Lesson 13 Fluid and Electrolytes PDF
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This document provides a detailed description of fluid and electrolytes. It discusses the key components, such as intracellular fluid (ICF), extracellular fluid (ECF), and total body water (TBW). It covers different conditions like hypernatremia, hypokalemia, and diabetes insipidus, and the treatment for each condition.
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- Males have more muscle mass so they have slightly more TBW content than women - ICF -55% of TBW - ECF -- 45% of TBW and subdivided into interstitial and intravascular/plasma - TBW decreases with age e.g. infants have higher, elderly have lower - Intravenous fluids - Cr...
- Males have more muscle mass so they have slightly more TBW content than women - ICF -55% of TBW - ECF -- 45% of TBW and subdivided into interstitial and intravascular/plasma - TBW decreases with age e.g. infants have higher, elderly have lower - Intravenous fluids - Crystalloids increase ECF volume by hydrostatic effect. Fluid does not stay in intravascular space long before diffusing across the semi-permeable membrane - Colloids increase have high oncotic pressure so they increase ECF by osmotic effect by pulling water into the intravascular space - Osmolality is the sum of the positively charged ions in the plasma - Sodium - Key functions = generation of action potentials, volume regulation and osmoregulation - Volume regulation = absolute sodium and water content by controlling extracellular volume - Effectors = RAAS, SNS, ADH, BNP, renal pressure - Osmoregulation = ratio of solutes (i.e. salt) to water to control extracellular osmolality - Effectors = thirst, ADH - Sodium absorption occurs in the distal small bowel and colon - Predominant cation in ECF - Changes to ECF volume are directly related to total body sodium content - Hypernatremia - Loss of water \> sodium - More commonly caused by decrease in circulating blood volume e.g. you lose water so you have a greater proportion of sodium to water - Pts can be hypovolemic, euvolemic, or hypervolemic - Hypovolemic hypernatremia seen in dehydration, diarrhea, osmotic diuresis - Euvolemic hypernatremia seen in DI - Hypervolemia can cause impaired gas exchange - Hypervolemic hypernatremia seen in Cushing syndrome and primary hyperaldosteronism - Diabetes insipidus - Most common cause of hypernatremia with normal total body sodium in conscious pt - Central DI caused by decrease in ADH secretion leading to increased amount of diluted urine - Nephrogenic DI caused by normal ADH secretion but impaired ability of kidney to respond - Congenital or due to kidney disease or the result of medications such as lithium or amphotericin B - Kidney fails to respond to exogenous ADH - Treatment of hypernatremia - Restore plasma osmolality to normal and correct underlying cause - Enteral free water preferred or D5W - Want to correct balance slowly because rapid correction can cause cerebral edema and demyelination syndromes - Do not change Na balance faster than 0.5mEq/L/hr - If decreased total body Na+, restore plasma volume before treatment with a hypotonic solution - If increased total body Na+, give loop diuretic and D5W - Mild hypernatremia is associated with increased perioperative morbidity, mortality, and hospital length of stay - Postpone elective surgeries if pt is hypernatremia \>150 or hyponatremia \ water - Caused by a defect in urinary diluting capacity - Hypoosmolality is nearly always associated with hyponatremia - Exception = pseudohyponatremia - Pseudohyponatremia = a non-sodium solute is holing water in the ECF so that creates a dilutional hyponatremia - Hypoosmolality with decreased total body sodium - Renal cause = diuretics, mineral corticoid deficiency, nephropathy - Extrarenal = vomiting, diarrhea, sweating - Hypoosmolality with normal total body sodium - Causes primary polydipsia, SIADH, hypothyroidism - Hypoosmolality with increased total body sodium - TBW and Na both increase but TBW increases more than Na - Edematous disorders i.e. kidneys can't excrete sodium properly - E.g. CHF, cirrhosis, nephrotic syndrome - Clinical