physical injuries-asphyxia

1. Definition and types of physical injuries

• Injuries from physical agents • Heat (local→burn, systemic→heat illness), Cold, Electricity, Pressure, Radiation, Starvation

2. Definition of burn & manner of infliction

• Tissue injury of external body surface from heat, radiation, chemicals, or electricity • Manner: Mostly accidental > homicidal (battered child/concealing death) > suicidal

3. Types of burns

• Dry: Flame (contact w/ flame), Contact (hot object ≥70°C), Radiant heat (no contact) • Moist (scalds): hot liquid/steam • Chemical (corrosions) • Microwave • Electric (electrocution)

4. Factors determining severity/prognosis of burns

• Age (extremes worse)

• Sex (females more neurogenic shock)

• General health (chronic disease = worse)

• Intensity of heat

• Duration of exposure

• Site (neck/chest/abdomen bad; perineum worst)

• Depth

• Extent (TBSA) – most important

5. Rule of Nines (adult)

• Head & neck = 9% • Each upper limb = 9% • Anterior torso = 18%, Posterior torso = 18% • Each lower limb = 18% • Perineum = 1% • 33% TBSA = grave prognosis; 50% = expected fatal

6. 1st degree burn

• Epidermis only • Blister-free, dry, painful, red (e.g., sunburn) • Heals 3–6 days

7. 2nd degree burn

• Epidermis + part of dermis • Painful, swollen, red, blistering • Superficial partial: 7–20 days • Deep partial: >21 days

8. 3rd degree burn

• Full thickness (epidermis + entire dermis), reaches subcutaneous tissue • White/leathery/blackish, necrotic, painless (nerve destruction) • Heals in months; needs skin graft

9. 4th degree burn

• Penetrates muscle/bone • No sensation (nerve destruction) • Heals in months; needs skin graft

10. Important note on burn depth

• Surface appearance does NOT necessarily indicate depth of injury

11. Jackson's burn zones (1947)

• Zone of coagulation (center, irreversible)

• Zone of stasis (can be saved with adequate resuscitation, or lost if inadequate)

• Zone of hyperemia (outermost, recovers)

• Zones are 3D; tissue loss in stasis zone → wound deepens & widens

12. Systemic effects of burns (>20% TBSA)

• Loss of fluid → hypovolemic shock

• ↑ vascular permeability → fluid leakage → ARDS/pulmonary edema

• Local infection → sepsis → distributive shock

• DIC from clotting factor activation • Heat loss through skin → hypothermia

• Nerve damage → neuropathic pain or permanent loss

• End organ damage (brain, kidney, liver, gut)

13. Scalding burn definition & types

• Definition: injury from steam or liquid >60°C • Types: Immersion, Splash/spill, Steam burns (may cause laryngeal/tracheal/respiratory burns → ARDS)

14. Scalding burn manners & distribution

• Homicidal: child abuse, domestic homicide

• Accidental: splash = multiple/varying depth; spill = face, neck, upper chest, arms (children pulling hot liquid)

• Water at 70°C → full thickness burn

• Clothing protects skin

• Fluid cools as it flows down → less severe distal burns

15. Heat-related illness definition & types

• Definition: disorders from overexposure to heat/exertion causing thermoregulation dysfunction

• Heat cramps: muscle cramps + profuse sweating + Na/Cl loss

• Heat exhaustion: sweating, water/salt depletion, cold clammy skin, nausea, headache

• Heat syncope: dizziness/fainting, pale moist cool skin, weak pulse, rapid HR, normal temp

16. Heat stroke definition & risk factors

• Definition: body overheating, core temp ≥40°C, most serious heat illness, needs emergency care

• Risk factors: hot/humid environment, age (>65, infants), obesity/dehydration/exertion/poor clothing/sleep deprivation, chronic disease, anticholinergic medications

17. Heat stroke pathophysiology stages

• Compensatory: ↑metabolic rate → ↑core temp → sweating → ↑cardiac output

• Noncompensatory: hypovolemia → ↓central venous pressure → ATP depletion, cellular anoxia, systemic inflammation, BBB breakdown → CNS derangement → heat stroke → death

18. Heat stroke symptoms

• Core temp ≥40°C

• Mental status change (confusion, seizures, coma)

