Effects of vatinoxan in dogs premedicated with medetomidine and butorphanol followed by sevoflurane anaesthesia: a randomized clinical study

OBJECTIVE

To investigate effects of vatinoxan in dogs, when administered as intravenous (IV) premedication with medetomidine and butorphanol before anaesthesia for surgical castration.

STUDY DESIGN

A randomized, controlled, blinded, clinical trial.

ANIMALS

A total of 28 client-owned dogs.

METHODS

Dogs were premedicated with medetomidine (0.125 mg m^-2) and butorphanol (0.2 mg kg^-1) (group MB; n = 14), or medetomidine (0.25 mg m^-2), butorphanol (0.2 mg kg^-1) and vatinoxan (5 mg m^-2) (group MB-VATI; n = 14). Anaesthesia was induced 15 minutes later with propofol and maintained with sevoflurane in oxygen (targeting 1.3%). Before surgical incision, lidocaine (2 mg kg^-1) was injected intratesticularly. At the end of the procedure, meloxicam (0.2 mg kg^-1) was administered IV. The level of sedation, the qualities of induction, intubation and recovery, and Glasgow Composite Pain Scale short form (GCPS-SF) were assessed. Heart rate (HR), respiratory rate (f_R), mean arterial pressure (MAP), end-tidal concentration of sevoflurane (Fe'Sevo) and carbon dioxide (Pe'CO₂) were recorded. Blood samples were collected at 10 and 30 minutes after premedication for plasma medetomidine and butorphanol concentrations.

RESULTS

At the beginning of surgery, HR was 61 ± 16 and 93 ± 23 beats minute^-1 (p = 0.001), and MAP was 78 ± 7 and 56 ± 7 mmHg (p = 0.001) in MB and MB-VATI groups, respectively. No differences were detected in f_R, Pe'CO₂, Fe'Sevo, the level of sedation, the qualities of induction, intubation and recovery, or in GCPS-SF. Plasma medetomidine concentrations were higher in group MB-VATI than in MB at 10 minutes (p = 0.002) and 30 minutes (p = 0.0001). Plasma butorphanol concentrations were not different between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

In group MB, HR was significantly lower than in group MB-VATI. Hypotension detected in group MB-VATI during sevoflurane anaesthesia was clinically the most significant difference between groups.

Clinical review of the pharmacological and anaesthetic effects of alfaxalone in dogs

This clinical review summarises the pharmacological and anaesthetic properties of alfaxalone in the dog. Available pharmacokinetic-pharmacodynamic data and factors affecting the induction dose have been reported. Furthermore, quality of induction and recovery after alfaxalone administration, the use of alfaxalone for total intravenous anaesthesia, and its effects on the cardio-respiratory system, on laryngeal motion, on intraocular pressure and tear production have been evaluated. Finally, the use of alfaxalone in dogs undergoing caesarean section and the effect of intramuscular alfaxalone administration have been considered.

Effects of sevoflurane, propofol or alfaxalone on neuromuscular blockade produced by a single intravenous bolus of rocuronium in dogs

OBJECTIVE

To compare the effects of sevoflurane, propofol and alfaxalone on the neuromuscular blockade induced by a single intravenous bolus of rocuronium in dogs.

STUDY DESIGN

A randomized, prospective, crossover experimental study.

ANIMALS

A total of eight adult Beagle dogs (four female, four male), weighing 8.9-15.3 kg and aged 5-7 years.

METHODS

The dogs were anesthetized three times with 1.25× minimum alveolar concentration of sevoflurane (SEVO treatment) and 1.25× minimum infusion rate of propofol (PROP treatment) or alfaxalone (ALFX treatment) at intervals of ≥14 days. Neuromuscular function was monitored with train-of-four (TOF) stimulation of the peroneal nerve by acceleromyography. After recording the control TOF ratio (TOFRC), a single bolus dose of rocuronium (1 mg kg^-1) was administered intravenously. The times from rocuronium administration to achieving TOF count 0 (onset time), from achieving TOF count 0 to the reappearance of TOF count 4 (clinical blockade period), from 25% to 75% of TOFRC (recovery index) and from achieving TOF count 0 to TOF ratio/TOFRC >0.9 (total neuromuscular blockade duration) were recorded.

