Fluid, Electrolytes, and Acid-Base Balance Lecture Notes

Exam Information

• Exams will focus more on application-based questions.

Module Preface: Fluid, Electrolytes, and Acid-Base Balance

• This module is crucial for understanding the basics of nursing.

• It's the foundation for future learning in cardiovascular, respiratory, and GI systems.

• Also important in 201, where there is an endocrine module based on these principles.

• The content may seem challenging, especially with the introduction of chemistry concepts.

• It's essential to grasp these concepts to avoid struggling in upper-level semesters.

• Experiencing real patient scenarios helps solidify understanding.

Fundamental Chemistry Understanding

• The body aims to maintain homeostasis.

• Fluid and electrolyte imbalances affect cells, tissues, and organs.

Terminology

• Solvent: The liquid part of the body (fluid).

• Solute: The particles in a solution.

• Electrolytes (Ions): Charged particles (positive and negative).

• Electrolyte abbreviations should indicate their charge.

• Intracellular Fluid: Fluid inside the cells.

• Extracellular Fluid: Fluid outside the cells.

• Interstitial Fluid: Fluid in the spaces between cells.

Water

• Water is crucial for the body.

• The body can only survive about three days without water before significant issues arise.

• Functions of water:

  • Transports waste products.

  • Acts as a solvent.

  • Necessary for metabolism.

  • Helps with digestion.

  • Regulates body temperature.

  • Maintains blood volume.

• Average adult body weight composition:

  • Approximately 60% water.

  • Higher in children.

  • Lower in the elderly due to decreased muscle mass.

• Muscle holds water, while fat repels it.

• Women generally have less water than men due to higher fat content.

• Daily water needs:

  • Two to three liters per day (2000-3000 mL).

  • Found in food and beverages, except alcohol.

• Alcohol causes dehydration.

• Drinking alcohol shifts fluids around, leading to dehydration and headaches.

• Drinking water while intoxicated can help with purging alcohol faster.

• 1 \text{ liter of water} = 1 \text{ kilogram} = 2.2 \text{ pounds}

• Adequate heart and kidney function are necessary for fluid balance.

Fluid Movement

• Three processes facilitate fluid movement:

  • Filtration

  • Diffusion

  • Osmosis

Filtration

• Movement occurs due to hydrostatic pressure.

• Fluid moves from areas of greater concentration to lesser concentration.

• It’s known as "water pushing pressure."

• Example: Fluid inside vessels, where excess fluid can lead to edema.

• Veins stretch, but only to a certain extent, and excess fluid filters into the interstitial space.

• Edema: Fluid in the interstitial space.

• Assessing edema:

  • Check for pitting.

  • Document the depth and time it takes for the indentation to resolve.

• Filtration is essentially water pushing pressure, moving from high to low concentration areas.

Diffusion

• Movement of molecules from high to low concentration until equilibrium is achieved.

• Only solute moves; fluid remains stationary.

• Particles are in constant motion, leading to equilibrium.

• Affected by:

  • Concentration gradient.

  • Size and amount of particles.

  • Temperature.

• Example:

  • Dissolving sugar in hot tea versus cold tea.

  • Sugar dissolves faster in hot tea due to temperature aiding diffusion.

• Sometimes, particles need assistance to move (facilitated diffusion), such as glucose requiring insulin.

Osmosis

• Movement of water only through a semi-permeable membrane.

• Particles cannot pass through the membrane.

• Water moves from areas of lesser concentration to greater concentration to dilute the space.

• Known as “water pulling pressure” or “water pulling force.”

• Defines terms like hypertonic, hypotonic, and isotonic.

• Water shifts due to electrolytes, hormones, and regulatory mechanisms.

• Osmolarity: number of milliosmols per liter of solution.

• Osmolality: number of milliosmols per kilogram of solution.

Isotonic, Hypertonic, and Hypotonic Solutions

• Isotonic: Equal concentration on both sides; no fluid shift.

• Hypertonic: Too many solutes; water is pulled in to dilute concentration.

• Hypotonic: Less solutes; water is pushed out.

• Lab work reflects blood content.

• Fluid imbalances (e.g., edema) may not reflect blood content.

• Osmosis and filtration work together to maintain fluid shift and homeostasis.

