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.

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.

Biomechanical properties of celiotomy wounds closed with tape and cyanoacrylate versus intradermal sutures.

OBJECTIVE: To compare cutaneous wound closure with mesh and 2-octyl cyanoacrylate (MOC) vs an intradermal suture pattern (ISP) in terms of time of application and biomechanical properties. SAMPLE POPULATION: Experimental study with 12 female beagle dogs. METHODS: A skin incision was created from the xiphoid to the pubis as part of an ovariohysterectomy; the linea alba and subcutaneous tissue were closed routinely. Half of the skin incision was closed with MOC, and the other half was closed with an ISP. Tissue samples were collected from both sections at days 14 and 28 and tested for ultimate strength and stiffness. RESULTS: Closure with MOC (72.8 ± 14.0 s) was faster than with an ISP (398.4 ± 36.4 s; P = .001). The ultimate load and stiffness increased with time for MOC (P = .005 and P = .005, respectively) and ISP (P < .001 and P < .001, respectively). On day 14, ultimate load and stiffness were greater in wounds closed with MOC compared with ISP (P = .014 and P = .02, respectively). No difference between groups was detected at day 28. CONCLUSION: Cutaneous wound closure with MOC was faster and resulted in superior strength at 14 days compared with closure with an ISP in this healthy population. CLINICAL SIGNIFICANCE: Mesh and 2-octyl cyanoacrylate offers an attractive alternative to ISP for skin closure after celiotomy in dogs, especially if surgical/anesthesia time is a concern.

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

OBJECTIVE: To compare cardiovascular effects and anaesthetic quality of alfaxalone alone or in combination with a fentanyl constant rate infusion (CRI) when used for total intravenous anaesthesia (TIVA) in dogs. STUDY DESIGN: Prospective, blinded, randomized, experimental study. ANIMALS: A group of 12 intact female dogs. METHODS: Following intramuscular dexmedetomidine (10 µg kg-1) and methadone (0.1 mg kg-1) administration, anaesthesia was induced intravenously with alfaxalone (2 mg kg-1) (group AP) or alfaxalone (2 mg kg-1) preceded by fentanyl (2 µg kg-1) (group AF). Anaesthetic maintenance was obtained with an alfaxalone variable rate infusion (VRI) started at 0.15 mg kg-1 minute-1 (group AP) or an alfaxalone VRI (same starting rate) combined with a CRI of fentanyl (10 µg kg-1 hour-1) (group AF). The alfaxalone VRI was adjusted every 5 minutes, based on clinical assessment. Cardiovascular parameters (recorded every 5 minutes) and recovery characteristics (using a numerical rating scale) were compared between groups. A mixed model statistical approach was used to compare the mean VRI alfaxalone dose and cardiovascular parameters between groups; recovery scores were analysed using the Wilcoxon rank-sum test (α = 0.05). RESULTS: The mean CRI alfaxalone dose for anaesthetic maintenance differed significantly between treatments [0.16 ± 0.01 mg kg-1 minute-1 (group AP) versus 0.13 ± 0.01 mg kg-1 minute-1 (group AF)]. Overall heart rate, systolic, mean and diastolic arterial pressures were lower in group AF than in group AP (p < 0.0001, p = 0.0058, p < 0.0001 and p < 0.0001, respectively. Recovery quality scores did not differ significantly and were poor in both groups. CONCLUSIONS AND CLINICAL RELEVANCE: In combination with a fentanyl CRI, an alfaxalone TIVA provides a cardiovascular stable anaesthesia in dogs. The addition of fentanyl results in a significant dose reduction. The quality of anaesthetic recovery remains poor.