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Trap-neuter-return programs have become a popular nonlethal alternative for the control of feral cat populations. The anesthetic used is an integral component of these programs. This study evaluated the use of tiletamine–zolazepam–ketamine–xylazine (TKX) as an IM anesthetic combination for large-scale feral cat sterilization surgery. Between July 1996 and August 2000, a total of 7502 cats entered large-scale feral cat clinics operating at the Colleges of Veterinary Medicine at North Carolina State University and the University of Florida. Up to 12 surgeries were performed simultaneously and up to 200 cats were sterilized in a single day. Cats were not weighed prior to anesthetic injection owing to their feral nature, so the initial anesthetic dose was based on estimated body weight. Tiletamine–zolazepam–ketamine–xylazine was administered IM while cats remained in their traps. Each milliliter of TKX contained 50 mg tiletamine, 50 mg zolazepam, 80 mg ketamine, and 20 mg xylazine. The cats were monitored by observation and palpation for mucous membrane color, heart rate, and respiratory rate, but these values were not recorded. Fluids were not routinely administered but were given subcutaneously in cases of dehydration or excessive blood loss. Yohimbine (0.5 mg) was administered IV at the end of the procedure, and cats were returned to their traps to recover. Cat signalment, drug use, and mortality data were analyzed retrospectively (July 1996–December 1999) and prospectively (December 1999–August 2000). Of those cats with complete drug records, more than 75% received a single dose of TKX with a mean total dose of 0.27 ± 0.09 mL. The overall mortality rate was one in 289 cats (0.347%) and the death rate owing to unknown causes (potential anesthetic deaths) was one in 469 cats (0.213%). These results suggest that the use of TKX for large-scale feral cat sterilization clinics has several benefits,... [ABSTRACT FROM AUTHOR]

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to provide analgesia in clinical veterinary medicine, but there are few objective data evaluating this effect under controlled conditions in cats. Analgesia is more difficult to detect with acute analgesiometry after NSAIDs than after opioids. This investigation aimed to adapt the feline thermal analgesiometry method previously employed with opioids (Dixon et al. 2002) for use with NSAIDs. Ketoprofen, a COX1 inhibitor licensed for cats was chosen. Six cats (2 neutered, four entire females, weighing 2.2–5.4 kg) were studied in two blinded randomized crossover trials each at least 2 weeks apart. Thermal thresholds (TT) were measured using the thermal threshold-testing device previously developed for cats. A heater element and temperature sensor in a small probe were held at constant pressure against the cats' shaved thorax with an elasticized band. Skin temperature was recorded before each test, then the heater activated. When the cat responded by flinching, turning or jumping the heater was turned off and the temperature recorded. In the first study TT were measured following subcutaneous (SC) injection of ketoprofen (2 mg kg-1 ) or a similar volume of saline. In the second study, prior to TT, and under isoflurane restraint, a mild inflammatory focus was produced at the probe site by five SC injections of 5 mg kaolin in 0.1 mL saline at each corner and in the center of a 1.5-cm square. Saline or ketoprofen as in the first study were injected at the same time. Three baseline temperatures were recorded before any injections were given. Thermal thresholds were measured at 1 and 2 hours and then two-hourly for 24 hours. Data were analysed using anova. Baseline skin temperature increased (37.3 ± 0.5–38.1 ± 0.8 °C) 24 hours after saline injection in study 2 (p < 0.05) but did not change after any other treatment. Thermal thresholds decreased (40.0 ± 1.3 to 39.1 ± 0.4 °C) 16 hours after ketoprofen in study 1 (p < 0.05) and increased (41.6 ± 1.5–44.8 ± 6.1 °C) 16–24 hours after ketoprofen in study 2 (p < 0.05), with no significant changes after saline. No obvious increase in sensitivity to thermal stimulation after kaolin injection was detected although obvious inflammation was present for up to 36 hours and the cats responded to digital pressure at the treated site. The method detected some effects of a COX1 selective NSAID and may be suitable for future NSAID studies in cats. However, a pressure stimulus (Dixon et al. 2000) may prove better than thermal, and it requires investigation. [ABSTRACT FROM AUTHOR]

