Measurement properties of grimace scales for pain assessment in nonhuman mammals: a systematic review.

ABSTRACT: Facial expressions of pain have been identified in several animal species. The aim of this systematic review was to provide evidence on the measurement properties of grimace scales for pain assessment. The protocol was registered (SyRF#21-November-2019), and the study is reported according to the PRISMA guidelines. Studies reporting the development, validation, and the assessment of measurement properties of grimace scales were included. Data extraction and assessment were performed by 2 investigators, following the COnsensus-based Standards for the Selection of Health Measurement INstruments guidelines. Six categories of measurement properties were assessed: internal consistency, reliability, measurement error, criterion and construct validity, and responsiveness. Overall strength of evidence (high, moderate, and low) of each instrument was based on methodological quality, number of studies, and studies' findings. Twelve scales for 9 species were included (mice, rats, rabbits, horses, piglets, sheep or lamb, ferrets, cats, and donkeys). Considerable variability regarding their development and measurement properties was observed. The Mouse, Rat, Horse and Feline Grimace Scales exhibited high level of evidence. The Rabbit, Lamb, Piglet and Ferret Grimace Scales and Sheep Pain Facial Expression Scale exhibited moderate level of evidence. The Sheep Grimace Scale, EQUUS-FAP, and EQUUS-Donkey-FAP exhibited low level of evidence for measurement properties. Construct validity was the most reported measurement property. Reliability and other forms of validity have been understudied. This systematic review identified gaps in knowledge on the measurement properties of grimace scales. Further studies should focus on improving psychometric testing, instrument refinement, and the use of grimace scales for pain assessment in nonhuman mammals.

Agreement and reliability of the Feline Grimace Scale among cat owners, veterinarians, veterinary students and nurses.

This study aimed to evaluate the agreement and reliability of the Feline Grimace Scale (FGS) among cat owners, veterinarians, veterinary students and nurses/technicians. Raters (n = 5/group) scored 100 images using the FGS (ear position, orbital tightening, muzzle tension, whiskers position and head position). Intra-class correlation coefficients (ICC) were used to assess inter- and intra-rater reliability. Agreement between each group and the veterinarian group (gold-standard) was calculated using the Bland-Altman method. Effects of gender, age and number of cats owned on FGS scores were assessed using linear mixed models. Inter-rater reliability was good for FGS final scores (ICC > 0.8). The muzzle and whiskers yielded lower reliability (ICC = 0.39 to 0.74). Intra-rater reliability was excellent for students and veterinarians (ICC = 0.91), and good for owners and nurses (ICC = 0.87 and 0.81, respectively). A very good agreement between all groups and veterinarians (bias < 0.1 and narrow limits of agreement) was observed. Female raters assigned higher FGS scores than males (p = 0.006); however, male raters were underrepresented in this study. Scores were not affected by age or number of cats owned. The FGS is reliable for feline acute pain assessment when used by individuals with different experience.

Pain burden, sensory profile and inflammatory cytokines of dogs with naturally-occurring neuropathic pain treated with gabapentin alone or with meloxicam.

Canine neuropathic pain (NeuP) has been poorly investigated. This study aimed to evaluate the pain burden, sensory profile and inflammatory cytokines in dogs with naturally-occurring NeuP. Twenty-nine client-owned dogs with NeuP were included in a prospective, partially masked, randomized crossover clinical trial, and treated with gabapentin/placebo/gabapentin-meloxicam or gabapentin-meloxicam/placebo/gabapentin (each treatment block of 7 days; total 21 days). Pain scores, mechanical (MNT) and electrical (ENT) nociceptive thresholds and descending noxious inhibitory controls (DNIC) were assessed at baseline, days 7, 14, and 21. DNIC was evaluated using ΔMNT (after-before conditioning stimulus). Positive or negative ΔMNT corresponded to inhibitory or facilitatory pain profiles, respectively. Pain scores were recorded using the Client Specific Outcome Measures (CSOM), Canine Brief Pain Inventory (CBPI), and short-form Glasgow Composite Measure Pain Scale (CMPS-SF). Data from baseline were compared to those of sixteen healthy controls. ΔMNT, but not MNT and ENT, was significantly larger in controls (2.3 ± 0.9 N) than in NeuP (-0.2 ± 0.7 N). The percentage of dogs with facilitatory sensory profile was similar at baseline and after placebo (61.5-63%), and between controls and after gabapentin (33.3-34.6%). The CBPI scores were significantly different between gabapentin (CBPI pain and CBPI overall impression) and/or gabapentin-meloxicam (CBPI pain and interference) when compared with baseline, but not placebo. The CBPI scores were not significantly different between placebo and baseline. The concentration of cytokines was not different between groups or treatments. Dogs with NeuP have deficient inhibitory pain mechanisms. Pain burden was reduced after gabapentin and/or gabapentin-meloxicam when compared with baseline using CBPI and CMPS-SF scores. However, these scores were not superior than placebo, nor placebo was superior to baseline evaluations. A caregiver placebo effect may have biased the results.

