Electrolytes PDF

ELECTROLYTES Prepare Smarter, Practice Better Electrolytes Calcium  Calcium Total Body Calcium 22500 – 29900 mmol 99% is in the bones Extracellular space > Intracellular space Calcium Distribution 46% calcium is bound to proteins 80% albumin...

ELECTROLYTES Prepare Smarter, Practice Better Electrolytes Calcium  Calcium Total Body Calcium 22500 – 29900 mmol 99% is in the bones Extracellular space > Intracellular space Calcium Distribution 46% calcium is bound to proteins 80% albumin 20% globuins 10% → associated with acid anions like citrate and HCO₃ 24% - free ionized form  Serum Calcium Normal Range (Serum) Ionized 1.1 – 1.3 mmol/l  Functions of calcium Facilitate nerve conduction Membrane Muscle integrity contraction Regulator of ion Muscle transport relaxation Co-factor for hormonal Bone secretion in mineralization endocrine organs Calcium Homeostasis Approximately 500mg of calcium is removed from the bones daily and replaced by an equal amount. Normally the amount of calcium absorbed by the intestines is matched by the urinary calcium excretion. Parathyroid gland is very sensitive to ionized serum calcium changes.  Calcium-Sensing Receptor (CaSR) Calcium-sensing receptor (CaSR) 7 transmembrane receptor linked to G-protein with a large extracellular amino- terminal region. CaSR induced activation of phospholipase C and inhibition of PTH secretion. Decrease in calcium stimulates the chief cells of the parathyroid gland to secrete PTH. Calcium-Sensing Receptor (CaSR) cont… Loss of CaSR leads to familial hypocalciuric hypercalcemia. In renal failure CaSR agonists suppress the progression of hyperparathyroidism and parathyroid gland growth.  Serum Calcium Hyperventilation causes ↑ Alkalization ↑Calcium bond to Albumin ↓Free calcium: Paraesthesis Tetany Spasm of smooth muscle  PTH and Vitamin D PTH stimulates osteoclastic bone reabsorption and distal tubular calcium reabsorption and mediates 1,25- dihydroxyvitiamin D Vitamin D Stimulates intestinal absorption of calcium Regulates PTH release by chief cells and mediates PTH stimulated bone reabsorption.  Hypocalcemia Reduction in serum calcium can result from decrease in albumin secondary to liver disease, nephrotic syndrome or malnutrition. Hypocalcemia causes neuromuscular irritability and tetany. Alkalemia induces tetany due to decrease in ionized calcium. Causes of Hypocalcemia Chronic renal failure Acute renal failure Vitamin D deficiency Magnesium deficiency Acute pancreatitis Causes of Hypocalcemia cont… Hypoparathyroidism Pseuohypoparathyroidism Infusion of phosphate Infusion of citrate  Patient History Crohn’s disease Celiac disease Chronic pancreatitis Previous neck surgery Seizures- hypocalcemia secondary to anticonvulsants  Patient History cont… Alcoholism- Magnesium deficiency, Malabsorption, Chronic pancreatitis Family history Low calcium diet Lack of sun exposure Certain medications- calcimimetic agent, cinacalcet and anticonvulsants  Symptoms of Hypocalcemia Neuromuscular Numbness and tingling sensations in the perioral area or in the fingers and toes Muscle cramps in the back and lower extremities Wheezing from bronchospasm Dysphagia Voice changes due to laryngospasm  Symptoms of Hypocalcemia cont… Neurological Irritability, depression and personality changes Fatigue Seziures  Symptoms of Hypocalcemia cont… Skin Coarse hair, brittle nails, psoriasis, dry skin  Physical Examination Constitional: Confused, disoriented, dementia or overt psychosis Head: Coarse hair, Alopecia Eyes Subcapsular cataracts, papilledema Oral: Increased risk of dental caries, Enamel hypoplasia Respiratory: Inspiratory, expiratory wheezes  Physical Examination Cont… Cardiac: Signs of heart failure Neurologic: Chvostek sign, 10% of population. Tapping the skin over the facial nerve immediately in front of the external auditory meatus will cause an ipsilateral contraction of the facial nerve.  