Evaluation of Tear Production as Measured by Schirmer Test I in Dogs after Acepromazine and Acepromazine–Methadone Premedication

Abstract

The purpose of the current study was to investigate the effects of two commonly used sedation protocols in dogs, acepromazine (ACP) and acepromazine–methadone (ACP–MET) combination, on tear production measured by the Schirmer Tear Test (STT) 1. We hypothesized that both sedation protocols cause a reduction in canine tear production for a variable time. Fifteen client-owned dogs were recruited for the study. Each dog was subjected to sedation twice, 2–3 weeks apart, and they were randomly allocated to one of two groups receiving ACP (0.015 mg kg−1) or ACP–MET (0.010 mg kg−1 and 0.2 mg kg−1) intramuscularly. In both eyes, tear production was measured 15 min before sedation (T0) and 20 min (T20 m), 40 min (T40 m), 1 h (T1), 2 h (T2), 4 h (T4) and 8 h (T8), after drug administration. Two-way repeated measures ANOVA, followed by the Bonferroni post hoc test (p < 0.05), showed a significant effect of time (p < 0.0001) and treatment (p < 0.0001). A significant decrease in tear production at T20 m, T40 m, T1 and T2 compared to T0 was observed in the ACP experimental protocol, while in the ACP + MET protocol, this reduction persisted until T8. Comparing the two experimental protocols, no statistically significant differences were observed at T0 or T20 m, and STT 1 values were statistically lower in the ACP + MET than the ACP protocol at the other data points. In the ACP + MET group, at T40 m, 100% of dogs showed STT 1 readings lower than 15 mm/min. This finding is clinically relevant as it can predispose dogs to corneal injuries. The major reduction in tear production due to the ACP + MET protocol proves the need for adequate corneal hydration, particularly to discourage its use in animals with altered tear production. The data obtained provide important information helping clinicians to better manage the drug’s effects on tear production.

Retrospective investigation of perioperative risk factors for immediate postoperative corneal erosions in dogs undergoing phacoemulsification

“…Reduced aqueous tear production is a known effect of sedation and following general anesthesia in the dog. [98][99][100] Given the ubiquitous nature of these effects in canine studies, the relatively low incidence of IPCE in our cohort does not support a direct association between reduced postoperative STT and the development of immediate postoperative erosion. Evaporative forms of dry eye such as meibomian gland dysfunction are also implicated as risk factors for postoperative corneal erosions in human patients.…”

“…As expected, STT was not routinely performed or noted in medical records within 24 h of surgery. Reduced aqueous tear production is a known effect of sedation and following general anesthesia in the dog 98–100 . Given the ubiquitous nature of these effects in canine studies, the relatively low incidence of IPCE in our cohort does not support a direct association between reduced postoperative STT and the development of immediate postoperative erosion.…”

Bilateral corneal ulceration in a cat after general anaesthesia

“…Opioid drugs have been shown to contribute to prolonged reduction of tear production in dogs, potentially impairing post-anaesthetic healing of corneal abrasions, even though their contribution compared to other factors has not been well determined. 4,25,27,32 More specifically, butorphanol showed synergistic reduction of tear production when administered with alpha-2 agonist sedatives in dogs. 27 It remains unclear if the butorphanol administered once in this cat could have played a significant role in the prolonged eye dryness observed.…”

“…Another relevant risk factor seems to be the drugs used for general anaesthesia, 22,23,27 while there is no knowledge on how the choice of these drugs influences the outcome. Opioid drugs have been shown to contribute to prolonged reduction of tear production in dogs, potentially impairing post‐anaesthetic healing of corneal abrasions, even though their contribution compared to other factors has not been well determined 4,25,27,32 . More specifically, butorphanol showed synergistic reduction of tear production when administered with alpha‐2 agonist sedatives in dogs 27 .…”