Objective: To determine the effects of three rates of dexmedetomidine (DMED) constant rate infusion (CRI) on overall tissue perfusion, isoflurane (ISO) requirements, haemodynamics and quality of recovery in canine surgical patients.
Study design: Prospective, randomized, blinded clinical study.
Animals: Client-owned dogs presented for soft tissue or orthopaedic surgery.
Methods: Following intravenous (IV) pre-medication with DMED (5 microg kg(-1)) and buprenorphine (10 microg kg(-1)) and propofol induction, anaesthesia was maintained with ISO in oxygen/air supplemented with a DMED CRI (1, 2 or 3 microg kg(-1) hour(-1); groups 1, 2 and 3, respectively). Ventilation was controlled in all animals using intermittent positive pressure ventilation (IPPV). Monitoring included end-tidal (ET) gases, ECG, arterial blood pressure, body temperature and sequential arterial blood gas and lactate measurements. Quality of recovery was scored after intramuscular (IM) administration of atipamezole (ATI) (12.5 microg kg(-1)). Immediate post-operative analgesia was provided with carprofen and/or buprenorphine. An analysis of variance was conducted for repeated measurements obtained during 80 minutes after first incision. Categorical data were evaluated with Chi-square analyses.
Results: Arterial blood pressure remained stable and within clinically acceptable limits. Mean heart rate in group 2 was significantly lower than in group 1. The incidence of 2nd degree AV block type II was significantly higher in group 3. Mean arterial lactate concentrations remained below 2 mmol/L in all groups during the study, with a significant increase occurring during recovery compared with surgery for group 3. Mean e'ISO% was similar and <1% in all groups. Complete recovery from anaesthesia was achieved after ATI administration and was of good quality in all but three animals.
Conclusions and clinical relevance: Dexmedetomidine CRI is a reliable and valuable adjunct to ISO anaesthesia in maintaining surgical anaesthesia in ASA I-II dogs. Data reported indicate adequate overall tissue perfusion and a low ISO requirement while enabling a smooth and rapid recovery following ATI. The DMED CRI of 1 microg kg(-1) hour(-1) following a loading dose of 5 microg kg(-1) produced the most favourable results.