Introduction To Fluid & Electrolyte Management (2023) PDF

Introduction to Fluid & Electrolyte Management Tim Jackson Pharm D 2023 Hypotonic • Having lower osmotic pressure, lower amount of osmotic solutes Definitions - Tonicity Isotonic • Having equal osmotic pressure, almost always in comparison to human plasma Hypertonic • Having higher osmotic pres...

Introduction to Fluid & Electrolyte Management Tim Jackson Pharm D 2023 Hypotonic • Having lower osmotic pressure, lower amount of osmotic solutes Definitions - Tonicity Isotonic • Having equal osmotic pressure, almost always in comparison to human plasma Hypertonic • Having higher osmotic pressure, higher amount of osmotic solutes Sodium and Potassium Exchange • Na and K cannot cross the cell membrane without active transport • Na/K-ATPase pumps are responsible for high sodium EC and low EC potassium concentrations Image source: https://media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs10158-018-0221-7/MediaObjects/10158_2018_221_Fig1_HTML.png Fluid Homeostasis • • Blood Volume is largely determined by sodium balance ADH, Aldosterone, Angiotensin II released in response to decrease in fluid • Natriuretic peptide released in response to atrial distension (due to fluid overload) • Ultimately as sodium is the main solute in plasma, effective circulating volume (ECF) is largely dependent on sodium movement/homeostasis Review – Hormones Regulating Tubular Reabsorption Image source: Roosa KA. 2021. Engaging undergraduates in mechanisms of tubular reabsorption and secretion in the mammalian kidney. CourseSource. https://doi.org/10.24918/cs.2021.4 Fluid Status Assessment Volume Depletion Vs. Volume Overload From Fluid Balance Management Lecture, Eglis Tellez-Corrales, Pharm.D, MBKU • Sources of Unusual Fluid Loss • • • • Trauma • Hemorrhage directly reduces effective circulating volume (ECF) • Burns/wounds - damaged skin allows water and electrolytes to seep out of the body Medications – diuretics Liver / Renal dysfunctions GI • Vomiting, diarrhea, NG suction Drains, Fistulas Third-Spacing Fluid "Loss" • If fluids in circulation are "first space", fluids in the interstitium are "second space", then fluids not in either of those places or places where fluid should not accumulate, are in a "third" space • Fluids (and medications dissolved in those fluids) are no longer circulating and cannot easily return to where it should be without medical intervention • Causes • • • • • • Inflammation (causes blood vessels to become "leaky") Internal Bleeding CHF Ascites Peritonitis, Pancreatitis Post-op patients (fluid accumulation in surgical area) Patient Assessment: Fluid Loss Vs. Fluid Overload Fluid Loss • Dehydration • • • Loss of water from intracellular space Most dehydrated patients are also volume depleted Volume Depletion • Reduction in circulating volume and interstitial fluid • Fluid Overload Fluid overload • Edema, Anasarca • Increased interstitial volume Clinical Presentation of Volume Depletion • Physical Symptoms • • • • • Clammy hands, reduced skin turgor Orthostatic hypotension • For more severe fluid loss, blood pressure may only be able to be maintained while laying down Heart Rate > 120 BPM • HR increases to compensate for ↓ stroke volume Respirations > 30/min Mental status changes • Especially for older patients Lab Values and Fluid Loss – BUN:SCr ratio • Urea in the blood is filtered out in the glomerulus, but reabsorbed (reabsorption continues even as filtration declines) • Creatinine is filtered in the glomerulus and secreted in urine • In hypovolemia, BUN will rise but Creatinine may stay the same BUN:SCr is usually 10-20:1 • BUN:SCr > 20:1 may indicate volume depletion • BUN:SCr < 10:1 may indicate intrinsic renal problems Lab Values and Fluid Loss • Hematocrit – Falsely increased as with most fluid loss other than hemorrhage, you lose plasma, but not RBC's, so RBC's per unit volume of blood increases • Albumin is falsely elevated in a similar fashion • Organ dysfunction with continued