Introduction
Brachycephalic breeds have surged in popularity despite the worsening quality of life and reduced life expectancy from hereditary conformational issues.1 Brachycephalic conformation has been linked to several significant disease processes, including brachycephalic obstructive airway syndrome and gastrointestinal dysfunction, which can affect their daily life and are assumed to be linked to increased adverse events in hospital including aspiration pneumonia and regurgitation.2–4 Variable anatomy and severity of brachycephalic index between individuals and between breeds predispose to disease.
There are several reasons for veterinarians to induce emesis in patients, including recent ingestion of some toxins and/or foreign body (FB). Contraindications for emesis induction may include ingestion of caustic substances, severe clinical signs of intoxication, ingestion of sharp objects, laryngeal disease, or loss of consciousness.5
Various medications or irritating substances have been used for emesis induction in dogs, including but not limited to tranexamic acid,6 ropinirole eye drops,7 washing soda crystals,8 hydrogen peroxide,9 and dish soap. The use of apomorphine (APO) for emesis is common and effective,5,9 with Zersen et al10 reporting a 94% emesis success rate with APO when administered IV or subconjunctivally. Associated complications from emesis induction, including vomiting and regurgitation, were considered mild and self-limiting.9,10 In addition to vomiting and regurgitation, other structural or functional issues identified in dogs, such as upper gastrointestinal dysmotility or incompetence, pyloric outflow obstruction, laryngeal disease, and reduced mentation, can lead to or cause aspiration pneumonia.3
To the authors’ knowledge, there are no studies evaluating whether adverse effects of emesis induction can be associated with facial conformation. This study aimed to identify and quantify the type and number of adverse events associated with induction of emesis in a heterogenous population of dogs that have ingested a toxin, FB, or both. In addition, the study aimed to evaluate any association between adverse events and facial conformation. The first null hypothesis was that dogs with brachycephalic conformation would have similar rates of adverse events with emesis induction when compared to mesocephalic and dolichocephalic dog breeds. The second null hypothesis was that the reason for induction of emesis would not be associated with risks of adverse events, regardless of patient skull conformation.
Methods
Electronic medical records between the dates of October 23, 2018, and April 11, 2022, from 1 university hospital and 1 private veterinary hospital were searched for dogs having emesis induced. Inclusion criteria included dogs of any age, those presenting for FB or toxin ingestion/exposure for which the attending clinician determined that emesis induction was indicated, and the use of only APO for induction of emesis. Exclusion criteria included incomplete medical records, being unable to determine facial conformation of mixed-breed dogs from the medical record and available photos, if the patient was lost to follow-up, the presence of comorbidities associated with increased risks of aspiration including previous laryngeal surgery and known esophageal motility disorder, and if any other emesis agent was administered by the owner or referring veterinarian prior to presentation to the study hospitals.
Data extracted from medical records included patient signalment, medical history, route of emesis induction, indication for emesis (toxin ingestion, FB ingestion, or both), the use of reversal/antagonist drug administration postemesis, as well as whether the emesis was successful. Cases were critically evaluated to determine whether there was any adverse event suspected or hospitalization occurred due to the emesis itself. Patient outcome was defined as survival to discharge, euthanasia, or death from cardiopulmonary arrest. Data from both institutions were collected using an electronic data capture system (REDCap).11
Patients were categorized on the basis of conformation, with pure-breed dogs categorized as brachycephalic, mesocephalic, or dolichocephalic. Mesocephalic breeds are those whose length and width of the cranium is equal. Dolichocephalic breeds are those with a breadth < 75% of the length of the skull. Brachycephalic breeds have a muzzle length less than one-third of the skull length and include the following breeds: French Bulldog, Boxer, Affenpinscher, English/British Bulldog, American Bulldog, Boston Terrier, Pug, Pekingese, Lhasa Apso, Bull Mastiff, Cavalier King Charles Spaniel, Brussels Griffon, Dogue de Bordeaux, Japanese Chin, Tibetan Spaniel, Staffordshire Terrier, Shar-Pei, and Chihuahua.1 If a breed was reported in the medical record as a mixed breed, each dog was categorized on the basis of which breed was most prevalent and any facial photos were reviewed to confirm the categorization. For example, a “Jug” would be within brachycephalic mixed and “Spoodle” would be with the mesocephalic/dolichocephalic mixed.
Adverse events were defined as aspiration, acute airway obstruction, regurgitation, recurrent vomiting, or esophageal obstruction. An aspiration event was defined by the suspicion of aspiration of gastric contents during emesis induction on the basis of clinical signs such as coughing, tachypnea, dyspnea, or hypoxemia noted following emesis. Acute airway obstruction was defined as either partial or complete obstruction of the larynx and caudal oropharynx during emesis. Clinical signs supporting this included choking, cyanosis, hypoventilation, and/or collapse, which resolved following suctioning or swabbing of the oral cavity. Regurgitation was defined by the observation of passive production of gastric contents and/or food or water commencing within the first 48 hours after emesis induction. Recurrent vomiting was defined as continued vomiting (> 2 episodes within 12 hours) following discharge of the patient from hospital and starting up to 48 hours after emesis induction. Esophageal obstruction was defined as partial or complete obstruction of the esophagus by food or FB based on radiographic or esophagoscopy confirmation within 48 hours of the induction of emesis.
