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Survival in dogs undergoing surgery with thoracic trauma | VETgirl Veterinary Continuing Education Podcasts

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In this VETgirl online veterinary continuing education podcast, we review thoracic trauma in dogs. In the emergency room, we criticalists frequently see patients that have sustained both blunt and penetrating thoracic trauma from a variety of causes, with the most common being vehicular trauma and bite wounds. Thankfully, the prognosis for trauma is generally fair to good, with a reported 90% survival (Hall). However, in patients requiring thoracic surgery, the prognosis is worse. Previous studies have shown a range of short-term mortality rates ranging from 10-44%.

So, Lux et al wanted to further evaluate this in a study called “Perioperative mortality rate and risk factors for death in dogs undergoing surgery for treatment of thoracic trauma: 157 cases (1990–2014).” This was a multi-center retrospective study conducted at multiple veterinary locations, including University of Tennessee, UC Davis, Pet Emergency Center (CA), VCA West LA, University of Georgia, University of Guelph, Kansas State University, Iowa State University, University of Illinois, and Oregon State University (Lux). In this large, multi-institutional study, patient records were reviewed for dogs undergoing surgical intervention for thoracic trauma. The authors looked at risk factors and mortality rates in these patients, and found that up to 85% of patients survive to discharge (which is excellent!). The authors utilized the Animal Trauma Triage (ATT) score as a measure that was previously developed as a way to evaluate animals that have sustained trauma. With this grading system, authors across multiple locations could assess whether the ATT score correlated with outcome. The ATT score was calculated by evaluation of 6 categories (e.g., perfusion, cardiac, respiratory, eye-muscle-integument, skeletal, and neurologic) and assignment of a score from 0 (slight or no injury) to 3 (severe injury) by means of predetermined criteria for each category (rubric available online) was done.

So what did the authors find?

Overall, a total of 157 dogs were included in the study. The following data were collected retrospectively: history, signalment, physical examination findings, clinicopathologic preoperative testing, the type of surgical procedure performed, the incidence of perioperative complications (such as aspiration pneumonia, cardiopulmonary arrest, etc.), the outcome, duration of hospitalization, and follow up, if available. 78% of patients in this study required thoracic surgery. The remainder had other surgical procedures, including abdominal surgery (25% of patients had diaphragmatic hernia repair, intra-abdominal organ repair/removal, body wall repair, etc.) and wound repair/debridement (11%). Bite wounds were the most common cause for thoracic surgery in this study, with 55% of patients in this study having thoracic bite wounds as the inciting cause of trauma.

No preoperative treatment was associated with perioperative death (including the use of oxygen supplementation, endotracheal intubation, antimicrobial use, analgesics, blood products or IV fluids). Also, no measured laboratory values, surgical treatments, or surgical findings were associated with survival to discharge. Multiple traumatic injuries were present in 59% (92/157) of dogs. The most common co-traumas included abdominal trauma in 20%, appendicular trauma in 18%, and trauma to the face or neck in 18%. 55% (86/157) and 34% (53/157) of dogs were classified as having systemic inflammatory response syndrome (SIRS) pre- and postoperatively, respectively. SIRS was not significantly associated with survival in this study, but has been previously reported (Ateca). Postoperative complications occurred in 43% (67/157) of patients and included incisional complications in 20% (32/157), gastrointestinal complications in 12% (19/157), cardiopulmonary arrest in 10% (15/157), cardiac arrhythmias in 7% (11/157), and aspiration pneumonia in 4% (7/157). In this study, 55% of patients had bacterial cultures performed, with the most common isolates being: Streptococcus spp in 11% (10 /87), Staphylococcus spp in 11% (10/87), Pseudomonas spp in 9% (8/87), Enterobacteriaceae in 9% (8/87), and Bacillus spp in 8% (7/87).

