Evaluation of vehicular trauma in dogs: 239 cases (January–December 2001)

Elizabeth M. Streeter Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Elizabeth A. Rozanski Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Armelle de Laforcade-Buress Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Lisa M. Freeman Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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John E. Rush Department of Clinical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

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Abstract

Objective—To describe a population of dogs with vehicular trauma and to determine whether age, type and severity of injury, or preexisting disease were associated with outcome.

Design—Retrospective case series.

Animals—239 dogs evaluated at a university referral hospital after vehicular trauma over a 12-month period.

Procedures—Patient characteristics, including age, outcome, animal trauma triage (ATT) score, treatments performed, hospital stay, cost, and preexisting disease, were recorded from medical records of dogs that had vehicular trauma. Dogs were assigned to a young, middle-aged, or geriatric age group. Categoric and continuous variables were compared between survivors and nonsurvivors to identify possible associations.

Results—239 dogs (126 males and 113 females) were evaluated following vehicular trauma during 2001: young (n = 149), middle-aged (68), and geriatric (22). The median ATT score was 3 (range, 0 to 15). Sixteen dogs had preexisting disease. Hospital stay ranged from < 1 to 28 days (median, 3 days). Cost ranged from $77 to $10,636 (median, $853). Two hundred six dogs were discharged. Twenty-six dogs were euthanatized, and 7 died. Dogs that died or were euthanatized had significantly higher ATT scores. The ATT score also was associated with a significantly higher cost of care. Dogs with multiple injuries had significantly higher ATT scores, had increased cost of care, and were significantly more likely to die or be euthanatized.

Conclusions and Clinical Relevance—Increased injury severity in dogs was associated with increased mortality rates and higher cost of treatment.

Abstract

Objective—To describe a population of dogs with vehicular trauma and to determine whether age, type and severity of injury, or preexisting disease were associated with outcome.

Design—Retrospective case series.

Animals—239 dogs evaluated at a university referral hospital after vehicular trauma over a 12-month period.

Procedures—Patient characteristics, including age, outcome, animal trauma triage (ATT) score, treatments performed, hospital stay, cost, and preexisting disease, were recorded from medical records of dogs that had vehicular trauma. Dogs were assigned to a young, middle-aged, or geriatric age group. Categoric and continuous variables were compared between survivors and nonsurvivors to identify possible associations.

Results—239 dogs (126 males and 113 females) were evaluated following vehicular trauma during 2001: young (n = 149), middle-aged (68), and geriatric (22). The median ATT score was 3 (range, 0 to 15). Sixteen dogs had preexisting disease. Hospital stay ranged from < 1 to 28 days (median, 3 days). Cost ranged from $77 to $10,636 (median, $853). Two hundred six dogs were discharged. Twenty-six dogs were euthanatized, and 7 died. Dogs that died or were euthanatized had significantly higher ATT scores. The ATT score also was associated with a significantly higher cost of care. Dogs with multiple injuries had significantly higher ATT scores, had increased cost of care, and were significantly more likely to die or be euthanatized.

Conclusions and Clinical Relevance—Increased injury severity in dogs was associated with increased mortality rates and higher cost of treatment.

Traumatic injury is known to have a major impact on the health of people, in terms of patient mortality rates and health-care use. Accidents were the fifth most common cause of death in people in the year 2001.1 Research in people has extensively evaluated individuals sustaining traumatic injury, and these studies have resulted in identification of risk factors and outcome predictors. In particular, age and injury severity influence outcome in human trauma patients; older or more severely injured patients have a worse outcome.2–6 Studies7–9 of people with traumatic injury have led to the development of many scoring schemes and outcome predictors. Data gathered from injury severity scores have been used to guide appropriate treatments and prioritize health care in the human field.10–12

Trauma is a common problem in dogs and cats. Clinical observations suggest that factors affecting injured animals, such as age, severity of injury, coexisting disease, and requirement of advanced care, may also impact outcome in dogs and cats. The use of scoring strategies to predict outcome in critically ill dogs and cats has been previously described.13–18 For instance, 1 study13 documented an increased risk with advancing age for perianesthetic morbidity and death in dogs. Also, age was implicated as an outcome predictor in dogs undergoing surgery.14 To our knowledge, no such associations with survival have been evaluated in dogs following vehicular trauma.

