Abstract
This study characterized trends in management of canine traumatic brain injury (TBI) among 182 small animal veterinarians grouped as follows: Board-certified specialists at a veterinary teaching hospital (BCS-VTH), Board-certified specialists in private practice (BCS-PP), non-specialists at a teaching hospital (DVM-VTH), and non-specialists in private practice (DVM-PP). The BCS-VTH, BSC-PP, and DVM-VTH groups were more comfortable using the modified Glasgow Coma Scale (MGCS) than the DVM-PP group (P < 0.001, P < 0.001, and P = 0.009, respectively). All respondents chose the following diagnostics most frequently: packed cell volume/total solids (95.6%), blood glucose (96.7%), and blood pressure (95.0%). The DVM-VTH group chose the following more frequently than the DVM-PP group: computed tomography (19.4% versus 4.5%; P = 0.027), venous or arterial blood gas (83.9% versus 46.3%; P < 0.001), electrocardiography (71.0% versus 44.8%; P = 0.018), lactate (87.1% versus 59.7%; P = 0.009), and brief thoracic ultrasound (87.1% versus 62.7%; P = 0.017). BCS-PP chose hypertonic saline more frequently than DVM-PP (94.1% versus 74.6%; P = 0.005). The DVM-PP group chose corticosteroid therapy and anticonvulsant therapy more frequently than BCS-PP (10.4% versus 0.0%; P = 0.019; 73.1% versus 43.1%; P = 0.004, respectively). This study highlights variability in management of canine TBI.
Résumé
Tendances actuelles dans la gestion des traumatismes cérébraux canins : sondage sur Internet. Cette étude a caractérisé les tendances dans la gestion des traumatismes cérébraux canins (TC) parmi 182 médecins vétérinaires pour petits animaux regroupés de la façon suivante : spécialistes agréés par un conseil dans un hôpital d’enseignement vétérinaire (BCS-VTH), spécialistes agréés en pratique privée (BCS-PP), non-spécialistes dans un hôpital d’enseignement vétérinaire (DVM-VTH) et non-spécialistes en pratique privée (DVM-PP). Les BCS-VTH, les BSC-PP et les DVM-VTH étaient plus à l’aise lors de l’utilisation de l’échelle de Glasgow modifiée (MGCS) que les DVM-PP (P < 0,001, P < 0,001 et P = 0,009, respectivement). Tous les répondants ont choisi les diagnostics suivants le plus fréquemment : valeur d’hématocrite/solides totaux (95,6 %), glycémie (96,7 %) et tension artérielle (95,0 %). Le groupe DVM-VTH a choisi les éléments suivants plus fréquemment que le groupe DVM-PP : tomodensitométrie (19,4 % contre 4,5 %; P = 0,027), gaz du sang veineux ou artériel (83,9 % contre 46,3 %; P < 0,001), électrocardiographie (71,0 % contre 44,8 %; P = 0,018), lactate (87,1 % contre 59,7 %; P = 0,009) et une brève échographie thoracique (87,1 % contre 62,7 %; P = 0,017). Le groupe BCS-PP a choisi la solution saline hypertonique plus fréquemment que le groupe DVM-PP (94,1 % contre 74,6 %; P = 0,005). Le groupe DVM-PP a choisi la thérapie corticostéroïde et une thérapie anti-convulsivante plus fréquemment que le groupe BCS-PP (10,4 % contre 0,0 %; P = 0,019; 73,1 % contre 43,1 %; P = 0,004, respectivement). Cette étude souligne la variabilité dans la gestion des TC canins.
