Fluids and Electrolytes (Class 21)

Intracellular Fluids

Intracellular Fluids

• Inside the cells

• Represent 2/3 of the total body water

Extracellular Fluids

• Outside the cells

• Includes intravascular and interstitial fluid

Interstitial Fluid

Located between the cells and the outside of the membranes (considered the “third space”)

Intravascular Fluid

The liquid part of blood (blood plasma)

Osmolality

A measure of the number of particles/kilograms of water. Determines the concentration of the solution

Transcellular Fluid

• Cerebrospinal fluid

• Pleural fluid

• Peritoneal fluid

• Synovial fluid

Isotonic

• “Same strength”

• No net water movement

• Cells stay the same size

• Ex. 0.9% NS, Lactated Ringers

True

True or False: D5W is isotonic but becomes hypotonic once it reaches the cells.

Hypotonic

• “Lower strength”

• Water moves inside the cell

• Cells can swell or burst

• Ex. 0.225% NS, 0.45% NS

Hypertonic

• “Higher Strength”

• Water moves out of the cell

• Cells shrink

• Ex. Dextrose 10% in water, 3-5% NaCl.

Crystalloids

IV fluids

Colloids

Blood products/proteins

Active Transport

Requires energy to move electrolytes across cell membranes (from areas of lower concentration to areas of higher concentration.) Ex. Na and K pumps

Diffusion

Passive movement of electrolytes or other particles down a concentration gradient (from areas of higher concentration to area of lower concentration.)

Osmosis

Water moves through a membrane that separates fluids with different particle concentration. Electrolytes pull water with them.

Filtration

The net effect of four forces, two that tend to move fluid out of capillaries and two that tend to move fluid back into them. Acts at the capillary level.

Sources of Intake

• Drinking

• Eating foods

• Food metabolism

• IV

• Enemas

• Irrigation of body cavities

Sources of Output

• Urine

• Sweat

• Diarrhea

• Emesis

How the Body Maintains Homeostasis

• Fluid intake

• Fluid distribution

• Fluid output

Fluid Intake

Occurs orally through drinking but also through eating because most foods contain some water.

Fluid Distribution

• Means the movement of fluid among different compartments

• Occurs by osmosis at the ECF and ICF level.

• Occurs by filtration at the vascular and interstitial level.

Fluid Output

• Occurs through skin, lungs, GI tract, and kidneys.

• Examples of abnormal fluid output would include vomiting, wound drainage, diarrhea, or hemorrhage.

True

True or False: The hypothalamus is the thirst control center of the brain.

Insensible Fluid Loss

• Burns

• Fever

• Sweat

Hormones that Control Kidney Output

• Antidiuretic hormone

• The renin-angiotensin-aldosterone system

• Atrial natriuretic peptides

Fluid Volume Deficit Causes

• Intake < Output

• Severely decreased oral intake of water and salt

• Increased GI output: vomit, laxative overuse, etc.

• Increased renal output

• Loss of blood or plasma

Fluid Volume Deficit Signs and Symptoms

• Sudden weight loss

• Thirst

• Restlessness

• Confusion

• Hypotension

• Oliguria

• Hypovolemia shock

• Lab values:

  • Hematocrit increases

  • BUN increases

  • Specific gravity increases

Fluid Volume Excess Causes

• Intake > Output

• Excessive administration of IV fluids or water and salt.

• Renal retention of Na and water: heart failure, cirrhosis, renal disease, aldosterone, or glucocorticoid excess.

Fluid Volume Excess Signs nd Symptoms

• Sudden weight gain

• Confusion

• Edema

• Crackles in lungs

• Pulmonary edema

• Lab values:

  • Hematocrit decreases

  • BUN decreases

  • Specific gravity decreases

Hyponatremia

• Diluted body fluid

• <136 mEq/L

Hyponatremia Causes

• Excessive ADH

• Polydipsia or forced excessive water intake

• Tap-water edemas

• Excessive IV administration of D5W

• Replacement of a large body fluid output with water but not Na.

Hyponatremia Signs and Symptoms

• Decreased LOC

• Confusion

• Coma

• Thirst

• Seizures

• Lethargy

• Lab values:

  • Na <136 mEq/L

  • Serum osmolality <285 mOsm/kg

Hypernatremia

• Concentrated body fluids

• 145 mEq/L

Hypernatremia Causes

• Diabetes insipidus

• Osmotic diuresis

• Lack of access to water

• Large insensible perspiration

Hypernatremia Signs and Symptoms

• Same as hyponatremia

• Lab values:

  • Na >145 mEq/L

  • Serum Osmolality >295 mOsm/kg

Clinical Dehydration

A fluid volume deficit AND hypernatremia.

