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Featured researches published by I. M. Bowen.


Equine Veterinary Journal | 2010

Comparison of radiography and scintigraphy in the diagnosis of dental disorders in the horse

R. Weller; L. Livesey; Johann Maierl; K. Nuss; I. M. Bowen; E. R. J. Cauvin; Martin Weaver; J. Schumacher; S. A. May

Scintigraphy, with 99mTechnetium methylenediphosphonate (99mTc-MDP) and 99mTc-labelled leucocytes, was compared to radiography in the diagnosis of dental disease in the horse in a prospective case-controlled study, comprising 30 horses with clinical signs of dental disease and 30 control horses. In each case, right and left lateral, ventral and dorsal soft tissue and bone phase scintigraphic images were obtained after i.v. injection of 1 GBq/100 kg bwt 99mTc-MDP, using a gamma camera. The same views were acquired in 10 horses with clinical signs of dental disease and 12 control horses after injection of 99mTc-labelled leucocytes. Standard radiographic projections of the paranasal sinuses and of the apices of the maxillary and mandibular teeth were obtained. The scintigraphs and radiographs were assessed subjectively by 2 board-certified surgeons and one board-certified radiologist, with extensive experience of equine radiology, from who the clinical history was withheld. Sensitivity, specificity and kappa, as a measure of agreement, were calculated for the different methods. Bone phase images were also scored subjectively on a scale from 0 to 3 on the basis of isotope uptake over the teeth. Regions of interest were defined over the teeth, and normal teeth compared to diseased counterparts. Total scintigraphic counts were related to the age of the animal and to the disease process. Differences in density ratios between left and right teeth were evaluated using the Mann-Whitney Test. Dental disease was confirmed in 22 horses at surgery or postmortem examination. Horses with dental disease showed a significant increase in scintigraphic activity over the affected tooth compared to the contralateral tooth, with a typical pattern for different diseases. The sensitivity of scintigraphy with 99mTc-MDP proved to be excellent (95.5%), whereas the specificity was moderate (86.4%). In contrast, radiography had excellent specificity (95.0%) and a low sensitivity (51.5%). The greatest sensitivity and specificity were achieved by evaluating radiographs and scintigrams together. The objective scintigraphic density ratios were found to be significantly different between diseased and control horses. The results of this study suggest that, if a density ratio of 1.5 or greater between a suspected diseased tooth and its contralateral number is regarded as abnormal, only 1% false positive diagnoses and 20% false negative diagnoses will occur. In contrast, scintigraphy with 99mTc-labelled leucocytes was not very successful, due to the lack of anatomical detail provided by this technique, which made identification of the diseased tooth impossible. Accurate radiographic interpretation of dental disease presents difficulties, both in terms of missed diagnoses and mistaken diagnoses. Scintigraphy complements radiographic examination of dental structures by providing information important for accurate diagnosis and is, therefore, conceived to be essential for selection of the appropriate treatment for dental disease.


Equine Veterinary Journal | 2010

Cardiopulmonary effects and pharmacokinetics of i.v. dexmedetomidine in ponies

R. Bettschart-Wolfensberger; S.L. Freeman; I. M. Bowen; F. S. Aliabadi; R. Weller; M. Huhtinen; Kathy W. Clarke

REASONS FOR PERFORMING STUDY Currently available sedatives depress cardiopulmonary function considerably; therefore, it is important to search for new, less depressive sedatives. The study was performed to assess duration and intensity of cardiopulmonary side effects of a new sedative, dexmedetomidine (DEX), in horses. OBJECTIVES To study pharmacokinetics and cardiopulmonary effects of i.v. DEX. METHODS Pharmacokinetics of 3.5 microg/kg bwt i.v. DEX were studied in a group of 8 mature (mean age 4.4 years) and 6 old ponies (mean age 20 years). Cardiopulmonary data were recorded in mature ponies before and 5, 10, 20, 30, 45 and 60 mins after administration of DEX 3.5 microg/kg bwt i.v. Data were analysed using ANOVA for repeated measures, and where appropriate Dunnetts t test was used to detect differences from resting values (P < 0.05). RESULTS Within 2 h after DEX administration, plasma levels were beyond limits of quantification (0.05 ng/ml). Mean values for kinetic parameters for mature and old ponies were: Cmax (ng/ml) 4.6 and 3.8, t 1/2 (min) 19.8 and 28.9 and AUC (ng.min/ml) 34.5 and 44.3, respectively. Heart rate, central venous pressure, pulmonary artery pressure and pulmonary capillary wedge pressure did not change significantly compared to presedation values throughout the 60 min observation period. Compared to presedation values, stroke volume and mixed venous PO2 were reduced for the first 5 mins, paralleled by an increase in systemic and pulmonary vascular resistance. Cardiac index was reduced for the first 10 mins, arterial blood pressures at 20, 30 and 45 mins and respiratory rate throughout the 60 min observation period, but no change in arterial PO2 or PCO2 occurred. CONCLUSIONS DEX administration i.v. causes similar cardiopulmonary changes to those caused by other alpha-2 adrenoceptor agonists, but of very short duration. DEX is redistributed particularly rapidly. POTENTIAL RELEVANCE DEX might be safer for sedation of horses because of its very short-lasting cardiopulmonary side effects. For long duration sedation, its kinetics favour its use as a continuous infusion.


