Transcript Frostbite Gang Wang M.D.

Electrical Injures
LENG RUPU
EPIDEMIOLOGY
The first report of electrical injury from man-made
sources occurred in 1746 after the development of the
capacitor.
The first recorded death due to electrical current
from a man-made source was reported in 1879, when
a carpenter in Lyons, France, inadvertently contacted
a 250- volt AC dynamo. The first U. S. fatality
occured in 1881, when a local inebriate, Samuel W.
Smith, passed out on a generator in front of a crowd
in Buffalo, New York.
The apparent painlessness of his death impressed
the crowd, and electrocution began to be thought of as
a “humane” mode of execution. In 1890 William
Kemmeler became the first man to be put to death in
New York State's electric chair.
Electrical burns account for 4% to 6.5% of all
admissions to burn units
PATHOPHYSIOLOGY
The exact pathophysiology of electrical injury is not
well understood because of the large number of
variables that cannot be measured or controlled when
an electrical current passes through tissue. Most of the
injury appears to be thermal, and most histologic
studies reveal coagulation necrosis consistent with
thermal injury. A magnetic field exists wherever an
electric current passes, there may be magnetic effects.
Factors Determining Electrical Injury
Type of circuit
Resistance of tissues
Amperage
Voltage
Current pathway
Duration
Environmental factors
Type of Circuit
The type of circuit, alternating current (AC) vs.
Direct current (DC), will help to determine the
severity of the injury. High-voltage DC tends to
cause a single muscle spasm, often throwing the
victim from the source. This results in a shorter
duration of exposure but increases the likelihood of
traumatic blunt injury. It is well-known that contact
with a DC source can result in disturbances in
cardiac rhythm, depending on the phase of the
cardiac cycle affected, a phenomenon that is utilized
in the common defibrillator.
AC tends to be three times more dangerous than
direct current of the same voltage.
The hand is frequently the site of entry as it grasps
a tool that comes into contact with an electric source.
Because the flexors of the hand and forearm are
much stronger than the extensors, contraction of the
flexors at the wrist, elbow, and shoulder occur,
causing the hand holding onto the current source to
pull the source even closer to the body. At currents
above the let-go threshold (6 to 9 mA) this can result
in the victim's being unable to voluntarily release the
current source, prolonging the duration of exposure
to the electrical current.
Resistance
The Row of electrical energy through a substance is
described by Ohm‘s law:
R = V/I
Resistence(R) of a tissue , electrical energy(I) to
thermal energy(P) at any given current as described
by Joule's Law:
P=I2×R
Duration
In general the longer the duration of contact, the
greater the degree of tissue destruction.
Current
Current, expressed in amperes, is a measure of the
amount of energy that flows through an object.
Voltage
Voltage is a measure of potential difference
between two points and is determined by the
electrical source.
Effects of Amperage Levels in Milli-amperes (mA)
Tingling sensation
1-4
Let-go current
Children
4
Women
7
Men
9
Freezing to circuit
10-20
Respiratory arrest from thoracic muscle tetany 20-50
Ventricular fibrillation
50-100
Pathway
The pathway that a current takes determines the tissues
at risk, the type of injury seen, and the degree of
conversion of electrical energy to heat. Current passing
through the heart or thorax can cause cardiac
dysrhythmias and direct myocardial damage.
Current passing through the brain can result in
respiratory arrest, seizures, and paralysis.
Current passing close to the eyes can cause cataracts.
It has been suggested that current flowing through the
left side of the body may be more dangerous than
through the right side or one isolated to an extremity.
As the cross-sectional diameter of the tissue a given
current passes through increases the less heat is
generated, and less damage occurs as the energy is
``diluted‘’ by the tissue.
Because the current is often concentrated at the
entrance and exit sites, the greatest degree of damage
is often observed there, although deep destruction of
the tissues in between may often occur, leading some
to describe the surface damage as only ``the tip of
the iceberg”.
MECHANISMS OF INJURY
The mechanisms of electrical injury are listed in the
box below. Obviously the victim who becomes part of
an electrical circuit, particularly if it is of high voltage,
may suffer significant injury. Nonconductive thermal
injury can occur by several mechanisms.
The most destructive indirect injury occurs when a
victim becomes part of an electrical arc. it can cause
very deep thermal burns . Sometimes the arc may
cause clothing to ignite, resulting in secondary thermal
burns. The electrical flash burn. a third mechanism of
nonconductive injury, usually results in only superficial
partial thickness.
Traumatic injury is frequently seen in patients
sustaining electrical injury because they may be
thrown clear of the source by intense contraction of
their muscles or by falling from a height.
The histologic changes seen in muscle injury are
coagulation necrosis with shortening of the sarcomere.
