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Introduction to Fluids & Electrolytes
Learning Objective
On completion of this chapter, the learner will be able to:
1. Differentiate between osmosis, diffusion, filtration, and active transport.
2. Describe the role of the kidneys, lungs, and endocrine glands in regulating the body’s fluid composition and volume.
3. Identify the effects of aging on fluid and electrolyte regulation.
4. Plan effective care of patients with the following imbalances: fluid volume deficit and fluid volume excess; sodium deficit (hyponatremia) and sodium excess (hypernatremia); potassium deficit (hypokalemia) and potassium excess (hyperkalemia).
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5. Describe the etiology, clinical manifestations, management, and nursing interventions for the following imbalances: calcium deficit (hypocalcemia) and calcium excess (hypercalcemia); magnesium deficit (hypomagnesemia) and magnesium excess (hypermagnesemia); phosphorus deficit (hypophosphatemia) and phosphorus excess (hyperphosphatemia); chloride deficit (hypochloremia) and chloride excess (hyperchloremia).
6. Explain the role of the lungs, kidneys, and chemical buffers in maintaining acid–base balance.
7. Compare metabolic acidosis and alkalosis with regard to causes, clinical manifestations, diagnosis, and management.
8. Compare respiratory acidosis and alkalosis with regard to causes,
clinical manifestations, diagnosis, and management.
9. Interpret arterial blood gas measurements. 10. Demonstrate a safe and effective
procedure of venipuncture. 11. Describe measures used for preventing
complications of intravenous therapy
Nursing Care is directed toward:
Assessing for clients at risk Monitoring clients for EARLY manifestations Implement collaborative and nursing
interventions to prevent or correct imbalances What segment of the life span is at highest
risk of fluid imbalances?
Fluid Compartments Intracellular (ICF) (2/3 of the fluid)
fluids contained within the cells Extracellular (ECF) (1/3 of the fluid)
(Remember blood tests measure extracellular fluid only – that’s why sodium is high and potassium is low!)
Interstitial (between the cells) Intravascular (plasma)
arteries, veins, capillaries Transcellular
misc: urine, digestive secretions, perspiration etc. Theoretical Third Space: trapped ECF in actual or
potential body space due to disease or injury Important in burns, shock and cardiovascular
Movement of Body Fluids: Important Concept
Body fluids are not static. Fluids & electrolytes shift from compartment to compartment.
Emphasis is always on maintaining homeostasis
FLUID MOVEMENT: review & see Table 11-2, p. 145 (Iggy)
Diffusion
Osmosis
Filtration
Active Transport
Osmosis Movement of water across a semi-permeable
membrane from an area of low solute concentration (lots of water) to an area of high solute concentration (less water) until even distribution (homeostasis) is achieved
Osmolarity = number of milli-osmoles in liter of solution Normal = 270 – 300 (or 275 – 295)
Osmolality = number of mill-osmoles in kilogram of solution
Isotonic Fluidsexample: normal saline 0.9% NaCl No net fluid (water)
shifts occur because the fluids are EQUALLY concentrated
Hypotonic Fluidsexample: 0.45% NaCl When a LESS
concentrated fluid is placed next to a MORE concentrated solution, water moves to MORE concentrated solution to equalize the solutions
Hypertonic Fluidsexample: 3% NaCl When a MORE
concentrated fluid is placed next to a LESS concentrated solution, water moves to the MORE concentrated solution to equalize the solutions
Body Fluids
Sources of fluid intake ingested fluids/foods water as byproduct of metabolism
Fluid Loss Urine Respiration Perspiration Gastrointestinal tract
KIDNEY FUNCTIONS
Regulate fluid volume and osmolality by selectively retaining & excreting fluids
Regulate electrolyte levels by selectively retaining & excreting e-lytes
Regulate pH (acid/base balance) by selectively retaining & excreting H+
Excrete metabolic wastes & toxic substances
THE NEPHRON
REGULATORY MECHANISMS THIRST KIDNEYS
Kidney Function HORMONES
Renin-Angiotensin-Aldosterone Anti-Diuretic Hormone Parathormone
Anti-Diuretic Hormone (think beer)
Parathyroid Hormone
Important for Calcium and Phosphorus balance
Where are the parathyroid glands????