Statistical analysis
Data were identified as parametric or nonparametric on the basis of visual evaluation of histograms and calculations of skewness and kurtosis. Descriptive statistics for continuous data were reported as count and either mean and range or median and IQR, depending on normality of the data distribution. Categorical data were reported as proportion (percentage).
Patients were grouped into facial conformational categories (brachycephalic, mesocephalic, or dolichocephalic), age categories (juvenile [< 1 year] or adult [≥ 1 year]), and reason for emesis categories (toxin ingestion, FB ingestion, or combination of FB and toxin ingestion). Associations between the frequency of adverse events and patient categories, admission to hospital, presence of signs of toxicity at presentation, route of APO administration, and type of antiemetic used were assessed using the Pearson χ2 and Fisher exact tests. Risk analysis was performed for variables with any significant cross tab analysis. A P value of < .05 was considered significant. Data were analyzed using a commercial spreadsheet for statistical analysis (Excel 2016; Microsoft Corp) and SPSS Statistics (version 24; IBM Corp).
Results
Cases
A total of 1,814 dogs met the inclusion criteria for this study. A total of 374 (20.6%) brachycephalic, 1,236 (68.1%) mesocephalic, and 178 (9.8%) dolichocephalic dogs were represented. There were 26 cases in which the patient’s facial conformation was unable to be determined (1.4%), leaving 1,788 patients included for statistical analysis. There were 548 (30.2%) female desexed, 244 (13.5%) female entire, and 7 (0.4%) female dogs of unknown reproductive status. Of the male dogs, there were 650 (35.8%) desexed, 362 (20.0%) entire, and 2 (0.1%) of unknown reproductive status. There was a single case (0.1%) in which the patient’s sex was not reported.
The median age was 2 years (IQR, 0.5 to 5.0 years), with a range from 0.5 to 19 years. Of the 1,814 patients, 524 (28.8%) were categorized as juvenile (< 1 year of age) and 1,271 (70.1%) as adult. Nineteen patients had no age recorded.
Indications for emesis
The majority of dogs had emesis induced due to toxin ingestion (1,360 [75.00%]), with FB ingestion reported in 420 (23.20%) dogs and both toxin and FB ingestion in 34 (1.90%) dogs. Of the group having ingested foreign bodies, 91 (20.0%) were deemed to have ingested organic material, 331 (72.90%) inorganic, 28 (6.20%) both organic and inorganic, and in 4 (0.90%) cases this unable to be determined from the clinical history assessed.
Apomorphine was administered via the conjunctival route in 799 (44.00%) dogs, 731 (40.30%) via the oral mucosa, 75 (4.13%) SC, 27 (1.49%) IV, and 15 (0.83%) intranasally. The route of APO administration was not recorded in 156 (8.60%) dogs, and 11 (0.61%) were administered APO via other routes. Additional doses of APO were administered in 86 (4.70%) dogs. The most common antiemetics used were metoclopramide (1,322 [72.90%]), via removal of conjunctival APO (293 [16.2%]), maropitant (189 [10.40%]), and ondansetron (7 [0.40%]). No antiemetic was reported for 47 (2.60%) dogs, 2 (0.10%) dogs were given a different antiemetic, and there were 178 (9.80%) cases in which no antiemetic was used. More than 1 antiemetic option was recorded for 250 dogs.
Complications
Complications were reported in 11 of 1,788 (0.60%) patients (Supplementary Table S1). Three (0.17%) patients had regurgitation postemesis, and 8 (0.44%) had recurrent vomiting. For the 3 patients with regurgitation, 2 were mesocephalic and 1 was dolichocephalic. Three brachycephalic and 5 mesocephalic dogs had recurrent vomiting. No patients were reported to have both regurgitation and recurrent vomiting.
Eighty-seven (6.2%) dogs had clinical signs of toxicity noted at the time of presentation of a total of 1,394 dogs presenting for toxin alone or a combination of toxin and FB. Of dogs with signs of intoxication, 55 (63.2%) were admitted to hospital. A total of 241 (17.3%) dogs without signs of intoxication at presentation were admitted to hospital. Out of the 420 dogs presenting for FB ingestion without toxin ingestion, 21 (5%) were admitted to hospital.
When evaluating the association of various patient factors with the reported complications of regurgitation and repeated vomiting, only 2 factors were found to be significant. The presence of clinical signs of toxicity in dogs with emesis induced was significantly associated with regurgitation (P < .001). The presence of regurgitation was significantly associated with admission to hospital (P = .001). Facial conformation was not associated with either reported complication (P = .502 for regurgitation and P = .562 for repeated vomiting).
