David Bardell

Factors associated with survival to hospital discharge following endoscopic treatment for synovial sepsis in 214 horses

REASONS FOR PERFORMING STUDY To determine risk factors involved in survival to hospital discharge of cases of synovial sepsis. OBJECTIVES Investigate pre-, intra- and post operative factors involved in short-term survival of horses undergoing endoscopic treatment for synovial sepsis. STUDY DESIGN Retrospective case series. METHODS Clinical data were obtained for horses (>6 months old) undergoing endoscopic surgery as part of management for synovial sepsis over a 7-year period in a single hospital population. Descriptive data were generated for pre-, intra- and post operative variables. Multivariable logistic regression analysis was used to develop 3 models related to presurgical, surgical and post surgical stages of management with outcome defined as survival to hospital discharge. RESULTS Two hundred and fourteen horses were included. In Model 1 (preoperative variables), increased preoperative synovial fluid total protein (TP) was associated with nonsurvival (OR 0.88, 95% CI 0.83-0.94, P<0.001) whereas the presence of a wound on admission was associated with survival (OR 4.75, 95% CI 1.21-18.65, P = 0.02). Model 2 (intraoperative variables) revealed that factors associated with decreased survival were anaesthetic induction outside of normal working hours (OR 0.36, 95% CI 0.15-0.88 P = 0.02) and presence of moderate/severe synovial inflammation at surgery (OR 0.28, 95% CI 0.12-0.67, P = 0.004). Model 3 (post operative variables) showed that increased post operative synovial fluid TP (OR 0.94, 95% CI 0.90-0.98, P = 0.013) and undertaking more than one endoscopic surgery for treatment (OR 0.19, 95% CI 0.05-0.70, P = 0.005) were associated with nonsurvival. Cut-off values for predicting survival were 55-60 g/l for preoperative and 50-55 g/l for post operative TP measurements. CONCLUSIONS This study has identified factors associated with altered likelihood of survival to hospital discharge following endoscopic surgery for synovial sepsis. Prognosis for survival to hospital discharge can be based on evidence from this study at the key stages of management of horses with synovial sepsis.

Use of continuous positive airway pressure (CPAP) to optimise oxygenation in anaesthetised horses – a clinical study

REASONS FOR PERFORMING STUDY Hypoxaemia is a common problem during equine anaesthesia. Continuous positive airway pressure (CPAP) is a ventilation mode routinely employed in man to overcome hypoxaemia but has not been objectively assessed in horses. OBJECTIVES To test the effects of CPAP on oxygenation and its indices in anaesthetised horses in a clinical setting. METHODS Twenty-four healthy horses requiring anaesthesia in dorsal recumbency were anaesthetised using a standard protocol. Following orotracheal intubation and connection to an anaesthetic machine capable of applying CPAP, horses were randomly allocated to ventilate at physiological airway pressure measured at the airway opening (Group PAP) or to receive CPAP of 8 cmH2O (Group CPAP). Arterial blood gas analysis was performed as soon as arterial cannulation was achieved and 30, 60 and 90 min after induction. If PaCO2 increased above 9.31 kPa controlled ventilation was initiated. Groups were compared using a general linear model. RESULTS Horses receiving CPAP had significantly higher PaO2 and calculated oxygen indices than horses receiving PAP. No significant differences in ventilation indices were observed between the 2 groups. Eight horses receiving PAP and 5 receiving CPAP required controlled ventilation. No differences in dobutamine requirements or mean arterial pressures were recorded. CONCLUSIONS Continuous positive airway pressure of 8 cmH2O improved oxygenation indices in dorsally recumbent horses without significantly influencing ventilation. POTENTIAL RELEVANCE Continuous positive airway pressure reduces the incidence of hypoxaemia in anaesthetised horses. Further research is warranted to elucidate the effects of CPAP on the cardiovascular system.

Use of acetaminophen (paracetamol) as a short-term adjunctive analgesic in a laminitic pony.