fluid loss -> elevated LFT's, troponin • Illustration from Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013. Dehydration vs Volume Depletion Dehydration Volume Depletion • Loss of water from intracellular space • Loss of Na+ from intravascular and interstitial space • Common with poor access to water, elderly • • Labs: increased BUN:SCr ratio • Labs – Hypernatremia, increased plasma osmolality Frequently associated with • • Blood loss Vomiting, diarrhea, decreased PO intake Fluid Tonicity • Hypertonic • • Isotonic • • Osmolality > 375 mOsm/L Osmolality similar to human plasma 275290 mOsm/L Hypotonic • Osmolality < 250 mOsm/L Image source: “Osmotic pressure on blood cells diagram.svg” by LadyofHats is in the Public Domain ↵ Fluid Loss – Treatment with Crystalloids • • Most frequently used IV fluids • Inexpensive and readily available Fluid does not stay in the blood (only) • • 0.9% Sodium Chloride Normal Saline (NS) • • Appropriate treatment for hypovolemia Sodium (and water) will eventually diffuse into the tissues, but NS offers more intravascular volume expansion than D5W 5% Dextrose (D5w) • Dextrose rapidly metabolized by cells upon administration, water is free to diffuse into the tissues (less intravascular volume expansion than NS) • Ok for dehydration, maintenance fluids Dextrose 5% (D5w) • • Diffuses into both the intracellular and extracellular compartments of the body • Less useful in intravascular volume resuscitation than Normal Saline • Useful for uncomplicated dehydration Cheap, readily available isotonic fluid (250mOsm/L) • • Dextrose provides 3.4 calories per gram, rapidly metabolized by cells leaving free water Hyperosmolar Dextrose fluids are NOT used for maintenance fluids (used for hypoglycemia, TPN) 0.9% NaCl Normal Saline (NS) • Because of the action of the Na+/K+ ATPase pump, most of the sodium in NS will stay win the extracellular space • Expands intravascular volume better than D5W • • Osmolality near equivalent to serum Contains 154 mEq Na per Liter Hypotonic Saline Preparations • 0.45% Sodium Chloride (Half NS)occasionally used as IV fluid, more often used to compound medications • • Ex: 0.45% Sodium Chloride with 75 mEq Sodium Bicarbonate provides a nearly isotonic solution 0.22% Sodium Chloride (¼ NS) not carried by many institutions due to potential for errors • Available with D5W and KCl as a premix • • • • Adverse Effects of Sodium Chloride IV Fluids Fluid Overload • Recall sodium is able to diffuse into, tissues and intracellular fluid, drawing water with it Hypernatremia • Monitor Sodium Hyperchloremic Acidosis • Increasing Chloride concentration causes a progressive loss of bicarbonate • Hyperchloremia also interferes with bicarbonate labs Coagulopathy • Clotting factor density decreased • Image source: Bruno CM, Valenti M. Acid-base disorders in patients with chronic obstructive pulmonary disease: A pathophysiological review. J Biomed Biotechnol 2012 (2012). Dextrose and Saline Combinations • 5% Dextrose and 0.225% Sodium Chloride (D5W ¼ NS) • • ¼ NS should not be given without the dextrose component (too hypotonic) D5/NS combinations for maintenance IVF of dehydrated euvolemic patients • 5% Dextrose and 0.45% Sodium Chloride (D5W 1/2NS) • 5% Dextrose and 0.9% Sodium Chloride (D5NS) Sodium Chloride vs. Dextrose Solutions Sodium Chloride Solutions • Pros • • • Dextrose Solutions • Better at expanding extracellular volume Good at correcting hypovolemia Cons • • • Exacerbates edema, CHF Fluid, Sodium overload Possible dilutional coagulopathy • Pros • • Excellent maintenance fluid • Provides calories For dehydrated patients (replaces total body water not just intravascular space) Cons • Not to be used for hyperglycemic patients • • Fluid overload concerns Inefficient and increasing intravascular volume Lactated Ringers • Contains Sodium Chloride (130 mEq/L) and other electrolytes in concentrations to mimic plasma • • Contains calcium, potassium, lactate • Caution Commonly used in patients with diabetes, or post-op and