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