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Three Part Question

Are [health care personnel who are performing chest compression] during [external defibrillation] [exposed to stray electrical current]?

Clinical Scenario

A 66 year-old man suffers a witnessed out of hospital cardiac arrest. He is given immediate bystander cardiopulmonary resuscitation (CPR) until a paramedic ambulance crew arrives. The first recorded cardiac rhythm shows ventricular fibrillation. The ambulance crew continues CPR in accordance with current Advanced Life Support guidelines. Initial resuscitation attempts including three defibrillation attempts fail. Each time the patient is defibrillated, there is a necessary interruption in chest compressions. As medical director, you question the safety of a rescuer remaining in contact with a patient being shocked with modern defibrillation equipment.

Search Strategy

Medline 1996-06/15 using OVID interface, Cochrane Library (2015), and Embase

[(resuscitation/adverse effects OR electric countershock/adverse effects OR defibrillators/adverse effects)] AND [(hands on) OR (chest compression) OR (heart massage.mp)]. Limit to humans and English language.

Search Outcome

176 papers were identified; two were relevant to the clinical question

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Lloyd MS, et al. May 2008 USA	Measured leakage voltage and current through health care workers administering hands on CPR while defibrillating patients using biphasic defibrillators. Created a "rescuer patient" circuit by attaching electrodes to patient and rescuer.	RCT	Measured 43 hands-on shock with range of 100j to 360j	All health care workers using polyethylene gloves did not feel any shock.	Measurements did not address bare skin-to-skin contact between the rescuers' hand and the anterior chest of the patient. Contact pressure on the anterior chest of the patient was estimated and may have varied between measurements, possible affecting the amount of the leakage energy coupled to the rescuer. Poorly adherent defibrillating electrodes with resultant arcing could put a hands-on rescuer at risk; they also did not examine leakage current using rigid handheld defibrillation paddles. About 10% of the shocks were above the allowable 0.5mA.
			Measured leakage voltage between rescuer and patient	Peak potential differences between the rescuer's wrist and thigh ranged from 0.28 to 14 V. The average leakage current flowing through the rescuer's body for each phase of the shock wavefrom was 282 +/- 140A. This was below several recommended safety standards for leakage current.
Lemkin DL, et al. 2014 USA	Six cadavers set up with device to measure voltage through different parts of body and using a formula rescuer-received dose (RRD) calculated received shock a rescuer would receive from patient during hands-on defirbrlation	RCT	Cadaver estimated RRD	Defribrillation resulted in rescuer exposure voltages ranging from 827V to 200V, depending on cadaver and anatomic location. The rescuer received dose under the test scenarios ranged from 1 to 8 J, which is in excess of accepted energy exposure levels.	Used cadavers vs live patients

Comment(s)

During resuscitation from cardiac arrest due to ventricular fibrillation or ventricular tachycardia, “all-clear” or “hands-off” periods are mandated to avoid potential electrocution of rescuers. These hands-off periods interfere with resuscitation, especially given that current strategies emphasize the importance of avoiding any interruption of chest compressions. There have been substantial changes to external defibrillation technology since the inception of resuscitation protocols with hands-off periods.1 Adhesive electrodes result in more consistent electrode-skin coupling and biphasic shocks and real-time impedance monitoring have reduced peak voltages. Most groups have now concluded that defibrillation should occur during and not after chest compressions, but concerns about safety have precluded implementation of such a strategy.

Clinical Bottom Line

The amount of harm that stray electrical energy could cause a human depends mostly on the current but also on voltage, oscillation frequency, and duration of exposure. Safety standards for the latter variables are not well defined. Since publication of the article by Lloyd and colleagues, subsequent laboratory studies have measured the electrical resistance across nitrile gloves. These gloves do not provide adequate electrical insulation for the rescuer to safely undertake 'hands-on' defibrillation and when exposed to the physical forces of external chest compression, even greater resistive degradation occurs. Hands-on defibrillation should be considered potentially dangerous until equipment and techniques that will protect rescuers are developed.

References

1. Lloyd MS, Heeke B, Walter PF, Langberg JJ Hands-on defibrillation: an analysis of electrical current flow through rescuers in direct contact with patients during biphasic external defibrillation Circulation 2008 May 13;117(19):2510-4
2. Lemkin DL, Witting MD, Allison MG, Farzad A, Bond MC, Lemkin MA Electrical exposure risk associated with hands-on defibrillation Resuscitation 2014 Oct;85(10):1330-6