Comparison of the effect of oxygen supplementation using flow-by or a face mask on the partial pressure of arterial oxygen in sedated dogs.

AIMS To compare the effect of oxygen supplementation using flow-by or a face mask on the partial pressure of arterial oxygen (PaO2) in sedated dogs. METHODS Twenty healthy dogs weighing >15 kg, of mixed sex and breed, were enrolled in a randomised cross-over study. Each dog was sedated with I/M 0.015 mg/kg medetomidine and 0.5 mg/kg methadone. Twenty minutes later dogs were exposed to two 5-minute treatment periods of oxygen supplementation separated by a 15-minute washout period during which dogs were allowed to breathe room air. During the treatment periods, oxygen was delivered at a flow rate of 3 L/minute either through a face mask (face mask oxygenation), or via a tube held 2 cm from the dog's nares (flow-by oxygenation). The order in which the treatments were administered was randomised. Arterial blood was collected for blood gas analysis and rectal temperature measured at four times: prior to commencing treatments, after each treatment, and at the end of the 15 minutes washout period between treatments. RESULTS The mean PaO2 in arterial samples taken from the dogs after face mask oxygen supplementation was 371.3 (SE 13.74) mmHg which was higher than in samples taken after they received flow-by oxygen supplementation (182.2 (SE 6.741) mmHg; p<0.001). The mean PaO2 in samples taken after receiving either form of oxygen supplementation was higher than in samples taken after the dogs had been breathing room air (82.43 (SE 2.143) mmHg; p<0.001). There was no association between sex, age, weight or breed of dogs and blood gas parameters or rectal temperature (p>0.05). CONCLUSIONS Oxygen supplementation delivered using a face mask was more effective at increasing PaO2 than flow-by oxygen supplementation. Flow-by oxygen supplementation at a distance of 2 cm from the nose may be a suitable alternative when the use of a face mask is not tolerated by the patient.

A pilot study comparing the effect of orally administered esomeprazole and omeprazole on gastric fluid pH in horses.

AIMS To compare the efficacy of an enteric coated esomeprazole paste with an enteric coated omeprazole paste to increase gastric pH after oral administration in horses. METHODS Nine adult Standardbred horses were randomly assigned to three groups, each containing three horses, for a study comprising three phases of 10 days, with an 18-day washout period between each phase. In each phase, three horses received either 0.5 mg/kg esomeprazole, 1 mg/kg omeprazole or a placebo, as an oral paste, once daily for 10 days (Days 0-9). Over the course of study all horses received all three treatments. Gastric fluid samples were collected using a gastroscope on Days 1, 3, 5, 8 and 10, with food and water withheld for 16 hours prior to collection of samples. The pH of all samples was measured immediately after collection. RESULTS Mean pH (3.38; SD 1.75) of the gastric fluid samples in the horses that received the placebo was lower than in the horses that received esomeprazole (6.28; SD 1.75) or omeprazole (6.13; SD 1.75) (p<0.001). There was no difference in the mean pH between horses receiving esomeprazole and those receiving omeprazole (p=0.56). CONCLUSIONS AND CLINICAL RELEVANCE Under these study conditions, esomeprazole paste was equally as effective as omeprazole paste in increasing gastric pH in horses. Enteric coated esomeprazole, may be a therapeutic alternative to omeprazole for the prevention of gastric ulcers in horses.

Gastrojejunostomy as a treatment for gastric outflow disorders in four adult horses.

Four adult horses with histories of moderate abdominal pain and inappetence were diagnosed with delayed gastric emptying and gastric impaction attributed to pyloroduodenal obstruction (three cases) or duodenitis (one case). A stapled side-to-side gastrojejunostomy was performed on all horses. Two horses returned to work and survived ≥3 years. One horse was euthanased 6 months post-surgery due to recurrent abdominal pain, and one was found dead 5 months postsurgery after an unattended foaling.

Effects of topical treatment of cannabidiol extract in a unique manuka factor 5 manuka honey carrier on second intention wound healing on equine distal limb wounds: a preliminary study.

