Dangersof Defibrillation: Injuries to Emergency Personnel During Patient Resuscitation WARREN GIBBS MD, PHD,* MICKEY EISENBERG MD, PHD,t SUSAN K. DAMON, BA*t There have been no studies of the nature of defibrillatory shocks or risks to persons, provlding them other than one individual case report and a number of incldental accounts. In this study, the severity and nature of injuries to prehospital emergency personnel in King County, Washington are reported. In addition, the types of injuries occurring to defibrillator operators throughout the United States, as voluntarily reported to the Food and Drug Administration (FDA), are described. In King County, prehospital emergency personnel reported eight accidental shocks. One indivldual was admitted to the hospital for 3 days and required lidocaine for premature ventricular contractions. Most injuries were the result of au cidental contact with the patient rather than equipment failure, but the most serious case was caused by equipment failure. There were 13 injuries reported to the FDA over a N-year period, and most injuries involved a mild shock or bum. Three patients were admitted to the hospital for observation. Two cases involved equipment failure. The rate of injury for paramedics was 1 per 1,700 defibrillatory shocks, and the rate of injury for emergency medlcal technician-defibrillator personnel was 1 per 1,000 defibrillatory shocks. These rates probably overestimate the real risk. Emphasis on safety and incorporation of safety procedures into resuscitation protocols can make the rate of injury even tower. (Am J Emerg Med lggO$:lOl-104. 0 1990 by W.B. Saunders Company.)
Since the advent of lightweight defibrillators and their use in the field by paramedics, a countless number of lives has been saved. At the inception of paramedic programs, defibrillator use by nonmedical personnel was met with considerable criticism. Their use by nonmedical personnel was considered to be practicing medicine without a license. It was thought that risks to the patient and to emergency personnel were too great, and that defibrillator use must be under tight supervision.’ Defibrillatory shocks, while often lifesaving, also have potential for harm. For a patient in ventricular fibrillation, the possibility of skin burns and myocardial muscle damage is clearly worth the risk given the grave clinical condition. However, for the individual administering the shock the possibility of harm must be low, and the type of injury must be acceptably minor. Injuries to patients receiving defibrillatory shocks have been described, but other than anecdotal re-
From the ‘Center for Evaluation of Emergency Medical Services, King County Health Department, Emergency Medical Services Division, and the tDepartment of Medicine, University of Washington, Seattle. Manuscript received March 9, 1989; revision accepted May 12, i 989. Address reprint requests to Dr Eisenberg: Center for the Evaluation of Emergency Medical Services, 110 Prefontaine PI, S, Suite 500, Seattle, WA 98104. Key Words: Electric countershock, defibrillation, adverse effects, emergency medical services, cardiac arrest, cardiopulmonary resuscitation. 0 1990 by W.B. Saunders Company. 0735-6757/90/0802-0004$5.00/O
ports, there have been no published studies of injuries to individuals administering defibrillatory shocks.‘*’ The use of defibrillators has increased substantially, and with automatic defibrillators the number of defibrillator shocks performed will increase even more. Therefore, we need to assess frequency, type, and rate of injuries to individuals providing defibrillatory shocks to patients in cardiac arrest. We believe that this is a safe procedure that can be performed satisfactorily by nonmedical personnel. METHODS Information about injuries to operators of defibrillators was obtained from two sources. The first source of information was a survey conducted among prehospital emergency personnel in King County, WA. The King County emergency medical service (EMS) system uses a tiered response system composed of emergency medical technicians (EMTs) and paramedics. The first emergency vehicle to arrive is staffed with EMTs or EMTs trained in defibrillation (EMTDs), and the second vehicle is staffed with paramedics. There are 500 EMT-Ds, who are authorized to provide defibrillatory shocks for ventricular fibrillation, and 63 paramedics, who provide advanced cardiac life support, employed in the King County EMS system. The EMT-Ds and the paramedics used manual defibrillators at the time of this survey. In May 1988 a questionnaire was mailed to every paramedic working in the King County EMS system. The questionnaire asked for a description of any episode in which the