Comparison of lidocaine and lidocaine-epinephrine for the paravertebral brachial plexus block in dogs.

OBJECTIVE: To compare the motor and sensory block efficacy and duration of a modified paravertebral brachial plexus block (PBPB) after administration of lidocaine alone (LI) or combined with epinephrine (LE). STUDY DESIGN: Prospective, randomized, blinded, crossover study. ANIMALS: A total of eight healthy female Beagle dogs. METHODS: Under general anesthesia, modified PBPB was performed on the left thoracic limb using neurostimulation and/or ultrasound guidance to administer lidocaine (2 mg kg-1; 0.2 mL kg-1) either alone (treatment LI, n = 10) or with epinephrine (1:100,000; treatment LE, n = 9). Sensory block was evaluated through reaction to a painful mechanical stimulus applied at five sites on the limb. Motor block effect was evaluated according to visual gait assessments and thoracic limb vertical force measurements under dynamic and static conditions. Data were analyzed using repeated-measures generalized estimating equations. All statistical tests were performed two-sided at the α = 0.05 significance threshold. RESULTS: The duration of sensory block did not differ significantly between treatments. Visible gait impairment was more persistent in LE than in LI (118 ± 63 minutes for LI and 163 ± 23 minutes for LE; mean ± standard deviation) (p = 0.027). At nadir value, dynamic peak vertical force was lower in LE than in LI (p = 0.007). For both dynamic and static evaluations, the nadir and the return to baseline force were delayed in LE (return to normal at 180-200 minutes) when compared with LI (130-140 minutes) (p < 0.005). CONCLUSIONS AND CLINICAL RELEVANCE: The addition of epinephrine to lidocaine prolonged the duration and increased the intensity of the regional block, as verified by visual gait assessment and kinetic analysis. No significant difference was noted between treatments regarding sensory blockade. Kinetic analysis could be useful to evaluate regional anesthetic effect in dogs.

Analgesic efficacy of tramadol in cats with naturally occurring osteoarthritis.

OBJECTIVES: This study aimed to (1) compare outcome assessments in normal and osteoarthritic cats and (2) evaluate the analgesic efficacy of tramadol in feline osteoarthritis (OA), in a prospective, randomised, blinded, placebo-controlled, crossover design. METHODS: Twenty cats were included after clinical examination, blood work and full body radiographs were performed. In Phase 1, outcome assessments aimed to differentiate normal (n = 5; i.e. exempt of any radiographic and clinical sign of OA) from OA (n = 15) cats. In Phase 2, OA cats were treated twice daily with a placebo (PG: cornstarch 15 mg) or tramadol (TG: 3 mg/kg) orally for 19 days, with a 3-month washout period between treatments. Evaluations were performed in normal and OA cats at baseline and consisted of: 1) peak vertical force (PVF) after staircase exercise; 2) telemetered night-time motor activity (NMA); and 3) response to mechanical temporal summation (RMTS). After treatment, PVF, NMA and RMTS evaluations were repeated in OA cats. Data were analysed with mixed model methods with an alpha-threshold of 5%. RESULTS: Phase 1: 1) PVF (% of body weight; mean ± SD) was higher in normal (59 ± 10.5) than in OA cats (50.6 ± 5.7) (p = 0.005); 2) NMA (no unit) was not different between groups; 3) RMTS (number of stimuli; median (range)) was higher in normal [29.5 (23.5-30)] than in OA cats [14 (8.5-28)] (p < 0.0001). Phase 2: PVF, NMA and RMTS presented a treatment effect (p = 0.024, p = 0.008 and p = 0.018, respectively). No clinically important adverse-effects were observed. CONCLUSION: Outcome assessments such as kinetics (PVF) and evaluation of central sensitisation (RMTS) are discriminant of OA status. Mobility measured by NMA was not discriminant of OA status, however it increased in OA cats with tramadol treatment. Nociceptive hypersensitivity quantified by RMTS was evident in OA cats and was responsive to tramadol treatment.

Concurrent validity of different functional and neuroproteomic pain assessment methods in the rat osteoarthritis monosodium iodoacetate (MIA) model.

