Treatment of Spontaneous Tumors With Algorithmically Controlled Electroporation.

OBJECTIVE: To study the safety and efficacy of algorithmically controlled electroporation (ACE) against spontaneous equine melanoma. METHODS: A custom temperature sensing coaxial electrode was paired with a high voltage pulse generation system with integrated temperature feedback controls. Computational modeling and ex vivo studies were conducted to evaluate the system's ability to achieve and maintain target temperatures. Twenty-five equine melanoma tumors were treated with a 2000V protocol consisting of a 2-5-2 waveform, 45ºC temperature set point, and integrated energized times of 0.005 s, 0.01 s, or 0.02 s (2500x, 5000x, and 10000x 2 µs pulses, respectively). Patients returned 20-50 days post treatment to determine the efficacy of the treatment. RESULTS: ACE temperature control algorithms successfully achieved and maintained target temperatures in a diverse population of spontaneous tumors with significant variation in tissue impedance. All treatments were completed successfully without and without adverse events. Complete response rates greater than 93% were achieved in all treatment groups. CONCLUSION: ACE is a safe and effective treatment for spontaneous equine melanoma. The temperature control algorithm enabled rapid delivery of electroporation treatments without prior knowledge of tissue electrical or thermal properties and could adjust to real time changes in tissue properties. SIGNIFICANCE: Real time temperature control in electroporation procedures enables treatments near critical structures where thermal damage is contraindicated. Unlike standard approaches, ACE protocols do not require extensive pretreatment planning or knowledge of tissue properties to determine an optimal energy delivery rate and they can account for changes in tissue state (e.g. perfusion) in real time to simultaneously minimize treatment time and potential for thermal damage.

Investigation of integrated time nanosecond pulse irreversible electroporation against spontaneous equine melanoma.

Introduction: Integrated time nanosecond pulse irreversible electroporation (INSPIRE) is a novel tumor ablation modality that employs high voltage, alternating polarity waveforms to induce cell death in a well-defined volume while sparing the underlying tissue. This study aimed to demonstrate the in vivo efficacy of INSPIRE against spontaneous melanoma in standing, awake horses. Methods: A custom applicator and a pulse generation system were utilized in a pilot study to treat horses presenting with spontaneous melanoma. INSPIRE treatments were administered to 32 tumors across 6 horses and an additional 13 tumors were followed to act as untreated controls. Tumors were tracked over a 43-85 day period following a single INSPIRE treatment. Pulse widths of 500ns and 2000ns with voltages between 1000 V and 2000 V were investigated to determine the effect of these variables on treatment outcomes. Results: Treatments administered at the lowest voltage (1000 V) reduced tumor volumes by 11 to 15%. Higher voltage (2000 V) treatments reduced tumor volumes by 84 to 88% and eliminated 33% and 80% of tumors when 500 ns and 2000 ns pulses were administered, respectively. Discussion: Promising results were achieved without the use of chemotherapeutics, the use of general anesthesia, or the need for surgical resection in regions which are challenging to keep sterile. This novel therapeutic approach has the potential to expand the role of pulsed electric fields in veterinary patients, especially when general anesthesia is contraindicated, and warrants future studies to demonstrate the efficacy of INSPIRE as a solid tumor treatment.

Error reporting in a large animal veterinary teaching hospital identifies medication errors occur most often in the prescribing phase of therapy.