paramedic or a bystander received an accidental shock or injury from a defibrillatory shock and asked for the number of years employed full-time as a paramedic. The King County EMS system has been in operation since 1975, but it has been operating fully only since 1979. In general, our study of the King County paramedics has focused on the last 10 years. Each questionnaire for which an incident was reported was followed up with a phone interview to obtain more information. Only those incidents in which the paramedic was personally involved were used. In addition to injuries to paramedics, accounts of all reported detibrillatorassociated injuries from the last 7 years to EMT-Ds were obtained from the medical director of the King County EMT defibrillation program (Richard 0. Cummins, personal communication, January, 1989). The total number of defibrillatory shocks delivered to patients in King County was determined from a cardiac arrest surveillance system. This system has collected information, including the number of defibrillatory shocks delivered during a resuscitation, on every prehospital cardiac arrest receiving emergency care since the inception of the paramedic 101
AMERICAN JOURNAL OF EMERGENCY MEDICINE m Volume 8, Number 2 n March 1990
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program in 1975.* An injury rate was calculated, based on the total shocks delivered and the number of injuries. Reports from throughout the United States to the Product Monitoring Branch of the Food and Drug Administration (FDA) were also used. Injuries either to the equipment operator or to the patient or device failures have been required to be reported to the Product Monitoring Branch since 1984. These records were obtained through the Freedom of Information Act and were reviewed for the period from January 1984 through September 1987. RESULTS Questionnaires were completed by all 63 paramedics. They reported five episodes of injuries to themselves and one episode of injury to an EMT. In addition, there were two episodes of accidental injury to EMT-Ds. The episodes involving the paramedics and EMT-Ds are summarized in Table 1. The most serious injury (case 1) was the result of a cracked defibrillator paddle; the paramedic received the shock at the time of defibrillation and recalls “blacking out” for 1 to 2 minutes. He was hospitalized for 3 days and required lidocaine for premature ventricular contractions. The crack was later found by the manufacturers’ technician and was not detectable by visual inspection. All the other injuries (cases 2 through 8) were results of accidental contact with the patient or stretcher. None of the accidental shocks resulted in permanent injury. In King County, paramedics have treated an average of 310 patients per year over the past 10 years with deflbrillatory shocks, including patients who are in ventricular fibrillation upon arrival of emergency personnel and patients in whom ventricular fibrillation occurs during resuscitation (usually in response to pharmacological intervention). When
defibrillatory shocks are required, paramedics administer an average of 3.2 shocks per patient. Thus, paramedics provide approximately 1,000 defibrillatory shocks per year. The six accidental injuries (five paramedics and one EMT) reported by the paramedics over a IO-year period averages 0.6 injuries per year, or approximately 1 injury per 1,700 shocks. For EMT-Ds two accidental injuries occurred during the 7 years of the EMT-D program. EMT-Ds provide deflbrillatory shocks for approximately 150 patients per year (average of the past 7 years) and administer an average of two shocks per patient. Thus, EMT-Ds experienced approximately 1 injury per 1,000 patient shocks. Both of these injury frequencies are probably overestimations because both EMT-Ds and paramedics use “live” defibrillations during training (Richard 0. Cummins, personal communication, January, 1989). Information obtained from the Product Monitoring Branch of the FDA reported 13 episodes of injuries to operators of defibrillators. Injuries occurred to paramedics, EMTs, nurses, and biomedical technicians. The episodes are summarized in Table 2. Ten of the injuries occurred during resuscitations. The other three were associated with testing and training. In two instances (cases 8 and 9), equipment failure led to a shock of the operator. Arcing of the electric shock from the paddle to an electrode on the patient’s chest occurred in three cases (cases 1,6, and 8). Three individuals were hospitalized for observation. There were no reports of persistent morbidity. DISCUSSION There has been only one case report and a few anecdotal accounts of injuries to operators of detibrillators.‘~3 The most dramatic case involved a physician, participating in an advanced cardiac life support course, who placed the de-
