Characteristics of black bear‐related trauma: A retrospective observational study

Abstract

Aim

Bear‐related trauma is a significant concern in Japan. This study identified trauma patterns, outcomes, and therapeutic approaches for bear‐related injuries treated.

Methods

This retrospective observational study used medical records from Akita University Hospital, focusing on patients with bear‐related trauma in 2023. Demographic data, injury details, treatment procedures, and outcomes were extracted.

Results

The study included 20 patients (median age: 74.5 years, 65% males). Most injuries occurred in human habitats, mainly in autumn, with the face being the most affected area (90%). Three patients required emergency transfusions and tracheal intubation. Emergency surgery was performed in 52.6% of patients, and 42.1% were admitted to the intensive care unit. All patients survived with a median hospital stay of 17 days. However, 15.8% of patients had significant sequelae, such as blindness. Despite prophylactic antibiotics, wound infections occurred in 21.1% of patients, particularly in deep wounds that were not adequately washed under general anesthesia.

Conclusions

Bear‐related trauma often results in severe upper‐body injuries that require prompt medical intervention. These findings highlight the need for improved preventive measures and strategies for initial treatment and long‐term care.

This study investigated trauma patterns, outcomes, and treatments for 20 patients with bear‐related injuries at Akita University Hospital in 2023. The findings provide insights into the need for care strategies and information to help address the impact of bear encounters on communities.

INTRODUCTION

Bear‐related trauma has become a worldwide problem, ¹ and Japan is no exception. In recent years, bear habitats have been expanding due to a decrease in the number of hunters and the frequency of human activities in forests. ² Bears are widespread in Japan, with brown bears in Hokkaido and black bears in Honshu and Shikoku. ² According to the Environment Ministry of the Japanese government, 209 bear‐related human injuries were reported in 2023, 70 of which occurred in Akita Prefecture in northern Japan. ³ This is the highest in Japan, indicating that the bear threat is significant. The species of bear living in Akita Prefecture is the black bear (Ursus thibetanus japonicus). Traumatic injuries caused by bears can be severe and require long‐term medical care. ⁴ Furthermore, the social impact of bears cannot be ignored, such as residents feeling insecure in their daily lives and restricting outdoor activities. However, there have been limited in‐depth studies on the specific patterns of bear trauma and optimal treatment. Due to the diversity of bear trauma and the complexity of treatment, consistent treatment guidelines have not been established. Existing reports are scattered and originate from a limited area, ⁴ , ⁵ , ⁶ indicating the need for more data on bear‐related injuries. Identifying specific patterns of bear trauma will enable appropriate clinical and social responses.

This study aimed to describe bear‐related trauma treated at a tertiary‐care hospital in Akita Prefecture, determining trauma patterns, outcomes, and therapeutic approaches associated with these incidents.

METHODS

This retrospective observational study was conducted using medical records from Akita University Hospital. It focused on patients who sustained bear‐related injuries in 2023. This study was approved by the Ethics Committee of Akita University Hospital (approval number: 3081) and conducted in accordance with the ethical guidelines for medical and health research involving human subjects and the Declaration of Helsinki.

Patient demographics, incident circumstances, transportation and hospitalization details, injury assessment, emergency department procedures, details of wound infection, operative treatment, intensive care unit (ICU) treatment, and clinical outcomes were collected. Wound infection was defined as physical signs with effusion or drainage within 30 days post‐suturing. Prehospital data were obtained from emergency medical service records. Demographic, physiological, operative management, resuscitation, and outcome data were extracted from medical records. Data are expressed as median values and interquartile ranges (IQR). Given the descriptive nature of this study, statistical analysis was not performed.

RESULTS

Patient demographics and injury characteristics

This study enrolled 20 patients with a median age of 74.5 years, of which 65% were male (Table 1); however, one patient was transferred to another hospital after initial treatment, thus follow‐up data were unavailable. Injuries occurred from May to November, with a peak in October (35.0%, Figure 1A). There was no specific trend in the time of day for injuries (Figure 1B). The most common injury sites were the face (90.0%), upper extremities (70.0%), and head (60.0%; Figure 2). Severe head and facial damage were also observed, including facial bone fractures (n = 9), eyeball rupture (n = 3), and skull fracture with intracranial hemorrhage (n = 1). The median injury severity score (ISS) was 9, suggesting that most injuries did not meet the definition of major trauma.