RESULTS

The onset time and recovery index did not differ among the treatments. The median clinical blockade period was longer in the SEVO treatment [27.3 (26.0-30.3) minutes] than in PROP [16.6 (15.4-18.0) minutes; p = 0.002] and ALFX [22.4 (18.6-23.1) minutes; p = 0.017] treatments; and longer in the ALFX treatment than in the PROP treatment (p = 0.020). The mean total neuromuscular blockade duration was longer in the SEVO treatment (43.7 ± 9.9 minutes) than in PROP (25.1 ± 2.7 minutes; p < 0.001) and ALFX (32.5 ± 8.4 minutes; p = 0.036) treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Compared with alfaxalone and propofol, sevoflurane prolonged rocuronium-induced neuromuscular blockade by a significantly greater extent in dogs.

Perioperative pharmacokinetics and pharmacodynamics of meloxicam in emus (Dromaius novaehollandiae) of different age groups using nonlinear mixed effect modelling

Meloxicam is a widely used nonsteroidal anti-inflammatory drug in avian species. However, variability in pharmacokinetic (PK) and pharmacodynamic (PD) parameters in birds warrants species-specific studies for dose and dosing interval optimization. We performed a perioperative PK study of meloxicam (0.5 mg/kg, intravenously) on emus of three different age groups: 3 chicks (5 weeks old, 3.5 kg), 4 juveniles (26 weeks old, 18.8 kg) and 6 adults (66 weeks old, 38.8 kg). A two-compartment population PK model including weight as a significant covariate on clearance and central volume of distribution (V1) best fitted the data. The typical values (20 kg bird) for clearance and V1 were 0.54 L/kg/h and 0.095 L/kg. Both parameters significantly decreased with increasing weight/age. Meloxicam potency and selectivity for COX-1 and COX-2 were measured in whole blood assays (TxB₂ production endpoint). Meloxicam was partially selective in emus (IC₅₀ COX-1:COX-2 = 9.1:1). At the current empirical dose (0.5 mg/kg/24 hr), plasma meloxicam concentration is above IC₅₀ of COX-2 for only 2 hr. PK/PD predicted dose required for 80% COX-2 inhibition over 24 hr were 3.4, 1.4 and 0.95 L/kg/day in chicks, juveniles and adult emus, respectively. The safety, therapeutic efficacy and practicality of modifying the daily dose or dose interval should be considered for dose recommendations in emus.

Sedative and cardiorespiratory effects of intramuscular administration of alfaxalone and butorphanol combined with acepromazine, midazolam, or dexmedetomidine in dogs

OBJECTIVE

To evaluate the sedative and cardiorespiratory effects of IM administration of alfaxalone and butorphanol combined with acepromazine, midazolam, or dexmedetomidine in dogs.

ANIMALS

6 young healthy mixed-breed hounds.

PROCEDURES

Dogs received each of 3 treatments (alfaxalone [2 mg/kg] and butorphanol [0.4 mg/kg] combined with acepromazine [0.02 mg/kg; AB-ace], midazolam [0.2 mg/kg; AB-mid], or dexmedetomidine [0.005 mg/kg; AB-dex], IM) in a blinded, randomized crossover-design study with a 1-week washout period between treatments. Sedation scores and cardiorespiratory variables were recorded at predetermined time points. Data were analyzed by use of mixed-model ANOVA and linear generalized estimating equations with post hoc adjustments.

