Study design
This study was approved by the Institutional Animal Care and Use Committee of the Université de Montréal (protocol 17-Rech-1890) and performed at the Centre hospitalier universitaire vétérinaire (CHUV), Faculty of Veterinary Medicine, Université de Montréal, between July 2017 and February 2018. This clinical trial is reported in accordance with the CONSORT guidelines [20]. The study design was a prospective, blinded, randomized clinical trial.
Animals
Twenty-four adult (> 1 year of age) cats of any breeds and gender with or without naturally occurring oral disease were included. Cats that could possibly require oral treatment were recruited from different shelter facilities. Before enrollment, an oral examination including the condition of gingiva and the amount of calculus was performed in the conscious cat by the dentistry service so the principal investigator (PS), but not other observers involved with anesthesia and pain assessment, would have an idea of group allocation that could facilitate further patient recruitment (cats with minimal or severe disease). A written informed consent was obtained before enrolment in the study. Animals were admitted approximately 24 h before general anesthesia (day 0); dental treatment was performed on day 1. Cats were discharged on day 6 (7 days after arrival and 6 days after treatment of oral disease) (Fig. 1). During hospitalization, they were housed in stainless steel cages in the cat ward of the CHUV with access to water ad libitum, toys, litter box and bedding. At the end of the study, they were returned to the shelter facilities for adoption.
Inclusion and exclusion criteria
Cats with body condition score ranging from 4 to 6 out of 9 and with no/minimal or severe oral disease that would require oral treatment including dental examination, scaling and/or extractions were included in the study. Inclusion criteria were also based on history, medical records, complete physical examination, and hematology and biochemical panel. Cats presenting fearful behaviors, concurrent medical conditions, systemic disorders (e.g. cancer, renal, cardiovascular, hepatic, or gastrointestinal disease) were not included. Cats were excluded if they received any medication including analgesics and antibiotics for up to 10 days before the study had begun or presented signs of disease during hospitalization.
Treatment of oral disease
Group allocation
Complete dental examination and radiography were performed, and patients underwent dental scaling and dental extractions (if needed) by a board-certified dentist and a resident of the American Veterinary Dental College. Group allocation (i.e. minimal or severe oral disease) was determined according to a scoring system suggested by these two individuals in agreement with the principal investigator (PS) based on their previous clinical experience. In brief, the number and location of extractions were thought to be important in determining the possible severity of postoperative pain [12]. The scores were as follows: canine tooth - 3 points, third premolar of maxilla or molar of mandible - 2 points, second premolar of maxilla or premolar of mandible - 1 point; a score of 2 points was given if seven or more incisive teeth and/or first premolars of the mandible were extracted; otherwise a score of 1 point was given if six or fewer incisive teeth were removed. The total dental score was calculated, and cats were allocated to the minimal oral disease group if dental score ≤ 7, and to the severe oral disease group if dental score was ≥8.
Anesthesia and analgesic protocol
Premedication consisted of intramuscular (IM) (i.e. epaxial muscles) administration of acepromazine (0.02 mg/kg; 1 mg/mL, Acepromazine maleate, Gentès & Bolduc, Saint-Hyacinthe, QC, Canada) and hydromorphone (0.1 mg/kg; 2 mg/mL, Hydromorphone hydrochloride, Sandoz, Boucherville, QC, Canada). A eutectic mixture of local anesthetic cream (EMLA cream lidocaine 2.5% and procaine 2.5% cream, Astra Zeneca, Mississauga, ON, Canada) was applied to the skin over the cephalic vein after clipping and covered with plastic film and adhesive bandage. Approximately 20 min later, a 22-G intravenous (IV) catheter was aseptically placed in one of the cephalic veins. Anesthetic induction was performed with the administration of intravenous propofol (4.0 ± 1.2 mg/kg) (10 mg/mL, Propoflo 28, Zoetis, Kirkland, QC, Canada) until the anesthetic depth for endotracheal intubation was achieved . The arytenoid cartilages were splashed with 0.05 mL of lidocaine 2% (Lidocaine hydrochloride sterile injection, 20 mg/mL, Vétoquinol N.-A.Inc., Lavaltrie, QC, Canada), and cats were intubated with a cuffed endotracheal tube and connected to a coaxial Mapleson D system. Anesthetic maintenance was performed with isoflurane (Isoflurane USP, Fresenius Kabi, Toronto, ON, Canada) in 100% oxygen. Anesthetic monitoring was performed with a multiparametric monitor (Lifewindow 6000 V Veterinary Multiparameter Monitor; Digicare Animal Health, Boynton Beach, FL, USA) as reported in our previous article [12]. A crystalloid solution was administered (2–5 ml/ kg/hour) throughout the procedure. Cats received local anesthetic blocks with bupivacaine 0.5% (50 mg/mL, Sensorcaine, AstraZeneca, ON, Canada) using a 25-G needle if dental extractions were required. These included the mental, infraorbital, maxillary and/or inferior alveolar mandibular nerve blocks approximately 20 min before tooth extraction. The total dose of bupivacaine for all anesthetic blocks did not exceed 2 mg/kg. Meloxicam (0.2 mg/kg; Metacam 5 mg/mL Solution for Injection; Boehringer Ingelheim, Burlington, ON, Canada) was administered subcutaneously at the end of the dental procedure. Three additional doses of meloxicam at 0.05 mg/kg were administered orally at 24, 48 and 72 h after the first dose according to label recommendations in Canada.