Physical examination cont… Trousseau sign- More specific than Chvostek sign  Hypoalbuminemia Low serum albumin levels can cause a reduction in serum calcium Each 1g/dL reduction in the serum albumin concentration will lower the total calcium concentration by approximately 0.8 mg/dL.  Hypoparathyroidism Neck irradiation Inadvertent surgical removal Infiltrative disease- Hemochromatosis, sarcoidosis, thalassemia, amyloidosis or metastaic malignant infiltration of the glands Late onset hypoparathyroidism- Ovarian failure, adrenal failure, pernicious anemia  Hereditary Hypoparathyroidism Hereditary hypoparathyroidism – familial or sporadic Familial forms include autosomal dominant and autosomal recessive as well as sex linked Hereditary Hypoparathyroidism cont… Sporadic DiGeorge form: syndrome  Kearns-Sayre syndrome (KSS) Kenny-Caffey syndrome is Kearns-sayre syndrome which associated with presents with heart block, retinitis Hypoparathyroidism pigmentosa and ophthalmoplegia. and includes medullary stenosis of the long bones and growth retardation.  Pseduohypoparathyroidism Pseduohypoparathyroidism end-organ resistance to the effects of PTH. PTH binds to the PTH receptor which in turn activates cyclic adenosine monophosphate (cAMP) through quinine nucleotide regulatory proteins (Gs).  Hypomagnesaemia Usual cause of hypomagnesaemia is due to loss through the kidney (e.g. osmotic diuresis, drugs) or the gastrointestinal tract (eg chronic diarrhea, severe pancreatitis , bypass or resection of small bowel). These patients present with low or inappropriately normal PTH levels in the presence of hypocalcemia. The mechanism of hypocalcemia includes resistance to PTH in the bone and kidneys, as well as a decrease in PTH secretion. Acute magnesium restoration rapidly corrects the PTH level, suggesting the hypomagnesaemia affects the release of PTH rather than its synthesis.  Vitamin D deficiency Ineffective PTH - Vitamin D is a necessary cofactor for the normal response to PTH and deficiency renders PTH ineffective Nutritional deficiency - can lead to an increased PTH and subsequent bone turnover Impaired absorption - Numerous conditions can impair the absorption of vitamin D. Small bowel disease such as celiac disease, gastric bypass, steatorrhea and pancreatic disease can lead to low vitamin D levels.  Vitamin D deficiency cont… Inheritable conditions - pseudovitamin D deficiency rickets or 1-alpha- hydroxylase deficiency. This condition is secondary to an autosomal mutation of the 1-hydroxylase gene. Ultimately, calcidiol is not hydroxylated to calcitriol and calcium. It is considered pseudovitamin D deficiency because high does of Vitamin D can overcome the clinical and biochemical findings of this disease.  Hepatic Disease Impaired 25-hydroxylation of Vitamin D, decreased bile salts with Malabsorption of vitamin D, decreased synthesis of vitamin D - binding protein, or other factors.  Renal Failure Chronic Kidney disease leads to a decrease in the conversion of 25-hydroxyvitamin D to its active from 1,25- dihydroxyvitamin D, particularly when the glomerular filtration rate (GFR) falls below 30 mL/min. This results in an increase in PTH.  Renal Failure cont… Increased absorption of phosphorus and calcium can lead to calcium-phosphorus mineral deposition in the soft tissues. Hypocalcemia can be seen due to the decrease in calcitriol production and a subsequent decrease in the intestinal absorption of calcium.  Critical Illness and Severe Sepsis In gram-negative sepsis, there is a reduction in total and ionized serum calcium. Elevated levels of cytokines ex: interleukin-6, interleukin-1, TNF-alpha.  