• Sweating change (hot dry skin in weather-induced; profuse sweat in exertional)

• Nausea/vomiting

• Flushed skin

• Rapid breathing

• Tachycardia

• Headache

19. Heat stroke complications

• Multiorgan failure within 24–48h

• DIC, ARDS, renal/cardiac/hepatic failure

• Rhabdomyolysis

• Electrolyte disturbances (hypocalcemia, hyperkalemia, acidosis)

20. Electrocution definition & manner

• Definition: passage of electric current through body → pain, muscle contraction, burns, cardiac arrest, respiratory failure, death • Manner: Accidental (most common), Homicidal (rare/torture), Suicidal (rare), Judicial (electric chair)

22. Factors related to affected person (electrocution)

• Two-point contact needed (entry/exit) • Resistance: bone/cartilage/skin high; blood/muscle/nerve low; dry/thick skin = more resistance (irrelevant in high voltage) • Age: children more susceptible • State of health: comorbidities ↑ complications

23. Mechanisms of electricity-induced injury

• Depolarization of nerves/muscles → abnormal cardiac/brain rhythms, muscle tetany

• Conversion to thermal energy → tissue destruction, coagulative necrosis

• Mechanical injury from falls or violent contractions

24. Clinical picture of electrocution - Shock & burns

• Shock: unconsciousness, weak rapid pulse, hypotension, dyspnea, cold clammy skin

• Low-voltage burn: entry (palms/fingertips), exit (soles); central collapsed blister/crater, chalky white, yellow/black; 1-1.5cm; absent in 50% of low-voltage cases

• High-voltage burn: destroyed skin/subcutaneous tissue, exposed vessels/nerves/bone, charred, possible limb loss/organ rupture

• muscle spasm

25. Muscular spasm effects in electrocution

• Gripping the conductor

• Propelling the body

• Fractures (scapula, humerus, femoral neck, thoracic vertebrae)

• Rhabdomyolysis

• Respiratory paralysis

26. Mechanisms of death due to electrocution

• Direct: Central asphyxia (brainstem)

, violent asphyxia (chest spasm)

, cardiac arrhythmias

, cardiac arrest (VF=low voltage AC; asystole=high voltage AC/DC)

, electric burns

• Indirect: Trauma, fire-related burns

27. ML responsibilities in thermal/electric injury cases

• Emergency management considering age/comorbidities/pathophysiology

• Consent may be waived in emergencies

• Treat as MLC, especially suspected suicide/homicide/torture/abuse; full body exam for entry/exit points

• Photograph patterned burns •

• Detailed MLR: degree, extent (TBSA), distribution, prognosis, death mechanism

28. Types of shock (overview)

• Hypovolemic

• Neurogenic •

Sympathetic storming

• Septic

29. Hypovolemic shock

• Definition: reduced tissue perfusion from inadequate O2/nutrient delivery •

• Causes: hemorrhagic shock (most common), large burns (2nd/3rd/4th degree)

• Timing: depends on age/health/rate; fatal if blood loss ≥1.5L; pericardial >200-250cc = tamponade; pleural/peritoneal >500cc = fatal

• • Clinical: restless/agitation, pale cool skin, hypotension, tachycardia, oliguria, death

30. Neurogenic shock

• Definition: hemodynamic instability from sympathetic disruption with preserved parasympathetic

• • Causes: spinal cord injury, severe fear/anxiety, vagus stimulation

• • Timing: manifests within 2h of trauma

• • Clinical: bradycardia/arrhythmias, profound hypotension, cold clammy skin

31. Sympathetic storming

• Definition: episodes of increased sympathetic activity •

• Causes: acute multiple trauma, traumatic brain injury

• • Timing: as early as first 24h, often delayed

• • Clinical: hypertension, tachycardia, arrhythmias, hyperthermia, pupillary dilation, profuse sweating

32. Sepsis & septic shock

• Definition: sepsis-induced hypotension persisting despite fluid resuscitation

• • Causes: trauma-impaired immunity, infections •

• Timing: within first 48h

• • Clinical: altered mental status, fever >38°C or <36°C, hypotension, tachycardia, tachypnea, oliguria/anuria, WBC>12,000 or <4000

