Glomerular filtration rate after tramadol, parecoxib and pindolol following anaesthesia and analgesia in comparison with morphine in dogs

To compare the effects of morphine, parecoxib, tramadol and a combination of parecoxib, tramadol and pindolol on nociceptive thresholds in awake animals and their effect on glomerular filtration rate (GFR) in dogs subjected to 30 minutes of anesthesia. Eight adult mixed breed experimental dogs. Randomized, controlled trial. Dogs received 0.05 mg kg(-1) acepromazine subcutaneously (SC) as anaesthetic pre-medication. Thirty to sixty minutes later, they received either tramadol 3 mg kg(-1) intravenously, (IV), parecoxib (1 mg kg(-1) IV), a combination of tramadol 3 mg kg(-1) (IV), parecoxib 1 mg kg(-1) (IV) and pindolol 5 mu g kg(-1) (SC), morphine (0.1 mg kg(-1) (IV) or 0.9% saline (2 mL). Anaesthesia was then induced with IV propofol to effect (2.9 +/- 0.8 mg kg(-1)) and maintained with halothane in oxygen for 30 minutes. Systolic arterial blood pressure was maintained above 90 mmHg with IV fluids and by adjusting the inspired halothane concentration. Post-treatment nociceptive thresholds to mechanical stimuli, expressed as percent of pre-treatment values, were compared between the treatments to assess the analgesic efficacy of the drugs. Plasma iohexol clearance (ICL), a measure of GFR, was estimated both before and 24 hours after induction of anaesthesia to study the drugs' effects on renal perfusion. Nociceptive threshold and GFR data were compared using mixed model analysis in sas((R))9.1. Both tramadol and parecoxib produced similar analgesia, which was less than that of morphine. Their combination with pindolol produced analgesia comparable with morphine. None of the test drugs, either alone or in combination, reduced GFR. Tramadol and parecoxib (either alone or in combination) can increase nociceptive thresholds in awake dogs and have minimal effects on renal perfusion in normotensive dogs subjected to anaesthesia.