Nursing Pathophysiology: Fluids, Electrolytes, Cellular Pathology, Proliferation, Inflammation, and Tissue Repair

Fundamental Concepts of Body Fluids and Compartments

• Total Body Water (TBW) Composition

  • Water accounts for approximately $60\%$ of total body weight in a standard healthy adult.
  • Physiological factors influencing total body fluid status include age, biological sex, and proportion of body fat.
  • Adipose tissue contains significantly less water than skeletal muscle mass; therefore, individuals with higher body fat percentages possess lower relative total body water content.
  • Total body water progressively decreases with advancing age.

• Fluid Compartment Division

  • Intracellular Fluid Compartment (ICF)
  • Contains $2/3$ of total body water (representing approximately $40\%$ of total body weight).
  • Fluid resides entirely inside individual cells.
  • Principal intracellular electrolyte cations and anions include large amounts of Potassium ($\text{K}^+$), moderate amounts of Magnesium ($\text{Mg}^{2+}$), small amounts of Sodium ($\text{Na}^+$), Chloride ($\text{Cl}^-$), Bicarbonate ($\text{HCO}_3^-$), and Phosphorus ($\text{PO}_4^{3-}$), and virtually zero Calcium ($\text{Ca}^{2+}$).
  • Regulated by cell membrane permeability, specialized ion channels, and intracellular osmotically active organic solutes.
  • Cell membranes allow water to pass freely down osmotic gradients, while restricting solute passage.
  • Extracellular Fluid Compartment (ECF)
  • Contains $1/3$ of total body water (representing approximately $20\%$ of total body weight).
  • Fluid resides outside the cell membranes and is further subdivided into three distinct sub-compartments:
    • Plasma (Intravascular Space): Accounts for $5\%$ of total body weight ($1/4$ of ECF). Circulating blood fluid within blood vessels essential for transporting gases, nutrients, electrolytes, and metabolic wastes.
    • Interstitial Space: Accounts for $14\%$ of total body weight ($3/4$ of ECF). Fluid occupying the microscopic spaces between tissue cells and vascular walls.
    • Transcellular Space: Accounts for $1\%$ of total body weight. Fluid located in specialized lined body cavities (e.g., cerebrospinal, synovial, pericardial, intraocular, and peritoneal fluids).
  • Principal extracellular electrolyte constituents include large concentrations of Sodium ($\text{Na}^+$) and Chloride ($\text{Cl}^-$), moderate Bicarbonate ($\text{HCO}_3^-$), and minimal concentrations of Potassium ($\text{K}^+$), Magnesium ($\text{Mg}^{2+}$), Calcium ($\text{Ca}^{2+}$), and Phosphorus ($\text{PO}_4^{3-}$).
  • Routine serum laboratory blood tests measure chemical concentrations exclusively within the extracellular fluid compartment.

Dynamics of Fluid and Solute Movement

• Mechanisms of Transport

  • Diffusion
  • The passive movement of solute particles along a chemical concentration gradient from an area of higher particle concentration to an area of lower particle concentration until equilibrium is established.
  • Osmosis
  • The passive movement of water molecules across a semipermeable membrane down a concentration gradient from an area with lower solute concentration (more dilute solution) to an area with higher solute concentration (more concentrated solution).
  • Governed by non-penetrating, osmotically active particles that cannot freely cross the semipermeable cell membrane.
  • Osmotic Pressure
  • The exact hydrostatic or hydrostatic-equivalent force generated as water molecules move across a semipermeable membrane driven by solute concentration differences.
  • Osmolality
  • The total concentration of osmotically active particles expressed per kilogram of water ($\text{mOsm/kg}$).
  • Normal physiological serum osmolality reference range: $275 - 295\,\text{mOsm/kg}$.
  • Major contributors to serum osmolality include Sodium ($\text{Na}^+$), Chloride ($\text{Cl}^-$), Bicarbonate ($\text{HCO}_3^-$), Glucose, Blood Urea Nitrogen (Urea), and plasma proteins.

