Evaluation of the sedative and cardiorespiratory effects of dexmedetomidine, dexmedetomidine-butorphanol, and dexmedetomidine-ketamine in cats

Clinical Effects and Pharmacokinetic Profile of Intramuscular Dexmedetomidine (10 μg/kg) in Cats

This study investigated the pharmacokinetic profile of and pharmacodynamic response to dexmedetomidine administered intramuscularly (IM) at a dose of 10 μg/kg in healthy cats. Nine adult cats were evaluated before and after administration of the drug, with serial collections of plasma samples. Dexmedetomidine induced deep sedation, with a rapid onset of action and a duration of one hour, reaching a peak between 20 and 30 min after administration. The half-life (T½) was 70.2 ± 48 min, with a maximum concentration (Cmax) of 2.2 ± 1.9 ng/mL and time to reach maximum concentration (Tmax) of 26.4 ± 19.8 min. The area under the curve (AUC) was 167.1 ± 149.1 ng/mL*min, with a volume of distribution (Vd) of 2159.9 ± 3237.8 mL/kg and clearance (Cl) of 25.8 ± 33.0 mL/min/kg. There was a reduction in heart rate (HR) and respiratory rate (RR) in relation to the baseline, with a slight decrease in systolic (SBP), diastolic (DBP), and mean (MAP) blood pressure in the first hour. Blood glucose increased after 60 min. Dexmedetomidine proved to be effective and safe, with rapid absorption, metabolization, and elimination, promoting good sedation with minimal adverse effects after IM administration in healthy cats.

Use of orally administered dexmedetomidine to induce emesis in cats

CASE SERIES SUMMARY

This case series describes the use of orally administered dexmedetomidine at a dose of 20 µg/kg to induce emesis in six cats. Emesis was successfully induced in 5/6 cats, with each of the cats vomiting once. The reasons for inducing vomiting included known or suspected ingestion of lilies, onions, acetaminophen (paracetamol) or acetylsalicylic acid. Four of the five cats in which emesis induction was successful did not develop any clinical signs of toxicity associated with the toxin ingested; the fifth cat developed clinicopathological changes consistent with acetaminophen toxicity. All six cats exhibited moderate to profound sedation, as expected, but no other adverse effects were documented.

RELEVANCE AND NOVEL INFORMATION

Induction of emesis in cats is notoriously difficult. This case series describes a novel route of administration of dexmedetomidine, a commonly available medication, with a high success rate observed for inducing emesis in this group of cats.

The Effect of a Subsequent Dose of Dexmedetomidine or Other Sedatives following an Initial Dose of Dexmedetomidine on Sedation and Quality of Recovery in Cats: Part I

Dexmedetomidine is an a2-agonist commonly used in veterinary practice. Occasionally, the administered dose of dexmedetomidine may result in insufficient sedation, and an additional dose or drug may be required. The sedative effects of seven different drugs administered at subsequent time points after an initial, insufficient dose of dexmedetomidine were evaluated. Seven adult cats participated in this crossover, blind, randomised study. The groups consisted of two consecutive doses of dexmedetomidine (15 + 10 μg/kg) (DD) or a dose of dexmedetomidine (15 μg/kg) followed by either NS 0.9% (DC-control group), tramadol 2 mg/kg (DT), butorphanol 0.2 mg/kg (DBT), buprenorphine 20 μg/kg (DBP), ketamine 2 mg/kg (DK), or midazolam 0.1 mg/kg (DM). Sedation was evaluated using the Grint sedation scale. In all groups, atipamezole was administered at the end of the evaluation, and recovery was assessed using the Lozano and Sams recovery scales. The DC and DM groups exhibited minimal sedative effects. The maximum sedative effect was observed in the DD and DK groups, while sedation in the DD and DK groups was significantly higher compared to the DC group. Recovery in all groups was uneventful, except in the DM group, where it was prolonged and difficult, although no statistically significant difference was detected. Therefore, insufficient sedation with dexmedetomidine can be enhanced by a subsequent dose of dexmedetomidine, ketamine, or butorphanol, whereas the addition of midazolam reduces sedation and prolongs recovery.

The Effect of a Subsequent Dose of Dexmedetomidine or Other Sedatives following an Initial Dose of Dexmedetomidine on Electrolytes, Acid-Base Balance, Creatinine, Glucose, and Cardiac Troponin I in Cats: Part II

The administered dose of dexmedetomidine may occasionally fail to produce the anticipated sedative effects. Therefore, a subsequent dose or administration of another sedative may enhance sedation; however, patient safety may be affected. The safety of seven different drugs administered at the following time point after an insufficient dose of dexmedetomidine was evaluated in a crossover, blind, experimental study that included six healthy adult cats. All cats received an initial dose of dexmedetomidine and a subsequent dose of either dexmedetomidine (Group DD), NS 0.9% (DC), tramadol (DT), butorphanol (DBT), buprenorphine (DBP), ketamine (DK), or midazolam (DM). Animal safety was assessed using repeated blood gas analysis and measurement of electrolytes, glucose, cardiac troponin I, and creatinine to evaluate cardiac, respiratory, and renal function. The median values of creatinine, cardiac troponin I, pH, partial pressure of carbon dioxide, potassium, and sodium did not change significantly throughout the study. Heart rate was significantly decreased in all groups after administration of the drug combinations, except for in the DK group. Respiratory rate decreased significantly after administration of the initial dose of dexmedetomidine and in the DBP and DM groups. The partial pressure of oxygen, although normal, decreased significantly after the administration of dexmedetomidine, whereas the median concentration of glucose increased significantly following the administration of dexmedetomidine. The results of our study suggest that the drug combinations used did not alter the blood parameters above normal limits, while cardiac and renal function were not compromised. Therefore, a safe level of sedation was achieved. However, the administration of dexmedetomidine reduced the partial pressure of oxygen; thus, oxygen supplementation during sedation may be advantageous. Additionally, the increase in glucose concentration indicates that dexmedetomidine should not be used in cats with hyperglycaemia, whereas the decrease in haematocrit suggests that dexmedetomidine is not recommended in anaemic cats.

Multiple uses of dexmedetomidine in small animals: a mini review

Dexmedetomidine is an alpha-2 adrenergic agonist, which use had an exponential increase in human and veterinary medicine in the last 10 years. The aim of this mini review is to summarize the various uses of dexmedetomidine underlining its new applications and capabilities in the small animals' clinical activity. While this drug was born as sedative in veterinary medicine, some studies demonstrated to be effective as an analgesic both in single administration and in continuous infusion. Recent studies have also shown the role of dexmedetomidine as an adjuvant during locoregional anesthesia, increasing the duration of the sensitive block and consequently decreasing the demand for systemic analgesics. The various analgesic properties make dexmedetomidine an interesting drug for opioid-free analgesia. Some studies highlighted a potential neuroprotective, cardioprotective and vasculoprotective role of dexmedetomidine, thus conferring it a place in critical care medicine, such as trauma and septic patients. Dexmedetomidine has demonstrated to be a multitasking molecule and it is ready to face new challenges.