Veterinary Record | 2009

Effect of left-sided valvular regurgitation on mortality and causes of death among a population of middle-aged and older horses.

Kim B. Stevens; Celia Marr; J. Horn; Dirk U. Pfeiffer; Justin D. Perkins; I. M. Bowen; E J Allan; J Campbell; J. Elliott

The effect of left-sided valvular regurgitation (LSVR) on the mortality of middle-aged and older horses was investigated in a prospective cohort study involving 19 yards and 1153 horses. The horses were examined to determine whether they had a cardiac murmur and its type, and their age, sex, breed type and occupation were recorded. They were followed up at intervals of two years by postal questionnaire, and after four years information on 773 horses was available. There was no significant difference in the mortality of the horses with and without LSVR, but small horses had a significantly higher risk of having LSVR than small ponies (odds ratio [OR] 2·33), and older horses were slightly more likely to have LSVR than young horses (OR 1·07). Twenty-nine per cent of the deaths reported by the owners were due to orthopaedic problems, 23·3 per cent to gastrointestinal problems, and only 7·9 per cent to cardiovascular problems. Orthopaedic problems were the main cause of death in the horses, and gastrointestinal problems were the main cause of death in the ponies.


Veterinary Record | 1999

Comparison of radiography, scintigraphy and ultrasonography in the diagnosis of a case of temporomandibular joint arthropathy in a horse

R. Weller; E. R. J. Cauvin; I. M. Bowen; S. A. May

Diagnosis of temporomandibular joint disease in the horse presents a challenge to the equine veterinarian. This case report illustrates a combined imaging approach using radiography, scintigraphy and ultrasonography in a horse with severe arthropathy of the left temporomandibular joint Radiographs were inconclusive. Scintigraphy with Tc99m methylenediphosphonate localised, but failed to characterise the disease process; ultrasonography was the only imaging method which both localised and characterised the lesion. Ultrasonography proved to be a relatively cheap, technically easy to perform and non-invasive method for the assessment of the disease.


Equine Veterinary Journal | 2010

Medetomidine-ketamine anaesthesia induction followed by medetomidine-propofol in ponies: infusion rates and cardiopulmonary side effects.

R. Bettschart-Wolfensberger; I. M. Bowen; S.L. Freeman; R. Weller; Kathy W. Clarke

REASONS FOR PERFORMING STUDY To search for long-term total i.v. anaesthesia techniques as a potential alternative to inhalation anaesthesia. OBJECTIVES To determine cardiopulmonary effects and anaesthesia quality of medetomidine-ketamine anaesthesia induction followed by 4 h of medetomidine-propofol anaesthesia in 6 ponies. METHODS Sedation consisted of 7 microg/kg bwt medetomidine i.v. followed after 10 min by 2 mg/kg bwt i.v. ketamine. Anaesthesia was maintained for 4 h with 3.5 microg/kg bwt/h medetomidine and propofol at minimum infusion dose rates determined by application of supramaximal electrical pain stimuli. Ventilation was spontaneous (F(I)O2 > 0.9). Cardiopulmonary measurements were always taken before electrical stimulation, 15 mins after anaesthesia induction and at 25 min intervals. RESULTS Anaesthesia induction was excellent and movements after pain stimuli were subsequently gentle. Mean propofol infusion rates were 0.89-0.1 mg/kg bwt/min. No changes in cardiopulmonary variables occured over time. Range of mean values recorded was: respiratory rate 13.0-15.8 breaths/min; PaO2 29.1-37.9 kPa; PaCO2 6.2-6.9 kPa; heart rate 31.2-40.8 beats/min; mean arterial pressure 90.0-120.8 mmHg; cardiac index 44.1-59.8 ml/kg bwt/min; mean pulmonary arterial pressure 11.8-16.4 mmHg. Recovery to standing was an average of 31.1 mins and ponies stood within one or 2 attempts. CONCLUSIONS In this paper, ketamine anaesthesia induction avoided the problems encountered previously with propofol. Cardiovascular function was remarkably stable. Hypoxaemia did not occur but, despite F(I)O2 of > 0.9, minimal PaO2 in one pony after 4 h anaesthesia was 8.5 kPa. POTENTIAL RELEVANCE The described regime might offer a good, practicable alternative to inhalation anaesthesia and has potential for reducing the fatality rate in horses.