• Toxicity and Solution Tonicity

  • Tonicity refers to the effective osmotic pressure gradient established by non-penetrating solutes across a cell membrane, directly determining cell volume and shape.
  • Isotonic Solution
  • Possesses an effective osmolality equal to intracellular fluid ($275 - 295\,\text{mOsm/kg}$).
  • Intravenous administration produces zero net water shift across cell membranes; erythrocyte volume remains unchanged.
  • Hypertonic Solution
  • Possesses an effective osmolality higher than intracellular fluid ($>295\,\text{mOsm/kg}$).
  • Causes water to exit the intracellular compartment into the extracellular space via osmosis, resulting in cellular dehydration and cell shrinkage (crenation).
  • Hypotonic Solution
  • Possesses an effective osmolality lower than intracellular fluid ($<275\,\text{mOsm/kg}$).
  • Causes water to move from the extracellular compartment into the intracellular space via osmosis, leading to cellular swelling and potential cell lysis.

Capillary Fluid Exchange and Pathophysiology of Edema

• Starling Forces Governing Capillary Exchange
  • Capillary fluid movement regulates the continuous exchange of nutrients, dissolved gases, solutes, and fluid between the intravascular system and the interstitial spaces.
  • Capillary Filtration Pressure ($P_c$)
  • Hydrostatic pressure within the capillary lumen pushing water and dissolved solutes outward through capillary pores into the interstitial space.
  • Interstitial Fluid Hydrostatic Pressure ($P_{if}$)
  • Hydrostatic pressure exerted by fluid within tissue spaces opposing fluid movement out of capillaries.
  • Capillary Colloidal Osmotic Pressure (Plasma Proteins / $\Pi_p$)
  • Osmotic pull generated by plasma proteins (primarily albumin) that are too large to pass through capillary endothelial pores, drawing fluid back into the capillary vascular bed.
  • Tissue Colloidal Osmotic Pressure ($\Pi_{if}$)
  • Osmotic pull generated by small amounts of plasma proteins present in interstitial fluid, drawing water out of capillaries into tissue spaces.

• Etiology and Pathogenesis of Edema

  • Edema is defined as visible or non-visible palpable swelling caused by excessive accumulation of fluid within interstitial spaces.
  • $1\,\text{L}$ of accumulated fluid corresponds to an acute body weight increase of $1\,\text{kg}$ ($2.2\,\text{lbs}$).
  • Pathophysiological Mechanisms:
  • Increased Capillary Filtration Pressure
    • Caused by elevated arterial blood pressure, venous obstruction (e.g., thrombophlebitis), or capillary distention from intravascular fluid overload.
    • Driven by gravity, fluid accumulates preferentially in lower dependent extremities (dependent edema).
  • Decreased Capillary Colloidal Osmotic Pressure
    • Results from inadequate production or excessive loss of plasma proteins.
    • Plasma proteins are synthesized in the liver; hepatic disease reduces protein synthesis.
    • Plasma proteins are lost pathologically through impaired renal glomerular filtration (kidney disease) or extensive denuded skin injury (burns).
    • Because plasma proteins are evenly distributed in circulation, edema from decreased colloidal osmotic pressure causes generalized swelling affecting non-dependent tissues (e.g., facial or periorbital edema).
  • Increased Capillary Permeability
    • Endothelial damage from allergic reactions, trauma, or inflammation leads to mediator release (e.g., histamine), dilating capillary pores.
    • Plasma proteins leak freely into interstitial tissues, sharply increasing tissue colloidal osmotic pressure.
  • Obstruction of Lymphatic Flow (Lymphedema)
    • The lymphatic system normally reabsorbs excess tissue fluid and returns proteins to circulation.
    • Obstruction via surgical removal of lymph nodes (e.g., cancer resections), trauma, or infection prevents lymphatic return, resulting in chronic localized edema.

• Clinical Manifestations and Significance of Edema

  • Local vs. Generalized: Localized to specific organ/injury sites or generalized throughout the body (anasarca).
  • Life-Threatening Locations: Edema involving the brain, larynx, or pulmonary tissue impairs vital functions and is life-threatening.
  • Tissue Effects: Increases diffusion distances for oxygen, nutrients, and metabolic waste clearance; compresses local microvascular blood flow leading to tissue ischemia or acute compartment syndrome; impairs joint range of motion.
  • Third-Space Accumulation
  • Pathological sequestration of extracellular fluid in transcellular body cavities (e.g., pericardial effusion, pleural effusion, ascites in peritoneal cavity).
  • Trapped third-space fluid is functionally non-exchangeable and unavailable for metabolic processes or systemic blood pressure maintenance.

