In irreversible shock, the critical event leading to cell death is the rupture of lysosomal membranes, resulting in the release of lysosomal enzymes into the cytoplasm. These enzymes degrade essential cellular components, causing extensive autodigestion and necrosis. Unlike reversible injury, where mitochondrial swelling and decreased ATP are initial reversible events, the enzymatic destruction by lysosomal contents is irreparable and definitive. Therefore, lysosomal enzyme release is the primary mechanism driving irreversible cell injury and death in shock.

Reference: Robbins Basic Pathology, Kumar, Abbas, Aster, 10th Edition.