OBJECTIVE: To identify the rate at which medication errors occurred over a 2-year period in a large animal veterinary teaching hospital and describe the types of errors that occurred. SAMPLE: 226 medication errors over 6,155 large animal visits occurred during the study period. Multiple errors may have affected the same patient. METHODS: Medication error reports from March 1, 2021, to March 31, 2023, were reviewed retrospectively and classified by species, type of drug, and month and day of the week the error occurred. Errors were categorized according to multiple previously developed systems to allow for comparison to other studies. RESULTS: 226 medication errors occurred over 6,155 patient visits in a 2-year period: 57.5% (130/226) were identified by a dedicated large animal pharmacist, and 64.2% (145/226) of errors were identified and corrected before reaching the patient. Prescription/medication order errors (58.4% [132/226]) occurred significantly more often than errors in medication preparation (21.7% [49/226]; P < .001) and administration (19.6%; P < .001). Antibiotics (48.7% [110/226]) and NSAIDs (17.7% [40/226]) were the drug classes most involved in errors. CLINICAL RELEVANCE: Most medication errors in this study occurred in the ordering/prescribing phase. This is similar to reports in human medicine, where standardized medication error reporting strategies exist. Developing and applying similar strategies in veterinary medicine may improve patient safety and outcome.

Efficacy of a commercial dry sleeve cryotherapy system for cooling the equine metacarpus.

OBJECTIVE: To determine the ability of a commercial cryotherapy system (Game Ready Equine) to cool the metacarpal subcutaneous tissue and the superficial digital flexor tendon (SDFT) in horses. STUDY DESIGN: Experimental study. ANIMALS OR SAMPLE POPULATION: Six healthy adult horses. METHODS: Thermocouples were implanted into the metacarpal subcutaneous tissues and the SDFT of six horses. Two treatments (cryotherapy or cryotherapy with 5-50 mmHg intermittent compression) were randomly assigned to forelimbs and performed for 20 minutes. Temperatures were compared to the target range of 10-19°C and between groups. RESULTS: Only one limb in the cryotherapy/compression group reached the target range after cryotherapy. Temperatures did not differ between treatment groups at time 0. Lowest temperatures achieved in the subcutaneous tissue (p = .0043) and SDFT (p = .005) were 4.9 and 7.6°C lower when intermittent compression was applied. Similarly, applying compression induced a maximum change in temperature of approximately 7.0°C in the subcutaneous tissue (p = .014) and 10.2°C in the SDFT (p = .0001). CONCLUSION: The cryotherapy system did not cool equine subcutaneous tissue or SDFT to the target temperature range, except in one limb. Combining cryotherapy with intermittent compression did result in lower temperatures and a greater change in temperature of the subcutaneous tissue and SDFT. CLINICAL SIGNIFICANCE: When using this cryotherapy system, the addition of intermittent compression should be considered to achieve lower temperatures and potentially greater reduction in inflammation. Further studies are warranted to determine the effect of longer treatment times, higher compression settings, and the optimal temperature for benefits in normal and diseased equine tissues.

Comparison of the Intestinal Pharmacokinetics of Two Different Florfenicol Dosing Regimens and Its Impact on the Prevalence and Phenotypic Resistance of E. coli and Enterococcus over Time.

In order to mitigate the food animal sector's role in the growing threat of antimicrobial resistance (AMR), the World Health Organization (WHO) suggests the use of lower tier antimicrobials, such as florfenicol. Florfenicol has two dosing schemes used to treat primarily bovine respiratory disease. In this study, the objective was to characterize the plasma and gastrointestinal pharmacokinetics of each dosing regimen and assess the effect of these dosing regimens on the prevalence of resistant indicator bacteria over time. Twelve steers underwent abdominal surgery to facilitate the placement of ultrafiltration probes within the lumen of the ileum and colon, as well as placement of an interstitial probe. Following surgery, cattle were dosed with either 20 mg/kg IM every 48 h of florfenicol given twice (n = 6) or a single, subcutaneous dose (40 mg/kg, n = 6). Plasma, interstitial fluid, gastrointestinal ultrafiltrate, and feces were collected. Pharmacokinetic analysis demonstrated high penetration of florfenicol within the gastrointestinal tract for both the high and low dose group (300%, 97%, respectively). There was no significant difference noted between dosing groups in proportion or persistence of phenotypically resistant bacterial isolates; however, the percent of resistant isolates was high throughout the study period. The recommendation for the use of a lower tier antimicrobial, such as florfenicol, may allow for the persistence of co-resistance for antibiotics of high regulatory concern.