TABLE 1.

Baseline characteristics, treatment details, and clinical outcomes.

Baseline characteristics	n = 20
Age, median (years)	74.5 (69.0–81.0)
Male	13 (65.0%)
Injury location type
Human habitat	15 (75.0%)
Mountain forest	5 (25.0%)
Transport type
Ambulance	10 (50.0%)
Doctor car	5 (25.0%)
Doctor helicopter	3 (15.0%)
Transferred from another hospital	2 (10.0%)
Injury severity score	9 (4.0–13.0)
Information in emergency department	n = 20
Emergency transfusion	3 (15.0%)
Tracheal intubation	3 (15.0%)
Hospitalization disposition	18 (90.0%)
Information post‐emergency department	n = 19
Operation
Emergency	10 (52.6%)
Elective	9 (47.4%)
ICU admission	8 (42.1%)
APACHE II on admission	10 (8.0–12.5)
SOFA on admission	1 (0–1.5)
ICU treatment
Transfusion	4 (50.0%)
Mechanical ventilation	2 (25.0%)
Vasopressor	1 (12.5%)
ICU length of stay	2 (2.0–5.5)
Prophylactic antibiotics	19 (100%)
Wound infection	4 (21.1%)
Unilateral blindness	3 (15.8%)
Hospital length of stay	17 (6.0–22.0)
Hospital death	0 (0%)

Note: Data are expressed as medians (interquartile ranges) for continuous variables and numbers (%) for categorical variables.

Abbreviations: APACHE, acute physiology and chronic health evaluation; ICU, Intensive care unit; SOFA, sequential organ failure assessment.

FIGURE 1.

Distribution of bear‐related trauma by month and time of day. Distribution of the month of injury by the bear (A) and time of incidence (B).

FIGURE 2.

Distribution of injury sites in patients with bear‐related trauma. The percentages of patients with injuries at each site were calculated (n = 20). This figure highlights the high prevalence of facial and upper extremity injuries in the patient population.

Treatment and outcomes

Three patients presented with hemorrhagic shock and required emergency transfusion at the emergency department (Table 1). Tracheal intubation for airway protection was performed for three patients due to oral hemorrhage (n = 2) and cervical airway injury (n = 1). Emergency surgery under general anesthesia was required for 11 patients, and all underwent washout debridement; tracheostomy and vitrectomy were performed for three patients each. Nine patients underwent subsequent elective surgery: fracture repair, free‐skin valve anastomosis, facial nerve anastomosis, and salivary leak closure. Eight patients were admitted to the ICU, and life support treatments, such as blood transfusions, mechanical ventilation, and vasopressors were used. All patients were discharged alive, with a median hospital stay of 17 days. Three patients (15.8%) became blind because of unilateral eye rupture.

Prophylactic antibiotics, including ceftriaxone, cefazolin, amikacin, and beta‐lactamase inhibitors were used as single agents or in combination. Beta‐lactamase inhibitors such as sulbactam/ampicillin and tazobactam/piperacillin were administered prophylactically to 11 patients. Amikacin was preferred for open fractures, whereas ceftriaxone and metronidazole were the combination of choice for skull fractures. The median duration of antibiotic prophylaxis was 7 days. In addition, tetanus prophylaxis was administered to all, and the standard procedure typically consisted of tetanus toxoid and 250 units of human tetanus immunoglobulin. Four of the 19 patients had wound infections. The sites of wound infection were the face, postoperative clavicle open fracture, and upper and lower extremities. There were 16 patients with deep wounds that reached muscles and organs, of which 1 of 11 (9.1%) was infected when the wound was washed under general anesthesia, and 2 of 5 (40.0%) were infected when the wound was washed under local anesthesia. Three shallow wounds were cleaned under local anesthesia, and one of them became infected. The median saline volume used for washing was 2250 mL (IQR: 1500–2500) under local anesthesia and 6000 mL (IQR: 4375–8000) under general anesthesia. The causative organisms were identified in 25% of the infections, and Serratia marcescens and Enterococcus faecalis were detected in the infected wounds. The incidence of wound infections was similar between patients treated with prophylactic antibiotics without β‐lactamase inhibitors (2/9, 22.2%) and those treated with antibiotics containing β‐lactamase inhibitors (2/11, 18.2%). The median number of days of antibiotic treatment was 13 (IQR: 6–16.5).

