Electrical Injury

Slide 1 · Electrical Injury

Pathogenesis, tissue effects and clinicopathologic interpretation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Distinguish thermal burns from electrical disruption of excitable tissues.

Explain why amperage, contact duration and current path govern injury.

Relate alternating current, wet contact and high-voltage exposure to major outcomes.

Apply burn morphology and systemic burn complications to extensive electrical injury.

Slide 3 · Electrical injury among physical-agent disorders

Injury by physical agents

Mechanical trauma

Thermal injury

Electrical injury

Ionizing radiation

Electrical injury has distinct electrical and heat-generating mechanisms.

Slide 4 · Two fundamental classes of electrical damage

Heat-mediated tissue damage

Disruption of nerve impulse conduction

Burns at contact sites

Ventricular fibrillation

Burns within internal organs

Failure of cardiac or respiratory centers

Extent influenced by current and time

Immediate functional catastrophe may precede visible burns

Heat-mediated tissue damage

Disruption of nerve impulse conduction

Slide 5 · Common exposure environments

Low-voltage contacts can occur in domestic and occupational environments.

High-voltage power lines are a separate hazardous exposure setting.

Lightning is a classic high-voltage source.

Exposure category alone does not specify the final physiologic injury.

Slide 6 · Low-voltage does not mean innocuous

Household / workplace voltage

High-voltage sources

Robbins cites typical supplies of 120 or 220 V.

Power lines and lightning are examples.

Wet contact can permit sufficient current for ventricular fibrillation.

Larger currents more often produce extensive burns.

Alternating current may prolong contact through tetany.

Medullary center paralysis is emphasized.

Household / workplace voltage

High-voltage sources

Slide 7 · Why voltage alone cannot describe risk

Applied voltage

Resistance at contact

Current through body

When resistance is low, ordinary supply voltage may permit a dangerous current.

Slide 8 · Three determinants of severity

Electrical exposure

Current strength (amperage)

Duration of flow

Path through the body

These jointly influence injury type and the severity and extent of burns.

Slide 9 · Amperage: The magnitude of flowing current

The strength of the electrical current is expressed as amperage.

Current strength is a determinant of the resulting tissue damage.

High-voltage sources can produce large current flows.

A source voltage is not equivalent to the amount of current passing through tissue.

Slide 10 · Duration compounds current-related injury

Contact persists

Current keeps flowing

Heat accumulates

Burn burden increases

Robbins explicitly links sustained flow to generated heat and burns.

Slide 11 · Current path determines exposed structures

The path within the body as a determinant of injury.

Entry and exit sites may be burned.

Internal organs along a current route may also sustain burns.

Clinical interpretation requires attention to affected tissues, not voltage alone.

Slide 12 · Wet skin changes the hazard

Wet contact

Lower resistance

More current may pass

Severe injury possible

This pathway is the specific household-contact example given.

Slide 13 · A 120- or 220-volt contact can be fatal

Robbins explicitly describes these voltages in homes and workplaces.

With low contact resistance, current may be sufficient for ventricular fibrillation.

Visible charring is not a prerequisite in this electrical mechanism.

Judging danger solely from nominal supply voltage is inadequate.

Slide 14 · A domestic contact: From exposure to fibrillation

Live supply

Low-resistance skin contact

Current traverses body

Electrical disturbance of heart

Conceptual sequence: The electrical endpoint includes ventricular fibrillation.

Slide 15 · Alternating current changes the duration of contact

Most domestic electrical supplies use alternating current (AC).

AC may trigger tetanic skeletal-muscle contraction.

Tetany can interfere with voluntary release of a grasped conductor.

The duration of electrical exposure may therefore increase.

Slide 16 · Alternating current: The grasp–tetany loop

Grasp live wire

Tetanic contraction

Persistent clutching

Prolonged current flow

The source describes irreversible clutching as likely, not inevitable, when a live wire or switch is grasped.

Slide 17 · Tetany is a mechanical amplifier of exposure

The muscle contraction is itself an electrical effect.

Loss of voluntary release extends the time of current passage.

Sustained current can increase heat generation.

The physiologic effect can therefore intensify the thermal injury.

Slide 18 · One exposure produces two coupled pathways

AC-induced tetany

Longer current exposure

More tissue heating

Parallel: Chest-wall tetany can impair ventilation; Prolonged exposure increases burn risk.

Slide 19 · Chest-wall muscle spasm can cause asphyxia

Alternating current can induce sustained spasm of respiratory muscles.

