Fluid and Electrolytes: Balance and Distribution

Homeostasis State of equilibrium in body Naturally maintained by adaptive responses Body fluids and electrolytes are maintained within narrow limits

Water Content of the Body 60% of body weight in adult 45% to 55% in older adults 70% to 80% in infants Varies with gender, body mass, and age

Changes in Water Content with Age Fig. 17-1

Compartments Intracellular fluid (ICF) Extracellular fluid (ECF) Intravascular (plasma) Interstitial Transcellular

Fluid Compartments of the Body Fig. 17-2

Intracellular Fluid (ICF) Located within cells 42% of body weight

Extracellular Fluid (ECF) One third of body weight Between cells (interstitial fluid), lymph, plasma, and transcellular fluid

Transcellular Fluid Part of ECF Small but important Approximately 1 L

Transcellular Fluid Includes fluid in Cerebrospinal fluid Gastrointestinal tract Pleural spaces Synovial spaces Peritoneal fluid spaces

Electrolytes Substances whose molecules dissociate into ions (charged particles) when placed into water Cations: positively charged Anions: negatively charged

Measurement of Electrolytes International standard is millimoles per liter (mmol/L) U.S. uses milliequivalent (mEq) Ions combine mEq for mEq

Electrolyte Composition ICF Prevalent cation is K+ Prevalent anion is PO43- ECF Prevalent cation is Na+ Prevalent anion is Cl-

Mechanisms Controlling Fluid and Electrolyte Movement Diffusion Facilitated diffusion Active transport Osmosis Hydrostatic pressure Oncotic pressure

Diffusion Movement of molecules from high to low concentration Occurs in liquids, solids, and gases Membrane separating two areas must be permeable to diffusing substance Requires no energy

Diffusion Fig. 17-4 Copyright © 2007, 2004, 2000, Mosby, Inc., an affiliate of Elsevier Inc. All Rights Reserved.

Facilitated Diffusion Movement of molecules from high to low concentration without energy Uses specific carrier molecules to accelerate diffusion

Active Transport Process in which molecules move against concentration gradient Example: sodium–potassium pump External energy required

Sodium–Potassium Pump Fig. 17-5 Copyright © 2007, 2004, 2000, Mosby, Inc., an affiliate of Elsevier Inc. All Rights Reserved.

Osmosis Movement of water between two compartments by a membrane permeable to water but not to solute Moves from low solute to high solute concentration Requires no energy

Osmosis Fig. 17-6

Osmotic Pressure Amount of pressure required to stop osmotic flow of water Determined by concentration of solutes in solution

Hydrostatic Pressure Force within a fluid compartment Major force that pushes water out of vascular system at capillary level

Oncotic Pressure Osmotic pressure exerted by colloids in solution (colloidal osmotic pressure) Protein is major colloid

Fluid Movement in Capillaries Amount and direction of movement determined by Capillary hydrostatic pressure Plasma oncotic pressure Interstitial hydrostatic pressure Interstitial oncotic pressure

Fluid Shifts Plasma to interstitial fluid shift results in edema Elevation of hydrostatic pressure Decrease in plasma oncotic pressure Elevation of interstitial oncotic pressure

Fluid Shifts Interstitial fluid to plasma Fluid drawn into plasma space with increase in plasma osmotic or oncotic pressure Compression stockings decrease peripheral edema

Fluid Movement between ECF and ICF Water deficit (increased ECF) Associated with symptoms that result from cell shrinkage as water is pulled into vascular system

Fluid Movement between ECF and ICF Water excess (decreased ECF) Develops from gain or retention of excess water

Fluid Spacing First spacing Second spacing Normal distribution of fluid in ICF and ECF Second spacing Abnormal accumulation of interstitial fluid (edema)

Fluid Spacing Third spacing Fluid accumulation in part of body where it is not easily exchanged with ECF

Regulation of Water Balance Hypothalamic regulation Pituitary regulation Adrenal cortical regulation Renal regulation

Regulation of Water Balance Cardiac regulation Gastrointestinal regulation Insensible water loss

Hypothalamic Regulation Osmoreceptors in hypothalamus sense fluid deficit or increase Stimulates thirst and antidiuretic hormone (ADH) release Result in increased free water and decreased plasma osmolarity