Many cats do not receive analgesics for treatment of perioperative pain, but when they do, the opioid agonist–antagonist butorphanol (B) is widely used. B is reported to provide long-lasting visceral analgesia, but its somatic actions are not well documented. This study aimed to assess B by using a thermal threshold (TT) model. Six cats (four spayed females, two castrated males, 4.4–6.9 kg) participated in the study. The day before each study, the lateral thorax of each of the cats was shaved and a cephalic catheter was placed. TT was measured using a thermal threshold testing device specifically developed for cats. A heater element and temperature sensor housed in a small probe was held against the cat's thorax with an elastic band and pressure bladder to assure consistent contact. Skin temperature was recorded before each test, then the heater was activated. When the cat responded by flinching, turning, or jumping, the stimulus was terminated and the threshold temperature recorded. A cut-out temperature was set at 55.5 °C. Three baseline measurements were recorded before IV injections of 0.1, 0.2, 0.4, or 0.8 mg kg-1 of B. Each cat received all doses in a randomized order at least 1 week apart, and the investigator was blinded to the treatments. TT was measured at every 15 minutes for 6 hours. Data were analyzed using a three-factor anova, and the critical mean difference was calculated. Pre-treatment threshold was 40.8 ± 2.25 °C in all cats. There was a significant increase in threshold in all groups from 15 to 90 minutes, but no dose-related differences were observed. Peak threshold achieved was 48.35 °C, 60 minutes after 0.4 mg kg-1 of B was injected. Mydriasis was present in all cats after treatment, and many exhibited dysphoric behavior. In this model, B had a short duration of action and no dose–response relationship. Compared to other opioids tested under similar conditions, the intensity of the effect of B was small and of shorter duration. [ABSTRACT FROM AUTHOR]

Little is known about the analgesic action of buprenorphine (BUP) in cats. Relative to man, the cat has a more alkaline oral pH, which may make this an effective route for administering BUP in this species. This study aimed to assess and compare the pharmacokinetics and pharmacodynamics of sublingual (S-L) and IV administration of BUP. Thermal threshold (TT) was measured and blood samples were collected following IV or S-L administration (20 µg kg-1 ) of the injectable formulation. Six cats (five spayed females, one castrated male, 4.1–6.6 kg) were used. Each cat received both treatments in a randomized cross-over study design with 1 month between experiments. Twenty-four hours prior to each study, the lateral thorax of each of the cats was shaved, cephalic and jugular catheters placed, and oral pH measured. On the day of the study, TT was measured using a ‘thorax-mounted’ thermal threshold-testing device specifically developed for cats. The cats were free to move around. Skin temperature was recorded before each test, then the heater activated. When the cat responded by flinching, turning, or jumping, the stimulus was terminated and the threshold temperature was recorded. The thermal threshold cut-off point was 55.5 °C. Three baseline thresholds were recorded before treatment with S-L or IV (via cephalic catheter) BUP (20 µg kg-1 ). Blood was withdrawn (jugular) at 1, 2, 4, 6, 10, 15, 30, 45, 60 minutes and at 2, 4, 6, 8, 12, and 24 hours post-administration. TT was measured every 30 minutes-6 hours, 1–12 hours, and at 24 hours post-administration. Plasma was immediately separated, stored at -20.5 °C, and assayed within 4 months using a commercially available 125 I radioimmunoassay. Threshold data were analyzed using anova with a repeat factor of time. No adverse effects were noted. Pupils were dilated for up to 9 hours post-BUP. Behavioral changes were calm euphoria. Measured oral pH was 9 in each cat. Pre-treatment mean threshold (±SD) was 41.2 ± 0.9 °C in the S-L group and 40.8 ± 0.85 °C in the IV group. There were no significant differences between the groups with respect to thresholds over time (p = 0.72). Thresholds were significantly increased from 30 to 360 minutes in both the groups (>44.615 °C). Peak plasma BUP (Cmax ) was lower (11 ± 6.7 ng mL-1 vs. 92.9 ± 107.9 ng mL-1 ) and occurred later (Tmax ) (30 minutes vs. 1 minute) after S-L compared to IV administration, respectively. BUP (20 µg kg-1 )-administered S-L or IV provided antinociception between 30 and 360 minutes after administration. Plasma levels did not correspond to TT. [ABSTRACT FROM AUTHOR]

