Electric current

1. Electric Injury
ZHADAN S.A. PhD
BELARUSIAN STATE MEDICAL UNIVERSITY
PATHOPHYSIOLOGY DEPARTMENT

2.  Electric Injury (EI) is the damage
caused by electric current effect on an
organism, characterized by damage and
dysfunctionof tissues and organs
Definition

3. Electric Current Features
The electric current:
1. is invisible, has neither smell, nor color, operates silently;
2. is able to turn to other kinds of energy (mechanical, chemical, thermal, and biological);
3. is not detected without special devices;
4. has a damaging effect:
5. damages tissues on the whole way of its passage through a body, not in place of touching only;
6. has discrepancy between severity of damages and duration of its influence;
- at direct contact;
- through subjects;
- on distance

4. The Reasons of Electric Injuries (1)
 imperfection and malfunction of protective adaptations and isolation,
 violation of precaution rules

5. The Reasons of Electric Injuries (2)
- indiscretion
- prank
- isolation damage - negligence
- accidents - mischief

6. The Reasons of Electric Injuries (3)
- direct contact or contact through other conductor
- inexperience

7. The Reasons of Electric Injuries (4)
- spark categories - lightning striking

8. Changes in an organism in case of electric current traumas depend on:
1. Physical characteristic of electric current (V, R, I etc);
2. Condition of an organism at the moment of EC injury:
o the states of sleeping, narcosis, “attention factor”, alcoholic intoxication lead to decrease of severity;
o the states of hypothyroidism, fatigue, illness, edema cause increase of electric injury severity
3. Environmental factors
(↑T◦C, high atmospheric pressure and high humidity - increase of electric injury
severity and vice versa)
Factors Determining EI

9.  voltage (V)
 current strength (I = V/R)
 resistance of tissues (R)
 type of circuit (alternating or direct)
 duration of current effect
 pathway of current distribution in an organism, etc
Physical characteristics of Electric
Current

10. Resistance of Body Tissues
Resistance is the tendency of a material to resist
the flow of electric current
Tissue resistance depends on:
 its moisture content;
 temperature;
 other physical properties

11. Least resistance
Nerves
Blood
Mucous membranes
Muscle
Intermediate
Dry skin
Tendon
Fat
Most
Bone
The higher the resistance of a tissue to a current flow,
the greater the potential for transformation of electrical
energy to thermal energy
Least resistance
Nerves
Blood
Mucous membranes
Muscle
Intermediate
Dry skin
Tendon
Fat

12. Type of Circuit
direct current alternating current
A current in one direction only
is called a direct current, or DC
If a current changes direction repeatedly
it is called an alternating current, or AC
What currents are more dangerous?
An alternating current exposure to the same voltage tends to be three times more dangerous
than a direct current (40–100 Hz)
With frequency increase damaging effect of a current decreases
Currents of high frequency even at a high voltage are not dangerous and are applied in
medicine

13.  The alternating current of voltage up to 500 V is more
dangerous, than a direct current of the same voltage
At voltage of 500 V damaging effect of an alternating
and a direct current are approximately equal
At voltage of more than 500 V direct current becomes
more dangerous, than alternating one
What voltage is more dangerous?

14. Duration of Contact
Electric current damaging effect is defined by duration of
its action; this effect is amplified with duration of action
Passage of a high-tension current and a big strength
during 0,1 second and less do not always causes death
At the same time current effect of the same strength and
voltage during 1 second always causes lethal outcome

15. Pathways of Current Distribution
For a damage outcome ways of electric current
distribution – “current loops” have a great value.
The current extends to body tissues from input place to
output place.
The passage of a current through the brain and heart is
considered to be the most dangerous to an organism
(at the beginning diastole).

16. Kinds of Current
Loops
 The bottom loop (8) (from foot to foot) – the least dangerous
 The top loop (2) (from hand to hand) – more dangerous
 The full loop (10) (both hands and both feet) – the most dangerous because current passes
through the heart
The most probable
pathways of
current:

17. The lethal outcome can come at all kinds of
loops since an electric current, passing through
an organism, irritates all receptors lying on its
way.
In case the current passes through all systems
and bodies, the nervous and cardiovascular
systems suffer the most.

18. There are three mainstreams of electrocurrent
distribution in an organism:
 blood vessels
 muscular tissue
 nervous trunks

19. Mechanisms of
Electrical Injury
NONSPECIFIC EFFECTS SPECIFIC EFFECTS

20. Mechanisms of Electrical Injury
NONSPECIFIC EFFECTS
Nonspecific effects of a current are the effects caused by other
forms of energy to which the electricity may be transformed passing
out through an organism
Examples of nonspecific effects:
- heated metal conductors;
- volt arches (400 c);
- burning of clothes;
- gas explosion.