TABLE1. Injuries Associated With Defibrillation Occurring to Paramedics and EMT-Ds in King County, WA, 1979-1988 Case
Personnel
Setting
Circumstances
Nature of Injury
1
Paramedic
Resuscitation
Crack in defibrillator paddle; shock to paramedic occurred during defibrillation
Admitted to hospital for 3 d; frequent premature ventricular contractions requiring lidocaine for 24 h; localized muscle spasms in paramedic’s chest and arms continued for several weeks
2
Paramedic
Resuscitation
Paramedic’s arm was touching side rail of stretcher
Tingling in right arm for 30 min
3
Paramedic
Resuscitation
Hand contact with gel during defibrillation
Mild soreness to right arm
4
Paramedic
Resuscitation
Paramedic was checking femoral pulse; EMT-D defibrillated
Shock knocked paramedic away from patient
5
Paramedic
Resuscitation
Paramedic’s leg was touching patient when shock was delivered
Mild shock to leg
6
EMT
Resuscitation
EMT was holding bag mask at time of defibrillatory shock
Mild shock to tips of fingers
7
EMT-D
Resuscitation
EMT-D’s thumb was in contact with patient’s breast at time of defibrillatory shock
Shock to hand; lethargy for several minutes
8
EMT-D
Resuscitation
EMT-D’s leg was touching stretcher at time of defibrillatory shock
Shock to leg
GIBBS, EISENBERG, AND DAMON H DANGERS OF DEFIBRILLATION
TABLE2. Injuries Associated With Defibrillation January 1984 Through September 1987 Case
Personnel
103
Occurring to Emergency Personnel Reported to the Food and Drug Administration,
Circumstances
Setting
Nature of Injury
1
Paramedic
Resuscitation
Arch from paddle to electrode on patient
Burn to hand; patient also received burn
2
EMT
Resuscitation
Accidental discharge during charging
Mild shock to three EMTs
3
Nurse
Resuscitation
Nurse received shock while defibrillating patient
Tingling sensation to hands, legs, and back
4
Nurse
Resuscitation
Accidental discharge while assessing ECG
Mild shock
5
Paramedic
Resuscitation
Shock received at time of defibrillatory shock
Discomfort to right arm; admitted to hospital for observation
6
Paramedic
Resuscitation
Arc from paddle to electrode on patient’s chest
Ringing in ears; admitted to hospital for observation
7
Nurse
Resuscitation
Unclear
Mild burn to hand
8
Paramedic
Resuscitation
Equipment failure; spontaneous discharge; after charging; arc from paddles to electrode on patient’s chest
Mild shock
9
Paramedic
Resuscitation
Equipment failure; Machine would not hold charge; operator received shock from touching charge button
Mild shock
10
Paramedic
Resuscitation
Shock received at time of defibrillatory shock
Admitted to hospital for observation
11
Paramedic
Testing defibrillator
Accidental discharge
Second degree burn to thigh
12
Trainer
Training
Accidental discharge during demonstration; hands placed over the paddle electrode
Shock to arms
13
Biomedical technician
Testing defibrillator
Shock occurred while testing machine after replacing paddles
Shock to hand and knee
fibrillator paddles against each of his temples and jokingly asked if they would work for electroconvulsive shock therapy. Without realizing the paddles were charged, he then discharged the defibrillator. He immediately slumped to the floor and was unresponsive for 5 minutes. For the next 36 hours he was noted to be listless. He had retrograde amnesia and minor second degree burns to the face. His recovery was complete with no late sequelae.’ There have been no reports of deaths following accidental injury from defibrillatory shocks. The purpose of our study was to document the frequency, type, and seriousness of injuries to the operators of defibrillator machines. The injury rates for paramedics, (1 injury per 1,700 defibrillatory shocks) and for EMT-Ds (1 per 1,000 shocks) are encouraging. The infrequent occurrence of accidental shocks, as well as the relative lack of serious, associated morbidity, suggests good training, careful behavior, and the inherent low risk of the procedure to the user. The types of injuries one would expect to see, cardiac arrhythmias, skin bums, and myocardial muscle damage, are dependent on a number of factors. These factors include the amount of energy, the distance from the source, the patMow of the energy, and the resistance between the shocker and shockee. The amount of energy (joules or watt-seconds) de-