Equine Veterinary Journal | 2010

Demonstration of regional differences in equine ventricular myocardial velocity in normal 2-year-old thoroughbreds with Doppler tissue imaging

M F Sepulveda; Justin D. Perkins; I. M. Bowen; Celia M. Marr

REASONS FOR PERFORMING STUDY Doppler tissue imaging (DTI) is a novel noninvasive method by which myocardial velocity can be assessed directly and it allows regional, rather than global, cardiac function to be evaluated. HYPOTHESIS That regional differences in myocardial velocities exist within the equine ventricle. OBJECTIVES To develop a repeatable examination technique for DTI in horses, describe DTI findings in various regions of the normal equine ventricle, compare colour (CDTI) and spectral (SDTI) techniques of DTI, and document regional differences in myocardial velocity. METHODS Five regions of the ventricles (right ventricular wall, interventricular septum and left, right and caudal regions of the left ventricle) were evaluated using SDTI and CDTI in 20 clinically normal Thoroughbreds age 2 years. Individual repeatability of the method was determined by examination of one 6-year-old Thoroughbred on 6 occasions. RESULTS Three major movements were observed in the ventricular walls in systole, early diastole and late diastole. The interventricular septum had a complex pattern of movement. The left region of the left ventricle and interventricular septum had the most rapid movement. The individual repeatability of CDTI was poor, while in systole and early diastole, but not late diastole, SDTI produced repeatable estimates of maximal myocardial velocity. The different velocity estimates obtained with SDTI and CDTI are not interchangeable. Regional differences in the peak mean and maximal myocardial velocities were found in systole and early diastole (P<0.05), but were not identified in late diastole. CONCLUSIONS The SDTI modality appears to produce the most repeatable data. There are regional differences in myocardial velocity within the equine ventricles for systole and early diastole. POTENTIAL RELEVANCE DTI shows potential as a tool for studying regional myocardial movement both in clinical cases suspected of having myocardial dysfunction and in a research setting. In particular, SDTI offers potential as a direct and noninvasive means to study early diastolic function of the equine ventricles.


Veterinary Record | 2000

Functional and histopathological evidence of cardiac parasympathetic dysautonomia in equine grass sickness

J. D. Perkins; I. M. Bowen; R. W. Else; C. M. Marr; I. G. Mayhew

The parasympathetic terminal cardiac ganglia were examined in three normal horses and in five horses with grass sickness. Histopathological changes, consistent with those observed in other ganglia of horses with grass sickness, were identified in the terminal cardiac ganglia of the affected horses. A functional analysis of cardiac autonomic control by time domain analysis (TDA) of heart rate variability was applied to eight horses with grass sickness, and double-paired to 16 normal horses on the basis of their age, sex and breed, and the time of day at which the electrocardiographs were obtained. There were statistically significant differences between the normal and the affected horses in terms of the triangular index (P=0.01), a geometric method of TDA, the sNN100 index (P=0.009), a statistical method of TDA, and the R to R interval (P<0.0005). These results indicate that there is a pathological and functional parasympathetic decentralisation to the heart in equine grass sickness.


Veterinary Record | 2000

Cardiopulmonary effects of romifidine and detomidine used as premedicants for ketamine/halothane anaesthesia in ponies.

S.L. Freeman; I. M. Bowen; Regula Bettschart-Wolfensberger; G. C. W. England

The cardiopulmonary effects of romifidine at 80 pig/kg (R80) or 120 pig/kg (R120), and detomidine at 20 pg/kg (D20) when used as premedicants for ketamine/halothane anaesthesia were investigated in six ponies. Using a blinded crossover design, acepromazine (0-04 mg/kg) was administered followed by the alpha-2 agonist. Anaesthesia was induced with ketamine at 2-2 mg/kg and maintained with halothane (expired concentration 1-0 per cent) in oxygen for three hours. During anaesthesia, arterial blood pressure, cardiac index, PaO2 and PmvO2 decreased, and systemic vascular resistance and PaCO2 increased. The cardiac indices for R80, R120 and D20 were, respectively, 39,39 and 32 ml/kg/minute at 30 minutes and 29, 29 and 26 ml/kg/minute at 180 minutes. The alpha-2 agonists had similar cardiovascular effects, but PaO2 was significantly lower with R120. The quality of anaesthesia was similar in all three groups.