Hydromorphone (H) may be an effective analgesic agent in cats, but fear of negative behavioral side-effects associated with opioids is cited as a reason for avoiding this class of analgesics in cats. This study was designed to assess onset and duration of antinociception using an established feline thermal threshold model in cats, given an accepted clinical dose of 0.1 mg kg-1 of H. In addition, cats were observed for changes in behavior and other side-effects. Six adult cats from an established colony (four spayed females and two castrated males, 4.7–7.0 kg) received 0.1 mg kg-1 H IV following establishment of baseline thermal threshold (TT) values. TT was tested at 15 minutes post-injection, then at every 30–60 minutes for 12 hours. Side-effects and behavior changes were recorded for 12 hours. Changes in TT over time were analyzed using a one-way anova; a p -value <0.05 was considered significant. TT increased from a pre-treatment value of (mean ± SD) 40.9 ± 1.65 °C to instrument cutout (55.5 °C) within 30 minutes for 5/6 cats. Mean TT was significantly elevated above baseline from 15 to 450 minutes after treatment. There was a significant increase in skin temperature from 15 to 300 minutes with peak increase of 1.55 °C at 135 minutes. Side-effects included mydriasis (6/6) and nausea (4/6), characterized by licking, foaming, and gagging. Mydriasis occurred within 10–30 seconds of injection and persisted for 5–7 hours. Nausea was noted within 2 minutes of injection and persisted for 30–90 minutes; no vomiting occurred. Commonly observed behavioral changes included ventral tail curl (6/6 cats, onset 5–45 minutes, duration 4–5 hours) and euphoria (5/6 cats, onset <6 minutes for 4/6, duration 1–6 hours). 2/6 cats were profoundly sedate. Three cats showed signs of dysphoria with or without increased motor activity with variable onset and duration. Dysphoric behavior included staring, pacing, vocalizing, and sudden movements. 3/6 cats exhibited both euphoria and dysphoria at different times during the study. At no time were cats difficult to restrain or work with. Return to baseline behavior occurred 7–8.5 hours post-injection. Mydriasis did not correlate closely with antinociception. Signs of sedation and euphoria corresponded with onset of antinociception, but not duration. Tail curl signs correlated with antinociception. In this model, H proved to be a rapid acting, potent, analgesic with a long (7.5 hours) duration of action. The most common behavioral changes noted were ventral tail curl, euphoria, and sedation. Mydriasis and nausea were noted as side-effects. [ABSTRACT FROM AUTHOR]