L&D patients • Fluid overload, dilutional coagulopathy (standard fluid warnings) • • Hyperkalemia (4mEq/L potassium) Drug interactions • • Ceftriaxone [Rocephin] Piperacillin-tazobactam [Zosyn] Plasma-Lyte A • Balanced, buffered crystalloid solution • Intended to more closely mimic constituents of human plasma • Same issues as other crystalloids (volume overload/edema) • Expensive • Used in some specialty OR preparations • Del Nido cardioplegia solution Distribution of IV Fluids • ACCP Updates in Therapeutics 2022, Fluids, Electrolytes, and Nutrition, Leslie A. Hamilton PharmD Albumin 5% • Proteins are too large to cross capillary membrane • For volume expansion • • More efficient than NS at expending intravascular volume (4x) • Not first line therapy for hypovolemia, but causes less edema than high dose crystalloids Warnings • Infusion reactions, viral transmission, anaphylaxis (more common in IgA deficient) • Possible aluminum toxicity (renal patients)? • Albumin 25% Oncotic pressure 5x that of human plasma • • Should be avoided in patients requiring fluid resuscitation • • Causes fluid shift from interstitial to intravascular space Fluid shift out of IS space can be dehydrated, even if intravascular volume expands Useful for when redistribution of fluids is required (often paired with diuretic to then remove shifted fluid out of intravascular space and into the urine) • • Pleural effusions ascites HetaStarch • • Synthetic Starch • • Avoid with renal impairment Like albumin, starch molecules too large to leave intravascular space Avoid in patients with bleeding concerns • • Reduced Factor VII Platelet inactivation Hydroxyethyl starch was associated with a significant increased risk of mortality and acute kidney injury. Clinical use of hydroxyethyl starch for acute volume resuscitation is not warranted due to serious safety concerns General Chemistry Lab Reference Ranges Hyponatremia Treatment Considerations • Clinical Pearls • • Consider correcting hypokalemia first • As K is reduced, there is a net shift of Na into the cells to maintain electroneutrality • By replacing K, Na is shifted into the extracellular compartment Hyperglycemia • Extracellular shift of water in hyperglycemia causes a dilutional hyponatremia • Corrected sodium a better predictor of hyponatremia severity in hyperglycemic patients • 1.6 is the classic correction factor, 2.4 used by others Classification of Hyponatremia Hypovolemic Hyponatremia Description Euvolemic Hyponatremia Hypervolemic Hyponatremia Na and fluid both low, Normal Na, but too but more Na lost than much fluid water Unusual Fluid Loss, third SIADH, medications spacing Extra Na+ and fluid, but more extra fluid Diagnosis Urine Na < 25 mEq/L = nonrenal Na loss (GI). Urine Na > 40 mEq/L = renal loss of Na Urine Osmolality > 100 mOsm/L (impaired water excretion); urine Na > 20 mEq/L Urine Na < 25 mEq/L = edema (HF, cirrhosis, nephrotic syndrome. Urine Na > 25 mEq/L = acute/chronic renal failure Treatment Fluid resuscitation Address drug induced Na and water restriction, SIADH, fluid vaptans, diuretics restriction, vaptans Causes Heart failure, cirrhosis, nephrotic syndrome Hypovolemic Hyponatremia • Volume depletion stimulates ADH (vasopressin) secretion • Increases water reabsorption -> perpetuates hyponatremia • Treat with 0.9% Sodium Chloride to address hypovolemia • As volume improves and ADH secretion is reduced, serum Na will begin to rapidly correct itself • Careful monitoring to prevent overcorrection • Can result in permanent neurological damage Vaptans • ADH (vasopressin) receptor antagonists • Used for euvolemic or hypervolemic hyponatremia refractory to fluid restriction • Euvolemic – Syndrome of inappropriate antidiuretic hormone secretion (SIADH) - body makes too much ADH (vasopressin) • Increases electrolyte free water secretion • Hypervolemic – disorders with edema – CHF, cirrhosis • Reduces excess water weight in CHF Tolvaptan (Samsca) • Dosing • Euvolemic/hypervolemic Hyponatremia for maintenance of