When comparing brachycephalic dogs to nonbrachycephalic dogs, there is a significant difference in the indication for emesis induction (2-sided Fisher exact test, P = .001), with brachycephalic dogs having a 1.6 times greater odds of having emesis induced due to toxin ingestion compared to FB ingestion (OR, 1.66; 95% CI, 1.202 to 2.171). When investigating the categories of FB ingested, there was a significant difference between brachycephalic dogs and nonbrachycephalic dogs (χ2 value, 19.310; P = .001), but when the category of “Both” was removed from analysis, no significant difference was identified (2-sided Fisher exact test, P = .609).
Brachycephalic dogs with emesis induced for toxin ingestion or FB ingestion did not have different rates of complications when compared to nonbrachycephalic dogs. No significant difference was found in the rate of repeated vomiting between brachycephalic dogs and nonbrachycephalic dogs (2-sided Fisher exact test, P = .375). Similarly, brachycephalic dogs did not have a significantly different rate of regurgitation when compared to nonbrachycephalic dogs (2-sided Fisher exact test, P = 1.00).
Discussion
This was the first study to evaluate the risk of inducing emesis in brachycephalic and nonbrachycephalic breeds. Different degrees of risk for complications have been found between brachycephalic dogs and nonbrachycephalic ones, particularly associated with anesthesia and the postoperative period.12–14 Gruenheid et al15 reported that, compared to nonbrachycephalic dogs, brachycephalic breeds were 1.57 times and 4.33 times more likely to develop intra-anesthetic and postanesthetic complications, respectively. In the current study, complications with induction of emesis were rare and did not cause death. In addition, no significant overall difference was found in rates of complications regardless of facial conformation, suggesting that the anecdotal concerns for inducing emesis in brachycephalic dogs are unfounded.
It has been reported that up to 97% of brachycephalic dogs have anatomical abnormalities that may predispose them to an increased risk of aspiration pneumonia.13,16 Some of these abnormalities identified in brachycephalic dogs include hiatal hernia, pyloric stenosis, pyloric mucosal hyperplasia, retention of gastric contents, and gastrointestinal reflux.17–20 Due to the retrospective nature of the current study, it is unknown whether any of the brachycephalic dogs had any anatomical abnormalities that may have affected the risks of complications.
The majority of dogs in this study had emesis induced for potential toxin ingestion. Various toxins can affect the nervous system or gastrointestinal system, leading to potential increased risk of aspiration. Since toxins were not categorized by affected organ systems and many times the potentially ingested toxin was unknown, any effect of the toxin category on complications could not be assessed. Those dogs with clinical signs of toxicity at presentation were more likely to have regurgitation compared to those without clinical signs, while no difference was found with clinical signs of toxicity and vomiting. In addition, while brachycephalic dogs had higher rates of toxin ingestion compared to nonbrachycephalic dogs, this did not translate to higher rates of complications. It is likely that the different rates of complications with signs of intoxication were due to the type of toxin ingested, but direct complications from the emesis induction could not be ruled out.
While this study found no increased risk of complications in brachycephalic dogs, it looked only at induced emesis. Further studies are advised to investigate whether spontaneous emesis is associated with different risk levels in brachycephalic and nonbrachycephalic dogs. Although the reasons for inducing emesis were not associated with complications, this study did find that brachycephalic dogs were more likely to present to the reporting hospitals for toxin ingestion compared to other conformations. Given that the participating hospitals are referral hospitals, referring veterinarian concerns about risks of emesis with brachycephalic dogs may have led to a higher proportion of dogs with this conformation presenting for care.
The limitations of this study were those often associated with a retrospective design. The study relied on preexisting data that varied in level of detail. The relatively low overall percentage of brachycephalic dogs in the study population (20.6%) may have led to type II error. The number of complications were < 1% in this study, consisting only of regurgitation and recurrent vomiting. Considering a lack of consistent follow-up following discharge, the possibility exists that patients that did not develop complications immediately could have developed complications after discharge or, if they did, may not have re-presented to the same hospital for follow-up care. This may lead to under-documentation of the number of complications, and additional follow-up is advised.
In conclusion, this study had very low complication rates when APO was used to induce emesis in dogs, with no increased risk of complications in brachycephalic breeds compared to nonbrachycephalic breeds. This extends to the reason for inducing emesis, whether for FB or toxin ingestion. Prospective studies with defined follow-up periods may help determine whether delayed complication rates are present. Future studies are needed to prospectively investigate risks associated with spontaneous emesis due to illness, comparing brachycephalic and nonbrachycephalic breeds.
Supplementary Materials
Supplementary materials are posted online at the journal website: avmajournals.avma.org
Acknowledgments
The authors wish to acknowledge the staff at Animal Referral and Emergency Centre for their assistance with data collection.
Disclosures
The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.
Funding
The authors have nothing to disclose.
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