Evaluation of tumescent local anesthesia in cats undergoing unilateral mastectomy.

OBJECTIVE: To evaluate the analgesic efficacy and safety of tumescent local anesthesia (TLA) in cats undergoing unilateral mastectomy. STUDY DESIGN: Prospective clinical trial. ANIMALS: A total of 12 ovariohysterectomized female cats. METHODS: All animals were premedicated with pethidine (4 mg kg-1) intramuscularly (IM), followed by induction of anesthesia with propofol (5 mg kg-1) intravenously and maintenance with isoflurane in oxygen. A refrigerated TLA solution (15 mL kg-1, 8 °C) was injected using a Klein cannula. The solution was composed of 0.5 mL of epinephrine (1 mg mL-1) and 40 mL of 2% lidocaine added to 210 mL lactated Ringer's solution (final lidocaine concentration 0.32%). Heart and respiratory rates, systolic arterial blood pressure, temperature and oxygen saturation were measured during anesthesia. Blood samples were collected from the jugular vein for measurement of plasma lidocaine concentration using high performance liquid chromatography. Postoperative pain scores were evaluated hourly for 6 hours. Analgesic rescue was performed with tramadol (2 mg kg-1) IM and meloxicam (0.15 mg kg-1) subcutaneously. RESULTS: Plasma lidocaine concentration peaked at 90 minutes after injection of TLA, but no concentration considered toxic for the species was measured. The median postoperative analgesia time was 6 hours after injection of TLA. CONCLUSIONS: This study found that TLA prevented sympathetic response to noxious stimuli during anesthesia and provided satisfactory postoperative analgesia in cats submitted to total unilateral mastectomy, with no apparent signs of toxicity. CLINICAL RELEVANCE: TLA can prevent sympathetic stimulation resulting from noxious stimuli during anesthesia, promoting good intraoperative conditions, proving to be a viable addition to analgesia in cats submitted to a total unilateral mastectomy.

Preliminary survey of the attitudes of Brazilian scientists towards pain management and assessment in animals used in science.

OBJECTIVE: To investigate the current scenario in Brazil regarding pain assessment and control in experimental animals. STUDY DESIGN: Prospective survey. METHODS: A confidential questionnaire was available online and sent by e-mail to Brazilian scientists working with animal experimentation in Brazil. Data collection was conducted from October 2016 to October 2017. The exclusion criteria included blank questionnaires or with <80% completed responses, researchers not performing experiments involving animals and foreign scientists. RESULTS: A total of 96 questionnaires from 104 respondents were analyzed. The Fisher's exact test showed a disparity between the proportions of scientists who recognized the importance of analgesia and their application of analgesic techniques in painful procedures (p < 0.0003), and also for the researchers who assumed that experiments inflicted pain and their classification of the degree of invasiveness (p < 0.0001), indicating their insufficient knowledge of these topics. Overall, 77% of institutions did not offer specific training to assess pain in experimental animals, and 24% of respondents had no training to work with animal experimentation. In total, 62% of the studies inflicted pain, 48% of respondents used pain scales, and the drugs administered most frequently for pain management were morphine (44%), meloxicam (43%) and tramadol (37%); 15% of respondents did not include analgesics even though their studies inflicted pain. Commonly used animals were rats (33%), mice (29%) and rabbits (8%). CONCLUSIONS AND CLINICAL RELEVANCE: The results of this preliminary survey indicated that in Brazil there is a gap in the knowledge and training on pain assessment and management of experimental animals. Therefore, there is a necessity for an educational program to prepare and train scientists to assess and manage pain in laboratory or experimental animals. Further studies using a psychometrically validated survey instrument are warranted.

Clinical applicability of detomidine and methadone constant rate infusions for surgery in standing horses.