Two large studies19,20 that have evaluated dogs and cats with trauma were performed more than 25 years ago. One study19 evaluated trauma populations in dogs and cats and documented that approximately 13% of hospital admissions were for treatment of traumatic injuries.19 Overall mortality rates as high as 36% were described, but no relationship to specific injuries or injury severity was identified.19 In comparison to the extensive and complex injury severity scoring schemes available in human medicine, there are fewer scoring schemes available for use in veterinary medicine. Shores18 developed the small animal coma scale for use in assessing animals with neurologic injury. This modification of the Glasgow coma scale has been shown to predict outcome of dogs with brain injury.21 Kirby16 has suggested a scoring scheme rating traumatic injuries into 4 categories: mild, moderate, severe, and catastrophic. The ATT score was developed to rank severity of injury after trauma in dogs and cats.15 This scoring scheme uses 6 categories and ranks abnormalities within each category from 0 to 3. The summation of this scoring scheme gives a numeric rank, the higher scores indicating increased injury severity. The ATT scores were higher in animals that did not survive trauma, compared with that of survivors.15 King et al17 have proposed a model for prediction of survival in critically ill dogs. This study, which included dogs with traumatic injury, developed an equation (the survival prediction index) that gives an estimate of the probability of survival.

Identification of variables influencing survival may be beneficial in determining appropriate treatments and treatment goals. In human emergency medicine, scoring schemes can be used to determine need for referral to advanced trauma centers and identify people who are at high risk for complications and death.12 Similar information may be useful for the veterinary trauma population.

The objectives of the study reported here were to describe a population of dogs with vehicular trauma and to determine whether age, type and severity of injury (eg, type of injury, single vs multiple injury, and ATT score), or preexisting disease were associated with survival. We also evaluated whether any of these variables were associated with cost of care and length of hospital stay and whether these variables differed among age groups.

Materials and Methods

Criteria for selection of cases—Dogs were selected for study inclusion by use of an in-house data registry. All dogs admitted during a 12-month period (January 1, 2001 to December 31, 2001) to the Foster Hospital for Small Animals at Cummings School of Veterinary Medicine, Tufts University after vehicular trauma (hit by car) were eligible for study inclusion. The Foster Hospital serves as a primary emergency facility and as a regional referral hospital. Dogs were excluded if there was limited information available in the medical record, if the owners declined hospitalization or treatment when recommended, or if vehicular trauma could not be established as the cause of the dog's injuries.

Procedures—Medical records were reviewed, and data were collected by use of a standardized data collection sheet. Variables such as date of birth, weight, initial injuries and physical examination findings, ATT score, outcome, cost of care, and length of hospital stay were recorded. Dogs were assigned to 1 of 3 age groups on the basis of categories reflective of body size established in a previous study.13 Three age categories were used (young, middle-aged, and geriatric) on the basis of age and breed. Weight was used to group dogs into toy to small, medium, large, or giant breed categories, and adjustments were made to account for the differing life expectancies of dogs. To calculate the ATT score, a score of 0 to 3 was given to each of the following categories: perfusion, cardiac, respiratory, eye-muscle-integument, skeletal, and neurologic.15 Predetermined criteria were used to assign the score ranging from 0 (slight or no injury) to 3 (severe injury).15 Outcome was classified as survivor (defined as survival until discharge) or nonsurvivor. Dogs classified as nonsurvivors were further classified as those that were euthanatized and those that died despite ongoing medical care. Cost of care was calculated for all dogs on the basis of financial records of all costs incurred during the hospital stay. The presence and number of preexisting illnesses were also tabulated, with a preexisting illness defined as the presence of any major chronic disease requiring ongoing medical management at the time of the vehicular trauma (eg, cardiac disease, diabetes mellitus, cancer, inflammatory bowel disease, or osteoarthritis), on the basis of historic information contained in the medical record or as reported by the owner.

