WordPress.com



201930964565Patho-physiology00Patho-physiology1460500963930Ohm’s law: DC circuits: V = I (current) x R (resistance) AC circuits: v = I (current) x Z (impedance)Factors determining injury severity:Voltage: high risk >600V; high voltage = >1000V (threshold for severe injury); household voltage = 240V; lightning = 100 million – 2 billion V; arc formed in high voltage can cause thermal injuryCurrent type: AC VF, tetanic muscle contractions; AC more common; DC = lightning, AC = household; AC and DC have similar effects at high voltageCurrent size: proportional to voltage of source, inversely proportional to resistance of conductor; lightning = 30,000-50,000Amp 1mAmp tingling sensation 2-10mAmp pain 10mAmp paralysis, tetany 30mAmp extreme breathing problems 100mAmp – 1Amp VF, respiratory arrest, burns >10Amp asystoleResistance: bone > fat > tendon > skin (25x ? resistance if wet) > muscle > blood vessels > nervesPathway: vertical = more dangerous to brain (20% mortality) horizonal = more dangerous overall; spares brain, but still effects heart (5% through heart), respiratory muscles, spinal cord (60% mortality, 3x ? risk of VF)Duration: AC longer; DC thrown away; lightning high voltage but very short duration (10-100msec)Electrical mechanism of Injury: CV: vascular spasm ( compartment syndrome), vascular bleeding (may occur late), arterial and venous thrombosis; cardiac arrhythmias (fast onset; delayed rare; VF more common with low voltage AC; asystole more common with DC or high voltage AC (although can also get VF); cardiac arrest in 75% direct lightning strike victims; variety of arrhythmias and ECG changes possible, often transient); direct diffuse myocardial necrosis (more severe in high voltage, AC; may not be ECG changes or typical symptoms); HTN, tachycardia, non-specific ECG changes (due to massive catecholamine release); If no arrhythmia at time of presentation, no monitoring needed; if arrhythmia present at time of presentation, will usually resolve by itselfNS: neurological injury occurs in 50% with high voltage burns; seizures, ? LOC, amnesia, coma, expressive dysphasia, motor deficits, cranial nerve deficit, spinal cord injury, memory deficit, hypoxic injury In lightning: leg paralysis, hemiplegia, tinnitis, autonomic dysfunction (eg. Mydriasis, anisocoria)Grp I: immediate and transient; LOC 75%; confusion, amnesia, headaches, paraesthesia, weakness 80%; keraunoparalysisGrp 2: immediate and prolonged; significant neurological injury (eg. Intracerebral haemorrhage, cerebellar syndrome, hypoxic ischaemic neuropathy)Grp 3: delayed; seizures, muscular atrophy, ataxia, chronic painGrp 4: traumaticMS: muscle contraction and necrosis (CK reflects injury) compartment syndrome and rhabdomyolysis (rare with lightning inj) In lightning: keraunoparalysis – delayed onset reversible transient paralysis associated with sensory disturbance and peripheral vasoconstriction; resolves in 1-6 hours; lower limb > upper limb; appears cool, blue, pulseless; due to sympathetic instability and intense vascular spasm; fasciotomy almost never requiredRS: respiratory depression; suffocation from respiratory muscle contraction and transient paralysis of medullary respiratory centre (can result in secondary cardiac arrest VF and asystole); inhalation injury from ozone exposure (irritation, pulmonary oedema, haemorrhage)GI: ileus, perforation, stress ulcersGU: renal ischaemic injury and myoglobinuric ARF (10% severe burns get ARF); transient oliguria, albuminuria, haemoglobinuriaHaematological: coagulation disordersEye: in lightning: cataracts (common), corneal burns, intraocular haemorrhage, retinal detachment, uveitis, hyphemaEar: in lightning: sensorineural hearing loss; 50% have tympanic membrane ruptureThermal Burns Mechanism of Injury: Exit and entry wounds do not indicate depth, extent of injury often not visible, severity difficult to assess; muscle / blood vessel / nerve / spinal cord necrosis; secondary flame burns related to clothes; deep internal burn more common in high voltage electrical injury than lightning injury; more severe burns caused by arcs (high voltage); in children, oral commissure and lingual artery burns with delayed bleedingTrauma: blunt (in lightning injury), crush, blast (high voltage; chest, tympanic membrane, GI)00Ohm’s law: DC circuits: V = I (current) x R (resistance) AC circuits: v = I (current) x Z (impedance)Factors determining injury severity:Voltage: high risk >600V; high voltage = >1000V (threshold for severe injury); household voltage = 240V; lightning = 100 million – 2 billion V; arc formed in high voltage can cause thermal injuryCurrent type: AC VF, tetanic muscle contractions; AC more common; DC = lightning, AC = household; AC and DC have similar effects at high voltageCurrent size: proportional to voltage of source, inversely proportional to resistance of conductor; lightning = 30,000-50,000Amp 1mAmp tingling sensation 2-10mAmp pain 10mAmp paralysis, tetany 30mAmp extreme breathing problems 100mAmp – 1Amp VF, respiratory arrest, burns >10Amp asystoleResistance: bone > fat > tendon > skin (25x ? resistance if wet) > muscle > blood vessels > nervesPathway: vertical = more dangerous to brain (20% mortality) horizonal = more dangerous overall; spares brain, but still effects heart (5% through heart), respiratory muscles, spinal cord (60% mortality, 3x ? risk of VF)Duration: AC longer; DC thrown away; lightning high voltage but very short duration (10-100msec)Electrical mechanism of Injury: CV: vascular spasm ( compartment syndrome), vascular bleeding (may occur late), arterial and venous thrombosis; cardiac arrhythmias (fast onset; delayed rare; VF more common with low voltage AC; asystole more common with DC or high voltage AC (although can also get VF); cardiac arrest in 75% direct lightning strike victims; variety of arrhythmias and ECG changes possible, often transient); direct diffuse myocardial necrosis (more severe in high voltage, AC; may not be ECG changes or typical symptoms); HTN, tachycardia, non-specific ECG changes (due to massive catecholamine release); If no arrhythmia at time of presentation, no monitoring needed; if arrhythmia present at time of presentation, will usually resolve by itselfNS: neurological injury occurs in 50% with high voltage burns; seizures, ? LOC, amnesia, coma, expressive dysphasia, motor deficits, cranial nerve deficit, spinal cord injury, memory deficit, hypoxic injury In lightning: leg paralysis, hemiplegia, tinnitis, autonomic dysfunction (eg. Mydriasis, anisocoria)Grp I: immediate and transient; LOC 75%; confusion, amnesia, headaches, paraesthesia, weakness 80%; keraunoparalysisGrp 2: immediate and prolonged; significant neurological injury (eg. Intracerebral haemorrhage, cerebellar syndrome, hypoxic ischaemic neuropathy)Grp 3: delayed; seizures, muscular atrophy, ataxia, chronic painGrp 4: traumaticMS: muscle contraction and necrosis (CK reflects injury) compartment syndrome and rhabdomyolysis (rare with lightning inj) In lightning: keraunoparalysis – delayed onset reversible transient paralysis associated with sensory disturbance and peripheral vasoconstriction; resolves in 1-6 hours; lower limb > upper limb; appears cool, blue, pulseless; due to sympathetic instability and intense vascular spasm; fasciotomy almost never requiredRS: respiratory depression; suffocation from respiratory muscle contraction and transient paralysis of medullary respiratory centre (can result in secondary cardiac arrest VF and asystole); inhalation injury from ozone exposure (irritation, pulmonary oedema, haemorrhage)GI: ileus, perforation, stress ulcersGU: renal ischaemic injury and myoglobinuric ARF (10% severe burns get ARF); transient oliguria, albuminuria, haemoglobinuriaHaematological: coagulation disordersEye: in lightning: cataracts (common), corneal burns, intraocular haemorrhage, retinal detachment, uveitis, hyphemaEar: in lightning: sensorineural hearing loss; 50% have tympanic membrane ruptureThermal Burns Mechanism of Injury: Exit and entry wounds do not indicate depth, extent of injury often not visible, severity difficult to assess; muscle / blood vessel / nerve / spinal cord necrosis; secondary flame burns related to clothes; deep internal burn more common in high voltage electrical injury than lightning injury; more severe burns caused by arcs (high voltage); in children, oral commissure and lingual artery burns with delayed bleedingTrauma: blunt (in lightning injury), crush, blast (high