Hypernatremia Causes

• All causes of ECV deficit

• Poor or no water intake

Hypernatremia Signs and Symptoms

A combination of ECV findings and hypernatremia findings.

Risk Factors for Fluid and Electrolyte Imbalances

• Disease processes

• Medications

• Diarrhea

• Endocrine disorders

Potassium (K)

• Normal Value: 3.5-5.0 mEq/L

• Maintains the resting membrane potential of skeletal, smooth, and cardiac muscle, allowing normal muscle function.

• Food Sources:

  • Fruits

  • Potatoes

  • Instant coffee

  • Molasses

  • Brazil nuts

Hyperkalemia

• Abnormally high K caused by increased K intake and absorption.

• Can cause:

  • Muscle weakness

  • Cardiac dysrhythmias

  • Cardiac arrest

• People with oliguria are at risk.

Hypokalemia

• Abnormally low K

• Caused by:

  • Diarrhea

  • Vomiting

  • K Wasting diuretics

• Causes:

  • Muscle weakness

  • Cardiac dysrhythmias

True

True or False: Any tissue trauma will cause K to leak into the bloodstream.

False

True or False: Pushing K does not pose any threat to a patient.

Independent Nursing Interventions

• Daily weights

• Measure I/O’s

• Fluid restriction-hyponatremia

• Safety precautions (fall)

• Liquids that contain lactose or have a low sodium content are inappropriate when a patient has diarrhea

• Physical examination

• Seizure precautions (hyponatremia)

• Orthostatic vitals

Dependent Nursing Interventions

• Antiemetics for nausea

• IV hydration

• Hematocrit

• Sodium

• Kidney function (BUN + CR)

• BMP for electrolytes

Calcium

• Normal Value: 9.0-10.5 mg/dL

• Influences excitability of nerve and muscle cells

• Necessary for muscle contraction

• Requires vitamin D for the best absorption

• Food Sources:

  • Dairy products

  • Canned fish with bones

  • Broccoli

  • Oranges

Hypercalcemia

• Results from increased intake/absorption

• Caused by some cancers that draw calcium out of the bones or bone injuries

• Decreases neuromuscular excitability and increases lethargy

Hypocalcemia

• Low calcium concentration in the blood.

• Commonly seen in pancreatitis patients as the calcium binds to the fat.

• Causes hyperactive reflexes, numbness and tingling, and tetany.

True

True or False: Chvostek’s Sign is a symptom of decreased Ca and Mg.

Magnesium (Mg)

• Normal Value: 1.3-2.1 mEq/L

• Influences function of neuromuscular junctions

• Cofactor for numerous enzymes

• Food Sources:

  • Dark leafy greens

  • Whole grains

  • Some laxatives and antacids

  • Undigested fat prevents absorption

Phosphate

Normal Value: 3.0-4.5 mEq/L

False

True or False: Elderly patients have an increased thirst response.

True

True or False: Daily weights are the most effective intervention for monitoring fluid status.

Hematocrit Lab Values

• Increased with EFV deficit

• Decreased with EFV excess

Urine Specific Gravity Lab Values

• Increases with EFV deficit

BUN Lab Values

• Focuses on hydration status

• Increases with EFV deficit

• Decreases with EFV excess

K and Mg

Electrolytes decreased after surgery.

Signs and Symptoms of Infiltration/Extravasation

• Coolness

• Edema

• Pallor

Nursing Interventions for Infiltration/Extravasation

• Immediately stop infusion

• Immediately assess

• Do not apply pressure

Signs and Symptoms of Phlebitis

• Signs of infection along a vein

Nursing Interventions for Phlebitis

• Frequently change peripheral IV to avoid this.

Signs and Symptoms of Local Infection

• Erythema

• Tenderness

• Heat

Nursing Interventions for Local Infections

• Use aseptic technique

• Assess frequently

Signs and Symptoms of Air Embolism

• Dyspnea

• Chest pain

• Tachycardia

• Coughing

• Decreased LOC

Nursing Interventions for Air Embolism

• Prime tubing

• Avoid puncturing tubing