Disease States 1 - Chapter 3: Distribution of body fluids and acid-base balance

Vocabulary flashcards covering body fluid compartments, fluid movement, edema mechanisms, electrolyte balance, and acid-base regulation.

Total body water (TBW)

The sum of fluids in all body compartments; normally about 60% of body weight in adults; higher in newborns (70–80%).

Extracellular fluid (ECF)

Fluid outside cells; ~1/3 of TBW; compartments include interstitial fluid, intravascular (plasma), and transcellular fluids.

Intracellular fluid (ICF)

Fluid inside cells; ~2/3 of TBW.

Interstitial fluid

Fluid in the spaces between cells (part of ECF).

Intravascular fluid

Fluid within blood vessels (plasma).

Transcellular fluids

Fluids in epithelial-lined cavities (pleural, synovial, peritoneal, pericardial, intraocular, etc.).

Newborn TBW percentage

Newborns have TBW of about 70–80% of body weight; higher evaporative losses and metabolism influence fluid needs.

Fat and TBW

Adipose tissue contains little water; more body fat means less TBW and greater risk of dehydration.

Aquaporins

Water channel proteins that facilitate water movement across cell membranes.

Osmosis

Movement of water across a semipermeable membrane toward higher solute concentration to equalize osmolality.

Osmolality

A measure of solute concentration, expressed as mOsm/kg; normal range ~275–295 mOsm/kg.

Normal osmolality range

Approximately 275–295 mOsm/kg.

Sodium (Na+)

Primary extracellular cation; helps maintain osmotic balance; normal serum 135–145 mEq/L.

Potassium (K+)

Primary intracellular cation; important for membrane potential and function; normal serum 3.5–5.0 mEq/L.

Albumin

Major plasma protein produced by the liver; maintains capillary oncotic pressure (colloid osmotic pressure).

Oncotic pressure (colloid osmotic pressure)

Pressure exerted by plasma proteins (primarily albumin) to pull water into capillaries.

Capillary hydrostatic pressure (HPc)

Hydrostatic pressure in capillaries that pushes fluid out into the interstitial space.

Interstitial hydrostatic pressure (HPif)

Hydrostatic pressure within the interstitial space (opposes capillary filtration).

Interstitial oncotic pressure (OPif)

Oncotic pressure in the interstitial space that can pull water out of capillaries.

Capillary oncotic pressure (OPc)

Oncotic pressure inside capillaries that tends to pull water from interstitium into capillaries.

Filtration

Movement of fluid out of the capillary into the interstitial space.

Absorption

Movement of fluid from the interstitial space back into the capillary.

Net filtration pressure (NFP)

NFp = (HPc + OPif) – (HPif + OPc); positive means filtration, negative means reabsorption.

Edema

Excess accumulation of fluid in the interstitial spaces.

Edema mechanisms

Increased capillary hydrostatic pressure, decreased plasma oncotic pressure, increased capillary permeability, and lymphatic obstruction.

Lymphatic system / lymphedema

Lymphatic system drains interstitial fluid; obstruction can cause lymphedema (chronic swelling).

Isotonic

ECF volume increases or decreases with no net change in osmolality (normal tonicity, e.g., 0.9% NaCl).

Hypertonic

ECF osmolality rises above normal, causing cells to shrink.

Hypotonic

ECF osmolality falls below normal, causing cells to swell.

Sodium normal range

135–145 mEq/L.

Chloride normal range

96–106 mEq/L.

Bicarbonate (HCO3-)

A major bicarbonate buffer; normal ~22–26 mEq/L; balances H2CO3 in acid-base balance.

Anion gap

Difference between measured cations and measured anions; cation - anion

Hypernatremia

Serum Na+ >145 mEq/L; often reflects water loss or sodium gain; can cause cellular dehydration and neurologic symptoms.

Hyponatremia

Serum Na+ <135 mEq/L; common in hospitalized patients; various etiologies (hypovolemic, euvolemic, hypervolemic).

Hyperkalemia

Potassium >5.0 mEq/L; risk of arrhythmias; causes include increased intake, shift from ICF to ECF, decreased excretion.

Hypokalemia

Potassium <3.5 mEq/L; can cause weakness, arrhythmias, and neuromuscular symptoms; often due to losses or shifts.

Calcium

Normal serum Ca2+ ~8.4–10.6 mg/dL; essential for bones, clotting, nerve and muscle function.

Parathyroid hormone (PTH)

Hormone that increases plasma Ca2+ by increasing kidney reabsorption and bone resorption.

Vitamin D

Fat-soluble vitamin that increases intestinal Ca2+ absorption.

Calcitonin

Hormone that lowers plasma Ca2+ by inhibiting bone resorption.

Phosphate

Bone-associated anion; normal ~2.5–4.5 mg/dL; involved in high-energy bonds (ATP, creatine phosphate).

Magnesium (Mg2+)

Intracellular cation; normal ~1.3–2.1 mEq/L; essential for NM conduction; dysregulation affects neuromuscular function.

Acid-base balance

Regulation of pH through buffers, lungs, and kidneys; normal arterial pH 7.35–7.45.

Buffer systems

Buffering pairs that resist pH change (bicarbonate–carbonic acid, phosphate, hemoglobin, protein systems).

Arterial pH

7.35–7.45.

Compensation (acid-base)

Physiologic adjustments (respiratory or renal) to counteract a primary acid-base disorder.

Metabolic acidosis

Decreased HCO3- or increased non-carbonic acids; causes include lactic acidosis, DKA, renal failure; often with compensatory hyperventilation.

Metabolic alkalosis

Elevated HCO3-; causes include vomiting, gastric suctioning, diuretic use; often with compensatory hypoventilation.

Respiratory acidosis

pH

Respiratory alkalosis

pH >7.45 with PaCO2 <38 mm Hg; hyperventilation; compensation by kidneys decreasing bicarbonate.

Buffer systems: bicarbonate–carbonic acid

Extracellular buffer pair; central to acid-base balance with a 20:1 bicarbonate to carbonic acid ratio.

Mixed acid-base disorders

Two or more simultaneous primary acid-base disorders, common in hospitalized patients.

Net filtration

the process of fluid movement across capillary membranes, influenced by hydrostatic and osmotic pressures, determining fluid balance in tissues.

HPc

Capillary hydrostatic pressure (blood pressure pushing)

OPif

Osmotic pressure from interstitial fluid; it opposes capillary filtration.

OPc

Osmotic pressure from plasma; it promotes capillary filtration by drawing water into the capillaries. (opposing filtration)

HPif

Interstitial hydrostatic pressure( water pushing; it opposes hydrostatic pressure.

The major forces lie within the capillary

Capillary hydrostatic pressure ( HPc); Capillary (plasma) onccotic (osmotic) pressure

capillary hydrostatic pressure

the pressure exerted by fluid within the capillaries, promoting filtration of fluid out of the capillaries into the interstitial space.

edema

excessive accumulation of fluid within interstitial space

Most adudant cation in ICF

potassium (K+)

Most abundant cation in ECF

sodium (Na+)

rigor mortis

the stiffening of muscles after death due to chemical changes in the body.

liver mortis

the pooling of blood in the lowest parts of the body after death, resulting in a discoloration of the skin. (redish purple discoloration of skin after death)

Cellular adaptation

reversible response to sustain homeostasis