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Electrolyte Imbalance and Acid-Base disorders Victor Politi, M.D., FACP, Medical Director, St. John’s University Dr. Andrew J. Bartilucci Center College of Pharmacy and Allied Health Professions, PA Program Importance of Homeostasis • Fluid and electrolyte and Acid- base balance are critical to health and well-being – Maintained by intake and output – Regulation by renal and pulmonary systems Imbalances Result From: • Illness • Altered fluid intake • Prolonged vomiting or diarrhea Distribution of Body Fluids • Water is the largest single component of the body – 60% of adult’s weight is water • Healthy people can regulate balance Composition of Body Fluids • Water • Electrolytes – Separates into ions when dissolved • Carries an electrical charge – Positive charge – CATIONS » Sodium, Potassium, Calcium – Negative charge – ANION » Bicarbonate, Chloride Fluid Intake • Regulated primarily by thirst mechanism – In the hypothalamus • Osmoreceptors monitor serum osmotic pressure – Hypothalamus stimulated when osmolarlity increases – Thirst mechanism stimulated » With decreased oral intake » Intake of hypertonic fluids » Loss of excess fluid » Stimulation of renin-angiotensisn-aldosterone mechanism » Potassium depletion » Psychological factors » Oropharyngeal dryness Fluid Intake (cont) • Average adult intake – 2200-2700 cc/day • Oral – 1100-1400 • Solid foods – 800-1000 • Oxidative metabolism – 300 – By-product of cellular metabolism of ingested foods Fluid Intake (cont) • Must be alert • Able to perceive mechanism • Able to respond to mechanism • **At risk for dehydration: – Elderly – Very young – Neurological disorders – Psychological disorders Fluid Output Regulation • Kidneys – Major regulatory organ • Receive about 180 liters of blood/day to filter • Produce 1200-1500 cc of urine • Skin – Regulated by sympathetic nervous system • Activates sweat glands – Sensible or insensible-500-600 cc/day » Directly related to stimulation of sweat glands • Respiration – Insensible • Increases with rate and depth of respirations, oxygen delivery – About 400 cc/day • Gastrointestinal tract – In stool – Average about 100-200 » GI disorders may increase or decrease it. Acid-Base Balance • pH measures amount of Hydrogen ion concentration – Greater the concentration, lower the pH • 7 is neutral; <7 acidic; >7 basic or alkaline – Needed to maintain cell membrane integrity and speed of cellular enzymatic actions – Normal range – 7.35-7.45 – Regulated by buffers Physiological Regulation • Lungs and Kidneys – Lungs adapt fast • Try to correct pH before biological buffers kick in – Hydrogen and carbon dioxide levels provide stimulus for respirations » Lungs alter depth and rate according to hydrogen concentration – With metabolic acidosis, respirations increase to exhale more carbon dioxide – Metabolic alkalosis, lungs retain carbon dioxide by decreasing respiraitons – Kidneys take from a few hours to several days • Reabsorb bicarbonate in case of acid excess; excrete it in cases of acid deficit Common Disturbances Electrolyte Balance • Sodium – Hypernatremia (Na > 145, sp gravity < 1.010) • Caused by excess water loss or overall sodium excess – Excess salt intake, hypertonic solutions, excess aldosterone, diabetes insipidus, increased s water loss, water deprivation – S&S: thirst, dry, flushed skin, dry, stick tongue and mucous membranes – Hyponatremia (Na < 135, sp gravity > 1.030) • Occurs with net loss of sodium or net water excess – Kidney disease with salt wasting, adrenal insufficiency, GI losses, increased sweating, diuretics, SIADH – S&S: personality change, postural hypotension, postural dizziness, abd cramping, n&v, diarrhea, tachycardia, convulsions and coma Common Disturbances Electrolyte Balance • Potassium – Hyperkalemia (K > 5.3; EKG irregularities-bradycardia, heart block, wide QRS pattern-cardiac arrest) • Primary cause: renal failure; major symptom: cardiac irregularity – Fluid volume deficit, massive cell damage, excess K+ given, adrenal insufficiency, acidosis, rapid infusion of stored blood, potassium-sparing diuretics – S&S: