Objective To compare both vasopressor and intraoperative rescue fentanyl administration after thoracolumbar (TL) and lumbosacral (LS) epidural (extradural) anaesthesia in dogs undergoing cranial abdominal surgery. Study design Retrospective cohort, single-centre, observational study. Animals Eighty-nine client-owned dogs undergoing cranial abdominal surgery. Methods Medical records of dogs undergoing TL or LS epidural anaesthesia for cranial abdominal surgery between 2014 and 2021 were retrieved. Selected demographic variables, mean arterial blood pressure, anaesthetic and epidural drugs and their dosage, volume and injection site, vasopressor and intraoperative rescue fentanyl administration were compared between groups. Intraoperative haemodynamic stability was assessed using generalised average real variability (GenARV). Univariate analysis was used to compare groups. Results Forty-three dogs were enrolled in the TL group and 46 in the LS group. Vasopressors were required more frequently [p = 0.030; odds ratio 2.67 (1.09–6.53)] in the LS group, but GenARV was not different (p = 0.706; 1.51 ± 0.60 and 1.46 ± 0.68 mmHg minute−1 in the LS and TL groups, respectively]. The number of dogs requiring intraoperative rescue fentanyl did not differ between groups (p = 0.992); however, the median (range) amount of fentanyl per hour of surgery was lower in the TL group [1.31 (0.75–7) and 2.87 (0.75–14) μg kg−1 hour−1 in the TL and LS groups, respectively; p = 0.019]. The volume of epidural injectate was lower in group TL (p < 0.001). Conclusions and clinical relevance In dogs undergoing cranial abdominal surgery, TL epidural anaesthesia was associated with reduced vasopressor use compared to LS epidural anaesthesia, while providing comparable intraoperative analgesia with a reduced volume of injectate. Thoracolumbar epidural anaesthesia may result in a more targeted neuraxial blockade with fewer cardiovascular adverse effects, supporting its use for cranial abdominal surgeries.
Objective To investigate whether a clinically relevant solution of dantrolene sodium (DS) (defined as ≥1 mg mL−1) could be produced using available, safe-to-use solvents for emergency preparation and parenteral administration in veterinary species. Study design Laboratory study. Methods DS used in the investigation was from both commercially available oral capsules (DS-cap) and chemical-grade DS (99.9% pure). The DS was dissolved in various solvents using a 25-minute abbreviated shake-flask method and sonication. Ultraviolet absorbance at 387 nm was recorded and concentrations were extrapolated from a dimethylformamide calibration curve. Solvents were titrated to pH 9.5–10 using aliquots of 0.4% sodium hydroxide to assess the influence of pH on DS solubility. Descriptive statistical analyses were performed on resultant data. Results Initial solvent screening identified that 0.9% sodium chloride, 7.2% hypertonic saline, lactated Ringer’s solution, and 50% polyethylene glycol 400 failed to reach predefined target concentrations. Other solvents, including 5% dextrose (D5W) and 20% ethanol (EtOH), failed to reach concentrations ≥ 1 mg mL−1, but stability was maintained over 24 hours. Titrating the solvent pH to 9.5–10 enhanced DS solubility and stability in all tested solvents. Titrated solutions containing 20% N-methyl-2-pyrrolidone and 50% polyethylene glycol 300, with 20% EtOH and D5W as cosolvents, produced DS concentrations of at least 5 mg mL−1 for both DS-cap and chemically pure (99.9%) DS. Conclusions and clinical relevance Multiple solvents and solvent systems investigated demonstrated possibilities for a clinically relevant formulation of DS. DS may be suitable for compounding for off-label use if a patient is known to be malignant hyperthermia (MH) positive or following early MH detection. The safety profile, pharmacokinetic and pharmacodynamic data are still needed.
