see also: [[Burns]] See: [Lightning Injuries – Core EM](cubox://card?id=7233194479765687077) > [!Key Points] > - Death from ==electric shock== is due to **ventricular fibrillation**, (for ==lightning== it is **asystole** ) the lethal arrhythmia occurring at the time of the exposure; *therefore, routine admission for ECG monitoring is unnecessary* > - most deaths are caused by low-voltage <1000V exposures > - Can calculate current from voltage and expected skin resistamce using V=IR then compare to table below (but not necessary) > - ==Threshold for VF is 100mA== > - the amount of current passing through the body is determined mainly by tissue resistance, which is dramatically reduced by moisture > - electrical injury resembles a crush injury more than a burn. tissue damage below the skin level is more severe than cutaneous wound would suggest > - lighting injury is different from high-voltage electrical injury and has a unique range of features; mgmt is mostly expectant - roughly 20 electrical fatalities each year in australia # Physics electrical current passing through the body can cause damage in two ways: 1. thermal injury 2. physiological change > Current greater than 10 mA can induce muscular tetany and prevent the patient from letting go of the source > ==threshold for ventricular fibrillation is 100mA== > The maximum "safe" current tolerable for 1s is 50mA >[!Ohm's Law] >V = IR >*current passing through the body is directly proportional to the voltage and inversely proportional to resistance* # Electric shock risk factors Factors that determine the effects of electrical current passing through the body are: - types of current - most injurys from AC (3x as dangerous as DC) - tetany is a feature of AC, not of DC - household frequency 50hz, in dangerous range - voltage - electromotive force in the system - generally, the greater the voltage, the more extensive the injury - **high voltage >1000V** - household voltage in australia = 240V - voltage <50V are not hazardous - ==tissue resistance== - different tissues provide different resistance - bone highest resistance, then fat, tendon, skin, muscle, blood vessels, and nerves - **moist skin has resistance of 1000 ohms, dry, thick skin resistance of 100,000 ohms** - therefore, by Ohm's law, ==dry skin resistance to a contact with a 240 V potential results in current of 2.4 mA==, which is just above perception. - when skin is wet and dropps to 1000 ohms, ==current increases to 240mA, which is easily enough to trigger ventricular fibrillation== - current path - hand-to-hand passes through heart - hand to foot less goes through heart - leg to leg none through heart - contact duration - longer = worse ![[Pasted image 20230702215556.png]] # Electric shock clinical features - more like a crush injury - differ from thermal burns in several ways: - direct effects onheart and nervous system - electrical injury involves deep structures - small entry and exit wounds do not accurately indicate extent or depth of tissue damage - many phenotypes ## Burns - arc burns ## Cardiac - **ventricular fibrillation** is usual cause of immediate death - delayed arrhythmia is very rare - sinus tachy is common and non-specific ST and T changes may be observed - AF very rare and usually resolves spontaneously - AMI rare ## nervous system acute and delayed neurologicla sequalae are possible **acute** - resp arrest - seizures - altered mentation - amnesia - coma - expressive dysphasia - motor deficits **delayed** - spinal cord injury/myelopathy with local amyotrophy and long tract sings - reflex sympathetic dystrophy ## renal - renal failure may occur secondary to myoglobinuria ## Vascular - large and small vessel arterial and venous thrombosis - DVT, arterial thrombosis ## Musculoskeletal - tetanic muscle contractures can result in compression fractures of vertebral bodies - fractures of long bones and joint dislocations - rhabdo # Electric shock ED management - primary and secondary survey - ECG - cardiac monitoring not needed if normal ECG and asymptomatic - routine CK and troponin is not required - **most patients can be reassured and d/c'd from ED** - [delayed lethal arrhythmias have not been reported in patients without initial