Sodium Imbalance Lecture Notes PDF

Conditions of Sodium Imbalance Scot H. Simpson, BSP, PharmD, MSc Professor Pronouns: He, Him...

Conditions of Sodium Imbalance Scot H. Simpson, BSP, PharmD, MSc Professor Pronouns: He, Him ©2024, Scot H. Simpson Copyright-protected material contained herein is reproduced either with permission from the rights holder or under the terms of the Copyright Act. This material is being made available for your individual use; other use of this material has not been authorized and may require permission of the rights holder.  Lecture Objectives / Outline Sodium imbalances – Hyponatremia – Hypernatermia Describe the signs and symptoms of electrolyte abnormalities Describe management strategies for electrolyte abnormalities Related Readings (Pharmacotherapy 12th ed): – Chapter 68 (Disorders of Sodium and Water Homeostasis) 2  Recall from the previous lecture… Water Balance Total body water (TBW) represents 45-60% of total body weight Distribution into two (three?) compartments: H2 O 3 Source: www.peterloewen.com (Sodium & Water Assessment & Therapeutics)  Sodium (Na+) Homeostasis Daily sodium intake 1000-1500 mg (Adequate Intake) – About ½ a teaspoon of table salt 4  Mean Daily Sodium Intake (mg) of Canadians by Age Group and Sex Chart Title % Consuming excessive amounts of sodium 71 or older 24% 56% 51 to 70 31% 70% 45% 31 to 50 75% 45% 19 to 30 96% 50% 14 to 18 92% 63% 9 to 13 79% 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Female Male 5 Sources: Sodium Intake of Canadians in 2017. Health Canada. 2018 World Health Organization Global report on Sodium Intake Reduction. 2023  Percentage Contribution of Major Food Categories to the Mean Daily Sodium Intake of Canadians in 2017 Series 1 Bakery Products Mixed Dishes Processed Meat Products Cheese Soups Sauces & Condiments Fat, Oils, Spreads, and Dressings Snacks Fish & Seafood Products Breakfast Cereals Processed Vegetables & Veg. Juice Nut Butters 0% 5% 10% 15% 20% 25% 6 Source: Sodium Intake of Canadians in 2017. Health Canada. 2018.  Sodium (Na+) Homeostasis Daily sodium intake 1000-1500 mg (Adequate Intake) – About ½ a teaspoon of table salt Sodium is a primary driver of osmolality in the extracellular fluid compartment – Serum Osmolality = (2 x [Na+]) + [Glucose] + [Blood Urea Nitrogen] – Normal is 280-300 mOsm/kg Actively transported out of cells* – Via the Na+-K+-ATPase pump Kidneys are responsible for sodium excretion – Responsive to changes in serum sodium concentrations to maintain osmolality – Will conserve sodium if required 7 *Also involved in cell depolarization (nerves, muscles)  Sodium Concentration Normal serum sodium concentration – 135-145 mmol/L (mEq/L) Low sodium concentration (145 mmol/L) – Hypernatremia: always associated with hypertonicity and can cause significant reduction in intracellular fluid volume 8  Lecture Objectives / Outline Sodium imbalances – Hyponatremia – Hypernatermia Describe the signs and symptoms of electrolyte abnormalities Describe management strategies for electrolyte abnormalities Related Readings (Pharmacotherapy 12th ed): – Chapter 68 (Disorders of Sodium and Water Homeostasis) 9  Symptoms of Hyponatremia Mild / Chronic Moderate to Severe [Na+] 125-134 mmol/L [Na+] 160 mmol/L) Thirst mechanism (activated by release of vasopressin) is usually sufficient to resolve transient episodes of hypernatremia – Impairment in children, elderly, disabled Mild to Moderate: weakness, lethargy, restlessness, irritability, twitching, and confusion Severe: seizures, coma, and an increased risk of death 26  Classification of Hypernatremia Based on status of extracellular fluid volume Hypovolemic: water loss (renal, GI, lung, skin) ‘faster’ than sodium loss – sweating, diarrhea, vomiting, exposure to high temperatures – Usually thirst mechanism will correct this imbalance Hypervolemic: sodium overload (e.g., overcorrect hyponatremia using 3% NaCl, sodium bicarbonate, salt tablets) Euvolemic: water loss with little or no loss of sodium – Diabetes Insipidus is the most common cause 27  Causes of Diabetes Insipidus Daily urine volume > 3L Central (low levels of vasopressin) – Polyuria develops suddenly – Unreplaced water loss from skin & lung – Medical Conditions: Hypodipsia, TB, head trauma, CNS malignancy – Other: ethanol ingestion (transient) Nephrogenic (renal tubules do not respond to vasopressin) – Polyuria develops gradually – Medical Conditions: hypokalemia, hypercalcemia, kidney disease – Drug Induced: lithium, demeclocycline, amphotericin B 28  Lecture Objectives / Outline Sodium imbalances – Hyponatremia – Hypernatermia Describe the signs and symptoms of electrolyte abnormalities Describe management strategies for electrolyte abnormalities Related Readings (Pharmacotherapy 12th ed): – Chapter 68 (Disorders of Sodium and Water Homeostasis) 29  Patient Encounter The temperature is 30˚C and your neighbour has been up on their roof all day painting window trim. When your neighbour comes down the ladder, you notice that they stumble and look disoriented. Their shirt is soaked with sweat. Mentimeter 1. What is the most likely electrolyte abnormality? 2. Assuming your neighbour is hemodynamically stable, what is the most appropriate treatment? 30  Management of Hypovolemic Hypernatremia Hemodynamically stable: blood pressure is normal – Oral solutions should be sufficient to correct imbalance Hemodynamically unstable: blood pressure is low – Normal saline (0.9% NaCl) until hemodynamically stable Adults 200 to 300 mL/h Children 10 to 20 mL/kg/h – Once patient is hemodynamically stable, switch to half normal saline (0.45% NaCl), 5% dextrose (D5W), or other hypotonic solution 31  Management of Diabetes Insipidus Central: replace vasopressin – Desmopressin acetate: intranasally every 12-24h Nephrogenic: – Correct the underlying cause (e.g., hypercalcemia) – If drug-induced, stop or decrease dose (e.g., Li+) – Limit sodium intake and add a thiazide diuretic Creates a mild deficit in extracellular fluid volume, which can lower urine output by ↑water reabsorption in renal tubule 32  Management of Sodium Overload Administer D5W (5% Dextrose in Water) and a loop diuretic (e.g., furosemide) to facilitate sodium elimination – Measure sodium concentration every 2-4 hours until < 148 mmol/L and symptoms of hypertonicity have resolved 33  A few [Cl-]osing points… Chloride (Cl-) is a major extracellular anion – Passively follows Na+ – Normal concentration is 96-106 mmol/L Hypochloremia (106 mmol/L) – Associated with metabolic acidosis and hypernatremia 34  Reflecting on the Learning Objectives… Describe the signs and symptoms of electrolyte abnormalities – Hyponatremia – Hypernatremia Describe management strategies for electrolyte abnormalities – Hyponatremia – Hypernatremia 35