Anesthetic and analgesic effects of an opioid-free, injectable protocol in cats undergoing ovariohysterectomy: A prospective, blinded, randomized clinical trial.

This study evaluated the effects of ketamine-dexmedetomidine-midazolam as part of an opioid-free, multimodal protocol in cats undergoing ovariohysterectomy. In a prospective, blinded, randomized clinical trial, cats received either 1 of 2 doses of ketamine [5 mg/kg body weight (BW), n = 10, K5 or 7 mg/kg BW, n = 13, K7] with midazolam (0.25 mg/kg BW) and dexmedetomidine (40 µg/kg BW) intramuscularly, intraperitoneal bupivacaine (2 mg/kg BW) and subcutaneous meloxicam (0.2 mg/kg BW) after surgery. Buprenorphine (0.02 mg/kg BW, intravenously) was administered if pain scores exceeded intervention scores with 2 pain scoring systems. Similar prevalence of rescue analgesia was observed (K5 = 6/10; K7 = 7/13) with significantly lower requirements in kittens (2/8) than adults (11/15). Tachypnea (K5 = 7/10 and K7 = 9/13) and desaturation (K5 = 3/10 and K7 = 4/13) were the 2 most common complications. Age influenced the prevalence of rescue analgesia. Most adult cats required opioids for postoperative pain relief.

Effets anesthésiants et analgésiques d'un protocole injectable sans opioïde chez des chats soumis à une ovario-hystérectomie : essai clinique prospectif, randomisé, à l'aveugle. Lors de la présente étude nous avons évalué les effets de la combinaison kétamine-dexmedetomidine-midazolam comme élément d'un protocole multimodal sans opioïde chez des chats soumis à une ovario-hystérectomie. Dans un essai clinique prospectif, randomisé, à l'aveugle, des chats reçurent une des deux doses de kétamine [5 mg/kg poids corporel (BW), n = 10, K5 ou 7 mg/kg BW, n = 13, K7] avec du midazolam (0,25 mg/kg BW) et du dexmedetomidine (40 µg/kg BW) par voie intramusculaire, de la bupivacaine par voie intrapéritonéale (2 mg/kg BW) et du meloxicam sous-cutané (0,2 mg/kg BW) après la chirurgie. De la buprenorphine (0,02 mg/kg BW, par voie intraveineuse) fut administrée si les pointages de douleur excédaient les pointages d'intervention avec deux systèmes de pointage de la douleur. Une prévalence similaire d'analgésie de secours fut observée (K5 = 6/10; K7 = 7/13) avec des demandes significativement moindres chez les chatons (2/8) que chez les adultes (11/15). De la tachypnée (K5 = 7/10 et K7 = 9/13) et de la désaturation (K5 = 3/10 et K7 = 4/13) étaient les deux complications les plus fréquentes. L'âge influençait la prévalence de l'analgésie de secours. La plupart des chats adultes ont requis des opioïdes pour soulager la douleur post-opératoire.(Traduit par Dr Serge Messier).

Inter-Rater Reliability of the Feline Grimace Scale in Cats Undergoing Dental Extractions.

