Scales of reaction to electric shock. Thresholds and biophysical mechanisms

Safety of a High-Efficiency Electrical Fence Energizer

INTRODUCTION

Our primary goal was to evaluate the performance of a new high-efficiency electric fence energizer unit using resistive load changes. Our secondary goal was to test for compliance with the classical energy limits and the newer charge-based limits for output.

METHODS

We tested 4 units of the Nemtek Druid energizer with 2 channels each. We used a wide load-resistance range to cover the worst-case scenario of a barefoot child making a chest contact (400 Ω) up to an adult merely touching the fence (2 kΩ).

RESULTS

The energy output was quite consistent between the 8 sources. Even at the lowest resistance, 400 Ω, the outputs were well below the IEC 60335-2-76 limit of 5 J/pulse. The charge delivered was also quite consistent. Even at the lowest resistance, 400 Ω, the outputs (679 ± 23 μC) were well below the proposed limits of 4 mC for short pulses.

CONCLUSIONS

The high-efficiency electric fence energizers satisfied all relevant safety limits. Charge, energy, voltage, and current outputs were consistent between channels and units.

Assessment of Electrosurgery Burns in Cardiac Surgery

BACKGROUND

Monopolar surgery is applied mostly in major operations, while bipolar is used in delicate ones. Attention must be paid in electrosurgery application to avoid electrical burns.

OBJECTIVES

We aimed to assess factors associated with electrosurgery burns in cardiac surgery operating rooms.

PATIENTS AND METHODS

This was a case-control study in which two groups of 150 patients undergoing cardiac surgery in Imam Khomeini Hospital were recruited. Several factors like gender, age, operation duration, smoking, diseases, infection, atopia, , immunosuppressive drugs use, hepatic cirrhosis, and pulmonary diseases were compared between the two groups. Patients were observed for 24 hours for development of any burn related to the operation. Data was analyzed using SPSS v.11.5, by Chi square and T-test.

RESULTS

Patients in the two groups were similar except for two factors. DM and pulmonary diseases which showed significant differences (P = 0.005 and P = 0.002 respectively). Seventy-five patients from controls and 35 from the study group developed burns, which was significant (P ˂ 0.0001).

CONCLUSIONS

None of the factors were significantly related to developing burns. The differences between the two groups highlights the importance of systems modifications to lessen the incidence of burns.

Tc-99m pyrophosphate imaging of poloxamer-treated electroporated skeletal muscle in an in vivo rat model

OBJECTIVE

This study investigates whether (99m)Tc pyrophosphate (PYP) imaging provides a quantitative non-invasive assessment of the extent of electroporation injury, and of the effect of poloxamer in vivo on electroporated skeletal muscle.

METHODS

High-voltage electrical shock was used to produce electroporation injury in an anesthetized rat's hind limb. In each experiment, the injured limb was treated intravenously by either poloxamer-188, dextran, or saline, and subsequently imaged with (99m)Tc PYP. The radiotracer's temporal behavior among the experimental groups was compared using curve fitting of time-activity curves from the dynamic image data.

RESULTS

The washout kinetics of (99m)Tc PYP changed in proportion to the electric current magnitude that produced electroporation. Also, (99m)Tc PYP washout from electroporated muscle differed between poloxamer-188 treatment and saline treatment. Finally, 10-kDa dextran treatment of electroporated muscle altered (99m)Tc PYP washout less than poloxamer-188 treatment.

CONCLUSIONS

Behavior of (99m)Tc PYP in electroporated muscle appears to be an indicator of the amount of electroporation injury. Compared to saline, intravenous polaxamer-188 treatment reduced the amount of (99m)Tc PYP uptake. Coupled to results showing poloxamer-188 seals ruptured cellular membranes, lessens the extent of electroporation injury and improves cell viability, (99m)Tc PYP imaging appears to be a useful in vivo monitoring tool for the extent of electroporation injury.

Influence of electricity on post-mortal body temperature

In a case of suicidal application of electricity differences between the rectal temperature of the body and the suspected time of death were observed. In order to answer the question whether an electric current from hand to hand over >30 min led to a rise in body temperature FEM-based computer simulations and animal experiments were carried out. Both resulted in a warming of the soft parts in the arm without warming the body core. Thus a temperature-based estimation of the time since death can also be used in cases with electricity as the cause of death. Besides, in the animal experiment we found a spontaneous rise in the body core temperature even without application of electricity which may be a reason for the typical temperature plateau after death.

