Effect of fentanyl on the induction dose and minimum infusion rate of alfaxalone preventing movement in dogs

Sugammadex for reversal of rocuronium-induced neuromuscular blockade during alfaxalone anesthesia in dogs

OBJECTIVE

To investigate the reversal effect of sugammadex on neuromuscular blockade induced by a single bolus of rocuronium in dogs under alfaxalone anesthesia.

STUDY DESIGN

Randomized, prospective, crossover experimental study.

ANIMALS

A group of six adult Beagle dogs (three females and three males), weighing 11.3-15.8 kg and aged 6-8 years, were used.

METHODS

Dogs were anesthetized twice with a 1.25 times minimum infusion rate of alfaxalone, with a washout period of at least 14 days between experiments. Neuromuscular function was monitored using acceleromyography with train-of-four (TOF) stimulation of the peroneal nerve. After recording the control TOF ratio (TOFRC), rocuronium (0.5 mg kg-1) was administered intravenously. Subsequently, sugammadex (4 mg kg-1) or an equal volume of saline (control treatment) was administered intravenously when the TOF count returned from 0 to 1 after neuromuscular blockade. Time from rocuronium injection to TOF count = 0 (onset time), time from TOF count = 0 to TOF count = 1 (maximum blockade period), time of first twitch amplitude recovery from 0.25 to 0.75 (recovery index), and time from sugammadex or saline administration to TOF ratio/TOFRC ≥ 0.9 (recovery time) were recorded.

RESULTS

The onset time and maximum blockade duration did not differ between sugammadex treatment [1.2 (0.7-1.5) minutes and 9.9 (6.3-10.5) minutes, respectively] and control treatment [median (range); 1.0 (0.7-1.1) minutes and 9.9 (8.8-11.5) minutes, respectively] (p = 0.219 and 0.844, respectively). Recovery index was 0.5 (0.3-0.7) minutes in sugammadex treatment, which was shorter than that in control treatment [4.5 (3.7-4.9) minutes] (p = 0.031). Recovery time was 0.8 (0.5-2.8) minutes in sugammadex treatment, which was shorter than that in control treatment [10.5 (6.8-14.3) minutes] (p = 0.031).

CONCLUSIONS AND CLINICAL RELEVANCE

Rocuronium-induced neuromuscular blockade was effectively reversed by sugammadex in dogs anesthetized with alfaxalone.

Pharmacokinetics and pharmacodynamics of intramuscular alfaxalone in central bearded dragons (Pogona vitticeps): Effect of injection site

OBJECTIVE

To evaluate the pharmacodynamic effects and pharmacokinetics of a single intramuscular (IM) injection of alfaxalone in central bearded dragons (Pogona vitticeps) when injected at a cranial versus a caudal site.

STUDY DESIGN

Prospective, masked, randomized crossover study.

ANIMALS

A total of 13 healthy bearded dragons weighing 0.48 ± 0.1 kg.

METHODS

Alfaxalone (10 mg kg^-1) was administered IM to 13 bearded dragons in the triceps muscle (cranial treatment) or the quadriceps muscle (caudal treatment) separated by 4 weeks. Pharmacodynamic variables included movement score, muscle tone score and righting reflex. Blood was obtained from the caudal tail vein using a sparse sampling methodology. Plasma alfaxalone concentrations were determined using liquid chromatography-mass spectrometry, and pharmacokinetic analysis was performed using nonlinear mixed-effects modeling. Differences in variables between injection sites were analyzed using a nonparametric Wilcoxon signed-rank test for paired data with significance set at p ≤ 0.05.

RESULTS

Time to loss of righting reflex score was not different, median (interquartile range), between cranial and caudal treatments [8 (5-11) and 8 (4-12) minutes, respectively, p = 0.72]. Time to recovery of righting reflex was also not different between cranial and caudal treatments [80 (44-112) and 64 (56-104) minutes, respectively, p = 0.75]. Plasma alfaxalone concentrations were not significantly different between treatments. The population estimate (95% confidence intervals) for volume of distribution per fraction absorbed was 1.0 (0.79-1.20) L kg^-1, clearance per fraction absorbed was 9.6 (7.6-11.6) mL minute^-1 kg^-1, absorption rate constant was 2.3 (1.9-2.8) minute^-1 and elimination half-life was 71.9 (52.7-91.1) minutes.

CONCLUSIONS AND CLINICAL RELEVANCE

Regardless of the injection site, IM alfaxalone (10 mg kg^-1) produced reliable chemical restraint in central bearded dragons, appropriate for nonpainful diagnostic procedures or anesthetic premedication.

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.

Comparison between intravenous lidocaine and fentanyl on cough reflex and sympathetic response during endotracheal intubation in dogs

OBJECTIVE

To compare the effects of intravenous (IV) lidocaine and fentanyl on the cough reflex and autonomic response during endotracheal intubation in dogs.

STUDY DESIGN

Randomized, blinded, superiority clinical trial.

ANIMALS

A total of 46 client-owned dogs undergoing magnetic resonance imaging.

