Electrical and Lightning Injuries. Electrical and Lightning Injuries : Lecture Outline ƒPhysics...

Electrical and Lightning

Injuries

Electrical and Lightning Injuries : Lecture Outline

ƒ Physics & pathophysiology of electrical injuries

ƒ Recognition, treatment, & prevention of :–Household current injuries–High voltage injuries–Lightning injuries

Electrical Burns : History

ƒ First commercial use of electricity : 1849

ƒ First reported fatal electrocution in 1879 in Lyon, France (250 volt AC dynamo)

ƒ First fatal electrocution in USA in 1881 : Sam Smith in Buffalo, NY

ƒ First use of electrocution for death penalty in 1890 : William Kimmler in New York

ƒ Kouwenhoven's studies at John Hopkins for ConEd of electrical injuries led to his development of the defibrillator

Electrical Injuries

ƒ Three main types :–Household current (110 to 220 Volts)–High voltage (> 1000 Volts)–Lightning

Electrical Line Voltages

ƒ Cross country lines : > 100,000 voltsƒ Residential & industrial area : 7620 voltsƒ Household heavy appliances : 220 or 240

volts–This voltage commonly used in Europe

ƒ Interior household lines : 110 to 120 volts alternating current : 60 cycles per second (hertz) in U.S.A. (is direct current instead in much of Europe)

Electricity Formulas

ƒ Energy (heat) = current times voltage Q = I X Eƒ Ohm's Law : Voltage = amperage X

resistanceƒ Joule's Law : Heat = amperage squared X

resist.ƒ Voltage = tension = potential =

electromotive forceƒ Amperage = intensity = current flow per

unit timeƒ Ohm = resistance

Human Tissue Electrical Resistance

ƒ Heavily calloused hand : 1 million ohms

ƒ Average skin : 5000 ohmsƒ Moist skin : 1000 ohmsƒ Internal resistance of the human

body : 500 ohms

Resistance of Tissues to Electrical Current

Least NerveBlood vesselMuscleSkinTendonFat

Greatest Bone

Electrical Burns : Physiologic Effects

60 hz Current Level Physiologic Effect 1 milliamp Threshold of sensation

10 milliamps Threshold of pain Muscle paralysis Breathing difficulty Ventricular fibrillation Severe burns 100 milliamps Breathing stops 1 amp Cardiac standstill 10 amps Defibrillation current

Electrical Current Flow Effects on Humans

ƒ Alternating current has a tetanizing effect on muscles–"Let-go current" (the current level at which the person is unable to release his grasp on the conductor) is 15 milliamps for men & 10 milliamps for women

ƒ Strong sustained muscle contraction can cause fractures

ƒ Direct current (DC) felt as heat only & can cause a single violent muscle contraction that can throw the victim from the power source

Household Current Injuries

ƒ In one series, caused half of all electrical deaths

ƒ Major risk is ventricular fibrillation (caused by the AC feature of current)

ƒ Deep tissue damage directly from the current is very rare

ƒ Can cause fractures and dislocations

ƒ If EKG normal & no skin burn, admission to hospital not necessary

Oral Cavity Electric Burns

ƒ 60 % in boysƒ Sucking extension cord socket : 54

%ƒ Biting on electric cord : 30 %ƒ Sucking an electric outlet : 2 %ƒ Temperature of electric arc : 2500

degrees F (> 1500 degrees C)–So usually these injuries represent more a thermal injury than an electrical current injury

Oral Cavity Electric Burns

ƒ Most involve lower lipƒ Can involve tongueƒ Complications :

–Drooling–Adhesions–Impaired speech–Tooth damage–Impaired mandible growth (rare)

Treatment of Oral Cavity Electric Burns

ƒ "Corner of mouth" burn from biting electric cord–Treatment by topical agent (like Silvadene) several times daily, custom-made mouth stretcher–No surgical treatment for at least 1 year–Warn parents about delayed bleeding if labial eschar sloughs off

Oral Cavity Electric Burns

ƒ Labial artery bleeding :–Occurs in 24 % of cases–1 to 21 days delayed–Usually stops with pressure–Rarely requires arterial ligation with suture

High Voltage Electrical Injuries : Demographics

ƒ 3 to 10 % of admissions to burn units

ƒ 10 to 15 % mortalityƒ ? > 1000 deaths / year in U.S.A.

High Voltage Electrical Injuries : People at Risk

ƒ Electric company linemenƒ Roofersƒ Agricultural workers (carrying

irrigation pipes)ƒ Parachutistsƒ Reckless teenagers (climbing

towers)ƒ Car drivers (hitting power poles)

Electrocution Risk

ƒ U.S. electric company linemen–33 per 100,000 workers per year

ƒ U.S. electricians–8.3 per 100,000 workers per year

ƒ Not well quantified for other higher risk groups (construction workers, heavy equipment operators, roofers, etc.)