DISCUSSION

In this study, bear‐related trauma often occurred in human habitats in the autumn. Upper‐body injuries were common and required emergency surgery under general anesthesia. Some patients required intubation and blood transfusions for hemorrhagic shock. Despite prophylaxis, wound infections occurred in 21.1%. All survived; however, 15.8% had significant sequelae, such as blindness. Bear‐related trauma has substantial acute and post‐acute consequences.

Japanese black bears begin hibernation in late November to early December and wake up in mid‐March to early May. ⁷ There were no bear‐related trauma incidents during the hibernation period. Consistent with previous reports, our study observed a peak in bear‐related traumas around October. ⁸ In this study, injury occurrence was observed during both the day and evening. Although bears are considered diurnal, they are known to approach human habitats at night in response to food‐seeking behavior. ⁹ Notably, most injuries occur in human habitats rather than in mountainous forests. Increased bear appearances in human settlements stem from the expanding foraging ranges into human areas, ⁹ especially in autumn when mountain food is scarce. Focusing on “urban bears” that appear in human habitats is important. If more bear‐related trauma occurs in the spring and summer phases than in previous years, it is necessary to prepare for even more in the autumn.

It has been reported that the face is the most commonly injured part of the body due to bear‐related trauma, followed by the upper extremities, ⁸ , ¹⁰ , ¹¹ and a similar trend was observed in the current study. The upper‐body injury results from bears often attacking from a standing position, targeting the head and neck, while upper extremities are injured in defense. ¹² Consistent with previous studies, 15% of patients experienced hemorrhagic shock, and some required tracheal intubation or tracheostomy for airway management. ¹⁰ , ¹³ , ¹⁴ Bear‐related trauma is not a major trauma in the ISS anatomic evaluation, but attention should be paid to physiological abnormalities due to trauma in the head and neck region, which is rich in blood flow and involves the airway. The severity scores at ICU admission were not high and there were no hospital deaths; therefore, effective initial treatment may avoid a fatality. The face also hosts critical sensory organs, requiring multidisciplinary care. Thus, early transport to advanced facilities for team‐based care is vital.

Bear trauma is considered to be highly contaminated, with 20%–44% ⁴ , ¹⁰ , ¹⁵ of patients reported to have wound infections. In the current study, 21.1% of patients had wound infections, but they were likely less common in wounds that reached the muscles and organs when the wounds were washed under general anesthesia. Thus, in deep wounds, washing with definite sedation and analgesia is necessary.

This study's strengths include detailed descriptions of bear‐related trauma and findings applied beyond intrahospital care. Limitations involve internal validity issues due to non‐standardized treatments across departments and solely on acute phase injuries, potentially omitting long‐term physical and psychological effects. External validity was limited by the small dataset from a single tertiary‐care hospital, introducing selection bias toward severe injuries and geographic bias, restricting generalizability to areas with different bear behaviors and medical infrastructures.

In conclusion, this study provides insights into black bear‐related trauma in high‐incidence areas, emphasizing increased awareness of risks in human habitats, particularly in autumn. Prompt medical intervention, including emergency surgery, airway management, and treatment of hemorrhagic shock, are crucial.

FUNDING INFORMATION

This study did not receive any specific grants from funding agencies in the public, commercial, or nonprofit sectors.

CONFLICT OF INTEREST STATEMENT

The authors declare that they have no competing interests.

ETHICS STATEMENT

Approval of the research protocol: The Ethics Committee of Akita University Hospital approved this retrospective study (approval number: 3081).

Informed consent: The need for informed consent was waived because of the observational nature of the study and the requirement for no treatment beyond daily clinical practice (Ministry of Education, Culture, Sports, Science and Technology, and Ministry of Health, Labor and Welfare, Japan; Ethical Guidelines for Medical and Health Research Involving Human Subjects).

Registry and the registration no. of the study/trial: N/A.

Animal studies: N/A.

Tsuchida H, Satoh K, Hirasawa N, Okuyama M, Nakae H. Characteristics of black bear‐related trauma: A retrospective observational study. Acute Med Surg. 2024;11:e70009. 10.1002/ams2.70009

DATA AVAILABILITY STATEMENT

The data supporting the findings of this study are available from the corresponding author, KS, upon reasonable request.