METHODS

After intramuscular methadone (0.2 mg kg^-1), dogs were randomized to be administered either IV lidocaine (2 mg kg^-1; group L) or fentanyl (7 μg kg^-1; group F). After 5 minutes, alfaxalone was administered until endotracheal intubation was possible (1 mg kg^-1 IV over 40 seconds followed by 0.4 mg kg^-1 increments to effect). Total dose of alfaxalone was recorded and cough reflex at endotracheal intubation was scored. Heart rate (HR) was continuously recorded, Doppler systolic arterial blood pressure (SAP) was measured every 20 seconds. Vasovagal tonus index (VVTI) and changes (Δ) in HR, SAP and VVTI between pre-intubation and intubation were calculated. Groups were compared using univariate and multivariate analysis. Statistical significance was set as p < 0.05.

RESULTS

Group F included 22 dogs and group L 24 dogs. The mean (± standard deviation) alfaxalone dose was 1.1 (± 0.2) and 1.35 (± 0.3) mg kg^-1 in groups F and L, respectively (p = 0.0008). At intubation, cough was more likely in group L (odds ratio = 11.3; 95% confidence intervals, 2.1 - 94.2; p = 0.01) and HR increased in 87.5% and 54.5% of groups L and F, respectively (p = 0.02). The median (range) ΔHR between pre-intubation and intubation was higher (13.1%; - 4.3 to + 55.1) in group L (p = 0.0021). Between groups, SAP and VVTI were similar.

CONCLUSION AND CLINICAL RELEVANCE

At the stated doses, whilst reducing the alfaxalone dose, fentanyl is superior to lidocaine in suppressing the cough reflex and blunting the increase in HR at endotracheal intubation in dogs premedicated with methadone.

Effects of ketamine or midazolam continuous rate infusions on alfaxalone total intravenous anaesthesia requirements and recovery quality in healthy dogs: a randomized clinical trial

OBJECTIVE

To determine the alfaxalone dose reduction during total intravenous anaesthesia (TIVA) when combined with ketamine or midazolam constant rate infusions and to assess recovery quality in healthy dogs.

STUDY DESIGN

Prospective, blinded clinical study.

ANIMALS

A group of 33 healthy, client-owned dogs subjected to dental procedures.

METHODS

After premedication with intramuscular acepromazine 0.05 mg kg^-1 and methadone 0.3 mg kg^-1, anaesthetic induction started with intravenous alfaxalone 0.5 mg kg^-1 followed by either lactated Ringer's solution (0.04 mL kg^-1, group A), ketamine (2 mg kg^-1, group AK) or midazolam (0.2 mg kg^-1, group AM) and completed with alfaxalone until endotracheal intubation was achieved. Anaesthesia was maintained with alfaxalone (6 mg kg^-1 hour^-1), adjusted (±20%) every 5 minutes to maintain a suitable level of anaesthesia. Ketamine (0.6 mg kg^-1 hour^-1) or midazolam (0.4 mg kg^-1 hour^-1) were employed for anaesthetic maintenance in groups AK and AM, respectively. Physiological variables were monitored during anaesthesia. Times from alfaxalone discontinuation to extubation, sternal recumbency and standing position were calculated. Recovery quality and incidence of adverse events were recorded. Groups were compared using parametric analysis of variance and nonparametric (Kruskal-Wallis, Chi-square, Fisher's exact) tests as appropriate, p < 0.05.

RESULTS

Midazolam significantly reduced alfaxalone induction and maintenance doses (46%; p = 0.034 and 32%, p = 0.012, respectively), whereas ketamine only reduced the alfaxalone induction dose (30%; p = 0.010). Recovery quality was unacceptable in nine dogs in group A, three dogs in group AK and three dogs in group AM.

CONCLUSIONS AND CLINICAL RELEVANCE

Midazolam, but not ketamine, reduced the alfaxalone infusion rate, and both co-adjuvant drugs reduced the alfaxalone induction dose. Alfaxalone TIVA allowed anaesthetic maintenance for dental procedures in dogs, but the quality of anaesthetic recovery remained unacceptable irrespective of its combination with ketamine or midazolam.

Pharmacokinetics and pharmacodynamics of alfaxalone after a single intramuscular or intravascular injection in mallard ducks (Anas platyrhynchos)

Pharmacokinetics and pharmacodynamics of alfaxalone was performed in mallard ducks (Anas platyrhynchos) after single bolus injections of 10 mg/kg administered intramuscularly (IM; n = 10) or intravenously (IV; n = 10), in a randomized cross-over design with a washout period between doses. Mean (±SD) C_max following IM injection was 1.6 (±0.8) µg/ml with T_max at 15.0 (±10.5) min. Area under the curve (AUC) was 84.66 and 104.58 min*mg/ml following IV and IM administration, respectively. Volume of distribution (V_D ) after IV dose was 3.0 L/kg. The mean plasma clearance after 10 mg/kg IV was 139.5 (±67.9) ml min^-1  kg^-1 . Elimination half-lives (mean [±SD]) were 15.0 and 16.1 (±3.0) min following IV and IM administration, respectively. Mean bioavailability at 10 mg/kg IM was 108.6%. None of the ducks achieved a sufficient anesthetic depth for invasive procedures, such as surgery, to be performed. Heart and respiratory rates measured after administration remained stable, but many ducks were hyperexcitable during recovery. Based on sedation levels and duration, alfaxalone administered at dosages of 10 mg/kg IV or IM in mallard ducks does not induce clinically acceptable anesthesia.