Effects of intravenous administration of ascorbic acid (vitamin C) on oxidative status in healthy adult horses.

BACKGROUND: Ascorbic acid (AA) is an antioxidant that might be beneficial for adjunctive treatment of sepsis in horses. The optimal dose and effects on oxidative status are unknown. HYPOTHESIS: Ascorbic acid administration will increase plasma AA concentrations and decrease determinants of reactive oxygen metabolites (dROM), basal and stimulant-induced intraerythrocytic reactive oxygen species (ROS) concentrations, and stimulant-induced neutrophil ROS production, and increase plasma antioxidant capacity (PAC) in a dose-dependent manner. ANIMALS: Eight healthy horses. METHODS: Randomized placebo-controlled crossover study. Each horse received 4 single-dose IV treatments including AA at 25, 50, and 100 mg/kg and saline (placebo) with each treatment separated by ≥1 week. Blood was collected at baseline, 2 and 6 hours for assessment of plasma dROM and PAC via photometer, intraerythrocytic ROS by flow cytometry, and stimulant-induced neutrophil ROS by a fluorometric assay. Plasma AA concentrations were measured by high-performance liquid chromatography/electrochemical detection. RESULTS: Ascorbic acid at 100 mg/kg resulted in decreased dROM 2 hours after treatment (P = .03, 95% CI 5.51-121.2, point estimate 63.3). There was no effect of AA on basal or stimulant-induced intraerythrocytic ROS (P = .88, 95% CI -0.156 to 0.081, point estimate -0.037; P = .93, 95% CI -0.123 to 0.112, point estimate -0.006, respectively), basal or stimulant-induced neutrophil ROS (P ≥ .12, 95% CI -644.9 to 56.2, point estimate -294.4), or PAC (P ≥ .64, 95% CI -1567 to 463.4, point estimate -552.0) at any dose or timepoint. Plasma AA concentrations increased in a dose-dependent manner. CONCLUSIONS AND CLINICAL IMPORTANCE: High-dose administration of AA might provide antioxidant benefits in horses.

Evaluation of frontal and infratrochlear nerve blocks for standing sedated frontonasal sinusotomy in horses.

OBJECTIVE: To determine if targeted blocking of frontal and infratrochlear nerves provided anesthesia for the approach to a frontonasal sinusotomy. STUDY DESIGN: Two part study: Part 1 randomized crossover design; Part 2 proof of concept. ANIMALS: N = 12; six each in Parts 1 and 2. METHODS: Part 1: Each horse had either frontal and infratrochlear nerve blocks or a line block performed with 2% mepivacaine hydrochloride. Mechanical nociceptive thresholds (MNT) were obtained at five sites along a proposed frontonasal sinusotomy prior to injection, and at 10, 60, and 120 min after blocking. After a 4 day washout period, the opposite procedure was performed. Order of procedure and side of face were randomized. MNTs were analyzed using mixed-model ANOVA with p < .05. Part 2: Frontal and infratrochlear nerve blocks were performed followed by creation of a skin/periosteal incision, which was closed at 2 h. Ability to create and suture the incision, and the size of the incision were recorded. RESULTS: For part 1, both line and targeted blocks resulted in at least two times an increase in median MNT values at each of the five sites, as compared to baseline MNT values (p < .0025). In Part 2, incisions could be completed in five of six horses, with median incision size of 6.5 × 5 cm. CONCLUSION: Following frontal and infratrochlear nerve blocks, MNTs were increased along a proposed frontonasal sinusotomy, and skin incisions could be created in the majority of horses. CLINICAL SIGNIFICANCE: Frontal and infratrochlear nerve blocks provide an alternative technique to create a frontonasal sinusotomy.