We would like to describe the use of acetaminophen (paracetamol) as an adjunctive analgesic agent in a pony with severe laminitis. An 8-year-old obese Welsh section C gelding weighing 450 kg was presented to the Philip Leverhulme Equine Hospital. The pony was sweating and had an unsteady gait. The heart rate was 84 beats minute and the Obel laminitis grade was 4 (Menzies-Gow et al. 2010). Following further examination and diagnostic tests, equine metabolic syndrome with laminitis in all four hooves was diagnosed. Marked rotation (10 , 10.4 and 10.6 ) and sinking of three of the distal phalanges was evident. Based on an estimated weight, morphine (morphine sulphate; Martindale Pharmaceuticals, UK) 0.13 mg kg and flunixin (Meflosyl; Pfizer Animal Health, UK) 0.89 mg kg were administered intravenously (IV). Subsequently the heart rate reduced to 64 beats minute, sweating and weight-shifting decreased and demeanor improved. Four hourly monitoring of clinical and laboratory parameters was instituted. The pony was fed soaked hay and all four hooves were packed with silicone putty (Newmarket Sole Support, Newmarket Premixes Ltd, UK). Despite this management, the pony still was weight-shifting, lying down frequently and remained tachycardic. Further analgesia was provided, with varying degrees of efficacy, over the subsequent 4 days, including phenylbutazone (Equipalazone; Dechra Veterinary Products Ltd, UK) at 4.4 mg kg twice daily per os (PO), lidocaine (lidocaine 0.2% in 5% glucose; Fresenius Kabi, UK) 1.3 mg kg IV bolus followed by 3 mg kg hour IV infusion and morphine 0.08 mg kg epidurally. Unfortunately by day 5, technical and financial limitations led to the removal of both IV and epidural catheters. The pony was receiving phenylbutazone 4.4 mg kg twice daily IV but was still graded as Obel 3, had a poor appetite and demonstrated frequent weight-shifting. Heart rate was now 44 beats minute. Euthanasia was discussed with the owners at this stage. An adjunctive analgesic was sought which would have a rapid onset with few side-effects, be inexpensive, suitable for enteral administration and be appropriate to use under the licensing cascade. Acetaminophen (Paracetamol; M&A Pharmachem Ltd, UK) 25 mg kg was administered via a nasogastric tube on day 6. Within 2 hours the pony showed improved demeanor, appetite, mobility and stance and reduced Obel grade to 2. The decision was made with the owner’s consent to continue treatment and phenylbutazone treatment 4.4 mg kg IV twice daily was continued. Fortytwo hours from first administration of acetaminophen, the Obel grade increased to 3 and the pony was recumbent more frequently, and had a reduced appetite. A second dose of acetaminophen 20 mg kg was crushed into water and administered PO by dosing syringe. Within 1 hour, the Obel grade was 2. The dosing was maintained thereafter with acetaminophen 20 mg kg and phenylbutazone 4.4 mg kg, both twice daily PO. On day 9, the pony was shod with plastic heart bar shoes, after which the Obel grade was 0 and the pony did not display a laminitic gait. The pony was discharged on day 11 and received a further week of acetaminophen at 20 mg kg and 1 week of phenylbutazone 3.3 mg kg, then phenylbutazone 2.2 mg kg for a further week, all twice daily PO. The pony remained comfortable until a recurrence of laminitic pain after 10 weeks, at which stage the owners elected to have the pony euthanased. Acetaminophen (N-acetyl-p-aminophenol) is a phenolic compound which has a marketing authorization combined with codeine (Pardale-V; Dechra Veterinary Products, UK) for oral use in dogs for the short-term treatment of pain. Analgesia is thought

Reversal of profound rocuronium block monitored in three muscle groups with sugammadex in ponies

