Survival Rate of High-Rise Syndrome Cases Using Animal Trauma Triage Score in Cats

Abstract

Objective To assess the data of high-rise syndrome (HRS) cases and determine the relationship between Animal Trauma Triage Score (ATTS), height, injury profile, and survival rate of patients.

Study Design Retrospective study evaluating cats with HRS within a 4-year period.

Results A logistic regression analysis which included height, ground type, and ATTS variables was performed to predict survival rate of patients. Only ATTS was significant among these variables (p < 0.001) and each point increase in ATTS increased the nonsurvival by 0.46 times (95% confidence interval [CI]: 0.347–0.624). The receiver operating curve indicates that ATTS is good at predicting mortality (area under the curve: 0.857; 95% CI: 0.788–0.926; p < 0.001).

Conclusion The height of the fall, injury type, or ground type do not seem to be accurate in estimating the survival rate in HRS patients. Established scoring systems such as ATTS should be used to determine survival rates in future HRS studies.

Keywords

cats - fall - high-rise syndrome - Animal Trauma Triage Score - survival

Introduction

High-rise syndrome (HRS) is used to describe lesions in cats falling from the second or higher floor of a building. This term is used to represent three findings: hard palate fracture, pneumothorax and epistaxis seen after the fall.[1] [2]

This syndrome has no sex predisposition and is more common in cats between 2 and 3 years of age.[2] Previous reports have investigated the relationship between the height of falling and the resulting lesions. Most studies have reported that the number and severity of injuries increase up to a certain height and then remain relatively constant.[2] [3] [4] According to these reports, the frequency and severity of injuries mostly increase between the second and sixth floors and then stay relatively constant. Another study proposed a direct relationship between injuries and height, with no plateau after a certain point.[5] [6] There have also been reports suggesting the use of scoring systems for injuries to evaluate the potential severity of an HRS patient.[5] [7] Very few studies utilized the Animal Trauma Triage Score (ATTS) previously in HRS.[8] [9]

The capability of ATTS in predicting survival in HRS has not been investigated in a large sample size. This study retrospectively evaluates the clinical findings and outcomes of a large number of HRS cases. The aim of this study was to determine whether the ATTS system is effective in predicting survival in HRS.

Materials and Methods

The medical records of cats with HRS that were brought to the Veterinary Teaching Hospital of Ondokuz Mayıs University from 2017 to 2020 were retrospectively evaluated. Each cat brought to our hospital during this time was reviewed and considered for this study regardless of its sex, age, breed, and weight. After evaluation, those with complete medical records were included in the study. Records were considered complete if they included the patient's signalment, patient history (sex, height of the fall, ground type), physical examination results, and neurological or orthopaedic findings (if applicable). Cats were excluded from the study if the initial chest radiogram or data on treatment and outcome were missing.

Lesions were grouped as follows: orthopaedic lesions (extremity and pelvic injuries), head and neck (skull, maxillofacial areas, mandibular and hard palate), vertebral column (cervical, thoracal, lumbar, and sacral), thoracic traumas (pneumothorax, pleural effusion, diaphragmatic hernia, etc.), and soft tissue injuries (urinary bladder rupture, abdominal hernia, etc.).

Lesions requiring the patient to be euthanized, such as spinal trauma without deep pain perception, were not included among the causes of mortality in this study. Each patient was evaluated individually and given an ATTS. The parameters used for scoring are shown in [Supplementary Table S1] (available in the online version).

Statistical Methods

The normal distribution of the collected data was determined using the Q–Q plot and Shapiro–Wilk tests. Normal and nonnormal distributed data were respectively shown as mean ± standard deviation and median (range). Categorical variable data were shown as frequency and percentage. The Kruskal–Wallis test was used to compare the number of cases in each season. The independent t-test or Fisher's exact test, as appropriate, was applied for statistical analysis of landing surface, ATTS, and ground between nonsurviving and surviving cats. Spearman's rank correlation was used to evaluate the relationship between height and ATTS. A binary logistic regression model was used to predict the survival rating of the ATTS. The receiver operating characteristic (ROC) was used for the graphical demonstration, and the area under the curve (AUC) was shown to express performance. A binary logistic regression model was used to predict injuries in cats by fall height, body weight, and surface. Ordinal logistic regression analysis was used to determine the relationship between ATTS with age, sex, and body weight. Commercially available software (SPSS, version 26.0, IBM) was used for each analysis, and a p <0.05 criterion was adopted in every statistical evaluation.

