18. Burns – Part 4
Electrical Injury / Burns
- Nomenclature: Though the two terms electrical injury/burns are often used synonymously, they require to be distinguished from each other. For e.g. if a high tension wire leaks and earths, it produces two simultaneous effects. It increases the temperature of the air through which the current passes and this increase can be manifold and lead to a flash causing thermal burn of an individual (or an animal in the vicinity) and the heat might be so intense that the persons’ clothes might catch fire (or an animals’ coat may get charred). In addition the air when it is heated, expands and produces a wave phenomena which will throw the subject for some distance causing skeletal or visceral injuries. This kind of burn is in fact a thermal burn accompanied by trauma and the treatment is no different from what has been related in the first three preceding sections in these short notes. On the other hand, when an electrical current, while earthing (for example from a high tension wire or as in lightning,) has a person becoming a part of the earthing process, an electrical injury is caused. In the case of lightning the consequences are often fatal (called electrocution), but may not be so in the case of a high tension leak or in an industrial accident where the current is of a lesser magnitude or may be quickly switched off.
- Electrical injury: An electrical current passing through the body produces molecular changes in the cells incompatible with their life and the passage also generates heat leading to damage in the surrounding tissues. Alternating currents up to 220 volts which are commonly used in the domestic or commercial environment usually do not cause much damage. But higher currents classically have a point of entry and the current then travels along paths of least resistance, like nerves, vessels or muscles, but may be offered resistance by structures such as bones. When the bone encounters the electric current, it may undergo some liquefaction and if the current is causing severe muscular contractions and leads to a fall the bone can also get fractured. Having travelled, the electric current usually has a wound of exit and the damage that is caused is not dependent upon where the current enters but what happens to it subsequently. If the current can diffuse in several directions as in the torso, the damage might be less because it dissipates itself over a broader area. But a linear progression in an arm or a leg creates greater damage because the pathological effect remains concentrated in the limb. Classically in the upper arm the current having passed up to the shoulder will exit from the back and the wound of entry might be small but the wound of exit might be patchy or diffuse. In cases where the back is not in contact with another object and the current is not earthed, it diffuses in the area producing a zone of burns till the current expends its energy. In case of a high voltage alternating current rescuers have to be careful not to touch the stricken individual till the current is switched off lest the rescuer also gets affected by the current. Where direct currents are in use the individual who suffers the electrical injury usually gets thrown off and this danger does not exist.
- Resuscitation at the site must first concentrate on the cardio-respiratory system. Damage to the respiratory muscles as well as central paralysis of these muscles can affect breathing and the patient might need an adequate airway if necessary with an intratracheal tube and artificial respiration with bellows. The passage of electrical current also produces a variety of arrhythmias including cardiac asystole which will require immediate injection of adrenaline and ironically cardioversion by an electrical current with the help of a defibrillator. The other arrhythmias are treated with appropriate drugs to revert the heart to normal sinus rhythm. Here too traumatic injuries need to be assessed and will require splintage and other first aid.
- Electrical injuries with high voltage particularly to extremities result in an iceberg phenomena where the wound of entry might be small but gross necrosis of deeper tissues supervenes in a matter of hours. The skin might not reflect the deeper necrosis immediately but will discolour over a period of time. The necrosis of tissues either occurs directly due to coagulation or due to thrombosis of major blood vessels. In a double jeopardy, necrosed muscle mass leads to myohaemoglobinuria causing blockage of renal tubules. In addition the body suffers due to sequestration of considerable blood volume caused by the blockage of vessels of the limb. This leads to sudden hypovolemia and shock which is disproportionate to the size of the injury (which is often called a burn). Both these conditions need to be treated with large infusions of intravenous fluids, up to four to six ccs per kilogram per injured area in the first 8 hours. Monitoring of the urine output and the central venous pressure will allow the clinician to administer diuretics whenever required. Myohaemoglobinuria usually settles within 48 hours after which the infusions can be reduced in quantity. If renal function suffers over longer periods, either indirectly because of myohaemoglobinuria or direct renal visceral injury, dialysis might have to be considered.
