Fluid and Electrolyte Balance and Acid-Base Physiology
Dialogue Section
The conversation opens with inquiries about a photo and a reference to a bat mitzvah.
A parent mentions their daughter, and they reflect on a photo showcasing her with a side ponytail from when she was three years old.
Discussing the photo further, the family dynamic is hinted at, suggesting there is humor and warmth.
Upcoming Quiz Details
A quiz is scheduled for Tuesday focused on the topic of nutrition.
It consists of 10 questions based on material covered in previous discussions.
Topics unrelated to this quiz may not be covered in detail.
There is a mention of a review from Pathophysiology (Patho) about acids and bases that might contribute to the quiz content.
Body Fluid Basics
Importance of Water
Survival without food can last many days; however, survival without water is significantly shorter.
Body Water Composition
Total body water constitutes 50-60% of body weight in a normal, healthy adult.
Infants have a higher body fluid percentage compared to adults leading to increased risk for volume deficits.
Body water varies based on factors such as biological sex and fat content:
Women generally have less body water compared to men.
Lean tissue has a high water content, while fat cells contain minimal water.
Elderly individuals typically have a decreased water percentage in their bodies, causing risks for fluid deficits.
Fluid Balance and Electrolytes
Fluid balance between electrolytes and water occurs naturally via biological mechanisms.
The solution consists of:
Solvents (e.g., lipids) that hold a substance,
Solutes (e.g., sugar) that are dissolved in the solvent.
Example: In lemonade, sugar is the solute while water is the solvent.
Types of Fluid Loss
Sensible Loss
Sensible loss is measurable loss of body fluids such as urine.
Insensible Loss
Insensible loss cannot be measured, resulting from sweat and respiration.
Definitions of Fluid Imbalances
Hypovolemia: Decreased blood volume, specific to blood.
Dehydration: A broader term indicating a loss of body water or electrolytes; blood volume changes may not occur.
Third Spacing: Abnormal fluid movement from the intravascular space into interstitial spaces, causing potential fluid balance complications.
Ingestion of Fluids
Sources of Water
Primary sources of body water include:
Thirst Mechanism - located in the hypothalamus, triggered by dehydration and reduced blood volume.
Dietary Intake - Solid foods can be a source of water, with fruits containing more water than dry foods like cereal.
Metabolic Water - Water produced as a byproduct during the oxidative metabolism of food (approx. 300 ml).
Electrolyte Definitions
Electrolytes: particles that carry electrical charge; can be either cations (+) or anions (-).
Common cations include sodium (Na+), potassium (K+), calcium (Ca2+), hydrogen (H+), and magnesium (Mg2+).
Common anions include chloride (Cl-), bicarbonate (HCO3-), and phosphate (PO4^3-).
Major Electrolytes in Body Fluids
Sodium
Critical for extracellular fluid volume regulation.
Normal range: [135-145 ext{ mmol/L}].
Potassium
Essential for intracellular fluid regulation and nerve/muscle function.
Normal range: [3.5-5.0 ext{ mmol/L}].
Calcium
Most abundant electrolyte in the body, involved in neuromuscular function, muscle contraction, and blood coagulation.
Total serum calcium level normal range: [8.6-10.2 ext{ mg/dL}]; ionized calcium normal range: [4.5-5.1 ext{ mg/dL}].
Magnesium
Important for neuromuscular functions and cardiovascular health.
Normal range: [1.3-2.3 ext{ mg/dL}].
Bicarbonate
Key component in the body's primary buffer system, regulating acid-base balance.
Normal range: [25-29 ext{ mmol/L}].
Phosphates
Involved in energy storage and critical chemical reactions, with a normal range of [2.5-4.5 ext{ mg/dL}].
Homeostasis Organs
Kidneys: Filter plasma, maintain electrolyte levels, and regulate acid-base balance by excreting or retaining substances.
Cardiovascular System: Distributes nutrients and water; plays a role in fluid balance.
Lungs: Maintain pH through oxygen and carbon dioxide regulation, managing acid-base balance during respiration.
Pituitary Gland: Produces ADH, which facilitates water retention; excess ADH increases water retention.
Gastrointestinal System: Absorbs fluids during digestion.
Fluid Dynamics
Osmolarity of Solutions
Osmolarity: Concentration of particles in a solution influences fluid movement.
Isotonic Solutions: Equal concentration of solutes compared to plasma.
Hypertonic Solutions: Greater solute concentration than plasma; water moves out of cells, leading to cell shrinkage.
Hypotonic Solutions: Lower solute concentration than plasma; water moves into cells, potentially causing them to burst.
Principles of Fluid Movement
Osmosis: Water movement from low solute concentration to high concentration, aimed at achieving equilibrium.
Diffusion: Movement of molecules from high concentration to low concentration.
Active Transport: Movement against the concentration gradient using ATP.
Capillary Filtration: Involves pressure causing fluid movement from blood to surrounding tissues due to hydrostatic pressure.
Acid-Base Balance
Definitions
Acids: Substances that release hydrogen ions in solution.
Bases: Substances that can accept hydrogen ions.
pH Levels: Ranges 1 to 14, with normal physiological pH levels between [7.35-7.45].
Role of Buffers
Buffers prevent significant pH changes by either donating or absorbing hydrogen ions. There are three main buffer systems:
Carbonic Acid](H2CO3) / Sodium Bicarbonate (HCO3-) System: Most significant buffer system in the body, maintaining a 20:1 ratio.
Phosphate Buffer System: Operates primarily within intracellular fluid.
Protein Buffer System: Involves plasma proteins and hemoglobin that can adapt to changes in pH.
Respiratory and Renal Responses
Short-term regulation of acid-base status occurs via respiratory compensation, adjusting breathing rates to alter CO2 levels in blood.
Long-term regulation through renal mechanisms involves the kidneys excreting or retaining bicarbonate and hydrogen ions according to blood pH levels.
In acidosis, increased hydrogen ions compel the kidneys to retain bicarbonate.
In alkalosis, an excess of bicarbonate necessitates carbon dioxide retention by the lungs.