Systemic Fluid, Water, and Blood Pressure Regulation

• Body Water Balance and Daily Requirements

  • Standard physiological requirement: Approximately $1\,\text{mL}$ of pure water per $1\,\text{kcal}$ metabolized.
  • Primary fluid intake source: Oral consumption of liquids and solid foods.
  • Primary fluid elimination pathways: Renal excretion (urine), skin (perspiration/insensible loss), lungs (exhaled water vapor), and gastrointestinal tract (feces).
  • Even during complete fluid withholding, the kidneys continuously produce obligatory urine output to eliminate metabolic nitrogenous wastes.

• Systemic Regulatory Mechanisms

  • Thirst Mechanism
  • Regulated by the hypothalamus via osmoreceptors that detect micro-changes in ECF osmolality.
  • Stimulated by intracellular dehydration (increased ECF osmolality) or hypovolemia monitored by vascular baroreceptors.
  • A loss of $1\%$ of total body weight ($\approx 700\,\text{mL}$ of water) triggers the thirst sensation.
  • Thirst serves as an early clinical indicator of acute hemorrhage, appearing prior to overt blood pressure drops.
  • Baroreceptors
  • Stretch-sensitive mechanoreceptors in carotid sinuses and aortic arch sensing vascular wall tension and pressure fluctuations.
  • Decreased wall stretch activates the Sympathetic Nervous System (SNS).
  • Sympathetic Nervous System (SNS)
  • Increases heart rate, cardiac contractility, and induces arterial vasoconstriction to restore systemic blood pressure.
  • Renin-Angiotensin-Aldosterone System (RAAS)
  • Activated by decreased renal perfusion blood flow or low intravascular volume.
  • Renin converts angiotensinogen to angiotensin I, converted by ACE to angiotensin II (a potent vasoconstrictor), triggering adrenal cortical release of Aldosterone.
  • Aldosterone increases renal tubular Sodium reabsorption and Potassium excretion, expanding intravascular volume.
  • Antidiuretic Hormone (ADH / Vasopressin)
  • Synthesized in the hypothalamus, stored/released by posterior pituitary gland.
  • Release triggered by elevated ECF osmolality or decreased ECF fluid volume.
  • Acts on renal collecting ducts to increase water permeability and water reabsorption into blood.
  • Natriuretic Peptides (ANP and BNP)
  • Atrial Natriuretic Peptide (ANP) and Brain Natriuretic Peptide (BNP) are released from cardiac chambers in response to excessive cardiac wall stretch/volume overload.
  • Induce systemic vasodilation and inhibit renal sodium reabsorption, promoting fluid excretion in kidneys.
  • Gerontologic Considerations: Endogenous physiological fluid homeostatic mechanisms decline in sensitivity and efficiency with advancing age.

• Volume Imbalances

  • Fluid Volume Deficit (FVD)
  • Isotonic reduction of extracellular fluid volume affecting both interstitial and intravascular spaces.
  • Etiology: Gastrointestinal loss (vomiting, diarrhea), polyuria, profuse diaphoresis, acute hemorrhage, or inadequate intake (impaired thirst, lack of water access, unconsciousness, oral trauma).
  • Clinical Manifestations: Severe thirst, rapid weight loss, oliguria, prolonged capillary refill time ($>2\,\text{seconds}$), decreased skin turgor, flat neck veins, orthostatic hypotension.
  • Fluid Volume Excess (FVE)
  • Isotonic expansion of extracellular fluid in both interstitial and vascular compartments caused by sodium retention accompanied by proportional water expansion.
  • Etiology: Renal failure, congestive heart failure, hepatic cirrhosis, or iatrogenic fluid administration.
  • Clinical Manifestations: Bounding peripheral pulses, acute weight gain, Jugular Venous Distention (JVD), shortness of breath (SOB), dyspnea, moist pulmonary cough, peripheral edema.