• Sweating leads to fluid loss, increasing particle concentration, and causing fluid shift from intracellular to extracellular spaces.

• This triggers thirst.

• Hypertonic means water pulling. Hypotonic means water pushing. Isotonic maintains balance.

Fluid and Electrolyte Balance

• Electrolytes carry either a positive (cation) or negative (anion) charge.

• Electrolyte concentrations differ between intracellular and extracellular fluids.

• All adults are at risk for electrolyte imbalances, with older adults at higher risk.

• Fluid balance is affected by:

  • Age

  • Gender

  • Fat content

• Decreased muscle mass in the elderly leads to decreased fluid.

• Women have less fluid due to higher fat concentration.

• Obese individuals have less fluid in fat tissue.

• Average fluid intake: two to three liters per day.

• Fluid intake:

  • Actual liquids (except alcohol).

  • Foods.

  • Catabolism (breakdown processes).

• Fluid output:

  • Kidneys.

  • Skin.

  • Lungs (exhalation).

  • GI tract (formed stool contains water).

  • Drainage from wounds.

  • GI suction.

  • Salivation.

• Insensible water loss: Water loss that cannot be controlled or measured i.e. exhalations.

• Examples include:

  • Exhalations

  • Sweat

  • GI tract.

Fluid Regulation

• Regulated through hormones:

  • Aldosterone

  • Antidiuretic hormone (ADH)

  • Natriuretic peptides

Aldosterone

• Produced in the adrenal cortex.

• Reabsorbs sodium and water.

• Water follows sodium.

• Prevents hypernatremia and hyperkalemia.

Antidiuretic Hormone (ADH/Vasopressin)

• Prevents fluid loss and causes vasoconstriction.

• Retains water and constricts vessels.

• Increases blood pressure when fluid volume is low.

Natriuretic Peptides (ANP, BNP)

• Respond to increased blood volume and pressure.

• Control sodium retention or excretion, affecting water balance.

Renin-Angiotensin-Aldosterone System (RAAS)

• Compensatory response controlled by kidneys.

• Activated when fluid volume is low.

• Kidneys release renin, converting to angiotensin I.

• Angiotensin I converts to angiotensin II with angiotensin-converting enzyme (ACE).

• Angiotensin II causes vasoconstriction, raising blood pressure.

• Activated during shock or severe stress.

• Urine output indicates adequate perfusion.

• Kidneys preserve fluid by shutting down when there is not enough fluid volume.

• Normal urine output: 30 mL per hour.

• Low urine output may indicate fluid shifting.

• Hypertension patients should avoid sodium.

• The kidneys don’t like to be insulted; they expect respect

Fluid Imbalances

• Proper fluid balance is essential for homeostasis.

• Older adults have a higher risk due to age and health problems.

• Two major imbalances:

  • Hypovolemia (dehydration)

  • Hypervolemia (overhydration)

Hypovolemia (Dehydration)

• Occurs when fluid intake or retention is less than needed.

• Results in fluid volume deficit.

• Most common in:

  • Very young.

    • Children don’t think about drinking; they're more focused on play.

  • Elderly.

    • Lack of funds, ability, means or decline in taste and smell.

• Medications (e.g., diuretics) can cause fluid loss.

• Changes in mental status also contribute to fluid imbalances.

• Old folks forget or they have incontinence.

• Immobility plays a role.

• Cognitively impaired individuals don’t realize they're not drinking.

• Two forms:

  • Actual: Fluid loss from not taking in enough or getting rid of too much fluid.

  • Relative: Fluid shift inside the body, with vascular space moving to the interstitial space.

• Three forms of dehydration

  • Isotonic (most common): Water and electrolytes are lost equally in the vascular space

Dehydration Assessment

• History.

• Height and weight, which play an important role.

• A change in body weight is the best indicator of fluid loss or retention based on daily weights.

• Instruct to take daily weights at the same time using same clothes on the same scale.

• Complaints:

  • Ring and shoe tightness (fluid shifts to interstitial space).

  • Palpitations (heart compensates for fluid loss).

  • Lightheadedness (reduced oxygen to the brain).

  • Orthostatic hypotension.

• Abnormal fluid loss includes sweating.