OBJECTIVE: Evaluate the effect of topical 1% cannabidiol on second intention wound healing in distal limb wounds of horses. DESIGN: Experimental. ANIMALS: Six Standardbred horses. METHODS: A total of five 2.5 cm × 2.5 cm full thickness skin wounds were created on the dorsomedial aspect of the metacarpi of 6 horses. Wounds were contaminated with faeces on the day of wound creation. Each wound was then assigned to a treatment group; compounded 1% cannabidiol in unique manuka factor (UMF) 5 manuka honey, UMF 5 manuka honey, UMF 20 manuka honey or saline. Each treatment was applied topically daily for a total of 42 days. Legs were bandaged and bandages were changed, daily, for 13 days postoperatively. Digital photographs of each wound were taken on day 1 then weekly for 6 weeks. Wound size, daily healing rate and total time to healing were recorded and compared statistically. RESULTS: Irrespective of the treatment, wounds did not retract as expected in the first 7 days after wound creation. There was no difference in wound area, daily healing rate, days to complete healing between treatment groups. CONCLUSIONS: This preliminary study failed to demonstrate any difference in wound healing variables between treatment groups in this model of second intention wound healing. This was unexpected due to the established effects of UMF 20 manuka honey on wound healing using the same model. This may be due to systemic effects of cannabidiol and study design. Further research into the use of cannabidiol in equine wounds is warranted.

Encephalomyocarditis virus infection in alpacas.

Encephalomyocarditis virus (EMCV) infection was detected by real-time reverse transcription PCR (qRT-PCR) in four adult alpacas (Vicugna pacos) from two properties on the Far North Coast of New South Wales (NSW) in April and May 2018 and in two adult alpacas from a third property on the Central Coast of NSW in October 2018. Viral RNA was detected in a range of samples, including blood, fresh body organs and mucosal swabs. EMCV was isolated from the blood and body organs of five of these alpacas. These animals displayed a range of clinical signs, including inappetence, colic, recumbency and death. Necropsy findings included multifocal to coalescing areas of myocardial pallor, pulmonary congestion and oedema, hepatic congestion and serosal effusion. Histopathological changes comprised acute, multifocal myocardial degeneration and necrosis, with mild, neutrophilic and lymphocytic inflammation (5/5 hearts) and mild, perivascular neutrophilic meningoencephalitis (1/3 brains). This is the first report of disease due to EMCV in alpacas under farm conditions, and it identifies EMCV infection as a differential diagnosis for acute disease and death in this camelid species. In addition to the samples traditionally preferred for EMCV isolation (fresh heart, brain and spleen), blood samples are also appropriate for EMCV detection by qRT-PCR assay.

Effect of bandaging on second intention healing of wounds of the distal limb in horses.

OBJECTIVE: To evaluate the effect of a non-occlusive dressing incorporated in a 3-layer bandage on second intention healing of wounds of the distal portion of the limb. STUDY DESIGN: Untreated wounds in 33 adult horses used in four studies using the same wound-healing model conducted over 5 years. METHODS: Standardised, full-thickness wounds were made in the skin overlying the dorsomedial aspect of the mid-metacarpus; 17 horses were bandaged with a non-occlusive dressing covered by gauze-coated cotton wool that was compressed with adhesive tape; 16 horses were left unbandaged. Wounds were photographed weekly for 9 weeks and the images were analysed electronically. RESULTS: There were significant effects associated with bandage (P < 0.0001), week (P < 0.001), and bandage by week interaction (P < 0.0001). There was no difference in wound area at the first time-point after wound creation (P = 0.38). After week 1, there was a difference between bandaged and unbandaged wounds in wound area at each measurement until the end of the study. Bandaged wounds showed greater and more prolonged retraction. Unbandaged wounds retracted for 2 weeks before beginning to contract, whereas bandaged wounds continued to retract for 3 weeks. In bandaged wounds excess granulation tissue required regular trimming, but not in unbandaged wounds. There was no difference between groups in the total days to healing or the overall rate of healing. CONCLUSIONS: These results should be treated with caution until validated with contemporaneous, controlled studies. Covering a wound with a non-occlusive dressing in a 3-layer bandage led to greater wound retraction, modulated the rate of wound contraction and promoted excessive granulation tissue. If excessive granulation tissue is excised regularly, bandaging has no effect on total time to healing.