Clinical Pathophysiology of Electrolyte Disturbances

• Sodium ($\text{Na}^+$) Homeostasis

  • Normal reference range: $135 - 145\,\text{mEq/L}$.
  • Most abundant extracellular cation; primary determinant of ECF volume and serum osmolality.
  • Minimum physiological intake requirement: $500\,\text{mg/day}$. Excreted $90\%$ by kidneys, $10\%$ via GI/skin.
  • Hyponatremia ($<135\,\text{mEq/L}$)
  • Caused predominantly by water retention (dilutional hypotonic state) or sodium loss.
  • Subtypes: Hypovolemic (loss of water and sodium: hypoaldosteronism, burns, diaphoresis, vomiting, diarrhea, tap water enemas), Euvolemic (normal ECF volume: SIADH, MDMA/ecstasy toxicity), Hypervolemic (increased ECF volume: heart failure, liver failure, renal disease).
  • Clinical Manifestations: Serum osmolality $<275\,\text{mOsm/kg}$, lab hemodilution (decreased H&H and BUN), anorexia, nausea, vomiting, abdominal cramps, diarrhea, muscle cramps, weakness, apprehension, headache, lethargy, confusion, personality changes, stupor, coma, seizures.
  • Hypernatremia ($>145\,\text{mEq/L}$)
  • Caused by hypertonic sodium gain or excessive free water loss.
  • Subtypes: Excessive water loss (diarrhea, sweating, tachypnea, hypertonic tube feeds, Diabetes Insipidus), decreased water intake, hypertonic saltwater ingestion.
  • Clinical Manifestations: Serum osmolality $>295\,\text{mOsm/kg}$, intense polydipsia, oliguria/anuria, extracellular dehydration (tachycardia, hypotension), intracellular dehydration (dry mucous membranes, poor skin turgor, decreased salivation/tearing), agitation, restlessness, headache, seizures, coma.

• Potassium ($\text{K}^+$) Homeostasis

  • Normal reference range: $3.5 - 5.0\,\text{mEq/L}$.
  • Major intracellular cation; crucial for resting membrane potentials, cardiac conduction, neural impulse transmission, and muscle contraction.
  • Hypokalemia ($<3.5\,\text{mEq/L}$)
  • Etiology: Inadequate intake, excess GI loss (vomiting, diarrhea, GI suction), excess renal loss (diuretics, hyperaldosteronism, hypomagnesemia, alkalosis), alkalosis-driven intracellular shifts, insulin excess.
  • Clinical Manifestations: Metabolic alkalosis, hypotension, characteristic ECG changes, CARDIAC DYSRHYTHMIAS, confusion, depression, anorexia, nausea, vomiting, constipation, abdominal distention, paralytic ileus, muscle weakness, fatigue, cramps, paresthesias, flaccid paralysis, impaired renal urine concentrating ability, polyuria.
  • Hyperkalemia ($>5.0\,\text{mEq/L}$)
  • Etiology: Decreased renal excretion (renal failure, metabolic acidosis, hypoaldosteronism, potassium-sparing medications), excessive oral/IV intake, cellular shifts (acidosis, severe burns, tissue trauma, extreme exercise).
  • Clinical Manifestations: Metabolic acidosis, hypotension, ECG changes, CARDIAC DYSRHYTHMIAS, GI hypermotility, abdominal cramps, diarrhea, early paresthesias, progressive muscle weakness, flaccid paralysis.

• Calcium ($\text{Ca}^{2+}$) Homeostasis

  • Normal reference range: $8.5 - 10.5\,\text{mg/dL}$.
  • $99\%$ deposited in bone matrix; $1\%$ in ECF/ICF ($40\%$ bound to plasma albumin, $50\%$ free/ionized, $10\%$ complexed).
  • Free ionized calcium regulates neuronal excitability, membrane potentials, muscle contraction, cardiac automaticity, and blood coagulation cascade.
  • Hypocalcemia ($<8.5\,\text{mg/dL}$)
  • Etiology: Hypoparathyroidism, hypomagnesemia, vitamin D deficiency, intestinal malabsorption, renal failure, hyperphosphatemia, rapid citrated blood transfusions, alkalosis (increased protein binding), acute pancreatitis (soft tissue sequestration).
  • Clinical Manifestations: Cardiac dysrhythmias, hypotension, paresthesias, painful skeletal muscle cramps, hyperactive deep tendon reflexes, tetany, laryngeal spasm, bone pain, osteomalacic fractures.
  • Hypercalcemia ($>10.5\,\text{mg/dL}$)
  • Etiology: Hyperparathyroidism, bone malignancies, prolonged immobilization, excess Vit D/calcium intake, medications (thiazide diuretics).
  • Clinical Manifestations: Hypertension, ECG changes, lethargy, personality/behavioral changes, stupor, coma, anorexia, nausea, vomiting, constipation, muscle weakness, muscle atrophy, ataxia, osteopenia/osteoporosis, renal calculi, flank pain.

