Abstract
Objective
Analgesic regimes were compared in pregnant ewes after laparotomy by measuring thermal
(TT) and mechanical (MT) nociceptive thresholds.
Study design
Prospective randomised experimental study.
Animals
Pregnant ewes at 121 days gestation underwent laparotomy as part of another research
project.
Methods
Thermal and mechanical thresholds were measured before, and 2, 6, 24 and 48 hours
after surgery. Thermal stimuli were delivered to the lateral aspect of the metatarsus
via a skin-mounted probe, and mechanical stimuli to the contralateral site via a pneumatically
driven 1.5 mm diameter pin. Each test was performed five times, alternating thermal
and mechanical stimuli, with ten minutes between thermal stimuli. At the end of surgery
ewes received either: 75 μg hour−1 transdermal fentanyl patch (medial thigh) (group FP) (n = 8), or 3 μg kg−1hour−1 intra-peritoneal medetomidine via an osmotic pump (group IPM) (n = 8) inserted immediately prior to closure. Data were analysed using the Kruskal–Wallis
RS Test (p < 0.05). Once a significant effect was identified, pairwise comparisons were performed
using paired Wilcoxon RS tests. To compensate for multiple hypotheses testing, p < 0.005 was considered significant.
Results
Prior to surgery mean ± SD TT was 56.1 ± 5.0 °C (FP) and 55.6 ± 5.0 °C (IPM); MT was
5.3 ± 2.6 N (FP) and 8.0 ± 5.0 N (IPM). In FP there was no significant change in either
TT or MT over time. In IPM there was no significant change in MT over time but TT
increased at two hours to 59.2 ± 3.0 °C (p = 0.003). Skin temperature (ST) ranged from 33.0 to 34.7 °C and did not change over
time. There were no significant differences between groups in TT, MT or ST.
Conclusions and clinical relevance
Administration of intra-peritoneal medetomidine (3 μg kg−1hour−1) by an osmotic pump increases the thermal nociceptive threshold in the immediate
post operative period in pregnant sheep, suggesting that this agent may have a role
in providing post-operative analgesia.
Keywords
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Article info
Publication history
Accepted:
April 3,
2013
Received:
February 4,
2013
Identification
Copyright
© 2014 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Inc. All rights reserved.
