Cardiovascular effects, induction and recovery characteristics and alfaxalone dose assessment in alfaxalone versus alfaxalone-fentanyl total intravenous anaesthesia in dogs

Comparison of Propofol and Alfaxalone as Anesthesic Drugs in Bitches Undergoing Ovariohysterectomies (Healthy Bitches and with Pyometra) and Cesarean Sections

This study evaluated the efficacy and safety of two anesthetic agents, alfaxalone and propofol, on maternal physiological parameters (heart and respiratory rates, blood pressure, and temperature) on either ovariohysterectomies or cesarean sections in bitches. A total of 34 healthy and pyometra-affected females (classified as ASA II), were induced with IV propofol (4 mg/kg), while 35 females, both healthy and pyometra affected, were induced with IV alfaxalone (1 mg/kg). For cesarean sections, females (ASA II) were induced with propofol (n = 14) or alfaxalone (n = 14). Additionally, the neonatal viability and modified Apgar score were recorded at 5, 60, and 120 min post-delivery. There were no significant differences in the physiological parameters when comparing the use of propofol and alfaxalone in bitches undergoing ovariohysterectomies, regardless of their health status, nor when comparing cesarean sections. It was observed that bitches induced with propofol occasionally required an additional dose for maintenance of the anesthesia. Neonatal mortality rates were similar for both groups; however, alfaxalone was associated with higher neonatal viability as indicated by the Apgar scores. The findings suggest that both anesthetic protocols are effective and safe for use in canine reproductive surgeries, with no major differences in basic physiological parameters' alteration or neonatal outcomes between the two agents.

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.

Scoping review of quality of anesthetic induction and recovery scales used for dogs

OBJECTIVE

To compare, describe and assess the level of validation of all instruments measuring quality of induction and recovery from anesthesia in dogs.

DATABASES USED

A search was performed using the electronic database PubMed to find articles containing an induction quality scale, a recovery quality scale or both in dogs. Articles not directly accessible through PubMed were obtained through the Auburn University Library website and Google Scholar. The phrases 'induction scoring systems dogs', 'recovery scoring systems dogs', 'anesthetic induction score dogs', and 'anesthetic recovery score dogs' were used for searches using the 'best match search' function. The time frame searched was from 1980 to May 2020. The search was conducted from March 2020 to May 2020.

CONCLUSIONS

A thoroughly tested and validated scale for measuring the quality of induction and recovery does not exist in the current veterinary literature. A large disagreement exists between studies on the use of induction and recovery scales, and many have reported inconsistent results with current instruments. It is recommended that an induction and recovery scale intended for wide-scale use be constructed and tested extensively for psychometric validation and reliability.

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.

Hemodynamic effects of subclinical, clinical and supraclinical plasma alfaxalone concentrations in cats

OBJECTIVE

To characterize the hemodynamic effects of subclinical, clinical and supraclinical plasma alfaxalone concentrations in cats.

STUDY DESIGN

Experimental study.

ANIMALS

A group of six adult healthy male neutered cats.

METHODS

Cats were anesthetized with desflurane in oxygen for instrumentation. Catheters were placed in a medial saphenous vein for drug administration and in a carotid artery for arterial blood pressure measurement and blood collection. A thermodilution catheter was placed in the pulmonary artery via an introducer placed in a jugular vein for measurement of central venous pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, cardiac output and core body temperature, and for sampling mixed venous blood. A lead II electrocardiogram was connected. Desflurane administration was discontinued and a target-controlled infusion system was used to administer alfaxalone to reach six plasma alfaxalone concentrations ranging from 1.0 to 30.4 mg L^-1, with 7.6 mg L^-1 considered a clinical concentration for anesthesia. Cardiovascular measurements were recorded, and arterial and mixed-venous blood samples were collected for blood-gas analysis and plasma alfaxalone concentration measurement at each target concentration. Data were analyzed using a repeated-measures analysis of variance and Dunnett's test for comparisons to the lowest target concentration. Significance was set at p < 0.05.

RESULTS

Mean ± standard deviation plasma alfaxalone concentrations were 0.73 ± 0.32, 1.42 ± 0.41, 3.44 ± 0.40, 6.56 ± 0.43, 18.88 ± 6.81 and 49.47 ± 5.50 mg L^-1 for the 1, 1.9, 3.8, 7.6, 15.2, and 30.4 mg L^-1 target concentrations, respectively. PaCO₂ increased with increasing target plasma alfaxalone concentrations and was 69.4 ± 14.2 mmHg (9.3 ± 1.9 kPa) at the 30.4 mg L^-1 target. Some cardiovascular variables were statistically significantly affected by increasing target plasma alfaxalone concentrations.

CONCLUSION AND CLINICAL RELEVANCE

Within the plasma concentration range studied, alfaxalone caused hypoventilation, but the cardiovascular effects were of small clinical significance.

Effect of premedication on dose requirement, cardiovascular effects and recovery quality of alfaxalone total intravenous anaesthesia in dogs

OBJECTIVE

To investigate alfaxalone total intravenous anaesthesia (TIVA) following premedication with methadone combined with acepromazine (ACP) or dexmedetomidine in bitches undergoing ovariohysterectomy.

STUDY DESIGN

Prospective, blinded, randomized, experimental study.

ANIMALS

A group of 12 female Beagles.

METHODS

Dogs were premedicated intravenously with methadone (0.2 mg kg^-1) combined with ACP (20 μg kg^-1, group AM) or dexmedetomidine (5 μg kg^-1, group DM). Anaesthesia was induced with alfaxalone (2 mg kg^-1). Anaesthetic maintenance was obtained with an alfaxalone variable rate infusion (VRI) started at 0.15 mg kg^-1 minute^-1 and adjusted every 5 minutes based on clinical assessment. Mechanical ventilation was initiated when necessary to maintain normocapnia. Anaesthetic monitoring included electrocardiogram, heart rate (HR), invasive diastolic (DAP), systolic (SAP) and mean arterial blood pressure, arterial haemoglobin oxygen saturation, respiratory variables and oesophageal temperature. Data were recorded every 5 minutes. A mixed model statistical approach was used to compare cardiovascular variables within and between groups (α = 0.05). A Wilcoxon rank-sum test was used to compare body temperature, VRI alfaxalone rate, administered rescue analgesia, sedation, induction, intubation, recovery scores and recovery times between treatments.

RESULTS

Overall HR, SAP and DAP differed between groups (p = 0.001, 0.016, 0.019, respectively). The mean VRI dose rate of alfaxalone differed between groups DM [0.13 (0.11-0.14) mg kg^-1 minute^-1] and AM [0.18 (0.13-0.19) mg kg^-1 minute^-1; p = 0.030]. Rescue analgesia was administered more in group AM (p = 0.019). No significant difference in recovery times and scores was observed between protocols.

CONCLUSIONS AND CLINICAL RELEVANCE

Alfaxalone TIVA following dexmedetomidine/methadone premedication produced a more stable plane of anaesthesia to perform ovariohysterectomy than ACP/methadone. A dose reduction of alfaxalone of 27.7% was obtained in group DM compared with group AM. Recovery quality and recovery times were comparable between both groups.

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.