(Traduit par Isabelle Vallières)
Introduction
Canine traumatic brain injury (TBI) presents a therapeutic challenge to the veterinary practitioner. Moderate to severe TBI requires prompt recognition and therapeutic intervention to prevent rapid neurologic deterioration or death. Recommendations for the optimal management of human TBI patients are evolving and consensus guidelines for the management of canine TBI patients are lacking. Review articles describing the pathophysiology of canine TBI (1) and summarizing current recommendations for the management of small animal neurologic trauma (2) underscore the complexity of brain injury. As the pathophysiology is better elucidated, an increasing number of diagnostic and therapeutic targets have been identified. The utility of these diagnostics and the efficacy of specific therapies remain controversial, however. For example, veterinary studies that have evaluated the prognostic utility of advanced imaging [magnetic resonance imaging (MRI)] in canine head trauma suggest that there are significant associations between intraparenchymal lesions and prognosis (3). However, the cost, anesthetic risks, and availability of advanced imaging must be measured against its prognostic value. Further, both traditional and novel treatments for TBI continue to be debated and investigated. The human literature provides conflicting results regarding the superiority of hypertonic saline or mannitol for the treatment of intracranial hypertension, for example (4). Moreover, while human and canine head trauma patients appear to be at increased risk for post-traumatic seizures (5,6), the benefit of implementing prophylactic anticonvulsant therapy is unclear (2).
This Internet survey-based study was conducted as a preliminary step towards a larger goal: to initiate the development of formal and more widely available treatment guidelines for canine TBI. Surveys of current clinical practice can provide the foundation for the development of consensus guidelines for case management. In addition to identifying areas of clinical equipoise for further investigation, a thorough understanding of current clinical practice is necessary to identify barriers to implementation of guidelines and is a prerequisite for any study of the improvement of quality of care (7). The primary objective of this study was to characterize the current diagnostic and therapeutic strategies employed in the management of canine traumatic brain injury (TBI). The authors speculated that diagnostic and therapeutic preferences would be heterogeneous among practitioners surveyed.
Materials and methods
An Internet-based survey was used to interview practicing veterinarians regarding their management of canine TBI. The survey was conducted over a 3-month period (June to August 2016). The survey was constructed with the assistance of an Internet-based continuing education platform (VETgirl: Veterinary Continuing Educations Podcasts and Webinars) and distributed through social media as well as by e-mail. E-mail invitations were sent to veterinary professional list server groups [American College of Veterinary Emergency and Critical Care (ACVECC) and American College of Veterinary Internal Medicine (ACVIM) discussion list servers]. There was a total of 182 veterinarian respondents. The survey required that all questions be completed before submission, precluding the inclusion of incomplete surveys in data analysis. Responses from veterinary students and veterinary technicians were not included in final data analysis.
Survey characteristics
The survey contained 24 questions on diagnostic and therapeutic preferences in canine TBI cases. The questions were a combination of multiple-choice questions that permitted a single response, multiple choice questions that allowed for multiple responses, and a small number of open-ended questions. The questionnaire is available on request from the corresponding author. Respondents were divided into 4 categories: Board-certified specialists at a veterinary teaching hospital (BCS-VTH), Board-certified specialists in private practice (BCS-PP), non-specialists affiliated with a teaching hospital (DVM-VTH), and non-specialists in private practice (DVM-PP). The Board-certified specialists were individuals with diplomate status in American College of Emergency and Critical Care, American College of Veterinary Internal Medicine, American College of Veterinary Surgeons, or American College of Veterinary Anesthesia and Analgesia.
Statistical analysis
The survey questions were analyzed as a multinomial random variable when the survey question allowed the respondent to only choose a single response from a list. When respondents could choose multiple responses from a list, the data were analyzed per response category as a binomial random variable. Under the multinomial response paradigm, the multinomial relative frequency distributions of the BCS-VTH, the BCS-PP, the DVM-VTH, and the DVM-PP were compared by the conventional likelihood Chi-squared test when all of the multinomial categories were non-sparsely populated, and by the Pearson Chi-squared exact test when 1 or more of the multinomial cell frequency categories was sparsely populated. Under the binomial response paradigm, the binomial relative frequency distributions of the BCS-VTH, BCS-PP, DVM-VTH, and DVM-PP were compared by the conventional Fishers exact test. For hypothesis testing, a P ≤ 0.05 decision rule was used as the null hypothesis rejection criterion for all between-group comparisons. A commercial statistical analysis program (SAS version 9.4; SAS Institute, Cary, North Carolina, USA) was used to conduct all statistical analyses.