Urethane is widely used as a rodent anesthetic in the laboratory setting, and is characterized as producing long-lasting anesthesia. The purpose of this study was to evaluate the quality of anesthesia provided by a single dose of urethane based on the response to a noxious stimulus. If the quality of anesthesia was insufficient to prevent gross purposeful movement (GPM), isoflurane was also administered until no response to noxious stimulation occurred. Five adult Harlan Sprague Dawley rats (6 months of age, 250–300 g) were given urethane (1.4 g kg-1 IP) and evaluated for 120 minutes post-injection. If the rats became laterally recumbent by 20 minutes post-injection, a large hemostat was positioned around the tail and the response to tail clamping was assessed. If no GPM occurred, an additional 20 minutes was allowed to elapse. If the rats were not laterally recumbent or GPM was present, they were placed in a chamber and isoflurane in oxygen was administered. Inspired isoflurane concentrations (ISO) were measured using a S/5 anesthetic gas analyzer (Datex-Ohmeda Division, Helsinki, Finland) calibrated before each experiment with a standardized calibration gas mixture (DOT-34 NRC 300/375 m1014, Datex-Ohmeda Division, Helsinki, Finland). A period of 20 minutes was allowed for equilibration to inspired ISO. The tail-clamp stimulus was then re-applied and the animal's response recorded. If GPM was absent, ISO was lowered by 10–20% and an additional 20 minute interval elapsed. In contrast, if GPM was present, ISO was increased by 10–20%. This procedure was repeated until the ISO required to prevent GPM was determined in duplicate. The position within the estrus cycle influenced pain thresholds in the rats. As such, a vaginal smear was prepared from each rat and the position in the estrus cycle was determined based on vaginal cytology. Rats were euthanatized at the end of the study period. All values were mean ± SD. Four rats became recumbent after urethane injection (time to recumbency: 45 ± 17 seconds). Of these, two rats (one estrus, one metestrus) did not require isoflurane supplementation for the duration of the study. The three remaining rats (two metestrus, one estrus) required isoflurane supplementation. The mean ISO required to prevent GPM was 0.26 ± 0.16%. Position within the estrus cycle did not appear to affect the animal's response to urethane. These results indicate that urethane anesthesia is not long lasting in all rats and provides variable quality of anesthesia. This is of particular concern in the laboratory setting where muscle relaxants are often administered to rats shortly after urethane injection. [ABSTRACT FROM AUTHOR]

Determines the time to onset and duration of the antinociceptive activity and plasma concentration of fentanyl following intravenous administration in cats using a thermal threshold testing system. Research methodology; Rapid onset of antinociceptive action of fentanyl after IV administration; Pharmacokinetic data indicating little hysteresis between plasma concentration and effect.

Evaluates the effects of albuterol sulfate delivered by a simple metered-dose inhaler system on PaO[sub 2] values in hypoxaemic horses. Research methodology; Advantages of albuterol delivered via the endotracheal tube in anesthetized horses; Study's failure to elucidate the mechanism of action of albuterol.

Evaluates the effects of lidocaine (L) and ketamine (K) on thermal thresholds in cats. Research methodology; Apparent ability of K to cause hyperalgesia to thermal stimulation in cats; Failure of L to provide analgesia under the laboratory condition conditions studied.

Examines the effectivity of buprenorphine, an analgesic for cats in Great Britain. Effects of the administration of buprenorphine on the salivation of cats; Investigation of buprenorphine pharmacokinetics after buccal administration of buprenorphine hydrochloride solution; Similarity of intravenous and intramuscular administration to the buccal route.

