Fluids and electrolytes

CONCEPT OF FLUIDS AND ELECTROLYTES

FLUIDS AND ELECTROLYTES MODULE 6

Concept Learning Outcomes

• 6.1 Analyze the physiology of fluids and electrolytes in the body.

• 6.2 Differentiate alterations in fluids and electrolytes.

• 6.3 Outline the relationship between fluids and electrolytes and other concepts.

• 6.4 Explain the promotion of maintaining fluid and electrolyte balance.

• 6.5 Differentiate among common assessment procedures and tests used to examine fluid and electrolyte balance.

• 6.6 Analyze independent interventions nurses can implement for patients with alterations in fluid and electrolyte balance.

• 6.7 Summarize collaborative therapies used by interprofessional teams for patients with alterations in fluid and electrolyte balance.

• 6.8 Differentiate considerations related to the care of patients with alterations in fluid and electrolyte balance throughout the lifespan.

BODY FLUIDS REQUIRED FOR HOMEOSTASIS

• Types of Bodily Fluids:

  • Blood

  • Serum

  • Albumin

  • Urine

  • Bile

  • Hormones

  • Cerebrospinal Fluid

• Electrolytes:

  • Charged ions capable of conducting electricity, found within bodily fluids.

  • Critical for fluid and electrolyte balance which is essential for health.

• Fluid Imbalance:

  • Can result from various conditions affecting both chronic and acute illnesses.

  • Almost any illness could potentially create some form of imbalance.

  • Therapeutic measures can disturb homeostasis.

• Fluid Intake vs. Output:

  • Intake should equal fluid output.

  • Typical values:

  • Intake: 2000 mL

  • Output: 1500 mL

  • Allowable difference: 200 – 300 mL.

DISTRIBUTION AND COMPOSITION OF BODY FLUIDS

• Intracellular Fluid (ICF):

  • Found within body cells, constituting approximately 2/3 of total body fluid in adults.

  • Vital for normal cell functioning; contains solutes such as:

  • Oxygen

  • Electrolytes - measured in (Meq/L)

  • Glucose

  • Primary Cations: Potassium, Magnesium: +

  • Major Anions: Phosphate, Sulfate: -

• Extracellular Fluid (ECF):

  • Located outside cells, making up about 1/3 of total body fluid.

  • Main Compartment Types:

  • Intravascular Fluid (in the bloodstream) - 6% of all fluids

  • Interstitial Fluid (between cells) - 22% of all fluids

  • Other compartments include lymph and transcellular fluids.

  • Principal Electrolytes in ECF: Sodium, Calcium, Bicarbonate

  • Serves as a transport system for nutrients and waste products.

  • Third Spacing: fluids end up in places that they don’t belong

MOVEMENT OF BODY FLUIDS

• Mechanisms of Fluid Movement:

  • Osmosis: Movement of water across cell membranes from a less concentrated to a more concentrated solution.

  • Diffusion: Intermingling of molecules within liquids, gases, or solids; influenced by molecule size, concentration, and temperature.

  • Filtration: Movement of fluids and solutes together across a membrane from higher to lower pressure areas, determined by the balance of hydrostatic pressure and osmotic pressure.

  • Active Transport: Movement of substances across membranes against their concentration gradient, requiring metabolic energy. This is critical in maintaining sodium and potassium ion concentrations in ECF and ICF, managed by the sodium-potassium pump.

• Osmotic Pressure: Refers to the power of a solution to draw water across a membrane, significant in regulating fluid distribution between compartments:

  • Colloid Osmotic Pressure: The component of osmotic pressure exerted by plasma proteins which pulls water from interstitial spaces into the vascular compartment.

• Normal Blood Osmolarity: Typically ranges from 275 to 300 mOsm/kg, which is essential for maintaining a balance of fluids and electrolytes in the body.

REGULATING BODY FLUIDS

• Fluid Intake/Loss Balancing:

  • Ideally intake should equal loss to maintain fluid homeostasis.

  • Typical fluid intake: 2500 mL/day at moderate activity and temperature.

  • Fluid output: Approximately 1400 to 1500 mL/day through urine, insensible losses from skin and lungs, and feces.

  • Insensible loss: about 400 mL a day

• Kidneys: Primary regulators of fluid balance; filter waste products, return electrolytes to blood, adjust reabsorption of water from plasma filtrate, and play a significant role in acid-base regulation.

• Hormonal Regulation:

  • Antidiuretic Hormone (ADH): Regulates water excretion from kidneys.

  • Renin–Angiotensin–Aldosterone System: Controls blood pressure and fluid balance.

  • Atrial Natriuretic Factor (ANF): Promotes sodium excretion, inhibits thirst, and acts as a diuretic.

DISORDERS OF FLUID AND ELECTROLYTE BALANCE

• Fluid Volume Excess (FVE):

  • Intake exceeds output, leading to symptoms such as weight gain, pitting edema, cough, dyspnea, and decreased urinary output.

• Fluid Volume Deficit (FVD):

  • Output exceeds intake, common symptoms include diarrhea, vomiting, increased urinary output, and weight loss.