21. SPECIFIC EFFECTS:

22. Biological Electric Current
Effects

23. Biological Current Effects
Biological current effect is the effect that influences the excitable tissues and
first of all on the nervous system and the internal secretion organs.
They are expressed in:
• emission of catecholamines (adrenaline, noradrenaline) in a considerable quantity;
• changes in somatic and visceral organism functions;
• excitation and tonic spasms of skeletal and smooth muscles;
• changes in sodium-potassium gradient of cells, membrane potentials, etc.

24. Electrochemical
Electric Current Effect

25. Electrochemical Current Effect
Electrochemical (electrolytic) current effect is an effect that causes:
 electrolysis;
 infringement of ionic balance in cells;
 changes in transmembrane potential.
Electrolysis leads to:
• polarization of cellular membranes;
• changes in functional state of cells;
• movement of protein molecules leading to:
 coagulation of tissues (coagulation necrosis)
 swelling colloids (colliquative necrosis)

26. Electrothermal
Electric Current Effects

27. Electrothermal Current Effects
Electrothermal current effect is caused by transition of
electric energy in thermal energy with allocation of a
considerable quantity of heat.
As a result there are skin damages – signs of current
(electro labels) revealed by the following features:
 coagulation sites of epidermis
 the round or oval form
 grey-white color
 the firm consistence
 bordered bolster-like eminence
 become ingrained in the center

28. Direct contact
Electro thermal heating
Indirect contact
Arc
Flame
Flash
Types of Electrical Burns

29. Electrical burns are divided into 4
degrees:
 first-degree burn – skin reddening and signs of a current (electro labels)
 second-degree burn – epidermis exfoliation with vesicle formation
 third-degree burn – coagulation of the whole derma thickness
 fourth-degree burn – damage caused not only to derma, but also
to tendons, muscles, vessels, nerves, bones (up to carbonization)

30. Electrical burns have the following features
distinguishing them from thermal burns:
 they usually arise in places of current entry;
 skin gets various coloring depending on a conductor kind;
 minor soreness or absence of pain
(anaesthetizing effect of a current);
 heals much better, than in case of thermal burns;
 wounds are without the tendency to suppuration.
Thermal burn
Electrical burn

31. Electromechanical Current Effects
Electromechanical (dynamic) current damage can be caused in two ways:
• by means of direct transition of the electric power to mechanical energy
• by the effect of formed steam and gas
 stratification of tissues
 separation of body parts
 formation of cut wounds
 crises of bones
 dislocations of joints
 traumas of skull
 brain concussion etc.
They may result in:

32. EI Patterns of
Injury

33. Skin - flash burns, thermal burns, arc burns, contact electrical burns;
Muscle – swelling, pain, contractions, spasms, necrosis of muscles,
compartment syndrome;
Blood vessels – blood cloths, microvascular deterioration, myoglobinemia,
vasoconstriction, thrombosis, ischemia;
Heart – arrhythmia, asystole, ventricular fibrillation, sinus tachycardia,
myocardial necrosis/infarction, cardiac arrest;
Kidney – myoglobinuria, acute renal failure, acute tubular necrosis.
EI Patterns of Injury (1)

34. Nerves – weakness, paralysis, tingling, numbness, uncontrollable loss of
urine (incontinence), and chronic pain
Brain – seizures, hemorrhages, poor short-term memory,
unconsciousness, ischemia, personality changes, irritability, difficulty
in sleeping
Bones – joint dislocations, fractures, other blunt injuries
Ears – perforation of the eardrum, hemorrhage
Eyes - cataracts
EI Patterns of Injury (2)

35. Causes of death
from current

36. Causes of death from current
The death from current can come from:
 primary cardiac arrest (the cardiac form of death)
 primary respiratory standstill (the respiratory form of death)
 simultaneous cardiac and respiratory arrest
(the mixed form of death)
 electric shock (!)

37. The Cardiac Form of Death
The cardiac form of death can be caused by:
 irreversible fibrillation of heart
 spasms of coronary arteries
 damage of the vasomotor center
 elevation of the vagus nerve tone

38. The Respiratory Form of Death
The respiratory form of death can be caused by:
 braking or paralysis of the respiratory centre
 convulsive reduction of respiratory muscles
 spasms of vertebrae arteries supplying the respiratory center
 electric asphyxia (child-crowing)

39. Electric Shock
At electric shock the relationship of the basic nervous processes
(excitation and inhibition) is broken
Causes:
• Touching
o a high-voltage source, such as high-tension wires that fall during a storm
o someone who is still touching a live current
o a low-voltage current source, such as an electric socket or worn cord
o mixing water and electricity
• Being struck by lightning. A bolt of lightning carries as many as 30 million volts
The shock arises at a short-term touch to a current carrying subject in
victim if fibrillation does not develop and breath does not stop

40. Two phases of electrotraumatic shock
The stage of excitation:
• excitation of the central nervous
system;
• increase of arterial and venous
pressure;
• short breathing;
• spasms;
• involuntary urination;
• defecation
The stage of inhibition:
• inhibition of the central nervous
system;
• sharp decrease in a blood pressure;
• breath breaking;
• suppression of all vital functions up
to loss of consciousness;
• disappearance of reflexes

41. Lightning Injury

42. Direct strike
Orifice entry
Contact
Side flash, “splash”
Ground current or step
voltage
Blunt trauma
Mechanisms of Lightning Injury
Causes of injuries from contact:
 touching an object that is part of the pathway of lightning current (single tree or tent
pole);
 side flash or splash (lightning jumps from its primary strike object to a nearby
person on its way to ground);
 step voltage.