- Because the injury is deep seated the oedema can cause considerable pressure in the sub-fascial plane leading to a compartment syndrome and this increases the damage to the deeper structures which had been partly spared at the time of the initial injury. In the case of nerves where blood supply is already compromised and axonal damage has occurred, the pressure can lead to further vascular compromise leading to infarcts in long segments of nerves. Fasciotomy needs to be undertaken to counteract this situation which is diagnosed by the increasing pallor in the fingers with swelling and pain. The fasciotomy should be radical throughout the affected limb till the tissue underneath bulges through the incisions and might have to be done in more than one area, for example on both the extensor and flexor surfaces. The nature of the bulging tissue should then be examined and its viability determined. If the tissue is not viable and is encircling the limb, particularly in the distal half, and if the injury though limited to a limb is causing toxicity/infection/septicaemia, an amputation might be considered and will many times save lives. Charred fingers or toes or the fore foot which are obviously dead are also removed. Guillotine amputations are preferred because proximal flaps which may appear normal might not be viable and a formal refashioning is postponed for several days.
- Though electrical injury in a domestic or commercial environment rarely causes great damage the wounds of entry might be deeply necrotic if contact with an alternating current is of a longer duration. Muscle contraction caused by the electric current can prevent the patient letting go of an electrified object. Toes or the plantar surface of the foot can also be affected. The line of treatment can be somewhat expectant because the injuries do not have general consequences and the wound will show its full necrotic dimension over a period of time. Debridement should be done in stages till the full extent of the injury becomes obvious and the surrounding areas show adequate vascularity. Distant flaps are preferred, free flaps are tricky because the recipient vessels might have to be accessed at some distance but in instances such as electrical injuries to the scalp and the calvarium, free flaps remain the choice and access to relatively distant donor vessels is readily achieved.
- High voltage major electrical injuries will test the skills and planning of a reconstructive surgeon because the destruction involves not only the skin and subcutaneous tissue but also muscle mass and tendons and most importantly nerves. Damage or destruction of nerves may be over a long length, for example a loss of median and ulnar nerves over several inches will imply that the hand has not only lost all of its ventral sensations but has also lost the power of the intrinsic muscles as well as of any residual surviving muscle mass. Under these circumstances, whether reconstruction proceed with flaps, nerve grafts, tendon transfers etc. will be a matter of judgment. In such severe situations in spite of the best of efforts, the hand may look like a hand but is useless. The patient then needs to be a part of the decision making process because the science of dynamic prostheses has progressed considerably in the last two decades and an amputation may not only be in order but a prosthesis will be far more useful to the patient.
- In less grievous injuries, if muscle destruction is restricted to one compartment and a gap in the corresponding nerve or nerves is of a manageable proportion (in that they can be mobilized and sutured or can be bridged by a short nerve graft), reconstruction needs to be given a chance. The idea is to share whatever muscle power is left by way of tendon transfers to allow three basic movements; dorsiflexion of the wrist, a mass grasp of the fingers (if not individually) and an opposable thumb.
- Because nerves are extremely sensitive to the passage of an electrical current, some of the sequelae of such a passage of even low voltage might appear late by way of slow degeneration and demyelination. Injury to vessels supplying the spine and the spinal cord might manifest late. An unusual but late complication of an electrical injury is cataract which might occur in one or more commonly in both eyes. Retinal damage is uncommon unless there is a direct thermal burn of the globe. Patients with any significant electrical injury or burn must therefore be followed up for a long duration.
Dr. Sunil Keswani from Mumbai adds: In addition to cataracts, patients can suffer rupture of tympanic membrane, pneumothorax, intestinal perforation and gangrene of large lengths of intestine and infarcts in solid organs for e.g. brain, liver, kidney, spleen etc. The clinician must be aware of these conditions in order to recognize them and take suitable steps including references to appropriate specialists.