Endgames Picture Quiz

An unusual burn

BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f2856 (Published 15 May 2013) Cite this as: BMJ 2013;346:f2856
  1. C J Mitchell, core surgical trainee year 21,
  2. Z Ahmad, core surgical trainee year 21,
  3. M S Khan, consultant1
  1. 1Department of Burns, Plastic and Reconstructive Surgery, Salisbury District Hospital, Salisbury SP2 8BJ, UK
  1. Correspondence to: C J Mitchell, Department of Orthopaedics, Dorset County Hospital, Dorchester DT1 2JY, UK cjmitchell{at}doctors.org.uk

A 56 year old man presented with an injury to the radial aspect of his right wrist (figure). While undertaking mechanical repairs to his car the previous day his metal wrist watch had made contact with part of the electrical system. He felt immediate pain but did not implement any first aid measures or seek medical attention at the time of injury. Subsequent skin changes and discomfort at the periphery of the lesion prompted him to visit his general practitioner, who suspected an electrical burn and referred him to the local burns unit for assessment and management. He had no medical history of note. On examination the centre of the lesion had a leathery appearance, did not blanch on pressure, and was insensate.

Questions

  • 1 From the photograph, estimate the total body surface area and depth of this burn.

  • 2 How would you manage a patient presenting with an electrical burn?

  • 3 What complications can occur with an electrical burn?

Answers

1 From the photograph, estimate the total body surface area and depth of this burn

Short answer

The photograph shows a full thickness burn to the volar aspect of the wrist, total body surface area about 0.25%.

Long answer

Burn depth can be assessed using the four tests summarised in the table.1

Assessing burn depth1

View this table:

Several methods can be used to assess burn surface area as a percentage of total body surface area (TBSA), with the Lund and Browder burn charts being perhaps the most widely used. These allocate a percentage of TBSA to each part of the body and incorporate a conversion factor to compensate for areas affected by growth in children and adolescents.2 Alternatively, the surface of the patient’s palm (excluding wrist but including fingers) is roughly equivalent to 1% of TBSA in any age group. A tracing of the palm can be used to rapidly assess burn surface area for smaller burns or those of an irregular pattern.3 Areas of erythema alone or soot covered unharmed skin are not included in estimates of burn surface area.

2 How would you manage a patient presenting with an electrical burn?

Short answer

Initial management is to assess and resuscitate using advanced trauma life support and emergency management of severe burns principles, remove the burning source, and cool with tepid running water. Further assessment of burns includes full history (to identify the source and mechanism), careful examination, appropriate investigations, discussion with local burns unit, and application of non-adherent dressing.1

Long answer

When presented with any acute burn the first task is to remove the burning source if still present. In the context of an electrical burn injury, the source must first be made safe to avoid injury to any intervening healthcare workers. High voltage electrical burns may be associated with additional injuries. Structured assessment using an advanced trauma life support and emergency management of severe burns protocol is essential to ensure that potentially life threatening injury or compromise of physiological systems is identified and stabilised in order of clinical priority.

Intravenous fluid resuscitation is needed for burns covering greater than 15% of TBSA in adults or 10% in children. In the United Kingdom, this has traditionally been calculated using the Parkland formula.4 In the first 24 hours adult patients receive 4 mL/kg/%TBSA of isotonic crystalloid, half of which is given in the first eight hours after the burn is sustained, and the remainder over the next 16 hours. Alternative regimens include the modified Brook formula of 2 ml/kg/%TBSA, and the “rule of 10s,” whereby fluid rate (mL/h) is calculated as %TBSA×10 for patients weighing 40-80 kg, with an additional 100 mL/h for every 10 kg over 80 kg.5 6 Fluid infusion rates should be titrated to maintain a urine output of 0.5-1 mL/kg/h for uncomplicated thermal injury in adults. A urine output of 1 mL/kg/h should be the target for patients with electrical injury, acute kidney injury, or rhabdomyolysis. In all cases this is most accurately measured with the use of a urinary catheter.7

The rule of 10s is not appropriate for children, and a modified Brook formula should be used instead.5 Maintenance fluids should be given in addition to resuscitation fluids, aiming for a urine output of 1-2 mL/kg/h.

Initial cooling of the burn may be afforded by irrigation with clean tepid, rather than cold, water to avoid reactive vasoconstriction and further ischaemic insult to the burnt tissue. After copious irrigation, the burn should be covered with a non-adherent dressing to prevent secondary infection of the compromised epithelium.1

A careful history should be taken from the patient and any witnesses to establish the nature of the electrical burn sustained. It is important to identify the voltage of the electrical current involved, either high voltage (≥1000 V) or low voltage (<1000 V). One form of electrical burn known as a flash burn is sustained when electricity arcs between its source and another conducting object. Although this generates high temperatures and causes burns, it is often the case that no electricity passes through the patient’s body.8

Passage of electricity through the body generates heat, which causes thermal damage to adjacent tissue. The degree of damage is proportionate to the resistance of the tissue and increases from nerve and vessel to muscle, skin, tendon, fat, and finally bone.9 To establish the location of potential areas of damage, a full examination of the patient is needed to identify contact point wounds.

3 What complications can occur with an electrical burn?

Short answer

In addition to cutaneous injury at the contact points, complications specific to electrical burns include cardiac arrhythmias, rhabdomyolysis from thermal damage to muscle, acute renal failure from myoglobinuria, hepatic dysfunction, acute fracture, compartment syndrome, and cataracts.10

Long answer

Injury to structures lying between contact points should be carefully investigated and excluded. Damage to muscle occurs in both low and high voltage burns but is more severe with high voltage injuries. All burns affecting limbs should be strictly elevated and closely monitored for signs of compartment syndrome. Clinical examination results consistent with compartment syndrome mandate immediate decompressive fasciotomy and debridement of non-viable tissue. In extreme cases amputation may be required.8 9 10

A secondary consequence of rhabdomyolysis is the release of large quantities of myoglobin, which can cause acute renal failure through acute tubular necrosis. Manifesting as visible pigmentation of the urine, this can be confirmed by urinalysis and is treated by aggressive fluid resuscitation to maintain a urine output of 1 mL/kg/h. Mechanisms of the development of acute kidney injury in rhabdomyolysis are not fully understood but include vasoconstriction, tubule obstruction by myoglobin casts, and cytotoxic effects of myoglobin on tubular epithelial cells. Adjunctive treatment with mannitol (as an osmotic diuretic), sodium bicarbonate (to alkalinise urine), and loop diuretics have all been described. Creatine kinase is also released during rhabdomyolysis and can provide a useful laboratory indicator of muscle damage.11

Finally, transmission of an electrical current (particularly alternating current) through the body can interfere with propagation of the cardiac action potential, potentially precipitating cardiac arrhythmias. An initial electrocardiogram is mandatory in all patients presenting with electrical burn injuries—if this is normal and the patient did not lose consciousness, evidence suggests that further cardiac monitoring is not needed. Conversely, those presenting with either an abnormal electrocardiograph or a history of loss of consciousness require a 24 hour period of cardiac monitoring and further 12 lead electrocardiographic assessment.8 9 12

Patient outcome

The patient attended our outpatient burns dressing clinic for regular dressing changes and made a full recovery from his electrical burn with no complications.

Notes

Cite this as: BMJ 2013;346:f2856

Footnotes

  • Competing interests: We have read and understood the BMJ Group policy on declaration of interests and declare the following interests: None.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

  • Patient consent obtained.

References