Pituitary Regulation Under control of hypothalamus, posterior pituitary releases ADH Stress, nausea, nicotine, and morphine also stimulate ADH release

Adrenal Cortical Regulation Releases hormones to regulate water and electrolytes Glucocorticoids Cortisol Mineralocorticoids Aldosterone

Factors Affecting Aldosterone Secretion Fig. 17-9

Renal Regulation Primary organs for regulating fluid and electrolyte balance Adjusting urine volume Selective reabsorption of water and electrolytes Renal tubules are sites of action of ADH and aldosterone

Effects of Stress on F&E Balance Fig. 17-10

Cardiac Regulation Natriuretic peptides are antagonists to the RAAS Produced by cardiomyocytes in response to increased atrial pressure Suppress secretion of aldosterone, renin, and ADH to decrease blood volume and pressure

Gastrointestinal Regulation Oral intake accounts for most water Small amounts of water are eliminated by gastrointestinal tract in feces Diarrhea and vomiting can lead to significant fluid and electrolyte loss

Insensible Water Loss Invisible vaporization from lungs and skin to regulate body temperature Approximately 600 to 900 ml/day is lost No electrolytes are lost

Gerontologic Considerations Structural changes in kidneys decrease ability to conserve water Hormonal changes lead to decrease in ADH and ANP Loss of subcutaneous tissue leads to increased loss of moisture

Gerontologic Considerations Reduced thirst mechanism results in decreased fluid intake Nurse must assess for these changes and implement treatment accordingly

Fluid and Electrolyte Imbalances Common in most patients with illness Directly caused by illness or disease (burns or heart failure) Result of therapeutic measures (IV fluid replacement or diuretics)

Extracellular Fluid Volume Imbalances ECF volume deficit (hypovolemia) Abnormal loss of normal body fluids (diarrhea, fistula drainage, hemorrhage), inadequate intake, or plasma-to-interstitial fluid shift Treatment: replace water and electrolytes with balanced IV solutions

Extracellular Fluid Volume Imbalances Fluid volume excess (hypervolemia) Excessive intake of fluids, abnormal retention of fluids (CHF), or interstitial-to-plasma fluid shift Treatment: remove fluid without changing electrolyte composition or osmolality of ECF

Nursing Management Nursing Diagnoses Hypovolemia Deficient fluid volume Decreased cardiac output Potential complication: hypovolemic shock

Nursing Management Nursing Diagnoses Hypervolemia Excess fluid volume Ineffective airway clearance Risk for impaired skin integrity Disturbed body image Potential complications: pulmonary edema, ascites

Nursing Management Nursing Implementation Monitor cardiovascular changes Assess respiratory status and monitor changes Daily weights Skin assessment

Nursing Management Nursing Implementation Neurologic function LOC PERLA Voluntary movement of extremities Muscle strength Reflexes

Electrolyte Disorders Signs and Symptoms Excess Deficit Sodium (Na) Hypernatremia Thirst CNS deterioration Increased interstitial fluid Hyponatremia Potassium (K) Hyperkalemia Ventricular fibrillation ECG changes CNS changes Hypokalemia Bradycardia

Electrolyte Disorders Signs and Symptoms Excess Deficit Calcium (Ca) Hypercalcemia Thirst CNS deterioration Increased interstitial fluid Hypocalcemia Tetany Chvostek’s, Trousseau’s signs Muscle twitching CNS changes ECG changes Magnesium (Mg) Hypermagnesemia Loss of deep tendon reflexes (DTRs) Depression of CNS Depression of neuromuscular function Hypomagnesemia Hyperactive DTRs

Sodium Imbalances typically associated with parallel changes in osmolality Plays a major role in ECF volume and concentration Generation and transmission of nerve impulses Acid–base balance NV: 135-145 mEq/L

Hypernatremia Elevated serum sodium occurring with water loss or sodium gain Causes hyperosmolality leading to cellular dehydration Primary protection is thirst from hypothalamus

Hypernatremia Manifestations Impaired LOC Produced by clinical states Thirst, lethargy, agitation, seizures, and coma Impaired LOC Produced by clinical states Central or nephrogenic diabetes insipidus