Ophthalmic effects of dexmedetomidine, methadone and dexmedetomidine-methadone in healthy cats and their reversal with atipamezole

OBJECTIVES

The aims of this study were to evaluate and compare the effects that dexmedetomidine and methadone, either alone or in combination, have on the ocular variables of healthy adult cats when administered intramuscularly, as well as their reversal with atipamezole.

METHODS

A randomized crossover blinded study of 10 healthy cats was used to assess the effect of 0.2 mg/kg methadone (MET), 7.5 μg/kg dexmedetomidine (D7), 10 μg/kg dexmedetomidine (D10), 7.5 μg/kg dexmedetomidine and 0.2 mg/kg methadone (DM7) and 10 μg/kg dexmedetomidine and 0.2 mg/kg methadone (DM10) on intraocular pressure (IOP), tear production and pupil diameter (PD). The animals were evaluated for 30 mins. Afterwards, atipamezole was administered and ocular variables were evaluated for 30 mins.

RESULTS

D10, DM7 and DM10 significantly decreased mean IOP but MET or D7 did not. Tear production decreased significantly in all treatments, corresponding to 18%, 59%, 63%, 86% and 98% in MET, D7, D10, DM7 and DM10, respectively. PD increased in all treatments, but MET showed the highest PD. Thirty minutes after atipamezole (RT30), IOP returned to baseline with no difference between groups, and there was a significant increase in tear production, but the means were still different from baseline.

CONCLUSIONS AND RELEVANCE

Dexmedetomidine decreases IOP and tear production but increases PD in healthy cats. Atipamezole can partly reverse those alterations. Low-dose dexmedetomidine (7.5 µg/kg) promotes sedation without changing the IOP. All protocols significantly decrease tear production, and Schirmer tear test after sedation is not representative of non-sedated values. Methadone induces quick onset mydriasis without changing the IOP.

Ketamine-dexmedetomidine combined with local anesthesia, with or without different doses of atipamezole in the postoperative period, for orchiectomy in cats

OBJECTIVE

To evaluate the anesthetic and cardiopulmonary effects of ketamine-dexmedetomidine combined with local anesthesia, associated or not in the postoperative period with different doses of atipamezole, for orchiectomy in cats.

ANIMALS

24 healthy cats.

PROCEDURES

Cats received ketamine (7 mg/kg) combined with dexmedetomidine (10 µg/kg) IM, and 1 mL of saline (group KDSAL), 25 µg/kg (group KDAT25), or 50 µg/kg (group KDAT50) of atipamezole IV, postoperatively. All cats received local anesthesia (2 mg/kg of lidocaine) intratesticular and SC. Physiologic variables were recorded at baseline and at time points during anesthesia. Ketamine rescue dose (1 mg/kg) was recorded. The quality of recovery, the degree of sedation, and side effects were evaluated postoperatively.

RESULTS

2 cats received a single additional bolus of ketamine to perform local anesthesia. Heart rate was lower in KDSAL, KDAT25, and KDAT50 during anesthesia, compared with baseline. Hypertension was observed intraoperatively in all groups. The time to head up, pedal reflex regained time, time to sternal recumbency, and time to standing were shorter in KDAT25 and KDAT50 compared to KDSAL. Lower sedation scores were assigned sooner to KDAT25 and KDAT50 than KDSAL. All groups resulted in low recovery quality scores and no side effects.

CLINICAL RELEVANCE

At the doses used, ketamine-dexmedetomidine combined with local anesthesia allowed the performance of orchiectomy. Rescue dose of ketamine for performing local anesthesia may be required. This combination can result in hypertension. Both atipamezole doses shortened the anesthetic recovery, without differences among them, and side effects.

Effect of Dexmedetomidine Low Doses with or without Midazolam in Cats: Clinical, Hemodynamic, Blood Gas Analysis, and Echocardiographic Effects

Objectives

The aim of the study is to compare the sedative, cardiorespiratory, echocardiographic, and blood gas effects of dexmedetomidine and methadone associated or not with midazolam for restraint chemistry in cats.

Methods

Eighteen healthy young cats (4.06 ± 0.48 kg) were randomly sedated with two protocols, through the intramuscular route: dexmedetomidine (5 µg.kg-1), methadone (0.3 mg. kg-1) and midazolam (0.3 mg. kg-1) (DMTM, n = 9), or dexmedetomidine (7.5 µg.kg-1) and methadone (0.3 mg. kg-1) (DMT, n = 9). The cardiorespiratory parameters were measured at baseline, 5 and 10 minutes after pharmacological latency. The sedation, analgesia, and muscle relaxation scores were assessed before and 5 minutes after pharmacological latency, while arterial blood gas analysis and echocardiography were assessed before and after 10 or 15 minutes, respectively.

Results

There was no difference between the protocols regarding the cardiorespiratory, blood gas, and echocardiographic parameters used. The scores for sedation, analgesia, and muscle relaxation also did not differ between the protocols, with the degree of sedation, analgesia, and myorelaxation considered satisfactory in both groups. A significant decrease in heart rate (HR) was observed after administration of the sedative protocols, reaching a maximum reduction at T10 (46% and 53% reduction in the DMT and DMTM groups, respectively). The reduction in HR had an impact on echocardiographic parameters such as CO, which decreased 53% and 56% in the DMT and DMTM groups, respectively. There was a significant reduction in PaO2, SaO2, ejection fraction, and fractional shortening in both protocols. SpO2 decreased significantly after 5 minutes of sedation in the DMT group, but with a minimum mean SpO2 of 92% in T5. The respiratory rate decreased significantly at 5 and 10 minutes in the DMTM group, while PaCO2 increased in both groups, indicating respiratory depression caused by the drugs. Conclusions and Relevance. The study pointed out that both sedative protocols can be recommended for clinical sedation of young and healthy cats in the doses used. However, both protocols resulted in cardiorespiratory depression in cats and also the particularities of the animals should be evaluated regarding reducing cardiac output by more than 50%.

Comparison of two injectable anaesthetic protocols in Egyptian fruit bats (Rousettus aegyptiacus) undergoing gonadectomy

Egyptian fruit bats have gained increasing interest being a natural reservoir for emerging zoonotic viruses. Anaesthesia is often required to allow safe handling of bats. We aimed to compare the sedative and cardiopulmonary effects of two balanced anaesthetic protocols in bats undergoing gonadectomy. Group DK (n = 10) received intramuscular dexmedetomidine (40 µg/kg) and ketamine (7 mg/kg), whereas group DBM (n = 10) received intramuscular dexmedetomidine (40 µg/kg), butorphanol (0.3 mg/kg) and midazolam (0.3 mg/kg). Induction time and cardiopulmonary parameters were recorded. If anaesthetic plan was inadequate, isoflurane was titrated-to-effect. At the end of surgery venous blood gas analysis was performed and atipamezole or atipamezole-flumazenil was administered for timed and scored recovery. In DBM group heart rate and peripheral oxygen saturation were significantly higher (p = 0.001; p = 0.003 respectively), while respiratory rate was significantly lower (p = 0.001). All bats required isoflurane supplementation with no significant differences between groups. Induction and recovery times showed no significant differences. In group DK a better recovery was scored (p = 0.034). Sodium and chloride were significantly higher in DBM group (p = 0.001; p = 0.002 respectively). Both anaesthetic protocols were comparable and can be recommended for minor procedures in bats.

