Different rates of tramadol infusion for peri and postoperative analgesia in dogs undergoing orthopedic surgery

ABSTRACT The study aimed to determine the continuous rate infusion of tramadol associated with peri- and postoperative analgesia for orthopedic surgeries in dogs, as well as cardiorespiratory and adverse effects. Thirty dogs aged 4.2±1.2 years and weighing 15.1±0.9kg were enrolled in the study, premedicated intramuscularly with acepromazine (0.04mg kg-1) and tramadol (2mg kg-1); anesthesia was induced with propofol and maintained with isoflurane in oxygen. Three infusion rates were compared, comprising three experimental groups: G2: 2.0mg kg-1 h-1; G2.5: 2.5mg kg-1 h-1; and G3: 3.0mg kg-1 h-1. Surgery was initiated 15 minutes following the start of tramadol infusion. During anesthesia, animals were monitored in predefined time points: immediately after tracheal intubation and start of inhalation anesthesia (T0); surgical incision (TSI); final suture (TFS) and end of tramadol infusion (TEI), which was maintained for at least 120 minutes and prolonged according to the duration of surgery. Postoperative analgesia was evaluated through an interval pain scoring scale and the Melbourne pain scale. The mean time of tramadol infusion was greater than 120 minutes in all groups and no differences were found among them (141±27 minutes in G2, 137±27 minutes in G2.5 and 137±30 minutes in G3). Perioperative analgesia was regarded as short and did not correlate with infusion rates. Tramadol infusion provided adequate analgesia with cardiorespiratory stability Analgesia was not dose-dependent, however, and residual postoperative effects were short-lasting, which warrants proper postoperative analgesia following tramadol infusion. Additional studies are required using higher infusion rates and standardized nociceptive stimulation in order to determine how doses influence tramadol analgesia and whe therthereis a limit to its effect in dogs.