Hungry Bone Syndrome Surgical correction of primary or secondary hyperparathyroidism may be associated with severe hypocalcemia due to a rapid increase in bone remodeling. Hypocalcemia results if the rate of skeletal mineralization exceeds the rate of osteoclast-mediated bone resorption.  Acute Pancreatitis It is caused primarily by precipitation of Insoluble calcium salts are present in calcium soaps in the When the pancreas is Pancreatitis can be damaged, free fatty the pancreas, and the associated with abdominal cavity, but glucagon-stimulated free fatty acids avidly Tetany and acids are generated chelate the salts, calcitonin release by the action of hypocalcemia. and decreased PTH resulting in calcium pancreatic lipase. deposition in the secretion may play a retroperitoneum. role. Magnesium  Magnesium Serum Composition: Store of 1000 mmol 32% bound to protein of which 50% is the 13% bound to citrate skeleton and phosphate 55% free ionized form Potassium  Potassium Total Body potassium of a 70kg adult is 3500 mmol (50 mmol/kg body weight). Potassium total body amounts decrease with age. It is the most important cation in the intracellular space.  Potassium cont… Normal Range (serum) 3.5 – 5.5 mmol/l Mean value (serum) 4.4 mmol/l Daily Requirements – 1 – 1.5 mmol/kg body weight per day Potassium Deficit Formula K deficit (mmol) = ( K normal – 4.4 mmol/l K measured ) x kg body weight x 0.4 Average dietary intake is 70 to 100 mEq of potassium K+ is excreted slowly by the kidneys over approximately 24 hour time frame Kidney → elimination of potassium 10mEq/24 hrs →Max 10mEq per kg body weight / 24 hrs  Factors that affect Serum Potassium Rhabdomylysis Hemolysis Breakdow Chemotherapy –Leukemia, Lymphoma Blood Transfusion n of Tissue GI hemorrhage with potassium absorption K+ in medication Potassium in IV fluids  Potassium Excretion Disorders ↑Delivery of sodium to the Diuretics or saline infusion collecting tubule increase increase delivery of potassium excretion by sodium to the collecting increasing the amount of tubule and cause sodium presented for increased potassium exchanges with Potassium excretion  Potassium Excretion Disorders cont… Alkalosis Metabolic Alkalosis →HC0₃-→carries sodium to the collecting tubule as an accompanying cation Increased delivery of sodium ↑Sodium / Potassium exchange and increases urinary potassium excretion Acidosis Acidosis inhibits potassium secretion  Potassium Excretion Disorders cont… Major factors Distal delivery of sodium and which tubular fluid influence Aldosterone potassium Presence of no absorbable anions secretion at in the tubular fluid perfusing this the cortical segment Alkolosis ↑ potassium secretion collecting duct  Factors that Effect Potassium Insulin – shifts K+ into cells pH - Acidosis →K+ shifts OUT of cells in exchange for excess Acidosis is associated with hyperkalemia H+, whereas alkolosis shifts K+ Alkalosis is associated with hypokalemia INTO cells in exchange for H+; Β2 Adrenengic → causes Potassium to shift into cells  Factors that Effect Potassium cont… Large pathologic ↑ osmolity can occur in severe hyperglycemia can cause shift of potassium into extracellular fluid compartment and raise plasma potassium concentration Mechanism - Water flows out of cells in response to increase in ECFV tonicity. ↑intracellular potassium concentration. Solvent drag whereby water carries potassium along with it through cell membrane  Extrarenal Potassium Loss The normal K+ concentration in sweat is 9mEq/L ; the average sweat Loss in sweat is volume is 200ml/24hr usually minimal Thus, 9mEq/L x.2L= 1.8 mEq of K+ is lost in sweat per day High