Effects of dissociative anesthesia opioid-free protocols combined with local anesthesia, with or without flumazenil or atipamezole postoperatively, for orchiectomy in cats

OBJECTIVE

To evaluate the anesthetic effects of two drug combinations with local anesthesia, with or without postoperative antagonists, for orchiectomy in cats.

STUDY DESIGN

Prospective, randomized blinded clinical study.

ANIMALS

A total of 64 healthy cats.

METHODS

Cats were assigned to four equal groups: ketamine (5 mg kg^-1) and dexmedetomidine (10 μg kg^-1) were administered intramuscularly (IM), followed postoperatively with intravenous (IV) saline (5 mL; group KDS) or atipamezole (50 μg kg^-1; group KDA); and ketamine (14 mg kg^-1) with midazolam (0.5 mg kg^-1) and acepromazine (0.1 mg kg^-1) IM, with postoperative IV saline (5 mL; group KMAS) or flumazenil (0.1 mg kg^-1; group KMAF). Lidocaine (2 mg kg^-1) was divided between subcutaneous and intratesticular injection. Physiologic variables were recorded at time points during anesthesia. Ketamine rescue dose was recorded. The degree of sedation and the quality of recovery were evaluated postoperatively.

RESULTS

Time to loss of pedal reflex was longer in groups KMAS and KMAF than in groups KDS and KDA (p = 0.010). Total rescue dose of ketamine was higher in KMAS and KMAF than in KDS and KDA (p = 0.003). Heart rate (HR) during anesthesia was higher in KMAS and KMAF than in KDS and KDA (p = 0.001). Times to head up (p = 0.0005) and to sternal recumbency (p = 0.0003) were shorter in KDA than in KDS, KMAS and KMAF. Lower sedation scores were assigned sooner to KDA than KDS, KMAS and KMAF (p < 0.001). Recovery quality scores were good in all groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Both anesthetic protocols allowed the performance of orchiectomy. Groups KMAS and KMAF required higher rescue doses of ketamine before injecting lidocaine. HR and oscillometric systolic pressure were minimally changed in groups KD and tachycardia was recorded in groups KMA. Only atipamezole shortened the anesthetic recovery.

The effects of two intramuscular sedation protocols on echocardiographic variables in cats following sedation and blood donation

OBJECTIVE

To compare effects of 2 IM sedation protocols, alfaxalone-butorphanol (AB) versus dexmedetomidine-butorphanol (DB), on echocardiographic (ECHO) variables in cats following sedation and blood donation.

DESIGN

Experimental randomized, blinded crossover study.

SETTING

University teaching hospital.

ANIMALS

Eleven client-owned healthy cats.

INTERVENTIONS

Cats received a baseline ECHO without sedation prior to their first donation. Cats were sedated intramuscularly with AB (alfaxalone, 2 mg/kg, and butorphanol, 0.2 mg/kg) for 1 donation and DB (dexmedetomidine, 10 μg/kg, and butorphanol 0.2, mg/kg) for another, with a minimum 6 weeks between donations. A post-sedation, post-donation ECHO was performed after each blood donation.

MEASUREMENTS AND MAIN RESULTS

Eight cats completed the study. Compared to baseline, DB combined with blood donation decreased heart rate (-84/min; P < 0.0001), fractional shortening (-16.5%; P < 0.0001), ejection fraction (-21.0%; P = 0.0002), and cardiac output (-292 mL/min, P = 0.0001); AB combined with blood donation increased heart rate (+45/min; P = 0.0003) and decreased left ventricular end diastolic volume (-1.57 mL; P < 0.0001). Compared to AB, DB decreased heart rate (-129/min; P < 0.0001) and fractional shortening (-21.6%; P < 0.0001) and increased left ventricular end-systolic (+1.14 mL; P = 0.0004) and diastolic volumes (+1.93 mL; P < 0.0002). Cats administered DB had a significant increase in regurgitant flow across mitral, aortic, and pulmonic valves following blood donation (P < 0.05). One cat administered DB developed spontaneous echo contrast in the left ventricle following donation.

CONCLUSIONS AND CLINICAL RELEVANCE

Compared to AB, DB had more pronounced effects on ECHO variables in cats following IM sedation and blood donation. Due to its minimal impact on ECHO variables, AB may be a more desirable sedation protocol in this population of cats.

Feline procedural sedation and analgesia: When, why and how

PRACTICAL RELEVANCE

Procedural sedation and analgesia (PSA) describes the process of depressing a patient's conscious state to perform unpleasant, minimally invasive procedures, and is part of the daily routine in feline medicine. Maintaining cardiopulmonary stability is critical while peforming PSA.

CLINICAL CHALLENGES

Decision-making with respect to drug choice and dosage regimen, taking into consideration the cat's health status, behavior, any concomitant diseases and the need for analgesia, represents an everyday challenge in feline practice. While PSA is commonly perceived to be an uneventful procedure, complications may arise, especially when cats that were meant to be sedated are actually anesthetized.

AIMS

This clinical article reviews key aspects of PSA in cats while exploring the literature and discussing complications and risk factors. Recommendations are given for patient assessment and preparation, clinical monitoring and fasting protocols, and there is discussion of how PSA protocols may change blood results and diagnostic tests. An overview of, and rationale for, building a PSA protocol, and the advantages and disadvantages of different classes of sedatives and anesthetics, is presented in a clinical context. Finally, injectable drug protocols are reported, supported by an evidence-based approach and clinical experience.

Plasma Concentration Rise after the Intramuscular Administration of High Dose Medetomidine (0.13 mg/kg) for Semen Collection in Cats

High dose medetomidine 0.13 mg/kg can be used for semen collection in cats with variable results in terms of quantity and quality. Therefore, a variation in terms of distribution and elimination among patients has been hypothesised. The aim of the study was to characterise the pharmacokinetics of medetomidine (0.13 mg/kg) administered intramuscularly (IM) in healthy male cats. Eighteen male cats undergoing castration were included, and medetomidine (0.13 mg/kg) was administered IM. Venous blood samples were collected at 20, 30, 40, 50, 60, 75 and 90 minutes after medetomidine administration. Before orchiectomy, at T20, sperm collection was attempted. Plasma medetomidine concentrations were determined by liquid chromatography/mass spectrometry analysis. Semen collection was successful in 15/18 cats. The medetomidine plasma concentration following the IM administration of a bolus was best described using a non-compartment model. Time of maximum concentration was observed at 40 minutes (range 20–90); maximum concentration was 32.8 ng/mL (range 26.8–51.2). The median apparent clearance was 11.9 mL/kg/minute (range 0.7–43.8). In conclusion, medetomidine administered IM at 0.13 mg/kg reached its peak plasma concentration slowly and with variability among patients. In addition, it was characterised by low total body clearance probably due to the cardiovascular alterations associated with medetomidine administration.

Use of nalbuphine as a substitute for butorphanol in combination with dexmedetomidine and tiletamine/zolazepam: a randomized non-inferiority trial

OBJECTIVES

The goal of this study was to determine whether a drug combination using nalbuphine with dexmedetomidine and tiletamine/zolazepam is non-inferior to one that uses butorphanol.

