Trauma
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Question 179 of 300
A 31 year old trainee electrician presents to ED following an electric shock to his left hand while working on a household outlet. He describes a sudden onset pain but he withdrew his hand immediately and did not lose consciousness. He is usually fit and well. On examination, there are no visible marks to his left hand and his observations are normal. You are considering discharge, which of the following investigations should be completed before discharge?
Answer:
This patient has likely sustained a low-voltage electrical injury. Clear guidelines do not exist regarding which studies to obtain following electrical injury, and to a large degree, this must be determined clinically on a case-by-case basis. All patients, even if asymptomatic, should have an electrocardiogram (ECG) performed. A patient with any persistent symptoms or presence of cutaneous burns (including contact point wounds) should also have a urinalysis obtained to evaluate for myoglobinuria. For patients with a high-voltage or lightning exposure, large body surface burns, or concern for deep tissue injury; or those for whom observation or admission to the hospital is anticipated, the following studies are all suggested:- Basic serum electrolytes (including calcium)
- Creatine kinase (CK)
- Serum troponin
- Complete blood count
- Kidney function tests (creatinine and blood urea nitrogen)
Lightning Strike and Electrical Injuries
Environmental Emergencies / Trauma
Last Updated: 4th August 2021
Electrical injuries
Electrical injury is a relatively infrequent but potentially devastating multi-system injury with high morbidity and mortality. Most electrical injuries in adults occur in the workplace and are associated generally with a high voltage, whereas children are at risk primarily at home, where the voltage is lower (220V in Europe).
Factors influencing the severity of electrical injury include:
- Whether the current is alternating (AC) or direct (DC)
- Voltage
- Magnitude of energy delivered
- Resistance to current flow
- Pathway of current through the patient
- Area of contact
- Duration of contact
Pathophysiology:
- Contact with AC may cause tetanic contraction of skeletal muscle which may prevent physical release from the source of electricity
- Myocardial or respiratory failure may cause immediate death:
- Respiratory arrest may be caused by central respiratory depression or paralysis of the respiratory muscles
- Current may precipitate VF if it traverses the myocardium during the vulnerable period (analogous to an R-on-T phenomenon)
- Electrical current may also cause myocardial ischaemia because of coronary artery spasm
- Asystole may be primary, or secondary to asphyxia following respiratory arrest
- Current pathways
- Electric current follows the path of least resistance; conductive neurovascular bundles within limbs are particularly prone to damage
- Current that traverses the myocardium is more likely to be fatal
- A transthoracic (hand-to-hand) pathway is more likely to be fatal than a vertical (hand-to-foot) or straddle (foot-to-foot) pathway
- There may be extensive tissue destruction along the current pathway
Lightning strikes
- Electrocution from lightning strikes is rare but causes about 1000 deaths worldwide each year.
- Lightning strikes deliver as much as 300 kV over a few milliseconds
- Most of the current passes over the surface of the body in a process calls external flashover
- Both industrial shocks and lightning strikes cause deep burns at the point of contact; in industry, the points of contact are usually on the upper limbs, hands and wrists whereas with lightning they are mostly on the head, neck and shoulders
- Injury may also occur indirectly through ground current or current 'splashing' from a tree or other object that is struck by lightning
- Explosive force generated by a lightning strike may cause blunt trauma
- The pattern and severity of injury from a lightning strike varies considerably; death is caused by cardiac or respiratory arrest
- In those who survive the initial shock, extensive catecholamine release or autonomic stimulation may occur, causing hypertension, tachycardia, nonspecific ECG changes (including prolongation of the QT interval and transient T wave inversion) and myocardial necrosis; creatine kinase may be released from myocardial and skeletal muscle
- Lightning also causes various central and peripheral neurological problems
Treatment of lightning strike and electrical injuries
- Ensure any power source is switched off and do not approach the victim until it is safe
- High voltage electricity can arc and conduct through the ground for up to a few metres around the victim
- It is safe to approach and handle casualties after lightning strike although it would be wise to move to a safer environment
- Follow standard resuscitation guidelines
- Airway management can be difficult if there are electrical burns around the face and neck; intubate the trachea early in these cases and soft tissue oedema can cause subsequent airway obstruction; consider cervical spine immobilisation but this should not delay airway management
- Muscular paralysis, especially after high voltage, may persist for several hours; ventilatory support is required during this period
- VF is the commonest initial arrhythmia after high voltage AC shock; treat with prompt attempted defibrillation
- Asystole is more common after DC shock; use standard guidelines
- Remove smouldering clothing and shoes to prevent further thermal injury
- Give IV fluids if there is significant tissue destruction; maintain a good urine output to increase excretion of myoglobin, potassium and other products of tissue damage
- Consider early surgical intervention in patients with severe thermal injuries
- Conduct a thorough secondary survey to exclude injuries cause by tetanic muscular contraction or from the person being thrown by the force of the shock
- Electrocution can cause severe, deep soft tissue injury with relatively minor skin wounds because current tends to follow neurovascular bundles; look carefully for features of compartment syndrome, which will necessitate fasciotomy
- All patients who survive an electrical injury should be monitored in hospital if they have a history of cardiorespiratory problems or have had loss of consciousness, cardiac arrest, ECG abnormalities or soft tissue damage or burns
- Severe burns (thermal or electrical), myocardial necrosis, the extent of central nervous system injury, and secondary multiple system organ failure, determine the morbidity and long-term prognosis
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
