John G Burke

Galway Clinic Doughiska Limited, Gaillimh, Connaught, Ireland

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Publications (4)8.5 Total impact

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    ABSTRACT: Purpose To characterise changes in vertebral dimension in an ovine model of scoliosis and determine whether a reproducible curvature could be created that would be suitable for future testing of curve modifying surgical implants. Methods At a mean age of 5 weeks, 28 Scottish blackface sheep were anaesthetised. A 4 mm braided synthetic tape was laid under the left lamina of T5 and L1 and tightened to ‘hand’ tension. A scoliosis was then created by binding the six lowest ribs on the same side just distal to their rib angles and resecting a segment from each of the opposite ribs. Radiographs were taken at 4 weekly intervals, and CT images at 2, 5 and 7 months post tethering, to determine multi-planar curve progression. 20 animals were assessed at age 3 months, 12 at 41 weeks and 10 at 1 year with comparisons to five control animals. Results A significant bi-planar deformity was produced in all animals (scoliosis 32 ± 13º and lordosis 53 ± 21º 2 months post tethering; mean ± SD, n = 22). During the next 5 months the scoliosis decreased slightly (p = 0.08) but the sagittal deformity remained static: 21 ± 18° and 53 ± 19°, respectively (n = 12). The values at 7 months were associated with a mean 6 ± 4º rotational deformity. There was approximately twice as much growth in the right anterior aspects of the apical vertebrae as in the left posterior. Conclusions With appropriate care it was possible to obtain a reproducible curvature in immature sheep. The methods described are suitable for use in studies of growth modulation and other spinal devices.
    European Spine Journal 10/2014; 24(7). DOI:10.1007/s00586-014-3609-z · 2.47 Impact Factor
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    ABSTRACT: First, to determine whether scoliosis development could be limited or reversed by growth when a novel modular hinged implant was fixed to the convexity of a scoliosis created by contralateral rib and laminar tethering and unilateral rib resection in a sheep model. Second, to assess the effect and performance of the implant in normal non-tethered sheep.
    European Spine Journal 10/2014; 24(7). DOI:10.1007/s00586-014-3610-6 · 2.47 Impact Factor
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    ABSTRACT: To compare isoflurane and sevoflurane in lambs undergoing prolonged anaesthesia for spinal surgery. Prospective randomised clinical study. Eighteen Scottish blackface lambs 3-6 weeks of age and weighing 10-17 kg. After intramuscular medetomidine, anaesthesia was induced and maintained with either isoflurane (group I) or sevoflurane (group S) delivered in oxygen. Meloxicam, morphine, a constant rate infusion of ketamine and atracurium were given intravenously (IV) during surgery. Lungs were ventilated to maintain normocapnia. with peak inspiratory pressures of 20-25 cmH(2) O. Ephedrine or dextran 40% was administered when mean arterial pressure (MAP) was <55 mmHg. Intrathecal morphine, and IV meloxicam and edrophonium were injected before recovery. Time to loss of palpebral reflex (TLPR) upon induction, cardiorespiratory variables, time at first swallowing and other movement, tracheal extubation, vocalisation, spontaneous head lifting (>1 minute), reunion with the ewe, and the number of MAP treatments were recorded. Statistical analysis utilised anova, Mann-Whitney, t-test or Pearson's correlation test as relevant. p < 0.05 was considered significant. End-tidal carbon dioxide (mean ± SD) was significantly lower in group S (5.5 ± 0.6 kPa) than in group I (5.8 ± 0.5 kPa) while MAP (70 ± 11 mmHg) and diastolic arterial blood pressure (60 ± 11 mmHg) were higher in group S than in group I (65 ± 12 and 54 ± 11 mmHg, respectively). No differences were found with TLPR and MAP treatments. Time (median, range) from end of anaesthesia to ewe-lamb reunion was briefer (p = 0.018) in group S (48, 20-63 minutes). Isoflurane and sevoflurane are both suitable for maintaining general anaesthesia in lambs although sevoflurane, as used in this study, allows a more rapid reunion with the ewe. The principal advantage of sevoflurane over isoflurane during prolonged anaesthesia in lambs is a more rapid recovery.
    Veterinary Anaesthesia and Analgesia 04/2012; 39(5):495-502. DOI:10.1111/j.1467-2995.2012.00718.x · 1.78 Impact Factor
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    ABSTRACT: To determine the effects of age, sevoflurane and isoflurane on atracurium-induced neuromuscular blockade in 3-16 week-old lambs. Prospective randomized experimental trial. Twenty-six Scottish blackface ewe-lambs were anaesthetized for spinal surgery when either 3-6 (mean age 4.6 weeks; n = 18) or 12-16 weeks (mean age 13.7 weeks; n = 15) of age; seven animals were anaesthetized at both ages. After intramuscular injection of medetomidine (10 μg kg(-1)) anaesthesia was induced in the younger lambs either with isoflurane or sevoflurane in oxygen delivered by mask, and in the older lambs with ketamine (4 mg kg(-1)), and midazolam (0.2 mg kg(-1) ) administered intravenously (IV). In both groups anaesthesia was maintained with fixed end-tidal concentrations of either sevoflurane (2.8%) or isoflurane (1.8%) delivered in oxygen. Before surgery meloxicam (0.6 mg kg(-1)), morphine (0.5 mg kg(-1)) and ketamine (1 mg kg(-1) followed by 10 μg kg(-1) minute(-1) ) were administered IV. The lungs were ventilated mechanically to maintain normocapnia. Neuromuscular block was achieved with a loading dose (LD) of atracurium (0.5 mg kg(-1) IV). The peroneal nerve was stimulated (train-of-four every 12 seconds). Evoked responses in the digital extensor muscles were evaluated by palpation and observation. Maintenance doses (MD) of atracurium (0.17 mg kg(-1) IV) were administered when the first twitch (T1) returned. The onset and duration of LD action (T1 absent) and the duration of MD were recorded. Data were analysed using Student's t test, Mann-Whitney U test, repeated-measures anova, Wilcoxon's matched pairs test or Pearson correlation coefficient as relevant (p < 0.05). Onset of LD action developed significantly (p < 0.05) more rapidly in isoflurane compared with sevoflurane-anaesthetized lambs (55 ± 18 cf. 80 ± 37 seconds). Duration of action of LDs and MDs was longer (p < 0.05) in lambs aged 12-16 than 3-6 weeks (33 ± 5.4 cf. 25 ± 6.4 and 26 ± 4.2 cf. 18 ± 5.5 minutes) but were independent of the anaesthetic used. The effect of atracurium is age-dependent in lambs being prolonged in older animals. The onset of neuromuscular blockade is more rapid in isoflurane compared with sevoflurane-anaesthetized lambs.
    Veterinary Anaesthesia and Analgesia 03/2012; 39(3):256-65. DOI:10.1111/j.1467-2995.2011.00705.x · 1.78 Impact Factor