Statistical analysis—Data were analyzed by use of standard statistical software.a Data are reported as median (range). Data distributions were evaluated by use of the Kolmogorov-Smirnov 1-sample test. The ATT score, cost of care, and length of hospital stay were not normally distributed and so were logarithmically transformed prior to analysis. Categoric data were analyzed by use of a χ2 test (ie, comparing the frequency of dogs surviving between those with single or multiple injury, injury type, or the presence of preexisting disease or comparing the presence of preexisting disease or survival between age groups). Continuous data were compared between 2 groups by use of either independent t tests (ie, ATT score, cost, and length of hospital stay compared between dogs with single or multiple injuries; ATT score compared between survivors and nonsurvivors; or ATT score, cost, or length of hospital stay compared between dogs with or without preexisting disease) and between more than 2 groups by use of an ANOVA with Tukey post hoc analysis (ie, comparing ATT score, cost, and length of hospital stay between the 3 age groups). Multivariable analysis also was performed to determine variables with significant relationships with survival (eg, age, type and severity of injury, and preexisting disease). Pearson correlation was used to compare 2 categoric variables (ie, ATT score and length of hospital stay or cost of care). Values of P < 0.05 were considered significant.

Results

Two hundred thirty-nine dogs met inclusion criteria and had medical records available for data collection. This included 126 male dogs (75 castrated and 51 sexually intact) and 113 female dogs (86 spayed and 27 sexually intact). Dogs were classified as young (n = 149), middle-aged (68), and geriatric (22). The median ATT score was 3 (range, 0 to 15; Figure 1). The most frequent type of injury included long bone fractures, pulmonary contusion, soft tissue injury, pelvic fractures, and hemoabdomen (Figure 2).

Figure 1—
Figure 1—

Distribution of ATT scores for 239 dogs with vehicular trauma. The ATT score ranges from 0 to a highest possible score of 18.

Citation: Journal of the American Veterinary Medical Association 235, 4; 10.2460/javma.235.4.405

Figure 2—
Figure 2—

Distribution of injuries in 239 dogs with vehicular trauma.

Citation: Journal of the American Veterinary Medical Association 235, 4; 10.2460/javma.235.4.405

Of 239 dogs, 169 (71%) had multiple injuries. Sixteen dogs had preexisting illness, including heart disease (n = 9), endocrine disease (5), renal disease (1), and reproductive tract disease (1). Median cost of care was $853 (range, $77 to $10,636), and median length of hospital stay was 3 days (range, < 1 to 28 days). Of 239 dogs, 206 (86%) were discharged from the hospital. Thirty-three dogs were nonsurvivors with 26 dogs (11/239; 11%) euthanatized and 7 dogs (7/239; 3%) that died as a result of their injuries.

The ATT score was significantly (P < 0.001) related to outcome. Nonsurvivors had significantly higher ATT scores (median, 6; range, 2 to 15), compared with survivors (median, 2; range, 0 to 11). The ATT score was also significantly (r = 0.23; P = 0.001) correlated with cost of care. There was no correlation between ATT score and length of hospital stay (r = 0.02; P = 0.76). There was no difference in survival rate between the 3 age groups (P = 0.19). Also, there was no significant difference between the age groups and ATT score (P = 0.88), length of hospital stay (P = 0.92), or cost of care (P = 0.26). Dogs in the geriatric age group were significantly (P < 0.001) more likely to have preexisting disease, compared with dogs in the young or middle-aged groups, but preexisting disease was not associated with survival (P = 0.62), length of hospital stay (P = 0.15), or cost of care (P = 0.13). Dogs with multiple injuries had significantly (P < 0.001) higher ATT scores, significantly (P = 0.001) higher cost of care, and a significantly (P = 0.004) lower percentage of survivors, compared with those with a single injury. Dogs with cardiac arrhythmias (P < 0.001), hemoabdomen (P = 0.004), body wall hernias (P = 0.008), severe soft tissue injury (P = 0.04), or vertebral fractures (P < 0.001) were significantly more likely to die or be euthanatized than dogs without these injuries. After multivariable analysis, only ATT score remained significantly (P < 0.001) associated with survival.