METHODS

All healthy cats presenting solely for gonadectomy to two trap-neuter-return mobile clinic days were randomly assigned to induction with a combination of tiletamine/zolazepam 3 mg/kg, dexmedetomidine 7.5 µg/kg and either butorphanol or nalbuphine at 0.15 mg/kg. All participants were blinded to the identity of the combinations. The primary endpoint was clinician satisfaction, comprised of the mean of four satisfaction ratings on a 7-point Likert scale (highly dissatisfied through to highly satisfied) recorded for induction, maintenance of anesthesia, surgery and recovery. Exploratory endpoints included each individual score, number of injections, duration of induction, duration of recovery and need for reversal agent. To assess non-inferiority for the primary endpoint and individual scores, the difference and 95% confidence intervals (CIs) of the difference between the mean clinical scores for the nalbuphine and butorphanol-based combinations were calculated and compared with a prespecified non-inferiority margin of 20% (1.4 points).

RESULTS

Seventy-two cats were enrolled, 36 in each group. The mean ± SD composite score for the combination with nalbuphine was 6.06 ± 0.59 (95% CI 5.86-6.25) points, while the combination with butorphanol was 6.22 ± 0.62 (95% CI 6.01-6.43). The difference between mean scores was 0.17 (-0.12 to 0.45), which did not exceed the prespecified boundary of 1.4, establishing the non-inferiority of nalbuphine. No individual clinical score for nalbuphine was inferior to butorphanol, and there were no significant differences for any secondary endpoints.

CONCLUSIONS AND RELEVANCE

The clinical experience of the nalbuphine-based combination was non-inferior to the butorphanol-based combination. Nalbuphine is an effective substitute for butorphanol, providing another option if butorphanol is unavailable due to shortage, controlled status or cost, without requiring a change in anesthetic workflow.

Sedative, analgesic, behavioral and clinical effects of intravenous nalbuphine-xylazine combination in camels (Camelus dromedarius)

This study examined the sedative, analgesic, behavioral, and clinical effects of a combination of xylazine (XY) and nalbuphine-xylazine (NA-XY) in camels. A total of five adult camels were used in a prospective randomized cross-over design with a wash out period of two weeks. Camels were allocated randomly to two treatment groups: the XY group (xylazine, 1.1mL/100 kg IV) and the NA-XY group (xylazine, 1.1mL/100 kg IV and nalbuphine, 1 mg/kg IV). The sedative, analgesic, behavioral, and clinical effects of XY and NA-XY combination were evaluated prior to administration (baseline) and at 5, 15, 30, 45, 60, 75, 90, and 120 minutes post-administration. The results showed that the NA-XY combination accelerates the onset of sedation and analgesia and prolongs the durations of both sedation (p < 0.001) and analgesia (p < 0.01). The behavioral parameters showed higher scores with a NA-XY combination than xylazine alone. Although a XY injection resulted in a significant decline in the heart and respiratory rate, the NA-XY combination group revealed a non-significant change in both clinical parameters compared to the baseline. In conclusion, the use of a NA-XY combination in camels improved the sedative and analgesic onset and duration with an improved outcome in the behavioral scores, as well as in both the heart and respiratory rates compared to XY alone.

Early reversal of ketamine/dexmedetomidine chemical immobilization by atipamezole in golden-headed lion tamarins (Leontopithecus chrysomelas)

BACKGROUND

A smooth and rapid recovery from anesthesia allowing safe release is desirable, especially for wild species. This study describes the clinical effects of the combination of dexmedetomidine and ketamine and the partial reversal with atipamezole in golden-headed lion tamarins.

METHODS

Dexmedetomidine 10 μg kg^-1 and ketamine 15 mg kg^-1 were administered to 45 golden-headed lion tamarins undergoing vasectomy. Following surgery, animals were assigned to three groups: control (SAL; 0.9% NaCl), atipamezole 20 μg kg^-1 (ATI20), and atipamezole 40 μg kg^-1 (ATI40).

RESULTS AND CONCLUSIONS

All animals presented great scores of sedation and muscle relaxation during the procedure. Recovery in the control group was smooth and uneventful. Salivation, muscle tremors, and head movements were observed in ATI 20 and ATI40. The administration of atipamezole did not change total recovery times (ATI20 69 ± 23 minutes; ATI40 72 ± 45 minutes; SAL 57 ± 23 minutes).

Butorphanol-Azaperone-Medetomidine for the Immobilization of Rhesus Macaques (Macaca mulatta)

Maximizing animal wellbeing by minimizing drug-related side effects is a key consideration when choosing pharmaceutical agents for chemical restraint in nonhuman primates. One drug combination that may promote this ideology is butorphanol (27.3 mg/mL), azaperone (9.1 mg/mL), and medetomidine (10.9 mg/mL; BAM). Based on results from a pilot study, 2 doses of BAM (16 and 24 μL/kg IM) were compared in healthy, 3-y-old rhesus macaques. Physiologic parameters and anesthetic quality were assessed and recorded every 5 min. Experimental endpoints were established for hypoxemia (85% or less peripheral oxygen saturation with oxygen supplementation), pulse rate (80 bpm or less for 2 consecutive readings), mean arterial pressure (MAP; 50 mm Hg or less), and hypothermia (97 °F or less); if any endpoint was achieved, medetomidine was reversed by using atipamezole (0.22 mg/kg IM). Both BAM doses resulted in immobilization of all animals with no clinically significant differences between groups. All animals initially exhibited hypoxemia that resolved with oxygen supplementation. Regardless of dose, most macaques (71%) reached established experimental endpoints for bradycardia (62 to 80 bpm) or hypotension (44 to 50 mm Hg MAP). Given the results of this study, our recommendation regarding the use of 16- or 24-μL/kg BAM for immobilizing rhesus macaques is dependent on caution regarding cardiopulmonary parameters and the provision of supplemental oxygen.

Thermal antinociceptive, sedative and cardiovascular effects of Governing Vessel 1 dexmedetomidine pharmacopuncture in healthy cats

OBJECTIVE

To compare the antinociceptive, sedative and cardiovascular effects of dexmedetomidine pharmacopuncture at Governing Vessel 1 (GV 1) with dexmedetomidine intramuscular (IM) administration.

STUDY DESIGN

Randomized, masked crossover design.

ANIMALS

A group of eight healthy female cats.

METHODS

Cats were randomly administered either dexmedetomidine (0.005 mg kg^-1; Dex-IM) IM or at acupuncture point GV 1 (Dex-P) separated by 1 week. Prior to and up to 120 minutes posttreatment, skin temperature (ST), thermal threshold (TT), heart rate (HR), respiratory rate (f_R), sedation, muscle relaxation and auditory response scores were recorded. Parametric data were analyzed using a two-way repeated measures anova followed by Tukey's test for multiple comparisons. Nonparametric data were analyzed using a Friedman test followed by Dunn's multiple comparisons test, and Wilcoxon signed-rank test with Bonferroni correction for multiple comparisons. Significance was set at p ≤ 0.05.