Development of brain damage as measured by brain impedance recordings, and changes in heart rate, and blood pressure induced by different stunning and killing methods

Poultry are electrically stunned before slaughter to induce unconsciousness and to immobilize the chickens for easier killing. From a welfare point of view, electrical stunning should induce immediate and lasting unconsciousness in the chicken. As an alternative to electroencephalography, which measures brain electrical activity, this study used brain impedance recordings, which measure brain metabolic activity, to determine the onset and development of brain damage. Fifty-six chickens were surgically equipped with brain electrodes and a canula in the wing artery and were subjected to one of seven stunning and killing methods: whole body electrical stunning; head-only electrical stunning at 50, 100 or 150 V; or an i.v. injection with MgCl2. After 30 s, the chickens were exsanguinated. Brain impedance and blood pressure were measured. Extracellular volume was determined from the brain impedance data and heart rate from the blood pressure data. An immediate and progressive reduction in extracellular volume in all chickens was found only with whole body stunning at 150 V. This treatment also caused cardiac fibrillation or arrest in all chickens. With all other electrical stunning treatments, extracellular volume was immediately reduced in some but not all birds, and cardiac fibrillation or arrest was not often found. Ischemic conditions, caused by cessation of the circulation, stimulated this epileptic effect. A stunner setting of 150 V is therefore recommended to ensure immediate and lasting unconsciousness, which is a requirement for humane slaughter.

Biophysical injury mechanisms in electrical shock trauma

Electrical shock trauma tends to produce a very complex pattern of injury, mainly because of the multiple modes of frequency-dependent tissue-field interactions. Historically, Joule heating was thought to be the only cause of electrical injuries to tissue by commercial-frequency electrical shocks. In the last 15 years, biomedical engineering research has improved the understanding of the underlying biophysical injury mechanisms. Besides thermal burns secondary to Joule heating, permeabilization of cell membranes and direct electroconformational denaturation of macromolecules such as proteins have also been identified as tissue-damage mechanisms. This review summarizes the physics of tissue injury caused by contact with commercial-frequency power lines, as well as exposure to lightning and radio frequency (RF), microwave, and ionizing radiation. In addition, we describe the anatomic patterns of the resultant tissue injury from these modes of electromagnetic exposures.

Electrical stunning and exsanguination decrease the extracellular volume in the broiler brain as studied with brain impendance recordings

Electrical stunning in the process of slaughtering poultry is used to induce unconsciousness and immobilize the animal for easier processing. Unconsciousness is a function of brain damage. Brain damage has been studied with brain impedance recordings under ischemic conditions. This experiment studies brain impedance as a response to a general epileptiform insult caused by electrical stunning and ischemia caused by exsanguination. Brain impedance was recorded in 10 broiler chickens for each of three killing methods: whole body electrical stunning, which induces cardiac arrest; head only electrical stunning followed by exsanguination; and exsanguination without stunning. Brain impedance was converted into relative extracellular volume (ECV) values. Results showed that, immediately after electrical stunning, the ECV decreased 5.5% from base ECV. With exsanguination only, the ECV decreased from base ECV only after 4 min after neck cutting. The ECV decrease after 10 min did not differ between treatments. With a time of 228 s to reach one-half of the ECV decrease found at 10 min, electrical stunning resulted in a much faster change in ECV than exsanguination only (373 s). Within the head only stunning group, six animals showed a response similar to that found with whole body stunning; the other four animals responded similarly to the animals that were exsanguinated only. It was concluded that brain impedance recordings used with electrical stunning reflect brain damage. This damage was both epileptic and ischemic in nature. Whole body stunning induced immediate brain damage, suggesting that an adequate stun was delivered. The dual response found with head only stunning might indicate that this stunning method does not always produce an adequate stun.