BACKGROUND: Lack of validity in osteoarthritis pain models and assessment methods is suspected. Our goal was to 1) assess the repeatability and reproducibility of measurement and the influence of environment, and acclimatization, to different pain assessment outcomes in normal rats, and 2) test the concurrent validity of the most reliable methods in relation to the expression of different spinal neuropeptides in a chemical model of osteoarthritic pain. METHODS: Repeatability and inter-rater reliability of reflexive nociceptive mechanical thresholds, spontaneous static weight-bearing, treadmill, rotarod, and operant place escape/avoidance paradigm (PEAP) were assessed by the intraclass correlation coefficient (ICC). The most reliable acclimatization protocol was determined by comparing coefficients of variation. In a pilot comparative study, the sensitivity and responsiveness to treatment of the most reliable methods were tested in the monosodium iodoacetate (MIA) model over 21 days. Two MIA (2 mg) groups (including one lidocaine treatment group) and one sham group (0.9 % saline) received an intra-articular (50 µL) injection. RESULTS: No effect of environment (observer, inverted circadian cycle, or exercise) was observed; all tested methods except mechanical sensitivity (ICC <0.3), offered good repeatability (ICC ≥0.7). The most reliable acclimatization protocol included five assessments over two weeks. MIA-related osteoarthritic change in pain was demonstrated with static weight-bearing, punctate tactile allodynia evaluation, treadmill exercise and operant PEAP, the latter being the most responsive to analgesic intra-articular lidocaine. Substance P and calcitonin gene-related peptide were higher in MIA groups compared to naive (adjusted P (adj-P) = 0.016) or sham-treated (adj-P = 0.029) rats. Repeated post-MIA lidocaine injection resulted in 34 times lower downregulation for spinal substance P compared to MIA alone (adj-P = 0.029), with a concomitant increase of 17 % in time spent on the PEAP dark side (indicative of increased comfort). CONCLUSION: This study of normal rats and rats with pain established the most reliable and sensitive pain assessment methods and an optimized acclimatization protocol. Operant PEAP testing was more responsive to lidocaine analgesia than other tests used, while neuropeptide spinal concentration is an objective quantification method attractive to support and validate different centralized pain functional assessment methods.

Analgesic efficacy of an oral transmucosal spray formulation of meloxicam alone or in combination with tramadol in cats with naturally occurring osteoarthritis.

OBJECTIVE: To evaluate the analgesic efficacy of meloxicam oral transmucosal spray (OTMS) alone and with tramadol in cats with osteoarthritis (OA). STUDY DESIGN: Randomized, blinded study. ANIMALS: Fifteen geriatric cats weighing 4.5 ± 1.0 kg. METHODS: Healthy cats with OA were randomly administered a placebo (every 12 hours orally) and meloxicam OTMS (approximately 0.05 mg kg-1 every 24 hours) (group M, n = 7), or tramadol (3 mg kg-1 every 12 hours orally) and meloxicam OTMS (group TM, n = 8) for 25 days. Evaluations performed before treatment (D0) and at week 3 (W3) consisted of peak vertical force, motor activity and response to mechanical temporal summation of pain (RMTS). Data were analyzed with mixed models and Fisher's exact test. RESULTS: Mean ± standard deviation peak vertical force (percentage of body weight) increased significantly in both groups (p = 0.02), from 47.7 ± 6.5% to 60.5 ± 9.4% in group M, and from 51.8 ± 5.0% to 64.1 ± 6.5% in group TM, with no difference between groups. Motor activity increased in M (from 43 ± 12 to 56 ± 13; p = 0.02), but not in TM. The number of stimulations from RMTS increased in TM only. Cut-off values were reached in a larger number of cats (n = 5) in TM than M (n = 1) (p < 0.05). Gastrointestinal adverse effects were self-limiting in six cats, including five in TM. CONCLUSIONS AND CLINICAL RELEVANCE: Meloxicam OTMS had similar effects on peak vertical force, motor activity and pain sensitization as previously reported for oral meloxicam in OA cats. The tramadol-meloxicam combination provided no evident benefit over meloxicam alone, except for central hypersensitivity (assessed with RMTS). Further assessment of the potential toxicity of the combination is required prior to clinical use. Gingival administration was well accepted overall.

A medicinal herb-based natural health product improves the condition of a canine natural osteoarthritis model: a randomized placebo-controlled trial.

An oral herb-based natural health product (NHP) was evaluated in the canine natural osteoarthritis model. At baseline, the peak vertical force (PVF, primary endpoint) and case-specific outcome measure of disability (CSOM) were recorded in privately-owned dogs. Dogs (16/group) were randomized to receive NHP formulations or a negative control. The PVF was measured at week (W) 4 and W8. Daily locomotor activity was recorded using accelerometer. The CSOMs were assessed bi-weekly by the owner. The NHP-treated dogs (n = 13) had higher PVF at W4 (p = 0.020) and W8 (p <0.001) when compared to baseline. The changes at W8 were higher than control dogs (n = 14, p <0.027) and consistent with Cohen's d effect size of 0.7 (95% confidence interval: 0.0-1.5). The NHP-treated dogs had higher locomotor activity at W8 (p = 0.025) when compared to baseline. No significant change was observed for the CSOM. The NHP improved the clinical signs of osteoarthritis in this model.

Association between sensitisation and pain-related behaviours in an experimental canine model of osteoarthritis.