This study aimed to evaluate the inter-rater reliability of the Feline Grimace Scale (FGS) in cats undergoing dental extractions and the effects of the caregiver's presence on the FGS scores. Twenty-four cats (6 ± 3.3 years old; 4.9 ± 1.7 kg) undergoing oral treatment were included in a prospective, blinded, randomized, clinical study. They underwent treatment under general anesthesia (acepromazine-hydromorphone-propofol-isoflurane-meloxicam-local anesthetic blocks) at day 1 and were discharged at day 6. Images of cat faces were captured from video recordings with or without the caregiver's presence at 6 h postoperatively (day 1), day 6, and before and after rescue analgesia. Images were randomized and independently evaluated by four raters using the FGS [five action units (AU): ear position, orbital tightening, muzzle tension, whiskers change, and head position; score 0-2 for each]. Inter-rater reliability and the effects of the caregiver's presence were analyzed with intraclass correlation coefficient [single measures (95% confidence interval)] and the Wilcoxon signed-rank test, respectively (p < 0.05). A total of 91 images were scored. Total FGS scores showed good inter-rater reliability [0.84 (0.77-0.89)]. Reliability for each AU was: ears [0.68 (0.55-0.78)], orbital tightening [0.76 (0.65-0.84)], muzzle [0.56 (0.43-0.69)], whiskers [0.64 (0.50-0.76)], and head position [0.74 (0.63-0.82)]. The FGS scores were not different with [0.075 (0-0.325)] or without [0.088 (0-0.525)] the caregivers' presence (p = 0.12). The FGS is a reliable tool for pain assessment in cats undergoing dental extractions. The caregiver's presence did not affect FGS scores.

Clinical applicability of the Feline Grimace Scale: real-time versus image scoring and the influence of sedation and surgery.

BACKGROUND: The Feline Grimace Scale (FGS) is a facial expression-based scoring system for acute pain assessment in cats with reported validity using image assessment. The aims of this study were to investigate the clinical applicability of the FGS in real-time when compared with image assessment, and to evaluate the influence of sedation and surgery on FGS scores in cats. METHODS: Sixty-five female cats (age: 1.37 ± 0.9 years and body weight: 2.85 ± 0.76 kg) were included in a prospective, randomized, clinical trial. Cats were sedated with intramuscular acepromazine and buprenorphine. Following induction with propofol, anesthesia was maintained with isoflurane and cats underwent ovariohysterectomy (OVH). Pain was evaluated at baseline, 15 min after sedation, and at 0.5, 1, 2, 3, 4, 6, 8, 12 and 24 h after extubation using the FGS in real-time (FGS-RT). Cats were video-recorded simultaneously at baseline, 15 min after sedation, and at 2, 6, 12, and 24 h after extubation for subsequent image assessment (FGS-IMG), which was performed six months later by the same observer. The agreement between FGS-RT and FGS-IMG scores was calculated using the Bland & Altman method for repeated measures. The effects of sedation (baseline versus 15 min) and OVH (baseline versus 24 h) were assessed using linear mixed models. Responsiveness to the administration of rescue analgesia (FGS scores before versus one hour after) was assessed using paired t-tests. RESULTS: Minimal bias (-0.057) and narrow limits of agreement (-0.351 to 0.237) were observed between the FGS-IMG and FGS-RT. Scores at baseline (FGS-RT: 0.16 ± 0.13 and FGS-IMG: 0.14 ± 0.13) were not different after sedation (FGS-RT: 0.2 ± 0.15, p = 0.39 and FGS-IMG: 0.16 ± 0.15, p = 0.99) nor at 24 h after extubation (FGS-RT: 0.16 ± 0.12, p = 0.99 and FGS-IMG: 0.12 ± 0.12, p = 0.96). Thirteen cats required rescue analgesia; their FGS scores were lower one hour after analgesic administration (FGS-RT: 0.21 ± 0.18 and FGS-IMG: 0.18 ± 0.17) than before (FGS-RT: 0.47 ± 0.24, p = 0.0005 and FGS-IMG: 0.45 ± 0.19, p = 0.015). CONCLUSIONS: Real-time assessment slightly overestimates image scoring; however, with minimal clinical impact. Sedation with acepromazine-buprenorphine and ovariohysterectomy using a balanced anesthetic protocol did not influence the FGS scores. Responsiveness to analgesic administration was observed with both the FGS-RT and FGS-IMG.

The analgesic effects of buprenorphine (Vetergesic or Simbadol) in cats undergoing dental extractions: A randomized, blinded, clinical trial.

