[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Environmental pathology](https://durgical.com/en/general-pathology/#a-environment) › Thermal injury: burns, hyperthermia and hypothermia [General pathology](https://durgical.com/en/general-pathology/) · [Environmental pathology](https://durgical.com/en/general-pathology/#a-environment) # Thermal injury: burns, hyperthermia and hypothermia - Mechanism Too much heat or cold destroys skin and tissue and, when the whole body is affected, can cause shock, organ failure or arrhythmias. Updated 2026-11-01 ## Key points - Full-thickness burns are painless because nerve endings are destroyed. - Burn shock comes from generalised capillary leak; infection of the eschar (Pseudomonas) is a main cause of late death. - Inhalation injury: airway oedema plus carbon monoxide and cyanide. - Curling ulcer: acute gastric or duodenal ulcer after severe burns. - Hypothermia ECG: Osborn J waves. ## What it is Local heat coagulates proteins of the skin, and depth decides healing. Large burns cause fluid loss, hypermetabolism, infection and inhalation injury. Whole-body heat (heat stroke) or cold (hypothermia) overwhelms thermoregulation and injures every cell. Burns are a major cause of disability in low- and middle-income countries. ## Key facts - Heat stroke: core temperature rises with brain dysfunction; it leads to rhabdomyolysis, DIC, kidney and liver failure. - Malignant hyperthermia is genetic (RYR1) and triggered by inhaled anaesthetics and succinylcholine. - Hypothermia slows the heart, causes Osborn (J) waves and can end in ventricular fibrillation. - Frostbite: ice crystals form in tissue, endothelium is injured and small vessels thrombose. - A chronic burn scar can develop squamous cell carcinoma (Marjolin ulcer). ## Step by step - Heat coagulates proteins of the epidermis and dermis: a zone of necrosis surrounded by a zone of poor blood flow. - Mediators released by the burn make capillaries leaky in the whole body. - Plasma leaves the vessels: oedema, haemoconcentration and hypovolaemic shock (burn shock). - Hypermetabolism follows: high catecholamines, muscle breakdown and poor healing. - The dead, avascular eschar is easily infected, classically by Pseudomonas aeruginosa: sepsis. - Inhaled hot gases and smoke cause airway oedema and carbon monoxide and cyanide poisoning. ## Burn depth | Depth | Layers involved | Appearance | Healing | | --- | --- | --- | --- | | [Superficial](https://durgical.com/en/conditions/burns/) | Epidermis only | Red, dry, painful, no blisters | Heals without scar | | [Superficial partial thickness](https://durgical.com/en/conditions/burns/) | Epidermis and upper dermis | Blisters, moist, very painful, blanches | Heals from adnexa, little scar | | [Deep partial thickness](https://durgical.com/en/conditions/burns/) | Epidermis and deep dermis | Pale, less painful, blanches poorly | Slow; often needs grafts; hypertrophic scar | | [Full thickness](https://durgical.com/en/conditions/burns/) | Whole dermis and beyond | White, leathery or charred, painless | Needs grafts; contractures | ## Memory aid Depth decides the burn's fate; surface area decides the patient's. ## Test yourself Think of the answer, then tap the question to see it. ## Why is a full-thickness burn painless? The whole dermis, including its nerve endings, has been destroyed. ## Which organism classically infects burn wounds and causes sepsis? Pseudomonas aeruginosa, which thrives on the moist, avascular eschar. ## What mutation underlies malignant hyperthermia? Usually RYR1, the calcium release channel of skeletal muscle; anaesthetics trigger uncontrolled calcium release. ## What is a Marjolin ulcer? A squamous cell carcinoma arising in a chronic burn scar or other long-standing wound. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/general-pathology/thermal-injury-burns-hyperthermia-and-hypothermia/) ## Related - [Shock: types, stages and the organs it damages](https://durgical.com/en/general-pathology/shock-types-stages-and-the-organs-it-damages/) - [Abnormal repair: chronic wounds, hypertrophic scar, keloid, contracture](https://durgical.com/en/general-pathology/abnormal-repair-chronic-wounds-hypertrophic-scar-keloid-contracture/) - [Healing of skin wounds: first and second intention](https://durgical.com/en/general-pathology/healing-of-skin-wounds-first-and-second-intention/) - [Mechanical and electrical injury: abrasion, contusion, laceration, wounds](https://durgical.com/en/general-pathology/mechanical-and-electrical-injury-abrasion-contusion-laceration-wounds/) - [Health effects of climate change](https://durgical.com/en/general-pathology/health-effects-of-climate-change/) ## Related conditions - [Burns (thermal, chemical, electrical; inhalation injury)](https://durgical.com/en/conditions/burns/) - [Heat stroke and heat exhaustion](https://durgical.com/en/conditions/heat-stroke-and-heat-exhaustion/) - [Accidental hypothermia](https://durgical.com/en/conditions/accidental-hypothermia/) - [Frostbite](https://durgical.com/en/conditions/frostbite/) - [Malignant hyperthermia](https://durgical.com/en/conditions/malignant-hyperthermia/) - [Neuroleptic malignant syndrome](https://durgical.com/en/conditions/neuroleptic-malignant-syndrome/) - [Rhabdomyolysis](https://durgical.com/en/conditions/rhabdomyolysis/) - [Disseminated intravascular coagulation](https://durgical.com/en/conditions/disseminated-intravascular-coagulation/) - [Hypovolaemic shock](https://durgical.com/en/conditions/hypovolaemic-shock/) - [Carbon monoxide poisoning](https://durgical.com/en/conditions/carbon-monoxide-poisoning/) - [Keloid and hypertrophic scar](https://durgical.com/en/conditions/keloid-and-hypertrophic-scar/) - [Cutaneous squamous cell carcinoma](https://durgical.com/en/conditions/cutaneous-squamous-cell-carcinoma/) ## Elsewhere in DurgiPedia - [Body temperature regulation](https://durgical.com/en/physiology/body-temperature-regulation/) - [Heat exhaustion and heat stroke](https://durgical.com/en/physiology/heat-exhaustion-and-heat-stroke/) - [Hypothermia and cold injury](https://durgical.com/en/physiology/hypothermia-and-cold-injury/) - [Fever](https://durgical.com/en/physiology/fever/) - [Skin blood flow](https://durgical.com/en/physiology/skin-blood-flow/) - [Skin: epidermis layers, dermis, hypodermis](https://durgical.com/en/histology/skin-epidermis-layers-dermis-hypodermis/) - [Wound healing: phases and scar](https://durgical.com/en/histology/wound-healing-phases-and-scar/) ## Microorganisms - [Pseudomonas aeruginosa](https://durgical.com/en/microbiology/pseudomonas-aeruginosa/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Burns](https://www.who.int/news-room/fact-sheets/detail/burns) (World Health Organization, 2026); [Heat emergencies: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000056.htm) (MedlinePlus, US National Library of Medicine, 2026); [Hypothermia: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000038.htm) (MedlinePlus, US National Library of Medicine, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/thermal-injury-burns-hyperthermia-and-hypothermia/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/thermal-injury-burns-hyperthermia-and-hypothermia/