Impaired chest-wall movement can prevent effective breathing.

Fatal asphyxia as a possible result.

This mechanism differs from failure of central respiratory drive.

Slide 20 · Two mechanisms of respiratory failure

Chest-wall tetany

Respiratory center failure

Peripheral muscular mechanism

Central conduction / control mechanism

AC-associated spasm restricts respiratory movement.

Electrical injury disrupts neural impulse conduction.

Asphyxia can be the terminal event.

Center failure can be the terminal event.

Chest-wall tetany

Respiratory center failure

Slide 21 · Impulse-conduction disruption causes functional injury

Electrical injury need not act through thermal tissue destruction.

Interference with nerve impulse conduction is a separate mechanism.

Cardiac and respiratory centers may fail.

This accounts for life-threatening physiology even when burns are not the dominant feature.

Slide 22 · Pathway to ventricular fibrillation

Current exposure

Electrical conduction disturbed

Ventricular fibrillation

Loss of effective circulation

Final box is physiologic interpretation of ventricular fibrillation, not quoted Robbins language.

Slide 23 · Ventricular fibrillation is an electrical endpoint

Ventricular fibrillation among principal fatal events.

Low-resistance contact at household voltage may provide enough current.

Cardiac electrical failure must be distinguished from tissue heating.

The outcome depends on the particular current exposure, not simply its category.

Slide 24 · Immediate electrical events versus heat injury

Functional / conduction injury

Structural / thermal injury

Ventricular fibrillation

Entry and exit burns

Cardiac or respiratory center failure

Internal-organ burns

Chest-wall tetany and asphyxia

Extensive tissue destruction with sustained flow

Functional / conduction injury

Structural / thermal injury

Slide 25 · Sustained current generates thermal injury

Current persists

Heat generated in tissue

Localized and deeper burns

Potential systemic burn burden

Last step represents possible effects of extensive burns, covered in adjacent thermal-burn text.

Slide 26 · Electrical burns may involve entry and exit sites

Burns at the sites where current enters and exits.

The contact points represent only part of the possible injury distribution.

Sustained current increases the potential for heating along the route.

Do not infer a complete injury pattern from one skin contact mark.

Slide 27 · A current route may injure more than skin

Current through the body

Entry-site burn

Internal-organ burn

Exit-site burn

Schematic only: Actual paths vary; The textbook does not prescribe a fixed anatomical route.

Slide 28 · Internal-organ burns are an essential possibility

Electrical heating is not restricted to exposed epidermis.

Robbins explicitly describes internal-organ burns with sustained flow.

The current path becomes important when interpreting internal damage.

External burn appearance cannot establish the absence of deeper injury.

Slide 29 · Thermal and electrical injury: Overlap and distinction

Thermal-burn framework

Electrical-specific mechanisms

Describes depth and tissue necrosis.

Explains current path and contact conditions.

Explains edema, shock and infection in extensive burns.

Includes ventricular fibrillation and nerve conduction failure.

Useful when electrical injury causes major burns.

Cannot be replaced by burn grading alone.

Thermal-burn framework

Electrical-specific mechanisms

Slide 30 · High voltage often produces larger current flows

High-voltage exposures as producing similar types of damage.

Their large current flows make extensive burns more likely.

Paralysis of medullary centers is also more likely.

This is a tendency, not a claim that low-voltage events are harmless.

Slide 31 · High-voltage exposure: Dominant hazards

High-voltage electrical exposure

Large current flows

Extensive burns

Medullary-center paralysis

Extensive burns and medullary paralysis are parallel possible effects, not a sequential cascade.

Slide 32 · Medullary center paralysis

Robbins specifically associates high-voltage sources with medullary center paralysis.

The medulla contains vital autonomic control structures.

Loss of central control can produce catastrophic cardiorespiratory failure.

This is mechanistically different from a burn confined to contact skin.

Slide 33 · Electrical injury across exposure categories

Low-voltage exposure

High-voltage exposure

Household and workplace contact

Power lines and lightning

May cause ventricular fibrillation, especially with low skin resistance

More often causes extensive burns with large current flows

AC grasp tetany can prolong contact

Medullary paralysis more likely

Severe injury possible

Similar mechanisms, often greater tissue injury

Low-voltage exposure

High-voltage exposure

Slide 34 · Lightning as high-voltage exposure

Lightning is a classic example of high-voltage electrical injury.

Lightning within the same major electrical injury category.

Potential endpoints remain burns and electrical disruption of excitable tissues.