voltage; chest, tympanic membrane, GI)201930330200Electrical Injuries00Electrical Injuries11417307375525001911355867400Assessment00Assessment561403559328050014363705867400Examination: do thorough musculoskeletal, neurological and skin exam; assess eyes and ears; if ? BP, search for results of traumaSkin: cutaneous findings in 90% lightning strikes; look for entry and exit points (rare in lightning); linear burns (along sweat lines), punctate burns (1-10mm, may be full thickness), feathering lesions (due to extravasation of blood into subcutaneous tissue; Lichtenberg figures), thermal injury (clothing, belt buckles, only 5% are full thickness); in lightning burns are usually superficial and heal wellECG: do initial ECG; monitoring not indicated if asymptomatic and normal ECG (most severe cardiac complications present acutely; very unlikely delayed); less AF, but more asystole in lightning strikeIndications for ECG monitoring (at least 12 hours): high voltage (>1000V) / abnormal ECG / LOC, seizures, paediatrics, previous cardiac disease, burnsBloods/urine: monitor for myoglobinuria; less deep tissue damage, myoglobinruia and renal failure in lightning strike00Examination: do thorough musculoskeletal, neurological and skin exam; assess eyes and ears; if ? BP, search for results of traumaSkin: cutaneous findings in 90% lightning strikes; look for entry and exit points (rare in lightning); linear burns (along sweat lines), punctate burns (1-10mm, may be full thickness), feathering lesions (due to extravasation of blood into subcutaneous tissue; Lichtenberg figures), thermal injury (clothing, belt buckles, only 5% are full thickness); in lightning burns are usually superficial and heal wellECG: do initial ECG; monitoring not indicated if asymptomatic and normal ECG (most severe cardiac complications present acutely; very unlikely delayed); less AF, but more asystole in lightning strikeIndications for ECG monitoring (at least 12 hours): high voltage (>1000V) / abnormal ECG / LOC, seizures, paediatrics, previous cardiac disease, burnsBloods/urine: monitor for myoglobinuria; less deep tissue damage, myoglobinruia and renal failure in lightning strike200088581343500191770880745Lightning00Lightning14363703994785Ball lightning: moving floating ball; low energy; rarely fatal; associated with neurological sequelaeDirect strike: upper body strike more severe due to large potential difference between upper and lower bodyContact injury: victim touching objectSide flash: victim near objectGround current: lightning spread through ground; injury more severe if victim’s legs apart due to large potential difference between feetBlast injury: major organs, earFlashover: less internal cardiac injury and muscle necrosisAssociated with shockwave which can cause hollow viscous injury, retinal detachment, tympanic membrane perforation00Ball lightning: moving floating ball; low energy; rarely fatal; associated with neurological sequelaeDirect strike: upper body strike more severe due to large potential difference between upper and lower bodyContact injury: victim touching objectSide flash: victim near objectGround current: lightning spread through ground; injury more severe if victim’s legs apart due to large potential difference between feetBlast injury: major organs, earFlashover: less internal cardiac injury and muscle necrosisAssociated with shockwave which can cause hollow viscous injury, retinal detachment, tympanic membrane perforation25469853180715Yes00Yes47961552539365Rare00Rare25469852539365Common00Common47961553504565Asystole, prolonged apnoea, blunt injury00Asystole, prolonged apnoea, blunt injury14363703504565Cause of death00Cause of death25469853504565VF, prolonged apnoea, blunt injury, deep tissue burns00VF, prolonged apnoea, blunt injury, deep tissue burns47961552218055Asystole (also with DC)00Asystole (also with DC)47961551887855Superficial00Superficial47961551564005Billions00Billions25469852218055VF (low volts), asystole (high volts)00VF (low volts), asystole (high volts)25469851887855Deep00Deep25469851564005Up to 200,000V00Up to 200,000V4794885123444010 microseconds – 3 milliseconds0010 microseconds – 3 milliseconds254698512344400.3 – 2 seconds000.3 – 2 seconds2546985880745AC00AC4794885880745Lightning00Lightning14382753180715Blunt