BACKGROUND This clinical study evaluated the speed of reversal of profound rocuronium block in ponies using sugammadex and investigated the differences in onset and recovery from block in three different muscle groups. METHODS Anaesthesia was induced and maintained with isoflurane in oxygen 100% in eight ponies. Neuromuscular monitoring was performed at each site using acceleromyography: in the extensor muscles of the pelvic limb (peroneal nerve) and thoracic limb (radial nerve), and in the orbicularis oris muscle (OOM; facial nerve). Rocuronium 0.6 mg kg(-1) i.v. was administered, followed 5 min later by sugammadex 4 mg kg(-1) i.v. Onset time (onsetROC), maximum block, and time to recovery of the train-of-four ratio to 0.9 (TOFR=0.9) were recorded. The differences between monitored sites were compared using one-way anova followed by a post hoc Dunns test. RESULTS Onset of ROC was significantly delayed in OOM compared with both limbs [pelvic limb, thoracic limb, and OOM: 43.1 (sd 16.9), 50.6 (15.9), and 204.4 (35.8) s, respectively; P<0.001]. Complete block was achieved in the pelvic and thoracic limbs, but in none of the eight ponies in the OOM [mean T1=15.3 (9.4)%; range: 7-36%]. No differences were observed between muscle sites in recovery to TOFR=0.9 [pelvic limb, thoracic limb, and OOM: 2.3 (0.9), 3.4 (1.7), and 2.8 (2.1) min, respectively]. No adverse effects of sugammadex were detected throughout the study period. CONCLUSIONS Sugammadex can be used to reverse profound rocuronium-induced block in ponies during isoflurane anaesthesia. Thoracic limb muscles represent a suitable alternative for monitoring neuromuscular block compared with pelvic limb muscles.

Comparison of the EPOC and i-STAT analysers for canine blood gas and electrolyte analysis

OBJECTIVES A prospective study to evaluate agreement and precision of a new point-of-care portable analyser, the EPOC analyser, compared with the i-STAT analyser in canine blood. METHODS Blood samples (68 venous and 32 arterial) were obtained from 63 client-owned dogs for clinical reasons and surplus blood was used to analyse agreement between the EPOC and i-STAT analysers. Precision of the EPOC analyser was also assessed by repeat analysis of 20 samples. Measured analytes included pH, partial pressures of carbon dioxide and oxygen and concentrations of sodium, potassium, ionised calcium, glucose and haematocrit. Haemoglobin, base excess, bicarbonate and saturation of haemoglobin with oxygen were calculated. RESULTS EPOC precision was acceptable, but agreement was poor for sodium, haematocrit, haemoglobin and base excess. Overall, method comparison was poor for pH, partial pressure of oxygen, sodium, haematocrit, haemoglobin and base excess. CLINICAL SIGNIFICANCE The EPOC analyser is useful for dogs, although clinically significant differences between the EPOC and i-STAT analysers exist for some analytes, and as such these analysers should not be used interchangeably.

Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015.

Reasons for performing study Colic remains a life-threatening condition in the horse. Ischaemia and reperfusion following correction of small intestinal strangulation may produce oxidative stress. The ability to withstand oxidative stress depends on antioxidant levels and may be linked to horse survival. Objectives To measure peripheral antioxidant levels in horses undergoing exploratory laparotomy with small intestinal strangulation. Study design Case–control study. Methods Blood and plasma were collected from horses undergoing exploratory laparotomy for small intestinal strangulation and stored at −80°C. Controls involved non-colic horses. Total plasma glutathione was measured spectrophotometrically at 412 nm using the 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB, Ellmans reagent) reaction. Samples containing scavenger (to remove reduced glutathione, GSH) were used to measure oxidised glutathione (GSSG). Glutathione reductase (GR) activity (u/l) was measured as the rate of GSH production at 412 nm. Glutathione peroxidise (GPx) activity (u/l) was measured as the change in optical density (340 nm) following the consumption of NADPH after GSSG production. All assays were purchased from BioAssay Systems (Hayward, California). Clinical data including arterial blood gas analysis were collected on admission. Results Glutathione reductase activity in horses with strangulating small intestinal lesions was significantly reduced compared to control horses (12.2 ± 1.1 u/l vs. 15.9 ± 0.8 u/l, P = 0.03, n = 6) whereas GPx activity did not significantly differ between colic and control horses (155.7 ± 48.7 u/l vs. 167.3 ± 30.1 u/l, P = 0.84, n = 6). Total glutathione, reduced or oxidised glutathione did not differ significantly between control and colic horses. A positive correlation existed between GR activity and Ca2+ (r = 0.93) and K+ (r = 0.75) whereas a strong negative correlation was present between GR activity and HCO3− (r = −0.92) and PaCO2 (r = −0.96). Conclusions Reduced plasma glutathione reductase activity with small intestinal strangulation indicates oxidative stress and may be related to systemic electrolyte/bicarbonate abnormalities. Ethical animal research: Study approval No. VREC219a. Explicit owner informed consent for inclusion of animals in this study was not stated. Source of funding: Supported by the School of Veterinary Sciences, University of Liverpool. Competing interests: None declared.