• Phosphorus ($\text{PO}_4^{3-}$) Homeostasis

  • Normal reference range: $2.5 - 4.5\,\text{mg/dL}$.
  • $85\%$ in bone, $14\%$ intracellular, $1\%$ extracellular. Essential for ATP synthesis, DNA/RNA, cell membrane phospholipids, acid-base buffering, and phagocytic blood cell function. Maintains an inverse relationship with calcium.
  • Hypophosphatemia ($<2.5\,\text{mg/dL}$)
  • Etiology: Decreased intestinal absorption (diarrhea, Vit D deficiency), elevated renal elimination (alkalosis, hyperparathyroidism, DKA), malnutrition, chronic alcoholism, refeeding syndrome (IV glucose / insulin administration).
  • Clinical Manifestations: Impaired leukocyte/platelet function, hemolytic anemia, bone pain, joint stiffness, muscle weakness, paresthesias, confusion, stupor, coma, seizures, ataxia, secondary hypercalcemia.
  • Hyperphosphatemia ($>4.5\,\text{mg/dL}$)
  • Etiology: Impaired renal excretion (renal failure, hypoparathyroidism), phosphorus-containing laxatives/enemas, cellular destruction (trauma, heatstroke, seizures, rhabdomyolysis).
  • Clinical Manifestations: Hypotension, cardiac dysrhythmias, paresthesias, tetany, secondary hypocalcemia.

• Magnesium ($\text{Mg}^{2+}$) Homeostasis

  • Normal reference range: $1.8 - 2.6\,\text{mg/dL}$.
  • $50-60\%$ in bone, $40-50\%$ intracellular, $1\%$ extracellular. Essential cofactor for enzymatic reactions, ATP energy metabolism, $\text{Na}^+/\text{K}^+$ ATPase pump regulation, and parathyroid hormone (PTH) release.
  • Hypomagnesemia ($<1.8\,\text{mg/dL}$)
  • Etiology: Malnutrition, starvation, chronic alcoholism, TPN without magnesium, bowel bypass surgery, malabsorption, renal losses (diuretics, hyperaldosteronism, hyperparathyroidism, DKA).
  • Clinical Manifestations: Cardiac dysrhythmias, hypertension, tachycardia, neuromuscular tetany, personality changes, nystagmus.
  • Hypermagnesemia ($>3.0\,\text{mg/dL}$)
  • Etiology: Excessive intake (magnesium antacids/supplements/IV infusions), severe renal failure.
  • Clinical Manifestations: Cardiac dysrhythmias, cardiac arrest, hypotension, profound lethargy, hyporeflexia (diminished deep tendon reflexes), confusion, coma.

Patterns of Cellular Adaptation

• Overview of Adaptation

  • Cells respond to physiological or pathological environmental alterations by changing in size, cell number, or cellular phenotype/type.
  • Adaptive changes represent normal physiological responses when responding to appropriate bodily stimuli.

• Cellular Adaptations in Size

  • Atrophy
  • Decrease in cell size, leading to reduced functional tissue mass, diminished oxygen consumption, and reduced metabolic demands.
  • Primary Causes: Disuse (e.g., cast immobilization), denervation (loss of neural innervation), loss of endocrine stimulation (e.g., menopause), inadequate nutrition, and ischemia (decreased blood flow).
  • Hypertrophy
  • Increase in individual cell size resulting in expanded functioning tissue mass.
  • Predominantly observed in non-dividing muscle tissues (cardiac and skeletal muscle) exposed to increased hemodynamic or mechanical workloads.
  • Physiologic Hypertrophy: Increased muscle mass associated with exercise/weight training.
  • Pathologic Hypertrophy: Result of underlying disease state. Can be adaptive (e.g., left ventricular hypertrophy secondary to systemic hypertension) or compensatory (e.g., enlargement of remaining kidney tissue following a surgical nephrectomy).

• Cellular Adaptations in Number

  • Hyperplasia
  • Increase in the total number of cells within an organ or tissue through active mitotic cell division.
  • Limited to tissue types capable of mitotic division (epidermis, intestinal epithelium, glandular tissue).
  • Physiologic Hyperplasia: Hormonal (e.g., breast tissue expansion and uterine hypertrophy/hyperplasia during pregnancy) or Compensatory (e.g., liver regeneration following partial hepatectomy).
  • Non-Physiologic Hyperplasia: Uncontrolled cellular proliferation caused by excessive hormonal stimulation or growth factors (e.g., benign prostatic hyperplasia [BPH], skin warts caused by papillomaviruses). Promotes risk for neoplastic transformation.