This study aimed to evaluate the analgesic efficacy of two dosage regimens using two different concentrations of buprenorphine in cats undergoing dental extractions. Twenty-three cats with oral disease (8.2 ± 2.2 years old; 4.9 ± 0.9 kg) were included in a prospective, blinded, randomized clinical trial. Cats randomly received either Simbadol (1.8 mg/mL; 0.24 mg/kg, subcutaneously, every 24h: SG, n = 11) or Vetergesic (0.3 mg/mL; 0.02 mg/kg, intramuscularly, every 8h: VG, n = 12) throughout the study. They were admitted at day 0, underwent oral examination/radiographs/treatment under general anesthesia (buprenorphine-propofol-isoflurane-meloxicam-local anesthetic blocks) at day 1 and discharged at day 4. Sedation and pain were scored using the dynamic interactive visual analog scale (day 1) and the Glasgow Composite Measure Pain Scale-Feline (CMPS-F; up to postoperative 8 hours at day 1, 8 am, 4 pm and midnight at days 2 and 3, and 8 am at day 4), respectively. Rescue analgesia was administered with hydromorphone (0.05 mg/kg intravenously on day 1 or 0.1 mg/kg intramuscularly after day 2) when CMPS-F ≥ 5. Resentment defined as any type of escape behavior associated with aversion to drug administration was recorded. Sedation and pain scores, the prevalence of rescue analgesia and resentment during drug administration were analyzed using linear mixed models and Fisher's exact test, respectively (p < 0.05). Pain and sedation scores were not significantly different between groups. Sedation scores were significantly higher up to postoperative 2 hours in both groups. Pain scores in SG and VG were significantly higher up to postoperative 8 hours and 8 am of day 2, respectively, than baseline. Prevalence of rescue analgesia and resentment were not significantly different between groups (SG: 27.3%, VG: 33.3% and SG: 0%, VG: 25%, respectively). Simbadol produced similar analgesic effects to Vetergesic without resentment during drug administration.

Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale.

Grimace scales have been used for pain assessment in different species. This study aimed to develop and validate the Feline Grimace Scale (FGS) to detect naturally-occurring acute pain. Thirty-five client-owned and twenty control cats were video-recorded undisturbed in their cages in a prospective, case-control study. Painful cats received analgesic treatment and videos were repeated one hour later. Five action units (AU) were identified: ear position, orbital tightening, muzzle tension, whiskers change and head position. Four observers independently scored (0-2 for each AU) 110 images of control and painful cats. The FGS scores were higher in painful than in control cats; a very strong correlation with another validated instrument for pain assessment in cats was observed (rho = 0.86, p < 0.001) as well as good overall inter-rater reliability [ICC = 0.89 (95% CI: 0.85-0.92)], excellent intra-rater reliability (ICC > 0.91), and excellent internal consistency (Cronbach's alpha = 0.89). The FGS detected response to analgesic treatment (scores after analgesia were lower than before) and a cut-off score was determined (total pain score > 0.39 out of 1.0). The FGS is a valid and reliable tool for acute pain assessment in cats.

Analgesic Efficacy of Bupivacaine or Bupivacaine-Dexmedetomidine After Intraperitoneal Administration in Cats: A Randomized, Blinded, Clinical Trial.

The aim of this study was to compare the analgesic efficacy of intraperitoneal bupivacaine vs. bupivacaine-dexmedetomidine in combination with intramuscular buprenorphine in cats undergoing ovariohysterectomy. Sixty healthy adult cats (2.8 ± 0.7 kg; n = 30/group) were included in a randomized, prospective, blinded, clinical trial after owners' written consent. After premedication with acepromazine (0.02 mg/kg) and buprenorphine (0.02 mg/kg) intramuscularly, anesthesia was induced with propofol to effect (6.2 ± 1.4 mg/kg) and maintained with isoflurane. Bupivacaine 0.25% alone (BG; 2 mg/kg) or bupivacaine (same dose) with dexmedetomidine (BDG; 1 µg/kg) were instilled/splashed over the ovarian pedicles and caudal aspect of uterus before ovariohysterectomy. Final injectate volume was standardized between groups. Sedation was evaluated using a five-point simple descriptive scale. Pain was evaluated using the short-form UNESP-Botucatu composite pain scale (SF-CPS) before, and at 0.5, 1, 2, 3, 4, 6, 8, 12, and 24 h after surgery. Rescue analgesia was provided with buprenorphine (0.02 mg/kg intravenously) and meloxicam (0.2 mg/kg subcutaneously) when SF-CPS ≥ 4. The Mantel-Haenszel chi-square test was used for analyzing ordinal variables (e.g., SF-CPS pain scores). The effect of time in SF-CPS scores was assessed with the Cochran-Mantel-Haenszel test for repeated measures. The alpha level for each contrast was adjusted downward with the sequential Benjamini-Hochberg procedure. The number of cats receiving rescue analgesia was analyzed using χ2 test (p < 0.05). The prevalence of rescue analgesia was the same for the two treatments (p = 1.000) [BG, n = 6, 20%; BDG, n = 6, 20%] and similar for timing of rescue analgesia (p = 0.16). The SF-CPS scores were significantly increased between 1 and 12 h in BG, and between 0.5 and 8 h in BDG when compared with baseline values. Median (interquartile range) pain scores were higher in BG [1 (1-2)] than BDG [1 (0-1)] at 12 h (p = 0.023). Sedation scores were not significantly different between groups throughout the study. In terms of prevalence of rescue analgesia, but not duration of action, the analgesic efficacy of bupivacaine-dexmedetomidine was similar to bupivacaine alone after intraperitoneal administration in cats receiving buprenorphine.