Pilot study to quantify the time to clear dexamethasone from plasma and urine of adult horses following a single nebulisation.

OBJECTIVE: To quantify the time to clear dexamethasone from plasma and urine of horses following a single nebulisation. DESIGN: Experimental using six Standardbred mares. METHODS: Dexamethasone sodium phosphate (0.04 mg/kg) diluted in 0.9% sodium chloride was administered as an aerosol using a Flexineb E2® nebuliser. Blood samples (0, 2, 4, 6, 8, 10, 12, 24, 32, 48, 72 and 96 h) and urine samples (0, 1, 4, 8, 24, 32, 48, 72 and 96 h) were collected for analysis using liquid chromatography mass spectrometry. RESULTS: Maximum plasma concentrations (tmax ) were reached by the earliest detection point (2 h) after nebulisation (0.6-1.8 ng/mL), but was no longer detectable at 48 h. However, in one horse 0.1 ng/mL was found at 96 h after three consecutive readings of 0 ng/mL. The tmax in urine was reached by the earliest collection point (1 h) after nebulisation (3.2-23.8 ng/mL), but was no longer present in urine at 72 h in five horses, while detectable levels (0.1 ng/mL) were still present at 96 h in one horse. CONCLUSIONS: A single dose of 0.04 mg/kg of DSP administered as an aerosol through a FlexinebE2® mask was no longer detectable in blood at 48 h in six horses tested, but one horse returned a reading of 0.1 ng/mL at 96 h after having no detectable levels. Dexamethasone was not detectable in urine at 72 h in five horses but was detectable at a low concentration (0.1 ng/mL) at 96 h in one horse.

Effect of reducing inspired oxygen concentration on oxygenation parameters during general anaesthesia in horses in lateral or dorsal recumbency.

OBJECTIVE: To compare the effects of two concentrations of oxygen delivered to the anaesthetic breathing circuit on oxygenation in mechanically ventilated horses anaesthetised with isoflurane and positioned in dorsal or lateral recumbency. METHODS: Selected respiratory parameters and blood lactate were measured and oxygenation indices calculated, before and during general anaesthesia, in 24 laterally or dorsally recumbent horses. Horses were randomly assigned to receive 100% or 60% oxygen during anaesthesia. All horses were anaesthetised using the same protocol and intermittent positive pressure ventilation (IPPV) was commenced immediately following anaesthetic induction and endotracheal intubation. Arterial blood gas analysis was performed and oxygenation indices calculated before premedication, immediately after induction, at 10 and 45 min after the commencement of mechanical ventilation, and in recovery. RESULTS: During anaesthesia, the arterial partial pressure of oxygen was adequate in all horses, regardless of position of recumbency or the concentration of oxygen provided. At 10 and 45 min after commencing IPPV, the arterial partial pressure of oxygen was lower in horses in dorsal recumbency compared with those in lateral recumbency, irrespective of the concentration of oxygen supplied. Based on oxygenation indices, pulmonary function during general anaesthesia in horses placed in dorsal recumbency was more compromised than in horses in lateral recumbency, irrespective of the concentration of oxygen provided. CONCLUSION: During general anaesthesia, using oxygen at a concentration of 60% instead of 100% maintains adequate arterial oxygenation in horses in dorsal or lateral recumbency. However, it will not reduce pulmonary function abnormalities induced by anaesthesia and recumbency.

Surgical correction of metacarpophalangeal valgus deformity in an alpaca.

A 1-month-old alpaca cria presented with a 13 degree valgus deformity of the left metacarpophalangeal joint. The angular limb deformity was centered on the distal metacarpal physes. Transphyseal bridging of the physes was recommended. Two 2.7 mm cortical bone screws were placed either side of the distal metacarpal physes and a figure of eight wire was placed medially around the screw heads. The screws extended through the medial metacarpus into the axial cortex of the lateral metacarpus. Seven weeks after surgery the limb was straight and the screws and wire were removed. Transphyseal bridging of the distal metacarpal physes can be effectively used for the treatment of metacarpophalangeal valgus in crias with open physes.

