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A COMPARISON OF LIGHTNING AND ELECTRICAL INJURIES DO YOU KNOW THE DIFFERENCE ? LISA CAMPFENS MD, FRCP(C), FACEP EPIDEMIOLOGY LIGHTNING ELECTRICAL -150 - 250 fatalities per year - more than 800 victims per year - kills more people in the U.S.A. each year than any other natural disaster - golfers, campers, hikers, joggers, construction workers, etc. - 30% multiple victims -2100 burn unit admissions per year -more than 1000 fatalities per year - most commonly occupational related MYTHS ABOUT LIGHTNING Lightning is always fatal Lightning burns can turn victims into ‘crispy critters’ Lightning never strikes in same place twice Victims remain ‘electrified’ Lightning injuries are like other high voltage injuries DETERMINANTS OF ELECTRICAL INJURY The exact pathophysiology is not well understood because of the large number of variables that cannot be measured or controlled. VOLTAGE AMPERAGE EFFECTS Increased voltage leads to greater potential for tissue destruction resulting in major amputations and tissue loss. This is a measure of the amount of current or energy flowing through an object. Tingling 1 - 4 mA Let-go Current 4 - 9 mA Freeze to Circuit 10-20 mA Resp Arrest 20-50 mA V Fibrillation 50-100 mA * very narrow range of safety between household current and that which causes respiratory arrest or cardiac arrest. 2 RESISTANCE LEAST INTERMED MOST CIRCUIT AC DC countershock to DURATION PATHWAY VOLTAGE AMPERAGE RESISTANCE CIRCUIT DURATION PATHWAY Varies with the type of tissue. The higher the resistance of the tissue to the flow of current, the potential for electrical energy to transform to thermal energy. nerves/ blood/ muscle GOOD CONDUCTORS dry skin tendon/ fat/ bone HIGH RESISTANCE Direction of flow of current Much more dangerous because at 60cps (frequency of electrical transmission in U.S.A.) produces tetany of muscle fibres. This causes a single muscle spasm throwing the victim from the source which results in only brief instantaneous exposure but increases the likelihood of blunt trauma. Can also act as a massive cause disturbances in cardiac rhythms. Obviously increases the potential for injury. Determines the tissues at risk, the type of injury seen and the degree of conversion of electrical energy to heat. Current often concentrates at entrance and exit sites but this may also be only the ‘tip of the iceberg’. Damage to internal tissues may be spotty, irregular, unpredictable, and large distances away from entry (as nerves, blood, and muscles allow for good conduction to more resistant and distant tissues). LIGHTNING VS 10-20 million V ~20,000 A unclear DC brief instantaneous exposure flashover phenomena ELECTRICAL INJURY 110- 70,000 V < 1000 A unclear AC or DC prolonged tetany internal LIGHTNING PRODUCTION In simplified terms, static charges are produced when a cold high pressure front moves over a warm low pressure area. The moist warm air rises through the cold air causing condensation. Friction between the moving air particles causes ionization. The end result is the production of lightning and thunder. What you visualize is the Leader Stroke which is the slow jagged path from cloud to ground. As the leader stroke approaches the ground, an even stronger opposite charge is induced and there is a massive amount of release of energy in the form of the Pilot Stroke. Therefore, the majority of lightning discharge is actually in the upward direction. Thunder is the result of the explosive expansion of air ionized and heated by the stroke. 3 LIGHTNING MECHANISMS OF INJURY DIRECT STRIKE CONTACT SIDE FLASH STEP VOLTAGE other, a become part responsible for the BLUNT TRAUMA Victim touches object in the path of current eg. tree, tent pole, umbrella, golf club ‘splash’ or ‘flashover phenomena’ Current takes the path of least resistance and ‘splashes’ over onto victim from other object because the air between the object and the victim provides better conductance. Lightning current will spread through the ground in a radial pattern. If one foot is closer to the strike point than the potential difference is created allowing the legs to of the pathway. This is often the mechanism death of livestock. CLINICAL IMPACT Nearly 70% will show sequelae, of which most are temporary in nature. CVS Despite the ‘flashover phenomena’, internal