There is a lack of specific information on the pharmacokinetics of opioids in cats. As a result, dosing intervals for cats are extrapolated from other species despite evidence that they may handle drugs uniquely. The aim of this study was to perform kinetic analysis from measured plasma concentrations of buprenorphine [B], morphine [M], and meperidine [ME]. Healthy adult cats (five females, 1 male, 2–11 years, 2.9–7.2 kg) received B (10 µg kg-1 IV, IM), M (0.2 mg kg-1 IV, IM) and ME (5 mg kg-1 IM only) in a randomized order, with a minimum of 7 days between treatments. IM injections were made in the epaxial muscles. Blood was withdrawn from preplaced jugular catheters before and at 1, 2, 4, 6, 10, 15, 30, 45 and 60 minutes, and at 2, 4, 6, 8, 12 and 24 hours after drug dosing. Plasma was separated by centrifugation and stored at -20 °C until assayed. Plasma B was measured using an iodine labelled RIA; M was assayed by HPLC, and ME by gas chromatography. Concentration-time data were analyzed using a noncompartmental method. Compared to IV administration, bioavailability (F) after IM was 100% for B, and 26–124% for M. Cmax (ng mL-1, median and range) was B: 8.7 (3.6–11.8), M: 120 (45–218) and ME: 110 (86–142). Tmax (minutes, median and range) was B: 3 (2–15), M: 15 (1–45), ME: 10 (5–120). B, M, and ME T1/2β (mean ± SD) were 380 ± 131, 94 ± 8, and 216 ± 123 minutes, respectively. Plasma clearance rate (mL kg-1 minute-1) was 23.6 ± 12.6 for B, 13.9 ± 4 for M, and 20.8 ± 10.6 for ME. VSS (L kg-1) was 8.9 ± 5.9 for B, 1.7 ± 0.8 for M, and 5.2 ± 2.1 for ME. Several of the derived pharmacokinetic variables in this study are different from those published for dogs. This study suggests that dosing schedules for opioids in cats should be based on species-specific data. [ABSTRACT FROM AUTHOR]

In order to compare analgesic drugs, pain must be produced in a controlled fashion and the response must be measurable. Thermal nociceptive threshold devices have been used in several species, but there is little information on their use to assess opioid induced analgesia in cats. The aim of this study was to measure thermal thresholds in cats following administration of buprenorphine (B), morphine (M) and saline (S). Six healthy adult cats (five females, one male, 2–11 years, 2.9–7.2 kg) received three treatments in a randomized crossover design. The investigator was blinded to the treatments, which were as follows: B (10 µg kg-1 IM), M (0.2 mg kg-1 IM) and S (0.3 mL IM). All injections were made in the epaxial muscles. An electrical element produced thermal stimulation at a rate of 0.8 °C second-1, which was measured by an adjacent temperature sensor. Both were embedded in conductive epoxy and attached to the shaved thorax by an elastic and Velcro band that the cats were accustomed to wearing. The sensor output was read on a digital voltmeter. The end-point was a distinct skin twitch at which time the hold button on the voltmeter was pressed. A safety cutoff was set at 70 °C. Reproducibility of results in untreated cats has been previously reported. Measurements were made before, and at 5, 30, 45, 60 minutes and 2, 4, 6, 12 and 24 hours after IM injection. Data were analyzed by two-way analysis of variance for repeated measures. There was no significant change in thermal threshold after S. Following B; the thermal threshold was significantly (p < 0.05) increased at 2 and 6 hours (5.6 and 5.8%), respectively. Four hours after M administration, the thermal threshold was increased by 11.4% (p < 0.05). This study shows that significant increases in thermal thresholds are slow to develop after IM injection of B or M in cats. [ABSTRACT FROM AUTHOR]