• • Diagnosis: suspected infection + ≥2 above criteria

33. Pulmonary thromboembolism

• Definition: clot from elsewhere lodges in lung vessels, restricts blood flow, ↑pulmonary arterial pressure

• • Timing: immediate, early (within 3 days), or late (day 5-7)

• • Predisposing: pelvic/long bone fractures, hypercoagulable states (shock/sepsis/hypoxia), immobility

• • Clinical: sudden dyspnea, sharp chest/arm/shoulder/neck/jaw pain, cough ± blood, pale/cyanotic skin, tachycardia, sweating

34. Fat embolism

• Definition: intravascular fat blocks blood flow; common after long bone fractures (femur, tibia, pelvis)

• • Timing: gradual onset 12-72h after injury •

• Predisposing: orthopedic trauma/surgery, soft tissue damage/burns, crush injury

• Clinical: dyspnea, neurologic changes (confusion/headache/seizures), petechial rash (eyes/axilla/chest), tachycardia, fever, jaundice

35. Arterial gas (air) embolism

• Definition: bubbles in artery block organ blood supply → ischemia; more serious than venous

• • Causes: penetrating/blunt chest trauma (bronchopulmonary venous fistula), migration via right-to-left shunt

• • Clinical: rapid LOC/neurological impairment, coronary embolism → arrhythmia/cardiac failure/arrest

36. Venous air embolism (VAE)

• Definition: air enters vein → travels to pulmonary circulation

• • Causes: blunt head trauma w/ open cranial fractures, penetrating/blunt chest trauma, cut-throat (uncommon but consider) •

• Clinical: chest pain, cyanosis, dyspnea, shock, hemoptysis/bloody froth (PE)

37. Curling's ulcer

• Causes: severe trauma, massive burns

• • Site: esophagus, stomach (fundus/body), duodenum

• • Timing: early OR late (>2 weeks, duodenum, chronic signs)

• • Mechanism: splanchnic hypoperfusion → mucosal ischemia;

• ↓bicarbonate → acid mediated damage

• excess bile with burn toxins → breaks mucosal barrier allowing H+ ions to backflow and harm mucosa

• • Complication: perforation & bleeding

38. Cushing ulcer

• Causes: ↑intracranial tension from traumatic brain injury •

• Site: stomach & duodenum

• • Timing: 3rd stage of Cushing triad

• • Mechanism: ↑ICP stimulates vagus → ↑gastric acid → mucosal ulceration

• • Complication: deep perforation & bleeding

39. DIC (disseminated intravascular coagulopathy)

• • Definition: systemic coagulation activation → fibrin deposition → microthrombi → multiorgan dysfunction; consumes clotting factors → hemorrhage

• • Causes: crush injury, head injury, burns/heat stroke, sepsis, fat embolism

• • Timing: fibrinolytic phase = acute trauma (bleeding/death); late phase = multiorgan dysfunction in 24-48h

• • Clinical: recent severe infection/trauma/obstetric history, bleeding from multiple sites, indicates site of hemorrhage or occlusion

40. ARDS (adult respiratory distress syndrome)

• Definition: acute diffuse lung injury - poor oxygenation, pulmonary infiltrates

• • Causes: shock, fat embolism, gastric aspiration (comatose), near drowning

• • Timing: begins 24-48h after injury

• • Clinical: dyspnea, tachypnea, tachycardia, chest pain, low BP, confusion

41. ML responsibilities - trauma complications

• Strong suspicion + understanding pathophysiology essential •

• Prevention, early diagnosis, timely intervention = standard of care

• evaluate patient Consider age and comorbidities

• l Protocol adherence protects against malpractice

• • PTCs don't remove MLC status

42. Asphyxia definition & types of anoxia

• Asphyxia: inadequate O2 to tissues • Anoxic anoxia: O2 not entering/lungs can't oxygenate • Anaemic anoxia: reduced O2 carrying capacity of blood • Stagnant anoxia: slowed circulation • Histotoxic anoxia: cells can't use delivered O2

43. Causes of anoxic anoxia

• Ambient: high altitude, irrespirable gas (CO2/N2) • Central: CNS depressant overdose (morphine), electrocution • Paralytic: botulism, poliomyelitis • Mechanical (violent asphyxia): smothering, strangulation/throttling/hanging, traumatic asphyxia, choking, drowning, glottic edema • Vascular: pulmonary embolism