manifestations of hyponatremia are primarily neurological due to increase in intracellular water - Serious manifestations of hyponatremia are seen with plasma concentrations of \3 - Hyperkalemia - Most life-threatening electrolyte abnormality - Rare in pts with normal renal function - Causes = acidosis, hyperkalemic periodic paralysis, succinylcholine administration, beta-blockers, conditions that cause a lot of cell lysis so K+ is released when cells die, ACE inhibitors, blood transfusions - Clinical manifestations = skeletal muscle weakness occurs when K+\>8 - EKG changes happen when K+ is \>7 e.g. peaked T waves, shortened QT, wide QRS, loss of p wave - Treat = diuretics, glucose and insulin, calcium salts to stabilize cardiac membrane, bicarbonate, beta-agonists, avoid LR - May potentiate effects of NMBDs - Correct K+ when its \>6 - Calcium - Role in muscle contraction - Absorption occurs in diet and is dependent on vitamin D - Regulated by PTH, vitamin D, and calcitonin - 50% of calcium is found in free ionized form, 40% bound to albumin, 10% combined with anions and amino acids - Plasma pH affects calcium protein binding. Acidosis = decreased ionized calcium - Hypercalcemia - Causes = hyperparathyroidism and malignancies account for 90% of causes; adrenal insufficiencies, thiazide diuretics, lithium - PTH increases serum Ca++ by increased uptake from bone, increased renal reabsorption, increased renal excretion of phosphate, activation of vitamin D - Calcium levels are indirectly proportional to phosphate - Calcium is magnesium antagonist - Signs and symptoms = weakness, EKG shortened ST and QT - Treat = NS and loop diuretic, bisphosphonates, calcitonin, hemodialysis, avoid acidosis which can worsen hypercalcemia - Hypercalcemia - Should be diagnosed on the basis of ionized calcium - Causes = hypoparathyroidism, pseudohypoparathyroidism, pancreatitis, rhabdomyolysis, fat embolism, chelation of calcium due to mass transfusions or albumin, tumor lysis syndrome, vitamin D deficiency - Symptoms = convulsion, tetany, paresthesias, trousseau's sign, Chvostek sign, prolonged ST and QT, decreased cardiac contractility, hypotension - Symptomatic hypocalcemia is a medical emergency! - Administer calcium with massive transfusions - Phosphorus - Second most abundant mineral in the body after calcium - Needed for maintenance and repair of tissues in cells, nerve conduction, and muscle contraction - PTH promotes phosphorus excretion - Absorption is increased with vitamin D - Hyperphosphatemia - Associated with all cause mortality - Promotes calcification in blood vessels so contributes to LVH, declined renal function, atherosclerosis - Causes = increased intake e.g. laxative abuse, decreased excretion e.g. CKD, hypoparathyroidism - Treatment = phosphate binding antacids - Hypophosphatemia - Associated with all cause mortality - Causes = severe burns, DKA, alcohol withdrawal, alkalosis, CHO ingestion, insulin - Treat = replace phosphate - Avoid hyperglycemia, respiratory alkalosis - IV phosphate with precipitate with calcium - Magnesium - Important cofactor in many of the enzymes in our body - Hypocalcemia, PTH, ECF depletion, metabolic alkalosis increase Mg reabsorption - Hypercalcemia, acute volume expansion, aldosterone, ketoacidosis, diuretics, alcohol ingestion, phosphate depletion increase Mg excretion - Hypermagnesemia - Most commonly seen in pts with CKD - Other causes = excess intake from laxatives or antacids - Symptoms = muscle weakness, vasodilation, bradycardia, myocardial depression, widening of QRS, hyporeflexia - Severe hypermagnesemia can lead to respiratory and cardiac arrest - Treatment = IV calcium, dialysis, diuresis - Reduce doses of NMDAs - Potentiates vasodilation and negative inotropic effects of anesthetics - Hypomagnesemia - Typically due to inadequate intake from diet or malabsorption syndromes, diuretics, hypothyroidism, chronic alcoholism, burns, pancreatitis, ciclosporins, aminoglycosides, long term PPI therapies - Symptoms = atrial fib, weakness, fasciculations, ataxia - Treat = replace magnesium - Consider other electrolyte disturbances e.g. hypokalemia, hypophosphatemia, hypocalcemia