RESULTS

There were no differences within or between treatments for ST, f_R and auditory response. TT was significantly higher at 30-90 minutes in Dex-P (p ≤ 0.0285) than baseline. TT was significantly higher at 60-90 minutes for Dex-P than for Dex-IM (p ≤ 0.0252). HR was significantly lower at 10-75 minutes in Dex-P (p ≤ 0.0378) and at 5-75 minutes in Dex-IM (p ≤ 0.0132) than baseline. Compared with baseline, sedation scores were higher at 25 minutes (p = 0.0327) and 30 minutes (p = 0.0327), and muscle relaxation scores were higher at 25 minutes (p = 0.0151) and 35 minutes (p = 0.0151) in Dex-P. There were no differences in HR, sedation and muscle relaxation scores between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Dex-P increased thermal antinociception compared with Dex-IM at the same dose of dexmedetomidine in cats. This antinociceptive effect must be evaluated under clinical situations.

Sedative and electrocardiographic effects of low dose dexmedetomidine in healthy cats

ABSTRACT: In feline veterinary practice sedation is often needed to perform diagnostic or minimally invasive procedures, minimize stress, and facilitate handling. The mortality rate of cats undergoing sedation is significantly higher than dogs, so it is fundamental that the sedatives provide good cardiovascular stability. Dexmedetomidine (DEX) is an α2-adrenergic receptor agonist utilized in cats to provide sedation and analgesia, although studies have been utilized high doses, and markedly hemodynamic impairments were reported. The aim of this study was to prospectively investigate how the sedative and electrocardiographic effects of a low dose of DEX performing in cats. Eleven healthy cats were recruited; baseline sedative score, systolic arterial pressure, electrocardiography, and vasovagal tonus index (VVTI) were assessed, and repeated after ten minutes of DEX 5μg/kg intramuscularly (IM). A smooth sedation was noticed, and emesis and sialorrhea were common adverse effects, observed on average seven minutes after IM injection. Furthermore, electrocardiographic effects of a low dose of DEX mainly include decreases on heart rate, and increases on T-wave amplitude. The augmentation on VVTI and appearance of respiratory sinus arrhythmia, as well as sinus bradycardia in some cats, suggesting that DEX enhances parasympathetic tonus in healthy cats, and therefore will be best avoid in patients at risk for bradycardia.

Antinociceptive efficacy and respiratory effects of dexmedetomidine in ball pythons (Python regius)

OBJECTIVE To determine antinociceptive efficacy, behavioral patterns, and respiratory effects associated with dexmedetomidine administration in ball pythons (Python regius). ANIMALS 12 ball pythons. PROCEDURES Antinociception was assessed by applying an infrared heat stimulus to the cranioventral surface of snakes during 2 experiments. Thermal withdrawal latency was measured at 0, 2, and 24 hours after SC injections of dexmedetomidine (0.1 or 0.2 mg/kg) or saline (0.9% NaCl) solution and at 0 to 60 minutes after injection of dexmedetomidine (0.1 mg/kg) or saline solution. Behaviors were recorded at 0, 2, and 24 hours after administration of dexmedetomidine (0.1 mg/kg) or saline solution. Tongue flicking, head flinch to the approach of an observer's hand, movement, and righting reflex were scored. Respiratory frequency was measured by use of plethysmography to detect breathing-related movements after injection of dexmedetomidine (0.1 mg/kg) or saline solution. RESULTS Mean baseline withdrawal latency was 5 to 7 seconds; saline solution did not alter withdrawal latency. Dexmedetomidine increased withdrawal latency by 18 seconds (0.2 mg/kg) and 13 seconds (0.1 mg/kg) above baseline values at 2 hours. Increased withdrawal latency was detected within 15 minutes after dexmedetomidine administration. At 2 hours after injection, there were few differences in behavioral scores. Dexmedetomidine injection depressed respiratory frequency by 55% to 70%, compared with results for saline solution, but snakes continued to breathe without prolonged apnea. CONCLUSIONS AND CLINICAL RELEVANCE Dexmedetomidine increased noxious thermal withdrawal latency without causing excessive sedation. Therefore, dexmedetomidine may be a useful analgesic drug in ball pythons and other snake species.

Cardiovascular, respiratory and sedative effects of intramuscular alfaxalone, butorphanol and dexmedetomidine compared with ketamine, butorphanol and dexmedetomidine in healthy cats

Objectives The aim of the study was to evaluate the cardiorespiratory effects, quality of sedation and recovery of intramuscular alfaxalone-dexmedetomidine-butorphanol (ADB) and ketamine-dexmedetomidine-butorphanol (KDB), in cats. Methods Nine adult, healthy cats (6.63 ± 1.42 kg) were enrolled in a blinded, randomized, crossover experimental design. Cats were sedated twice intramuscularly, once with ADB (alfaxalone 1 mg/kg, dexmedetomidine 0.005 mg/kg, butorphanol 0.2 mg/kg), and once with KDB (ketamine 5 mg/kg, dexmedetomidine 0.005 mg/kg, butorphanol 0.2 mg/kg), in random order. Data collected included heart rate (HR), arterial blood pressure and blood gas analysis, respiratory rate and sedation score. Analysis of variance with Bonferroni post-hoc correction was used for parametric data, and a Wilcoxon signed rank test was used for non-parametric data. Significance was set at P <0.05. Results Total sedation time was shorter for ADB (90.71 ± 15.12 mins vs 147.00 ± 47.75 mins). Peak sedation was observed within 15 mins in both groups. Quality of recovery was excellent in both groups. HR decreased over time in both groups. Diastolic and mean arterial pressure decreased over time for ADB, becoming significant after 30 mins. All cardiovascular variables were within the clinically acceptable range in both groups. Arterial partial pressure of oxygen was significantly decreased from baseline for KDB at all time points (73 ± 2.5 mmHg [9.7 ± 0.3 kPa] vs ADB 83 ± 2.6 mmHg [11 ± 0.3 kPa]). Hypoventilation was not observed. Conclusions and relevance Both protocols produced acceptable cardiovascular stability. Sedation and recovery quality were good, albeit sedation was shorter with ADB. Although oxygenation was better maintained in the ADB group, all sedated cats should receive oxygen supplementation.

Effects of sedation with dexmedetomidine and buprenorphine on echocardiographic variables, blood pressure and heart rate in healthy cats

Objectives Sedative agents are occasionally used to enable echocardiographic examination when screening cats for heart disease, such as hypertrophic cardiomyopathy (HCM). Owing to their haemodynamic effects, sedative agents may alter echocardiographic measurements. The aim of the study was to evaluate the effects of the sedative combination dexmedetomidine and buprenorphine on echocardiographic variables, blood pressure (BP) and heart rate (HR) in healthy cats. Methods Fifty healthy, client-owned cats were prospectively recruited and included after physical examination. Cats were sedated intramuscularly with dexmedetomidine and buprenorphine, according to body weight. Blood pressure and HR measurements, echocardiographic and Doppler examinations were performed prior to sedation and repeated once cats had achieved acceptable sedation. Results Left ventricular internal diameter at end-diastole and systole, right ventricular internal diameter at end-diastole, left atrium (LA), pulmonary artery (PA) deceleration time, and systolic, diastolic and mean arterial blood pressure increased after sedation ( P ⩽0.022). Aortic and PA maximum velocity, fractional shortening, PA acceleration/deceleration time and HR decreased after sedation ( P <0.0001). Interventricular septum at end-diastole and systole, left ventricular posterior wall at end-diastole and systole, aortic diameter (Ao), left atrial/aortic diameter (LA/Ao) and pulmonic acceleration time did not change. Conclusions and relevance Blood pressure increased and HR decreased post-sedation. While wall thickness and LA/Ao were not affected by sedation, indices of LA and left ventricular size increased. Further studies are needed using cats with HCM to assess the effect of this sedative combination on HCM screening results.

