Patho chapt 3 study guide

Fluid and Electrolyte Balance

• Body cells exist in a fluid environment requiring precise electrolyte and acid-base concentration.

• Balance achieved via renal, hormonal, and neural functions.

• Changes impact electrical activity in nerve and muscle cells, fluid shifts, and blood pressure.

• Disturbances can disrupt enzyme function, leading to cell injury and potential life-threatening conditions.

Distribution of Body Fluids

• Body fluids are distributed among compartments, crucial for cellular and tissue function.

• Two-thirds of body water is intracellular fluid (ICF); one-third is extracellular fluid (ECF).

• ECF has two primary compartments: interstitial fluid and intravascular fluid (blood plasma).

• Major transcellular fluids include synovial fluid, pleural fluid, pancreatic juice, etc.

• Total body water (TBW) for a 70-kg person is about 42 liters (60% body weight).

Water Sources and Loss

• Sources: drinking, food, water from metabolism.

• Major losses via urine, which accounts for the largest amount.

• Additional losses occur through skin and lungs (insensible loss).

• Normal daily intake and output ranges: 2400-3200 mL.

Age and Fluid Distribution

• TBW percentage varies with age; newborns have 70-80% body weight as water (high metabolic rate).

• Infants are especially susceptible to dehydration due to rapid fluid loss (e.g. diarrhea).

• Children’s TBW decreases to 60-65%; males develop higher body water percentages during adolescence.

• Older adults exhibit decreased TBW due to increased fat and decreased muscle mass, leading to complications under stress.

Water Movement Between Compartments

• Water moves primarily due to osmotic forces and hydrostatic pressure.

• Sodium regulates osmotic balance in ECF, potassium in ICF.

• Osmotic equilibrium is usually maintained unless there are rapid changes in ECF osmolality.

• Changes in plasma hydrostatic pressure affect fluid distribution between plasma and interstitial fluid, governed by four pressures (hydrostatic and oncotic).

Edema: Causes and Clinical Manifestations

• Edema: excess fluid in interstitial spaces, resulting from changes in filtration forces.

• Common mechanisms: increased capillary hydrostatic pressure, decreased oncotic pressure, and increased permeability.

• Can be localized or generalized, with risks including impaired nutrient delivery and oxygen transfer, increased pressure, and delayed wound healing.

Sodium, Chloride, and Water Balance

• Sodium and water balance are closely intertwined; sodium retention leads to water retention.

• Regulated primarily by hormones like aldosterone and natriuretic peptides.

• Primary sources of sodium excretion include kidneys, impacted by fluid changes.

Sodium and Chloride Concentrations

• Sodium levels typically range from 135 to 145 mEq/L; chloride levels proportional to sodium changes.

• Hyponatremia (Na+ < 135 mEq/L) results from loss of sodium or excess water.

• Hypernatremia (Na+ > 145 mEq/L) occurs with water loss or sodium retention, leading to cellular dehydration.

Alterations in Potassium Balance

• Potassium is critical for cell functions; balance influenced by aldosterone, insulin, and pH levels.

• Hypokalemia (< 3.5 mEq/L): due to low intake, losses, or increased movement into cells.

• Hyperkalemia (> 5.0 mEq/L): may arise from excessive intake, shifts out of cells, or kidney retention issues.

Calcium and Phosphate Balance

• Calcium essential for bone structure, muscle contraction, and neurotransmission; normal range: 9.0 to 10.5 mg/dL.

• Phosphate maintains cellular energy function and acid-base buffering.

• Both are regulated by parathyroid hormone (PTH), vitamin D, and calcitonin.

Acid-Base Balance

• Acid-base homeostasis controlled through respiratory and renal functions.

• pH reflects hydrogen ion concentration; normal blood pH is 7.35-7.45.

• Acidemia and alkalemia indicate necessary physiological adjustments.

• Various disorders (metabolic or respiratory) can induce pH imbalances that require systematic management.

Summary

• Body fluid distribution is critical for homeostasis involving multiple systems.

• Electrolyte and fluid balance are regulated by hormones and renal systems across different age groups.

• Understanding of fluid dynamics aids in recognizing and treating clinical conditions related to imbalances.