Veterinary Record | 1998

Sudden cardiac arrest in an anaesthetised horse associated with low venous oxygen tensions

T. M. E. McGoldrick; I. M. Bowen; K. W. Clarke

References BARONE, R. (1964) Anatomie des Equides Domestiques. Vol 2, part 2. Lyon. p 577 BECKER, M., FREWEIN, J., RAPP, H. & STECHELE, M. (1991) Der praktische Tierarzt 5, 399 BLYTHE, L. (1979) Dissertation in partial fulfilment of the requirements for the degree of Doctor of Philosophy, Department of Comparative Pathology, University of California, Davis BOHME, G. (1992) Lehrbuch der Anatomie der Haustiere. Eds R. Nickel, A. Schummer, E. Seiferle. Vol 4. 3rd edn. Berlin and Hamburg, P. Parey. p 261 DENOIX, J. (1993) Pratique Veterinaire Equine 25, 173 DYCE, K., SACK, W. & WENSING, C. (1996) Textbook of Veterinary Anatomy. Philadelphia, W. B. Saunders. p 607 DYSON, S. (1991) Equine Practice. Ed Boden. London. p 21 1 FORD, T., ROSS, M. & ORSINI, P. (1989) Veterinary Surgery 18, 146 KEG, P., MERKENS, H., BARNEVELD, A., DIK, K. & VAN DEN BELT, A. (1992) Journal of Veterinary Medicine A 39, 349 DE LAHUNTA, A. & HABEL, R. (1986) Applied Veterinary Anatomy. Philadelphia, W. B. Saunders. p 106 NOMINA ANATOMICA VETERINARIA (1994) Veterinar-Anatomisches Institut der Universitat Zurich, Switzerland. p 131 SCHMOTZER, W. & TIMM, K. (1990) Veterinary Clinics of North America, Equine Practice 6, 705 VAN WASSENHOVE, A. (1949) Vlaams Diergeneeskundig Tijdschrift 18, 145 WILSON, D., BABER, G., PIJANOWSKI, G., BOERO, M. & BADERTSCHER, R. (1991) American Journal of Veterinary Research 52, 133


Veterinary Record | 2012

Primary cardiac lymphoma in a 10-year-old equine gelding

L. C. Penrose; A. Brower; G. Kirk; I. M. Bowen; Gayle Hallowell

PRIMARY cardiac lymphoma (PCL) is a rare tumour in all species (Sims and others 2003, Shinohara and others 2005, Miguel and Bestetti 2011, Petrich and others 2011) affecting the myocardium and/or pericardium (Shinohara and others 2005, Petrich and others 2011). PCL has been reported in cats, dogs and human beings, but prior case descriptions in horses were not identified in the literature. In horses, four categories of equine lymphoma are described: multicentric, thymic, alimentary and cutaneous (van den Hoven and Franken 1983) plus occasional anomalous cases (Meschter and Allen 1984, Staempfli and others 1988, Rhind and Dixon 1999, Taintor and Schleis 2011). A 10-year-old Cob gelding was presented with lethargy, weight loss and anorexia. On initial assessment, the horse was quiet, dull but responsive. Clinical examination revealed sinus tachycardia (64 bpm), which was confirmed by electrocardiography. A grade IV/VI pansystolic decrescendo murmur and a grade II/VI holodiastolic murmur, both loudest over the left fourth intercostal space, were auscultated. Jugular pulse quality and filling, and capillary refill time and colour were normal. The horse was tachypnoeic (20 bpm) with bronchovesicular sounds over both hemithoraces, more so on the right-hand side. Rectal temperature was normal. Muscle fasciculations of the proximal forelimb and weakness were observed, but no proprioceptive deficits suggestive of neurological disease were noted. Two-dimensional and M-mode echocardiography revealed normal cardiac dimensions with increased contractility (fraction shortening of 60 per cent; normal range 27 to 47 per cent) and …

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S.L. Freeman

University of Nottingham

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Celia M. Marr

Royal Veterinary College

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R. Weller

Royal Veterinary College

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S. A. May

Royal Veterinary College

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T J Potter

Royal Veterinary College

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J. Elliott

Royal Veterinary College

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