Overall, the mortality rate was 14.6% (23/157), which included patients that died (13/23) and patients that were euthanized (10/23). The mean number of days from surgery to death was 2.6 ± 2.9 days (median, 2 days; range, 0 to 13 days). For patients that survived, time from surgery to discharge was a median of 4 days (range, 0.5 to 27 days) postoperatively. Variables found to be associated with survival were sex and development of cardiac arrest. In female dogs, odds of survival to discharge were 6X those of male dogs. In patients that did not experience cardiac arrest, odds of survival to discharge were 102.3X those of patients that experienced cardiac arrest. Three of 7 patients with aspiration pneumonia in the present study died, and this mortality rate was higher than rates previously reported to be associated with aspiration pneumonia (18% to 19%) (Ovbey, Tart). The higher rate of mortality may be due to the fact that patients had preexisting thoracic disease or that owners had financial limitations, contributing to euthanasia. Low case numbers prevented statistical analysis of this variable. Whereas previous studies suggest that thoracic trauma generally carries a poor prognosis, the mortality rate for patients in the present study, in which 78% (123/157) required thoracic surgery, was only 14.6% (23/157).

So, what did we like about this study?  Again, prior reports indicated that mortality rates for patients with penetrating thoracic trauma range from 11-38%, but this study provides a mortality rate for patients requiring surgical intervention of 14.6%. Neither the severity of trauma documented with diagnostic imaging nor findings at the time of surgery were significant predictors of an increased risk of perioperative death for patients with thoracic trauma undergoing surgery, so even dogs with significant trauma can have a good outcome. When in doubt, consider utilizing the ATT score as a guide for intervention. However, limitations of this study were that it was retrospective in nature, and that ATT scores were assigned retrospectively (based on medical records, not clinical evaluation of the patient at the time). Also, the authors didn’t evaluate patients with similar injuries that did not have surgical intervention (e.g., there was no control group). Finally, the study was performed over a period of 24 years; over this huge time space, there are changes not only in the improvements in quality of care, but also in medical technology and medical record collection.

So, what do we take away from this VETgirl podcast?

Don’t give up on your patients with thoracic trauma, even if they require surgical intervention! The prognosis is still excellent, with up to 85% of patients in this study surviving to discharge. Obviously, patients that develop cardiac arrest are significantly less likely to survive to discharge. When in doubt, take the time to calculate the ATT score, as it may be a helpful predictor. In this study, ATT was significantly associated with outcome. Patients with an ATT score <7 had a 5.1X higher odds of survival than patients with an ATT score ≥7. Patients with an ATT score ≥7 developed cardiac arrest in 14% of cases, versus 2% of cases in patients with an ATT score <7. Again, the ATT score was associated with outcome and can be used to guide interventions in these patients, but should not be used as a determinant for euthanasia for individual cases. A higher ATT score likely warrants more diagnostics and/or more aggressive treatment for an individual patient.

References:
1: Hall KE, Holowaychuk MK, Sharp CR, et al. Multicenter prospective evaluation of dogs with trauma. J Am Vet Med Assoc 2014;244(3):300-8.
2. Lux CN, Culp WTN, Mellema MS, et al. Perioperative mortality rate and risk factors for death in dogs undergoing surgery for treatment of thoracic trauma: 157 cases (1990–2014). J Am Vet Med Assoc 2018;252(9):1097-1107.
3. Ateca LB, Drobatz KJ, King LG. Organ dysfunction and mortality risk factors in severe canine bite wound trauma. J Vet Emerg Crit Care 2014;24:705–714.
4. Ovbey DH, Wilson DV, Bednarski RM, et al. Prevalence and risk factors for canine post-anesthetic aspiration pneumonia (1999–2009): a multicenter study. Vet Anaesth Analg 2014;41:127–136.
5. Tart KM, Babski DM, Lee JA. Potential risks, prognostic indicators, and diagnostic and treatment modalities affecting survival in dogs with presumptive aspiration pneumonia: 125 cases (2005–2008). J Vet Emerg Crit Care 2010;20:319–329.

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