Renal agenesis in an alpaca cria.

A 4-day-old alpaca cria presented for inappetence that responded to symptomatic treatment. The cria re-presented with acute signs of inappetence and azotaemia. The azotaemia persisted despite intravenous fluid therapy. There was no right kidney on ultrasound and there appeared to be perirenal oedema around the left kidney. A diagnosis of right renal agenesis and acute renal failure of the left kidney was made. The cria failed to improve and was euthanased. Necropsy examination confirmed right renal agenesis and agenesis of the right ureter and right renal artery. A section of left kidney submitted for histological examination revealed diffuse, acute, marked tubular degeneration and nephrosis. The cause of the renal failure in the left kidney was not determined.

Treatment of a metallic foreign body in the cranial cervical region of a horse.

Ingestion of foreign bodies is uncommon in horses when compared with indiscriminate grazers such as cattle. This case report describes the diagnosis and treatment of a cervical abscess in a Thoroughbred racehorse thought to be associated with ingestion of wire. Radiographic and ultrasonographic examination provided a diagnosis, and conservative treatment of the lesion with antimicrobials initially allowed the lesion to localise closer to the skin for safer surgical exploration. Intra-operative ultrasonographic imaging facilitated surgical access, removal of the foreign body, and drainage. While surgical treatment is usually necessary to resolve an abscess, initially conservative therapy may help to improve the prognosis by simplifying surgical access and reducing the risk of surgical complications.

Comparison of the effects of topical application of UMF20 and UMF5 manuka honey with a generic multifloral honey on wound healing variables in an uncontaminated surgical equine distal limb wound model.

OBJECTIVE: To compare the effect of application of manuka honey with unique manuka factor (UMF) 5 or 20 with a generic multifloral honey on equine wound healing variables. METHODS: Two full-thickness skin wounds (2.5 × 2.5 cm) were created on the metatarsus of both hindlimbs of eight Standardbred horses. The wounds on each horse were assigned to 1 of 4 treatments: UMF20 (UMF20) and UMF5 (UMF5) manuka honey; generic multifloral honey (GH); and a saline control. Bandages were changed daily for 12 days, after which treatment was stopped and the bandages were removed. Wound area was measured on day 1, then weekly until day 42. Overall wound healing rate (cm2 /day) and time to complete healing were recorded. RESULTS: There was no difference in wound area for any of the treatments on any measurement day except for day 21, where the mean wound area for wounds treated with UMF20 was smaller than the mean wound area for the UMF5-treated wounds (P = 0.031). There was no difference in mean (± SE) overall healing rate (cm2 /day) among the treatment groups. There were differences in mean (± SE) days to complete healing. Wounds treated with UMF20 healed faster than wounds treated with GH (P = 0.02) and control wounds (P = 0.01). CONCLUSIONS: Treatment of wounds with UMF20 reduced overall wound healing time compared with wounds treated with GH and control wounds. However, using this model the difference in the overall time to complete healing was small.

End-to-side anastomosis of the left ventral colon to the small colon in a neonatal foal with segmental agenesis of the large colon.

CASE REPORT: A newborn foal was referred for evaluation because it had not passed meconium, despite the administration of four enemas. Abdominal radiographs and ultrasound scans showed generalised gaseous distension of the intestine and there was no observable meconium in the colon. Positive contrast colography showed contrast medium extending to the transverse colon. An exploratory laparotomy confirmed the absence of the left and right dorsal colon and the pelvic and diaphragmatic flexures. An end-to-side anastomosis of the left ventral colon to the midpoint of the small colon was performed. The foal recovered from anaesthesia and surgery uneventfully and immediately began suckling from the mare, with no signs of abdominal pain in the postoperative period. The foal began to pass soft faeces 3 days after surgery and at 6 months after surgery the foal was clinically normal and growing at a similar rate to its cohort. CONCLUSION: Intestinal atresia is a rare condition in foals, but should be considered as a differential diagnosis in foals that fail to pass meconium. Early recognition and surgical intervention can offer an improved chance of short-term survival in cases where there is adequate intestine to anastomose. An end-to-side anastomosis technique can be used where an end-to-end technique is not practical because of the difference in diameter of the proximal and distal intestinal segments.