Results
Respondent characteristics
A total of 182 respondents was included in the analysis. Respondents were placed in 1 of 4 categories for analysis: BCS-VTH: 33 respondents; DVM-VTH: 31 respondents; BCS-PP: 51 respondents); and DVM-PP: 67 respondents. The most frequent workplace categories cited were private practice specialty hospital (39.0%), private practice emergency practice (31.9%), and veterinary teaching hospital (35.2%). All respondents selected small animal as at least part of their patient population.
Incidence of canine TBI and preliminary clinical criteria used to further evaluate canine TBI cases
All respondents most frequently indicated that they saw or treated 1 to 5 cases of canine TBI per month (including polytrauma cases suspected to have TBI). The clinical criteria most often selected to further evaluate canine TBI cases included changes in mentation/responsiveness (98.4%), changes in pupil size, symmetry, responsiveness, or other cranial nerve deficits (97.8%), and hypertension/bradycardia (92.9%). Additional criteria, including evidence of external trauma (88.5%), evidence of seizures (86.8%), and changes in posture or ability to ambulate (82.4%), were also frequently chosen. Overall, 73.6% of respondents identified the modified Glasgow Coma Scale (MGCS) as part of the clinical criteria. The BCS-VTH practitioners were more likely to include the MGCS as part of their clinical criteria than were DVM-PP practitioners (P = 0.013). Similarly, BCS-PP practitioners were more likely to include the MGCS than were DVM-PP practitioners (P = 0.004).
Modified Glasgow Coma Scale: Utility of the MGSC and comfort level using the MCGC
Most practitioners indicated that the MGCS was moderately useful (62.6% of respondents). The majority of respondents were either moderately comfortable (37.9%) or very comfortable (39.0%) using the MGCS (Table 1). The DVM-VTH practitioners were more comfortable using the MGCS than were DVM-PP practitioners (P = 0.009). The BCS-VTH and BCS-PP practitioners also indicated they were more comfortable using the MCGS than were DVM-PP practitioners (both P < 0.001).
Table 1.
Responses to the survey question: What is your comfort level using the modified Glasgow Coma Scale (MGCS)?
| Group | Percent (%) of responses within each group | ||
|---|---|---|---|
|
| |||
| Not comfortable | Moderately comfortable | Very comfortable | |
| BCS-VTH | 9.1 | 33.3 | 57.6 |
| BCS-PP | 9.8 | 39.2 | 51.0 |
| DVM-VTH | 22.6 | 32.2 | 45.2 |
| DVM-PP | 40.3 | 32.2 | 17.9 |
BCS-VTH — Board-certified veterinarians working at a veterinary teaching hospital; BCS-PP — Board-certified veterinarians working in private practice; DVM-VTH — non-Board-certified veterinarians working at a veterinary teaching hospital; DVM-PP — non-Board-certified veterinarians working in private practice.
When asked about the frequency with which the MGCS is used in canine TBI patients, 48.4% of DVM-VTH practitioners responded that they used the MGCS in all patients while 23.9% of DVM-PP practitioners responded that they used the MGCS in all patients (P = 0.020). The DVM-PP practitioners were more likely to never use the MGCS (23.9%) compared with the BCS-PP practitioners (5.9%; P = 0.011). There were no significant differences among the responses of Board-certified specialist groups (P > 0.05).
Among all groups, 34.6% of survey respondents indicated that they repeat the MGCS in fewer than 50% of cases. Additional responses were as follows: the MGCS is never repeated at regular intervals (22.0%), the MGCS is repeated at regular intervals in > 50% but not all patients (22.5%), and the MGCS is repeated at regular intervals in all TBI patients (20.9%).