RESULTS

All treatments resulted in moderate to deep sedation (median score, ≥ 15/21) ≤ 5 minutes after injection. Sedation scores did not differ among treatments until the 40-minute time point, when the score was higher for AB-dex than for other treatments. Administration of AB-dex resulted in median scores reflecting deep sedation until 130 minutes, versus 80 and 60 minutes for AB-ace and AB-mid, respectively, after injection. Heart rate, cardiac output, and oxygen delivery decreased significantly after AB-dex, but not AB-ace or AB-mid administration. Respiratory variables remained within clinically acceptable ranges after all treatments. Undesirable recovery characteristics were observed in 4 dogs after AB-mid treatment. Four dogs required atipamezole administration 180 minutes after AB-dex injection.

CONCLUSIONS AND CLINICAL RELEVANCE

All protocols produced reliable sedation. The results indicated that in young, healthy dogs, AB-mid may produce undesirable recovery characteristics; AB-dex treatment caused cardiovascular depression and should be used with caution.

A possible solution to model nonlinearity in elimination and distributional clearances with α2 -adrenergic receptor agonists: Example of the intravenous detomidine and methadone combination in sedated horses

The alpha(α)₂ -agonist detomidine is used for equine sedation with opioids such as methadone. We retrieved the data from two randomized, crossover studies where detomidine and methadone were given intravenously alone or combined as boli (STUDY 1) (Gozalo-Marcilla et al., 2017, Veterinary Anaesthesia and Analgesia, 2017, 44, 1116) or as 2-hr constant rate infusions (STUDY 2) (Gozalo-Marcilla et al., 2019, Equine Veterinary Journal, 51, 530). Plasma drug concentrations were measured with a validated tandem Mass Spectrometry assay. We used nonlinear mixed effect modelling and took pharmacokinetic (PK) data from both studies to fit simultaneously both drugs and explore their nonlinear kinetics. Two significant improvements over the classical mammillary two-compartment model were identified. First, the inclusion of an effect of detomidine plasma concentration on the elimination clearances (Cls) of both drugs improved the fit of detomidine (Objective Function Value [OFV]: -160) and methadone (OFV: -132) submodels. Second, a detomidine concentration-dependent reduction of distributional Cls of each drug further improved detomidine (OFV: -60) and methadone (OFV: -52) submodel fits. Using the PK data from both studies (a) helped exploring hypotheses on the nonlinearity of the elimination and distributional Cls and (b) allowed inclusion of dynamic effects of detomidine plasma concentration in the model which are compatible with the pharmacology of detomidine (vasoconstriction and reduction in cardiac output).

Alfaxalone total intravenous anaesthesia in dogs: pharmacokinetics, cardiovascular data and recovery characteristics

OBJECTIVE

To evaluate the cardiovascular effects, pharmacokinetic (PK) data and recovery characteristics of an alfaxalone constant rate infusion (CRI) of different duration in dogs at manufacturer's recommended dose rate.

STUDY DESIGN

Experimental, prospective, randomized, crossover study.

ANIMALS

Six intact female Beagles.

METHODS

Following an intravenous alfaxalone bolus (3 mg kg^-1), anaesthesia was maintained using an alfaxalone CRI at 0.15 mg kg^-1 minute^-1 for 90 (short CRI) or 180 minutes (long CRI). Venous blood samples were collected to determine the PK profile. Cardiovascular variables and recovery characteristics were evaluated. Recovery was scored on a scale ranging from 0, excellent to 4, bad. A mixed-model statistical approach was used to compare the cardiovascular parameters (global α = 0.05). An analysis of variance was performed to compare PK parameters and recovery times between treatments.

RESULTS

No significant difference was noted between protocols for any PK parameter. Volume of distribution at steady state (935.74 ± 170.25 versus 1119.15 ± 190.65 mL kg^-1), elimination half-life (12 ± 2 versus 13 ± 3 minutes), clearance from the central compartment (26.02 ± 4.41 versus 27.74 ± 5.65 mL kg^-1 minute^-1) and intercompartmental clearance (8.47 ± 4.06 versus 12.58 ± 7.03 mL kg^-1 minute^-1) were comparable for short CRI and long CRI. Cardiovascular variables remained within physiological limits. Mechanical ventilation was necessary (short CRI: n = 1, long CRI: n = 4). The manufacturer's recommended dose rate resulted in a light plane of anaesthesia. No significant differences in recovery times and scores were observed between treatments. The quality of recovery was scored as very poor with both protocols.