Enteral fluid therapy in large animals.

Enteral fluids administered alone, or in conjunction with intravenous fluids, are reported to be useful for the treatment of dehydration and electrolyte loss associated with diarrhoea in a number of species, following exercise in horses and for feed impaction of the large intestine of horses. Enteral fluids are suitable for treatment of mild to moderately dehydrated patients with some intact intestinal epithelium and motile small intestine. In patients that will drink voluntarily or tolerate nasal intubation the use of enteral fluids may avoid the complications associated with intravenous fluid administration. However the labour costs associated with repeated nasal intubation in intensively managed patients requiring large volumes of fluids may make the use of enteral fluids less economical than intravenous fluid administration. Enteral fluid use alone is contraindicated in patients that are severely dehydrated and/or in hypovolaemic shock, however, if used in conjunction with intravenous fluids, the effects of villous atrophy and malnutrition may be ameliorated and the duration of hospitalisation shortened. There is a variety of commercially available enteral fluids available to veterinary practitioners. While the key components of these fluids are sodium, chloride and carbohydrates, the amounts of ions and other ingredients such as potassium, alkalising agents, amino acids and shortchain fatty acids may vary. The species of the animal, the underlying condition, and the constituents of the fluid, should influence the choice of an enteral fluid.

Exertional heat illness: a review of the syndrome affecting racing Thoroughbreds in hot and humid climates.

Metabolic heat produced by Thoroughbred racehorses during racing can rapidly elevate core body temperature (1°C/min). When environmental conditions are hot and humid, the normal physiological cooling mechanisms become ineffective. The heat accumulated may exceed a critical thermal maximum (estimated to be 42°C), which may trigger a complex pathophysiological cascade with potentially lethal consequences. This syndrome has been labelled exertional heat illness (EHI). EHI is described in humans, but has not been well documented in Thoroughbred racehorses. The clinical signs described in racehorses would suggest that the pathophysiological events affecting the central nervous (CNS) and gastrointestinal systems are similar to those described in humans. Clinical signs are progressive and include signs of endotoxaemia and increasing levels of CNS dysfunction. Initially, horses that may be mildly irritable (agitated, randomly kicking out) may progress to unmanageable (disorientation, severe ataxia, falling) and ultimately convulsions, coma and death. Currently, the approach to treatment is largely empirical and involves rapid and effective cooling, administration of drugs to provide sedation, administration of non-steroidal anti-inflammatory drugs to ameliorate the effects of endotoxaemia and glucocorticoids to stabilise cell membranes and reduce the effects of inflammation on the CNS. This review provides an overview of the current knowledge about EHI in Thoroughbred racehorses, suggests a likely pathophysiology of the syndrome in horses based on the current literature on heat illness in humans and horses, and outlines current treatment strategies being used to treat racehorses with clinical signs of EHI.

Effect of Manuka honey gel on the transforming growth factor ß1 and ß3 concentrations, bacterial counts and histomorphology of contaminated full-thickness skin wounds in equine distal limbs.

OBJECTIVE: To investigate the effect of 66% Manuka honey gel on the concentrations of transforming growth factor (TGF)-ß1 and TGF-ß3, bacterial counts and histomorphology during healing of contaminated equine distal limb wounds. METHODS: In this experimental study of 10 Standardbred horses, five full-thickness skin wounds (2 × 1.5 cm) were created on one metacarpus and six similar wounds were created on the contralateral metacarpus. Wounds were assigned to three groups: non-contaminated control wounds; contaminated control wounds; contaminated wounds treated daily with 1 mL Manuka honey gel topically for 10 days. For the contaminated wounds, faeces were applied for 24 h after wound creation. In five horses wounds were bandaged and in the other five horses wounds were left without a bandage. Biopsies were taken on days 1, 2, 7 and 10 after wounding to evaluate the effects of Manuka honey gel, wound contamination and bandaging on TGF-ß1 and TGF-ß3 concentrations, aerobic and anaerobic bacterial counts, and histomorphology. RESULTS: Manuka honey gel had no significant effect on TGF-ß1 and TGF-ß3 concentrations or wound bacterial counts. Manuka honey gel decreased wound inflammation (days 7, 10), increased angiogenesis (days 2, 7, 10), increased fibrosis and collagen organisation (day 7) and increased epithelial hyperplasia (days 7, 10). CONCLUSIONS: Treatment with Manuka honey gel resulted in a more organised granulation tissue bed early in wound repair, which may contribute to enhanced healing of equine distal limb wounds.