Initial diagnostic testing performed in canine TBI cases
The diagnostic tests most frequently performed on a TBI patient within the first 4 h of admission by all respondents included packed cell volume/total solids (PCV/TS) (95.6%), blood glucose (96.7%), and blood pressure (95.0%) (Table 2). Practitioners at a teaching hospital (BCS-VTH and DVM-VTH) indicated that they use lactate (93.9% versus 68.6%; P = 0.005), electrocardiogram (ECG) (75.8% versus 41.2%; P = 0.003), and brief thoracic ultrasound (81.8% versus 58.8%; P = 0.032) more frequently than did their private practice counterparts (BCS-PP and DVM-PP). When DVM-VTH and DVM-PP groups were compared, DVM-VTH practitioners chose computed tomography (CT) (19.4% versus 4.5%; P = 0.027), venous or arterial blood gas (83.9% versus 46.3%; P < 0.001), ECG (71.0% versus 44.8%; P = 0.018), lactate (87.1% versus 59.7%; P = 0.009), and brief thoracic ultrasound (87.1% versus 62.7%; P = 0.017) more frequently than did their private practice counterparts. Conversely, DVM-PP practitioners more frequently chose complete blood (cell) count (CBC) (70.1% versus 45.2%; P = 0.025), serum chemistry (76.1% versus 41.9%; P = 0.001), and survey radiographs (71.6% versus 35.5%; P = 0.001) as part of their initial diagnostic plan than did DVM-VTH practitioners.
Table 2.
Responses to the survey question: What initial diagnostics do you perform (within 4 hours of admission) on a canine traumatic brain injury patient?
| Diagnostic test | Percent (%) of responses within each group | |||
|---|---|---|---|---|
|
| ||||
| BCS-VTH | BCS-PP | DVM-VTH | DVM-PP | |
| PCV/TS | 100 | 98.0 | 100 | 89.6 |
| Blood glucose | 100 | 98.0 | 93.5 | 95.5 |
| Lactate | 93.9 | 68.6 | 87.1 | 59.7 |
| CBC | 48.5 | 74.5 | 45.2 | 70.1 |
| Serum chemistry | 45.5 | 78.4 | 41.9 | 76.1 |
| Blood pressure | 97.0 | 100 | 93.5 | 91.0 |
| Coagulation testing | 9.1 | 2.0 | 25.8 | 20.9 |
| Pulse oximetry | 81.8 | 80.4 | 67.7 | 73.1 |
| ECG | 75.8 | 41.2 | 71.0 | 44.8 |
| Survey radiographs | 33.3 | 70.6 | 35.5 | 71.6 |
| Brief abdominal ultrasound | 97.0 | 84.3 | 87.1 | 71.6 |
| Brief thoracic ultrasound | 81.8 | 58.8 | 87.1 | 62.7 |
| CT | 18.2 | 3.9 | 19.4 | 4.5 |
| MRI | 0 | 0 | 3.2 | 4.5 |
| EEG | 0 | 0 | 3.2 | 3.0 |
| Measurement of intracranial pressure | 0 | 0 | 0 | 1.5 |
| Venous or arterial blood gas | 81.8 | 60.8 | 83.9 | 46.3 |
| Other | 15.2 | 2.0 | 9.7 | 3.0 |
BCS-VTH — Board-certified veterinarians working at a veterinary teaching hospital; BCS-PP — Board-certified veterinarians working in private practice; DVM-VTH — non-Board-certified veterinarians working at a veterinary teaching hospital; DVM-PP — non-Board-certified veterinarians working in private practice; PCV/TS — packed cell volume and total solids; CBC — complete blood (cell) count; ECG — electrocardiography; CT — computed tomography; MRI — magnetic resonance imaging; EEG — electroencephalography.
Initial therapeutic interventions used in canine TBI cases
The initial therapeutic interventions chosen for TBI are summarized in Table 3. The most frequently selected treatments among all respondents included mannitol (89.0%), hypertonic saline (85.1%), crystalloid fluids (91.2%), elevation of the head (93.4%), oxygen therapy (93.4%), and opioid analgesia (84.6%).
Table 3.
