Comparison between the analgesic effects of morphine and tramadol delivered epidurally in cats receiving a standardized noxious stimulation

This study compared the analgesic effects of epidural tramadol versus morphine in six healthy cats. Under general anesthesia, each cat received an epidural injection of saline 0.22 ml/kg (control treatment, CT), tramadol 1 mg/kg (tramadol treatment, TT), or morphine 0.1 mg/kg (morphine treatment, MT). After cats had recovered from anesthesia a simple descriptive scale (SDS), visual analog scale (VAS) and physiological parameters (respiratory and heart rate) were used to assess analgesia level to a noxious stimulus (base of the tail skin fold clamping) at 1, 2, 3, 4, 6, 8, 10, and 12 h post-epidural. Group TT had a higher SDS and VAS score when compared to MT at 8, 10 and 12 h post-epidural. CT had higher SDS and VAS score at all time points when compared to TT and MT. In conclusion both morphine and tramadol provided analgesia in this model for the first 6 h; with epidural morphine resulting in longer lasting analgesia when compared to tramadol.