Impact of Voltage Level on Hospitalization and Mortality in Electrical Injury Cases: A Retrospective Analysis from a Turkish Emergency Department

Introductıon

Injuries caused by electricity, one of today’s important energy sources, range from local skin burns to fatal situations [1]. Almost all electrical injuries occur accidentally and they can affect people of all ages. These accidents often result from preventable causes [2,3]. Physicians need to know what to pay attention to in post-accident treatment and follow-up. Approximately 1000 deaths occur each year in the United States as a result of electrical injuries, and approximately 5% of all burn unit admissions occur as a result of electrical injuries [2]. In the adult population, electrical injuries primarily affect men, are mostly work-related, and are the 4th leading cause of traumatic work-related deaths [3,4]. The most common source point is the hands, followed by the head. The feet are usually the ground point [5].

The current, resistance, voltage, path, and duration of the electrical current are the main factors in determining the severity of tissue damage [1]. The severity of injury depends on several factors, including voltage, amperage, type of current, current path, duration of contact, contact point resistance, and excitation. The most critical factor is voltage, which is divided into 2 main groups: high voltage (>1000 V) and low voltage (<1000 V) [6]. Low-voltage electric current can cause serious injuries similar to high-voltage current, depending on the duration of exposure (eg, if there is prolonged muscle tetany), the size of the individual, and the cross-sectional area in contact with the electrical source [2,7]. High voltages cause deep burns and extensive deep tissue and organ damage [5]. The most fundamental concept for successful management of patients with high-voltage injuries is that there is no relationship between skin burns, vital organ involvement, and injury severit [3]. Electricity takes the path of least resistance, so injuries occur more in tissues with little resistance [5]. For example, skin is among the most resistant tissues, while blood, nerves, and muscles have less resistance. Therefore, deeper injuries occur in internal organs with less resistance [5].

The length of hospital stay of these patients is related to the organs affected. The most commonly used laboratory parameters to understand these are renal function tests, complete blood count, liver function tests, cardiac enzymes and ECG. One of the factors that determine hospitalization is the status of deep tissue injury in the affected tissues after electrical exposure. Compartment syndrome may occur as a result of deep tissue injury, and fasciotomy or amputation may be required in these tissues [1,8].

Most people with electrical injuries first come to the emergency department (ED). Electrical injury should be evaluated and managed as a multisystem injury, as almost no organ is protected against it. Emergency physicians need to better understand and manage these injuries. Therefore, this retrospective study aimed to evaluate the factors associated with hospitalization and 30-day mortality in 327 patients admitted to an ED in Turkey with electrical injuries between March 2019 and December 2023.

Material And Methods

ETHICAL APPROVAL:

The Clinical Research Local Ethics Committee-2 (December 27, 2023; E1-23-4532) approved the study. All researchers unconditionally and wholly complied with the Declaration of Helsinki throughout the study. The dataset was obtained from the hospital electronic archive after approval by the hospital management and the local ethics committee. There was no identifying information about the patients in the dataset. The researchers did not have access to the patients’ names or photographs.

STUDY DESIGN:

This study was planned as a retrospective observational clinical study. The researchers examined the data of patients with electrical injuries who presented at Ankara Bilkent City Hospital ED between March 1, 2019, and December 1, 2023. To protect personal data on patients who came to the ED with ICD (International Classification of Disease) diagnosis codes W86 and W87 were retrospectively scanned from the hospital information system.

The hospital where the study was conducted is a high-capacity hospital that receives referrals from neighboring cities and districts by land and air. This hospital has pediatric and adult EDs. According to hospital proceedure, pediatric trauma patients and adult patients are evaluated in the adult ED. Therefore, adult electrical exposures and pediatric electrical exposures are first evaluated in this ED.

DATA COLLECTION:

Patients were classified as having low- (<1000 volt) or high- (>1000 volt) voltage injuries and were divided into 2 groups: hospitalized and discharged. Patients were evaluated according to their age, sex, electrical voltage, electrical input and output areas, biomarkers – white blood cell, neutrophil, lymphocyte, monocyte, hemoglobin, hematocrit, RDW (red cell distribution width), platelet, sodium, potassium, urea, creatinine, AST (aspartate aminotransferase), ALT (alanine aminotransferase), LDH (lactate dehydrogenase), CK (creatine kinase), myoglobin, troponin, pH, HCO³ [bicarbonate] and lactate – LOS, and 30-day mortality. Electrocardiography (ECG) changes were recorded using the ECG data taken at admission.

