Rubor, calor, tumor, dolor and functio laesa
Mnemonic
The four of Celsus, with Galen’s fifth:
- Rubor - redness, from vasodilatation
- Calor - heat, from increased blood flow
- Tumor - swelling, from increased vascular permeability and exudate
- Dolor - pain, from bradykinin and prostaglandins, and pressure
- Functio laesa - loss of function, added by Galen
“Red, hot, swollen, painful, and it does not work.”
Each maps onto a mechanism, which is why the list is more than a mnemonic: vasodilatation comes from histamine, prostaglandins and nitric oxide; permeability from histamine and bradykinin acting on venules; pain from bradykinin and prostaglandin E2, which is precisely what NSAIDs block by inhibiting cyclooxygenase.
The acute response is neutrophil driven and lasts hours to days; the chronic response is lymphocyte and macrophage driven, with tissue destruction and repair proceeding simultaneously, which is why chronic inflammation causes fibrosis.
Expansion
- Rubor (redness): vasodilatation of arterioles, mediated by histamine, prostaglandins and nitric oxide
- Calor (heat): increased blood flow bringing core temperature to the surface
- Tumor (swelling): increased vascular permeability producing a protein-rich exudate
- Dolor (pain): bradykinin and prostaglandins sensitising nerve endings, plus pressure from the swelling
- Functio laesa (loss of function): the fifth sign, added by Virchow
The vascular sequence is: transient vasoconstriction, then vasodilatation with increased flow, then increased permeability causing stasis, then leucocyte margination and emigration.
Exudate versus transudate is the key distinction. An exudate is protein-rich with a high specific gravity and cells, resulting from increased permeability; a transudate is protein-poor, resulting from altered hydrostatic or oncotic pressure. Light’s criteria apply this distinction to pleural fluid.
Anti-inflammatory drugs act on the mediators: NSAIDs on prostaglandins, antihistamines on histamine, corticosteroids on phospholipase A2 and on gene transcription more broadly.