Vascular damage is greatest in the media, possibly
because of the diffusion of heat away from the intima
by the flow of blood, but can lead to delayed
hemorrhage when the vessel eventually breaks down.
Intimal damage may result in either immediate or
delayed thrombosis and vascular occlusion
Damage to neural tissue may occur from many
mechanisms. It may show an immediate drop in
conductivity as it undergoes coagulation necrosis similar
to that observed in muscle tissue. In addition, it may
suffer indirect damage as its vascular supply or myelin
sheath is injured.
The brain is frequently injured, focal petechial
hemorrhages in the brainstem, widespread chromatolysis,
and cerebral edema.
Immediate death in electrical injury may be from
asystole, ventricullar fibrillation, or respiratory
paralysis, depending on the voltage and pathway.
Mechanisms of Injury
Direct contact
Arc
Flash
Thermal
Blunt trauma
CLINICAL FINDINGS
Prehospital Considerations
When first reaching the scene, paramedic personnel
should secure the area so that no other injuries can occur
to bystanders or rescuers. It is essential that the power
source be turned off. Although many approaches to this
have been touted, Use of electrical gloves by emergency
medical service (EMS) groups has been condemned,
A downed high-tension line may jump as it repowers
periodically (similar to a water hose that jumps when
turned off and on) and may land anywhere in its radius,
causing more injuries. Therefore the rescue vehicle
should park at least one entire span away from the line.
The victim of an electrical incident should be
approached like any other trauma patient because the
person may have suffered injury as a result of violent
muscle contraction or a fall, in addition to having
severe burns that are often more extensive than they
initially appear. Attention should be paid to the
airway, breathing, and circulation. High-flow
oxygen and intubation should be provided if
necessary. Cardiac monitoring is essential. If the
victim has experienced cardiac arrest, standard
advanced life support protocols should be instituted.
Emergency Department Assessment
History.
Specific injuries:
Cardiovascular System. Cardiac arrest, either
from asystole or ventricular fibrillation, is a common
presenting condition in electrical accidents.
Skin. Skin injury are burns. The most common
sites of entry for the current include the hands and
the skull. The most common areas of exit are the
heels. painless, depressed, yellow-grey, punctate
areas with central necrosis.
Extremities. Muscle necrosis can extent to sites
distant from the observed skin injury, and compartment
syndromes can occur secondary to vascular ischemia
and muscle edema. Massive release of myoglobin from
the damaged muscle may lead to myoglobinuric renal
failure.
Vascular damage Damage to the vessel wall at the
time of injury can result in delayed thrombosis and
hemorrhage, especially in the small arteries to the
muscle. Progressive loss of muscle because of vascular
ischemia downstream from damaged vessels may lead
to the need for repeated deep debridements.
“kissing burn”--a peculiar type of burn-- occurs at the
flexor creases.
Nervous System. Loss of consciousness is common
and usually transient, Patients may exhibit confusion
flat affect, and difficulty with short-term memory and
concentration. A seizure may occur after electrical
injury . Peripheral nerve damage in extremities
sustaining injury is common, and recovery is usually
poor.
Other Viscera.
Skeletal System.
Eyes. Cataracts develop in approximately 6% of
cases
Mouth. Mouth burns secondary to sucking on
household electrical extension cords are the most
common electrical injury seen in children under 4
years of age.
Complications
Primary Complications and Causes of
Death in order of Occurrence
Cardiopulmonary arrest
Overwhelming injuries
Cardiac arrhythmias
Hypoxia and electrolytes
Intracranial injuries
Myoglobinuric renal failure
Abdominal injuries
Sepsis
Tetanus
Iatrogenic
Suicide
TREATMENT
Resuscitation. Once the accident scene is controlled.
a quick initial assessment of the patient is indicated,
with attention to the airway, breathing, and circulation.
Cardiac monitoring is helpful and cardiopulmonary
resuscitation (CPR) should be initiated, if indicated,
with institution of advanced life support.
Cardiac monitoring is more controversial and is
probably only necessary for the severely injured
patient and for those who have the indications listed
in the Box below.
Indication for Electrocardiographic Monitoring
Cardiac arrest
Documented loss of consiousness
Abnormal ECG
Dysrhythmia observed in prehospital or emergency department setting
History of cardiac disease
Presence of significant risk factors for cardiac disease
Concommitant injury severe enough to warrant addmission
Suspicion of conductive injury
Hypoxia
Chest pain
Rhabdomyolysis. Patients with heme pigment in the
urine should be treated as though they have
myoglobinuria.
Burn Wound Care.
Extremity Injuries. The current trend with regard to
damaged extremities favors early and aggressive
surgical management, including early decompressive
escharotomy, fasciotomy, carpal tunnel release, or
even amputation of an obviously nonviable extremity.