Hypernatremia Serum sodium levels must be reduced gradually to avoid cerebral edema

Nursing Management Nursing Diagnoses Risk for injury Potential complication: seizures and coma leading to irreversible brain damage

Nursing Management Nursing Implementation Treat underlying cause If oral fluids cannot be ingested, IV solution of 5% dextrose in water or hypotonic saline Diuretics

Hyponatremia Results from loss of sodium-containing fluids or from water excess Manifestations Confusion, nausea, vomiting, seizures, and coma

Nursing Management Nursing Diagnoses Risk for injury Potential complication: severe neurologic changes

Nursing Management Nursing Implementation Caused by water excess Fluid restriction is needed Severe symptoms (seizures) Give small amount of IV hypertonic saline solution (3% NaCl)

Nursing Management Nursing Implementation Abnormal fluid loss Fluid replacement with sodium-containing solution

Potassium Major ICF cation Necessary for Transmission and conduction of nerve and muscle impulses Maintenance of cardiac rhythms Acid–base balance

Potassium Sources Fruits and vegetables (bananas and oranges) Salt substitutes Potassium medications (PO, IV) Stored blood NV: 3.5-5.0 mEq/L

Hyperkalemia High serum potassium caused by Massive intake Impaired renal excretion Shift from ICF to ECF Common in massive cell destruction Burn, crush injury, or tumor lysis

Hyperkalemia Manifestations Weak or paralyzed skeletal muscles Ventricular fibrillation or cardiac standstill Abdominal cramping or diarrhea

Nursing Management Nursing Diagnoses Risk for injury Potential complication: dysrhythmias

Nursing Management Nursing Implementation Eliminate oral and parenteral K intake Increase elimination of K (diuretics, dialysis, Kayexalate)

Nursing Management Nursing Implementation Force K from ECF to ICF by IV insulin or sodium bicarbonate Reverse membrane effects of elevated ECF potassium by administering calcium gluconate IV

Hypokalemia Low serum potassium caused by Abnormal losses of K+ via the kidneys or gastrointestinal tract Magnesium deficiency Metabolic alkalosis

Hypokalemia Manifestations Most serious are cardiac Skeletal muscle weakness Weakness of respiratory muscles Decreased gastrointestinal motility

Nursing Management Nursing Diagnoses Risk for injury Potential complication: dysrhythmias

Nursing Management Nursing Implementation KCl supplements orally or IV Should not exceed 10 to 20 mEq/hr To prevent hyperkalemia and cardiac arrest

Calcium Obtained from ingested foods More than 99% combined with phosphorus and concentrated in skeletal system Inverse relationship with phosphorus

Calcium Bones are readily available store Blocks sodium transport and stabilizes cell membrane Ionized form is biologically active NV: 4.5-5.5 mg/dl NV: (total) 9-11 mg/dl

Calcium Functions Transmission of nerve impulses Myocardial contractions Blood clotting Formation of teeth and bone Muscle contractions

Calcium Balance controlled by Parathyroid hormone Calcitonin Vitamin D

Hypercalcemia High serum calcium levels caused by Hyperparathyroidism (two thirds of cases) Malignancy Vitamin D overdose Prolonged immobilization

Hypercalcemia Manifestations Decreased memory Confusion Disorientation Fatigue Constipation

Nursing Management Nursing Diagnoses Risk for injury Potential complication: dysrhythmias

Nursing Management Nursing Implementation Excretion of Ca with loop diuretic Hydration with isotonic saline infusion Synthetic calcitonin Mobilization

Hypocalcemia Manifestations Positive Trousseau’s or Chvostek’s sign Laryngeal stridor Dysphagia Tingling around the mouth or in the extremities

Hypocalcemia Low serum Ca levels caused by Decreased production of PTH Acute pancreatitis Multiple blood transfusions Alkalosis Decreased intake

Tests for Hypocalcemia Chvostek’s – contraction of facial muscles in response to a light tap over the facial nerve in front of the ear Trousseau’s sign - carpal spasm induced by inflating a blood pressure cuff above the systolic pressure for a few minutes Fig. 17-15