44. Causes of anaemic anoxia

• Chemically combined Hb: CO poisoning, methemoglobinemia • Hemolysis: naphthalene, arsine gas, viper venom, favism, incompatible transfusion • Hemorrhage

45. Causes of stagnant & histotoxic anoxia

• Stagnant: advanced heart failure, vagal/histaminic shock • Histotoxic: cyanide poisoning, extreme cold exposure

46. Violent mechanical asphyxia classification

• Compressional: on mouth/nose (smothering); on neck (hanging/ligature strangulation, manual strangulation/throttling); on chest/abdomen (traumatic/positional asphyxia) • Obstructive: solid foreign body (choking); liquid (drowning)

48. Classic external signs of asphyxia

• Cyanosis: bluish discoloration (lips, nose tip, nailbeds, ear lobes, tongue tip); needs ≥5g reduced Hb/100mL • Petechial hemorrhages: pinpoint (0.1-2mm), from acute venous pressure rise, in lax tissue (eyelid, pleura, epicardium) • Dark blue hypostasis: from deficient oxygenation

49. Hanging definition & types

• Definition: violent death by suspending body with ligature around neck; constricting force = body weight (whole or part) • Complete: body suspended, not touching ground, full body weight • Incomplete/partial: body part touches ground, partial weight (sitting/kneeling/lying)

51. Hanging - facial signs

• Face pale (complete hanging - both carotid & vertebral occluded) or congested (incomplete - only carotid occluded, vertebral still supplies)

• Subconjunctival petechiae + prominent eyeballs •

Tongue protrudes, swollen, cyanotic

• Dribbling saliva at mouth angle (antemortem sign)

• Head tilted opposite to suspension point

52. Hanging - neck & other body signs

• Other: cyanosis of fingernails, partial penile erection, involuntary urination/defecation, glove-and-stocking lividity (if prolonged suspension)

53. Mechanisms of death in hanging

• Cerebral ischemia (most important): carotid/vertebral artery stretch from body weight •

Anoxic anoxia: larynx lifted, tongue root presses palate

• Reflex cardiac inhibition: carotid sinus/body stimulation → vagal shock

• Spinal cord-brainstem disruption: C2-C3/C3-C4 fracture-dislocation (judicial hanging, 4-10ft drop)

54. Manner of death & sequelae - hanging

• Suicidal: most common

• Accidental: children w/ ropes/banisters, workmen falling from scaffold

• Homicidal: very rare (postmortem to conceal crime, or antemortem on senile/unconscious victim)

55. Ligature strangulation - definition & clinical picture

• Definition: violent asphyxia by ligature constriction without suspension •

Face: markedly congested/cyanosed, petechiae, proptosis, subconjunctival hemorrhage, bloody discharge from nose/mouth/ears (absent if death = reflex cardiac inhibition) •

Ligature mark: low (below thyroid), transverse, complete, deep; area below ligature paler

56. Manual strangulation (throttling) - clinical picture

• Facial signs as in ligature strangulation, except pale face if reflex cardiac inhibition

• Neck signs: crescentic fingernail abrasions and contusions (may be absent if interfering material e.g. collar)

57. Strangulation - mechanisms of death & manner

• Ligature: anoxic anoxia (most important), reflex cardiac inhibition, cerebral ischemia (strong force), delayed glottic edema

• Manual/throttling: reflex cardiac inhibition (most important, vagal shock), anoxic anoxia, delayed glottic edema

• Manner - Ligature: homicidal (most common, struggle evidence), accidental (children/ropes, umbilical cord), suicidal (very rare)

• Manner - Manual: often homicidal

59. Smothering - definition & external picture

• Definition: mechanical occlusion of nose/mouth (hand, cloth, pillow, plastic bag)

• External: classic asphyxia signs WITHOUT facial venous congestion; multiple fingernail contusions/abrasions around nose/mouth (absent if soft object used); lip/gum/tongue contusions; lacerated inner lips from teeth pressure

60. Smothering - mechanism & manner

• Mechanism: anoxic anoxia

• Manner: Homicidal (infants/elderly/unconscious), Accidental (plastic bag/sheet over child's head, infant prone in pillow), Suicidal (plastic bag, very rare)