Sweat Volume 10L/day; 9mEq/L x 10L = 90mEq/day Stool Losses of potassium →10% of Dietary Potassium Diarrhea →↑loss of potassium  Hypokalemia - Clinical Consequences Weakness Fatigue Neuromuscular Paralysis Respiratory Muscle Dysfunction Rhabdomyolysis  Hypokalemia - Clinical Consequences cont… GI Manifestations Constipation Ileus Nephrogenic Diabetes Insipidus ECG Changes U Wave T Wave Flattening ST segment changes Cardiac Arrhythmias  Hypokalemia - Clinical Consequences cont… Note: Hypotonic such as D5W, D5 0.45% Saline and 0.45% saline should not generally be used postoperatively or in the setting of volume depletion, because they deliver free water to a patient  Causes of Hypokalemia Marked Leukocytosis (WBC > 100,000) Insulin admin just prior to blood draw Redistribution Alkalemia (potassium shift Beta ₂ Androgenic activity agent Familial hypokalemic periodic paralysis into cells) Hypokalemic periodic paralysis with thyrotoxicosis Factor replacement in megaloblastic anemia  Causes of Hypokalemia cont… Urine potassium < 20mEq/ 24 hours Hypokalemia Diarrhea Laxative Abuse caused by Villous adenoma at colon external loss Sweat Loss Fasting/ Inadequate Intake  Causes of Hypokalemia cont… Vomiting / nasogastric →with tube Metabolic Diuretic Therapy Alkalosis Gitelman’s Syndrome Bartters Syndrome  Causes of Hypokalemia cont… →with no specific Osmotic diuresis Saline administration Acid Magnesium depletion Base Aminoglycoside Antibiotics Disorder Cisplatin  Causes of Hypokalemia cont… Alkalosis Potassium concentration decreases because potassium shifts into cells Serum potassium concentration falls by about 0.3 mEq for each 0.1 increase in pH  Causes of Hypokalemia cont… Increased Stimulation of Beta₂- Beta- Adrenergic receptors shifts potassium into cells by Andrenergic increasing the activity of activity sodium potassium ATPASE  Causes of Hypokalemia cont… Sympathetic Hyperresponsiveness Myocardial Infarction Delirium Tremens Major Head Trauma Asthma  Causes of Hypokalemia cont… Theophylline Toxicity Shift Potassium into cells Familial Hypokalemia →Autosomal Dominant  Causes of Hypokalemia cont… Periodic Paralysis Disorder is associated with recurrent episodes of flaccid paralysis that begin in childhood and are accompanied by hypokalemia. Serum potassium is often less than 3.0mEq/L during period of paralysis. Hypokalemic periodic paralysis Asian Heritage with thyrotoxicosis  Causes of Hypokalemia cont… Factor replacement therapy for severe megaloblastic anemia Rapid assimilation of potassium into RBC Falls occur approximately 2 days after beginning therapy for anemia  Diagnosis of Hypokalemia If 24 hour urinary potassium excretion 20 mEq/24 hours in presence of Hypokalemia implies renal potassium loss  Causes of Hypokalemia cont… Urine potassium < 20 mEq/24 hours Diarrhea →severe secretary Extrarenal Results in loss of K⁺ with HCO₃- resulting in hypokalemia and metabolic acidosis Potassium Villous Adenoma →rectosigmoid colon Chronic Laxative Abuse →severe potassium depletion and metabolic alkalosis Depletion Sweat→potassium concentration of roughly 9mEq/L→ athletic training or hard work in the hot sun may produce up to 12L/day of sweat Fasting or inadequate intake  Causes of Hypokalemia cont… Renal Potassium Depletion Urine Potassium > 20mEq/24 hours Renal hypokalemia with metabolic acidosis Renal tubular acidsosis Type I (distal) Renal tubular acidsosis Type II (proximal) Diabetic Ketoacidosis Carbonic anhydrase inhibitor therapy Ureterosigmoidostomy  Treatment of Hypokalemia Potassium Chloride – used in metabolic alkalosis Potassium Citrate Type I renal tubular acidosis Type II renal tubular acidosis Diarrhea (Citrate is converted to bicarbonate in the liver)  Treatment of