Na > 120 mEq/L in patients that cannot be maintained above 120 with initial therapy, or in patients with neurological symptoms • 15 mg PO daily while hospitalized • Titrate as needed after first 24 hours to 30mg daily, titrate daily to a maximum of 60mg daily • Clinical Pearls • • • Not for acute hyponatremia Monitor serum Na frequently Avoid fluid restriction during titration to avoid overcorrection Goal: 24 hour increase of 4-6 mEq/L rise in serum Na (maximum serum sodium increase: 8 mEq/L in any 24-hour period) • Conivaptan (Vaprisol) IV • • Dosing • Euvolemic/hypervolemic Hyponatremia • 20mg loading dose over 30 minutes, then continuous infusion of 20mg over 24 hours for 2-4 days (max dose 40mg QD, max duration 4 days) Clinical Pearls Goal: 24 hour increase of 4-6 mEq/L rise in serum Na (maximum serum sodium increase: 8 mEq/L in any 24-hour period) • Or increase 4-6 mEq/L in the first 6 hours for symptomatic patients Hypertonic Saline Preparations • • • For severe or symptomatic hyponatremia NEVER for IV Fluid High Alert medication • • Administration requires special monitoring • • Suggest technicians draw out ordered volume into an empty bag (prevent accidental over-administration) Suggest sodium level every 6 hours Other concentrations used for nebulization (7%) and compounding (23.4%) Hypertonic Saline Treatment goals • Quick but small and controlled rise in Na by 0.75-1.0 mEq/hr to a goal of 120 mEq/L • • • • • Consider 1-2 ml/kg/hr or 250 ml bolus over 30 minutes Treat until symptoms stop (about 120-125 mEq/L) Max change 10-12 mEq/L (… or 8, refer to institution specific guidelines) Overcorrection = central pontine myelinolysis or osmotic demyelination syndrome • • Then reduce increase to 0.5 mEq/L/hr Highest risk in chronic hyponatremia Not to be used for asymptomatic hyponatremia, or hyponatremia secondary to DKA or CHF Hypernatremia and Hypotonic Fluid • Patients with hypernatremia need water, not NaCl • Can NEVER give sterile water IV • Ideally water by mouth or by feeding tube would be best • Can give D5W if NPO • Resist orders to give any fluid with osmolarity < 150 mOsm/L • ¼ Normal Saline • Goal: Correct by no more than 10-12 mEq/L/Day • replace water deficit slowly, overcorrection potentially dangerous Treatment of Hypokalemia • Can't precisely calculate potassium deficit • Informal rule: give 10 mEq K for every 0.1 mEq K you want the serum K to rise • • • • • • K replacement should be guided by lab monitoring Consider initial dosing 20 mEq for moderate, 40 mEq for severe unless on telemetry or ICU setting Consider PO potassium for asymptomatic patients • GI upset – give with food and split doses > 40meq by 2+ hours when appropriate Potassium is NEVER EVER given IV Push • fatal at doses as low as 15 mEq, used in lethal injections Given IVPB Replace K at 10-20 mEq/hr • Faster rates require continuous EKG, ICU level care Hyperkalemia (K > 5.0-5.5 mEq/L) • • • Lab K values can be deceptive • Hemolyzed or coagulated samples will have artificially elevated K Mild/Moderate asymptomatic hyperkalemia • • Kayexalate Lokelma Severe hyperkalemia – symptomatic: muscle weakness, EKG changes [peaked t-waves, wide QRS) or K > 6.5 mEq/L • Urgent Treatment • • • • Insulin Calcium Sodium Bicarbonate Albuterol Sodium Polystyrene Sulfonate (Kayexalate) • Mechanism of Action: ion exchange resin--trades sodium for potassium in the intestine • • Dose • • • theoretical exchange capacity is 1 mEq potassium per 1 g 15 to 30 g PO once (max dose 60g) 30 to 50 g every 2 to 6 hour retention enema Risk of bowel necrosis when mixed with sorbitol • Usually reported with 70% sorbitol product • • Current product is 33% (rare risk of necrosis) Risk of sodium retention in renal failure Sodium Zirconium Cyclosilicate (Lokelma) • Mechanism of Action: exchanges potassium for hydrogen and sodium in the GI tract • Dose • • • Emergent: 10 g 3 times daily for up to 48 hours Chronic: Usual dosage range: 5 g once every other day to 15 g once daily Theoretically, similar risks of bowel