Histological characterization of hemorrhages in muscles of broiler chickens

Hemorrhages in meat of broiler chickens are major quality defects. The objective of our study was to characterize the various types of hemorrhages in thigh and breast muscles with respect to their morphological appearance, location, and origin. Chickens were stunned using a water-bath stunner and were either exsanguinated and fixed or perfused with fixative. The morphological appearance of the hemorrhages was determined by the type of tissue in which they were found and by the amount of extravasating blood. Origins of hemorrhages were found only at sites of rupture of venous structures, such as postcapillary venules and small collecting veins. The absence of significant leukocyte infiltration strongly indicated that muscle tissue damage and hemorrhage occurred within the 24 h preceding stunning and slaughter. The locations and types of hemorrhages indicate different underlying mechanisms.

Body surface potentials during discharge of the implantable cardioverter defibrillator

INTRODUCTION

Little is known about the hazard for persons in contact with patients experiencing a high-voltage discharge of their implantable cardioverter defibrillator (ICD). Compared to epicardial systems, this risk may be increased with transvenous electrode systems and particularly in active can configurations.

METHODS AND RESULTS

In 23 patients with a transvenous active can ICD system, body surface potentials Vs and current through an external resistance were measured during 35 discharges. Vs was detected using skin electrodes positioned over the left subpectorally implanted pulse generator [C], apex of the heart [A], and the right pectoral region [RP]. Mean Vs during discharges without an external shunt resistance ranged between 13 and 63.8 V [C to A] and 12.5 to 47.3 V [C to RP] (ICD peak stored/output voltage Vcap = 183 to 606 V, n = 20). Mean current flow [C to A] was 8.2 to 46.8 mA (Vcap = 288 to 633 V, n = 10) and 42 to 120.7 mA (Vcap = 447 to 579 V, n = 5) across a resistance of 1,696 and 797 omega, respectively.

CONCLUSION

During high-output shocks, a considerable potential difference is present on the body surface of ICD patients that, according to the literature, may induce a single cardiac response in a bystander. Analogous to spontaneous extrasystoles, there is only a minimal chance of triggering a tachyarrhythmia by this stimulated extra beat. Direct induction of ventricular fibrillation is unlikely, since reported fibrillation threshold values are much higher than the observed magnitudes of current and voltage.

Susceptibility of broiler chickens to hemorrhages in muscles: the effect of stock and rearing temperature regimen

In this study, the effect of genetic constitution (stock) and rearing temperature on the occurrence of hemorrhages in thighs and breasts of water bath stunned broilers was investigated. Particular attention was given to the relation between the susceptibility for hemorrhages, body composition, and adaptations in blood variables induced by low rearing temperatures. A factorial experiment was performed with five parental stocks, differing with respect to growth rate, feed conversion, and body composition, and two temperature regimens (thermoneutral and below the zone of thermoneutrality). Hemorrhage scores in thighs were dependent on rearing temperature, not on stock, and were highest in broilers reared at low temperatures. In all stocks, high scores in the thighs were accompanied by an increased carbon dioxide pressure and bicarbonate and triiodothyronine concentration of the venous blood, and by an increased relative heart weight, hematocrit, and blood loss at slaughter. Hemorrhage scores in breasts were dependent on stock, confounded with day of scoring. An effect of rearing temperature was present only for the leanest, slow-growing stock having the lowest feed conversion ratio at thermoneutral rearing conditions. Scores in breasts were related neither to body composition nor to metabolic and hemodynamic adaptations to low rearing temperatures. It is concluded that high hemorrhage scores in thighs are related to hemodynamic and metabolic adaptations to an increased need for energy and oxygen caused by low rearing temperatures. Hemorrhage scores are not related to stock-dependent differences.