Ceftiofur formulation differentially affects the intestinal drug concentration, resistance of fecal Escherichia coli, and the microbiome of steers.

Antimicrobial drug concentrations in the gastrointestinal tract likely drive antimicrobial resistance in enteric bacteria. Our objective was to determine the concentration of ceftiofur and its metabolites in the gastrointestinal tract of steers treated with ceftiofur crystalline-free acid (CCFA) or ceftiofur hydrochloride (CHCL), determine the effect of these drugs on the minimum inhibitory concentration (MIC) of fecal Escherichia coli, and evaluate shifts in the microbiome. Steers were administered either a single dose (6.6 mg/kg) of CCFA or 2.2 mg/kg of CHCL every 24 hours for 3 days. Ceftiofur and its metabolites were measured in the plasma, interstitium, ileum and colon. The concentration and MIC of fecal E. coli and the fecal microbiota composition were assessed after treatment. The maximum concentration of ceftiofur was higher in all sampled locations of steers treated with CHCL. Measurable drug persisted longer in the intestine of CCFA-treated steers. There was a significant decrease in E. coli concentration (P = 0.002) within 24 hours that persisted for 2 weeks after CCFA treatment. In CHCL-treated steers, the mean MIC of ceftiofur in E. coli peaked at 48 hours (mean MIC = 20.45 ug/ml, 95% CI = 10.29-40.63 ug/ml), and in CCFA-treated steers, mean MIC peaked at 96 hours (mean MIC = 10.68 ug/ml, 95% CI = 5.47-20.85 ug/ml). Shifts in the microbiome of steers in both groups were due to reductions in Firmicutes and increases in Bacteroidetes. CCFA leads to prolonged, low intestinal drug concentrations, and is associated with decreased E. coli concentration, an increased MIC of ceftiofur in E. coli at specific time points, and shifts in the fecal microbiota. CHCL led to higher intestinal drug concentrations over a shorter duration. Effects on E. coli concentration and the microbiome were smaller in this group, but the increase in the MIC of ceftiofur in fecal E. coli was similar.

Effects of acellular equine amniotic allografts on the healing of experimentally induced full-thickness distal limb wounds in horses.

OBJECTIVE: To characterize the growth factors contained in equine amniotic membrane allograft (eAM; StemWrap scaffold and StemWrap+ injection) and to evaluate the effect of eAM on equine distal limb wound healing. STUDY DESIGN: Prospective experimental controlled study. SAMPLE POPULATION: Eight adult horses. METHODS: Transforming growth factor (TGF)-ß1, vascular endothelial growth factor (VEGF), epidermal growth factor, platelet-derived growth factor-BB, and prostaglandin E2 (PGE2 ) concentrations in StemWrap+ were assessed with enzyme-linked immunosorbent assay. Two full-thickness 6.25-cm2 skin wounds were created on each metacarpus. On one forelimb, one wound was treated with eAM, and the other was left untreated (eAM control). On the contralateral limb, one wound was treated with a silicone dressing, and the other served as negative control. Three-dimensional images were obtained to determine wound circumference and surface area analyses at each bandage change until healed. Excessive granulation tissue was debrided once weekly for 4 weeks. Biopsy samples were taken to evaluate quality of wound healing via histologic and immunohistochemistry assays. RESULTS: StemWrap+ contained moderate concentrations of TGF-ß1 (494.10 pg/mL), VEGF (212.52 pg/mL), and PGE2 (1811.61 pg/mL). Treatment of wounds with eAM did not affect time to healing or histologic quality of the healing compared with other groups but was associated with increased granulation tissue production early in the study, particularly on day 7. CONCLUSION: Application of eAM resulted in increased granulation tissue production while maintaining appropriate healing of experimental wounds. CLINICAL SIGNIFICANCE: Use of eAM is likely most beneficial for substantial wounds in which expedient production of large amounts of granulation tissue is desirable.