Responses to the survey question: What initial therapeutics do you consider in canine traumatic brain injury cases?
| Therapeutic | Percent (%) of responses within each group | |||
|---|---|---|---|---|
|
| ||||
| BCS-VTH | BCS-PP | DVM-VTH | DVM-PP | |
| Mannitol | 84.8 | 94.1 | 93.5 | 85.1 |
| Hypertonic saline | 87.9 | 94.1 | 90.3 | 74.6 |
| Crystalloid fluid therapy | 84.8 | 96.1 | 96.8 | 88.1 |
| Colloid fluid therapy | 27.3 | 21.6 | 6.5 | 20.9 |
| Elevation of head (incline board) | 97.0 | 88.2 | 93.5 | 95.5 |
| Oxygen therapy | 93.9 | 96.1 | 87.1 | 94.0 |
| Corticosteroid therapy | 3.0 | 0 | 3.2 | 10.4 |
| Non-steroidal anti-inflammatory therapy | 0 | 0 | 3.2 | 7.5 |
| Opioid therapy | 87.9 | 90.2 | 83.9 | 79.1 |
| Anticonvulsant therapy | 54.5 | 47.1 | 58.1 | 73.1 |
| Therapeutic hypothermia | 18.2 | 9.6 | 12.9 | 17.9 |
| Mechanical ventilation | 45.5 | 21.6 | 22.6 | 20.9 |
| Hyperventilation | 9.1 | 9.8 | 0 | 3.0 |
| Antibiotic therapy | 18.2 | 15.7 | 25.8 | 25.4 |
| Insulin therapy | 0 | 7.8 | 3.2 | 3.0 |
| Antioxidant/Free-radical scavenging therapy | 9.1 | 19.6 | 3.2 | 14.9 |
| Other | 15.2 | 3.9 | 6.5 | 1.5 |
BCS-VTH — Board-certified veterinarians working at a veterinary teaching hospital; BCS-PP — Board-certified veterinarians working in private practice; DVM-VTH — non-Board-certified veterinarians working at a veterinary teaching hospital; DVM-PP — non-Board-certified veterinarians working in private practice.
The BCS-PP practitioners were more likely to choose hypertonic saline than were the DVM-PP practitioners; 94.1% BCS-PP practitioners chose hypertonic saline compared with 74.6% DVM-PP practitioners (P = 0.005). While 10.4% of DVM-PP practitioners chose corticosteroids as part of their initial treatment plan, none of the BCS-PP clinicians selected corticosteroid therapy (P = 0.019). Moreover, 73.1% DVM-PP clinicians chose anticonvulsant therapy compared to 47.1% of BCS-PP practitioners (P = 0.004).
Treatment(s) of choice for intracranial hypertension
Hyperosmolar agents were the initial therapy of choice for intracranial hypertension (ICH). Mannitol was chosen by 73.0% of participants and hypertonic saline was chosen by 73.6% of participants. Corticosteroid therapy (0.03%), colloid therapy (0.05%), and decompressive craniectomy (0.02%) were chosen much less frequently (Table 4). According to most respondents, mannitol and hypertonic saline were both available for use at all times (90.7%).
Table 4.
Responses to the survey question: What is your first-line therapy of choice for intracranial hypertension?
| Group | Percent (%) of responses within each group | |||||
|---|---|---|---|---|---|---|
|
| ||||||
| Mannitol | Hypertonic saline | Colloid | Corticosteroids | Decompressive craniectomy | Other | |
| BCS-VTH | 57.6 | 84.8 | 3.0 | 0 | 3.0 | 0 |
| BCS-PP | 68.6 | 72.5 | 3.9 | 0 | 2.0 | 3.9 |
| DVM-VTH | 93.5 | 87.1 | 3.2 | 6.5 | 6.5 | 3.2 |
| DVM-PP | 74.6 | 62.7 | 7.5 | 6.0 | 0 | 6.0 |
BCS-VTH — Board-certified veterinarians working at a veterinary teaching hospital; BCS-PP — Board-certified veterinarians working in private practice; DVM-VTH — non-Board-certified veterinarians working at a veterinary teaching hospital; DVM-PP — non-Board-certified veterinarians working in private practice.
Patient factors appeared to influence the choice of first-line therapy for ICH more so than specific characteristics of hypertonic saline versus mannitol. The patient’s volume status and/or hemodynamic stability appeared to influence initial therapeutic choices most often (82.4%). Comorbidities were also frequently considered when choosing a therapy (75.8%). DVM-VTH practitioners were more likely to indicate that “results of advanced imaging” guided first-line therapy for ICH than did their DVM-PP counterparts (16.1% versus 1.5%; P = 0.012).