Comparison of intramuscular butorphanol and buprenorphine combined with dexmedetomidine for sedation in cats

Objectives The objective of this study was to compare the sedative effect of butorphanol-dexmedetomidine with buprenorphine-dexmedetomidine following intramuscular (IM) administration in cats. Methods Using a prospective, randomised, blinded design, 40 client-owned adult cats were assigned to receive IM dexmedetomidine (10 µg/kg) combined with either butorphanol (0.4 mg/kg) ('BUT' group) or buprenorphine (20 µg/kg) ('BUP' group). Sedation was scored using a previously published multidimensional composite scale before administration (T0) and 5, 10, 15 and 20 mins afterwards (T5, T10, T15 and T20, respectively). Alfaxalone (1.5 mg/kg) was administered IM at T20 if the cat was not deemed adequately sedated to place an intravenous catheter. Adverse events were recorded. Friedman two-way ANOVA analysed sedation scores within groups. Mann-Whitney Rank Sum test compared sedation scores between groups; Fisher's exact test analysed the frequency of alfaxalone administration and adverse events. P <0.05 was considered statistically significant. Results Sedation scores between groups were similar at baseline, but at T5, T10, T15 and T20 scores were higher in the BUT group ( P <0.01). Within both groups, sedation scores changed over time and the highest sedation scores were reached at T10. Requirement for additional sedation was similar between groups: two cats in the BUT group and five cats in the BUP group. One cat and 11 cats vomited ( P = 0.002) in the BUT and BUP groups, respectively. No other adverse events were recorded. Conclusions and relevance At these doses, IM buprenorphine-dexmedetomidine provides inferior sedation and a higher incidence of vomiting than butorphanol-dexmedetomidine in cats. Butorphanol-dexmedetomidine may be preferred for feline sedation, especially where vomiting is contraindicated.

Assessing analgesia equivalence and appetite following alfaxalone- or ketamine-based injectable anesthesia for feline castration as an example of enhanced recovery after surgery

Objectives The primary study objective was to assess two injectable anesthetic protocols, given to facilitate castration surgery in cats, for equivalence in terms of postoperative analgesia. A secondary objective was to evaluate postoperative eating behavior. Methods Male cats presented to a local clinic were randomly assigned to receive either intramuscular ketamine (5 mg/kg, n = 26; KetHD) or alfaxalone (2 mg/kg, n = 24; AlfHD) in combination with dexmedetomidine (25 μg/kg) and hydromorphone (0.05 mg/kg). All cats received meloxicam (0.3 mg/kg SC) and intratesticular lidocaine (2 mg/kg). Species-specific pain and sedation scales were applied at baseline, 1, 2 and 4 h postoperatively. Time taken to achieve sternal recumbency and begin eating were also recorded postoperatively. Results Pain scale scores were low and showed equivalence between the treatment groups at all time points (1 h, P = 0.38, 95% confidence interval [CI] of the difference between group scores 0-0; 2 h, P = 0.71, 95% CI 0-0; 4 h, P = 0.97, 95% CI 0-0). Four cats crossed the threshold for rescue analgesia (KetHD, n = 1; AlfHD, n = 3). At 1 h, more cats in the KetHD (65%) group than in the AlfHD (42%) group were sedated, but statistical significance was not detected ( P = 0.15, 95% CI -1 to 0). Most AlfHD cats (88%) began eating by 1 h vs 65% of KetHD cats ( P = 0.039). Time to recover sternal recumbency did not differ between groups ( P = 0.86, 95% CI -14.1 to 11.8). Conclusions and relevance These results show that AlfHD and KetHD provide equivalent analgesia as part of a multimodal injectable anesthetic protocol. Alfaxalone is associated with an earlier return to eating.

Comparison of two sedation protocols for short electroretinography in cats

Objectives The objectives were to compare two different sedative combinations, xylazine-ketamine and dexmedetomidine-ketamine, for the short electroretinography (ERG) protocol and their impact on sedative effect, reversal times and physiological variables in cats. Methods Six healthy spayed female domestic cats were sedated using one of two ketamine-containing protocols: intramuscular xylazine hydrochloride (1 mg/kg) plus ketamine hydrochloride (3 mg/kg) (XK), and dexmedetomidine hydrochloride (5 µg/kg) plus ketamine hydrochloride (3 mg/kg) (DK). A short ERG protocol was recorded from the left eye of each cat under XK and DK sedation. Thirty minutes later, the effects were reversed with yohimbine or atipamezole for the XK and DK treatment, respectively. The cats were evaluated for time to recumbency, time to head elevation, and time to standing position after reversal treatments. Other variables recorded were: systolic blood pressure, cardiac rhythm, heart rate, pulse oximetry and respiratory rate. Recorded ERG variables included a- and b-wave amplitudes and implicit times under photopic, scotopic and scotopic mixed ERG conditions. Results Time to lateral recumbency with XK was shorter than for DK ( P <0.05). After reversal, head elevation and standing position times were significantly longer for the XK than the DK group ( P <0.05). Heart rate increased and systolic blood pressure decreased from baseline in both groups ( P <0.05), but there were no significant differences between treatment groups. The b-wave amplitude recorded in the photopic study of cats treated with XK was lower than in animals treated with DK ( P <0.05). No other significant differences in ERG variables were observed between treatment groups ( P >0.05). Conclusions and relevance The present study shows that XK and DK treatments are chemical restraint alternatives for ERG recording in cats, with significant differences only in the photopic b-wave amplitude.

Comparison of intramuscular alfaxalone and ketamine combined with dexmedetomidine and butorphanol for castration in cats

Objectives Cardiorespiratory parameters and anaesthesia quality in cats anaesthetised with either intramuscular (IM) alfaxalone or ketamine both combined with dexmedetomidine and butorphanol for castration were evaluated. Methods Thirty-two client-owned cats were randomly assigned to receive either alfaxalone (A; 3 mg/kg IM) or ketamine (K; 5 mg/kg IM), combined with dexmedetomidine (10 μg/kg) and butorphanol (0.2 mg/kg). Heart rate (HR), respiratory rate (RR) and rectal temperature (T°) were recorded prior to drug administration. Pulse rate (PR) and RR were recorded 10 (T10) and 15 (T15) mins after injection (T0). Cardiorespiratory values (PR, RR, SPO2, blood pressure, PE'CO2) were recorded every 5 mins for the duration of the procedure. Pain at injection, intubation and recovery were evaluated with simple descriptive scores. Feasibility of anaesthesia was evaluated by the number of top-ups of anaesthetic needed. Cat attitude, ability to walk and presence of ataxia were assessed several times after extubation (Texmin) and the time between injection and extubation recorded. Pain was assessed at Tex120 and Tex240 with the 4Avet-pain score. Results The RR was significantly lower in group K at T10 (RRK = 28 ±13.35 breaths per minute [brpm], RRA= 43.24 ±7.04 brpm) and T15 (RRK = 28 ±11.53 brpm vs RRA = 43 ±12.18 brpm). Time to extubation was significantly longer in group A (TA = 62 ±14.6 mins, TK = 45.13 ± 7.38 mins). Cats in group K needed more top-ups, were more ataxic at Tex120, had a worse recovery score at Tex60 and were less willing to walk at Tex30. Conclusions and relevance Cats receiving alfaxalone had a longer but better quality recovery. Cardiorespiratory parameters were stable and within clinically acceptable values following IM injection of either alfaxalone or ketamine in healthy cats. Intramuscular alfaxalone is a suitable alternative to ketamine for short procedures requiring anaesthesia when used in combination with dexmedetomidine and butorphanol.

