Unit 2 Fluid And Electrolyte Imbalance Answers

Unit 2 – Fluid and Electrolyte Imbalance
A. Homeostasis
a. State of equilibrium in the body
b. Naturally maintained by adaptive responses
c. Body fluids and electrolytes are maintained within narrow limits
B. Water content of the body
i. Varies with age, gender, body mass
1. Men have more muscle mass → increased water, fat cells have less water content
b. 50-60% of the weight in an adult
c. 45-55% in older adults
d. 70-80% in infants
C. Body Fluid Components
a. ICF
b. ECF
i. Intravascular (plasma) ii. Interstitial iii. Transcellular
D. Electrolytes
a. Substances whose molecules dissociate into ions (charged particles) when placed into water
i. Ions: charged particles ii. Cations: positively charged iii. Anion: Negatively
charged (protein carries a negative charge)
b. Electrolytes are measured in millimoles per liter
c. US uses milliequivalent (mEq)
d. Composition of Electrolytes
i. ICF
1. Prevalent cation is K+
2. Prevalent anion is PO4 3-
ii.
ECF
1. Prevalent cation is Na+
2. Prevalent anion is Cl-
E. Mechanisms controlling fluid and electrolyte movement
a. Diffusion
i. Movement of molecules from high to low concentration
1. Occurs in liquids, solids, gases
2. Membrane separating two areas must be permeable to diffusing substance
3. Requires no energy
b. Facilitated diffusion
i. Movement of molecules from high to low concentration without energy
1. Uses specific carrier molecules to accelerate diffusion
2. Passive and requires no energy
c. Active transport
i. Process in which molecules move against concentration gradient (ie. Sodium-potassium pump)
1. External energy required (ATP)
d. Osmosis
i. Movement of water (not particles) compartments separated by a membrane permeable to water but not to solute ii. Water moves from low solute to high solute concentrations iii. Requires no energy!!
e. Osmotic Pressure
i. Amount of pressure required to stop osmotic flow of water
1. Determined by concentration of solutes in solution
2. Measured in milliosmoles
f. Osmotic movement of fluids
i. Types of solutions
1. Isotonic (osmolality is the same)
2. Hypotonic (hyperosmolar) - less concentrated (less particles), more dilute (lower
osmolality)
3. Hypertonic (hyperosmolar) – more concentrated, higher osmolality ii. Normal plasma osmolalit 275-295mOsm/kg
1. Water deficit
2. Water excess
g. Hydrostatic Pressure
i. Force within a fluid compartment
ii.
Major force that pushes water out of vascular system at capillary level
1. Example – BP – force against the wall of a vessel
h. Oncotic Pressure (Colloidal osmotic pressure)
i. Osmotic pressure exerted by colloids in a solution
1. Protein is a major colloid*
F. Fluid Movement in Capillaries
a. Amount and direction of movement determined by:
i. Capillary hydrostatic pressure ii. Plasma oncotic pressure iii. Interstitial hydrostatic pressure iv. Interstitial oncotic pressure
G. Fluid shifts
a. Plasma to interstitial fluid shift results in edema
i. Elevation of venous hydrostatic pressure ii. Decrease in plasma oncotic pressure iii. Elevation of interstitial oncotic pressure
b. Interstitial fluid to plasma
i. Fluid drawn into plasma space with increase in plasma osmotic or oncotic pressure ii. Compression stockings decrease peripheral edema
c. Fluid movement b/w ECF and ICF
i. Water deficit (increased ECF)
1. Associated with symptoms that result from cell shrinkage as water is pulled into vascular system
a. 1st change seen is in the CNS w/ level of consciousness ii. Water excess (decreased ECF)
1. Develops from gain or retention of excess water
d. Fluid Spacing
i. First
spacing
1. Normal distribution of fluid in ICF and ECF ii. Second Spacing
1. Abnormal accumulation of interstitial fluid (edema) iii. Third Spacing
1. Fluid Accumulation in part of body where it is not easily exchanged with the rest of the ECF
2. Hard to clinically correct, dangerous
a. Examples: transcellular fluid in peritoneal cavity → ascites, liver failure
H. Regulation of water balance
a. Hypothalamic regulation
i. Osmoreceptors in hypothalamus sense fluid deficit or increase
1. Stimulates thirst and antidiuretic hormone release
2. Result in increased free water and decreased plasma osmolarity
b. Pituitary regulation
i. Under control of hypothalamus, posterior pituitary releases ADH ii. Stress, nausea, nicotine, and morphine also stimulate ADH release
c. Adrenal cortical regulation
i. Releases hormones to regulate water an electrolytes
1. Glucocorticoids
a. Cortisol
2. Mineralocorticoids
a. Aldosterone – helps body hold on to sodium (water follows sodium), lets go of potassium
b.