• Other Phenotypic Cellular Adaptations

  • Metaplasia
  • Reversible conversion where one adult cell type is replaced by another adult cell type of the same primary tissue class.
  • Involves reprogramming of undifferentiated stem cells triggered by chronic inflammation or continuous irritation, substituting fragile cells with tougher cell phenotypes.
  • Classic Example: Replacement of fragile pseudostratified ciliated columnar respiratory epithelium with stratified squamous epithelium in chronic tobacco smokers.
  • Dysplasia
  • Deranged cellular growth resulting in cells that vary significantly in size, shape, nuclear morphology, and structural organization.
  • Strongly associated with chronic physical irritation or inflammation. Highly adaptive and potentially reversible if the injurious stimulus is removed.
  • Clinical Significance: Strongly implicated as an obligate precursor to cancer (e.g., cervical dysplasia preceding cervical carcinoma).
  • Intracellular Accumulations
  • Abnormal accumulation of substances within cells that cannot be instantly processed or excreted.
  • Substrates: Normal endogenous substances (lipids, proteins, bilirubin), abnormal endogenous metabolic products (genetic storage disorders), or exogenous materials (tattoo pigments, inhaled silica, lead).
  • Pathologic Calcifications
  • Abnormal tissue deposition of calcium salts, iron, magnesium, and minerals (e.g., dystrophic calcification of damaged aortic cardiac valves).

Etiology and Mechanisms of Cellular Injury

• Determinants of Injury

  • The severity and reversibility of cellular injury depend upon: intensity and duration of the agent, cell type and metabolic requirements, local blood supply, cellular nutritional status, and inherent regenerative capacity.

• Etiological Causes of Injury

  • Physical Agents
  • Mechanical Forces: Impact trauma severing tissues, fracturing bones, disrupting blood flow.
  • Thermal Extremes: Intense heat coagulates blood vessels and denatures cellular proteins; extreme cold increases blood viscosity, induces severe vasoconstriction, and causes localized tissue hypoxia/frostbite.
  • Electrical Injury: Tissue disruption and thermal destruction caused by electric currents. Extent depends on voltage, amperage, current type (AC/DC), tissue resistance, contact duration, and current pathway through the body. Maximum tissue necrosis occurs at entrance and exit sites.
  • Radiation Injury
  • Ionizing Radiation: Directly breaks intracellular chemical bonds and hydrolyzes water, generating toxic free radicals. Immediately kills cells, impairs DNA replication, or induces carcinogenic mutations. Rapidly dividing cells (bone marrow, GI mucosa) are most vulnerable.
  • Ultraviolet Radiation: Causes sunburn, cellular membrane damage, and pyrimidine dimer formation in nuclear DNA, raising skin cancer risk.
  • Chemical Injury
  • Direct or indirect chemical disruption of membrane integrity or metabolic pathways.
  • Pharmaceuticals (e.g., acetaminophen/Tylenol overdose induces toxic metabolite accumulation causing severe hepatotoxicity; heavy metals like lead injure central nervous system structures).
  • Biologic Agents
  • Replicating pathogenic microorganisms (viruses, bacteria, fungi, parasites) that continuously synthesize exotoxins, endotoxins, or induce destructive immune responses.
  • Nutritional Imbalances
  • Starvation/malnutrition (protein/calorie deficiency), vitamin deficiencies, or severe obesity/nutrient excess.

• Pathophysiological Mechanisms of Cell Injury

  • Free Radical Injury
  • Driven by reactive oxygen species (ROS)—highly reactive chemical species containing an unpaired electron in an outer orbit.
  • ROS react destructively with cell components, inducing lipid peroxidation of cell membranes, inactivating intracellular enzymes, and damaging nuclear DNA.
  • Hypoxic Cell Injury
  • The single most common mechanism of cellular injury.
  • Hypoxia deprives cells of oxygen, interrupting mitochondrial oxidative phosphorylation and suppressing Adenosine Triphosphate (ATP) production.
  • Etiologies: Reduced atmospheric oxygen, respiratory disease, anemia, severe edema, cellular inability to utilize oxygen (cyanide toxicity), and Ischemia (impaired arterial blood delivery and impaired venous removal of metabolic wastes).
  • **The Cascade of Hypoxic