Nursing Management Nursing Diagnoses Risk for injury Potential complication: fracture or respiratory arrest

Nursing Management Nursing Implementation Treat cause Oral or IV calcium supplements Not IM to avoid local reactions Treat pain and anxiety to prevent hyperventilation-induced respiratory alkalosis

Phosphate Primary anion in ICF Essential to function of muscle, red blood cells, and nervous system Deposited with calcium for bone and tooth structure NV: 2.8-4.5 mg/dl

Phosphate Involved in acid–base buffering system, ATP production, and cellular uptake of glucose Maintenance requires adequate renal functioning Essential to muscle, RBCs, and nervous system function

Hyperphosphatemia High serum PO43- caused by Acute or chronic renal failure Chemotherapy Excessive ingestion of phosphate or vitamin D

Hyperphosphatemia Manifestations Calcified deposition in soft tissue such as joints, arteries, skin, kidneys, and corneas Neuromuscular irritability and tetany

Hyperphosphatemia Management Identify and treat underlying cause Restrict foods and fluids containing PO43- Adequate hydration and correction of hypocalcemic conditions

Hypophosphatemia Low serum PO43- caused by Malnourishment/malabsorption Alcohol withdrawal Use of phosphate-binding antacids During parenteral nutrition with inadequate replacement

Hypophosphatemia Manifestations CNS depression Confusion Muscle weakness and pain Dysrhythmias Cardiomyopathy

Hypophosphatemia Management Oral supplementation Ingestion of foods high in PO43- IV administration of sodium or potassium phosphate

Magnesium 50% to 60% contained in bone Coenzyme in metabolism of protein and carbohydrates Factors that regulate calcium balance appear to influence magnesium balance

Magnesium Acts directly on myoneural junction Important for normal cardiac function NV: 1.5-2.5 mEq/L

Hypermagnesemia High serum Mg caused by Increased intake or ingestion of products containing magnesium when renal insufficiency or failure is present

Hypermagnesemia Manifestations Lethargy or drowsiness Nausea/vomiting Impaired reflexes Respiratory and cardiac arrest

Hypermagnesemia Management Prevention Emergency treatment IV CaCl or calcium gluconate Fluids to promote urinary excretion

Hypomagnesemia Low serum Mg caused by Prolonged fasting or starvation Chronic alcoholism Fluid loss from gastrointestinal tract Prolonged parenteral nutrition without supplementation Diuretics

Hypomagnesemia Manifestations Confusion Hyperactive deep tendon reflexes Tremors Seizures Cardiac dysrhythmias

Hypomagnesemia Management Oral supplements Increase dietary intake Parenteral IV or IM magnesium when severe

IV Fluids Purposes Maintenance Replacement When oral intake is not adequate Replacement When losses have occurred

IV Fluids Hypotonic More water than electrolytes Pure water lyses RBCs Water moves from ECF to ICF by osmosis Usually maintenance fluids

IV Fluids Isotonic Expands only ECF No net loss or gain from ICF

IV Fluids Hypertonic Initially expands and raises the osmolality of ECF Require frequent monitoring of Blood pressure Lung sounds Serum sodium levels

D5W Isotonic Provides 170 cal/L Free water Moves into ICF Increases renal solute excretion

D5W Used to replace water losses and treat hyponatremia Does not provide electrolytes

Normal Saline (NS) Isotonic No calories More NaCl than ECF 30% stays in IV (most) 70% moves out of IV

Normal Saline (NS) Expands IV volume Does not change ICF volume Preferred fluid for immediate response Risk for fluid overload higher Does not change ICF volume Blood products Compatible with most medications

Lactated Ringer’s Isotonic More similar to plasma than NS Expands ECF Has less NaCl Has K, Ca, PO43-, lactate (metabolized to HCO3-) Expands ECF

D5 ½ NS Hypertonic Common maintenance fluid KCl added for maintenance or replacement

D10W Hypertonic Provides 340 kcal/L Free water Limit of dextrose concentration may be infused peripherally

Plasma Expanders Stay in vascular space and increase osmotic pressure Colloids (protein solutions) Packed RBCs Albumin Plasma