livered from a defibrillator is a function of the electrical charge (volts), the flow of electricity (current or amperes), and the duration of flow (seconds): Energy (J) = potential (V) x current (A) x duration (s). Defibrillators deliver peak electrical current to defibrillate a fibrillating heart. The electrical power (watts) is defined as the product of the voltage and the current: Power (W) = potential (V) x current (A). Generally, defibrillators deliver 60,000 watts during an extremely brief period such as 4 to 5 milliseconds, with a resulting energy level of 300 joules (watt-seconds).4 This high energy delivered over a short time is analogous to the electrical energy of a lightning strike, though much smaller in total joules. A lightning strike can deliver 10 million to 2 billion volts and 20,000 to 200,000 amperes in one millisecond.’ In general, a lightning type of electrical injury rarely causes tissue damage or bums because it occurs over such a short period that there is no skin breakdown and no internal electrical current is generated. Death is most often a result of cardiopulmonary arrest caused by the direct electrical current. Additionally, the amount of current delivered
AMERICAN
104
is dependent (ohms):
on the potential
Current (A) =
JOURNAL
(volts) and the resistance
potential (V) resistance
(a) ’
Therefore, the condition of the emergency personnel (eg, wet clothes, their relationship to the defibrillator paddles) will change the resistance and accordingly influence the severity of the electric injury. The difference in the rates of injuries between paramedics and EMT-Ds should not be over-interpreted because the data were not obtained in a comparable fashion. The survey of EMT-D injuries was based on reports to the medical director of the EMT-D program and may represent an underreporting of actual injuries. EMT-Ds may not have bothered to report minor electric shocks, especially if they thought the injuries were trivial or possible disciplinary action could result. Although there was a 100% response rate for paramedics, actual injuries may have been minimized or underreported. An injury rate for reports to the Product Monitoring Branch of the FDA cannot be estimated because there are no denominator data. Furthermore, the accounts of injuries are probably underreported because reporting is voluntary. For instance. our own exverience in Kine Countv was not reported to the FDA. Nevertheless, one would expect serious injuries to be reported, and their absence is encouraging. Are there lessons to be learned from this experience? Can steps be taken to decrease further the likelihood of injuries to emergency personnel? The Textbook of Advanced Cardiac Life Support offers recommendations for proper maintenance to minimize machine malfunction.6 These include daily visual inspections and weekly discharge tests. These recommendations are designed to prevent injuries due to machine failure or malfunction, such as what could occur with a cracked handle or broken cable. These recommendations are sensible, but they will not guarantee safety, as seen in case 1 in Table 1 and cases 8 and 9 associated with machine failure in Table 2. What is needed are comparable recommendations for safety at the time of operation. EMT-Ds in King County, as part of their training, receive special instructions in defibril1
OF EMERGENCY
MEDICINE
m Volume
8.
Number 2 l March 1990
lator safety. They are instructed to say loudly, immediately before each shock, “One, I’m clear. Two, you’re clear. Three, ready to shock.” Such a verbal reminder forces the operator to proceed through a series of visual safety checks and verbal warnings before delivering a defibrillatory shock. Almost all injuries’s reported by paramedics and EMT-Ds in King County resulted from accidental contact with the patient, stretcher, or respiratory equipment at the time of defibrillatory shock. Stressing defibrillator safety and making the verbal and visual check an integral part of protocols and standing orders will help minimize the risk of accidental shock. The incidence and morbidity of defibrillator-associated injuries to prehospital emergency personnel is low. and the nature of the injuries is minimal, with no lasting sequelae. This good experience adds support to the notion that use of defibrillators, including automatic defibrillators, by EMTs and first responders is both safe and life saving. However, one should not be complacent, and safety must continue to be stressed. The safety of emergency personnel and their patients is always the first priority in any resuscitation. The authors thank the paramedics of King County, WA, for their willingness to participate in this survey and for sharing their shocking experiences. Richard 0. Cummins, MD, Medical Director of the King County EMT-D program, provided information on EMT-D injuries and training procedures. Tom Hearne, PhD, and Steve Call provided administrative support. Judy Prentice helped with the survey and assisted in manuscript preparation.