Evaluation of a new handheld point-of-care blood gas analyser using 100 equine blood samples

OBJECTIVES To determine whether the Enterprise point-of-care blood analysis system (EPOC) produces results in agreement with two other blood gas analysers in regular clinical use (i-STAT and Radiometer ABL77) and to investigate the precision of the new machine when used with equine whole blood. STUDY DESIGN Prospective, randomized, non-blinded, comparative laboratory analyser study. ANIMALS Horses admitted to a university teaching hospital requiring arterial or venous blood gas analysis as part of their routine clinical management. METHODS One hundred equine blood samples were run immediately, consecutively and in randomized order on three blood gas analysers. Results of variables common to all three analysers were tested for agreement and compared with guidelines used in human medicine. These require 80% of results from the test analyser to fall within a defined range or percentage of results from the comparator devices to achieve acceptability. Additionally, 21 samples were run twice in quick succession on the EPOC analyser to investigate precision. RESULTS Agreement targets were not met for haematocrit, haemoglobin and base excess for either i-STAT or ABL77 analysers. EPOC precision targets were not met for partial pressure of carbon dioxide, ionized calcium, haematocrit and haemoglobin. Overall comparative performance of the EPOC was good to excellent for pH, oxygen tension, potassium, bicarbonate and oxygen saturation of haemoglobin, but marginal to poor for other parameters. CONCLUSIONS AND CLINICAL RELEVANCE The EPOC may be useful in performing analysis of equine whole blood, but trend analysis of carbon dioxide tension, ionized calcium, haematocrit and haemoglobin should be interpreted with caution. The EPOC should not be used interchangeably with other blood gas analysers.OBJECTIVES To determine whether the Enterprise point-of-care blood analysis system (EPOC) produces results in agreement with two other blood gas analysers in regular clinical use (i-STAT and Radiometer ABL77) and to investigate the precision of the new machine when used with equine whole blood. STUDY DESIGN Prospective, randomized, non-blinded, comparative laboratory analyser study. ANIMALS Horses admitted to a university teaching hospital requiring arterial or venous blood gas analysis as part of their routine clinical management. METHODS One hundred equine blood samples were run immediately, consecutively and in randomized order on three blood gas analysers. Results of variables common to all three analysers were tested for agreement and compared with guidelines used in human medicine. These require 80% of results from the test analyser to fall within a defined range or percentage of results from the comparator devices to achieve acceptability. Additionally, 21 samples were run twice in quick succession on the EPOC analyser to investigate precision. RESULTS Agreement targets were not met for haematocrit, haemoglobin and base excess for either i-STAT or ABL77 analysers. EPOC precision targets were not met for partial pressure of carbon dioxide, ionized calcium, haematocrit and haemoglobin. Overall comparative performance of the EPOC was good to excellent for pH, oxygen tension, potassium, bicarbonate and oxygen saturation of haemoglobin, but marginal to poor for other parameters. CONCLUSIONS AND CLINICAL RELEVANCE The EPOC may be useful in performing analysis of equine whole blood, but trend analysis of carbon dioxide tension, ionized calcium, haematocrit and haemoglobin should be interpreted with caution. The EPOC should not be used interchangeably with other blood gas analysers.