Results

The data of this study consisted of HRS cases brought to a single center within 4 years (2017–2020). A total of 425 cats were diagnosed with HRS. Of these cases, 373 patients had complete medical records and met the inclusion criteria of this study. The average age was 10 months (range: 2–168). Domestic shorthair, 332/373 (89%), was the most common breed in this study.

The sex distribution was 217 male (58.2%) and 156 female cats (41.8%). Only 16 (4.3%) of the cats reported in this study were neutered. The average body weight was 2.7 kg (range: 0.5–7). The average falling height in this study was the fourth floor (range: 3–13) ([Fig. 1]). According to patient histories, 45/373 (12.1%) of the cats fell on soft surfaces, while 328/373 (87.9%) fell on hard surfaces. The relationship between vertebral column and thoracic traumas had a higher percentage for cats that fell on hard surfaces, and this was found to be significant (p < 0.001). The relationship between orthopaedic lesions and ground type was not significant (p > 0.05). The relationship between head and neck lesions and ground type was not significant (p > 0.05). Soft tissue injuries were mostly seen in cats that fell on soft surfaces (p < 0.05) ([Fig. 2]). HRS cases were most common during the summer months (54.7 ± 7.54; p = 0.023).

Fig. 1 Distribution of case numbers in relation to floors for all cases.

Fig. 2 The percentages of every injury type in relation to fallen ground types for all cases.

All lesions encountered in this study were summarized into five groups: orthopaedic lesions, head and neck, vertebral column, thoracic traumas, and soft tissue lesions. The distribution of these lesions in relation to floors is shown in [Fig. 3]. Nineteen cats were completely healthy and free of pain despite the fall. The relationship between the five categories of injuries and the floor fallen from was not statistically significant (p > 0.05).

Fig. 3 The distribution of each injury type by floor. Despite the decline of skeletal lesions after the fifth floor and the incline of thoracic traumas after the sixth floor were not statistically significant for all cases.

Thoracic and orthopaedic lesions were the most common types of injury in HRS cases. Pneumothorax, 60/155 (38.71%), was the most observed thoracic lesion in cats, followed by diaphragmatic hernia, 50/155 (32.25%), and pleural effusion, 45/155 (29.03%). According to the results, thoracic traumas were uncommon below the fourth floor, and the number increased after the sixth floor. Despite this finding, statistical analyses showed no significance between thorax injuries and height (p > 0.05).

The soft tissue lesions seen in this study were skin wounds, 16/21 (76.19%), and subcutaneous hematomas, 5/21 (23.81%). Nineteen cats presented with no discernible pathology but mild-to-moderate pain. The odds of any given pathology occurring during a fall is 7.98 times higher for cats falling on hard surface instead of soft surface (95% confidence interval [CI]: 2.661–23.945; p < 0.001). There was no statistical significance between body weight and injuries of cats included in this study (odds ratio [OR]: 1.256; 95% CI: 0.839–1.879; p = 0.268). The number of patients without injuries was greater in cats fallen from the third floor. This finding was found to be statistically significant. There was a 16.96 times greater chance of having an injury at the fourth floor compared to the third (95% CI: 2.086–137.994; p = 0.008). The odds of cats having an injury when falling from the seventh and above floors were 5.1 times greater than the third (95% CI: 1.007–25.917; p = 0.049).

Orthopaedic lesions of the extremities were most commonly seen on the fifth floor and below. Rib fractures were seen in only four patients. Multiple long bone fractures were found in 30/373 (8%) cases.

Traumatic lesions affecting the head and neck were seen in 69/373 (18.5%) cases, with most of them falling from the fifth floor and below. Vertebral fractures were seen in 26/373 (7%) cases. Thoracic spine injuries 16/26 (61.54%) were more common than lumbar spine injuries 10/26 (38.46%), but most thoracic segment injuries were at the thoracolumbar junction, 9/16 (56.25%). A large percentage of cats, 254/373 (68.1%), in this study had none of the three lesions (hard palate fracture, pneumothorax/hemothorax, epistaxis) associated with the traditional definition of HRS.

The score distribution by floor by summarized in [Fig. 4]. The median score was linearly increased after fifth floor. A positive correlation was seen between ATTS and height (r = 0.244; p < 0.001).

Fig. 4 Distribution of each ATTS by floors for all cases (mean ± SD). ATTS, Animal Trauma Triage Score; SD, standard deviation.

The survival rate in this study was 354/373 (94.9%). The statistical relationship between survival and landing surface, ATTS, and fallen height is shown in [Table 1]. The lowest survival rate was observed on the sixth floor, but it was not statistically significant (p = 0.152). The highest mortality rate was found in cats with a score of 7 and above, 13/21 (61.9%) . There was no statistically significant relationship between lesion type and survival. The most common causes of death were vertebral and thoracic trauma in cats ([Fig. 5]).