injury00Blunt injury14363702877820Fasciotomy00Fasciotomy14382752538730Renal / rhabdo00Renal / rhabdo14382751234440Duration00Duration14376401564005Voltage00Voltage14376401887855Tissue Damage00Tissue Damage14370052218055Cardiac Rhythm00Cardiac Rhythm191135330200Epidemiology00Epidemiology143827533020090% males; 20% toddlers, 25% adolescents, 20% workers; lightning mortality rate 10-30%, 75% survivors have residual disability0090% males; 20% toddlers, 25% adolescents, 20% workers; lightning mortality rate 10-30%, 75% survivors have residual disability2584454314825In Pregnancy00In Pregnancy15163804314826DC cardioversion safe; burns have adverse effect00DC cardioversion safe; burns have adverse effect2584453322955Prognosis00Prognosis15163803323590Lightning: leg burns mortality 30%; cranial burns mortality 37%; cardiac arrest mortality 76%; if survive initial strike (no immediate sequelae), v good prognosis unless significant 2Y injury; 25-50% survival rate in arrhythmia if bystander CPR; overall mortality from lightening 34% (2/3 in 1st hour from apnoea / arrhythmia)DC shocks have 3x morbidity / mortality00Lightning: leg burns mortality 30%; cranial burns mortality 37%; cardiac arrest mortality 76%; if survive initial strike (no immediate sequelae), v good prognosis unless significant 2Y injury; 25-50% survival rate in arrhythmia if bystander CPR; overall mortality from lightening 34% (2/3 in 1st hour from apnoea / arrhythmia)DC shocks have 3x morbidity / mortality787402607945002584452607945Disposition00Disposition15163802607945Discharge if: <240V, brief, no LOC / tetany / burn wounds, asymptomatic + normal exam and ECG (if minor wound / paraesthesia, do ECG and urine)Admit if: >600V / abnormal ECG or examination / horizontal transmission00Discharge if: <240V, brief, no LOC / tetany / burn wounds, asymptomatic + normal exam and ECG (if minor wound / paraesthesia, do ECG and urine)Admit if: >600V / abnormal ECG or examination / horizontal transmission258445329565Management00Management1516380329565Safety of rescuers (safe to approach in lightning); if mass casualties, give priority to cardiac arrest (reverse triage compared to normal)C: assume spinal injury; spinal # may affect multiple vertebrae therefore image entire columnA: airway may be difficult if airway burns; early ETT if extensive burnsB: respiratory arrest may persist after ROSC, so ventilation needs to be supportedC: aggressive prolonged CPR indicated (cardiac arrhythmias and prolonged respiratory arrest may be only clinical problem; often young and survive prolonged CPR with minimal problems; resus may be successful even when time to commencement of resus prolonged; but chance of recovery low after 20- 30 minutes CPR); arrhythmias usually resolve spontaneously, but otherwise treat as per usual; give 20ml/kg IVF bolus then aim 1-2ml/kg/hour urine output (or IVF as per Parkland formula = 2-4ml/kg/% + maintenance); consider alkalinisation of urineD: remove smouldering clothes; all require ophthalmology review due to potential for delayed complications; dilated pupils are not sign of brain death00Safety of rescuers (safe to approach in lightning); if mass casualties, give priority to cardiac arrest (reverse triage compared to normal)C: assume spinal injury; spinal # may affect multiple vertebrae therefore image entire columnA: airway may be difficult if airway burns; early ETT if extensive burnsB: respiratory arrest may persist after ROSC, so ventilation needs to be supportedC: aggressive prolonged CPR indicated (cardiac arrhythmias and prolonged respiratory arrest may be only clinical problem; often young and survive prolonged CPR with minimal problems; resus may be successful even when time to commencement of resus prolonged; but chance of recovery low after 20- 30 minutes CPR); arrhythmias usually resolve spontaneously, but otherwise treat as per usual; give 20ml/kg IVF bolus then aim 1-2ml/kg/hour urine output (or IVF as per Parkland formula = 2-4ml/kg/% + maintenance); consider alkalinisation of urineD: remove smouldering clothes; all require ophthalmology review due to potential for delayed complications; dilated pupils are not sign of brain death ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download