Extremities should be splinted in functional position to
minimize edema and contracture formation.
DISPOSITION
All patients with significant electrical burns
should be stabilized and transferred to a regional burn
center if possible.
Electrical injury during pregnancy from low
voltage sources has been reported to result in
stillbirth. Obstetric consultation should probably be
obtained in all pregnant patients reporting electrical
injury,
Treatment of pediatric patients with oral burns is
more controversial. In general, these patients need
surgical and dental consultation for planning of
debridement, oral splinting and occasionally,
reconstructive surgery.
Lightning Injuries
EPlDEMlOLOGY
As would be expected, lightning incidents are most
common where there are more thunderstorms,
They also occur more frequently during the times
that people tend to be outdoors, in the afternoon and
early evening, and during the thunderstorm season,
May to September.
Lightning incidents were once most frequently
reported among farmers.
With the population shift to the cities, where
lightning strikes are less frequent, those most
commonly reported in lightning incidents are campers,
joggers and other athletes, and construction workers.
LIGHTNING PRODUCTION
Lightning is produced from the static charges that
occur as a cold high-pressure front moves over a
warm, moist, low-pressure area. The warm, moist air
rises through the cold air, allowing the moisture to
condense into a cloud. The friction of moving air
particles within the cloud causes ionization and
complicated energy changes .
In most cases the lightning begins as a leader
stroke from a cloud and takes a slow, jagged,
irregular path downward the oppositely charged earth
below the storm cloud.
A pilot stroke rising from ground upward cloud
cause the column of ionized air to flicker and
brighten momentarily as massive amounts of energy
are discharged. Although the majority of the
lightning discharge occurs in an upward direction,
lightning is perceived as a downward stroke because
of the irregular, weak, slower leader stroke.
MYTHS AND MISTREATMENTS
From ancient times lightning has played a prominent
part in the religions and folklore of many cultures,
giving rise to many superstitions and myths.
Unfortunately many of these myths persist today,
including some in the medical literature. They include:
1. Lightning is always fatal.
2. Lightning burns can turn victims into “crispy critters”.
3. Lightning never strikes in the same place twice.
4. Victims of lightning strikes remain electrified.
5. The bodies of victims of lightning strikes can remain in
“suspended animation”.
6. Lightning injuries are like other high-voltage injuries.
Because of the general lack of experience of most
urban physicians with lightning injuries, a great deal
of confusion exists between lightning injuries and
other high-voltage electrical injuries. Usually much
less energy is imparted to the lightning victim than to
the victim of regular high-voltage exposure, and
consequently far less injury occurs. Although the
body's electrical systems may be short-circuited by
lightning, resulting in cardiac arrest, tinnitus,
temporary blindness, and paralysis, injuries typical of
man-made high-voltage electricity such as burns,
myoglobinuria, and deep-muscle damage are rare.
PATHOPHYSIOLOGY OF
LIGHTNING INJURY
Mechanisms of Lightning Injury
Direct strike
Contact
Side flash, "splash"
Ground current or step voltage
Blunt trauma
A direct strike is self-evident. Injury from contact
occurs when the person is touching an object that is
part of the pathway of lightning current. Side flash or
splash occurs as lightning jumps from its pathway to a
nearby person.
Step voltage occurs as a result of lightning current
spreading radially through the ground. A person who
has one foot closer than the other to the strike point
will have a potential difference between his or her feet
so that a current may be induced through the legs and
body. This is a frequent killer of large livestock such as
cattle and horses because of the distance between their
hindlegs and forelegs.
Blunt injury can occur from two mechanisms. (1) the
person may be thrown a considerable distance by the
opisthotonic contraction caused by current passing
through the body or (2) from the explosive/implosive
force caused as the lightning pathway is instantaneously
superheated and then rapidly cooled after the passage of
the lightning is over. The heating is seldom long enough
to cause severe burns but does cause rapid expansion of
air followed by rapid implosion of the cooled air as it
rushes back into the void.
Factors Governing Electrical Injuries
Type of circuit(AC or DC)
Duration
Voltage
Amperage
Resistance of tissues
Pathway
Not only is there an absolute energy difference, but
the duration of lightning is so incredibly short that
the energy seldom has time to break down the skin
and cause any significant internal current flow or
tissue damage. Thus the pathway is also different. As
with metal conductors, the vast majority of the
current travels around the outside of the conductor,
``flashing over'' the outside of the victim.
Although a small amount of current may leak
internally, causing short-circuiting of electrical
systems such as the heart, respiratory centers, and
autonomic nervous system or causing spasm of
arteries and muscles, lightning seldom causes any
significant burns or tissue destruction. Thus burns
and myoglobinuric renal failure play a small part
in the injury pattern, whereas cardiac and
respiratory arrest, vascular spasm, and autonomic
instability play a much greater role.
