation): isotonic fluid 0.9% NS If inadequate renal excretion of sodium, will administer diuretics. Correction rate of Na level should be not more than 0.5 mmol/L/hr (complication: cerebral oedema) Diet therapy Mild – Ensure water intake, reduce salt intake. Potassium Most abundant cation of ICF, helps maintain ICF volume Key role in the resting membrane potential and action potential of neurons and muscle fibers K+ level is controlled by aldosterone Hydrogen-potassium exchange in cell membrane Minimal potassium intake: 1 mmol/kg Factors influencing K+ crossing the cell membranes Hypokalaemia (< 3.5 mmmol/l) Causes: Decrease intake of K Increase shifts of K into cells: alkalosis, drugs (insulin, β2- adrenergic agonists), hyperthyroidism Increased urine loss: diuretics, osmotic diuresis, hyperaldosteronisme Increased GI loss: diarrhoea, vomiting Sweat loss Hypokalaemia Se K < 3.5 mmmol/l Symptoms: Cardiac: flat t waves, ST depression, U wave, QT interval prolongation, arrhytmias Muscle paralysis, rhabdomyolysis Coma Metabolic alkalosis Hypokalaemia Se K < 3.5 mmol/l Management Mild hypoK (K >3.0mmol/L) Increased oral K intake (fruit, vegetables, dried fruits) Oral KCl supplement Moderate hypoK (K 5.0 mmmol/l) Causes Impaired excretion Renal failure, aldosterone deficiency, drugs (potassium sparing diuretics, ACE-inhibitors NSAID, cyclosporin) Increased K load IV potassium, potassium-riched food Increase shifts of K out of cells Tissue breakdown, acidosis, insulin deficiency Hyperkalaemia (Se K > 5.0 mmmol/l) Symptoms: Cardiac (peaked T waves, loss of P waves, heart blocks, ventricular arrhytmias, widening of QRS complexes, asystole) Paresthesias, weakness, paralysis Acidosis  Hyperkalaemia (Se K > 5.0 mmmol/l) Therapy Direct antagonism of hyperkalemic effect on cell membrane polarization (stabilization of membrane potential) IV Calcium gluconate 10% 10cc over 10min Movement of ECF K into ICF compartment Insulin (+glucose): IV D50% 50cc over 10min followed by IV actrapid 10u (separate boluses) Sodium bicarbonate: IV NaHCO3 1mEq/kg BW as a bolus of 5min β2-adrenergic agonists: Neb salbutamol 5mg: 3ml NS over 10min Removal K from the body Loop diuretics (Frusemide) Resonium A Dialysis Prevent further potassium increase Review all medications e.g. ACEI, B blocker, spironolactone & Review diet Calcium Regulated by the parathyroid gland Parathyroid hormone Helps with calcium retention and phosphate excretion through the kidneys Promotes calcium absorption in the intestines Helps mobilize calcium from the bone 63 3 organs that involved in calcium homeostasis 3 hormones that regulates serum calcium Parathyroid hormones Calcitonin Major stimulus – high calcium in plasma Major action – inhibit osteoclast bone resorption  reduce plasma calcium Vitamin D Promote mineralization of new bone Intestine  induce synthesis of calbindin D-28K Kidney  stimulates reabsorption of calcium and phosphate Stimulate osteoclast activity + bone resorption Hypocalcemia Se Ca < 2.0mmol/L Abnormalities of the parathyroid gland or inadequate intake or excessive losses Can cause skeletal and neuromuscular abnormalities Impairs clotting mechanisms Affects membrane permeability Diagnostic findings EKG changes – prolonged QT interval Calculated Ca = Ca (measured) + [(40 – albumin (g/L) x0.02] levels < 2.2mm;o/L Prolonged PT and PTT 68 Hypocalcemia Se Ca < 2.0mmol/L Cause: Surgically induced hypoparathyroidism Renal failure Vitamin D deficiency Inadequate exposure to ultraviolet light Acute pancreatitis hyperphosphatemia 69 Hypocalcemia Se Ca < 2.0mmol/L Signs and Symptoms Muscle cramps Hyperactive deep tendon reflexes Paresthesia of fingers, toes and face Tetany Seizures Positive Trousseau’s sign/Chvostek’s sign Laryngeal spasms Confusion Memory loss Cardiac dysrhythmias 70 Hypocalcemia Se Ca < 2.0mmol/L Therapy: Seizure precautions Administer IV Ca++ slowly for symptomatic patient (tetany and seizures), prolonged QT and corrected Ca calcium gluconate 90mg elemental Ca – but not recommended dt risk of tissue necrosis in event of extravasation Oral Calcium can be used for milder symptoms (paraesthesia) Assess nutritional intake of Ca++ 73 Hypercalcemia Sr Ca >3.0mmol/L Increased serum levels of Ca++ Symptoms are directly related to degree of elevation Pts with metastatic cancer are especially at risk Cause Excessive intake Excessive use of antacids with phosphate-binding Prolonged immobility Excessive vitamin D intake Thiazide diuretics Cancer Thyrotoxicosis 74 CAUSES Parathyroid hormone-mediated Parathyroid hormone-independent Primary hyperparathyroidism Hypercalcemia of malignancy (adenoma, carcinoma) Familial Vitamin D intoxication Secondary hyperparathyroidism (CKD, Chronic granulomatous disease vitamin D deficiency) (sarcoidosis, TB, leprosy, histoplasmosis) Tertiary hyperparathyroidism Medication (thiazide, lithium, theophylline toxicity) Endocrine cause (hyperthyroidism, acromegaly, phaeochromocytoma, adrenal insufficiency) Immobilization Parenteral nutrition Hypercalcemia Sr Ca >3.0mmol/L Signs and Symptoms Muscle weakness Personality changes Nausea and vomiting Extreme thirst Anorexia Constipation Polyuria Pathological fractures Calcifications in the skin and cornea Cardiac arrest 77 Hypercalcemia Sr Ca >3.0mmol/L Therapy: Stabilize and reduce calcium level Ensure adequate hydration Hydration with isotonic saline  through dilution Extracellular volume expand  inhibit proximal and loop reabsorption of sodium  reduce reabsorption of calcium  increase calcium clearance Rate of fluid depend on degree of hypercalcemia, severity of dehydration, ability of patient to tolerate hydration IV fluid initial rate 200-300ml/hr, maintain urine output 100-150ml/hr Drink plenty of fluids, 3-5 liters to help excrete excess Ca++ Increase urinary calcium excretion Loop diuretics – patient who are overloaded at presentation Biphophonate and calcitonin  prevent bone resorption by inhibit osteoclast Teach client to avoid dairy products Thank you