PATIENT SELECTION:

Patients who were admitted to the ED due to electrical injuries were included in the study. Patient data were scanned from the information system using the W86 and W87 ICD codes. Since this was a retrospective observational study, patients whose information could not be obtained (those referred to another hospital and those who left the hospital of their own free will) were excluded from the study.

OUTCOME MEASURES:

Hospitalization of patients was examined as the primary outcome, and 30-day mortality was examined as the secondary outcome.

STATISTICAL ANALYSIS:

Data analysis was conducted using SPSS (IBM Corp., Armonk, NY, USA), version 25. Demographic descriptive data of the patients are presented as n and%. The normality of data distribution was assessed using the Shapiro-Wilk test, and since the data did not follow a normal distribution, nonparametric tests were applied. Categorical variables were analyzed using the chi-square test and Fisher’s exact test. The Mann-Whitney U test was employed for comparisons between 2 independent groups. In contrast, the Kruskal-Wallis test was used for multiple independent group comparisons, followed by post hoc analysis with the Mann-Whitney U test. Spearman’s correlation test was applied to analyze numerical variables. The alpha error threshold was set at 0.05. According to the pairwise comparison results of the data that may affect the hospitalization status for hospitalization and discharge, parameters with a p value <0.200 were included in the logistic regression model.

Five patients included in the study died; therefore, the factors affecting mortality could not be examined due to insufficient sample size.

Results

DEMOGRAPHIC CHARACTERISTICS OF PATIENTS:

A total of 327 electrically injured patients who presented to the ED between March 01, 2019, and December 01, 2023, were included; 74.6% were male, the mean age was 25 years, and 76.8% (n=251) had LVI. The most common electrical inlet area was 72.5% of the upper extremity. There was no inlet area in 22%. The most common electrical outlet area was the upper extremity. There was no outlet area in 79.2%. The median length of stay (LOS) was <1 day, 67% (n=219) were discharged from the ED, 18.7% (n=61) were admitted to the ICU, and 5 died by 30-day follow-up (Table 1).

Five patients died in the patient group examined. Three of these patients had sudden cardiac arrest. One had a head injury after electrical exposure and died from subarachnoid hemorrhage and multiple skull fractures. One patient died on the 3^rd day in the ICU due to third-degree burns extending from the forearm to the back.

DISTRIBUTION AND COMPARISON OF LOW AND HVI ACCORDING TO PATIENT DATA:

The mean age of patients exposed to low voltage was 23.52 years, and that of those exposed to HVI was 32.26 years, and the difference between the 2 groups was significant (p<0.001). The mean LOS was 1.05 days in the low-voltage group and 11.32 days in the high-voltage group, and there was a significant difference between the 2 groups (p<0.001). There were 215 patients without electrical outlet areas in the low-voltage group (p<0.001). Patients with upper-extremity electrical inlet areas and patients without electrical inlet areas were significantly more likely to be discharged from the ED without hospitalization (p=0.013; Z=−4.873). Patients without electrical inlet areas were also significantly more likely to be discharged from the ED without hospitalization (p<0.001; Z=−3.437).

Patients in the low voltage group were significantly more often discharged from the ED without hospitalization (p<0.001). When the ECGs of the patients were examined, abnormalities were found in the ECGs of more patients in the high-voltage group (p<0.001) (Table 2).

HOSPITALIZATION OF PATIENTS: Males were significantly more likely to be hospitalized (p<0.001). The median age of hospitalized patients was 22 years (p=0.043). Patients exposed to high voltage were significantly more likely to be hospitalized (p<0.001). Those with upper-extremity inlets and those without electrical inlet areas were more likely to be discharged from the ED without hospitalization (p=0.013; Z=−4.873). Patients without an electric outlet area were discharged more frequently (p<0.001; Z=−3.437). Patients with normal ECGs were more likely to be discharged from the ED without hospitalization (p<0.001; z=−6.369) (Table 3).