d. Renal regulation
i. Primary organs for regulating fluid and electrolyte balance
1. Adjusting urine volume
a. Selective reabsorption of water and electrolytes
b. Renal tubules are sites of action of ADH and aldosterone ii. Less renal profusion leads to production of aldosterone → hold onto Na+, get H2O, let go of K+
e. Cardiac regulation
i. Natriuretic peptides are antagonists to the RAS
1. Produced by cardiomyocytes in response to increased atrial pressure
2. Suppress secretion of aldosterone, rennin, and ADH to decrease blood volume and pressure
f. GI regulation
i. Oral intake accounts for most water ii. Small amounts of water are eliminated by GI tract in feces iii. Diarrhea and vomiting can lead to significant fluid and electrolyte loss
1. Fluid in the GI tract is transcellular (absorbs 8L per day)
g. Insensible water loss
i. invisible vaporization from lungs and skin to regulate body temperature
1. Approx. 600 to 900mL.day is lost
2. No electrolytes are lost (only water, but sweat does have electrolytes in it)
I. Gerontologic Considerations
a. Structural changes in kidneys decrease ability to conserve water
b. Hormonal changes lead to decrease in ADH and ANP
c. Loss of subQ tissue leads to increased loss of moisture
d. Reduced thirst mechanism → decreased fluid intake
e. Nurse must assess for these changes and implement treatment accordingly
J. Fluid and Electrolyte imbalances
a. Common in most patients with major illness or injury
i. Directly caused by illness or disease (burns or heart failure) ii. Result of therapeutic measures (IV fluid replacement or diuretics)
K. Extracellular Fluid Volume Imbalances
a. ECF volume deficit (hypovolemia)
i. Abnormal loss of normal boy fluids (diarrhea, fistula drainage, polyuria, hemorrhage), inadequate intake or plasma-to-interstitial fluid shift ii. Treatment – replace and electrolytes with balanced IV solutions
1. Signs and Symptoms
a. Increased pulse, hypotension
b. ECF volume excess (hypervolemia)
i. Excessive intake of fluids, abnormal retention of fluids (HF or RF), or interstitial to plasma fluid shift ii. Treatment: remove fluid without changing electrolyte composition or osmolality of ECf
1. Signs and symptoms
a. Bounding pulse, increased BP
L. Nursing Diagnoses
a. Hypovolemia
i. Deficient fluid volume ii. Decreased CO iii. Risk for deficient fluid volume iv. Potential complication: hypovolemic shock
b. Hypervolemia
i. Excess fluid volume ii. Risk for imbalanced fluid volume iii. Impaired gas exchange iv. Risk for impaired skin integrity
v. Disturbed body image vi. Potential complications: pulm. Edema, ascites
M. Nursing Implementation
a. I&O
b. Monitor cardiovascular changes
c. Assess respiratory changes (crackles or rhales with fluid in lungs)
d. Daily weights
e. Skin assessment
f. Neurologic Function
i. LOC ii. PERRLA iii. Voluntary movement of extremities iv. Muscle strength
v. Reflexes
g. Other nursing measures
i. Carefully administer IV solutions ii. Patient’s receiving TF will require additional water iii. Patient with NG suction should not take PO water – water will increase loss of electrolytes iv. Encourage PO fluids if able
N. Electrolyte Disorders
a. Signs and Symptoms
1. Sodium: normal range 145-175
2. Imbalances associated with parallel changes in osmolality
3. Plays a role in ECF volume and concentration
4. Generation and transmission of nerve impulses
5. Acid-base balances
a. Excess = Hypernatremia
b. Elevated serum sodium occurring with water loss or sodium gain
c. Causes hyperosmolality leading to cellular dehydration
d. Primary protection is thirst from hypothalamus
i. Thirst, lethargy, agitation, seizures and coma ii. CNS deterioration, impaired LOC iii. Increased interstitial fluid
6. Deficit = hyponatremia
a. CNS deterioration
b.
ii. Potassium normal range: 3.5-5
1. Excess = hyperkalemia
a. Ventricular fibrillation
b. ECG changes
c. CNS changes
2. Deficit = Hypokalemia
a. Bradycardia
b. ECG changes
c. CNS changes iii. Calcium normal range: 8.2-10.2
1. Excess = hypercalcemia
a. Thirst
b. CNS deterioration
c. Increased interstitial fluid
2. Deficit = hypocalcemia
a. Tetany
b. Chvostek’s Trousseau’s signs
c. Muscle twitching
d. CNS changes
e. ECG changes