CONCLUSIONS AND CLINICAL RELEVANCE

PK data were similar between long and short infusions of alfaxalone at the manufacturer's recommended dose, with acceptable cardiovascular conditions. Nevertheless, both protocols resulted in a superficial plane of general anaesthesia with poor recovery characteristics.

A controlled randomized clinical trial to assess postoperative analgesia after thiopental-isoflurane anaesthesia or total intravenous anaesthesia with alfaxalone in dogs

Alfaxalone, a synthetic neuroactive steroid, has been attributed with properties including sedation, anaesthesia and analgesia. The clinical relevance of any analgesic properties of alfaxalone has not been demonstrated. This study was a prospective, blinded, randomized, negative control clinical trial in 65 healthy dogs presented for ovariohysterectomy. Anaesthesia was induced and maintained, for Group 1 (TIVA) dogs (n = 30) with intravenous alfaxalone alone and for Group 2 dogs (n = 35) with thiopental followed by isoflurane in 100% oxygen inhalation. After ovariohysterectomy, quantitative measures of pain or nociception were recorded at 15 min intervals for 4 hr using three independent scoring systems, a composite measure pain scale (CMPS), von Frey threshold testing and measures of fentanyl rescue analgesia. The mean CMPS scores of Group 2 (THIO/ISO) dogs remained higher than Group 1 (TIVA) dogs from 15 to 135 min post-surgery but this difference was not statistically significant. There were no significant differences between groups in the proportions of dogs requiring rescue fentanyl analgesia, the total fentanyl dose used or the time to first fentanyl dose. The Von Frey threshold testing was found to be unsuitable for measurement of pain in this experimental model. When administered as total intravenous anaesthesia, alfaxalone did not provide analgesia in the postoperative period.

Comparison of two intravenous anesthetic infusion regimens for alfaxalone in cats

OBJECTIVE

To compare the performance of an alfaxalone constant rate intravenous (IV) infusion versus a 3-step IV infusion, both following a loading dose, for the maintenance of a target plasma alfaxalone concentration of 7.6 mg L^-1 (effective plasma alfaxalone concentration for immobility in 99% of the population) in cats.

STUDY DESIGN

Prospective randomized crossover study.

ANIMALS

A group of six healthy, adult male neutered cats.

METHODS

Catheters were placed in a jugular vein for blood sampling and in a medial saphenous vein for drug administration. An IV bolus of alfaxalone (2 mg kg^-1) was administered, followed by either 0.2 mg kg^-1 minute^-1 for 240 minutes (single infusion; SI) or 0.4 mg kg^-1 minute^-1 for 10 minutes, then 0.3 mg kg^-1 minute^-1 for 30 minutes, and then 0.2 mg kg^-1 minute^-1 for 200 minutes (3-step infusion; 3-step). Plasma alfaxalone concentration was measured at six time points during the infusions. Measures of performance were calculated for each infusion regimen and compared using the paired Wilcoxon signed-rank test.

RESULTS

Median (range) absolute performance error, divergence, median prediction error and wobble were 15 (8-19)%, -8 (-12 to -6)% hour^-1, -12 (-19 to -7)% and 10 (8-19)%, respectively, in the SI treatment, and 6 (2-16)%, 0 (-13 to 2)% hour^-1, 1 (-16 to 4)% and 4 (3-6)% respectively, in the 3-step treatment and were significantly smaller in the 3-step treatment than in the SI treatment.

CONCLUSION AND CLINICAL RELEVANCE

After IV administration of a bolus dose, a 3-step infusion regimen can better maintain stable plasma alfaxalone concentrations close to the target concentration than a single constant rate infusion.