leakage of current may occur causing a massive DC countershock which depolarizes the entire myocardium simultaneously. ASYSTOLE>>V FIB Although automaticity causes the heart to begin beating again, the respiratory arrest may last long enough to cause a secondary arrest in the form of V Fib or asystole which is now much more resistant to therapy. If resuscitation is successful, delayed multiple dysrhythmias may be apparent. RESP Respiratory arrest is the result of a direct effect on the brain stem. Blunt trauma- pulmonary contusion CNS LOC secondary to direct effect on brainstem,hypoxia, cerebal edema, blunt trauma ( hemmhorage) Seizures (blunt trauma, hypoxia) Amnesia and confusion is universal and usually transient. 2/3 of severly injured: Lower extremity paralysis 1/3 of severly injured: Upper extremity paralysis 4 This phenomena is usually due to vascular spasm resulting from sympathetic instability. The extremities appear blue, cold, mottled, and pulseless.The majority will recover completely over a few hours. OPTH vitreal OTIC >50% will develop cataracts. These can develop up to two years after the injury. Other opthalmic injuries include corneal lesions, lens dislocation, hemmhorage, retinal detachment, transient bilateral blindness, etc. Dilated or unreactive pupils cannot be used as a criterion for brain death in a lightning victim until all other functional lesions are ruled out. facial >50% sustain TM rupture (uni or bilateral). This may be a result of the shock wave, direct burn, or a basilar skull fracture. Other injuries include direct nerve damage with sensorineural loss and/or palsies, and disruption of ossicles and mastoid. EXTS Blunt trauma- fractures/dislocations ABD Injury rare. RENAL Failure rare. SKIN Because of the ‘flashover phenomena’, deep burns occur in <5%. Initially there may be no sign of injury and may take hours to display: Linear Punctate Feathering Thermal Results secondary to steam production (along ‘sweat’ lines). Appear like multiple small cigarette burns. PATHOGNOMONIC These are not true burns and there is no damage to the skin. They produce a ‘fern pattern’ and require no treatment. These result if clothing is ignited or a victim is wearing metal which then heats up. PREHOSPITAL CARE Always ensure own safety first. Remember lightning can strike in the same place twice. Victims are not dangerous to providers. Rules of triage are reversed - RESUSCITATE THE DEAD. In absence of respiratory or cardiac arrest, victims unlikely to die of any other cause. Recognition- have a high degree of suspicion and look for clues. Concentrate on ABC’s. ED MANAGEMENT 5 PROVIDE ABC’S - Prolonged CPR not indicated. - Dilated pupils are not an absolute criteria for death. - Ensure C-spine immobilization. FLUID MANAGEMENT - Massive fluid resuscitation rarely required. - Shock may result from blunt trauma,cardiac or autonomic dysfunction. Treat accordingly. APPROPRIATE INVESTIGATIONS - Blood work may include CBC, lytes, BUN, Cr, cardiac enzymes,ABG’s - Check urine for Myoglobin - ECG, CXR, C-spine films, CT scan and other films as indicated MONITORING - Cardiac monitor for potential dysrhythmias - Insert foley catheter to monitor urine output - NG tube as needed TETANUS PROPHYLAXIS Complications result from over-aggressive management. In contrast to electrical injuries, massive fluid resuscitation, use of diuretics and alkalinization, fasciotomies, amputations, and large tissue debridements, are rarely required. DISPOSITION AND PROGNOSIS Patients should be monitored in an ICU setting for 24 hours for potential cardiac dysrhythmias. Consultation with Cardiology, Trauma service, ENT, and Opthalmolgy, will depend on given injuries. AWAKE/ALERT (+/- ear or eye injuries) expect full recovery ALTERED MENTAL STATUS OR EXTREMITY INJURY expect neurologic sequelae CARDIORESPIRATORY ARREST > 60% mortality 6 ELECTRICAL ACCIDENTS MECANISM OF INJURY DIRECT CONTACT ARCING CURRENT RESCUER CONTACT BLUNT TRAUMA This can result from: - being thrown from the source by intense contraction of muscles. - fall from height - violent muscle spasms from prolonged tetany resulting in fractures and/or dislocations. - exit wounds resulting from AC current which tend to be explosive in nature. A current spark is formed between two objects of different potential that are not in contact