Dehydration
Isotonic dehydration: water & electrolytes lost in equal proportions
Hypertonic dehydration: water loss exceeds electrolyte loss
Hypotonic dehydration: electrolyte loss exceeds water loss
Dehydration Etiology
Isotonic: inadequate fluid intake, fluids shifts between compartments, excessive loss of body fluids
Hypertonic: excessive perspiration, hyperventilation, fever, diarrhea, ketoacidosis
Hypotonic: chronic illness such as renal failure, excessive ingestion hypotonic fluids (babies & water!)
DEHYDRATION: FLUID VOLUME DEFICIT nsg dx PATHOPHYSIOLOGY
Loss of GI fluids (vomiting, diarrhea, NG suctioning, fistulas, intestinal drainage, chronic abuse of laxatives and/or enemas)
Renal loss from diuretics Water loss from sweating or heat Blood loss (hemorrhage) Fluid lost to Third Space (burns, trauma)
Dehydration
History (risk factors) age (very young & very old) check loss of body weight history of fluid losses
Dehydration
ASSESSMENT/MANIFESTATIONS Hypotension (decreased systolic, narrowed pulse
pressure, postural hypotension) Weak, rapid pulse with collapsed veins Decreased skin turgor, dry membranes Output > Intake (urine high specific gravity) Weight loss (1000 ml = 1000gm or 1 kg (2.2
pounds) ** very important
Dehydration
Lab Assessment Serum electrolytes abnormal Urine specific gravity high (urine is concentrated) Low central venous pressure Elevated hematocrit and BUN (blood urea nitrogen)
Caused by more solute, less water = hemoconcentration
Nursing Diagnosis: FLUID VOLUME DEFICIT
Diet therapy Oral fluid replacement Oral rehydration therapy
Pediatric implications to follow on future slide Drug therapy (varies with type of dehydration)
IV = isotonic (safest) 0.9% NaCl, Ringer’s Lactate Meds to treat underlying problem
Dehydration: Pediatric Implications Assessment Manifestations
Tend to be subtle & happen quickly You have a site to observe on an infant that no
longer exists on an adult - ?? FONTANELS (anterior & posterior) Give isotonic fluids
Pedialyte (Gatorade) Professional Responsibility
Community Based Care: Adults & Children Health teaching
Diet, drugs, & avoidance in the future Home care management
control environmental temperature & humidification family offers fluids frequently (avoid large amounts plain
water in formula fed infant – see under hyponatremia) Health care resources
Home care visit
Overhydration (nsg dx fluid volume excess)
PATHOPHYSIOLOGY Isotonic = hypervolemia Hypotonic = excessive fluid (water intoxication) Hypertonic = rare, excessive sodium intake
SUMMARY: TOO MUCH FLUID! Steroids, heart failure, cirrhosis of the liver, renal failure,
adrenal gland disorders, excessive intake IV fluids or Sodium (foods, meds, IV solutions)
FLUID VOLUME EXCESS
ASSESSMENT/MANIFESTATIONS Increased blood pressure Strong, bounding pulse with neck vein distention Taut skin turgor, moist mucous membranes Intake > Output (urine low specific gravity) Weight gain Crackles in lung sounds, orthopnea, irritating cough
OVERHYDRATION (FVE)
Diagnostic Tests Electrolytes Decreased hematocrit & BUN (Blood urea
nitrogen) Caused by more water, less solute = hemodilution
Increased central venous pressure Drug therapy
Diuretics Sodium & Water Restriction
Overhydration Nursing Diagnoses Fluid Volume Excess
as above & assess I&O, vital signs, edema daily weights education: sodium
Risk for Impaired Skin Integrity Potential: Respiratory Insufficiency