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Focus on PHARMACOLOGY ESSENTIALS FOR HEALTH PROFESSIONALS CHAPTER 24 Drugs Used to Treat Fluid and Electrolyte Balances Figure 24-1 The urinary system. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Kidney Structure • Inner medulla and outer cortex • Nephrons: functional units located in renal cortex – Renal corpuscle: filtering unit with glomerulus and glomerular capsule – Renal tubule: proximal convoluted tubule, loop of Henle, distal convoluted tubule Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Figure 24-2 The kidney with an expanded view of the nephron. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Renal Physiology • Urine production promotes homeostasis by regulating volume and composition of blood. • Three organic waste products: – Urea: most abundant waste – Creatinine: produced in skeletal muscle tissue – Uric acid: formed by recycling nitrogenous base from RNA molecules Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Diuresis in Elderly People • Older adults have: – Decreased ability to concentrate urine – Decreased ability to tolerate dehydration or water loads – Fewer nephrons – Reduce drug elimination – More drug accumulation in plasma, causing possible toxic reactions Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Urine Formation • Begins with filtration of plasma by glomerular capillaries (glomerular filtration) • Glomerular filtration produces 180 L of fluid each 24 hours. • Kidneys return filtered fluid to internal environment through tubular reabsorption. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Urine Formation • Waste products are excreted in urine. • Tubular secretion removes hydrogen ions and toxins faster than through filtration. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Figure 24-3 Sites of resorption and secretion in a nephron. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Homeostasis Glomerular filtration +Tubular secretion −Tubular reabsorption ____________________ Urinary excretion Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Fluid Imbalances in Children • The urine of infants and children is more dilute than that of adults because of: – Higher blood flow – Shorter loops of Henle Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Fluid Imbalances in Children • Pediatric patients are more affected by fluid imbalances resulting from: – Diarrhea – Infection – Improper feeding Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Fluid Imbalances in Children • Pediatric patients have limited ability to quickly regulate change in: – pH – Osmotic pressure Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Control of Urine Volume • Urine volume regulated by reabsorption of water: – By osmosis in proximal convoluted tubule and descending loop of Henle – Antidiuretic hormone (ADH) needed to increase water permeability of tubules. – Absence of ADH can cause diabetes insipidus. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Medications and Urine Retention • Several medications cause urine retention: – Anticholinergics and antispasmodics – Antidepressants and antipsychotics – Antihistamines – Antihypertensives – Beta-adrenergic blockers – Opioids Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Fluid and Electrolyte Balance • Levels of water and electrolytes in body are interdependent: – Electrolytes are dissolved in water of body fluids. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Figure 24-4 Electrolyte balance. Electrolyte intake occurs through the ingestion of foods and fluids through metabolic reactions. Electrolyte output occurs through the excretion of feces, sweat, and urine. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Dehydration in Infants • At birth, total body water (TBW) represents about 75 to 80% of total body weight. • Decreases to 67% during first year of life Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Dehydration in Infants • Infants are particularly susceptible to significant changes in TBW because of high metabolic rate and greater body surface area. • Dehydration may occur. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Water Deficit • Can indicate both sodium and water loss • Pure water deficits are rare. • Comatose or paralyzed patients have insensible water loss through the skin and lungs. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Water Balance • Water intake = water output • Water balance regulated by secretion of ADH and perception of thirst. • ADH is secreted when plasma osmolality increases or circulating blood volume decreases and blood pressure drops. • Increase plasma osmolality occurs with water deficit. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Fluctuating TBW in Elderly Patients • Decreased TBW in elderly patients results in part from increased body fat, decreased muscle, and the kidneys’ reduced ability to regulate sodium and water balance. • With stress or illness, this decreased TBW can become life threatening. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Table 24-1 Normal Water Gains and Losses* Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Electrolytes • Electrolytes: conduct electricity (cations) or are decomposed by electricity (anions) • Electrolytes of greatest importance: sodium, potassium, calcium, magnesium, chloride, sulfate, phosphate, bicarbonate, hydrogen Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Table 24-2 The Main Electrolytes in the Body Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Electrolyte Imbalances • Elderly people are at higher risk for fluid and electrolyte imbalance because of: – Decreased thirst sensation – Decreased ability of kidneys to concentrate urine – Decreased intracellular fluid and TBW Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Electrolyte Imbalances • Elderly people are at higher risk for fluid and electrolyte imbalance because of: – Decreased response to body hormones that regulate fluid and electrolytes – Increased use of diuretics – Decreased fluid and food intake Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Diuretics • Group of drugs that promote water loss from body into urine • Principal action at level of nephrons • Remove excess extracellular fluid into interstitial tissue which would otherwise result in edema • 5 classes: carbonic anhydrase inhibitors and osmotic, thiazide, loop, and potassium-sparing diuretics Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Table 24-3 Osmotic Diuretics Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Osmotic