Table 1 Statistical analysis of landing surface, ATTS, and floor in cats with HRS

Variable		Survivors (n = 352)	Nonsurvivors (n = 21)	p-Value
Landing surface	Hard	45 (12.8%)	0 (0%)	0.091
	Soft	307 (87.2%)	21 (5.6%)
ATTS		3.93 ± 2.17	7.09 ± 1.86	<0.001
Floors		4.6 ± 1.37	5 ± 1.24	0.152

Abbreviations: ATTS, Animal Trauma Triage Score; HRS, high-rise syndrome.

Note: Values are mean ± SD, or n (%).

Fig. 5 Distribution of the five main lesions in survivor and nonsurvivor cats.

Logistic regression analysis was performed to determine the survival rate of patients. ATTS, height, and ground type were included in the model as variables. Among these, only ATTS was significant (p < 0.001). A point increase in ATTS increases the risk of nonsurvival by 0.46 times (95% CI: 0.347–0.624). ROC curve was shown graphically to assess the role of the ATTS in determining nonsurvival ([Fig. 6]). The ROC curve shows that ATTS is effective in predicting mortality in HRS (AUC: 0.857; 95% CI: 0.788–0.926; p < 0.001). When the cut-off was set to >5, sensitivity and specificity were determined to be 15 and 98%, and when this value was set to 10, sensitivity and specificity were 67 and 95%.

Fig. 6 Receiver operating characteristic curves constructed by using ATTS results. Note that the area under the curve (AUC) of ATTS is closer to the upper left part which indicates greater accuracy in results. ATTS, Animal Trauma Triage Score.

There is no statistical significance in the relationship between age (OR: 1.011; 95% CI: 0.999–1.023; p = 0.071) and body weight (OR: 1.019; 95% CI: 0.873–1.190; p = 0.812) on ATTS. Male cats had 0.687 times (95% CI: 0.478–0.988; p = 0.042) higher ATTS than female cats.

Discussion

HRS occurs most frequently in urban areas, as larger buildings are more common in these residential areas.[4] [7] Cats twist their bodies and brace their legs to “right” themselves during a fall, but falls from the fifth floor or more impede the function of the vestibular system so cats relax their muscles, causing their limbs to spread and show a “parachute-like effect.”[1] Thus, falls from below the fifth floor tend to injure the limbs, while any fall above that height tends to cause damage to the spine, thorax, and head.[6] [10] Terminal velocity is used to describe the maximum amount of speed an object can reach during a fall. Previous reports have shown that the seventh floor is the height at which falling cats reach terminal velocity at the bottom. This means that the speed and the impact generated upon falling remain the same on any floor above seven.[2] [10] Interestingly, some results of previous studies, as well as the present study, are contrary to these facts. While the physics of a cat falling from a height is well known and can be explained in simple terms, we feel that some of the concepts of HRS are fluid and worthy of discussion. The term “floor” is not constant. The same floor windows of two different buildings may not be of the same height, and some buildings have vastly different ceiling heights than others. The obstacles encountered during a fall may also decrease or even stop the velocity of the descent and even injure the cat during a fall.[7] [11] Moreover, although previous studies have stated that the ground is important to the clinical outcome, they mostly focused on the height of the fall.[7] Solid surfaces do not absorb any force, but soft ground does; therefore, serious injuries are more likely to happen on hard-surface surfaces. We believe the results of this study emphasizes the importance of the ground, since injuries were significantly more common in cats falling onto hard surfaces.

It is quite difficult to find a correlation between the height of the fall and the trauma profile. Another reason for the inconsistencies between height and injury may be faulty record keeping. During the care of an emergency patient, data may be mishandled, especially in understaffed facilities. We believe that the discrepancies in theory and practice may be caused by these reasons. However, some patients did not show any injuries and a significant number of these fell from the third floor; the odds of having injuries drastically increased in just one floor increment (fourth) in this study. Unsurprisingly, the potential to accrue injuries increases with height. It is also worth mentioning that most of the patients that showed no pathology fell on soft ground.