Hypokalemia cont… 50mEq per kg of body weight In a 70kg Man; 70kg x 50 mg = 3500mEq total body potassium Potassium 98% intracellular compartment (70-100mEq) TBW =.6 x 70kg = 42L Content ⅓ x 42 = 14L Extracellular ⅔ x 42 = 28L Intracellular 14 x 4mEq/L = 56mEq Extracellular 28 x 100mEq/L = 2800mEq Total = 2856 mEq  Treatment of Hypokalemia cont… IV K⁺ administration is potentially dangerous →could have severe hyperkalemia Irritating to the veins Concentrations more than 30mEq/L and rates of administration more than 10mEq/hr are not generally recommended Need to have frequent potassium levels Treatment of Hypokalemia cont… Total amount of potassium normally contained in the body is Estimation of proportional to muscle, mass, and body weight Total Body Muscle mass declines Potassium with age generally and greater in men than women Potassium 1mEq/L decrease in Deficits potassium concentration reflects deficit of 150- 400 mEq in total body potassium Treatment of Hypokalemia cont… 150mEq→for a 1mEq/L decrease in potassium concentration might apply to an elderly woman with small muscle mass 400mEq→deficit for a 1 mEq/L decrease in potassium concentration might apply to a 20 year old-man with large muscle mass  Hyperkalemia Clinical manifestations potassium concentration >6.5 mEq/L Neuromuscular Weakness Ascending paralysis Respiratory failure  Hyperkalemia cont… ECG Changes Peaked T Waves Flattened P Waves Prolonged PR interval  Hyperkalemia cont… Hemolysis during blood drawing Excessive fist clenching with tourniquet during blood drawing Platelets > 1,000,000 Pseudohyperkalemia WBC > 200,000 Mononucleosis Familial pseudohyperkalemia range 6.0- 8.0mEq/L  Hyperkalemia cont… Redistribution (potassium shifts out of cell) Acidosis Hypertonic States Massive digitalis overdose Autosomal dominant hyperkalemia periodic paralysis  Hyperkalemia cont… Primary adrenal failure Aldosterone Autoimmune Deficiency/ TB unresponsiveness Hemorrhage Tumor Infiltration  Hyperkalemia cont… NSAIDS Aldosterone ACEI Deficiency/ ARB Unresponsiveness Heparin Cyclosporine  Hyperkalemia cont… Aldosterone Deficiency/ Unresponsiveness cont… Potassium-sparing diuretics Trimethoprim Pentamidine  Hyperkalemia cont… Acidosis –shift potassium out of cells in exchange for Hydrogen Ion Metabolic Acidosis Potassium will ↑ 0.7 mEq/L for every 0.1 decrease in pH Respiratory Acidosis Potassium will ↑0.7 mEq/L for every 0.1 decrease in pH Diagnosis Hyperkalemia ECG changes→Medical 100-200mEq of Emergency potassium Total Body Potassium Step I- STOP all to produce administration of hyperkalemia is not potassium (oral, large 5.0 to 6.0→only external, IV) requires Step IV- Send STAT Step II- Obtain STAT repeat potassium ECG Step III- Quickly seek possible hidden sources potassium  Treatment of Hyperkalemia Calcium Gluconate – 10ml→10% solution (1 gram) /HCO3 IV over 5-10 minutes Glucose D50 with 10iu regular insulin Temporarily translocates potassium into the cells Effect lasts 1 hour  Treatment of Hyperkalemia cont… Beta 2 Agonist Temporarily translocate k⁺ into cells Potentially dangerous in the setting of coronary artery disease Sodium zirconium cyclosilicate Hemodialysis Sodium  Sodium Major Extracellular Cation Major determinant of size of ECFV ↑ Na + → In ECF (Extracellular Fluid) → ↑ ECFV (Extracellular Fluid Compartment)  Sodium cont… ↑Na + in Congestive Heart Extracellular Failure Fluid Compartment Cirrhosis of Liver Examples Nephrotic Syndrome  Sodium cont… Total Sodium ↓-size of ECFV ↓ Poor Skin Turgor Tachycardia Orthostatic fall in blood pressure  Chart of IV Fluid Replacement Solution Glucose OSM Na⁺ Cl DSW 50 252 0 0 0.45% NaCl 0 154 77 77 0.9% NaCl 0 308 154 154 Ringers Lactate 0 272 130 109 3% NaCl 0 1026 513 513