Evaluation of nociceptive sensitisation in canine osteoarthritis studies has been poorly reported, or even related to other clinical symptoms. In 16 dogs, peak vertical force (PVF), subjective pain assessment using 3 scales, sympathetic stress response with electrodermal activity (EDA) measurement, and behavioural changes with video analysis and telemetered motor activity were quantified at baseline (D-7), and 28 and 56 days post transection of the cranial cruciate ligament. As markers of central sensitisation, selected spinal cord biomarkers (substance P and transthyretin) were quantified at D56. Electrical withdrawal thresholds on the stifle and the tail were measured as indicative of peripheral and central quantitative sensory testing (QST) sensitisation, respectively. The effects of vehicle administration (n=8) were compared with tiludronate (2mg/kg subcutaneously, q2 week, starting at D0) administration. Generalized estimated equations tested the association between the behavioural and physiological methods and QST sensitisation, and therefore the sensitivity of the methods for detecting treatment efficacy. Compared to tiludronate, at D56, vehicle-treated dogs had increased spinal substance P (P=0.01), concomitant decreased transthyretin (P=0.02), and (compared to baseline) demonstrated peripheral and central QST sensitisation, which was not present for tiludronate. Only PVF, the spontaneous behaviour "walking with full weight-bearing," and EDA were associated with occurrence of QST sensitisation and indicated significant tiludronate analgesic efficacy after inclusion of central QST sensitisation as a predictor variable in the statistical model. This study establishes the strong interest to implement QST as a predictor of canine osteoarthritis pain symptoms explained by pain sensitisation.

Effect of a diet enriched with green-lipped mussel on pain behavior and functioning in dogs with clinical osteoarthritis.

This study aimed to establish the effect of a diet enriched with green-lipped mussel (GLM) on pain and functional outcomes in osteoarthritic dogs. Twenty-three client-owned dogs with osteoarthritis (OA) were fed a balanced control diet for 30 d and then a GLM-enriched balanced diet for the next 60 d. We assessed peak vertical force (PVF), which is considered to be the gold standard method, at Day (D)0 (start), D30 (end of control diet), and D90 (end of GLM-enriched diet). The owners completed a client-specific outcome measure (CSOM), which is a pain questionnaire, once a week. Motor activity (MA) was continuously recorded in 7 dogs for 12 wk. Concentrations of plasma omega-3 fatty acids were quantified as indicative of diet change. Statistical analyses were linear-mixed models and multinomial logistic regression for repeated measures. The GLM diet (from D30 to D90) resulted in an increase in concentrations of plasma omega-3 fatty acids (P < 0.016) and improvement of PVF (P = 0.003). From D0 to D30, PVF did not significantly change (P = 0.06), which suggests that the GLM diet had a beneficial effect on gait function. Moreover, PVF (P = 0.0004), CSOM (P = 0.006), and MA (P = 0.02) improved significantly from D0 to D90. In general, the balanced control diet could have contributed to reduced OA symptoms, an effect that was subsequently amplified by the GLM diet.

L'objectif de cette étude était d'établir l'effet d'une diète équilibrée enrichie en moule verte (GLM) avec des évaluations fonctionnelles et de douleur sur des chiens arthrosiques. Vingt-trois chiens arthrosiques de propriétaires (région de Montréal, QC) ont été nourris d'abord avec une diète équilibrée contrôle pendant 30 j., puis avec la diète enrichie en GLM pour les 60 j. suivants. Les évaluations incluaient le pic de force verticale (PFV), considéré comme la méthode étalon, au Jour (J)0 (inclusion), J30 (fin de la diète contrôle) et J90 (fin de la diète GLM). Les propriétaires ont complété de manière hebdomadaire une échelle de mesure spécifique à chaque client (CSOM), qui est un questionnaire de quantification de la douleur. L'activité motrice (AM) a été enregistrée en continu sur 7 chiens pour toute la durée de l'étude (12 sem.). Les concentrations plasmatiques d'acides gras oméga-3 ont été quantifiées en tant que marqueurs de changement de diètes. Les analyses statistiques furent des modèles linéaires-mixtes et une régression logistique multinomiale pour mesures répétées. La diète GLM (de J30 à J90) augmenta les concentrations plasmatiques d'acides gras oméga-3 (P < 0,016) ainsi que le PFV (P = 0,003). De J0 à J30, les changements de PFV furent non-significatifs (P = 0,06), ce qui suggère que la diète GLM a eu un effet thérapeutique sur la fonction biomécanique. De plus, PFV (P = 0,0004), CSOM (P = 0,006) et AM (P = 0,02) s'améliorèrent significativement de J0 à J90. De manière globale, il est possible que la diète équilibrée contrôle ait contribué à améliorer les signes d'arthrose, un effet qui fut amplifié par la suite avec la diète GLM.(Traduit par Docteur Eric Troncy).