with each other. This usually occurs between a highly charged source and a ground. If victim becomes part of this arc, they sustain deep thermal burns at point of contact or as a result of clothing being ignited. Temperatures reach 2500o C. CLINICAL IMPACT BURNS Seen in close to 100% of victims. There may be multiple entry and exit sites. Entry wounds most commonly seen on hands and skull. Exit wounds most common on heels. ‘Kissing burns’ are seen in flexor creases as a result of arcing current. CNS 25 -100% IMMEDIATE LOC, seizures, amnesia, confusion, parasthesias, and paralysis. Spinal c cord injury results from fractured vertabrae, ligamentous injury with instability, and spinal artery spasm with thrombosis. INTERMEDIATE Pain, headache, paralysis, and autonomic disturbances. DELAYED These injuries may become apparent days to years after the initial insult and carry a very poor prognosis. It may include aphasia, ataxia, hemiplegia, seizures, Parkinson’s Disease, ascending paralysis, mononeuritis, ALS, transverse myelitis, and disseminated spinal degeneration. 7 CVS 10 - 40% 100 mA can cause V Fib or asystole. Multiple dysrhythmias may be seen. ST elevation is usually transient. AMI is rare despite elevated CK-MB fractions resulting from massive tissue damage. These levels must be interpreted with caution and require more detailed investigations to rule out permanent myocardial damage. RESP 50 mA can cause respiratory arrest usually secondary to a direct effect on the brainstem. EXTS You cannot predict the amount of underlying tissue damage from the amount of cutaneous involvement. Massive muscle necrosis, venous thrombosis, vascular ischemia, and tissue edema leads to secondary compartment syndromes requiring fasciotomies, amputations, and wide tissue debridement. Fractures and dislocations result from blunt trauma. RENAL 20% Rhabdomiolysis with the release of Myoglobin cause Acute Renal Failure. GI 25% Complications include stress ulcers, mesenteric thrombosis, gallbladder necrosis. OPTHAL Cataracts may develop up to 2 years after but unlike with lightning, only seen in 6%. MOUTH This is the most common electrical injury seen in children < 4 years old. They will chew and suck on household extension cords and sustain injuries to the mouth as a result of ‘local arc burns’ ( current arcs through saliva). Temperatures reach 2500o C. The concern is that there is a 10% risk of delayed bleeding 4-5 days later from the Labial artery when the eschar separates. Splinting is also required to minimize cosmetic deformities. PRE-HOSPITAL CARE ‘Protect the rescuers’ - the only time extrication is safe is when the power is shut off. Downed high-tension wires may repower or continue to pour current into the ground. Approach the victim as a Trauma Patient: -ABC’s -C-spine immobilization -cardiac monitoring -two large-bore IV’s- these patients require tremendous fluid resuscitation. Combined ACLS / ATLS protocols. 8 ED MANAGEMENT PROVIDE ABC’S - cardiac monitoring - maintain C-spine immobilization. FLUID MANAGEMENT - aggressive fluid resuscitation: treat for shock, burns, and potential ARF. - rule of ‘9’s doesn’t apply- aim for UO of 1-1.5 ml/kg/hr. - treatment of an electrical burn more like a crush injury than a thermal burn because of large amount of tissue damage under the skin. APPROPRIATE INVESTIGATIONS - Blood work should include CBC, lytes, BUN, Cr, cardiac enzymes, ABG’s - urinalysis for Myoglobin - ECG, CXR, +/- CT scan - other films as needed MONITORING - cardiac monitor - CVP/ Swan Ganz catheter - foley catheter / NG tube TETANUS PROPHYLAXIS ANTIBIOTICS - Will depend on individual Burn Centre. COMPLICATIONS Complications include cardiopulmonary arrest, overwhelming injuries, hypoxia,intracranial injuries, myoglobinuric renal failure, and multiple organ failure. SEPSIS is the most common cause of death after initial resuscitation. DISPOSITION Significant electrical burns must be transferred to a Regional Burn Centre. Asymptomatic patients suffering low voltage injuries with minimal cutaneous injury, normal ECG, and normal urinalysis may be observed for 6 hours and then discharged. Pediatric oral burns and pregnant patients in their 2nd or 3rd trimester should be admitted for observation. PROGNOSIS MORTALITY With high V ~10% Early- cardiorespiratory arrest Late- ARF, sepsis