arrhythmias](x-devonthink-item://10DC3BB1-027C-40D6-BDB3-4AF0C6B160E6?page=797&start=1500&length=89&search=Delayed%20lethal%20arrhythmias%20have%20not%20been%20reported%20in%20patients%20without%20initial%20arrhythmias) - **Severe electrical injury with extensive soft tissue damage should be managed as a crush injury** - more likely wiht high voltage exposure ; look for large exudation and sequestration of fuids in the damaged area - volume replacement and tx acidosis and rhabdo/myoglobinuria # Tasers - deliver 50,000V of electricity in rapid pulses over 5s - essentially rapid fire low-amplitude DC shocks - output mmostly staus near surface of teh body in skin and muslces and isn't supposed to penitrate into internal organs - After being tasered, most healthy subjects can be safely discharged after barb removal and clinical assessment - **high risk patients**: with known ICD or PPM, prenancy, intoxicated need to be addressed - if chest pain; standard CP workup - **pregnant women** > 24 weeks should stay for CTG monitoring # Lightning injury Lightning vs high-voltage injury #tables | factor | lightning | high voltage| |---|---|---| |time of exposure|brief instantaneous| prolongned tetanic| |energy level| 100 million V, 200K A| usually much lower| |type of current| direct| alternating| |shock wave|yes|no| |flashover|yes|no| |cardiac arrest| asystolic| ventricular fibrilation| terms: **‘flashover’** seems to save many victims from death by lightning. Current passes around and over, but not through, the body. The victim’s clothing and shoes may be blasted apart. Only cutaneous flame-type burns result. ## clinical features **immediate** - *Asystolic* cardiac arrest rather than VF - can be followed by secondary hypoxic arrest - neurologic deficits, unconscious, mute, unable to move (usually resolves) - contusions from shock waves - tympanic membrane rupture **delayed** - *keraunoparalysis* - lightning induced limb paralysis is extremly common. flacidity and complete loss of sensation of the affect limb are observed. can't feel pulses, mottled, plae, blue ?due ot lightning-induced vasospasm - usually self resolves within 1-6 hours - "feathery" cutaneous burns (lichtenburg flowers) - pathognomonic of lightning injury - *cateracts* - sensorineural deafness - vestibular dysfunciton - *retinal detachment* - optic nerve damage ## Treatment - standard trauma resus - DDx is CVA, seizure, spinal cord injury, closed head injury, stokes-adams attack, MI, toxins - examine ears - treat lightning-induced limb paralyss expectantly - standard tx for ocular complications eg retinal detachment or cataracts - document baseline visual acuity ## Prognosis if you survive the initial strike, prgnosis is excellent unless significant secondary injury ## disposition *admit lightning strike patients for observation* if abnormal mental status or ECG, or with significant burns or traumatic complications burns usualy heal well; grafting is rarely required for those with ocular complications, long term opthalmic follow up is necessary # Related Questions ## electrical injury - [x] 94Q: [Electrical Injury](x-devonthink-item://4134DDB3-6E12-474A-9F6F-64135C0C6048?page=31) -- [Answer](x-devonthink-item://AC92B5F1-8EE6-461A-B03E-F70AE7DC1275?page=32) -- [prop](x-devonthink-item://68EA6F60-334D-4A94-8327-78286C5F1AED?page=7) - [x] 95Q: [Electrical Injury](x-devonthink-item://4134DDB3-6E12-474A-9F6F-64135C0C6048?page=53) -- [Answer](x-devonthink-item://AC92B5F1-8EE6-461A-B03E-F70AE7DC1275?page=53) - [x] 96Q: [Electrocution](x-devonthink-item://8A1FC024-FD4E-4202-A93D-77C4E8234DC5?page=14) -- [Answer](x-devonthink-item://7EEBE66F-C2B1-4EF7-B29C-FB52D469C8CD?page=13) - [x] DUPLICATE Q: [Electrocution](x-devonthink-item://8A1FC024-FD4E-4202-A93D-77C4E8234DC5?page=14) -- [Answer](x-devonthink-item://7EEBE66F-C2B1-4EF7-B29C-FB52D469C8CD?page=13) - [ ] 97Q: [Electrical Injury](x-devonthink-item://7E9EF652-F67B-42C5-A536-2EE85BA1954F?page=43) -- [Answer](x-devonthink-item://2DE5FACA-6D8F-41A2-8EAA-8DFE1E76FA61?page=26) - [ ] 98Q: [Electrical Injury](x-devonthink-item://4BF6800D-0EC2-4637-A444-F2BC7D2E380C?page=12) -- [Answer](x-devonthink-item://9F437E5A-02D4-43FC-B795-5386EDE954F3?page=8) ## lightning injury - [x] 109Q: [Lightning strike](x-devonthink-item://F0498813-9350-484C-AD5B-6FF7C3AE9015?page=54) -- [Answer](x-devonthink-item://A491A3F6-FD6D-492F-BCBE-7F7BAE101EDF?page=59)