REFERENCES 1. Trimble C: Blind defibrillation by basic EMTs. J Am Coil Emerg Phys 19765543-544 2. Eisenberg MS, Bergner L, Hallstrom AP: Paramedic programs and out-of-hospital cardiac arrest: I. Factors associated with successful resuscitation. Am J Public Health 1979;69:30-38 3. lserson KV, Barsan WG: Accidental “cranial” defibrillation. J Am Coll Emerg Phys 1979;8:24-25 4. Cummins RO: Defibrillation. Emerg Med Clin North Am 1988;6:217-239 5. Cooper MA: Lightning injuries. In Rosen P, Baker FJ, Braen GR, et al (eds): Emergency Medicine: Concepts and Clinical Practice, St Louis, MO, Mosby, 1986, pp 631-636 6. Albarran-Sotelo R, Atkins JM, Bloom RS, et al: Textbook of Advanced Cardiac Life Support. Dallas. TX. American Heart Association, 1987, p 93
Since the advent of lightweight defibrillators and their use in the field by paramedics, a countless number of lives has been saved. At the inception of paramedic programs, defibrillator use by nonmedical personnel was met with considerable criticism. Their use by nonmedical personnel was considered to be practicing medicine without a license. It was thought that risks to the patient and to emergency personnel were too great, and that defibrillator use must be under tight supervision.’ Defibrillatory shocks, while often lifesaving, also have potential for harm. For a patient in ventricular fibrillation, the possibility of skin burns and myocardial muscle damage is clearly worth the risk given the grave clinical condition. However, for the individual administering the shock the possibility of harm must be low, and the type of injury must be acceptably minor. Injuries to patients receiving defibrillatory shocks have been described, but other than anecdotal re-
From the ‘Center for Evaluation of Emergency Medical Services, King County Health Department, Emergency Medical Services Division, and the tDepartment of Medicine, University of Washington, Seattle. Manuscript received March 9, 1989; revision accepted May 12, i 989. Address reprint requests to Dr Eisenberg: Center for the Evaluation of Emergency Medical Services, 110 Prefontaine PI, S, Suite 500, Seattle, WA 98104. Key Words: Electric countershock, defibrillation, adverse effects, emergency medical services, cardiac arrest, cardiopulmonary resuscitation. 0 1990 by W.B. Saunders Company. 0735-6757/90/0802-0004$5.00/O
ports, there have been no published studies of injuries to individuals administering defibrillatory shocks.‘*’ The use of defibrillators has increased substantially, and with automatic defibrillators the number of defibrillator shocks performed will increase even more. Therefore, we need to assess frequency, type, and rate of injuries to individuals providing defibrillatory shocks to patients in cardiac arrest. We believe that this is a safe procedure that can be performed satisfactorily by nonmedical personnel. METHODS Information about injuries to operators of defibrillators was obtained from two sources. The first source of information was a survey conducted among prehospital emergency personnel in King County, WA. The King County emergency medical service (EMS) system uses a tiered response system composed of emergency medical technicians (EMTs) and paramedics. The first emergency vehicle to arrive is staffed with EMTs or EMTs trained in defibrillation (EMTDs), and the second vehicle is staffed with paramedics. There are 500 EMT-Ds, who are authorized to provide defibrillatory shocks for ventricular fibrillation, and 63 paramedics, who provide advanced cardiac life support, employed in the King County EMS system. The EMT-Ds and the paramedics used manual defibrillators at the time of this survey. In May 1988 a questionnaire was mailed to every paramedic working in the King County EMS system. The questionnaire asked for a description of any episode in which the paramedic or a bystander received an accidental shock or injury from a defibrillatory shock and asked for the number of years employed full-time as a paramedic. The King County EMS system has been in operation since 1975, but it has been operating fully only since 1979. In general, our study of the King County paramedics has focused on the last 10 years. Each questionnaire for which an incident was reported was followed up with a phone interview to obtain more information. Only those incidents in which the paramedic was personally involved were used. In addition to injuries to paramedics, accounts of all reported detibrillatorassociated injuries from the last 7 years to EMT-Ds were obtained from the medical director of the King County EMT defibrillation program (Richard 0. Cummins, personal communication, January, 1989). The total number of defibrillatory shocks delivered to patients in King County was determined from a cardiac arrest surveillance system. This system has collected information, including the number of defibrillatory shocks delivered during a resuscitation, on every prehospital cardiac arrest receiving emergency care since the inception of the paramedic 101