Dosing Regimen of Enrofloxacin Impacts Intestinal Pharmacokinetics and the Fecal Microbiota in Steers.

Objective: The intestinal concentrations of antimicrobial drugs that select for resistance in fecal bacteria of cattle are poorly understood. Our objective was to associate active drug concentrations in the intestine of steers with changes in the resistance profile and composition of the fecal microbiome. Methods: Steers were administered either a single dose (12.5 mg/kg) or 3 multiple doses (5 mg/kg) of enrofloxacin subcutaneously every 24 h. Enrofloxacin and ciprofloxacin concentrations in intestinal fluid were measured over 96 h, and the abundance and MIC of E. coli in culture and the composition of the fecal microbiota by 16S rRNA gene sequencing were assessed over 192 h after initial treatment. Results: Active drug concentrations in the ileum and colon exceeded plasma and interstitial fluid concentrations, but were largely eliminated by 48 h after the last dose. The concentration of E. coli in the feces significantly decreased during peak drug concentrations, but returned to baseline by 96 h in both groups. The median MIC of E. coli isolates increased for 24 h in the single dose group, and for 48 h in the multiple dose group. The median MIC was higher in the multiple dose group when compared to the single dose group starting 12 h after the initial dose. The diversity of the fecal microbiota did not change in either treatment group, and taxa-specific changes were primarily seen in phyla commonly associated with the rumen. Conclusions: Both dosing regimens of enrofloxacin achieve high concentrations in the intestinal lumen, and the rapid elimination mitigates long-term impacts on fecal E. coli resistance and the microbiota.

Recovery of horses from general anesthesia after induction with propofol and ketamine versus midazolam and ketamine.

OBJECTIVE To evaluate quality of recovery from general anesthesia in horses after induction with propofol and ketamine versus midazolam and ketamine. DESIGN Prospective randomized crossover study. ANIMALS 6 healthy adult horses. PROCEDURES Horses were premedicated with xylazine (1.0 mg/kg [0.45 mg/lb], IV), and general anesthesia was induced with midazolam (0.1 mg/kg [0.045 mg/lb], IV) or propofol (0.5 mg/kg [0.23 mg/lb], IV), followed by ketamine (3.0 mg/kg [1.36 mg/lb], IV). Horses were endotracheally intubated, and anesthesia was maintained with isoflurane. After 60 minutes, horses were given romifidine (0.02 mg/kg [0.009 mg/lb], IV) and allowed to recover unassisted. Times to first movement, sternal recumbency, and standing and the number of attempts to stand were recorded. Plasma concentrations of propofol or midazolam were measured following induction and immediately before recovery. Recovery quality was scored by 3 graders with a recovery rubric and a visual analog scale. RESULTS Number of attempts to stand was significantly lower when horses received propofol (median, 2; range, 1 to 3) than when they received midazolam (median, 7.5; range, 3 to 16). For both the recovery rubric and visual analog scale, recovery quality was significantly better when horses received propofol than when they received midazolam. Plasma drug concentration at recovery, as a percentage of the concentration at induction, was significantly lower when horses received propofol than when they received midazolam. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that for horses undergoing short (ie, 60 minutes) periods of general anesthesia, recovery quality may be better following induction with propofol and ketamine, compared with midazolam and ketamine.

Evaluation of epiduroscopy for detection of vertebral canal and spinal cord lesions in dogs.