Adverse reactions of α2-adrenoceptor agonists in cats reported in 2003-2013 in Finland

OBJECTIVE

To describe suspected adverse drug reactions in cats associated with use of α₂-adrenoceptor agonists.

STUDY DESIGN

Retrospective study.

ANIMALS

A total of 90 cats.

METHODS

Data were collected from reports on adverse reactions to veterinary medicines sent to the Finnish Medicines Agency during 2003-2013. All reports of suspected adverse reactions associated with use of α₂-adrenoceptor agonists in cats were included. Probable pulmonary oedema was diagnosed based on post mortem or radiological examination, or presence of frothy or excess fluid from the nostrils or trachea. If only dyspnoea and crackles on auscultation were reported, possible pulmonary oedema was presumed.

RESULTS

Pulmonary oedema was suspected in 61 cases. Of these cats, 37 were categorised as probable and 24 as possible pulmonary oedema. The first clinical signs had been noted between 1 minute and 2 days (median, 15 minutes) after α₂-adrenoceptor agonist administration. Many cats probably had no intravenous overhydration when the first clinical signs were detected, as either they presumably had no intravenous cannula or the signs appeared before, during or immediately after cannulation. Of the 61 cats, 43 survived, 14 died and for four the outcome was not clearly stated.

CONCLUSIONS AND CLINICAL RELEVANCE

Pulmonary oedema is a perilous condition that may appear within minutes of an intramuscular administration of sedative or anaesthetic agent in cats. The symptoms were not caused by intravenous overhydration, at least in cats having no venous cannula when the first clinical signs were detected.

CARDIORESPIRATORY EFFECTS OF DEXMEDETOMIDINE-BUTORPHANOL-MIDAZOLAM (DBM): A FULLY REVERSIBLE ANESTHETIC PROTOCOL IN CAPTIVE AND SEMI-FREE-RANGING CHEETAHS (ACINONYX JUBATUS)

Multiple anesthesia protocols have been used in the cheetah ( Acinonyx jubatus ). Twenty healthy, captive cheetahs were immobilized with dexmedetomidine (15.8 ± 1.9 μg/kg), butorphanol (0.22 ± 0.03 mg/kg), and midazolam (0.18 ± 0.03 mg/kg) by intramuscular injection. Induction, recumbency, and recovery times were recorded, and physiologic parameters were monitored. Anesthesia was antagonized with atipamezole (0.125 ± 0.02 mg/kg) and naltrexone (0.1 ± 0.014 mg/kg) intramuscularly. All cheetahs were safely anesthetized with this protocol. Cheetahs were laterally recumbent by 8 ± 3.5 min. Cardiorespiratory values were stable throughout the length of anesthesia. Moderate hypertension, with systolic blood pressure ranging from 178 ± 19.8 mm Hg, was initially observed but decreased over time. There was a statistical decreasing trend in temperature; SpO2; and systolic, mean, and diastolic blood pressure, but not in heart rate and end-tidal CO₂. Recoveries were rapid, with cheetahs standing by 11.3 ± 5.7 min postreversal administration. This is the first report of a dexmedetomidine-butorphanol-midazolam anesthetic combination in cheetahs. Overall, this anesthetic protocol proved to be safe and effective.

Injectable anaesthesia for adult cat and kitten castration: effects of medetomidine, dexmedetomidine and atipamezole on recovery

Objectives Rapid recovery from injectable anaesthesia benefits cat shelter neutering programmes. The effects of medetomidine, dexmedetomidine and atipamezole on recovery were evaluated in adult cats and kittens (⩽6 months old). Methods One hundred healthy male cats (age range 2-66 months, weight range 0.7-5.3 kg) admitted forneutering were randomly allocated to groups of 25. Anaesthesia was induced with 60 mg/m2 ketamine, 180 µg/m2 buprenorphine, 3 mg/m2 midazolam and either 600 µg/m2 medetomidine (groups M and MA) or 300 µg/m2 dexmedetomidine (groups D and DA) intramuscularly (IM). Groups MA and DA also received 1.5 mg/m2 atipamezole IM after 40 mins. Preparation time, surgical time, and times to sternal recumbency and standing were recorded. Data were analysed using the Kruskall-Wallis test, unpaired t-tests and ANOVA. Statistical significance was deemed to be P ⩽0.05. Results Groups did not differ significantly in age, body weight, preparation or surgical time. The time to sternal recumbency in group MA (64 ± 34 mins) was less than in group M (129 ± 32 mins), and in group DA it was less than in group D (54 ± 6 mins vs 110 ± 27 mins) ( P <0.001). There were no differences in duration of recovery to sternal recumbency between groups M and D or MA and DA. The time to standing in group MA (79 ± 51 mins) was less than in group M (150 ± 38 mins) ( P <0.001), and in group DA it was less than in group D (70 ± 22 mins vs 126 ± 27 mins) ( P <0.01). Time to standing in group D (126 ± 27 mins) was less than in group M (150 ± 38 mins) (P <0.05). Time to standing in groups DA and MA were not different. Kittens recovered faster than adults after atipamezole. Minimal adverse effects were seen. Conclusions and relevance Atipamezole reliably reduced recovery time after anaesthesia incorporating either dexmedetomidine or medetomidine; however, the choice of dexmedetomidine or medetomidine had little effect. Recovery was faster in kittens.

Combinations of dexmedetomidine and alfaxalone with butorphanol in cats: application of an innovative stepwise optimisation method to identify optimal clinical doses for intramuscular anaesthesia

OBJECTIVES

The aim of this study was to optimise dexmedetomidine and alfaxalone dosing, for intramuscular administration with butorphanol, to perform minor surgeries in cats.

METHODS

Initially, cats were assigned to one of five groups, each composed of six animals and receiving, in addition to 0.3 mg/kg butorphanol intramuscularly, one of the following: (A) 0.005 mg/kg dexmedetomidine, 2 mg/kg alfaxalone; (B) 0.008 mg/kg dexmedetomidine, 1.5 mg/kg alfaxalone; (C) 0.012 mg/kg dexmedetomidine, 1 mg/kg alfaxalone; (D) 0.005 mg/kg dexmedetomidine, 1 mg/kg alfaxalone; and (E) 0.012 mg/kg dexmedetomidine, 2 mg/kg alfaxalone. Thereafter, a modified 'direct search' method, conducted in a stepwise manner, was used to optimise drug dosing. The quality of anaesthesia was evaluated on the basis of composite scores (one for anaesthesia and one for recovery), visual analogue scales and the propofol requirement to suppress spontaneous movements. The medians or means of these variables were used to rank the treatments; 'unsatisfactory' and 'promising' combinations were identified to calculate, through the equation first described by Berenbaum in 1990, new dexmedetomidine and alfaxalone doses to be tested in the next step. At each step, five combinations (one new plus the best previous four) were tested.