Diuretics: Uses • Primarily work by decreasing solute content resulting in less water reabsorption by loop of Henle and collecting duct and less sodium reabsorption in proximal tubule • Highly effective in cerebral edema Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Osmotics: Adverse Effects • Common adverse effects of osmotics include: – Headache – Tremor or convulsions – Dizziness – Hypotension or hypertension Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Osmotics: Adverse Effects • Common adverse effects of osmotics include: – Thrombophlebitis – Blurred vision – Dry mouth – Nausea and vomiting Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Osmotics: Contraindications • Osmotics are contraindicated in the following: – Anuria – Pulmonary congestion or edema – Severe congestive heart failure – Metabolic edema – Intracranial bleeding Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Osmotics: Contraindications • Osmotics are contraindicated in the following: – Shock – Severe dehydration – Pregnancy and lactation Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Osmotics: Patient Information • Advise patients to report thirst, muscle cramps or weakness, paresthesia, dyspnea, or headache. • Instruct female patients to avoid breastfeeding. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Table 24-4 Carbonic Anhydrase Inhibitors Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Carbonic Anhydrase Inhibitors: Uses • Work by converting carbon dioxide into bicarbonate ions • Used to treat absence, tonic-clonic, and focal seizures; to reduce intraocular pressure in glaucoma; to treat highaltitude sickness Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Carbonic Anhydrase Inhibitors: Adverse Effects • Common: anorexia, nausea and vomiting, weight loss, dry mouth, thirst, diarrhea, fatigue, dizziness, drowsiness, hyperglycemia • Serious: bone-marrow depression, hepatic dysfunction Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Carbonic Anhydrase Inhibitors: Contraindications • Contraindicated in renal and hepatic dysfunction, Addison’s disease and adrenocortical insufficiency, hyponatremia, hypokalemia, hypochloremic acidosis • Safety in pregnancy and lactation not established Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Carbonic Anhydrase Inhibitors: Contraindications • Use cautiously in diabetes mellitus, gout, obstructive pulmonary disease and respiratory acidosis, and in patients taking digitalis. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Carbonic Anhydrase Inhibitors: Patient Information • Instruct patients to avoid driving or hazardous activities if drowsiness or dizziness occurs. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Table 24-5 Thiazides and Thiazide-like Diuretics Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Thiazide Diuretics: Uses • Increase urinary excretion of sodium and water by inhibiting sodium reabsorption; also increase excretion of chloride, potassium, and bicarbonate ions • Used to treat hypertension and as adjunctive therapy in edema associated with heart failure and cirrhosis Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Thiazide Diuretics: Adverse Reactions • Common: anorexia, gastric irritation, nausea, vomiting, cramping, diarrhea, constipation, jaundice, hypokalemia, pancreatitis • Serious: anaphylactic reactions, respiratory distress Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Thiazide Diuretics: Contraindications • Contraindicated in patients with diabetes, history of gout, severe renal disease and impaired liver function, and in elderly patients • Not recommended during lactation • Interactions occur with corticosteroids, lithium, probenecid, antidiabetic agents Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Thiazide Diuretics: Patient Information • Instruct patients with diabetes to monitor blood glucose levels with care. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Table 24-6 Loop Diuretics Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Loop Diuretics: Uses • Act directly on loop of Henle to inhibit sodium and chloride reabsorption • Drugs of choice in acute pulmonary edema of heart failure • Also used to treat hypercalcemia and hypertension Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Loop Diuretics: Adverse Reactions • Common: fluid/electrolyte imbalances, skin rashes, photosensitivity, hypotension • Serious: circulatory collapse, thromboemboli, hepatic encephalopathy, ototoxicity, shock, cardiac arrhythmias, bone-marrow depression Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Loop Diuretics: Contraindications • Do not use in infants or lactating women. • Avoid in patients with severe diarrhea, dehydration, electrolyte imbalance, or hypotension. • Use cautiously in patients with hepatic cirrhosis, diabetes mellitus, pulmonary edema, pregnancy, and history of gout. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Loop Diuretics: Contraindications • Interact with NSAIDs, lithium, anticoagulants, aminoglycosides, and thiazide diuretics Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Loop Diuretics: Patient Information • Instruct patients to take in the morning and not at bedtime. • Advise women to avoid during lactation. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Table 24-7 Potassium-Sparing Diuretics Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Potassium-Sparing Diuretics: Uses • Prevent sodium reabsorption in distal tubule • Used to treat edema of heart failure, hepatic cirrhosis with ascites, nephrotic syndrome • Used mainly in combination with other drugs to treat hypertension Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Potassium-Sparing Diuretics: Adverse Effects • Common: kidney stones, gynecomastia • Serious: life-threatening hyperkalemia, renal failure Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Potassium-Sparing Diuretics: Contraindications • Contraindicated in patients with acute renal insufficiency, impaired renal function, or hyperkalemia • Use cautiously in pregnancy and lactation, or in patients with cirrhosis. • Interact with potassium supplements, NSAIDs, and lithium Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini Potassium-Sparing Diuretics: Patient Information • Teach patients about symptoms of hypokalemia, such as muscle cramps and weakness, lethargy, anorexia, irregular pulse, and confusion. • Advise patients of symptoms of hyperkalemia, including thirst, dry mouth, and drowsiness. Focus on Pharmacology: Essentials for Health Professionals, Second Edition Jahangir Moini