Mechanical and functional properties of the equine superficial digital flexor tendon.

The in vitro and in vivo mechanical properties of the superficial digital flexor tendon have been described. To date the focus has been on single load to failure testing, however refined in vivo methods may prove useful to evaluate the effects of treatment and exercise on tendons. During maximal exercise, the adult superficial digital flexor tendon operates close to its functional limits with a narrow biomechanical safety margin. This combined with exercise and age associated microdamage, and a limited adaptive ability may increase the risk of fatigue failure. Studies evaluating treatment regimens for tendonitis have focused on repair and regeneration and yielded varying results. It would appear that the superficial digital flexor tendon has a limited ability if any to adapt positively to exercise after maturity. In contrast, the foal's superficial digital flexor tendon may have a greater adaptive ability and may respond to an appropriate exercise regimen to produce a more functionally adapted tendon. Recent studies have shown that foals allowed free pasture exercise develop a larger, stronger, more elastic tendon compared to foals that were confined or subjected to a training program. Effects on the non-collagenous matrix appear to be responsible for these differences. In contrast, training or excess exercise may have permanent detrimental effects on the biomechanical and functional properties of the superficial digital flexor tendon in the foal. The implication is that the determination of optimum exercise intensity and timing, and the role of the non-collagenous matrix in tendon physiology in the young horse may hold the key to developing tendons more capable of resisting injury.

Recent advances in equine abdominal surgery.

Laparoscopy is a minimally invasive procedure that has applications as a diagnostic, therapeutic and prognostic technique. Specialized equipment is necessary to perform equine laparoscopy, and there is a large range of instruments, both disposable and non-disposable available. Laparoscopic procedures described include ovariectomy, cryptorchidectomy, adhesiolysis and herniorrhaphy. Laparoscopy can be performed in a standing or dorsally recumbent position, depending on surgeon preference, patient status and the procedure to be performed. Stapling equipment is frequently used in gastrointestinal surgery in horses. Advantages include decreased surgical time and a decrease in the risk of contamination. Stapling equipment is often used in creating anastomoses, both in the large and small intestines, as well as in vessel ligation. New surgical techniques intended to decrease adhesion formation include the use of carboxymethylcellulose and bioresorbable patches. Indwelling abdominal drains can be used for peritoneal lavage following surgery and also appear to decrease the risk of adhesion formation. Improvements in post-operative care, including the treatment of post-operative ileus and endotoxaemia can significantly improve the outcome of horses that have undergone surgery for abdominal disorders. Recommendations for the use of prokinetic agents in horses with ileus vary widely. Prokinetic agents include local anaesthetics, macrolide antimicrobials, cholinergic agonists and dopamine antagonists. Endotoxaemia is common in horses following surgery for gastrointestinal disorders. The antibiotic polymyxin B binds to the circulating endotoxin molecule, decreasing its half-life in the intra-vascular space and reducing associated inflammation. This drug appears to be an effective and affordable treatment option for horses with endotoxaemia. The use of specific cyclooxygenase inhibitors in veterinary medicine have been studied recently. Selective cyclooxygenase-2 inhibitors may provide comparable anti-inflammatory and analgesic properties to the non-selective non-steroidal anti-inflammatory drugs. These drugs appear to have similar clinical effectiveness and will hopefully minimize deleterious side effects. The optimal healing of ventral midline incisions in horses is related to many factors including appropriate suture patterns and bite size, in addition to appropriate post-operative exercise recommendations. Recent advances in surgical techniques and post-operative care should decrease the morbidity and mortality associated with abdominal surgery. This article provides an overview of some of these advances.