  • Patients in controlled environment with excessive sweating means there's an underlying issue.

• Diarrhea (watery stools), vomiting, and polyuria can lead to dehydration.

• Measured: weight of dressing is measured before.
  They just weigh those diapers. There’s another that’s reason 5,644 not to work, little people.

• Therapies can include surgery.

• Diuretics, NPO status, hypertonic enemas.

• NG tube suctioning needs to be monitored.

• Check gastric residuals.

Dehydration Systems

• What happens to my body if I don't have enough fluid?

Cardiovascular:

• Increased heart rate as signals aren't receiving enough fluid.

• Pulse feels very thin i.e. "thready".

• Decreased blood pressure/orthostatic hypotension.

• Flat neck and hand veins in dependent positions.

• Diminished/absent pulses.

• The best place to check skin turgor is clavicular area, sternum, forehead.

• Weight loss (duh).

• Decreased central venous pressure.

Respiratory:

• Increased rate and depth of respirations.

• The body isn't getting enough O2 which means heart is overworking itself.

• Confusion if there’s no oxygen.

• Theory about oxygen: A little oxygen ain't never kill nobody. But not giving any has killing many.

Skin:

• Dry and scaly.

• Poor skin turgor tenting present (DO NOT check back of hand).

  • The older folks lose elasticity and they actually will tint even though they may still be adequately hydrated. The best place to do it, there's a couple places, clavicular area, sternum, forehead, never the back of the hand.

• Dry oral mucous membranes.

• Edema noted, make sure you note the pitting i.e. cankles.

Neurologically:

• Decreased central nervous system.

• Patients get lethargic/coma because the symptoms are similar.

• Mental status/kidney/tachycardias may occur.

• Neurologic chagnes may be an earlier sign that there's a fluid balance issue.

• Fever can quickly lead to dehydration.

• Every degree of elevation equals a minimum of 500 mL fluid loss.

Kidneys

• Indicate hydration status

• Volume
  Daily waste.

• Composition

  • Volume and composition

• Look at urine.

  • It smells

  • Color

• Monitor daily weights and intake/output. Daily waste.

  • Monitor daily weights and intake/output.

• Most accurate way for knowing fluid loss/gain are daily weights because: Insensible water loss i.e. breathing out fluid/poo we ain't measuring.

• Insensible water loss makes intake and output least accurate to daily weights because the insensible water loss.

Psychosocially:

• Black effect.

• Patients may become anxious/restless/confused.

• A flat affect is like monotone, doesn't show excitement or expression.

Labs

• There is no single lab or test to say OH YA this person has dehydration.

• Labs in association of the patient and there symptoms.
  Labs in association of the patient and symptoms.

• Labs will show: hemoconcentration because fluid balance is decreased

• Lab values are going to be extremely increased because hemocentration due to dehydration.

What do we need to do:

• Restore fluid balnce fluid replacements

• Isotonic solutions!

• Mild dehydration=increase fluid/foods to intake/fruits.

• Medications=correct the underlying causes.

  • Medication=hydrate!

  • antiemetic=hydrate!

  • Antipyretics=hydrate!

• Medication fever, hydrate. Because u loose 500ccs and the temperatures coming down!
  Antipyretics = Hydrate! Even when you have a fever they still hydrate.

Cardiac Output

• Decreased cardiac output because of dehydration.

• A stroke and heart rate that is been pump throughout. Decreased cardiac output because of dehydration:

  • Make sure you asses the heart rate, rhythm and quality. Which means actually putting on stethoscope on patients.
    How do we treat this due dehydration = *fluid replacements with isotonic.

• Need to look to see what medications are leading them into being dehydrated. diuretics -Medications that a patient may be taking: diuretics, anti- hypertensives Patients are already dehydrated, do we need to giving more stuff?

Impaired Oral Mucous Membranes, look at that mouth, it is dry!

• *Starting w/ IV *fluid replacement****.

• Salivia subs:

• Salivia substitutes a water based gel/jelly. Another use for the KY jelly, haha! Subs are:

  • KY but needs to have a repeated because temporary.
    Need to void a mouthwash and that have alcohol in them,

• Don’t take with alcohol cause going is dry more

• Avoid mouth to be too dry."