In our study, orthopaedic injuries were common below the fifth floor and decreased linearly as height increased. Most orthopaedic injury patterns were similar to the previous literature,[7] but it may be important to note that hard palate fractures and thorax pathologies were common in multiple fracture cases. This is most likely due to the failing support of the fractured limbs during the time of impact. Most long bone fracture cases fell from the fifth floor or below and landed on hard surfaces. At these heights, the vestibular system is active, and the limbs are extended to brace the fall.[1] [12] A previous report suggested that open fractures occur due to the type of trauma rather than the anatomical structure of a specific bone.[13]

Rib fractures had a low incidence in this study. A previous report found that the median age of cats for rib fractures was 3 years.[14] As most of the cats in this study were up to 1 year old, the elasticity of the ribs could have prevented fractures. Most diaphragmatic hernia cases fell on hard surfaces, and all fell from the sixth floor or higher. Arguably, cases that are at terminal velocity impacting the ground have a higher risk of diaphragmatic herniation. As hard surface ground does not absorb the impact, it is directly transferred to the body, and an increase in abdominal pressure damages the diaphragm.[7] [15]

A relatively small number of patients had soft tissue injuries, and most of them did not require surgery. Notable exceptions were two abdominal hernias, one bladder rupture, and radial nerve paralysis. Only a small number of patients had skin lacerations or abrasions. This is not surprising, as falling and impacting the ground at high speed will most likely cause blunt trauma.[16] It is safe to assume that the wounds were caused by sharp objects on the path, such as railings or corner edges. According to our results, the ground also greatly affected the patient's outcome. Thoracic trauma and vertebral column lesions, which are the two most important causes of mortality in this study, were mostly observed in cats that fell on hard surface grounds.

Interestingly, more than two-thirds (68.1%) of the cats included in the study did not have any of the three “classical” conditions of HRS,[1] [2] which are pneumothorax, epistaxis, and hard palate fracture. A previous paper broadened these conditions to “face, thorax, and extremities,” but it still did not explain the remaining lesions (e.g., lumbar fracture, bladder rupture, pelvic fractures).[4] We suggest that the description of HRS should be broadened because the traditional description does not cover some injuries that falling might cause.[17] Thoracic, abdominal, orthopaedic, neurologic, palatal, dental, and soft tissue (skin, muscle) injuries were all reported in cases falling from a building. A number of studies express the need to expand the definition and trauma profile of HRS since almost any type of injury is possible when falling.[11]

The high number of cats in this study could also be due to a lack of government regulations on pet ownership. Proofing a household pet from a fall (e.g., window meshes, balcony nets) is not mandatory, and there is no punishment for negligence. This could also be a reason for the high number of patients in this study.

A previous scoring system only took lesions into account without considering their severity or the patient's outcome.[7] Since the same condition has different possible prognoses in different patients, the survival rate and prognosis of a patient should be assessed using a trauma triage scoring system instead of individual injuries. The ATTS system is comprehensive and accurate for predicting prognosis, but it requires all existing patient data when assigning a score.[9] [11] Most previous retrospective studies did not utilize a scoring system in HRS for cats.[8] According to logistic regression analysis, ATTS provides accurate results when determining the patient's survival in HRS cases. However, there was a slight decrease in our AUC value compared to the previous study.[8] The change in results could be attributed to the increased number of cases in this study. It can be speculated that a greater sample size might have yielded more different results.

The role of mating and hunting behaviors in HRS has been reported in many studies.[2] [7] [11] Behavior in cats is affected by age, sex, and body weight. However, in this study, body weight and age were not influential in determining ATTS.

The residential zones in our region do not have many buildings longer than seven floors, and most have concrete parking lots; thus, the distribution of cases between soft surface and hard surface and different heights is uneven. As this is a retrospective clinical study, the conditions were not the same for each patient. The results could be easily influenced by obstacles hit during a fall or the time passed after the initial trauma when the patient was brought to the clinic. We believe that ATTS has reliable results in trauma patients, but this study only examined HRS patients, which have relatively low mortality rates. This may have influenced the logistical regression reliability of ATTS, as the patient dispersion is one-sided (e.g., no motor vehicle accidents, no gunshot wounds).

This study concludes that there is no discernible connection between survival and height, or height and type of injury. Statistically, injury types did not relate to animal survival in this study which supports the initial hypothesis of ATT being a more reliable predictor in determining mortality rates. We believe using a quantitative system such as ATT in future studies may allow for more comprehensive meta-analyses which can provide more accurate results for survival in HRS.

Conflict of Interest

None declared.

Authors' Contribution

Conception of study: K.S.İ., T.Ö., A.Ö., C.Y., H.Ö.N., K.S. Study design: K.S.İ., T.Ö., A.Ö., C.Y., H.Ö.N., K.S. Acquisition of data: K.S.İ., T.Ö., B.D.Ö.E., M.G., E.B.K. Data analysis and interpretation: K.S.İ.

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Publication History

Received: 21 November 2023

Accepted: 17 July 2024

Article published online:
01 August 2024