A Comparison of the Intrarectal and Intramuscular Effects of a Dexmedetomidine, Ketamine and Midazolam Mixture on Tear Production in Cats: A Randomized Controlled Trial

Abstract

Cats are often easily stressed and uncooperative. The use of sedative agents in the feline species is widely used to perform even minor clinical and diagnostic procedures. The aim of this study is to assess the impact on tear film production of the intrarectal route (IR) administration of a mixture of dexmedetomidine, ketamine and midazolam in comparison with the intramuscular (IM) one. A group of twenty cats were involved in a randomized and blinded clinical trial. A clinical and ophthalmological examination was conducted on the cats. The IR group received dexmedetomidine 0.003 mg kg^-1, ketamine 4 mg kg^-1 and midazolam 0.4 mg kg^-1; the IM group received dexmedetomidine 0.003 mg kg^-1, ketamine 2 mg kg^-1 and midazolam 0.2 mg kg^-1. A Shirmer tear test I (STT- I) was conducted 1 h before sedation and 2', 10', 20', 30', 40', and 80' post drug administration. The reaction to STT-I administration was also evaluated. The IM group has a lower mean tear production than the IR group for all time points evaluated. Cats in the IM group showed less reaction to STT-I administration. This study may suggest that the effect of sedative agents administered by the IR route has a lower incidence on tear production than the IM one. The use of eye lubricant is recommended in any case.

Keywords: cats; dexmedetomidine; intramuscular route; intrarectal route; ketamine; midazolam; sedation; tear production.

Figure 1

Tear flow in the right eye over time during sedation in the two groups. The first histogram refers to the IM group, the second to the IR group. On the y-axis line, tear secretion is expressed as mm/min. On the x-axis line, time is expressed as T0 (1 h before drug administration), T1 (2′), T2 (10′), T3 (20′), T4 (30′), T5 (40′) and T6 (80′). Tear production is reported as media and standard deviation. In the IR group, tear film production is higher than in the IM group.