The physical properties of mannitol and hypertonic saline as hyperosmolar agents, their effects on inflammation, and their ability to modulate oxidative injury were chosen with a similar frequency (33.5%, 27.4%, and 26.9% of all respondents, respectively). The rheological effects of hypertonic saline and mannitol were considered by 25.2% of all respondents.
Improved mentation or responsiveness was the most important clinical criterion used to guide treatment for TBI, chosen with a frequency of 99.4%. The following clinical criteria were also frequently considered: resolution of the hemodynamic changes associated with intracranial hypertension (90.6%) and improvement of pupil size, symmetry, and reactivity (93.4%). Control of clinical seizures was chosen by 76.3% of respondents, while improvement of the MGCS score was chosen by 64.2% of all respondents. Improvement of ventilation parameters, normolactatemia, and normoglycemia were chosen by 47.8%, 42.3%, and 41.7%, respectively. Achieving a normal EEG was rarely chosen to guide continued therapy (0.04% of all respondents; Table 5).
Table 5.
Responses to the survey question: What clinical criteria do you use to guide therapy in canine traumatic brain injury?
| Clinical criterion | Percent (%) of responses within each group | |||
|---|---|---|---|---|
|
| ||||
| BCS-VTH | BCS-PP | DVM-VTH | DVM-PP | |
| Improved mentation/responsiveness | 97.0 | 100 | 100 | 100 |
| Improved MGCS score | 75.8 | 72.5 | 61.3 | 53.7 |
| Normotension and normal heart rate | 87.9 | 92.2 | 90.3 | 91.0 |
| Normal pupil size, symmetry, and reactivity | 78.8 | 96.1 | 93.5 | 98.5 |
| Eupnea | 72.7 | 80.4 | 67.7 | 80.6 |
| Normocapnia | 69.7 | 37.3 | 54.8 | 41.6 |
| Normoglycemia | 51.5 | 39.2 | 32.3 | 43.3 |
| Normolactatemia | 57.6 | 35.3 | 51.6 | 35.8 |
| Control of clinical seizures | 72.7 | 70.6 | 71.0 | 85.1 |
| Normal EEG | 0 | 2.0 | 3.2 | 7.5 |
| Other | 3.0 | 2.0 | 0 | 1.5 |
BCS-VTH — Board-certified veterinarians working at a veterinary teaching hospital; BCS-PP — Board-certified veterinarians working in private practice; DVM-VTH — non-Board-certified veterinarians working at a veterinary teaching hospital; DVM-PP — non-Board-certified veterinarians working in private practice; MGCS — modified Glasgow Coma Scale score; EEG — electroencephalography.
Pathophysiology of secondary brain injury
Most practitioners were either very familiar (42.3%) or somewhat familiar (43.4%) with the pathophysiology of secondary brain injury. Board-certified specialists were more likely to be very familiar with secondary brain injury than non-Board-certified specialists of either group: 63.6% BCS-VTH practitioners and 66.7% BCS-PP practitioners indicated they were very familiar with secondary brain injury, whereas 38.7% DVM-VTH practitioners and 14.9% DVM-PP practitioners indicated that they were very familiar with secondary brain injury. The DVM-VTH practitioners were more likely to indicate that they were very familiar with secondary brain injury than were the DVM-PP practitioners (DVM-VTH 38.7% versus DVM-PP 14.9%; P = 0.017).
Availability and accessibility of canine TBI treatment guidelines and comfort level treating canine TBI
According to most respondents, guidelines for canine TBI are somewhat clear (68.1%) and moderately available and accessible (67.6%). Among all groups, 54.4% of respondents felt very comfortable treating TBI. A substantial number of respondents indicated they were moderately comfortable (40.7%), and a lesser number indicated they were not comfortable treating TBI (4.9%). Board-certified specialists of both groups were more likely to indicate they were very comfortable treating TBI than were non-specialists of either of the non-specialist groups (79.7% BCS versus 32.6% DVM). The DVM-VTH practitioners were more likely to indicate that they were very comfortable treating canine TBI than were their DVM-PP counterparts (48.4% versus 25.4%; P = 0.047).