Feasibility and reliability of electrical, mechanical and thermal nociceptive testing and assessment of diffuse noxious inhibitory control in dogs.

PURPOSE: Quantitative sensory testing has been used to assess the somatosensory system. This study aimed to evaluate the feasibility and reliability of electrical (ENT), mechanical (MNT) and thermal (TNT) nociceptive testing and the effect of a conditioning stimulus on MNT. PATIENTS AND METHODS: Sixteen healthy client-owned dogs were included in this study. Stimulation was applied bilaterally to the dorsal and plantar aspect of the metacarpus and metatarsus respectively, using transcutaneous electrical stimulator, algometry and a cold nociceptive device in a randomized order until a behavior response was observed or a cut-off reached. Tests were performed twice (60 seconds apart) by two observers. Retesting was performed 5 hours later. The diffuse noxious inhibitory control was tested by comparing MNT pre- and post-conditioning stimuli. Sham-testing was performed for ENT and TNT. Statistical analysis included linear model and intra-class correlation coefficient (P<0.05). RESULTS: Feasibility was 99% (ENT), 93.5% (MNT) and 93.6% (TNT). Data for TNT were not analyzed due to inconsistent results. Mean ± SD were 48±22.6 mA (ENT) and 11.9±3.5 N (MNT). MNT was higher for thoracic than for pelvic limbs (P=0.002). Conditioning stimulus increased MNT (P=0.049). Inter-observer reliability was 91.4% (ENT) and 60.9% (MNT). False-positive responses were 15% (ENT) and 35.7% (TNT). CONCLUSION: ENT was feasible, repeatable and superior to MNT and TNT. The assessment of the diffuse noxious inhibitory control with a conditioning stimulus showed promising results in dogs. These tools could be used in naturally-occurring disease to provide insight on their underlying mechanisms and therapeutics.

Postoperative pain and short-term complications after two elective sterilization techniques: ovariohysterectomy or ovariectomy in cats.

BACKGROUND: Surgical sterilization of cats is one of the most commonly performed procedures in veterinary practice and it can be accomplished by two different techniques: ovariohysterectomy (OVH) or ovariectomy (OVE). Although there is an apparent preference for OVH in United States and Canada, OVE seems to be the standard of care in many European countries due to its advantages, such as a smaller surgical incision and potentially less complications associated with surgical manipulation of the uterus. The aim of this randomized, blind, prospective study was to compare postoperative pain and short-term complications in cats undergoing ovariohysterectomy or ovariectomy. METHODS: Twenty female cats were randomly assigned into two groups (OVH, n = 10 and OVE, n = 10). Pain was assessed prior to surgery (baseline) and 1, 2, 4, 8 12 and 24 h after the procedure using pain and sedation scales, physiologic parameters and blood glucose levels. Short-term complications were evaluated in the early postoperative period and reassessed at day 7 and day 10. RESULTS: Changes in cardiovascular parameters were not clinically relevant, however cats in OVH group had higher heart rates at T1 h compared with baseline (p = 0.0184). Blood glucose levels in OVH group were also higher at T1 h compared with baseline (p = 0.0135) and with OVE group (p = 0.0218). Surgical time was higher in OVH group (p = 0.0115). Even though no significant differences in pain scores were observed between groups or time points, cats in OVH group had greater need for rescue analgesia compared with OVE (2/10 and 0/10, respectively). Complications were not observed in any cat during surgery, at days 7 and 10 postoperatively or at discharge. CONCLUSIONS: Both surgical techniques promoted similar intensity of postoperative pain in cats and there were no short-term complications throughout the study's evaluation period. Therefore, both techniques may be indicated for surgical sterilization of cats, according to the surgeon's preference and expertise. Cats that underwent ovariectomy did not require rescue analgesia and surgical time was shorter in that group.