Validation of orthopedic postoperative pain assessment methods for dogs: a prospective, blinded, randomized, placebo-controlled study.

In the context of translational research, there is growing interest in studying surgical orthopedic pain management approaches that are common to humans and dogs. The validity of postoperative pain assessment methods is uncertain with regards to responsiveness and the potential interference of analgesia. The hypothesis was that video analysis (as a reference), electrodermal activity, and two subjective pain scales (VAS and 4A-VET) would detect different levels of pain intensity in dogs after a standardized trochleoplasty procedure. In this prospective, blinded, randomized study, postoperative pain was assessed in 25 healthy dogs during a 48-hour time frame (T). Pain was managed with placebo (Group 1, n = 10), preemptive and multimodal analgesia (Group 2, n = 5), or preemptive analgesia consisting in oral tramadol (Group 3, n = 10). Changes over time among groups were analyzed using generalized estimating equations. Multivariate regression tested the significance of relationships between pain scales and video analysis. Video analysis identified that one orthopedic behavior, namely 'Walking with full weight bearing' of the operated leg, decreased more in Group 1 at T24 (indicative of pain), whereas three behaviors indicative of sedation decreased in Group 2 at T24 (all p<0.004). Electrodermal activity was higher in Group 1 than in Groups 2 and 3 until T1 (p<0.0003). The VAS was not responsive. 4A-VET showed divergent results as its orthopedic component (4A-VETleg) detected lower pain in Group 2 until T12 (p<0.0009), but its interactive component (4A-VETbeh) was increased in Group 2 from T12 to T48 (p<0.001). Concurrent validity established that 4A-VETleg scores the painful orthopedic condition accurately and that pain assessment through 4A-VETbeh and VAS was severely biased by the sedative side-effect of the analgesics. Finally, the video analysis offered a concise template for assessment in dogs with acute orthopedic pain. However, subjective pain quantification methods and electrodermal activity need further investigation.

Clinical validity of outcome pain measures in naturally occurring canine osteoarthritis.

BACKGROUND: The conceptual validity of kinetic gait analysis and disability outcome assessment methods has guided their use in the assessment of pain caused by osteoarthritis (OA). No consensus on the best clinical methods for pain evaluation in canine OA exists, particularly, when evaluating treatments where a smaller treatment effect is anticipated than with pharmacological pain killers. This study thus aimed at determining the technical validity of some clinical endpoints on OA pain in dogs using the green-lipped mussel (GLM)-enriched diet.Twenty-three adult dogs with clinical OA completed the prospective controlled study. All the dogs were fed a balanced diet over a 30-day control period followed by a GLM-enriched diet over a 60-day period. The kinetic gait analysis parameter (PVF(BW), peak vertical force adjusted for body weight change), electrodermal activity (EDA), and a standardized multifactorial pain questionnaire (MFQ) were performed on day (D) 0 (inclusion), D30 (start) and D90 (end). The owners completed a client-specific outcome measures (CSOM) instrument twice a week. Motor activity (MA) was continuously recorded in seven dogs using telemetered accelerometric counts. We hypothesized that these methods would produce convergent results related to diet changes. A Type I error of 0.05 was adjusted to correct for the multiplicity of the primary clinical endpoints. RESULTS: Neither the EDA nor the MFQ were found reliable or could be validated. Changes in the PVFBW (P(adj) = 0.0004), the CSOM (P(adj) = 0.006) and the MA intensity (P(adj) = 0.02) from D0 to D90 suggested an effect of diet(s). Only the PVFBW clearly increased after the GLM-diet (P(adj) = 0.003). The CSOM exhibited a negative relationship with the PVF(BW) (P = 0.02) and MA duration (P = 0.02). CONCLUSIONS: The PVF(BW) exhibited the best technical validity for the characterization of the beneficial effect of a GLM-enriched diet. The CSOM and MA appeared less responsive following a GLM-diet, but these measures appeared complementary to gait analysis. Apparently, the CSOM provides the capacity to rely on pain OA assessment influenced by both lameness quantification (PVF(BW)) and physical functioning (MA).

Brachystemma calycinum D. Don Effectively Reduces the Locomotor Disability in Dogs with Naturally Occurring Osteoarthritis: A Randomized Placebo-Controlled Trial.