Same-day mass sterilization of feral cats requires rapid onset, short-duration anesthesia. The purpose of this study was to compare our current anesthetic protocol, Telazol–ketamine–xylazine (TKX) with medetomidine–ketamine–buprenorphine (MKB). Feral female cats received either IM TKX (n = 68; 0.25 mL cat-1 ; tiletamine 12.5 mg, zolazepam 12.5 mg, K 20 mg, and X 5 mg per 0.25 mL) or MKB (n = 17; M 40 µg kg-1 , K 15 mg kg-1 , and B 10 µg kg-1 ). Intervals measured included time from injection to recumbency, time to surgery, duration of surgery, and time from reversal of anesthesia (TKX: yohimbine 0.50 mg cat-1 IV; MKB: atipamezole 0.50 mg cat-1 IM) to sternal recumbency. Following instrumentation (Vet/Ox 4403 and Vet/BP Plus 6500), physiological measurements were recorded at 5-minute intervals, and included rectal temperature, heart rate (HR), respiratory rate (RR), SpO2 (lingual or rectal probes), and indirect mean arterial blood pressure (MAP) (oscillometric method). Nonparametric means were compared using Mann–Whitney U -tests. Parametric means were compared using a two-factorial anova with Bonferroni's t -tests. The alpha-priori significance level was p < 0.05. Values were mean ± SD. Body weight (TKX: 2.9 ± 0.5 kg, MKB: 2.7 ± 0.7 kg), time to recumbency (TKX: 4 ± 1 minutes, MKB: 3 ± 1 minutes), time to surgery (TKX: 28 ± 7 minutes, MKB: 28 ± 5 minutes), and duration of surgery (TKX: 11 ± 7 minutes, MKB: 8 ± 5 minutes) did not differ between groups. In contrast, MKB cats required less time from reversal to sternal recumbency (TKX: 68 ± 41 minutes, MKB: 7 ± 2 minutes) and were recumbent for shorter duration (TKX: 114 ± 39 minutes, MKB: 53 ± 6 minutes). Temperature decreased during the study in both groups, but overall temperature was higher in MKB cats (38.0 ± 0.95 °C) than in TKX cats (37.5 ± 0.95 °C). RR, HR, and SpO2 did not change during the study in either group. However, overall HR and RR were higher in TKX cats (RR: 18 ± 8 breaths minute-1 , HR: 153 ± 30 beats minute-1 ) compared to MKB cats (RR: 15 ± 7 breaths minute-1 , HR: 128 ± 19 beats minute-1 ). In contrast, overall SpO2 was lower in the TKX group (90 ± 6%) compared to the MKB group (94 ± 4%). MAP was also lower in the TKX group (112 ± 29 mm Hg) compared to that in the MKB group (122 ± 20 mm Hg). However, MAP increased in the TKX group during surgery compared to pre-surgical values, but did not change in the MKB group. The results of this study suggested that MKB might be more suitable as an anesthetic for the purpose of mass sterilization of feral female cats. [ABSTRACT FROM AUTHOR]

Simulators developed at Stanford University and at the University of Florida permit students and physicians to administer anesthesia in real time. The patient has breath sounds, a heartbeat, pulses, neuromuscular transmission and produces urine. The patient can be monitored with an electrocardiogram; arterial, venous and pulmonary pressures; pulse oximetry; temperature; respiratory gases and cardiac output. The instructor can instantly program the patient, anesthesia machine and monitors to react to complications such as, but not limited to, equipment failure, laryngospasm, endobronchial intubation, pulmonary edema, atelectasis, tension pneumothorax, bronchospasm, hemorrhage, shock, heart failure, malignant hyperthermia, excessive anesthetic depth, anaphylaxis, ventricular tachycardia and cardiac arrest. The student analyzes data displayed on real time monitors and examines the patient, after which he/she initiates therapy and the patient responds. Students of veterinary medicine at our institution receive a very limited time learning anesthesia (a lecture series, a two-week core clinical rotation and, for approximately one-half of the students, another two-week elective). Yet, when these students graduate, a substantial number of them will anesthetize their own patients in the clinic. It is doubtful in a two to four week rotation, that they will encounter critical events that lead to significant complications or even mortality. Therefore, we have tailored an experience with the simulator for our veterinary medicine students. Our students work in small groups of 4–6 students at a time taking care of ‘Joe the Chimp’, but for the appearance of the mannequin, could be ‘Fido the Dog’. The experience is challenging and virtually ‘real life’ so that the students talk about ‘their patient’ without sacrificing live animals. They display concern, sweat when things go wrong, jump in to help each other, and breathe a sigh of relief when their treatment is appropriate. Between 1 November 1999 and 15 June 2000, 48 students have taken the course. Each student evaluates the course in a narrative written response. They are enthusiastic, report this is an excellent way to apply book knowledge to ‘real life’ without sacrificing animals and want more such classes. We conclude that this is a valuable teaching tool and has considerable promise for the future. [ABSTRACT FROM AUTHOR]