Digital cryotherapy in horses: arterial doppler ultrasonography

Author(s)

Gabriela Gomes Rivera

• Document type: Master's Dissertation
• Press: Jaboticabal. 2017-06-08.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2017-04-28
• Advisor: Paulo Aléscio Canola

Abstract

Cryotherapy has been extensile used as adjuvant treatment in cases of equine laminites, despite scientific evidence to sustain its efficacy and lack of consensus regarding its efficiency, even on human medicine. Therefore, we assessed the effects of cryotherapy over digital perfusion of horses. To that purpose, eight healthy adult horses, with no previous history of laminitis, were used. The local and systemic effects of cryotherapy were assessed by spectral Doppler ultrasound and mean arterial pressure acquisition of the left thoracic limb (treated limb) and right thoracic limb (no treated limb). Data was recorded previously (baseline) and at 10- minute intervals in between evaluations following immersion of the left thoracic limb into a cooled solution (4 oC), for 60 minutes. A multivariate analysis was used for statistical purposes. Digital artery diameter, area, systolic and mean arterial flow were intimately correlated (process 1) and were responsible for 37.2% of the variability observed on arterial parameters. Twenty-six percent of the variability were associated to the systolic, diastolic and mean systemic arterial pressure (process 2), 21% to systolic and mean blood velocity (process 3) and 12% was correspondent to diastolic velocity (process 4). No statistical significance was observed for treatment (p > 0.1), regarding all processes. There was statistical difference between treated and nontreated limbs regarding Process 3 at T50 (t-test, p ≤ 0.05). Similarly, regarding treated limb, a statistical difference was observed between T20 and T30, T20 and T40, T30 and T60, and T40 and T60 (Fisher test, p ≤ 0.1). Process 3 showed a 3rd degree effect (p < 0.05), which, incidentally, no equation was found to elucidate the untreated limb. Furthermore, a discreet (- 0.32) negative product Pearson correlation (p ≤ 0.1) was observed between products 1 and 3 (p =0,02) for the treated limb which was more pronounced (-0.63) at T10 (p = 0.09). Results suggest local action of the cooled water most promptly on the treated limb. Process 3 data on this appendix responded differently throughout treatment when compared to the untreated limb. Moreover, although there was no difference in between processes (p > 0.05), mainly between processes 1 and 2, it is possible to indicate there was physiological implications associated to the cryotherapy significant because of the high variability observed for the processes. Mean variations observed for the treated limb strongly suggest activation of the sympathetic nervous system in response to treatment. Activation of the sympathetic nervous system was likely responsible for reduction on variables of process 1 and increase in pressure values of process 2 for the treat limb. Response of treated limb to treatment throughout time, investigated by Pearson‟s product correlation, suggests activation of local neuronal control mechanisms, in order to maintain local flow. This response was more significant at T10. It is believed powerful protection mechanisms present within the hoof may have been activated and its action most likely minimized local and systemic effects of cryotherapy over digital palmar artery hemodynamics. It is suggested that the local action of the cooled water on digital microcirculation may interfere with the local hemodynamics of the digital palm arteries. (AU)

• FAPESP's process: 16/00667-3 - Assessment of the effects of cryotherapy over digital perfusion of horses
• Grantee: Gabriela Gomes Rivera
• Support Opportunities: Scholarships in Brazil - Master