Objective. The aim of this randomized placebo-controlled trial was to evaluate the beneficial effect of a whole plant extract of Brachystemma calycinum D. Don (BCD) in naturally occurring osteoarthritis (OA) in dogs. Methods. Dogs had stifle/hip OA and poor limb loading based on the peak of the vertically oriented ground reaction force (PVF) measured using a force platform. At baseline, PVF and case-specific outcome measure of disability (CSOM) were recorded. Dogs (16 per group) were then assigned to receive BCD (200 mg/kg/day) or a placebo. The PVF was measured at week (W) 3 and W6. Locomotor activity was recorded throughout the study duration using collar-mounted accelerometer, and CSOM was assessed biweekly by the owner. Results. BCD-treated dogs had higher PVF at W3 and W6 when compared to Baseline (P < 0.001) and at W6 when compared to placebo-treated dogs (P = 0.040). Higher daily duration (P = 0.024) and intensity (P = 0.012) of locomotor activity were observed in BCD-treated dogs compared to baseline. No significant change was observed in either group for CSOM. Conclusions. Treatment with BCD improved the limb impairment and enhanced the locomotor activity in dogs afflicted by naturally-occurring OA. Those preclinical findings provide interesting and new information about the potential of BCD as an OA therapeutic.

Measurements of canine aqueous humor inflammatory mediators and the effect of carprofen following anterior chamber paracentesis.

OBJECTIVES: Phase I: To evaluate levels of prostaglandin E(2) (PGE(2) ), nitrites and nitrates (NO(x) ), tumor necrosis factor-alpha (TNF-α) and expression of inducible cyclo-oxygenase (COX-2), nitric oxide synthase (NOS-2), and matrix metalloproteinases (MMP-3 and -9) in canine aqueous humor following repeated anterior chamber paracenteses (ACP). Phase II: to evaluate the effect of carprofen on PGE(2) , NO(x) , and TNF-α in canine aqueous humor following ACP. ANIMALS STUDIED: Four beagles in phase I and 8 beagles in phase II. PROCEDURES: Phase I: ACP was performed at time (T) 0, 4 and 8 h. Phase II: A randomized, placebo-controlled cross-over design with four dogs per group where carprofen was given 4.4 mg/kg/day on day (D) 1, 2 and 3. ACP was performed at T0 and T1.5 on D3. Statistical analysis was performed with repeated measures anova and post hoc Tukey-Kramer multiple-comparison procedure. In phase II, TNF-α level was analyzed with a Wilcoxon signed-rank test. RESULTS: Phase I: PGE(2) significantly increased (P < 0.0001) to plateau at T4. NO(X) was decreased at T4 (P < 0.06), but increased at T8 (P < 0.0001). COX-2 showed detectable expression only at T8. TNF-α, NOS-2, MMP-3 and -9 were undetectable at all time points. Phase II: At T1.5, PGE(2) was significantly elevated in both groups but was lower in the carprofen group (P = 0.037). NO(x) and TNF-α did not statistically increase in either group. CONCLUSIONS: Following ACP, significant increases in PGE(2) levels confirmed inflammation characterized by a rise of COX-2. The NO(x) pathway took longer to induce as compared with PGE(2) . Carprofen decreased PGE(2) levels and could help control intraocular inflammation.

Tiludronate treatment improves structural changes and symptoms of osteoarthritis in the canine anterior cruciate ligament model.

INTRODUCTION: The aim of this prospective, randomized, controlled, double-blind study was to evaluate the effects of tiludronate (TLN), a bisphosphonate, on structural, biochemical and molecular changes and function in an experimental dog model of osteoarthritis (OA). METHODS: Baseline values were established the week preceding surgical transection of the right cranial/anterior cruciate ligament, with eight dogs serving as OA placebo controls and eight others receiving four TLN injections (2 mg/kg subcutaneously) at two-week intervals starting the day of surgery for eight weeks. At baseline, Week 4 and Week 8, the functional outcome was evaluated using kinetic gait analysis, telemetered locomotor actimetry and video-automated behaviour capture. Pain impairment was assessed using a composite numerical rating scale (NRS), a visual analog scale, and electrodermal activity (EDA). At necropsy (Week 8), macroscopic and histomorphological analyses of synovium, cartilage and subchondral bone of the femoral condyles and tibial plateaus were assessed. Immunohistochemistry of cartilage (matrix metalloproteinase (MMP)-1, MMP-13, and a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS5)) and subchondral bone (cathepsin K) was performed. Synovial fluid was analyzed for inflammatory (PGE(2) and nitrite/nitrate levels) biomarkers. Statistical analyses (mixed and generalized linear models) were performed with an α-threshold of 0.05. RESULTS: A better functional outcome was observed in TLN dogs than OA placebo controls. Hence, TLN dogs had lower gait disability (P = 0.04 at Week 8) and NRS score (P = 0.03, group effect), and demonstrated behaviours of painless condition with the video-capture (P < 0.04). Dogs treated with TLN demonstrated a trend toward improved actimetry and less pain according to EDA. Macroscopically, both groups had similar level of morphometric lesions, TLN-treated dogs having less joint effusion (P = 0.01), reduced synovial fluid levels of PGE(2) (P = 0.02), nitrites/nitrates (P = 0.01), lower synovitis score (P < 0.01) and a greater subchondral bone surface (P < 0.01). Immunohistochemical staining revealed lower levels in TLN-treated dogs of MMP-13 (P = 0.02), ADAMTS5 (P = 0.02) in cartilage and cathepsin K (P = 0.02) in subchondral bone. CONCLUSION: Tiludronate treatment demonstrated a positive effect on gait disability and joint symptoms. This is likely related to the positive influence of the treatment at improving some OA structural changes and reducing the synthesis of catabolic and inflammatory mediators.

