2535 W23 FEAB final ppt week 4 knowt

Fluid, Electrolytes, & Acid-Base Balance

Overview

• Physiology Review: Key concepts include understanding fluids and electrolytes.

• Fluid & Electrolyte Imbalances: Mechanisms causing imbalances in the body.

• Acid-Base Balance: Importance of maintaining pH levels.

Homeostasis

• Definition: A state of equilibrium in the body maintained by adaptive responses.

• Maintained by: Body fluids and electrolytes are kept within narrow limits to support vital functions.

Water Content of the Body

• Percentage of Body Weight:

  • Adults: 50% - 60%

  • Older Adults: 45% - 55%

  • Infants: 70% - 80%

• Variations Based On: Gender, body mass, and age.

Total Body Water (TBW)

• Composition:

  • 60% of the adult body is water.

  • Extracellular Fluid (ECF): 1/3 of TBW.

  • Intracellular Fluid (ICF): 2/3 of TBW.

  • Plasma Volume (PV): 1/3 of ECF.

  • Interstitial Fluid (ISF): 2/3 of ECF.

Electrolytes

• Definition: Substances that dissociate into ions in water.

• Types:

  • Cations: Positively charged ions (e.g., Na+, K+).

  • Anions: Negatively charged ions (e.g., Cl−, PO4³−).

• Measurement: International standard is millimoles per liter (mmol/L).

Electrolyte Composition

• ICF (Intracellular Fluid):

  • Cation: K+ (Potassium).

  • Anion: PO4³− (Phosphate).

• ECF (Extracellular Fluid):

  • Cation: Na+ (Sodium).

  • Anion: Cl− (Chloride).

Mechanisms Controlling Fluid and Electrolyte Movement

1. Diffusion: Movement from high to low concentration without energy.

2. Facilitated Diffusion: Uses carrier molecules but still no energy required.

3. Active Transport: Movement against concentration gradient requiring energy (e.g., sodium-potassium pump).

4. Osmosis: Movement of water across a selectively permeable membrane.

5. Hydrostatic Pressure: Force pushing water out of the vascular system.

6. Oncotic Pressure: Osmotic pressure exerted by colloids in solution, significant with proteins.

Fluid Exchange and Movement

• Fluid Movement in Capillaries: Determined by hydrostatic and oncotic pressures.

• Fluid Shifts: Changes in hydrostatic or oncotic pressure lead to edema or fluid retention in tissues.

• Regulation: Mechanisms involve renal, cardiac and hormonal responses to fluid imbalances.

Fluid and Electrolyte Imbalances

• Common in patients with significant illness (e.g., heart failure).

• ECF Volume Imbalances:

  • Hypovolemia: Loss of body fluids (e.g., diarrhea).

  • Hypervolemia: Excess fluid retention.

• Electrolyte Disorders:

  • Sodium imbalances (e.g., hypernatremia, hyponatremia).

  • Potassium imbalances (e.g., hyperkalemia, hypokalemia).

  • Calcium, magnesium, and phosphate imbalances also affect body functions.

Acid-Base Balance

• Normal Blood pH: Ranges from 7.35 to 7.45, essential for physiological functions.

• Buffer Systems: Include carbonic acid-bicarbonate buffer to maintain pH.

• Acidosis and Alkalosis:

  • Caused by metabolic or respiratory issues affecting H+ concentrations.

  • Types of imbalances: Respiratory acidosis, respiratory alkalosis, metabolic acidosis, metabolic alkalosis.

Acid-Base Imbalances

• Assessment Methods: Arterial blood gas (ABG) sampling for actual pH.

• Management: Corrective measures depend on underlying causes of imbalances.