COMPARISON OF PATIENTS’ LABORATORY DATA WITH HOSPITALIZATION: When the hospitalization of the patients was examined with biomarkers; WBC, neutrophil, platelet, urea, AST, ALT, LDH, CK, myoglobin, troponin, lactate values were found to be significantly higher in hospitalized patients (p<0.001; p<0.001; p<0.001; p<0.001; p<0.001; p<0.001; p<0.001; p<0.001; p<0.001; p<0.001; p<0.001). HCO3 was lower in hospitalized patients (p<0.001) (Table 4).

LOGISTIC REGRESSION ANALYSIS OF DATA:

Logistic regression analysis was performed with the backward elimination method to evaluate the differences between hospitalized and non-hospitalized patients. Age, electrical input area, electrical output area, ECG findings, sex, electrical exposure type, WBC, neutrophil, lymphocyte, platelet, urea, AST, ALT, LDH, CK, myoglobin, troponin, HCO3, and lactate variables were included in the analysis. The probability of hospitalization decreased with increasing age (B=−0.051, S.E.=0.017, p=0.003, OR=0.950, 95% CI: 0.920–0.982). The risk of hospitalization was higher in patients with ECG changes than in those without (B=2.044, S.E.=0.903, p=0.024, OR=7.724, 95% CI: 1.317–45.302). The type of electrical exposure was also a significant variable; patients with a certain type of exposure had a higher risk of hospitalization (B=1.651, S.E.=0.578, p=0.004, OR=5.212, 95% CI: 1.679–16.174). Each unit increase in LDH level increases the probability of hospitalization (B=0.006, S.E.=0.002, p=0.025, OR=1.006, 95% CI: 1.001–1.010). Similarly, an increase in myoglobin level is also associated with the probability of hospitalization (B=0.002, S.E.=0.001, p=0.022, OR=1.002, 95% CI: 1.000–1.004). The constant term of the model was found to be statistically significant (B=−2.055, S.E.=0.814, p=0.012), indicating that the basic risk of hospitalization was low. The explanatory power of the model was calculated as Negelkerke R2=0.568 (Table 5).

Discussion

Electrical injuries are a preventable cause of mortality and morbidity. In this study, we examined the data of patients exposed to electric shock – 74.6% of the patients were male, the median age was 24 years, 76.8% of the patients had LVI (low-voltage injuries), and 87.5% (n=286) were exposed to electrical injuries at work. The most common electrical entry site was the upper extremity (72.5%). The median hospital stay was <1 day. The mortality rate was 1.5%. LOS was significantly longer in patients exposed to high voltage. Patients exposed to low voltage were discharged earlier. Patients with normal ECGs were more likely to have been exposed to low voltage. Males were more likely to be hospitalized. Older patients were more likely to be discharged earlier. Patients with upper-extremity electrical entries and no electrical exit sites were discharged earlier. Logistic regression analysis was performed to understand the factors affecting hospitalization, showing that hospitalization decreased with increasing age, hospitalization increased in patients with ECG changes, and patients with high-voltage injuries were more likelt to be hospitalized. High levels of LDH and myoglobin also were associated with increased risk of hospitalization. The explanatory power of the model was Negelkerle R2=0.568.

Most patients with electrical injuries are men, and this is consistent with studies conducted in our Turkey and other countries [1,9,10]. We believe that men’s higher rate of electric shock is due to their work in construction and industrial areas. In fact, 87.5% of the patients were injured by electricity at work.

LVI were observed most frequently in our study, which is consistent with other studies [11]. The literature indicates the duration of hospitalization is shorter in patients with LVI [9]. In addition, the decrease in hospitalization with decreasing age was found to be consistent with the literature [3]. In our study, LVI was more common, which is consistent with other studies. This is because children are exposed to low-voltage electricity through home accidents.

In this study, 5 patients died due to electrical injuries – 3 developed sudden cardiac arrest, 1 died as a result of subarachnoid hemorrhage due to trauma, and 1 died due to extensive third-degree burns. The number of patients who died was not sufficient to assess the risk factors affecting mortality. However, 3 patients died due to low-voltage exposure, which shows that any voltage exposure can result in death. Khor et al and Shih et al concluded that high-voltage electrical injuries are associated with more acute complications, while any voltage is related to sudden death, cardiac complications, and short- and long-term sequelae [3,9].