Respiratory safety pharmacology: concurrent validation of volume, rate, time, flow and ratio variables in conscious male Sprague-Dawley rats.

This study compares basic respiratory variables (rate, tidal and minute volumes) with time-, flow- and ratio-derived parameters obtained using head-out plethysmography in rats following administration of reference drugs (isotonic saline, 2.0 mL/kg, IV; albuterol, 400 µg/kg, inhalation; methacholine, 136 µg/kg, IV; and remifentanil, 14 µg/kg, IV) to identify respiratory variables with superior sensitivity. Paired t-tests by block-period, and analysis of covariance (ANCOVA) with baseline as covariate and a posteriori pair-wise comparisons using Dunnett's test were used. Variations in respiratory parameters observed over time justify the use of a control group in any respiratory safety pharmacology study for inter-groups comparison. Handling-, and slumbering-, induced perturbations were minimal. The system was sensitive and specific to detect changes in respiratory variables related to pharmacologically-induced bronchodilation, bronchoconstriction and central respiratory depression. The standard variables (respiratory rate, tidal and minute volumes) confirmed to be the cornerstone of respiratory safety pharmacology to detect pharmacological changes. Flow-derived parameters appeared as highly valuable complement for interpretation of respiratory response, whereas time- and ratio-derived parameters presented limited added value during interpretation.

Cardiovascular effects of oxytocin infusion in a porcine model of myocardial infarct.

The effects of oxytocin (OT) on cardiovascular endpoints were assessed in a myocardial infarct (MI) model. OT (10 ng.kg(-1).hour(-1)) or saline infusion was initiated at reperfusion (D0) or 8 days (D8) after MI. Our hypothesis was that OT administration to individuals with a low pretreatment OT levels (PTOT) may be beneficial, whereas individuals with an elevated PTOT would be prone to adverse effects. Starting OT on D0 reduced left ventricular fraction shortening evaluated 8 days post MI and had no effect on infarct size. OT initiated on D8 in animals with high PTOT decreased ejection fraction (EF) and increased left ventricular end-systolic diameter at 28 days post MI but had no significant effects on EF and left ventricular end-systolic diameter in low PTOT animals. OT infusion reduced OT receptor protein expression in high PTOT animals but not in low PTOT animals. Among placebo-treated individuals, low PTOT presented a trend toward reduced EF and larger infarct size compared with high PTOT. MI areas of fibrosis presented lower Annexin V expression compared with MI with cardiomyocyte predominance. Pretreatment endogenous OT levels and timing of OT administration post MI seem to impact outcome in this porcine model, and further investigations are warranted to define potential role of OT in cardiac regenerative therapy.

Respiratory safety pharmacology: positive control drug responses in Sprague-Dawley rats, Beagle dogs and cynomolgus monkeys.

Rats are most frequently used to fulfill ICH S7A requirements for respiratory safety pharmacology. We hypothesized that the models used to assess respiratory safety pharmacology present different ventilatory responses to bronchoconstriction, bronchodilation and respiratory depression. Respiratory monitoring was performed with head-out plethysmographs for rats, masks for dogs and bias airflow helmets for monkeys. Respiratory rate (RR), tidal volume (TV) and minute volume (MV) were recorded. Forty rats, 18 dogs and 8 monkeys were acclimated to the respiratory monitoring equipment. Animals received saline (IV), albuterol (inhalation), methacholine (IV) and remifentanil (IV). Albuterol increased TV in all species. Methacholine decreased TV and MV in monkeys. In dogs, methacholine increased TV, RR and MV. In rats, methacholine increased TV and decreased RR. Remifentanil induced central respiratory depression in all species with decreased MV, except in rats. Dogs presented a biphasic response to remifentanil with hypoventilation followed by delayed hyperventilation. The monkeys presented similar responses to humans which may be due to biologic similarities. Dogs and rats presented clinically significant ventilatory alterations following positive control drugs. Although, the response to bronchoconstriction in dogs and rats was different from humans, the two species presented ventilatory changes that highlight the potential adverse effect of test articles.

