A comparison of cardiopulmonary effects and anaesthetic requirements of two dexmedetomidine continuous rate infusions in alfaxalone-anaesthetized Greyhounds

Sedation Quality and Cardiorespiratory, Echocardiographic, Radiographic and Electrocardiographic Effects of Intramuscular Alfaxalone and Butorphanol in Spanish Greyhound Dogs

The quality of sedation and changes in cardiorespiratory variables after the intramuscular administration of alfaxalone and butorphanol in Spanish greyhound dogs were evaluated. Twenty-one adult dogs were included. The dogs received alfaxalone (2 mg/kg) and butorphanol (0.2 mg/kg) intramuscularly. Sedation scoring, cardiorespiratory parameters (including blood gas analysis), echocardiography, thoracic radiography and electrocardiography were performed before sedation and 30 min after drug administration. Moderate sedation was observed, and side effects, such as tremors, nystagmus and auditory hyperesthesia, were noticed. Statistically significant changes in heart rate, invasive blood pressure, pH, arterial saturation of O2 and partial pressure of O2 and CO2 were found. Echocardiographic variables, including end-diastolic volume, left ventricular diameter in diastole, aortic and pulmonic flow, diastolic transmitral flow and left atrial/aortic ratio, and electrocardiography parameters, including PQ interval and QT interval, showed statistically significant changes. In conclusion, the intramuscular administration of alfaxalone and butorphanol to healthy dogs produced moderate sedation with mild cardiorespiratory, echocardiographic and electrocardiographic changes, without alterations in cardiac size on radiographic images.

ED50 and ED95 of rocuronium during alfaxalone anesthesia in dogs

OBJECTIVE

To determine the median effective dose (ED₅₀) and effective dose required to depress the twitch value by 95% (ED₉₅) of rocuronium during alfaxalone anesthesia in dogs.

STUDY DESIGN

A randomized, prospective, crossover experimental study.

ANIMALS

A total of eight adult Beagle dogs (four female, four male), weighing 10.3-14.6 kg and aged 6-8 years.

METHODS

The dogs were anesthetized three times with 1.25-fold the individual minimum infusion rate of alfaxalone 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) and first twitch of TOF (T1C), a single bolus dose of rocuronium 100, 175 or 250 μg kg^-1 (treatments R100, R175 or R250) was administered intravenously. The maximum suppression of the first twitch of TOF (T1) was recorded and calibrated with T1C to construct the dose-response curve, from which ED₅₀ and ED₉₅ were calculated. Time from rocuronium administration to TOF ratio/TOFRC > 0.9 (duration TOFR0.9) was recorded.

RESULTS

ED₅₀ and ED₉₅ of rocuronium during alfaxalone anesthesia were 175 and 232 μg kg^-1, respectively. The median (range) duration TOFR0.9 was longer in treatment R250 [10.1 (9.2-10.9) minutes] than in treatments R100 [3.1 (2.9-4.4) minutes; p < 0.0001] and R175 [7.7 (6.9-8.1) minutes; p < 0.0001]; and longer in treatment R175 than in treatment R100 (p < 0.0001).

CONCLUSIONS AND CLINICAL RELEVANCE

The duration of TOFR0.9 correlated positively with the dosage of rocuronium, indicating that recovery time of rocuronium was also dose-dependent in dogs anesthetized with alfaxalone. The duration TOFR0.9 of rocuronium 250 μg kg^-1 was 10 minutes during alfaxalone anesthesia in dogs.

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.

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.

A preclinical large-animal model for the assessment of critical-size load-bearing bone defect reconstruction

Critical-size bone defects, which require large-volume tissue reconstruction, remain a clinical challenge. Bone engineering has the potential to provide new treatment concepts, yet clinical translation requires anatomically and physiologically relevant preclinical models. The ovine critical-size long-bone defect model has been validated in numerous studies as a preclinical tool for evaluating both conventional and novel bone-engineering concepts. With sufficient training and experience in large-animal studies, it is a technically feasible procedure with a high level of reproducibility when appropriate preoperative and postoperative management protocols are followed. The model can be established by following a procedure that includes the following stages: (i) preoperative planning and preparation, (ii) the surgical approach, (iii) postoperative management, and (iv) postmortem analysis. Using this model, full results for peer-reviewed publication can be attained within 2 years. In this protocol, we comprehensively describe how to establish proficiency using the preclinical model for the evaluation of a range of bone defect reconstruction options.

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.