Horses Auto-Recruit Their Lungs by Inspiratory Breath Holding Following Recovery from General Anaesthesia

This study evaluated the breathing pattern and distribution of ventilation in horses prior to and following recovery from general anaesthesia using electrical impedance tomography (EIT). Six horses were anaesthetised for 6 hours in dorsal recumbency. Arterial blood gas and EIT measurements were performed 24 hours before (baseline) and 1, 2, 3, 4, 5 and 6 hours after horses stood following anaesthesia. At each time point 4 representative spontaneous breaths were analysed. The percentage of the total breath length during which impedance remained greater than 50% of the maximum inspiratory impedance change (breath holding), the fraction of total tidal ventilation within each of four stacked regions of interest (ROI) (distribution of ventilation) and the filling time and inflation period of seven ROI evenly distributed over the dorso-ventral height of the lungs were calculated. Mixed effects multi-linear regression and linear regression were used and significance was set at p<0.05. All horses demonstrated inspiratory breath holding until 5 hours after standing. No change from baseline was seen for the distribution of ventilation during inspiration. Filling time and inflation period were more rapid and shorter in ventral and slower and longer in most dorsal ROI compared to baseline, respectively. In a mixed effects multi-linear regression, breath holding was significantly correlated with PaCO2 in both the univariate and multivariate regression. Following recovery from anaesthesia, horses showed inspiratory breath holding during which gas redistributed from ventral into dorsal regions of the lungs. This suggests auto-recruitment of lung tissue which would have been dependent and likely atelectic during anaesthesia.

Lack of association between arterial oxygen tensions in horses during exploratory coeliotomy and post-operative incisional complications: A retrospective study.

The aim of this retrospective study was to determine if there was an association between the lowest arterial blood oxygen tensions (PaO2) measured during anaesthesia and post-operative incisional complications in horses. Clinical records of 278 horses undergoing ventral midline coeliotomy from 1 January 2010 to 31 December 2013 were examined. The frequency of incisional complications was 32.0% (n = 89). In a multivariable model, intra-operative arterial blood oxygen tensions (PaO2) were not significantly associated with development of an incisional complication (P = 0.351). Using hypertonic (7.2%) saline (P = 0.028, OR 3.167, 95% CI 1.132-8.861), increasing total plasma protein concentration (TP) (P = 0.002, OR 1.061 per g/L, 95% CI 1.021-1.102), an intestinal resection (P <0.001, OR 4.056, 95% CI 2.231-9.323), increasing body mass (P = 0.004, OR 1.004 per kg, 95% CI 1.001-1.006) and the use of penicillin alone compared with penicillin and gentamicin pre-operatively (P = 0.009, OR 4.145, 95% CI 1.568-10.958) increased the risk of incisional complications. The study was unable to demonstrate a link between low intra-operative PaO2 and increased risk of post-operative incisional complications.

Corneal abrasion and microbial contamination in horses following general anaesthesia for non-ocular surgery

OBJECTIVE To evaluate the incidence of corneal abrasions/ulceration and microbial contamination in horses undergoing general anaesthesia. STUDY DESIGN Prospective, observational, clinical study. ANIMALS A total of 40 client-owned healthy horses scheduled for elective non-ophthalmic procedures. METHODS Conjunctival sac swabs were taken, fluorescein dye applied and digital images recorded from both eyes of the horses after preanaesthetic medication and 24 hours after recovery from general anaesthesia. A paraffin-based bland ophthalmic ointment was applied on the ocular surface intraoperatively following collection of a sample into a sterile container. All samples underwent aerobic, anaerobic and fungal culture. Subject demographics, chronology of ophthalmic ointment use, anaesthesia duration, recumbency after induction, during surgery and recovery, fluorescein uptake and culture results were recorded. Descriptive statistics were performed. RESULTS Complete data were collected from 34 horses; six (17.6%) developed mild unilateral generalized fluorescein uptake consistent with corneal abrasions. Recumbency on the operating table was the only risk factor significantly associated with corneal abrasions. A total of 11 bacterial species were identified; Staphylococcus spp. (15 eyes) and Micrococcus spp. (eight eyes) were the most frequently isolated bacteria. Two fungal species were isolated postoperatively (Aspergillus spp., Saccharomyces spp.) in two eyes. Ointment contamination was recorded in two cases (5%) but cross-contamination was not recognized. CONCLUSIONSAND CLINICAL RELEVANCE Incidence of corneal abrasion/ulceration in horses undergoing general anaesthesia and contamination rate of ophthalmic solutions are similar to those previously reported in dogs.