AMERICAN JOURNAL OF EMERGENCY MEDICINE m Volume 8, Number 2 n March 1990
102
program in 1975.* An injury rate was calculated, based on the total shocks delivered and the number of injuries. Reports from throughout the United States to the Product Monitoring Branch of the Food and Drug Administration (FDA) were also used. Injuries either to the equipment operator or to the patient or device failures have been required to be reported to the Product Monitoring Branch since 1984. These records were obtained through the Freedom of Information Act and were reviewed for the period from January 1984 through September 1987. RESULTS Questionnaires were completed by all 63 paramedics. They reported five episodes of injuries to themselves and one episode of injury to an EMT. In addition, there were two episodes of accidental injury to EMT-Ds. The episodes involving the paramedics and EMT-Ds are summarized in Table 1. The most serious injury (case 1) was the result of a cracked defibrillator paddle; the paramedic received the shock at the time of defibrillation and recalls “blacking out” for 1 to 2 minutes. He was hospitalized for 3 days and required lidocaine for premature ventricular contractions. The crack was later found by the manufacturers’ technician and was not detectable by visual inspection. All the other injuries (cases 2 through 8) were results of accidental contact with the patient or stretcher. None of the accidental shocks resulted in permanent injury. In King County, paramedics have treated an average of 310 patients per year over the past 10 years with deflbrillatory shocks, including patients who are in ventricular fibrillation upon arrival of emergency personnel and patients in whom ventricular fibrillation occurs during resuscitation (usually in response to pharmacological intervention). When
defibrillatory shocks are required, paramedics administer an average of 3.2 shocks per patient. Thus, paramedics provide approximately 1,000 defibrillatory shocks per year. The six accidental injuries (five paramedics and one EMT) reported by the paramedics over a IO-year period averages 0.6 injuries per year, or approximately 1 injury per 1,700 shocks. For EMT-Ds two accidental injuries occurred during the 7 years of the EMT-D program. EMT-Ds provide deflbrillatory shocks for approximately 150 patients per year (average of the past 7 years) and administer an average of two shocks per patient. Thus, EMT-Ds experienced approximately 1 injury per 1,000 patient shocks. Both of these injury frequencies are probably overestimations because both EMT-Ds and paramedics use “live” defibrillations during training (Richard 0. Cummins, personal communication, January, 1989). Information obtained from the Product Monitoring Branch of the FDA reported 13 episodes of injuries to operators of defibrillators. Injuries occurred to paramedics, EMTs, nurses, and biomedical technicians. The episodes are summarized in Table 2. Ten of the injuries occurred during resuscitations. The other three were associated with testing and training. In two instances (cases 8 and 9), equipment failure led to a shock of the operator. Arcing of the electric shock from the paddle to an electrode on the patient’s chest occurred in three cases (cases 1,6, and 8). Three individuals were hospitalized for observation. There were no reports of persistent morbidity. DISCUSSION There has been only one case report and a few anecdotal accounts of injuries to operators of detibrillators.‘~3 The most dramatic case involved a physician, participating in an advanced cardiac life support course, who placed the de-
TABLE1. Injuries Associated With Defibrillation Occurring to Paramedics and EMT-Ds in King County, WA, 1979-1988 Case
Personnel
Setting
Circumstances
Nature of Injury
1
Paramedic
Resuscitation
Crack in defibrillator paddle; shock to paramedic occurred during defibrillation
Admitted to hospital for 3 d; frequent premature ventricular contractions requiring lidocaine for 24 h; localized muscle spasms in paramedic’s chest and arms continued for several weeks
2
Paramedic
Resuscitation
Paramedic’s arm was touching side rail of stretcher
Tingling in right arm for 30 min
3
Paramedic
Resuscitation
Hand contact with gel during defibrillation
Mild soreness to right arm
4
Paramedic
Resuscitation
Paramedic was checking femoral pulse; EMT-D defibrillated