61. Choking - definition, mechanism & manner

• Definition: asphyxia from internal airway obstruction •

Mechanism: reflex cardiac inhibition (laryngeal trauma), anoxic anoxia (complete/partial obstruction + laryngospasm + mucus)

• Manner: Accidental (dust/sand inhalation, foreign body impaction - food/coin/teeth/vomit/blood), Homicidal (infanticide, pushing cloth into mouth/pharynx of unconscious adults)

62. Traumatic asphyxia

• Definition: mechanical fixation of chest preventing respiratory movements

• Mechanism: anoxic anoxia + injury to vital organs

• External: congestion of head/neck/upper trunk with petechiae, chest/abdomen contusions, line of demarcation •

Manner: Accidental (building collapse, crush under car, crowd/riot crush), Homicidal (Burke & Hare "burking")

63. Positional asphyxia

• Definition: body confined in position/restricted space impairing breathing •

Mechanism: anoxic anoxia

• External: classic asphyxia signs, body confined/wrapped restricting movement

• Manner: Accidental (entrapment, esp. children), Homicidal (forced position limiting lung expansion)

64. Drowning - definition & types

• Definition: asphyxia from submersion of mouth/nose in fluid; complete body submersion not necessary

• Typical wet drowning: classical, water inhaled/swallowed/lodged in lungs

• Atypical dry drowning: laryngospasm prevents water entry; best for resuscitation

65. True drowning mechanism - anoxic anoxia

• Accidental submersion → loss of breathing pattern → panic/struggle/laryngospasm → pulmonary aspiration/apnea → hypoxemia → hypoxia/hypercarbia/acidosis → end-organ damage & circulatory arrest

66. Drowning in fresh water - mechanism

• Hypotonic water absorbed from lungs → enters circulation → hemodilution → heart overload

• Also lysis of RBCs → release of potassium → hyperkalemia → cardiotoxic effect → death

67. Drowning in salt water - mechanism

• Hypertonic water → withdraws fluid from circulation into lungs → pulmonary edema + asphyxia

• Hemoconcentration → hypovolemia → circulatory shock → myocardial anoxia → shock → cardiac standstill → death

68. Non-drowning mechanisms of death

• Death before water entry: natural (convulsion/heart attack) or unnatural (body disposal to conceal cause/identity)

• Traumatic injuries: faulty diving, striking objects, boat accidents

• Reflex vagal inhibition: cold water rush into nasal sinuses/pharynx/larynx, sudden cold immersion •

Dry drowning (<10%): laryngospasm before lung entry, lungs appear dry

• Delayed bronchopneumonia (near/secondary drowning): initial recovery then deterioration from pulmonary edema/aspiration pneumonia/electrolyte imbalance

69. Drowning - sure signs (drowning process)

• Cyanosis • Froth: abundant, white (or bloody), odorless, recurs after chest pressure; from violent respiration mixing water+exudate+surfactant

• Dark blue hypostasis

• Cadaveric spasm: ATP depletion in hand muscles → firmly clutched weeds/mud/sand/gravel; fingernail abrasions in palms

70. Drowning - probable signs (body in water)

• Wet, muddy skin/clothes • Cutis anserina (goose skin)

• Palms/soles: 1-2.5h = corrugated/pale/sodden (washerwoman's skin); weeks = peeling in glove/stocking pattern

• Postmortem injuries: fish bites, propellers, rocks

• PM changes in water: cooling 2x faster; hypostasis dark blue in head/neck/shoulders; adipocere in 3wks-6months; putrefaction takes double time

71. Drowning - manner of death

• Accidental: most common (drunk, narcotic, epileptic in shallow water)

• Suicidal: next common (may tie feet/weights) •

Homicidal: rare (infants/children, pushing unaware person); absence of sure signs if concealing murder

72. ML responsibilities - violent asphyxia victims

• Provide treatment per presentation (neuro symptoms, ischemia, anoxia, arrhythmia, electrolytes)

• Monitor 48h for delayed death (hanging, strangulation, near-drowning)

• Written consent from non-emergency conscious adults/relatives

• Preserve evidence (ligature, cloth) - air dry, hand to authorities •

Detailed diagrammed MLR • All cases = MLC, notify police of admission/discharge/death

• If death: no death certificate, no body release, keep in