Discussion
This survey identified some conserved practices implemented by most practitioners, as well as specific differences in diagnostic and therapeutic approaches to canine TBI. While all respondents appear to rely heavily on the results of a complete neurologic examination, Board-certified specialists were more comfortable with the use of the MGCS and used it more frequently than did other groups. The explanations for these discrepancies were not addressed in this survey. A future survey could be constructed to more specifically interrogate clinicians about their familiarity with and exposure to the MGCS at varying levels of education and training. The Glasgow Coma Scale (GCS) has traditionally been considered the gold standard in human medicine for providing an objective neurologic assessment of the level of consciousness in human patients with severe brain injury (8). Initial as well as serial GCS scores can be used to guide therapy, compare treatment efficacies, and determine prognosis in human patients sustaining brain injury (8–10). Similar to the GCS in human comatose patients, the MGCS serves as an objective neurologic assessment that can be performed at the time of admission and repeated at intervals during hospitalization. Previous veterinary studies that have evaluated prognostic indicators in head trauma have found the MGCS to be a useful indicator of survival in the TBI patient population (11–14). Given its prognostic utility, concerted efforts to teach and to reinforce consistent use of the MGCS in canine TBI cases seem warranted.
Initial diagnostic tests performed in TBI cases help to guide therapeutic interventions and to provide prognostic information. Based on retrospective veterinary studies, neither blood pressure nor blood glucose at the time of admission is predictive of outcome in TBI, although hyperglycemia may indicate the severity of brain injury (12). While hyperglycemia has been associated with poor outcome in humans with TBI in clinical studies, some studies suggest that episodic hyperglycemia may improve cerebral metabolism and mitigate secondary brain injury (15). The effects of glucose control on neurologic outcome or survival in canine TBI patients have yet to be determined. Moreover, indicators of hypoperfusion or metabolic dysfunction, including increased lactate, decreased blood pH, increased base deficit, and decreased bicarbonate, have been shown to be predictive of non-survival in dogs with traumatic brain injury (12). The non-uniform pattern of diagnostic tests chosen by practitioners at a teaching hospital versus those in private practice in this survey suggests a lack of clarity regarding the utility — or necessity-of specific diagnostics. The disparity seen in responses should prompt the construction of a more formal diagnostic algorithm that can be applied to canine TBI cases.
Neuroimaging in the acute canine TBI patient was infrequently chosen as a diagnostic tool among all respondents in this survey. Neuroimaging allows for the identification of structural changes to brain and skull and may be used to guide therapy in the head trauma patient. In humans, CT remains the imaging modality of choice for head trauma within the first 24 h of injury, as it allows for rapid assessment for hemorrhage and fractures (16). As the sequelae of secondary brain injury develop, however, MRI becomes the superior imaging modality for detecting changes to the brain parenchyma and becomes the imaging modality of choice 24 h or more after the injury (16,17). A study evaluating MRI in dogs with head trauma demonstrated associations between MRI findings and prognosis (3). In veterinary patients, however, CT and MRI often require heavy sedation or anesthesia to obtain images of diagnostic quality, so in addition to cost, the risks and benefits of advanced imaging to the individual patient must be carefully considered (14). A follow-up survey could be designed to identify the reasons that clinicians infrequently pursue advanced imaging in the context of canine TBI (i.e., perceived value or necessity of information obtained, financial costs, anesthetic risks, accessibility, other reasons). Specific recommendations regarding neuroimaging in the canine TBI patient and the optimum time at which to perform imaging would be of value in the construction of treatment guidelines.
Therapeutic options for canine TBI are numerous and often controversial. Corticosteroid therapy was chosen by fewer than 5% of respondents; however, 10.4% of non-specialists in private practice indicated that they use corticosteroids in the management of TBI. A randomized control trial evaluating corticosteroid administration in human head trauma (CRASH study) found no clinical benefit to corticosteroid therapy and in fact showed increased early mortality rates in patients who received corticosteroids (18). Prior to this study, corticosteroids were more commonly used in the treatment of TBI. Although there are no studies that evaluate the use of corticosteroids in canine TBI, given the evidence for harm in the human population, the authors believe it is prudent to recommend against the use of corticosteroids in the treatment of TBI.