Electrical Injuries (1982 Utah Study)

ƒ Number of high voltage injuries 68

ƒ Number injured from house current 8

ƒ Number injured from lightning 4

ƒ Number of electrical company linemen 14

ƒ Number of farm or ranch workers 22

ƒ Number of people injured on roofs 10

ƒ Number of construction workers 12

High Voltage Electrical Injuries : Pathologyƒ Causes coagulation necrosis of tissue

along current pathƒ Points of maximum destruction are at

skin entrance and exit sitesƒ May cause extensive muscle necrosis

in limb or trunk beneath unburned skinƒ May cause myocardial necrosis,

peripheral nerve injuries, bowel wall necrosis

ƒ Retrograde amnesia / confusion for several days common

Location of High Voltage Skin Injuries (1982 Utah Study)

Entrance Wounds Hand or Forearm Shoulder, Flank, Buttock Scalp, Face, Neck

54 patients 11 patients 13 patients

Exit Wounds One or Both Feet Back, Flank, Thigh

43 patients 29 patients

Associated Injuries (1982 Utah Study)

INJURY NUMBER Cardiac arrest requiring CPR * 11 Loss of consciousness > 15 minutes 13 Falls 11 Smoke inhalation 3 Femur fractures 2 Rib fractures 2 Skull fracture 1 Tibial fracture 1 Dislocated shoulder 1 Corneal abrasion 1 Lacerations 5

Total 51

* 10 of these were neurologically intact long term survivors

Resuscitation For High Voltage (HV) Electrical Burns

ƒ Turn off current ; remove patient from source (use nonconductive materials to push)

ƒ CPR (may need to be prolonged)–High neurologically intact survival rate

ƒ Immobilize spineƒ O2 , maintain airway, respiratory supportƒ IV LR : 4 to 12 cc / Kg / % burn / 24 hoursƒ Assess for other injuriesƒ NG, Foley, tetanus toxoid, Type & Cross ƒ IV antibiotics if muscle involvementƒ Emergent Tc99m muscle scanƒ To O.R. for fasciotomy & debridement

Resuscitation Fluid and Transfusions (1982 Utah Study)

ƒ Average amount of fluid received in first 24 hours : 9.9 liters or 12 cc / Kg / % burn

ƒ Range of amount of resuscitation fluid : 1.5 to 38 liters

ƒ Patients transfused with blood products : 41

ƒ Total units of blood used : 818ƒ Average units of blood used per

transfused patient : 20ƒ Units of fresh frozen plasma used :

195

Problems With Non-Visual Assessments of Muscle Viability

ƒ Angiography : cannot evaluate small muscle artery branches well

ƒ Fluorescein : cannot evaluate tissues beneath surface

ƒ Muscle biopsies : take too long to process and too many required

Tc99m (Technetium) Muscle Scan Interpretation

ƒ Cold (nonperfused) areas = dead muscle

ƒ Hot ( increased activity) areas = damaged muscle (20 % to 80 % fibers damaged)

ƒ Normal perfusion : areas that do not require visual inspection for viability

ƒ So Tc99m scanning, in conjunction with direct visual inspection, is the best way to assess muscle viability in electrical burns

26 year old male with high voltage burns ;

Technetium scan shows nonperfused muscle in apex of axilla

Technetium scan of same patient on previous slide showing nonperfusion of the thumb (so it must be amputated)

General Sequence of Surgical Care for High Voltage Electrical Burns

ƒ Resuscitation in EDƒ Tc99m muscle scanƒ To O.R. for fasciotomiesƒ Wound care in burn unitƒ Repeat trips to O.R. every 24 to 48

hours for debridementƒ Close fasciotomies with suture or

skin grafts when debridements complete

ƒ Rehabilitation

Benefits of Early Fasciotomy

ƒ Prevents decreased perfusion of limb tissue due to increased muscle compartment pressure

ƒ Allows visualization of muscle to assess viability

ƒ Probably helps preserve limb length when distal amputation is required

ƒ Not associated with significant increase in complications or infection

HV Electrical Burns : Indications for Emergent Surgical Decompression

ƒ Extensive deep limb burnsƒ "Mummified" distal extremityƒ Marked limb edemaƒ Decreased distal pulsesƒ Altered distal neurologic

functionƒ Delayed presentation

Fasciotomy : O.R. Technique

ƒ Do not use tourniquetƒ Check all hot and cold areas

noted on Tc99m scanƒ Do carpal tunnel release for

wrist involvement

Treatment Choices for Fasciotomy Sites Prior to Closure

ƒ Silvadene dressings : reapply q8h

ƒ Cadaver or pigskin graftsƒ Soaked dressings (saline with

antibiotics)