No lightning-specific lesion morphology is specified in the supplied excerpt.

Slide 35 · Link determinants to their pathologic effects

Electrical exposure features

Low resistance → current passage

Prolonged flow → heating

AC tetany → persistent contact

High current → extensive injury

These arrows express source-supported causal relationships, not quantitative risk estimates.

Slide 36 · Extensive electrical burns enter the burn-injury framework

Tissue heating from sustained current can produce genuine burns.

The adjacent Robbins thermal-burn section defines burn depth and complications.

Those general consequences provide context when electrical burns are extensive.

They do not replace assessment of the electrical mechanism itself.

Slide 37 · Burn depth is a tissue-anatomic classification

Epidermis

Dermis

Subcutaneous tissue

Compare the anatomic layer reached by each burn depth.

Superficial: Epidermis • Partial-thickness: Dermis • Full-thickness: Subcutaneous tissue

Slide 38 · Superficial burn: Injury confined to epidermis

Epidermis

Dermis

Subcutaneous tissue

Extent stops within the epidermis.

A superficial burn remains within the epidermis; Deeper layers are spared in this classification.

Slide 39 · Partial-thickness burn: Dermis involved

Epidermis

Dermis

Subcutaneous tissue

Dermal involvement makes this a partial-thickness injury.

Partial-thickness injury extends into the dermis, exceeding a superficial epidermal burn.

Slide 40 · Full-thickness burn: Into subcutaneous tissue

Epidermis

Dermis

Subcutaneous tissue

Subcutaneous extension establishes full thickness.

Full-thickness injury extends into subcutaneous tissue and may also involve underlying muscle.

Slide 41 · Burn depth and gross appearance

Partial-thickness burn

Full-thickness burn

Pink or mottled appearance

White or charred appearance

Blisters may be present

Dry surface

Painful

Painless if cutaneous nerve endings destroyed

Features vary with depth

Deep tissue loss and possible muscle involvement

Partial-thickness burn

Full-thickness burn

Slide 42 · Burned tissue shows coagulative necrosis

The adjacent thermal-burn morphology section describes coagulative necrosis in devitalized tissue.

Tissue architecture can persist transiently despite cell death.

Microscopy addresses structural heat damage—not ventricular fibrillation.

This framework applies to thermal components of electrical injury.

Slide 43 · At the burn edge: Necrosis and inflammation

Heat-damaged tissue interface

Devitalized tissue: Coagulative necrosis

Adjacent living tissue: Leukocytes

Marked inflammatory exudation

Necrosis and adjacent inflammation are related morphologic findings, not distinct sequential stages.

Slide 44 · Depth does not equal total clinical severity

Burn depth is one component of severity.

Robbins also identifies total body-surface involvement and associated internal injury.

Fluid/electrolyte support and infection prevention influence outcomes of extensive burns.

Electrical cardiopulmonary effects remain additional, distinct hazards.

Slide 45 · Extensive burns can precipitate shock

Large burn burden

Systemic inflammatory response

Vascular fluid leak

Intravascular depletion / shock

General thermal-burn physiology; Not a claim that every electrical burn produces shock.

Slide 46 · Vascular leak explains widespread edema

Severe burns may produce a systemic inflammatory response.

Fluid shifts to interstitial tissues through increasingly permeable vessels.

Generalized edema can be prominent; Pulmonary edema may occur.

This is a secondary injury mechanism in extensive burn patients.

Slide 47 · Burn wounds provide a niche for microorganisms

The burn surface contains proteinaceous exudate and tissue debris.

Compromised local blood supply can weaken effective host responses.

Colonization is common; Invasive infection can progress beyond the wound.

Infection is a later hazard distinct from the initial electric exposure.

Slide 48 · Burn infection can become a systemic problem

Compromised burn wound

Microbial infection

Bloodstream spread / toxins

Sepsis and organ failure

General thermal-burn section connects wound infection to pneumonia, shock, renal failure and ARDS.

Slide 49 · Three major complications of extensive burns

Complication

Mechanistic association

Shock

Inflammation and systemic fluid leakage

Sepsis

Wound microbial invasion and dissemination

Respiratory insufficiency

Pulmonary edema, infection or associated airway injury

Complication

Mechanistic association

Slide 50 · Major burns impose increased metabolic demands

A hypermetabolic state after extensive burns.

Heat loss and heightened energy requirements contribute to this response.

Systemic burn care must therefore look beyond the local skin wound.

This observation is not a specific biomarker of electrical injury.