Anticonvulsant therapy was chosen by approximately 50% of respondents, which suggests a lack of consensus regarding the necessity of seizure prophylaxis. In humans, seizure prophylaxis is recommended in severe TBI patients (5,19,20). Studies evaluating EEG findings in human patients with moderate to severe TBI have shown that post-traumatic seizures occur in approximately 20% of the patient population; most of these seizures are non-convulsive and detected on EEG alone (19). Similarly, a study evaluating the incidence of post-traumatic seizures in dogs with head trauma revealed a greater incidence of seizures in trauma patients than in the general population (6). While prompt treatment of overt seizure activity in canine TBI patients is unlikely to be contested, the necessity for seizure prophylaxis remains controversial (1). Further, the anticonvulsant of choice for seizure prophylaxis, as well as the diagnostic modalities necessary to detect non-convulsive seizures, warrant further investigation before specific recommendations can be made.
While hyperosmolar agents have antioxidant properties, the addition of other antioxidants for the explicit purpose of scavenging reactive oxygen species was infrequently chosen as an initial therapeutic intervention for TBI. Studies evaluating the effect of specific antioxidants on outcome in human and veterinary TBI cases are lacking. It has been postulated that the mitigation of oxidative stress may be an important therapeutic target in TBI (21,22).
Intracranial hypertension is a severe complication of TBI and exacerbates cerebral ischemia and secondary brain injury (1,23). While surgical decompression via craniectomy may provide an acute reduction in intracranial pressure, intracranial hypertension is much more commonly treated with hyperosmolar therapies that target the reduction of interstitial edema within the brain (1,23). Mannitol and hypertonic saline are the 2 most widely used hyperosmolar agents in both human and veterinary medicine (1,4,23,24). In this survey, respondents chose mannitol and hypertonic saline as their first-line treatment of choice for intracranial hypertension with very similar frequencies. Beyond their hyperosmolar properties, the 2 therapies have varying effects on rheology, cerebral vasospasm, cardiac output, intravascular volume, and inflammation (4,24,25). Individual studies and meta-analyses in human medicine have sought to compare mannitol to hypertonic saline to determine whether there is a superior hyperosmolar therapy for the management of intracranial hypertension (4,26). While some studies suggest that hypertonic saline may more effectively reduce intracranial pressure compared with mannitol (1,4,26,27), these studies do not demonstrate that hypertonic saline improves survival or neurological signs relative to mannitol (27). Current guidelines for the treatment of severe TBI in humans do not recommend one hyperosmolar solution over the other, citing that there is insufficient evidence to do so (28). The relative benefits of hypertonic saline versus mannitol have not been investigated in naturally occurring TBI in the dog.
This study has several limitations. While the survey was distributed across 2 list servers and a veterinary continuing education social media platform for a 3-month period, the total number of respondents was small. The sample size was sufficient for the identification of statistically significant differences between groups; however, a larger number of participants would have increased the power to detect smaller differences. Furthermore, there was a limited number of questions that required clinicians to make diagnostic or therapeutic choices without case-specific information. As with any survey-based study, the construction of the questionnaire may have influenced survey results.
In conclusion, the results of this study suggest that significant heterogeneity exists in the assessment and treatment of canine TBI in the veterinary community. In particular, there is variation in the use of the MGCS, monitoring of oxygenation, ventilation and perfusion, and treatment with corticosteroids and hyperosmolar therapies, despite existing evidence for or against these interventions. This study highlights the need for evidence-based consensus guidelines for the treatment of TBI and identifies clinically relevant gaps in understanding that warrant further research.
Acknowledgments
The authors thank James Patrie for performing the statistical analyses, Cape Cod Veterinary Specialists for their financial support of the project, Dr. Louisa Rahilly for critical review of the survey, Dr. Shana O’Marra for critical review of the manuscript, and Dr. Justine Lee with VETgirl: Veterinary Continuing Education Podcasts and Webinars for critical review of the survey and assistance with survey distribution. The authors also thank those who responded to the survey questions. CVJ
Footnotes
Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (hbroughton@cvma-acmv.org) for additional copies or permission to use this material elsewhere.
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