Injury by electrical forces: pathophysiology, manifestations, and therapy

The pathogenesis and pathophysiologic features of electrical injury are more complex than once thought. The relative contributions of thermal and pure electrical damage depend on the duration of electric current passage, the orientation of the cells in the current path, their location, and other factors. If the contact time is brief, nonthermal mechanisms of cell damage will be most important and the damage is relatively restricted to the cell membrane. When contact time is much longer, however, heat damage predominates and the whole cell is affected directly. These parameters also determine the anatomic tissue distribution of injury. Damage by Joule heating is not known to be dependent on cell size, whereas larger cells are more vulnerable to membrane breakdown by electroporation. Cells do survive transient plasma membrane rupture under appropriate circumstances or if therapy is instituted quickly. If membrane permeabilization is the primary cellular pathologic condition, then injured tissue may be salvageable and the challenge for the future is to identify a technique to reseal the damaged membranes promptly. Present standards of care for electrical injury require a fully staffed and well-equipped intensive care unit, available operating suites, and the availability of the full range of medical specialists. Major teaching hospitals with burn centers may be the ideal setting for the treatment of an electrical trauma victim. After the initial resuscitation, efforts are directed primarily towards preventing additional tissue loss mediated through the compartment syndrome, compressive neuropathies, or the presence of necrotic tissue. Renal and cardiac failure caused by the release of intracellular muscle contents into the circulation must be prevented. Attention can then be directed towards maximizing tissue salvage and preventing late skeletal and neuromuscular complications. Reconstructive procedures that transfer healthy tissue from a distance are necessary to optimize the functional value of the remaining tissue. Finally, unless the patient is rehabilitated psychologically, the real benefit from other sophisticated care will not be fully realized. These goals are important throughout the acute care of the patient. In the future, new guidelines for treating electrical trauma will be based on a clearer understanding of the relevant pathophysiologic features. These strategies will rely on improved diagnostic imaging and on reversing the fundamental problem of cell membrane damage. Moreover, complex biochemical and organ system pathophysiologic interactions will require careful management. If successful, research efforts presently underway should improve the prognosis of victims after electrical trauma.

Observations on the Electric Lance and the Welfare of Whales: A Critical Appraisal

Japanese whalers use the electric lance as a secondary method of killing minke whales (Balaenoptera acutorostrata). The lances are dropped into the body, and currents varying between 2.2 and 14. OA, with a mean of 6.8A, are applied.

When currents of 5A were applied to the carcasses of dead whales, varying in size from 1.8 to 15.7m in length, no current densities induced in the target organs were sufficient to cause either insensibility (10mA cm−2 in the brain), or to cause ventricular fibrillation (0.5mA cm−2 in the heart), except in a few cases where electrodes were specifically placed to span the heart. When electrodes were placed in positions normally used in whaling operations, no current densities were produced which would have been sufficient to cause brain and cardiac dysfunction.

Further investigations on changes in current density with time post mortem after application of a controlled current of 5A showed, during a 60 hour period, a fourfold increase in the current density in the heart, and more than a twofold increase in the brain. Thus contrary to previous criticisms, if these studies had been carried out on live animals, all current densities would have been below threshold values.

There are no records of signs of epileptic form seizure, which are associated with an effective electrical stun, in whales subjected to the electric lance.

It is concluded that the electric lance as used in whaling operations is ineffective and likely to cause extra pain and suffering to an already distressed animal.

Assessment of the humane aspects of electric lancing of whales by measurement of current densities in the brain and heart of dead animals

The potential physiological effects of the electric lance are assessed, as used in Japanese whaling operations. Current densities are measured in the brains and hearts of six whales to which a controlled current of 5 A is applied by two electrodes inserted at various sites in the carcasses. The whales vary in size from 1.8 m (22 kg) to 16 m (40 t). The minimum current density in the brain necessary to cause depolarisation of neurones is estimated to be 10 mA cm-2 and to cause ventricular fibrillation is estimated to be 0.5 mA cm-2. No current densities exceeding 4.8 mA cm-2 are recorded in the brain. Very few recordings of current density from the heart are above 0.5 mA cm-2, and they occur only when electrodes are in optimal positions. When electrodes are placed as in whaling operations, no whale over 3 m in length would receive current densities in the heart or brain sufficient to cause permanent dysfunction. It is concluded that electric lancing is ineffective as a secondary method of killing whales and that the current densities recorded could cause pain and suffering to an already distressed animal.

The physicochemical basis for thermal and non-thermal 'burn' injuries

One of the most basic problems of burn science may well be the confusing nomenclature we use. The word 'burn' is used to identify several different mechanisms of tissue injury. This article describes the problem of accurately characterizing and defining the various burn injuries on the basis of molecular events. The most important objective is to distinguish between the various physicochemical injuries on the basis of differences in their fundamental physicochemical mechanisms and physiological consequences. Also, pathophysiologically important biophysical processes such as the central importance of cell membrane permeabilization in acute cellular necrosis, which different types of burn injury have in common, are emphasized. The biophysics of membrane formation and permeabilization is presented to clarify the conditions for membrane damage as well as to discuss the potential for therapeutic intervention. Where feasible, plausible new strategies to reverse the molecular alterations caused by injury are hypothesized.