dysrhythmias, paresthesia – Hypokalemia (K < 3.5; EKG irregularities-ventricular) • Most common electrolyte imbalance; affects cardiac conduction and function. Most common cause: potassium wasting diuretics – Diarrhea, vomiting, alkalosis, excess aldosterone secretion, polyruia, extreme sweating, insulin to treat diabetic ketoacidosis – S&S: weakness, ventricular dysrhythmias, irregular pulse Common Disturbances Electrolyte Balance • Calcium – Hypercalcemia (Ca > 5; x-rays show calcium loss, cardiac irregularities) • Frequently symptom of underlying disease with excess bond resorption and release of calcium – Hyperparathyroidism, malignant neoplastic disease, Paget’s disease, Osteoporosis, prolonged immobization, acidosis – S&S: anorexia, nausea and vomiting, weakness, kidney stones – Hypocalcemia (Ca < 4.0, EKG abnormalities) • Seen in severe illness – Rapid blood transfusion with citrate, hypoalbuminemia, hypoparathyroidism, Vitamin D deficiency, Pancreatitis, Alkalosis – S&S: numbness and tingling, hyperactive reflexes, positive Trousseau’s sign (wrist), positive Chvostek’s sign (cheek), tetany, muscle cramps, pathological fracture Common Disturbances Electrolyte Balance • Chloride • Usually seen with acid-base imbalance – Hyperchloremia (Na >145, Bicarb <22) • Serum bicarbonate values fall or sodium rises – Hypochloremia (pH > 7.45) • Excess vomiting or N/G drainage; loop of thiazide diuretics because of sodium excretion – Leads to metabolic alkalosis due to reabsorption of bicarbonate to maintain electrical neutrality Acid Base Balance • Arterial blood gas is best measure – pH • Measures hydrogen ion concentration – 7.35-7.45 – PaCO2 • Measures carbon dioxide (pulmonary ventilation) – 35-45 < hyperventilation; > hypoventilation – PaO2 • Oxygen in arterial blood – 80-100 – Oxygen Saturation • How much hemoglobin is carrying oxygen – 95-99% – Base Excess • How much blood buffer is present – High – alkalosis Caused from: Antacids, rapid blood transfusion, IV bicarb – Low – acidosis Caused from: Diarrhea – Bicarbonate • Major renal component of acid-base balance – Excreted and reproduced by kidneys • 22-26; 20 times the level of carbonic acid : low is metabolic acidosis, high alkalosis Common Disturbances in Acid-Base Balance • Respiratory acidosis (pH <7.35; CO2> 45;) – Increased carbon dioxide, excess carbonic acid, increased hydrogen ion concentration • Causes: HYPOVENTILIATION – Atelectasis, pneumonia, cystic fibrosis, respiratory failure, airway obstruction, chest wall injury, overdose, paralysis of respiratory muscles, head injury, obesity – S&S: neurological changes and respiratory depression » Confusion, dizziness, lethargy, headache, ventricular dysrhythmias, warm flushed skin, muscular twitching Common Disturbances in Acid-Base Balance • Respiratory alkalosis (pH > 7.45; CO2 < 35;) – Decreased carbon dioxide, decreased hydrogen ions • Causes: hyperventilation – asthma, pneumonia, inappropriate ventilator settings, anxiety, hypermetabolic state, CNS disorder, salicylate overdose – S&S: dizziness, confusion, dysrhythmia, tachypnea, numbness and tingling, convulsions, coma Common Disturbances in Acid-Base Balance • Metabolic acidosis (pH < 7>35; Bicarb < 22) – Increased acid (hydrogen ions, decreased sodium bicarbonate • High Anion Gap (Sodium minus Chlorine + Bicarb) – Causes: starvation, diabetic ketoacidosis, renal failure, lactic acidosis, drug use (paraldehyde, aspirin) – S&S: tachypnea with deep respirations, headache, lethargy, anorexia, abdominal cramps Common Disturbances in Acid-Base Balance • Metabolic alkalosis – Loss of acid (hydrogen ions) or increase bicarbonate • Most common cause: vomiting and gastric secretions – Hypokalemia, hypercalcemia, excess aldosterone, use of drugs (steroids, bicarb, diuretics) – S&S: numbness and tingling, tetany, muscle cramps Assessing Blood Gases • 1st look at pH – Over 7.45 Alkalosis – Below 7.35 Acidosis • 2nd check CO2 – Should move in opposite direction as pH • if abnormal, respiratory cause • if normal, metabolic • 3rd evaluate bicarbonate – Should move in same direction as pH • If so, metabolic cause • if not, respiratory cause • 4th both CO2 and bicarbonate abnormal? – Which more closely corresponds to pH and deviates more from normal? • Shows likely cause, other is trying to compensate Hypercalcemia Hypercalcemia • Most common causes (90% of cases): – Malignancy associated hypercalcemia • Tumor production of PTH-related protein is the commonest paraneoplastic endocrine syndrome, accounting for most cases of hypocalcemia in inpatients – Primary hyperparathyroidism • Most common cause in ambulatory patients Hypercalcemia - symptoms • Symptoms • (usually occur if serum calcium is > 12mg/dl and tend to be more severe if hypercalcemia develops acutely) – Constipation – Polyuria – Heart • Ventricular extrasystoles and idioventricular rhythm – Neurologic symptoms • Stupor, coma, azotemia in severe cases Hypercalcemia - TX • Treatment – Ultimate goal – locate primary disease process & control – Treatment of hypercalcemia of malignancy • Bisphosponates – effective in 95% of cases – Emergency tx of choice • Saline & furosemide (prevent volume overload and enhances Ca2+ excretion) Hypocalcemia Hypocalcemia • Often mistaken as a neurological disorder • Most common cause – renal failure • Other causes: – Malabsorption – Vitamin D deficit – Alcoholism – Diuretic therapy – Endocrine disease Hypocalcemia - Symptoms • Hypocalcemia increase excitation of nerve and muscle cells, primarily affecting the neuromuscular and cardiovascular systems Hypocalcemia - Symptoms • Symptoms: – Muscle cramps and tetany – Laryngospasm w/stridor – Convulsions – Paresthesias of lips & extremities – Abdominal pain Hypocalcemia - Symptoms • Chvostek’s & Trousseau’s signs are usually readily elicited – Chvostek’s sign • Contraction of the facial muscle in response to tapping the facial nerve anterior to the ear – Trousseau’s sign • Carpal spasm occurring after occlusion of the brachial artery with a bp cuff for 3 minutes Hypocalcemia - Labs • ECG: – Prolonged QT interval • Serum calcium concentration: – < 9mg/dl • Serum magnesium – usually low • Serum phosphate level – usually elevated in hypoparathyroidism or end-stage renal failure – Suppressed in early stage renal failure or vitamin D deficiency Hypocalcemia - Tx • Severe, symptomatic hypocalcemia – 10-15 milligrams of calcium per kilogram of body weight, or 6-8 10-ml vials of 10% calcium gluconate (558-744mg of calcium) added to 1 liter of D5W and infused over 4-6hrs. Adjust infusion rate to maintain serum calcium level at 7-8.5mg/dL – In presence of tetany, arrhythmias or seizures • Calcium gluconate 10% (10-20 ml) IV over 10-15min Hypocalcemia - Tx • Asymptomatic Hypocalcemia – Oral calcium 1-2g and vitamin D preparations are used Hyperkalemia Hyperkalemia • Many cases associated with acidosis • Pseudohyperkalemia – result of lysis of red cells releasing potassium into the serum Hyperkalemia • Associated With: – HIV – diabetic ketoacidosis – Medications • Surgical Med - Aminocaproic acid • Ace Inhibitors • Trimethoprim • Immunosuppressive medications Hyperkalemia • Findings – Muscle weakness – Abdominal distention – Diarrhea – Rare finding – flaccid paralysis Hyperkalemia • Heart rate may be slow, V-Fib & cardiac arrest may occur • ECG changes include: – Peaked T waves, widening of QRS, biphasic QRS-T complexes • Note:nearly 50% of cases with serum levels 6.5meq/L or greater will not exhibit ECG changes Hyperkalemia - TX • Confirm elevated level of serum potassium (measure in plasma rather than serum) • Tx consists of witholding potassium and giving cation exchange resins by mouth or enema – Sodium polystyrene sulfonate 40-80g/d Hyperkalemia – Emergent TX • Indicated if cardiac toxicity or muscular paralysis present or if hyperkalemia severe > 6.5-7 meq/L – Calcium gluconate 10% 5-30ml IV – NaHCO3 44-88 meq (1-2 ampules) IV – Insulin 5-10 units, IV plus glucose 50% 25g,1 ampule, IV – Nebulized albuterol 10-20mg in 4 ml normal saline inhaled over 10 min Hyperkalemia – Nonemergent Tx • Loop diuretic (Furosemide) 40-160mg IV or orally w or w/o NaHCO3, 0.5-3 meq/kg daily • Sodium polystyrene sulfonate (Kayexalate) oral: 15-30g in 20% sorbitol (50-100mL) rectal: 50g in 20% sorbitol • Hemodialysis • Peritoneal Dialysis Hypokalemia Hypokalemia • Severe hypokalemia may induce dangerous arrhythmias or rhabdomyolysis • Self limited hypokalemia occurs in 50-60% of trauma patients (possibly related to enhanced release of epinephrine) • Hypokalemia in the presence of acidosis suggests profound potassium depletion and requires urgent tx Hypokalemia - Signs • Common findings – Muscular weakness – Muscle cramps – Fatigue – Constipation or ileus Hypokalemia - Labs • ECG • Decreased amplitude • T wave broadening • Prominent U waves • PVCs • Depressed ST segment Hypokalemia – Causes Several Causes of Hypokalemia – Decreased potassium intake – Potassium shift into the cell – Renal potassium loss • Primary hyperaldosteronism • Renovascular HTN • Cushing’s Syndrome • Bartter’s Syndrome • Metabolic acidosis – Extrarenal potassium loss • Vomiting, diarrhea, laxative abuse, • Zollinger-Ellison syndrome Hypokalemia- Tx • Mild to moderate deficiency – Oral potassium • 20 meq/L to prevent hypokalemia, • 40-100 meq/L over a period of days to weeks to treat hypokalemia and fully replete potassium stores Hypokalemia - TX • Moderate to severe – Peripheral IV should not exceed 40meq/L at rates up to 40 meq/L/h – Continuous ECG monitoring indicated – Check serum potassium q 3-6 hours – Correct magnesium deficiency Hyponatremia Hyponatremia • MILD HYPONATREMIA – plasma sodium levels under <135 mmol x L(-1). • SEVERE HYPONATREMIA – plasma sodium levels below < 130 mmol x L(-1) compromising health and performance. • CRITICAL HYPONATREMIA – plasma sodium levels below 120 mmol x L(-1) (may be fatal). Hyponatremia • Defined as serum sodium concentration less than 130 meq/L • Most common electrolyte abnormality observed in hospitalized patient population • Most cases of hyponatremia result from water imbalance not sodium imbalance. Hyponatremia • Initial approach is to determine serum osmolality • Normal (280-295 mosm/kg) • Low (< 280 mosm/kg) • High (> 295 mosm/kg) Hyponatremia • Measurement of urine sodium helps distinguish renal from non-renal causes – Urine sodium > 20 meq/L • consistent with renal salt wasting (diuretics, ACE inhibitors, mineralocorticoid deficiency, salt-losing nephropathy) – Urine sodium < 10meq/L or fractional excretion of sodium < 1% • implies sodium retention by kidney to compensate for extrarenal fluid loss (vomiting, diarrhea, sweating, third- spacing) Hyponatremia • Isotonic & Hypertonic hyponatremia can be ruled out by determining serum osmolality, blood lipids, and blood glucose • Osmolality = 2 (Na+ meq/L) + Glucose mg/dL + BUN mg/dL 18 2.8 Hypotonic hyponatremia Volume Status Hypervolemic Hypovolemic Euvolemic UNa+ < 10meq/L Edematous states Extrarenal salt loss 1. SIADH 1. CHF 1. Dehydration 2. Post-op hyponatremia 2. Liver Disease 2. Diarrhea 3. Hypothyroidism 3. Nephrotic syndrome (rare) 3. Vomiting 4. Psychogenic polydipsia 4. Advanced renal failure 5. Beer potomania 6. Idiosyncratic drug reaction UNa+> 20meq/L 7. Endurance exercise Renal salt loss 1. Diuretics 2. Ace inhibitors 3. Nephropathies 4. Mineralocorticoid deficiency 5. Cerebral sodium wasting syndrome Hyponatremia - Tx • Treatment of underlying condition • Water restriction • Diuretics • Hypertonic 3% saline – Dangerous in volume overloaded states, not routinely recommended – Emergency dialysis Hypernatremia Hypernatremia – Na > 145, sp gravity < 1.010 • An intact thirst mechanism usually prevents hypernatremia • Excess water loss can cause hypernatremia only when adequate water intake is not possible, as with unconscious patients • Rarely, excessive sodium intake may cause hypernatremia Hypernatremia - Symptoms • Typical Findings include; – orthostatic hypotension, oliguria • In severe cases: – hyperthermia, delirium, and coma Hypernatremia- TX • Treatment directed at correcting the cause of fluid loss and replacing water and as needed, electrolytes • If hypernatremia is corrected too rapidly, the osmotic imbalance may cause water to preferentially enter brain cells causing cerebral edema and potentially severe neurologic impairment Questions ?
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