Video recording
The schedule for video recording was performed according to Fig. 1. There were nine time points of video recording and each lasted 10 min (total of 90 min for each cat). A wide-angle glass lens camera (GoPro Hero 5, GoPro, Riverside, CA, USA) set between cage bars was used. Cats were moved to a specific cage for video recording that included better lighting and material quality. After a 5-min acclimation period, the camera was activated remotely using a smart-phone (iPhone7, Apple Inc., Cupertino, CA, USA). During the 10-min period, video recording was performed as follows: a) time 0–3 min: the general behaviors of the cat were recorded without any observer in the room (3 min; general behavior), b) time 3–5 min: the observer entered the room, greeted and petted the cat, stimulated the cat to play with a ribbon toy (2 min; playing behavior), c) time 5–8 min: the cat was fed with dry or soft food; feeding should potentially evoke pain behaviors as it has been described in the literature (3 min; feeding behavior) [6] and d) time 8–10 min: food was removed, and cats were filmed for another 2 min without the observer in the room (2 min; post-feeding behavior). Cats were fed with dry food (Hill’s Science Diet, Adult Optimal Care – Dry; Hill’s Pet Nutrition Canada Inc., Mississauga, ON, Canada) at 6 pm on day 0 and 8 am on day 6. A commercial canned prescription recovery diet (Hill’s Prescription Diet a/d; Hill’s Pet Nutrition Canada Inc., Mississauga, ON, Canada) was provided at 1 pm on day 0; 6 am and postoperative 2 and 6 h on day 1; at 8 am, 1 pm and 6 pm at days 2, 3, 4 and 5. Any remaining food was removed after 2 h.
Video analysis
A total of 36 h of video material was analyzed using a professional software (The Observer XT, Noldus information technology, VA, U.S.A). Videos were randomized according to the website www.randomization.com and assessed by a board-certified behaviorist [DF] of the American College of Veterinary Behaviorists who was blinded to severity groups. An ethogram was developed using normal behaviors and those described in painful cats with oral disease in review and scientific articles, textbooks and clinical experience [6, 7, 17]. Some behaviors were added to the ethogram based on the researchers’ observation during pain assessment of these cats [12]. The duration (%) (duration of each behavior/video length × 100) or frequency (times of the event/minute or total number of each behavior during the video/video length) for each behavior were obtained for statistical analysis. Baseline duration and frequency of each behavior were calculated using the mean of preoperative values. For general and playing behaviors, the mean of three values were used (1 pm and 6 pm on day 0 and 6 am on day 1) whereas for feeding and post-feeding with soft food, the mean of two values (1 pm on day 0 and 6 am on day 1) were used to calculate baseline mean values. The behaviors that were recorded less than five times during video assessment were excluded from statistical analysis.
Pain assessment
Pain assessment was performed by an observer [RW] who was unaware of the disease severity using the Glasgow composite measure pain scale-feline (CMPS-F) according to Fig. 1 [15]. Pain assessment was performed before video recording. Rescue analgesia was administered with hydromorphone at 0.05 mg/kg IV (if the intravenous catheter was in place, first 24 h after surgery) or 0.1 mg/kg IM (if the intravenous catheter had been removed) when CMPS-F scores were ≥ 5/20 at any time during the study. Based on the duration of hydromorphone in cats, the videos obtained within 2 h of rescue analgesia were excluded from statistical analysis to avoid bias [19].
Statistical analysis
Statistical analyses were performed using SAS version 9.3 (SAS Institute, Cary, NC, USA). The power analysis revealed that eight cats would be needed per group to detect a difference of three points in the CMPS-F pain scores between the two groups 80% of the time using an alpha value of 0.05, and a standard deviation within group of two points [12]. Twelve cats were included per group for adequate power considering the individual variability of oral disease. After normality test using a Shapiro-Wilk test, demographic data for each treatment group were compared using two-sample t-tests or Mann-Whitney U where appropriate. Duration and frequency of each behavior were compared between groups at each time point, and between baseline and the postoperative time points in both groups. Duration of each behavior was transformed using the arcsine square root transformation and analyzed using a linear mixed model with patient identification as the random factor, and groups and time and their interaction as fixed factors, and gender as co-factor. Frequency of each behavior was analyzed using a generalized linear model with log link and Poisson errors with patient identification as the random factor, groups and time as fixed factors, and gender as co-factor. When there was an association with fixed factors, a series of a priori contrasts were performed to compare the means using sequential Benjamini-Hochberg’s adjustment. p < 0.05 was considered statistically significant.