Determination of glomerular filtration rate in anesthetized pigs by use of three-phase whole-kidney computed tomography and Patlak plot analysis.

OBJECTIVE: To develop a whole-kidney computed tomography (CT) technique that would allow 3-point Patlak plot determination of glomular filtration rate (GFR) and assess the correlation of GFR determined via CT (CT-GFR) with GFR determined via renal plasma clearance of inulin (Inu-GFR) in pigs. ANIMALS: 6 healthy anesthetized pigs. PROCEDURES: Each pig underwent 3-phase whole-kidney helical CT (arterial, early, and late parenchymal phases) before and after contrast medium administration. After contrast medium administration, corrected Hounsfield unit values were determined for each kidney and the aorta. A 3-point Patlak plot for each kidney was generated, and plasma clearance per unit volume was multiplied by renal volume to obtain whole-animal CT-GFR. Correlations of mean Inu-GFR for the left and right kidneys (and combined [total] values) with the corresponding CT-GFRs were assessed via linear regression and Bland-Altman analyses. RESULTS: Left kidney, right kidney, and total CT-GFRs were good predictors of the respective Inu-GFR values (r(2) = 92.3%, r(2) = 85.5%, and r(2) = 93.7%, respectively). For the left kidney, no significant bias between Inu-GFR and CT-GFR was detected. Right kidney and total CT-GFRs underestimated the corresponding Inu-GFRs (mean underestimation, -8.4 mL*min(1) and -12.6 mL*min(1), respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Three-phase whole-kidney CT with Patlak plot analysis of GFR may underestimate right kidney and total Inu-GFRs in pigs. The Patlak plot generated may be sensitive to nonlinearity caused by temporal variation in GFR. Nonetheless, the 3-phase CT approach offers some practical advantages for simultaneous evaluation of renal morphology and measurement of GFR.

Renal effect of meloxicam versus ketoprofen in anaesthetized pseudo-normovolaemic piglets.

Due to renal COX-2 constitutive expression, meloxicam is presumably deleterious for kidney function in critical situations. The present study investigates the influence of intravenous meloxicam on renal parameters and compares it with a nonselective COX inhibitor, ketoprofen. Piglets (n = 6 in each group) were treated with ketoprofen (2 mg.kg(-1)), meloxicam (0.2 mg.kg(-1)), or saline at the beginning of anaesthesia. Under intravenous anaesthesia, pigs were instrumented for cardiovascular, respiratory, and renal function evaluation, including urinary flow (UF), glomerular filtration rate (GFR), and renal blood flow (RBF). After baseline data collection (U0), data collection consisted of six 20-minute periods (U1 to U6). In all groups, the time course of cardiovascular and respiratory parameters remained within normal ranges. A small decrease in cardiac output and an increase in mean systemic arterial blood pressure (p = 0.002) occurred in all groups. In the placebo group, a similar decrease was observed for RBF and cardiac output, with troughs of -10.1% +/- 6.8%, and -12.9% +/- 3.2%, respectively. GFR and UF, however, remained stable over time in this group. Ketoprofen significantly decreased UF (-29.3% +/- 5.5% max at U3), with similar decreases in GFR and RBF. Meloxicam induced a transient (at U2) and small decrease in UF with no difference, at any time point, with the placebo group. The renal effects of meloxicam appear minimal and transient in anaesthetized piglets. This study demonstrates the safety of meloxicam for preemptive surgical analgesia under conditions of normovolaemia. Fluid therapy appears recommended to prevent any renal dysfunction.

Validation of respiratory safety pharmacology models: conscious and anesthetized beagle dogs.