Closure Techniques for Fasciotomy Sites

ƒ Primary closure : only if edema gone and compartment pressure not increased

ƒ Split Thickness Skin Grafts (STSG's)

ƒ Rotated skin flapsƒ Free flaps

–Flaps often necessary when nerves or tendons are exposed

Same patient as on prior slide after fasciotomy showing extensive muscle damage under areas of unburned skin

High voltage entry wound of shoulder

Same patient as on prior slide, showing exit wound on right hand and “frozen” position of the limb from extensive muscle damage

Gross myoglobinuria from the same patient on the prior slide

High voltage contact injury to shoulder in another patient

High Voltage Electrical Injury : Complications

ƒ Acute MI / arrhythmiasƒ Renal failure

–This is really an iatrogenic problem & should be preventable if sufficient resuscitation fluid is given

ƒ Infections / sepsisƒ Peripheral neuropathyƒ Amputationsƒ Cataracts

Electrical Burns : Neurologic Complications

ƒ Mental confusion : 2 days to 3 weeksƒ Acute spasticity : may last 6 months to

1 yearƒ Reflex sympathetic dystrophyƒ Seizures ƒ Paralysis

uncommonƒ Causalgia

Electrical Burns : Infectious Complications

ƒ Sepsisƒ Pneumoniaƒ Osteomyelitisƒ Amputation stump cellulitis (if

this occurs, use Tc99m scan to locate necrotic muscle)

Electrical Injuries During Pregnancy

ƒ Only a few cases reported in the literature

ƒ True incidence of electric shock without any injury may be very high

ƒ Of the 15 cases reported since 1965, the incidence of stillbirth & major fetal anomalies was 14 / 15

ƒ No apparent increased risk to mother due to pregnancy itself

Electrical Burns Prevention

ƒ Don't be stupid !ƒ Turn power off at source before working on

wiring or applianceƒ Replace damaged electrical cords and

appliancesƒ Use non-conductive electric plug fillers when

children presentƒ Don't handle any electrical apparatus when

hands or area are wetƒ Use ground fault interrupter type outlets

wherever possible

Lightning

ƒ Essentially a sudden massive Direct Current (DC) shock (up to 1,000,000 volts and 200,000 amps)

ƒ ? Causes 300 to 600 deaths per year in U.S.

ƒ 1/3 of victims have serious injury or death

A picture I took of lightning in Reading, Pennsylvania

Lightning striking the World Trade Center

Fatal lightning strike site at the U.S. Open Golf Tournament

Airliner swerving to avoid lightning

Lightning Definition

ƒ The natural atmospheric electric discharge that occurs between regions of net positive and net negative charge

ƒ Usually associated with cumulonimbus clouds

ƒ May occur with : –Nimbostatus clouds–Snowstorms–Volcano gas

Lightning Incidence

ƒ 50,000 thunderstorms / day in world

ƒ 8 million lightning strikes per day

ƒ Causes more deaths than any other type of weather

ƒ Florida has much higher frequency than other U.S. states

World map of lightning frequency

Lightning Occurence

ƒ Does strike twice in the same place

ƒ A Virginia park ranger was hit 7 times over a 30 year period (he later committed suicide)

ƒ Tall buildings commonly receive multiple strikes each year

Therapeutic Effect of Lightning

ƒ The use of ECT (electroconvulsive therapy) for treatment of depression was suggested after a neurotic patient improved after being struck by lightning in 1890

Thunder

ƒ Caused by heating of air crossed by lightning

ƒ Cylindric column of air expands at supersonic speed

ƒ Shock wave decays to sound waveƒ Time from sighting flash to hearing

thunder allows calculation of distance to flash site (light : 186,000 miles per second, essentially instantaneous ; sound : 1100 feet per second or 300 meters per second)

Forms of Lightning

ƒ Streak (branching) : most common accounts for almost all injuries

ƒ Sheet : usually cloud to cloudƒ Ribbon (rare ; current isƒ Bead broken up)ƒ Ball : rarest

Sequence of Events Leading to Lightning Discharge

ƒ Air updrafts form ice particlesƒ Particle collisions build up static

electrical energyƒ Positive charge develops in upper

cloudsƒ Negative charge develops in lower

clouds and groundƒ When the potential difference

exceeds the insulating properties of the air, a flash occurs

Sequence of events leading to lightning formation

Lightning Structure

ƒ "Stepped leader" = current from cloud to ground

ƒ Upward current = return or pilot stroke ; meets the leader 50 meters above ground

