The effects of alfaxalone, alone or with butorphanol, on the ultrasonographic appearance of the feline spleen.

Objective: To investigate the sonographic effects of alfaxalone and butorphanol alone and in combination on feline splenic size, shape, margins, echogenicity, echotexture, and blood flow. Our hypothesis was that alfaxalone alone and in combination would be associated with an increase in splenic size and blood flow and a nonhomogenous echotexture.

Methods: This was a randomized, prospective crossover study. 8 healthy adult cats were all injected IM with each of the following protocols in a randomized fashion, with a minimum of 7 days of washout between each protocol-alfaxalone 2 mg/kg, butorphanol 0.2 mg/kg, and the 2 in combination. Splenic ultrasounds were performed before drug administration, then every 15 minutes for 1 hour subsequently. Ultrasound images were interpreted by 2 board-certified radiologists. Heart rate, respiratory rate, and feline multiparametric sedation scores (FMSS) were also recorded. Splenic appearance, heart rate, respiratory rate, and FMSS were compared to baseline.

Results: There were no significant changes detected in splenic margins, shape, echogenicity, echotexture, or blood flow compared to baseline for any of the protocols. An increase in splenic size occurred for all protocols, with no significant difference between them. Both protocols containing alfaxalone caused a significant increase in FMSS; butorphanol alone did not.

Conclusions: Alfaxalone did not affect splenic margins, echotexture, echogenicity, or blood flow; however, a mild and transient increase in splenic size was noted.

Clinical relevance: Alfaxalone in combination with butorphanol provided the best sedation and can be used in the sedation of healthy cats for splenic ultrasound without significant changes to splenic appearance. Splenomegaly may occur but is unlikely to be of clinical significance.