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Frontiers in veterinary science2024; 11; 1412755; doi: 10.3389/fvets.2024.1412755

Effect of nose twitching on the pupillary dilation in awake and anesthetized horses.

Abstract: Pupillometry is used in humans to monitor pain, nociception and analgesia. This single-center, non-randomized, non-blinded intervention trial, evaluated the effect of nose twitching on the pupil size in awake, sedated, and anesthetized horses. Pupil height (H) and length (L) were measured before (Be) and after (Af) nose twitching in fourteen non-painful adult awake horses (T0). The percentage of variation (PSV) was calculated (PSVTn = [(TnAf-TnBe)/TnBe]*100). Measurements were repeated (Tn) after acepromazine (0.04 mg kg IV) (T1), romifidine (0.04 mg kg IV) (T2), morphine (0.1 mg kg IV) (T3), after anesthesia induction with diazepam (0.05 mg kg IV) and ketamine (2.2 mg kg IV), at the time the horse was placed on the operating table (T4) and when the expiratory fraction of sevoflurane was 2% (T5). HAf vs. HBe, LAf vs. LBe as well as PSVH vs. PSVL at each time were compared with a Mann-Whitney Wilcoxon test. The PSVL and PSVH, as well as HBe and LBe over time were compared with the Skillings-Mack test followed by a Wilcoxon test for paired data to make pairwise comparisons (Tn + 1 vs. Tn). In non-sedated horses (T0), the application of the nose twitch induced a significant increase in pupil length (LT0Be: 17.09 [16.05; 19.67] mm versus LT0Af: 19.52 [18.74; 21.40]) mm ( = 0.004). Thirty minutes after acepromazine administration (T1), nose twitching induced a significant increase in pupil length (LT1Be: 16.45 [14.80; 18.66] mm versus LT1Af 18.31 [17.20; 20.52] mm) ( = 0.016) and height (HT1Be: 8.44 [5.68; 12.04] mm versus HT1Af: 11.09 [7.97; 14.3] mm) ( < 0.001). PSVHT1 was significantly greater than PSVLT1 ( = 0.025). PSVH was higher at T1 than at T0 ( = 0.04). It was also significantly higher at T1 than at T2 ( < 0.001). Romifidine induced mydriasis (HT2Be 16.95 [14.73; 18.77] mm versus HT1Be 8.44 [5.68; 12.04] mm) ( < 0,001) (LT2Be 19.66 [18.45; 20.41] mm versus LT1Be 16.45 [14.80; 18.66] mm) ( < 0.001). The results suggest that nose twitching induced a pupillary dilation in the awake horse. This effect was potentiated after the administration of acepromazine but disappeared after the administration of romifidine.
Copyright © 2024 Mascaró Triedo, Karar, Abunemeh and Portier.
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Publication Date: 2024-07-04 PubMed ID: 39036796PubMed Central: PMC11258756DOI: 10.3389/fvets.2024.1412755Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study explores how nose twitching impacts the size of a horse’s pupil when awake, sedated, and anesthetized. It revealed that nose twitching leads to the dilation of the pupil in awake horses, an effect enhanced by the administration of acepromazine, but neutralized by romifidine.

Study Design and Procedures

  • The researchers undertook a non-randomized, single-center intervention trial to assess the impact of nose twitching on the size of a horse’s pupil. This experiment was conducted on 14 adult non-painful horses both when awake and under different states of sedation and anesthesia.
  • Measurements of the pupil’s height (H) and length (L) were taken before (Be) and after (Af) the application of the nose twitch at different points in time (Tn).
  • The Percentage of Variation (PSV) between the before and after measurements was then calculated (PSVTn = [(TnAf-TnBe)/TnBe]*100).
  • The same measurements were taken again after administering different agents namely acepromazine, romifidine, morphine, diazepam, and ketamine; and at specific intervals such as upon laying the horse on the operating table and when the expiratory fraction of anesthetic sevoflurane was at 2%.
  • The variations between Ha and Hb, La and Lb, and between PSVH and PSVL at each timestamp were compared using a Mann-Whitney Wilcoxon Test.
  • Comparisons of PSVL, PSVH as well as HBe and LBe over time were conducted with the Skillings-Mack Test. This was followed by a Wilcoxon Test for paired data to make pair-wise comparisons (Tn + 1 vs. Tn).

Observations and Findings

  • In non-sedated horses, the application of the nose twitch resulted in a significant increase in pupil length. This effect was also observed after the administration of the sedative, acepromazine.
  • There was also a significant increase in pupil height 30 minutes after applying acepromazine.
  • Hence, the study concluded that nose twitching leads to increased dilation of pupils in awake horses. The effect is more pronounced after administering acepromazine but disappears after introducing romifidine.

Implications of the Study

  • The study’s outcomes suggest the potential of using pupillometry (measurement of pupils) as an indicator of nociception (sensory nervous system response to harmful stimuli), similar to how it’s used in human medicine. The significant dilation of pupils after a nose twitch might indicate a pain response.
  • The different drugs’ effects on this response could also lead to further studies on assessing pain and developing better pain management strategies in horses under sedation or anesthesia.

Cite This Article

APA
Mascaró Triedo CE, Karar S, Abunemeh M, Portier K. (2024). Effect of nose twitching on the pupillary dilation in awake and anesthetized horses. Front Vet Sci, 11, 1412755. https://doi.org/10.3389/fvets.2024.1412755

Publication

Frontiers in veterinary science
ISSN: 2297-1769
NlmUniqueID: 101666658
Country: Switzerland
Language: English
Volume: 11
Pages: 1412755
PII: 1412755

Researcher Affiliations

Mascaró Triedo, Carlota Emilia
  • VetAgro Sup, CREFAC, Université de Lyon, Marcy l'Etoile, France.
Karar, Sahra
  • VetAgro Sup, CREFAC, Université de Lyon, Marcy l'Etoile, France.
Abunemeh, Maha
  • VetAgro Sup, CREFAC, Université de Lyon, Marcy l'Etoile, France.
Portier, Karine
  • VetAgro Sup, CREFAC, Université de Lyon, Marcy l'Etoile, France.
  • Centre de Recherche en Neurosciences de Lyon, INSERM, CRNL U1028 UMR5292, Trajectoire, Université Claude Bernard Lyon 1, Bron, France.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

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Citations

This article has been cited 1 times.
  1. Roth LSV, McGreevy P. Horse vision through two lenses: Tinbergen's Four Questions and the Five Domains. Front Vet Sci 2025;12:1647911.
    doi: 10.3389/fvets.2025.1647911pubmed: 40895790google scholar: lookup
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