OBJECTIVE To evaluate the potential usefulness of epiduroscopy for clinical diagnosis and treatment of vertebral canal and spinal cord lesions in dogs. SAMPLE Cadavers of 6 mixed-breed dogs. PROCEDURES Dogs were positioned in sternal recumbency, and an endoscope was introduced into the lumbosacral epidural space. A fiberscope (diameter, 0.9 mm; length, 30 cm) was used for 3 dogs, and a videoscope (diameter, 2.8 mm; length, 70 cm) was used for the other 3 dogs. Visibility and identities of anatomic structures were recorded, and maneuverability of the endoscopes was assessed. Extent of macroscopic tissue damage was evaluated by manual dissection of the vertebral canal at the end of the procedure. RESULTS Intermittent saline (0.9% NaCl) solution infusion, CO2 insufflation, and endoscope navigation improved visualization by separating the epidural fat from the anatomic structures of interest. Images obtained with the fiberscope were small and of poor quality, making identification of specific structures difficult. Maneuverability of the fiberscope was difficult, and target structures could not be reliably reached or identified. Maneuverability and image quality of the videoscope were superior, and spinal nerve roots, spinal dura mater, epidural fat, and blood vessels could be identified. Subsequent manual dissection of the vertebral canal revealed no gross damage in the spinal cord, nerve roots, or blood vessels. CONCLUSIONS AND CLINICAL RELEVANCE A 2.8-mm videoscope was successfully used to perform epiduroscopy through the lumbosacral space in canine cadavers. Additional refinement and evaluation of the technique in live dogs is necessary before its use can be recommended for clinical situations.

Implantation of an ultrafiltration device in the ileum and spiral colon of steers to continuously collect intestinal fluid.

Collection of fluid from the lumen of the gastrointestinal tract is commonly necessary for research projects, but presents challenges including intestinal motility and potential for leakage of intestinal contents. In this study, ultrafiltration collection devices were surgically implanted in the ileum and spiral colon of 12 steers for repeated collection of intestinal fluid over 48 hours. There were no significant complications associated with surgery or during the post-operative period, nor were there any significant pathologic changes found at necropsy 3 or 4 days post-surgery. Over 48 hours, we obtained 88% of the desired 212 samples. Only two devices failed to routinely collect samples. Use of ultrafiltration probes is a novel, consistent and humane method to repeatedly sample the gastrointestinal contents.

Standing equine surgery of the upper respiratory tract.

The purpose of this article is to review the literature and personal experiences of equine surgeons so as to describe procedures that can be performed in the standing sedated horse to alleviate conditions that result in upper respiratory tract obstruction. Upper respiratory tract surgery requires attention to detail, meticulous planning, and careful dissection and execution with little room for error. This article describes a selection of standing upper airway procedures, the indications for and possible complications of these surgeries, and advantages and disadvantages of a particular method.

Resection and anastomosis of the descending colon in 43 horses.

OBJECTIVES: To determine (1) the short- (to hospital discharge) and long- (>6 months) term survival, (2) factors associated with short-term survival, and (3) the perioperative course for horses with resection and anastomosis of the descending colon. STUDY DESIGN: Multicentered case series. ANIMALS: Horses (n=43) that had descending colon resection and anastomosis. METHODS: Medical records (January 1995-June 2009) of 7 equine referral hospitals were reviewed for horses that had descending colon resection and anastomosis and were recovered from anesthesia. Retrieved data included history, results of clinical and clinicopathologic examinations, surgical findings, postsurgical treatment and complications, and short-term survival (hospital discharge). Long-term survival was defined as survival > or =6 months after hospital discharge. RESULTS: Of 43 horses, 36 (84%) were discharged from the hospital. Twenty-eight of 30 horses with follow-up information survived > or =6 months. No significant associations between perioperative factors and short-term survival were identified. Lesions included strangulating lipoma (n=27), postfoaling trauma (4), infarction (4), intraluminal obstruction (2), and other (6). Common postoperative complications included fever and diarrhea. During hospitalization 7 horses were euthanatized or died because of septic peritonitis (3), endotoxemia (3), and colic and ileus (1). CONCLUSIONS: Descending colon resection and anastomosis has a favorable prognosis for hospital discharge and survival > or =6 months. The most common cause of small colon incarceration was strangulating lipoma. CLINICAL RELEVANCE: Complications include postoperative fever and diarrhea but the prognosis is good after small colon resection and anastomosis.