As a strength of our study, the increase in white blood cells, neutrophils, urea, ALT, AST, LDH, myoglobin, troponin, and lactate values, and the decrease in HCO3 values, which were not examined in many studies, were found to be significant in terms of hospitalization. Logistic regression analysis showed hospitalization was associated with age, high-voltage injury, and high LDH and myoglobin values (Negelkerle R2=0.568).

In the study by Ahmed et al, increases in CK, troponin, and creatinine were observed in LVI and HVI, but these could not be generalized due to the small number of patients [11]. A previous study observed that CK and myoglobin values were significantly higher at initial presentation, and a significant decrease was observed in these values at 2-, 3-, and 4-day follow-ups [12]. Since this study examined hospitalization of electrical injuries admitted to the ED, we do not have information about the changes in biomarkers during follow-up.

Many studies have examined CK and troponin biomarkers in electrical injuries, and in this study we examined them as well. Although they were found to be significantly associated with hospitalization, they were not significant in logistic regression analysis. However, high myoglobin and LDH values were associated with hospitalization.

In a study investigating the predictive value of LDH together with the abbreviated burn severity index for the prediction of acute kidney injury and mortality in severe burn patients, 194 severe burn patients were examined. The AUC value of LDH for mortality was found to be 0.904, while it was 0.925 for acute kidney injury. They concluded that the combination of LDH and the abbreviated response severity index could better predict mortality and acute kidney injury than the indicators alone [13]. Our study also determined LDH elevation was a factor affecting hospitalization. However, we did not have sufficient samples to evaluate LDH as a mortality risk factor. More studies are needed to understand the effect of LDH as a risk factor in electrical injuries.

In a study examining 162 patients with electrical injuries from 2 centers, serum myoglobin and CK levels at presentation were significantly associated with high-voltage injury, burn area, ICU LOS, ventilator days, number of interventions, mortality, amputation, flap surgery, and sepsis [12]. In a study examining the relationship between electrical injuries and troponin, troponin values were examined in 533 patients with electrical injuries, and a significant relationship was found between MACE (major adverse cardiac event) and troponin. In this study, the relationship between hospitalization and troponin was not examined. The troponin test seems to be a predictive marker of MACE risk and it has been concluded that it should be taken into consideration in high-risk patients [14]. Although troponin and CK levels were not found to be significant factors affecting hospitalization in our study, it is important to use CK and troponin values in patient follow-up and to monitor both cardiac and muscle tissue damage. Our study has limitations because MACE and muscle damage were not examined.

Arrhythmias are the most common cardiac complication of electrical injuries [15]. In our study, ST segment abnormalities were the most common abnormal ECG finding, at 7.3% (n=24), while 1.5% (n=5) had arrythmias. In our study, only the initial ECGs were evaluated and we could not determine if arrhythmias developed during follow-up. Jensen et al described delayed arrhythmias 8–12 hours after electrocution in 3 cases [16]. Studies have not found a relationship between ECG change and mortality, but significant ECG change was found in the high-voltage group [17,18]. In our study, the number of patients who died was too small to perform statistical analysis to investigate the factors affecting mortality. However, a significant difference was found in ECG change between the LVI and HVI groups. ECG change was found to be an important factor affecting hospitalization.

Since this was a single-center, retrospective study, access to patient data was limited. Additionally, due to the insufficient number of fatalities, we were unable to analyze factors influencing mortality. We also lacked information on patients’ medical conditions, which could have affected LOS and recovery time. Another limitation is the lack of detailed information regarding burn injuries. Although burn size is a key factor influencing hospitalization and decisions for discharge, it was not included in our study. Similarly, associated traumatic injuries could have impacted admission rates and LOS, but we did not have sufficient radiological data to assess this factor. Future multicenter prospective studies may provide a more comprehensive understanding of electrical injuries.

Conclusions

According to the study results, patients with low-voltage injuries are discharged earlier. Among the factors affecting the hospitalization of patients, age, ECG changes, YVI and LDH, and myoglobin increase are important parameters. Multicenter prospective studies are needed to better understand hospitalization in electrical injuries.