Outline

• Physics of injury • Clinical featurs & effect on

different body systems • Management • disposition

Physics

• P = I2Rt ( I=V/R)

P thermal power I , in joules I current , ampers R resistance in ohmsT time in seconds V Potential , in volts

Q: All of the following are factors determining the electrical injury except ?

• Type of circuit • Duration of contact • resistance of tissue • Pathway of current • Surface area of victim

Q: All of the followings are true facts about type of circuit except ?

• DC ( direct current ) cause single muscle injury , shorter duration of contact & less traumatic blunt injury

• AC ( alternative current) tend to be three times more dangerous than DC due to continious muscle contraction

• flexor muscle contraction with exposure to AC prevent the victum from releasing his hand leading to prolong exposure

• Breief contact with DC can result in cardiac arrythmias

( tendes to through the victim from the source)

Resistance

Q:Which of the following tissues are the most resistant ?

• bone • nerve • muscle • blood vessel

• The higher is the resistance of tissue the greater transformation of electrical to thermal injuries

• Muscles & blood vessels has low resistance & good conductor

• Bone tendon & fat have high resistance & tend to heat & coagulate rather than transmit the current

• Callosed skin has more resistance than normal skin

• Moister & sweaty skin decrease the resistance

Resistance of body tissues

Most tendon Fat Bone

intermediate dry skin

Least Nerve BloodMuscle Membrane Muscle

Current ( Ampreage )( the measure of the amount of energy flows through an object )

• Remember I=V/R• The voltage of the sourse is known

but the resistance varies • The physical effect vary with

different amprage

"let go" current

• the maximum current at which a person can grasp the current and then release it before muscle tetany makes letting go impossible.

• child is 3-5 mA; this is well below the 15-30 A of common household circuit breakers.

adults, the "let go" current is 6-9 mA, slightly higher for men than for women

• The thoracic tetany occur just above the let

go current & result in respirator arrest • VF occur at an amperage of 60 to 120 • VF occur more with alternative current

while asystole with DC

Duration of contact

• The longer the duration they greater the electro thermal energy & tissue distraction in electrical injury

With lightening injury

• Short duration less skin damage flash over the current around the body

Voltage (the measure of diffrence in electrical potential between two points)

-depend on the source -the higher the voltage the more is tissue distraction - no fatalities with low voltage

500V or 1000V used as a cutpoint

Pathway ,which of the following is false:

• Current through heart & thorax can cause arrythmia & myocardial damage

• Cerebral current cause respiratory arrest & seizure

• Truncal current cause more damage than single digit current .

• Current passing through head & neack are more likely inducing cataract

• As the current density increase the tendency to flow to less resistance tissue is overcome

• With high voltage current the damage occur at a site distant from apparent contact area

• Electrical field strength = voltage /length

Histological changes

• Coagulation necrosis of muscles (periosteal , shortening of sarcomers)

• Vascular damage ( hemorrhage , thrombosis ,

progressive tissue necrosis)• Neural tissue damage ( Coagulation necrosis , compartment syndrome)

Mecechanism of injury ( Electrical injury )

1-Direct contact : Electrothermal heating

• Low voltage :limited to the affected area

• High voltage : burn any where along the current path

2-Indirect contact: Electrical Arc

• formed between two objects differing in potential , not in contact

• Result in deep thermal injury because of high temp of the electrical arc or sometimes flame burn or splashing across the entire body

• Flame: Ignition of clothing causes direct burns from flames.

• Flash: When heat from a nearby

electrical arc causes thermal burns but current does not actually enter the body

Lightning Injury

• Direct strike ( orifice entry )• Contact ( when a person touch an object

in the path way of lightning )

• Side flash ( lightning jump from primary strike

object to near by person)

• Ground current ( Difference in electrical potential

between person feet)• Blunt trauma (expulsive or impulsive force)

Clinical features : Head & neck Which of the following is false?

• Head & neck are common Points of high voltage injury

• Cataracts develop in 6% more typically short after the injury

• Tympanic membrane rupture occur in lightening injury

• Ocular injuries occur ( uveitis , iridocyclitis , vitrous hemorrhage & retenal detachment ) & the common is cataract

• Cardiac arrest from Asystole(lightening) or VF(electrical ) in electrical injuries

• Cardiac arrest from shock or induced vascular spasm in lightening injury

• Hypertension is commonly present after lightening injury.

Clinical features : cardiovascular

• All of the following are ecg changes in electrical injuries except :

• Transient ST elevation • Prolonged QT • Premature ventricular contaction• AF • Bundle brach block• VT AMI is rare ,, can be misdiagnosed due top high

CK

Clinical features : skinall of the following are true except ?

• deep burn occur in electrical injuries especially in hand & skull • heels are most common site of ground contact point • kissing burn commonly occur in extensor creases • electrical flash burn are superficial partial thickness • electrical injury burn is 10 % -25 % surface area • most common burn in children is mouth burn complicated by orbicularis oris muscular injury , labial artery damage , damage to developing dentition

deep burns occur in only 5% of lightening injury

superficial burns ( linear , punctate , feathering , thermal burns )

) flash/ferning.(

feathering

Clinical features : skin

17 years old boy, suffered injuries to both upper limbs caused by accidental contact with high-voltage electric current. Under medical care, he was transferred to our service on the day of the accident and continued treatment in our intensive care unit.