Shock knocked paramedic away from patient
5
Paramedic
Resuscitation
Paramedic’s leg was touching patient when shock was delivered
Mild shock to leg
6
EMT
Resuscitation
EMT was holding bag mask at time of defibrillatory shock
Mild shock to tips of fingers
7
EMT-D
Resuscitation
EMT-D’s thumb was in contact with patient’s breast at time of defibrillatory shock
Shock to hand; lethargy for several minutes
8
EMT-D
Resuscitation
EMT-D’s leg was touching stretcher at time of defibrillatory shock
Shock to leg
GIBBS, EISENBERG, AND DAMON H DANGERS OF DEFIBRILLATION
TABLE2. Injuries Associated With Defibrillation January 1984 Through September 1987 Case
Personnel
103
Occurring to Emergency Personnel Reported to the Food and Drug Administration,
Circumstances
Setting
Nature of Injury
1
Paramedic
Resuscitation
Arch from paddle to electrode on patient
Burn to hand; patient also received burn
2
EMT
Resuscitation
Accidental discharge during charging
Mild shock to three EMTs
3
Nurse
Resuscitation
Nurse received shock while defibrillating patient
Tingling sensation to hands, legs, and back
4
Nurse
Resuscitation
Accidental discharge while assessing ECG
Mild shock
5
Paramedic
Resuscitation
Shock received at time of defibrillatory shock
Discomfort to right arm; admitted to hospital for observation
6
Paramedic
Resuscitation
Arc from paddle to electrode on patient’s chest
Ringing in ears; admitted to hospital for observation
7
Nurse
Resuscitation
Unclear
Mild burn to hand
8
Paramedic
Resuscitation
Equipment failure; spontaneous discharge; after charging; arc from paddles to electrode on patient’s chest
Mild shock
9
Paramedic
Resuscitation
Equipment failure; Machine would not hold charge; operator received shock from touching charge button
Mild shock
10
Paramedic
Resuscitation
Shock received at time of defibrillatory shock
Admitted to hospital for observation
11
Paramedic
Testing defibrillator
Accidental discharge
Second degree burn to thigh
12
Trainer
Training
Accidental discharge during demonstration; hands placed over the paddle electrode
Shock to arms
13
Biomedical technician
Testing defibrillator
Shock occurred while testing machine after replacing paddles
Shock to hand and knee
fibrillator paddles against each of his temples and jokingly asked if they would work for electroconvulsive shock therapy. Without realizing the paddles were charged, he then discharged the defibrillator. He immediately slumped to the floor and was unresponsive for 5 minutes. For the next 36 hours he was noted to be listless. He had retrograde amnesia and minor second degree burns to the face. His recovery was complete with no late sequelae.’ There have been no reports of deaths following accidental injury from defibrillatory shocks. The purpose of our study was to document the frequency, type, and seriousness of injuries to the operators of defibrillator machines. The injury rates for paramedics, (1 injury per 1,700 defibrillatory shocks) and for EMT-Ds (1 per 1,000 shocks) are encouraging. The infrequent occurrence of accidental shocks, as well as the relative lack of serious, associated morbidity, suggests good training, careful behavior, and the inherent low risk of the procedure to the user. The types of injuries one would expect to see, cardiac arrhythmias, skin bums, and myocardial muscle damage, are dependent on a number of factors. These factors include the amount of energy, the distance from the source, the patMow of the energy, and the resistance between the shocker and shockee. The amount of energy (joules or watt-seconds) de-
livered from a defibrillator is a function of the electrical charge (volts), the flow of electricity (current or amperes), and the duration of flow (seconds): Energy (J) = potential (V) x current (A) x duration (s). Defibrillators deliver peak electrical current to defibrillate a fibrillating heart. The electrical power (watts) is defined as the product of the voltage and the current: Power (W) = potential (V) x current (A). Generally, defibrillators deliver 60,000 watts during an extremely brief period such as 4 to 5 milliseconds, with a resulting energy level of 300 joules (watt-seconds).4 This high energy delivered over a short time is analogous to the electrical energy of a lightning strike, though much smaller in total joules. A lightning strike can deliver 10 million to 2 billion volts and 20,000 to 200,000 amperes in one millisecond.’ In general, a lightning type of electrical injury rarely causes tissue damage or bums because it occurs over such a short period that there is no skin breakdown and no internal electrical current is generated. Death is most often a result of cardiopulmonary arrest caused by the direct electrical current. Additionally, the amount of current delivered
