Patient Monitoring

Many individuals attend the emergency department following an electrical shock from a low voltage source. Such patients have often sustained little or no thermal injury. However, they or their employer are concerned about the risk of cardiac dysrhythmia. Debate exists about the need for ECG monitoring of such patients.

The risk of malignant dysrhythmias such as VF/VT is greatest at the time of injury. The incidence of late dysrhythmia is not known but is thought to be very low. A six year review of fatal electrocutions in Delhi found that 150 of the 153 fatalities died at the scene. A further two died of septicaemia and one died of a dysrhythmia that was present on admission.

Dysrhythmia and low voltage injuries

By the time of presentation to the emergency department the risk of a malignant dysrhythmia is low. An Australian study of 212 consecutive presentations of low voltage electrical injury demonstrated transient conduction abnormalities in only 4% of patients following 6 hours of ECG monitoring.

The authors went on to develop a protocol whereby patients who sustained a low voltage injury and had a normal baseline ECG did not undergo further monitoring. No ill effects resulting from this policy were observed.

Dysrhythmia and high voltage injuries

Traditionally, patients who sustain high voltage injuries (>1000 volts), lose consciousness, have a transthoracic current pathway or an abnormal baseline ECG are thought to be at higher risk of dysrhythmia and consequently undergo cardiac monitoring.

The necessity and duration of cardiac monitoring in this so-called high risk group is subject to debate. A Canadian study performed 24 hours of continuous cardiac monitoring on 134 high risk patients. No lethal dysrhythmias were observed during the 24 hour monitoring period.

Troponin

The role of troponin or CK MB measurement in electrical injury is unclear. Baseline and 12 hour troponin measurement may be carried out if high risk features are present. The clinical significance of elevated troponin is uncertain.

Monitoring the foetus

Monitoring of the foetus by cardiotochography (CTG) is advisable for pregnant women over 22 weeks gestation. An obstetric consultation should also be obtained.

Learning bite

ECG monitoring is not routinely required for ‘low risk’ electrical shocks.