The analgesic effects of buprenorphine (Vetergesic or Simbadol) in combination with carprofen in dogs undergoing ovariohysterectomy: a randomized, blinded, clinical trial.

BACKGROUND: Buprenorphine is a potent lipophilic opioid analgesic that is largely used in the multimodal treatment of acute pain. Simbadol (buprenorphine hydrochloride) is the first and only FDA-approved high-concentration formulation of buprenorphine for use in cats. The aim of this study was to evaluate the analgesic efficacy of carprofen in combination with one of two commercial formulations of buprenorphine (Simbadol and Vetergesic, 1.8 mg/mL and 0.3 mg/mL, respectively) in dogs undergoing ovariohysterectomy. Twenty-four dogs were included in a randomized, prospective, controlled, clinical trial. Patients were randomly divided into 2 groups as follows. Dogs were premedicated with acepromazine (0.02 mg/kg) and either 0.02 mg/kg of Vetergesic or Simbadol intramuscularly (Vetergesic group - VG; Simbadol group - SG, respectively; n = 12/group). General anesthesia was induced with propofol and maintained with isoflurane in 100% oxygen. Carprofen (4.4 mg/kg SC) was administered after induction of anesthesia. Heart rate, respiratory rate, blood pressure, pulse oximetry, pain scores using the Glasgow Composite Pain Scale Short Form (CMPS-SF), sedation scores using a dynamic interactive visual analogue scale and adverse events were evaluated before and after ovariohysterectomy by an observer who was unaware of treatment administration. If CMPS-SF scores were ≥ 5/20, dogs were administered rescue analgesia (morphine 0.5 mg/kg IM). Statistical analysis was performed using linear mixed models and Fisher's exact test (p < 0.05). RESULTS: Pain and sedation scores and physiological parameters were not significantly different between treatments. Three dogs in VG (25%) and none in SG (0%) required rescue analgesia (p = 0.109). Adverse effects (i.e. vomiting and melena) were observed in two dogs in SG and were thought to be related to stress and/or nonsteroidal anti-inflammatory drug toxicity. CONCLUSIONS: The administration of buprenorphine with carprofen preoperatively provided adequate postoperative analgesia for the majority of dogs undergoing OVH without serious adverse events. Prevalence of rescue analgesia was not significantly different between groups; however, it could be clinically relevant and explained by a type II error (i.e. small sample size). Future studies are necessary to determine if analgesic efficacy after Simbadol and Vetergesic is related to individual variability or pharmacokinetic differences.

Paravertebral brachial plexus blockade in cats: a cadaver study.

Objectives The aims of this study were to describe the paravertebral brachial plexus (PBP) blockade in cats, and compare the spread of bupivacaine-methylene blue solution (BMS) using two volumes of injection into the PBP. Methods Six cadavers (4.4 ± 1.8 kg) randomly received 0.15 ml/kg (LOW) or 0.2 ml/kg (HIGH) per injection of BMS into the PBP. The first injection was made ventral to the transverse process of the sixth cervical vertebra (nerves C6 and C7) at the emergence of nerve roots. A second injection was performed at the edge of the cranial border of the scapula and directed ventrally towards the first rib (C8 and T1). Cadavers were dissected and the presence of BMS in contact with the nerves (success rate) and length of staining were evaluated for each nerve (C6/C7/C8/T1). Length of target nerves in contact with BMS was measured and <15 mm was considered fair, ⩾15 mm sufficient and >40 mm excessive. Complications (aspiration of blood, staining of pleural space and/or spinal cord) were recorded. Paired t-test, Mann-Whitney U-test and χ2 test were used for statistical analysis when appropriate ( P <0.05). Results Eleven hemilateral brachial plexuses were injected. Aspiration of blood occurred during one injection. Inadvertent pleural or spinal staining was not observed. Success rates (positive nerve staining) in the LOW and HIGH groups, respectively, were as follows: C6: 83% and 80%; C7: 66% and 100%; C8: 66% and 100%; T1: 50% and 60% ( P >0.05). Median (range) length of nerve staining was 22 mm (15-39 mm) for LOW and 21 mm (13-35 mm) for HIGH ( P >0.05). Excessive nerve staining was not recorded. Conclusions and relevance This study describes the PBP blockade in cats with acceptable nerve staining and minimal complications. Success rate and length of nerve staining were not significantly different between the LOW and HIGH groups.