RESULTS

None of the tested combinations resulted in adverse effects. Four steps and 120 animals were necessary to identify the optimal drug combination (0.014 mg/kg dexmedetomidine, 2.5 mg/kg alfaxalone and 0.3 mg/kg butorphanol).

CONCLUSIONS AND RELEVANCE

The investigated drug mixture, at the doses found with the optimisation method, is suitable for cats undergoing minor clinical procedures.

Effects of ketamine and alfaxalone on application of a feline pain assessment scale

OBJECTIVES

The objective of this study was to compare the effects of ketamine and alfaxalone on the application of a validated feline-specific multidimensional composite pain scale (UNESP-Botucatu MCPS).

METHODS

In a prospective, randomized, blinded, crossover trial, 11 adult cats (weight 4.4 ± 0.6 kg) were given dexmedetomidine (15 μg/kg) and hydromorphone (0.05 mg/kg) with either alfaxalone (2 mg/kg) or ketamine (5 mg/kg) as a single intramuscular injection for the induction of general anesthesia. After orotracheal intubation, general anesthesia (without surgery) was maintained for 32 mins with isoflurane, followed by atipamezole. The following parameters were recorded at baseline, 1-8 h and 24 h post-extubation: pain (pain expression and psychomotor subscales) and sedation scale scores. Alfaxalone treatment injection sites were examined for inflammation at baseline, postinjection, and 8 h and 24 h post-extubation.

RESULTS

Psychomotor scores were higher with ketamine at hours 1 (3.5 [0-5.0], P <0.0001), 2 (2.5 [0-4.0], P <0.0001) and 3 (0.5 [0-4.0], P = 0.009) post-extubation compared with alfaxalone (hour 1, 0 [0-2]; hour 2, 0 [0-0]; hour 3, 0 [0-0]). Six cats in the ketamine group crossed the analgesic intervention threshold. In contrast, pain expression scores did not differ significantly between treatments at any time (P >0.05); one cat from each group crossed the analgesic intervention threshold. Sedation was greater with ketamine (1 [0-3], P = 0.02) than alfaxalone (0 [0-1]) 1 h post-extubation. No cats had visible inflammation at the injection sites at any time.

CONCLUSIONS AND RELEVANCE

Ketamine has a confounding effect on the psychomotor subscale of the pain scale studied, which may lead to erroneous administration of rescue analgesia. In contrast, alfaxalone was not associated with significant increases in either pain subscale. These effects of ketamine should be considered when evaluating acute postoperative pain in cats.

Accidental alfaxalone overdose in a mature cat undergoing anaesthesia for magnetic resonance imaging

Case summary This case report describes the clinical signs and treatment of an alfaxalone 10 times overdose in a 12-year-old cat undergoing anaesthesia for MRI. The cat was discharged from hospital following a prolonged recovery including obtunded mentation and cardiorespiratory depression for several hours following cessation of anaesthesia. The cat received supportive therapy that included supplemental oxygen via a face mask, intravenous crystalloid fluids and active rewarming. The benefits of using alfaxalone for maintenance of anaesthesia, its pharmacokinetics and previously reported lethal doses are discussed. Strategies for reducing the incidence of medication errors are presented. Relevance and novel information An unintentional overdose of alfaxalone by continuous rate infusion has not been reported previously in a cat. Treatment is supportive and directed towards maintenance of the cardiorespiratory systems. Whenever possible, smart pumps that have been designed to reduce human error should be used to help prevent medication errors associated with continuous rate infusions.

Evaluation and optimisation of propofol pharmacokinetic parameters in cats for target-controlled infusion

The aim of this study was to develop and evaluate a pharmacokinetic model-driven infusion of propofol in premedicated cats. In a first step, propofol (10 mg/kg) was administered intravenously over 60 seconds to induce anaesthesia for the elective neutering of seven healthy cats, premedicated intramuscularly with 0.3 mg/kg methadone, 0.01 mg/kg medetomidine and 2 mg/kg ketamine. Venous blood samples were collected over 240 minutes, and propofol concentrations were measured via a validated high-performance liquid chromatography assay. Selected pharmacokinetic parameters, determined by a three-compartment open linear model, were entered into a computer-controlled infusion pump (target-controlled infusion-1 (TCI-1)). In a second step, TCI-1 was used to induce and maintain general anaesthesia in nine cats undergoing neutering. Predicted and measured plasma concentrations of propofol were compared at specific time points. In a third step, the pharmacokinetic parameters were modified according to the results from the use of TCI-1 and were evaluated again in six cats. For this TCI-2 group, the median values of median performance error and median absolute performance error were -1.85 per cent and 29.67 per cent, respectively, indicating that it performed adequately. Neither hypotension nor respiratory depression was observed during TCI-1 and TCI-2. Mean anaesthesia time and time to extubation in the TCI-2 group were 73.90 (±20.29) and 8.04 (±5.46) minutes, respectively.

Sedative effects of intramuscular alfaxalone administered to cats

The sedative effects of intramuscular (IM) alfaxalone in 2-hydroxypropyl-beta-cyclodextrin (alfaxalone-HPCD) were evaluated in cats. The cats were treated with alfaxalone-HPCD in five occasions with a minimum 14-day interval between treatments: an IM injection of 1.0 mg/kg (IM1), 2.5 mg/kg (IM2.5), 5 mg/kg (IM5) or 10 mg/kg (IM10), or an intravenous injection of 5 mg/kg (IV5). The sedative effects were evaluated subjectively using a composite measurement scoring system (a maximum score of 16). Cardio-respiratory variables were measured non-invasively. The median sedation scores peaked at 10 min (score 9), 15 min (score 14), 10 min (score 16), 10 to 20 min (score 16) and 2 to 5 min (score 16) after the IM1, IM2.5, IM5, IM10 and IV5 treatments, respectively. The IM5 treatment produced longer lasting sedation, compared to the IV5 treatment. Durations of maintenance of lateral recumbency after the IM10 treatment (115 ± 22 min) were longer than those after the IM2.5 (40 ± 15 min), IM5 (76 ± 21 min) and IV5 treatments (50 ± 5 min). Cardio-respiratory variables remained within clinically acceptable ranges, except for each one cat that showed hypotension (<60 mmHg) after the IM10 and IV5 treatments. Tremors, ataxia and opisthotonus-like posture were observed during the early recovery period after the IM2.5, IM5, IM10 and IV5 treatments. In conclusion, IM alfaxalone-HPCD produced dose-dependent and clinically relevant sedative effect at 2.5 to 10 mg/kg in healthy cats. Hypotension may occur at higher IM doses of alfaxalone-HPCD.