43. Step voltage is a difference in electrical potential between a
person’s feet (may occur as lightning current spreads radially
through the ground).
A person is a much better conductor of electricity than the earth.
Thus a person who has one foot closer than the other to the
strike point will have a potential difference between the feet so
that the lightning current will preferentially flow through the legs
and body rather than the ground

44. Blunt injury from lightning can occur in two ways:
First, the person may be thrown at a considerable distance by a sudden,
massive contraction caused by current passing through the body
Second, an explosive or implosive force occurring as the lightning passes
through a superheated and then rapidly cooled object following the passage of
the lightning.
The heating seldom lasts long enough to cause severe burns but it may cause
rapid expansion of air followed by rapid implosion of the cooled air leading to
rupture of inner organs
Mechanisms of Lightning Injures

45. When lightning strikes a person:
Only about 20% of people die instantly from lightning strikes.
Other interesting facts about lightning strikes include:
Pollution causes an increase in lightning strikes.
Lightning strikes increase by 25% during the working week.
A bolt of lightning can heat air around it to 50,000 °F.
A lightning bolt can contain 100,000,000 volts of electricity and be
more than 5 miles long.
There’s an average of 25,000,000 lightning strikes every year
(U.S.).
On average, 67 people die from lightning strikes in the U.S. every
year.
A lightning bolt can travel at 60,000 miles per second.
80% of all people struck by lightning survive. Although, they often
have long-term injuries.
The back of a man who was
struck by lightning. There’s a
reddish feathery pattern from
the striking point to the exit
point of the bolt.

46. Late complications:
 Muscle fibrosis
 Peripheral neuropathies
 Loss of tissue from debridement
 Joint stiffness
 Reflex sympathetic dystrophy
 Cataracts
 Paraplegia
 Quadriplegia
 Subtle mental changes

47. 1. If safely possible:
Simply turning off an appliance may NOT stop the flow of electricity
2. Call for medical help. 
• shut off the electrical current
• unplug the cord
• remove the fuse from the fuse box
• or turn off the circuit breakers

48. 3. If the current can't be turned off, use a non-conducting object, such as a
broom, chair, rug, or rubber doormat to push the victim away from the source
of the current. Do NOT use a wet or metal object. If possible, stand on
something dry and non-conducting, such as a mat or folded newspapers. Do
NOT attempt to rescue a victim near active high-voltage lines.

49. 4. Once the victim is free from the source of electricity, check the victim's
airway, breathing, and pulse. If either has stopped or seems dangerously
slow or shallow, start first aid.
5. If the victim has a burn, remove any clothing that comes off easily, and rinse
the burned area in cool running water until the pain subsides. Give first aid
for burns.

50. 6. If the victim is faint, pale, or shows other signs of shock, lay him or her
down, with the head slightly lower than the trunk of the body and the legs
elevated, and cover him or her with a warm blanket or a coat.
7. Stay with the victim until medical help arrives.

51. 8. Electrical injury is frequently associated with explosions or falls that can
cause additional traumatic injuries, including both obvious external
injuries and concealed internal injuries.
Avoid moving the victim's head or neck if a spinal injury is
suspected.
Administer appropriate first aid as needed for other wounds or fractures.

52. KEY CONCEPTS:
 Exposure to AC is three times more dangerous than DC of the same voltage
because of the potential for muscular tetany and prolonged contact.
 Nerves, muscles, and blood vessels have low resistance and are better electrical
conductors than bone, tendon, and fat.
 Electrical burns are usually most severe at the source and ground contact points. It is
not possible to predict the amount of underlying tissue damage based on the amount
of cutaneous involvement.
 Traditional rules of triage do not apply to lightning victims. Triage of lightning victims
should concentrate on those who appear to be in cardiorespiratory arrest.
 The most common presenting signs of lightning injury (keraunoparalysis, mottling,
confusion, amnesia) resolve with time. After spinal cord and intracranial processes
are excluded, observation is the mainstay of treatment.
Keraunoparalysis, also known as Charcot's paralysis, involves transient weakness affecting the lower limbs more commonly and automatically reverses in a matter of few
hours. The hypothesis behind this is the adrenergic gush and catecholamine release leading to temporary vasospasm of the spinal arteries.

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