PREHOSPlTAL
CONSIDERATIONS
The prehospital personnel must remember that
lightning can strike the same place twice and guard
themselves against also becoming victims.
The major cause of death in lightning injuries is
cardiorespiratory arrest. victims are unlikely to die
of any other cause. Thus triage of lightning victims
should concentrate on those who appear to be in
cardiorespiratory arrest. Lightning acts as a
massive DC countershock, sending the heart into
asystole. Although automaticity may lead to the
heart restarting, the respiratory arrest often lasts
longer than the cardiac pause and may lead to a
secondary cardiac arrest with ventricular
fibrillation from hypoxia.
CLINICAL FINDINGS
Patients may present with little evidence of injury
or, alternately, cardiopulmonary arrest. After initial
resuscitation, additional, rarely life-threatening,
conditions may be identified.
Head and Neck. including skull fractures, Over
50% of victims have at least 1 tympanic membrane
ruptured. Although most recover without serious
sequelae, disruption of the ossicles and mastoid may
occur, as well as cerebrospinal fluid otorrhea,
hemotympanum, and permanent deafness.
Cataracts may occur. Other injuries to the eyes may
occur.Cervical spine injury may be caused by a fall or
being thrown.
Cardiopulmonary. Pulmonary contusion and
hemorrhage have been reported. Cardiac damage or
arrest caused by either the electrical shock or induced
vascular spasm may occur. Numerous dysrhythmias
have been reported in the absence of cardiac arrest.
Nonspecific ST-T wave-segment changes may occur,
and serum levels of cardiac enzymes are sometimes
elevated. Hypertension is often present initially but
usually resolves in an hour or two so that treatment is
not usually
Abdominal. Blunt abdominal injuries have been
reported but are rare. None of the other intraabdominal
catastrophies associated with electrical injury (e.g. gallbladder necrosis, mesenteric thrombosis) have been
reported with lightning injury.
Extremities. On initial presentation, two-thirds of the
seriously injured patients have keraunoparalysis with
lower and sometimes upper extremities that are blue,
mottled, cold, and pulseless because of vascular spasm
and sympathetic nervous system instability. Generally
this clears within a few hours, although some patients
may be left with permanent paresis or paresthesias.
Skin. The skin may show no signs of injury initially.
Deep burns occur in less than 5% of the reported
injuries. As mentioned previously, burns are usually
superficial, if present at all. They consist of four types
(see box below and Fig. 1).
Lightning Burns
Linear
Punctate
Feathering (ferning)
Thermal
COMPLICATIONS
Complications of lightning injury fall into two areas.
(1) those which could be reasonably predicted from the
presenting signs and which can be treated routinely (i.
e., hearing loss from tympanic membrane rupture,
paresthesias and paresis from neurologic damage) and
(2) those complications which are iatrogenically
caused by over-aggressive management.
Lightning injuries tend to cause few external or internal
burns, rarely myoglobulinuria, and little tissue loss,
although there may certainly be permanent functional
impairment. As a result, treatment of lightning victims
seldom requires massive fluid resuscitation, fasciotomies
for compartment syndromes, mannitol and furosemide
diuretics, alkalinization of the urine, amputations, or
large repeated debridements. In fact, most lightning
victims, particularly those with head injuries, should
probably have their fluids restricted to decrease the
likelihood of cerebral edema.
DIFFERENTIAL DIAGNOSIS
Differential Diagnosis
Cardiac dysrhythmias
Myocardial infarction
Cerebrovascular accident
Subarachnoid hemorrhage
Seizures
Closed-head injury
Spinal cord trauma
Tick-bite paralysis
Heavy-metal poisoning
TREATMENT
Initial care must be given to the ABCs (airway,
breathing, and circulation), with primary attention
going to those in cardiac arrest or near arrest.
All victims should be transported to a hospital and
receive an ECG, cardiac isoenzyme level study,
urinalysis for myoglobin, and other tests and x-ray
studies as appropriate for their injuries. Most should
be monitored for 24 hours and receive standard
antidysrhythmia medications if they develop any
signs of cardiac irritability.
The vast majority of lightning victims will behave
as though they have had electroconvulsive
psychiatric therapy and will be confused and have
an anterograde amnesia covering several days after
the incident. If any neurologic deterioration occurs,
CT or MRI scanning is indicated to rule out
intracranial hemorrhage.
Long-term sequelae include insomnia and other
sleep disturbances, anxiety attacks, decrease in
fine mental functions, fear of storms, and
paresthesias and paresis of affected extremities.