AMERICAN
104
is dependent (ohms):
on the potential
Current (A) =
JOURNAL
(volts) and the resistance
potential (V) resistance
(a) ’
Therefore, the condition of the emergency personnel (eg, wet clothes, their relationship to the defibrillator paddles) will change the resistance and accordingly influence the severity of the electric injury. The difference in the rates of injuries between paramedics and EMT-Ds should not be over-interpreted because the data were not obtained in a comparable fashion. The survey of EMT-D injuries was based on reports to the medical director of the EMT-D program and may represent an underreporting of actual injuries. EMT-Ds may not have bothered to report minor electric shocks, especially if they thought the injuries were trivial or possible disciplinary action could result. Although there was a 100% response rate for paramedics, actual injuries may have been minimized or underreported. An injury rate for reports to the Product Monitoring Branch of the FDA cannot be estimated because there are no denominator data. Furthermore, the accounts of injuries are probably underreported because reporting is voluntary. For instance. our own exverience in Kine Countv was not reported to the FDA. Nevertheless, one would expect serious injuries to be reported, and their absence is encouraging. Are there lessons to be learned from this experience? Can steps be taken to decrease further the likelihood of injuries to emergency personnel? The Textbook of Advanced Cardiac Life Support offers recommendations for proper maintenance to minimize machine malfunction.6 These include daily visual inspections and weekly discharge tests. These recommendations are designed to prevent injuries due to machine failure or malfunction, such as what could occur with a cracked handle or broken cable. These recommendations are sensible, but they will not guarantee safety, as seen in case 1 in Table 1 and cases 8 and 9 associated with machine failure in Table 2. What is needed are comparable recommendations for safety at the time of operation. EMT-Ds in King County, as part of their training, receive special instructions in defibril1
OF EMERGENCY
MEDICINE
m Volume
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Number 2 l March 1990
lator safety. They are instructed to say loudly, immediately before each shock, “One, I’m clear. Two, you’re clear. Three, ready to shock.” Such a verbal reminder forces the operator to proceed through a series of visual safety checks and verbal warnings before delivering a defibrillatory shock. Almost all injuries’s reported by paramedics and EMT-Ds in King County resulted from accidental contact with the patient, stretcher, or respiratory equipment at the time of defibrillatory shock. Stressing defibrillator safety and making the verbal and visual check an integral part of protocols and standing orders will help minimize the risk of accidental shock. The incidence and morbidity of defibrillator-associated injuries to prehospital emergency personnel is low. and the nature of the injuries is minimal, with no lasting sequelae. This good experience adds support to the notion that use of defibrillators, including automatic defibrillators, by EMTs and first responders is both safe and life saving. However, one should not be complacent, and safety must continue to be stressed. The safety of emergency personnel and their patients is always the first priority in any resuscitation. The authors thank the paramedics of King County, WA, for their willingness to participate in this survey and for sharing their shocking experiences. Richard 0. Cummins, MD, Medical Director of the King County EMT-D program, provided information on EMT-D injuries and training procedures. Tom Hearne, PhD, and Steve Call provided administrative support. Judy Prentice helped with the survey and assisted in manuscript preparation.
REFERENCES 1. Trimble C: Blind defibrillation by basic EMTs. J Am Coil Emerg Phys 19765543-544 2. Eisenberg MS, Bergner L, Hallstrom AP: Paramedic programs and out-of-hospital cardiac arrest: I. Factors associated with successful resuscitation. Am J Public Health 1979;69:30-38 3. lserson KV, Barsan WG: Accidental “cranial” defibrillation. J Am Coll Emerg Phys 1979;8:24-25 4. Cummins RO: Defibrillation. Emerg Med Clin North Am 1988;6:217-239 5. Cooper MA: Lightning injuries. In Rosen P, Baker FJ, Braen GR, et al (eds): Emergency Medicine: Concepts and Clinical Practice, St Louis, MO, Mosby, 1986, pp 631-636 6. Albarran-Sotelo R, Atkins JM, Bloom RS, et al: Textbook of Advanced Cardiac Life Support. Dallas. TX. American Heart Association, 1987, p 93