INTRODUCTION: Installation, operation and performance qualifications were performed on a test system for respiratory monitoring. METHODS: For performance qualification, conscious dogs received saline (0.2 mL/kg, iv, n=12), albuterol (100 microg/kg, inhalation, n=5), methacholine (2.0 and 8.0 microg/kg, iv, n=8) and remifentanil (4.0 microg/kg, iv, n=7). Following anesthesia with propofol infusion, dogs received saline (iv, n=15), albuterol (100 microg/kg, inhalation, n=8), methacholine (8.0 microg/kg, iv, n=8), remifentanil (4.0 microg/kg, iv, n=7), and cholecystokinine tetrapeptide (CCK-4) (10 microg/kg, iv, n=7) and were exposed to hypoxic gas mixture (10% oxygen) (n=12). RESULTS: Saline had no significant respiratory effect. Albuterol increased tidal volume (TV) (+28%, p<0.05) and minute ventilation (MV) (+96%, p<0.01) in conscious dogs. In anesthetized dogs, MV was significantly increased (+23%, p<0.05) but the difference was not statistically significant for TV and respiratory rate (RR). Methacholine at 2.0 microg/kg increased MV (+45%, p<0.01) in conscious animals while 8.0 microg/kg increased RR (+66%, p<0.01), TV (+24%, p<0.05) and MV (+88%, p<0.05). In anesthetized dogs, methacholine increased RR (+51%, p<0.05), MV (+34%, p<0.05), lung elastance (+36.9%, p<0.01), and resistance (+45.8%, p<0.01). Remifentanil decreased MV in conscious dogs (-68%, p<0.01) while transient apnea was observed in all anesthetized dogs. CCK-4 increased RR (+328%, p<0.01) and MV (+127%, p<0.05) and decreased TV (-58%, p<0.01). Exposure to hypoxic gas mixture increased MV and RR (p<0.01). Baseline MV was lower (p<0.05) in anesthetized than in conscious dogs. DISCUSSION: Arterial blood gas values, particularly SaO(2), presented a limited sensitivity to detect any ventilation disturbance, but allowed confirmation of both ventilatory compensatory phenomenon (when present) and initial pharmacologic drug effect. These results also highlight the greater sensitivity of the conscious model when compared to anesthetized dogs.

Evidence for non-linear pharmacokinetics of oxytocin in anesthetizetized rat.

PURPOSE: Because oxytocin (OT) is potentially useful in cardiovascular therapy but has hormonal roles on the cardiovascular and renal systems, we characterized its pharmacokinetic (PK) properties as a function of dose. METHODS: A single intravenous bolus of OT was given at doses of 200, 300, 500, 1000, 3000, 5000 and 10000 ng/kg to anesthetized male rats (n >= 4 per dose). Blood samples (6) were taken over 72 min to 150 min, depending on dose. The individual time-courses of plasma OT concentrations were analyzed with a one- or an open two-compartment PK model. Kruskal-Wallis tests (alpha=0.05) were used to compare the PK parameters among groups. RESULTS: At doses up to 500 ng/kg, OT showed a higher median systemic clearance (CLT = 0.0624 L/(min*kg); 0.0622 +/- 0.0228 as mean +/- SD value), a higher median central compartment volume of distribution (VC = 0.7906 L/kg; 0.6961 +/- 0.1754), and a lower median elimination half life (t(1/2)(lambdaz) 7.94 min; 9.08 +/- 4.3) with respect to the higher doses (CLT = 0.0266 L/(min*kg); 0.0284 +/- 0.0098, VC = 0.2213 L/kg; 0.2227 +/- 0.1142, and t(1/2)(lambdaz) 21.09 min; 28.36 +/- 21.8), all differences being significant (p 0.0008). Minimal differences were found for the estimates of these PK parameters among the 4 higher OT doses. CONCLUSION: The PK properties and persistence of exogenous OT are not proportional to dose, therefore this must be accounted for in dosing regimen design for potential cardiovascular therapy.

A cardiovascular monitoring system in conscious cynomolgus monkeys for regulatory safety pharmacology. Part 1: Non-pharmacological validation.

INTRODUCTION: This project addresses the validation study design of a test system using a telemetered non-human primate model for cardiovascular safety pharmacology evaluation. METHODS: The validation provided by the supplier evaluated installation (IQ) and operation (OQ) qualifications. This protocol was completed with tests evaluating electronic data management and accuracy and precision of transmitter (n=4) measurements for temperature and pressure criteria with a series of tested values. As part of performance qualification, physical activity (for 24 h) as well as cardiovascular, ECG (20 complexes for each animal) and systemic arterial blood pressure (SAP, 10 different measures), data were recorded simultaneously from the same animals (n=4) using certified equipment and the telemetry system. Reliability was evaluated over 60 days. RESULTS: The IQ and OQ were completed successfully. The electronic data management was performed successfully. The ex-vivo evaluation for temperature and pressure showed high correlation (R(2)>0.99) but with a slight pressure shift, as expected, with this transmitter model. For physical activity, the correlation coefficients were good to excellent with high activity counts but the comparison demonstrated a limited sensitivity of the telemetry system with animal presenting low activity levels. ECG interval measurement using the telemetry software was considered at least equivalent to manual measurement, but with some limitations in the reading of the ECG. The comparison between both methods of SAP measurement showed adequate precision (R(2)=0.969) but no accuracy. DISCUSSION: Reference monitoring methods are important to ensure proper test system validation. Monitoring with a reference methodology and the telemetry system is important in order to evaluate precision and accuracy of the test system. Computerized analysis may lack the capability to analyze ECG complexes with abnormal morphologies. This reinforces the need to have ECG evaluation prior to telemetry implantation along with visual evaluation of ECG tracing at standard speed (e.g. 50 mm/s) at all time points.