necrosis as with Kayexalate • Avoid with GI motility disorders Severe Hyperkalemia Treatment • Calcium Gluconate 1-2gm IV – prevent arrhythmias associated with hyperkalemia • • Calcium chloride has 3x elemental calcium of calcium gluconate Extreme extravasation risk - avoid IVP calcium chloride except during code blue • • Calcium gluconate can easily be given 1-2gm in 50ml NS over 10 minutes as well Shift potassium into Cells • Insulin Regular 10 units IVP x1 (effect within 60 minute) • May give with 25-50gm dextrose IVP to prevent hypoglycemia (omit if hyperglycemic) • Predicted K reduction – 0.5-1.5 mEq/L Severe Hyperkalemia Treatment • Sodium Bicarbonate 50mEq IVP, may repeat after 30 min (effect within 30-60min) • • Disputed, least effective in patients with CKD, more effective with underlying metabolic acidosis Albuterol • 10-20mg nebulized over 10 minutes (effect within 30 minutes) • • • Predicted K reduction – 0.5-1.5 mEq/L Risk of tachycardia up to 40% of patients do not respond • Beta blockers Hypermagnesemia (Mg > 2.3 mg/dL) • Rare, usually only occurs with CKD • Signs/symptoms • N/V, bradycardia, hypotension, heart block • Symptoms rare until Mg > 4-5 mg/Dl • Treatment • Discontinue Mg containing medications • Asymptomatic – 0.9% Sodium Chloride IV fluids + loop diuretics • Symptomatic patients – 100-200mg elemental calcium IV over 5-10 minutes • Hemodialysis with CKD Hypomagnesemia (Mg < 1.7 mg/dL) • • • • Causes • Impaired intestinal absorption (GI disorders) • • Common with hospitalized patients Alcohol abuse Often occurs with hypokalemia/hypocalcemia Signs/symptoms - Arrhythmias, seizure, twitching, tetany, death Treatment • • Oral supplements (limited by diarrhea) Symptomatic patients • Magnesium sulfate IV 1-4gm given at 1gm / hr • Half of magnesium administered iv is excreted in urine • Reduce dose by 1/2 for renal insufficiency • Magnesium replacement may take 3-5 days Hypophosphatemia (PO4 < 2.5 mg/dL) • Causes • Increased renal elimination (drugs- diuretics, sodium bicarbonate) • • • • Refeeding syndrome Respiratory Alkalosis Treating DKA – phosphorous shifts into cells as acidosis is corrected Signs and Symptoms • • • Tissue hypoxia (decreased oxygen release in peripheral tissues) Mental status changes Pulmonary/cardiac symptoms – respiratory failure, arrhythmias Hypophosphatemia (PO4 < 2.5 mg/dL) • Prevention • Consider supplementing IV fluids with 10-30 mmol/L phosphorous for patients at risk • • Oral Phosphorous (K-Phos Neutral) used for asymptomatic patients, but poorly absorbed Treatment • Symptomatic patients or patients with PO4 < 1.9 • 0.5-0.75 mmol/kg of IBW • Frequently given in 15 or 30 mmol IVPB • Comes in 2 salt forms • Sodium Phosphate (4 mEq Na per 3 mmol of phosphate) • Potassium Phosphate (4.4 mEq K per 3 mmol of phosphate) • Hyperphosphatemia (PO4 > 4.5mg/dL) • Typically occurs in patients with CKD or hypoparathyroidism • Most patients are asymptomatic, but can have signs like EKG changes, parathesias, vascular calcifications • Controlled with phosphate binders / phosphate absorption inhibitors, diet changes, dialysis (covered in CKD) • • Symptoms include muscle spasms, anxiety, hypotension, hallucinations, seizures • Occurs in patients with CKD, hypoparathyroidism, Vit D deficiencies, hyperphosphatemia, patients receiving lots of blood products or undergoing CRRT • Conditions that cause an increase in Ca becoming albumin bound • Metabolic alkalosis causes lower ionized Ca levels • Need to calculate corrected calcium when albumin is low • Metabolic alkalosis causes lower ionized Ca levels Hypocalcemia ( < 8.5 mg/dL) Treatment of Disorders of Calcium Homeostasis • Treatment • • • Asymptomatic • hypocalcemia with hypoalbuminemia - Does not require treatment usually (get ionized calcium level) • Otherwise can be treated with oral supplements Symptomatic hypocalcemia • • 1 gram calcium chloride IVPB 2-3 grams calcium gluconate IVPB Hypercalcemia (Ca > 10.5 mg/dL) • Usually related to malignancy or hyperparathyroidism