OBJECTIVE: To determine the required rate of a detomidine infusion (loading dose 5 µg kg-1; initial rate 12.5 µg kg-1 hour-1) added to a constant infusion of methadone (0.2 mg kg-1; 0.05 mg kg-1 hour-1) for sedation in standing horses and ponies undergoing elective surgeries with appropriate local anaesthetic techniques. STUDY DESIGN: Prospective, clinical study. ANIMALS: Adult, healthy, client-owned, non-food-producing horses or ponies sedated for elective standing surgeries longer than 45 minutes. METHODS: At baseline (in the stables before administration of sedative agents), at 10 minutes after sedation and every 5 minutes thereafter, ataxia, sedation and surgical condition were evaluated; each scored 0-3. These scores were used to adjust the detomidine administration rate using the Ghent Sedation Algorithm. A 10 cm visual analogue scale (VAS) was used by the main surgeon at the end of the procedure to evaluate the surgical conditions. Heart rate, systolic arterial pressure and respiratory frequency were also recorded at each time point. For statistical analysis, anova for normal, Kruskal-Wallis H-test for non-normal variables, and Mann-Whitney U test for VAS were used. RESULTS: From the 42 horses/ponies included in this study, 28 underwent dental procedures and 14 other types of procedures. Overall, dental procedures required higher mean detomidine rates compared with other types of surgeries (16.9 ± 4.5 versus 9.0 ± 1.9 µg kg-1 hour-1) (p < 0.001). Dental procedures were assigned similar VAS scores, median (range), of 7.8 (5.8-10) with other procedures, 8.7 (2.8-10). Cardiovascular changes were not clinically significant. No signs or behavioural changes of abdominal pain were observed postoperatively. CONCLUSIONS AND CLINICAL RELEVANCE: Satisfactory surgical conditions were achieved using a combination of detomidine and methadone infusions with locoregional anaesthesia, with no adverse effects. Dental procedures required higher detomidine dose rates compared with other surgeries.

Sedative and antinociceptive effects of different combinations of detomidine and methadone in standing horses.

OBJECTIVE: To evaluate intravenous (IV) detomidine with methadone in horses to identify a combination which provides sedation and antinociception without adverse effects. STUDY DESIGN: Randomized, placebo-controlled, blinded, crossover. ANIMALS: A group of eight adult healthy horses aged (mean ± standard deviation) 7 ± 2 years and 372 ± 27 kg. METHODS: A total of six treatments were administered IV: saline (SAL); detomidine (5 µg kg-1; DET); methadone (0.2 mg kg-1; MET) alone or combined with detomidine [2.5 (MLD), 5 (MMD) or 10 (MHD) µg kg-1]. Thermal, mechanical and electrical nociceptive thresholds were measured, and sedation, head height above ground (HHAG), cardiopulmonary variables and intestinal motility were evaluated at 5, 15, 30, 45, 60, 75, 90, 120 and 180 minutes. Normal data were analyzed by mixed-model analysis of variance and non-normal by Kruskal-Wallis (p < 0.05). RESULTS: Nociceptive thresholds in horses administered methadone with the higher doses of detomidine (MMD, MHD) were increased above baseline to a greater degree and for longer duration (MMD: 15-30 minutes, MHD: 30-60 minutes) than in horses administered low dose with methadone or detomidine alone (MLD, DET: 5-15 minutes). No increases in nociceptive thresholds were recorded in SAL or MET. Compared with baseline, HHAG was lower for 30 minutes in MMD and DET, and for 45 minutes in MHD. No significant sedation was observed in SAL, MET or MLD. Intestinal motility was reduced for 75 minutes in MHD and for 30 minutes in all other treatments. CONCLUSIONS: Methadone (0.2 mg kg-1) potentiated the antinociception produced by detomidine (5 µg kg-1), with minimal sedative effects. CLINICAL RELEVANCE: Detomidine (5 µg kg-1) with methadone (0.2 mg kg-1) produced antinociception without the adverse effects of higher doses of detomidine.

Anesthetic effects of different volumes of lidocaine for spermatic cord block in cattle.

OBJECTIVE: To evaluate three volumes of lidocaine for spermatic cord block to perform castration in cattle. STUDY DESIGN: Randomized blinded clinical study. ANIMALS: Thirty mixed-breed Nellore cattle, aged 28-40 months and weighing 395±21 (352-452) kg [mean±standard deviation (range)]. METHODS: Cattle were restrained in a chute and allowed to stand without sedation. Three milliliters of 2% lidocaine without epinephrine were infiltrated subcutaneously at each site of scrotal incision in all animals. The animals were allocated to three groups of 10 animals each. Lidocaine 2% was injected into each spermatic cord using a volume of 2, 3 or 4 mL in groups A, B, or C, respectively. The total volumes of lidocaine used were 10, 12, and 14 mL in groups A, B, and C, respectively. The duration of surgery and the retraction of the testicle (scored as positive or negative according to retraction of the testicle) during the procedure were recorded. The data were statistically analyzed by one-way anova followed by Tukey's and chi-square tests. Differences were considered significant when p<0.05. RESULTS: The mean surgical time was shorter in group C than in groups A and B (p<0.001). In groups A, B and C, 90%, 60% and 10% of the animals showed retraction of the testicle, respectively. Fewer animals retracted the spermatic cord in group C than in group A (p=0.002) and B (p=0.02). CONCLUSIONS AND CLINICAL RELEVANCE: Optimal spermatic cord block was achieved by injection of 4 mL of 2% lidocaine 5 minutes before castration and following incisional infiltration of lidocaine, in adult cattle weighing about 400 kg.