• **Electrolyte Disorders: (Example: Sodium)

  • Hyponatremia: Sodium levels fluctuate, common risks include excessive fluid intake, liver disease, and medications. Symptoms range from confusion to seizures.

  • Hypernatremia: Excess sodium, characterized by thirst, dry membranes, and potentially leading to serious neurological symptoms.

• Low BP: often given preload to strengthen blood flow

REGULATING ELECTROLYTES

• Electrolytes Function:

  • Maintain fluid balance, contribute to acid-base regulation, facilitate enzyme reactions, and transmit neuromuscular signals.

• Electrolyte Levels:

  • Measured in milliequivalents per liter (mEq/L). Common electrolytes include sodium, potassium, calcium, magnesium, and chloride with specified normal serum levels.

SPECIFIC ELECTROLYTES

• Sodium (Na+):

  • Most abundant cation in ECF; normal serum level: 135-145 mEq/L; roles in water balance and blood pressure regulation, and pH.

  • Found in foods like bacon, processed can foods, and table salt.

  • Suggested intake: less than 2,300 mg/day

  • Sodium hypernatremia- big and bloated

    • Critical value: > 160 meq/L

    • Symptoms: thirst, dry sticky mucus membranes, OH, dyspnea, nausea, vomiting, increased muscle tone.

    • Lower sodium levels gradually

  • Sodium hyponatremia: < 135 meq/L

    • Critical value: <115 meq/L

    • Symptoms: mental status changes, headache, muscle twitching, seizures, abd cramps, n/v, anorexia, lethargy, and confusion.

• Potassium (K+): 80% excreted through Kidneys, 20% through bowels

  • Major ICF cation involved in muscle function and acid-base balance; normal serum level: 3.5-5 mEq/L.

  • Found in fruits, vegetables, meat, and fish

  • Potassium Hyperkalemia: 5.5 meq/L

    • Critical value: 7.0 meq/L

    • Symptoms: ECG changes, vague muscle weakness, GI hyperactivity, flaccid muscle paralysis, numbness in extremities, face and tongue.

  • Potassium Hypokalemia: Think low and slow 3.5 meq/L

    • Critical value: <2.5 meq/L

    • Symptoms: alkalosis, cardiac arrythmias, muscle soreness, leg cramps, fatigue, lethargy, n/v.

  • Cardiac monitoring is very important.

• Calcium (Ca2+): 99% in skeletal muscle system (Bones, blood (clotting factors), beats (heart beats))

  • Vital for muscle contraction and cardiac function; normal total serum calcium: 9-11 mg/dL.

  • Calcium levels reported in two ways:

    • Normal total serum calcium level: 9-11 mg/dl

    • Normal ionized serum calcium level: 4.25-5.25 mg/dl (Available calcium not attached to proteins)

  • Found in milk, dark green leafy vegetables, canned salmon

    • Calcium Hypercalcemia: > 5.5 mg/dl and serum calcium > 11 meq/L

      • Symptoms: ECG changes, lethargy, n/v, polyuria, polydipsia, psychosis, cardiac arrest.

    • Calcium Hypocalcemia: < 4.5 meq/L and serum calcium < 9 meq/L

      • Symptoms: Numbness, tingling, muscle tremors, cramps, muscle changes, Chvostek’s sign, Trousseau’s sign

      • Supplements should be administered 1-2 hours after meals to increase intestinal absorption.

  • Diluted in D5W.

• Magnesium (Mg2+): Law and Order of the Muscles

  • Important for intracellular metabolism and neuromuscular function

  • Found in skeletal system

  • Second most abundant ICF cation

  • Normal serum level: 1.5 - 2.5 meq/L

  • Involved in regulating neuromuscular, cardiac function (primarily uterus and cardiac)

• Chloride (Cl-):

  • Regulates serum osmolality with sodium; normal serum level: 95-105 mEq/L.

• Phosphate (PO4 3-):

  • Major anion in ICF critical for muscle and nerve function; normal level: 2.4-4.5 mg/dL.

ALTERATIONS TO FLUIDS AND ELECTROLYTES

• Various health conditions including chronic kidney disease (CKD) and acute kidney injury (AKI) can lead to significant alterations in fluid and electrolyte balance.

COMPENSATION FOR IMBALANCES

• The body tries to compensate for imbalances by shifting fluids and electrolytes between compartments. Rarely does only one type of imbalance occur.

• Mild electrolyte disorders can be associated with significant illness or mortality.

HEALTH PROMOTION AND NURSING ASSESSMENT

• Regular monitoring of patient hydration, education on fluid intake, assessment of weight, and vital signs are crucial in maintaining fluid and electrolyte balance.

• Strategies include monitoring dietary intake, encouraging adequate hydration, and recognizing specific patient needs such as those in vulnerable populations (e.g., infants, pregnant women, and older adults).

INTERVENTIONS AND COLLABORATION

• Nursing interventions include monitoring, assessing, and educating patients about their fluid and electrolyte balance. Implementing independent and collaborative interventions, such as electrolyte supplementation and dietary modifications, is essential in managing patient care.