Slide 51 · Recovery may leave hypertrophic scars

Hypertrophic scarring can follow major burn injuries.

Excess collagen deposition characterizes the scar.

Itching and scar symptoms can persist long after the exposure.

This is a healing consequence, not a defining electrical diagnostic sign.

Slide 52 · Immediate and later complications are not interchangeable

Immediate electrical hazard

Potential consequence of extensive burn

Ventricular fibrillation

Circulatory shock from vascular leak

Cardiac / respiratory center failure

Wound infection and sepsis

AC-associated chest-wall tetany

Hypertrophic scarring during recovery

Immediate electrical hazard

Potential consequence of extensive burn

Slide 53 · A clinicopathologic interpretation checklist

Identify the likely source: Domestic, workplace, power line or lightning.

Consider contact resistance, duration, current strength and trajectory.

Separate conduction-related outcomes from heat-mediated injury.

For extensive burns, use depth, extent and systemic complications as additional context.

Slide 54 · Case 1 — Wet-contact household exposure

Clinical scenario

An adult touches a household electrical fitting with wet hands. The source is a conventional domestic supply.

Why can this apparently low-voltage contact produce a fatal event?

A. Wet skin raises electrical resistance.

B. Lower skin resistance permits greater current passage.

C. Only high-voltage sources can affect the heart.

Slide 55 · Case 1 — Mechanistic resolution

B. Lower skin resistance permits dangerous current passage.

Robbins explicitly uses wet skin as a low-resistance example.

Domestic 120/220 V exposure can allow sufficient current for ventricular fibrillation.

Electrical lethality is not determined from voltage label alone.

Slide 56 · Case 2 — Grasping a live conductor

Clinical scenario

A worker grasps a live AC conductor. The hand remains tightly clenched around it despite an attempt to release.

Which sequence best accounts for increasing tissue injury?

A. Tetany → sustained contact → longer current flow → heating

B. Thermal necrosis → lower voltage → no further exposure

C. Medullary paralysis → reduced current through the limb

Slide 57 · Case 2 — Mechanistic resolution

A. Tetany extends electrical contact.

Alternating current can cause sustained muscle spasm.

Persistent clutching prolongs the period of current flow.

Longer exposure increases the opportunity for extensive burns.

Slide 58 · Case 3 — High-voltage exposure

Clinical scenario

A person contacts a high-voltage power source and develops extensive tissue injury together with abrupt cardiorespiratory dysfunction.

Which pattern is most consistent with Robbins?

A. High voltage produces burns but never affects neural centers.

B. High current flows favor extensive burns and medullary paralysis.

C. Current trajectory and exposure duration have no role.

Slide 59 · Case 3 — Mechanistic resolution

B. High current flow can injure tissue and vital centers.

High-voltage sources can generate large current flows.

Extensive burns are more likely.

Paralysis of medullary centers is an additional recognized hazard.

Slide 60 · Case 4 — Deep burn and systemic deterioration

Clinical scenario

A survivor of electrical exposure has sustained large, deep burns. Over the subsequent course, generalized edema and systemic infection become concerns.

Which mechanistic framework is appropriate?

A. Only electrical arrhythmias are relevant after exposure.

B. Major-burn inflammatory leak and infection pathways may apply.

C. Tissue depth provides no useful pathologic information.

Slide 61 · Case 4 — Mechanistic resolution

B. Extensive burns have important downstream pathophysiology.

Systemic inflammatory vascular leak can contribute to edema and shock.

Devitalized burn wounds are vulnerable to infection and sepsis.

Electrical conduction-related complications must still be considered independently.

Slide 62 · One integrated map of electrical injury

Electrical current traverses the body

Excitable tissue → fibrillation / central failure

AC tetany → prolonged contact / asphyxia

Heat generation → skin and internal burns

Extensive burns → shock / infection sequelae

All branches are potentially relevant; Their relative prominence depends on exposure.

Slide 63 · Essential clinicopathologic conclusions

Electrical injury operates through both heat generation and disruption of impulse conduction.

Amperage, exposure duration and current path are central determinants.

Wet contact and AC grasp tetany explain why household exposures can be lethal.

High-voltage currents favor extensive burns and medullary-center injury.

Extensive electrical burns can share the complications of major thermal burns.

Slide 64 · Reference and source boundary

Robbins, Cotran & Kumar: Pathologic Basis of Disease, 11th edition (2026).

Electrical Injury (principal section)

Injury by Physical Agents (parent context)

Thermal Burns (adjacent general burn pathology)