Analgesic effects of gabapentin and buprenorphine in cats undergoing ovariohysterectomy using two pain-scoring systems: a randomized clinical trial.

Objectives The aim of the study was to evaluate the analgesic efficacy of gabapentin-buprenorphine in comparison with meloxicam-buprenorphine or buprenorphine alone, and the correlation between two pain-scoring systems in cats. Methods Fifty-two adult cats were included in a randomized, controlled, blinded study. Anesthetic protocol included acepromazine-buprenorphine-propofol-isoflurane. The gabapentin-buprenorphine group (GBG, n = 19) received gabapentin capsules (50 mg PO) and buprenorphine (0.02 mg/kg IM). The meloxicam-buprenorphine group (MBG, n = 15) received meloxicam (0.2 mg/kg SC), buprenorphine and placebo capsules (PO). The buprenorphine group (BG, n = 18) received buprenorphine and placebo capsules (PO). Gabapentin (GBG) and placebo (MBG and BG) capsules were administered 12 h and 1 h before surgery. Postoperative pain was evaluated up to 8 h after ovariohysterectomy using a multidimensional composite pain scale (MCPS) and the Glasgow pain scale (rCMPS-F). A dynamic interactive visual analog scale (DIVAS) was used to evaluate sedation. Rescue analgesia included buprenorphine and/or meloxicam if the MCPS ⩾6. A repeated measures linear model was used for statistical analysis ( P <0.05). Spearman's rank correlation between the MCPS and rCMPS-F was evaluated. Results The prevalence of rescue analgesia with a MCPS was not different ( P = 0.08; GBG, n = 5 [26%]; MBG, n = 2 [13%]; BG, n = 9 [50%]), but it would have been significantly higher in the BG (n = 14 [78%]) than GBG ( P = 0.003; n = 5 [26%]) and MBG ( P = 0.005; n = 4 [27%]) if intervention was based on the rCMPS-F. DIVAS and MCPS/rCMPS-F scores were not different among treatments. A strong correlation was observed between scoring systems ( P <0.0001). Conclusions and relevance Analgesia was not significantly different among treatments using an MCPS. Despite a strong correlation between scoring systems, GBG/MBG would have been superior to the BG with the rCMPS-F demonstrating a potential type II error with an MCPS due to small sample size.

Thermal antinociception following oral administration of tapentadol in conscious cats.

OBJECTIVE: To evaluate the onset, magnitude and duration of thermal antinociception after oral administration of two doses of tapentadol in cats. STUDY DESIGN: Prospective, randomized, blinded, experimental study. ANIMALS: Six healthy adult cats weighing 4.4 ± 0.4 kg. METHODS: Skin temperature (ST) and thermal threshold (TT) were evaluated using a wireless TT device up to 12 hours after treatment. Treatments included placebo (PBO, 50 mg dextrose anhydrase orally), buprenorphine (BUP, 0.02 mg kg-1) administered intramuscularly, low-dose tapentadol (LowTAP, 25 mg orally; mean 5.7 mg kg-1) and high-dose tapentadol (HighTAP, 50 mg orally; mean 11.4 mg kg-1) in a blinded crossover design with 7 day intervals. Statistical analysis was performed using anova with appropriate post hoc test (p ≤ 0.05). RESULTS: Salivation was observed immediately following 11 out of 12 treatments with tapentadol. The ST was significantly increased at various time points in the opioid treatments. Hyperthermia (≥ 39.5 °C) was not observed. Baseline TT was 45.4 ± 1.4 °C for all treatments. Maximum TT values were 48.8 ± 4.8 °C at 1 hour in LowTAP, 48.5 ± 3.0 °C at 2 hours in HighTAP and 50.2 ± 5.3 °C at 1 hour in BUP. TT significantly increased after LowTAP at 1 hour, after HighTAP at 1-2 hours, and after BUP at 1-2 hours compared with baseline values. TTs were significantly increased in BUP at 1-2 hours compared with PBO. CONCLUSION AND CLINICAL RELEVANCE: Oral administration of tapentadol increased ST and TT in cats. The durations of thermal antinociception were similar between HighTAP and BUP, both of which were twice as long as that in LowTAP. Studies of different formulations may be necessary before tapentadol can be accepted into feline practice.

