Irreversible Cell Injury Indicators: Toxicological Overload (Geriatric Update)

■ LECTURE OVERVIEW: Cell injury progresses through a reversible stage before crossing a critical biochemical boundary into irreversible cell injury and cell death. ■ THE CROSSING SEGMENTS: 1. Calcium Accumulation: Depletion of intracellular ATP disables membrane-bound ATP-dependent calcium pumps (Ca2+-ATPase). Calcium rushes into the cytosol and the mitochondria. 2. Enzymatic Overdrive: Elevated cytosolic calcium activates multiple destructive cytosolic enzymes: phospholipases (peroxidizing membranes), proteases (degrading structural cytoskeleton), endonucleases (fragmenting chromatin), and ATPases (further depleting remaining ATP). 3. Heavy Mitochondrial Vacuolization: Mitochondria undergo profound swelling, accumulation of amorphous, calcium-rich dense bodies in the matrix, and permanent loss of membrane potential. 4. Lysosomal Rupture: Low intracellular pH destabilizes lysosomes, releasing acid hydrolases into the cytosol, which digest organelles from within. 5. Nuclear Destruction: Follows a specific sequence: Pyknosis (nuclear condensation), Karyorrhexis (nuclear fragmentation), and Karyolysis (enzymatic disintegration of DNA). ■ TOXICOLOGICAL OVERDOSAGE PROTOCOL: Toxic absorption or cumulative exposure results in receptor saturation, chemical cell damage, or severe secondary target-organ failure. Immediate toxicological profiles dictate serum or urine screens. ■ GERIATRIC PHYSIOLOGIC ADJUSTMENTS: Older patients display reduced physiological reserves, altered muscle-to-fat distributions, and distinct renal filtration profiles. [HY-BOARD-1139]