Continuous infusion of propofol in dogs premedicated with methotrimeprazine.

OBJECTIVE: To evaluate the cardiopulmonary and clinical effects of three different infusion rates of propofol in dogs premedicated with methotrimeprazine. STUDY DESIGN: Randomized experimental trial. ANIMALS: Ten healthy adult mixed-breed male and female dogs, weighing from 14 to 20 kg. METHODS: Dogs were premedicated with methotrimeprazine [1 mg kg-1 intravenously (IV)] followed by induction of anesthesia with 4.5 mg kg-1 of propofol IV and maintenance with propofol for 60 minutes as follows: T1, 0.2 mg kg-1 minute-1; T2, 0.3 mg kg-1minute-1; and T3, 0.4 mg kg-1minute-1. Heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP), end-tidal CO2 (PETCO2), arterial hemoglobin O2 saturation, arterial blood gases, and pedal and cutaneous reflexes were measured before and 5, 10, 20, 30, 45 and 60 minutes after the beginning of the propofol infusion. Statistical analysis was performed using an anova. RESULTS: Heart rate increased during anesthesia in all cases and arterial blood pressure decreased only in dogs in the T3 category. Respiratory depression was proportional to the infusion rate of propofol. Muscle relaxation was satisfactory, but analgesia was inadequate in the three treatments. CONCLUSIONS: The infusion of 0.2-0.4 mg kg-1 minute-1 of propofol produced a dose-dependent respiratory depression. The presence of a pedal withdrawal reflex and marked cardiovascular responses to this noxious stimulus suggests that anesthesia may not be of sufficient depth for surgery to be carried out. CLINICAL RELEVANCE: Although several studies have been performed using propofol in animals, few studies have investigated the cardiopulmonary and analgesic effects with different doses. The determination of an adequate propofol infusion rate is necessary for the routine use of this intravenous anesthetic for the maintenance of anesthesia during major surgical procedures in dogs.

Intravenous anaesthesia using detomidine, ketamine and guaiphenesin for laparotomy in pregnant pony mares.

Objective To characterize intravenous anaesthesia with detomidine, ketamine and guaiphenesin in pregnant ponies. Animals Twelve pony mares, at 260-320 days gestation undergoing abdominal surgery to implant fetal and maternal vascular catheters. Materials and methods Pre-anaesthetic medication with intravenous (IV) acepromazine (30 µg kg-1), butorphanol (20 µg kg-1) and detomidine (10 µg kg-1) preceded induction of anaesthesia with detomidine (10 µg kg-1) and ketamine (2 mg kg-1) IV Maternal arterial blood pressure was measured directly throughout anaesthesia and arterial blood samples were taken at 20-minute intervals for measurement of blood gases and plasma concentrations of cortisol, glucose and lactate. Anaesthesia was maintained with an IV infusion of detomidine (0.04 mg mL-1), ketamine (4 mg mL-1) and guaiphenesin (100 mg mL-1) (DKG) for 140 minutes. Oxygen was supplied by intermittent positive pressure ventilation (IPPV) adjusted to maintain PaCO2 between 5.0 and 6.0 kPa (38 and 45 mm Hg), while PaO2 was kept close to 20.0 kPa (150 mm Hg) by adding nitrous oxide. Simultaneous fetal and maternal blood samples were withdrawn at 90 minutes. Recovery quality was assessed. Results DKG was infused at 0.67 ± 0.17 mL kg-1 hour-1 for 1 hour then reduced, reaching 0.28 ± 0.14 mL kg-1 hour-1 at 140 minutes. Arterial blood gas values and pH remained within intended limits. During anaesthesia there was no change in heart rate, but arterial blood pressure decreased by 10%. Plasma glucose and lactate increased (10-fold and 2-fold, respectively) and cortisol decreased by 50% during anaesthesia. Fetal umbilical venous pH, PO2 and PCO2 were 7.34 ± 0.06, 5.8 ± 0.9 kPa (44 ± 7 mm Hg) and 6.7 ± 0.8 kPa (50 ± 6 mm Hg); and fetal arterial pH, PO2 and PCO2 were 7.29 ± 0.06, 4.0 ± 0.7 kPa (30 ± 5 mm Hg) and 7.8 ± 1.7 kPa (59 ± 13 mm Hg), respectively. Surgical conditions were good but four ponies required a single additional dose of ketamine. Ponies took 60 ± 28 minutes to stand and recovery was good. Conclusions and clinical relevance Anaesthesia produced with DKG was smooth while cardiovascular function in mare and fetus was well preserved. This indicates that DKG infusion is suitable for maintenance of anaesthesia in pregnant equidae.