Distribution of bupivacaine hydrochloride after sciatic and femoral nerve blocks in cats: A magnetic resonance imaging study.

The objective of this study was to evaluate the distribution of bupivacaine hydrochloride using magnetic resonance imaging (MRI) after electrical nerve stimulator (ENS)-guided sciatic (ScN) and femoral (FN) nerve blocks in cats. Six adult cats (body weight 4.8±0.6kg) were anesthetized with acepromazine-buprenorphine-propofol-isoflurane. Transverse and sagittal plan sequences of pelvic limbs were obtained using a high-field magnet (1.5T). Afterwards, the ScN and FN blocks (one block per limb) were performed using 0.1mL/kg of bupivacaine 0.5% per site and the MRI sequence was repeated after each block. The injection was considered successful when bupivacaine was in contact with the nerve. Injectate location and complications were recorded. The length (mm) of contact (spread) between bupivacaine and nerves was measured and classified as fair (<15mm) or adequate (≥15mm). Five out of six ScN injections were successful; of these, four had adequate spread over the nerve [26 (13-39) mm]. All FN injections were successful, but in one case bupivacaine was administered over the motor branch of FN, distally to the bifurcation between the femoral and saphenous nerve. It was not possible to measure neither the length of contact between bupivacaine and FN nor to identify iatrogenic trauma caused by the injections. MRI can be used for the evaluation of bupivacaine distribution, but not complications, following ENS-guided ScN and FN blocks in cats. Despite most of the injections were considered successful, individual variability regarding the injectate location may explain differences in efficacy in the clinical setting.

Morphine-induced pruritus after epidural administration followed by treatment with naloxone in a cat.

CASE SUMMARY: A young male domestic shorthair cat weighing 1.6 kg was admitted to a veterinary teaching hospital for elective orchiectomy. A lumbosacral epidural injection of preservative-free morphine (0.1 mg/kg) and lidocaine (0.25 ml/kg) was performed under general anesthesia. One hour after extubation, the cat became agitated. Severe licking and biting of the hindlimbs, tail and lumbar area were observed. Pruritus was suspected and likely to be caused by epidural morphine. Acepromazine (0.02 mg/kg IM) was administered but clinical signs did not cease. Naloxone (2 µg/kg IV) was administered and clinical signs resolved within 20 mins. RELEVANCE AND NOVEL INFORMATION: Different therapeutic approaches are available for the treatment of morphine-induced pruritus. This case describes an additional treatment option using opioid antagonism with naloxone.

Comparison of preoperative tramadol and pethidine on postoperative pain in cats undergoing ovariohysterectomy.

BACKGROUND: A variety of analgesic agents are available, and which one can be used in dogs and cats is a highly controversial issue, existing however a fear in the use of opiates due to possible adverse effects that these drugs can cause. The aim of this study was to compare the analgesic effect provided by the administration of tramadol or pethidine on early postoperative pain of cats undergoing ovariohysterectomy in a double-blind prospective study. Fourty-two animals were randomly assigned into three groups. Pet received pethidine (6 mg/kg), Tra 2 received tramadol (2 mg/kg) and Tra 4 received tramadol (4 mg/kg); all intramuscularly and associated with acepromazine (0.1 mg/kg). The efficacy of each analgesic regimen was evaluated prior to surgery (baseline - TBL), during surgery and 1, 3 and 6 hours after extubation with subjective pain scale, physiologic parameters, serum concentrations of glucose, cortisol and IL-6. RESULTS: Changes in cardiovascular system were not clinically relevant. There were no significant differences in pain scores (P > 0.05) during the study, although the number of rescue analgesia was significantly higher (P < 0.05) at Pet group (5/14) than Tra 4 group (0/14), whereas in Tra 2, two animals (2/14) required additional analgesia. The serum cortisol values of Pet group were significantly higher at T1h T3h (P < 0.05) and T6h (P < 0.01) when compared to baseline (induction), also it was noticed a significant difference among the groups at T6h (Pet values were higher than Tra 2 and Tra 4; P < 0.05). CONCLUSIONS: Tramadol provided adequate analgesia and it was more effective than pethidine to at least six hours for the studied animals. At the higher dose (4 mg/kg) tramadol is probably more effective, since rescue analgesia was not necessary. No significant changes were observed physiological parameter that could contraindicate the use of these opioid in described doses, for the feline species.