On the second day of treatment he was taken to the operating theatre and debridement of the wounds in the radiocarpal areas

day 3 there was clear evidence of full necrotic tissues also on all the fingers, which until then had been ischaemic ?

What is the mechanism explaining this finding • compartment syndrome • thrombus in brachial artery• nerve injury • vascular delayed hemorrhage

Clinical features : Extremities Electrical injury• Muscle necrosis might occur at area distant

from the skin injury point • Compartment syndrome is common • Renal failure is secondry to myoglobulinuria

Joints exhibit more severe injury than muscles,, why ?

Vascular injury should be assesed continiously ( thrombosis or hemorrhage )

Clinical features : Extremities

Lightening injury • Cause transient vasospasm ,, extremity

cold , blue, pulseless • Resolve spontiniously within hours

• Long bones fracture , shoulder dislocation migt occur .( rotator cuff muscle spasm )

Clinical features : Nervous system

Electrical injury: ( high voltage injury ) = transient LOC , confusion , flat

effect Short memory loss Seizure direct effect traumatic injury hypoxia

neurologicasl damage

immediateDelayed

Within hours

Weaknessparaesthesia

Days to years

Lateral sclerosisTransverse mylities Ascending paralysis

Q:which of the following statements regarding lightening strike is correct ?

• Absence of pupil reactivity is reliable examination confirming brain death

• In mass causality incidents involving lightening cardiopulmonary arrest victums mandate high priority

• Lower extremity paralysis is typically permanent

• Vitrous hemorrhage is the most frequently observed ocular sequale

• 25 years old man , after exposure of lightening injury was found to have lower limb paralysis that apper to be blue , mottled , cold & pulseless

• What immediate intervention is required:

- admit for serial perephral vascular examination

- immideiate surgical intervention - discharge home - observe in the emergency for 6 hrs i- perform radiological study to confirm diagnosis in ED

Neurological symptoms ( lightening )

• Keraunoparalysis( clear within hours)• Intracranial hemorrhage, seizure ,

loc Might occur

Management , prehospital :

Securing the scene

• Power source should be turned off

• Use of electrical gloves by medical personnale is dangerous

• DEnergizing the lines

• Triage should be concentrated on the presence of cardiac or respiratory arrest

• Patients require cardiac & trauma care

Remember

• ABCs• IV-O2 monitoring • Folyes catheter • NGT in severe injuryies

Fluid resusitation

• Al least 1 large bore cannula should be there

• Initial resuscitation by 20 ml /kg isotonic fluid

• Body surface area formulas for calculating fluid requirement is not applicable

• Lightening injury does not require fluid overload

Q: 2-years old girl a brought to ED found crying holding her right index finger, unprotecteted electrical wall socket was nearby visual inspection reveals localized areythema , good capillary refill , good pulses , full range of movement Chest auscultation reveals normal heart sounds , no other signs of trauma . What diagnostic test should be performed to complete the evaluation of this child ?• Urinalysis• Basic metabolic panel • chest x-ray• ECG• Arterial doppler

Monitoring :

• Cardiac monitoring is indicated in: • Cardiac arrest • Documented Loc • H/O cardiac disease • Suspicious of conductive injury • Hypoxia • Chest pain • A bnorml ECG

All patients require : • ECG• Cardiac enzymes• CT scan for victims with altered mentation or detororation of neurological status

Laboratory :• Cbc , ue 1 , urinalysis• Liver & pancreatic enzymes , coagulation if there is abd trauma• Check for myoglobulinuria• CK level ( predict muscle injury)• Radiological study according to the injured area

Specific therapy

Rhabdomyalisis • Urinary alkalinization• Mannitol & frusamide • Urine output maintained at 1-1.5 ml/kg/hr • Ph of blood maintained at 7.4 by sodium

carbonate

Burn wound care : • Dressing with silver sulfadiazine • TT• High dose of penicillin ( clostriridial myositis

Extremities injury • Spilint• Durgical amputaionSurgical wound care • Debridement• Skin grafts and flaps• Escharotomy• Fasciotomy:• Nerve release• ArthroplastyAmputation

• Disposition

Q: 4-years old boy represent after sticking a fork in to a home Electrical outlet with his right hand and get shocked . His right elbow was on the ground he remained asymptomatic physical examination reveals two extremely small first-degree burns on his right hand and elbow; a 12-lead ECG is normal . The most appropriate disposition is ? -admit to monitored bed for 24 hours - admit to non monitored bed for serial perephral vascular examination - discharge home - observe in the emergency for 6 hrs if no dysarrythmiias occur discharge home - perform echocardiography in ED

Disposition:which patient can be dischrged home ?

• 52 years old with high voltage current & chest pain

• 30 years old with low voltage injury, coetaneous burn & mild persistent symptoms

• 22years old man with lightening injury & altered mentation

• 60 years old man with low voltage exposure known to have cardiac illness but asymptomatic & normal ECG

• 3years old boy with electrical lip burn & non caring parents

Thank you