ƒ Tip of leader releases heat and lightƒ Secondary leader and return strikes

occur (4 to 7 per stroke)

Lightning Injury : Types

ƒ Direct strike –High morbidity (since head is hit)

ƒ Splash current –On outside of body –Causes flame-like burns

ƒ Ground current–May cause mass casualities from one strike–Arrhythmias or asystole predominate

Lightning Injury : Skin Injuries

ƒ "Feathering" –Very common–Is superficial fern-like marks–Not a true skin burn–Disappear after a few days

ƒ 2nd or 3rd degree burns–Usually due to clothing fire or contact with heated metal

“Feathering” of the skin from lightning injury

Third degree skin burn (“charring”) from lightning

Second degree skin burns from vaporization of moisture on the skin by lightning

Differential Diagnosis of Lightning Injury

ƒ Cerebrovascular accidentƒ Seizure disorder (postictal)ƒ Closed head injuryƒ Spinal cord injuryƒ Hypertensive encephalopathyƒ Cardiac arrhythmiaƒ Myocardial infarctionƒ Toxic ingestion or intoxication

Treatment for Lightning Injury

ƒ Two different treatment regimens :–For most victims (who have deep tissue damage and / or flame burns on skin)

ƒ Same scheme as for high voltage injuries (high volume fluid resuscitation , Tc99m scan, fasciotomy, etc.)

–For victims who just have "CNS stunning" treat same as for head trauma with increased ICP (fluid restriction, hyperventilation, etc)

ƒ In both groups TM perforation is common (need otic gtts & E.N.T. followup)

Lightning Injury Triage Principle

ƒ If multiple victims, ignore the ones who are moving and awake, and concentrate evaluation and care on the ones who may be arrested (even prolonged CPR often successful for these victims)

Lightning Injury

ƒ Factors unrelated to mortality :–Sex–Age–Trunk or arm burns

ƒ Factors related to mortality :–Leg and head burns–Immediate cardiopulmonary arrest

Lightning Injury : Neurologic Effects

ƒ Loss of consciousness : 72 % of cases

ƒ Paralysis of respiratory center ; leads to apnea

ƒ Rarely : rapid cerebral edema and even brainstem herniation

ƒ Transient motor paralysis : 70 %ƒ Mechanical trauma : skull fracture,

intracranial hematomas

Lightning Injury : Cardiac Effects

ƒ Depolarizes entire myocardium at onceƒ Single systolic contraction ; leads to

asystole ƒ Then return of cardiac function

(bradycardia)ƒ If apnea however, leads to hypoxia,

then ventricular fibrillationƒ May show EKG changes c/w acute MI

without coronary artery occlusionƒ May have vasomotor spasm &

prolonged arterial vasoconstriction

Lightning Injury : Ocular and Otic Effects

ƒ Cataracts : most common effect–May appear 6 weeks to 24 months after–Usually bilateral–Also common after HV electrical injury

ƒ Retinal detachment : uncommonƒ Lid burnsƒ Keratitis : may be severeƒ Direct current damage to inner ear or

auditory nerveƒ Tympanic memebrane rupture in up to

50 %–Due to proximity of thunder noise generation

Lightning Injury : Other Effects

ƒ Muscle necrosis or rupturesƒ Myoglobinuric renal failureƒ Ileusƒ GI bleedingƒ Pancreatic hemorrhage /

necrosisƒ Thunder phobia

Risk Factors for Direct Strike by Lightning

ƒ Outsideƒ Carrying a metal objectƒ Any metal object (hairpin or

helmet) even if small, on headƒ No taller objects in the vicinity

Lightning Injury Prevention

ƒ If outside :–Avoid being the tallest object in the vicinity–Avoid hilltops, poles, towers, trees–If in a group, spread out–Avoid wet soil–Lie flat and curled up–Stay away from metal equipment–If your hair stands on end, run from the area right away (you've been targeted !)

National Weather Service “30/30 Rule” for Lightning

• If you can’t count to 30 between seeing the lightning and hearing the thunder, then you should go to a safe sheltered location

• Don’t return outdoors until 30 minutes after the last sound of thunder

Lightning Injury Prevention

ƒ If inside :–Stay away from radiators, stoves, appliances, gas and water pipes–Avoid showering or bathing until storm over–Do not use the phone–Stay away from the fireplace

Electrical and Lightning Injuries : Summary

ƒ Start cardiac monitoring & fluid resuscitation early

ƒ Use Tc99m scan to guide early surgical therapy for HV injuries

ƒ For lightning, determine if patient has HV-like injuries or just "CNS stunning" since the Rx is different for these 2 types

ƒ Prevention, mainly common sense measures, is effective for both