Discussion

The median ATT score was significantly higher in dogs that died or were euthanatized than in dogs that survived. Also, the number of injuries was higher in dogs that did not survive, compared with that of survivors. Dogs that had multiple injuries had higher ATT scores than those with single body systems affected. High ATT scores seen in dogs with multiple injuries are not surprising as the score does take into account the number of body systems affected. This is reflected by the fact that only ATT score remained significant on multivariable analysis. Increased mortality rate in dogs with severe injuries also reflects trends seen in injured people.22–29 In human medicine, injury severity scores are often used to determine which patients may need advanced trauma centers with advanced treatment capabilities.10–12 In veterinary medicine, future research may elucidate whether injury severity scores, such as the ATT score, could also be useful to determine which animals are at high risk for death and require more intensive treatments and care.

Injury severity, as assessed by the ATT score, was significantly correlated with higher cost of care, although the relationship was weak (r = 0.23; P = 0.001). This observation seems reasonable, as dogs with severe injuries may require multiple interventions and treatments. Additional treatments, medications, or multiple surgical procedures add to costs in patient care. These variables are important to consider when evaluating the trauma patient, as prediction of resource use and cost may influence owner treatment decisions.

Although older people are at increased risk for death, sepsis, and other complications of trauma, survival rate was not significantly different between the 3 age groups in the current study.2–6,26 However, it must be mentioned that this was a relatively small study and included only 22 geriatric dogs. Further investigation in the relationship between age and survival in veterinary trauma is needed. In human medicine, epidemiologic studies include numbers in excess of 80,000 patients.30 These numbers are difficult to obtain in the veterinary population; however, additional evaluation with larger numbers of dogs may identify a relationship between age and outcome in trauma.

Results of human studies also indicate that older people with traumatic injuries have a higher prevalence of concurrent chronic illness. These illnesses, such as cardiopulmonary disease, have been associated with poorer outcomes.31,32 Although there was a higher prevalence of preexisting disease in the geriatric age group in our study, dogs with preexisting disease were not more likely to die or be euthanatized. Again, this finding may be hampered by a small sample size. In future investigations, additional numbers of geriatric animals may identify a relationship between the presence of preexisting conditions and survival in trauma. However, dogs and cats differ from humans in the etiology and severity of illnesses. This factor may also be responsible for the lack of significance seen between the presence of concurrent illness and survival.

There are other limitations to the current study. Studies conducted in different populations of dogs with vehicular trauma may yield different results, and results from dogs cannot be directly transferred to cats without further study. Also, costs at other hospitals may differ from ours, so dogs presenting to a different hospital may have had different costs. Other experimental design issues of the current study also influenced the results. For example, there is debate on the optimal method to assess survival in dogs and cats. In the current study, survival was defined as survival to discharge, but this is an important issue to consider in species in which euthanasia is an option. Finally, the potential for confounding factors that could affect results (eg, treatments) also is an important limitation of the current study. It would be valuable in future larger studies to evaluate the potential effects of the many other factors that could affect results in dogs and cats with trauma.

In this population of dogs with vehicular trauma, dogs that did not survive to discharge had a higher ATT score and higher cost of care. Future studies to validate the ATT score as a part of patient assessment and to assess prognosis are warranted. Additional studies also may provide justification for use of the ATT score in the assessment of health-care use in dogs and cats with traumatic injury.

ABBREVIATION

ATT

Animal trauma triage

a.

Systat, version 11.0, SPSS Inc, Chicago, Ill.

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