Evaluation of butorphanol and fentanyl in preanaesthetic protocols to propofol-isoflurane anaesthesia in adult and geriatric canine patients

Two anaesthetic protocols were evaluated in four groups (A₁, A₂, B₁ and B₂) of six canine patients each from two different age groups (A₁ and A₂: < 6 yr; B₁ and B₂: > 8 yr) presented for various surgical procedures. Preanaesthetic combination of glycopyrrolate (0.01 mg/kg b.wt), dexmedetomidine (5 μg/kg b.wt) and butorphanol (0.1 mg/kg b.wt) was administered intramuscularly in animals of groups A₁ and B₁. In Animals of groups A₂ and B₂, a mixture of glycopyrrolate (0.01 mg/kg b.wt), dexmedetomidine (5 μg/kg b.wt) and fentanyl (4 μg/kg b.wt) was administered, intramuscularly. Anaesthesia was induced with propofol (10 mg/mL) 15 min after administration of preanaesthetics. Maintenance of anaesthesia was done with isoflurane using rebreathing system of anaesthesia with a oxygen flow rate of 30 mL/kg/min in all the four groups. Preanaesthetic combination used in groups A₁ and B₁ produced better sedation than in A₂ and B₂ groups. The required doses of propofol (mg/kg) to achieve general anaesthesia in A₁, A₂, B₁ and B₂ groups were 2.11±0.40, 3.13±0.69, 1.47±0.23 and 1.90±0.27, respectively. No significant difference in the induction dose of propofol was noted among the groups. The anaesthesia could be maintained by setting the isoflurane vaporizer between 1.5% and 3% in A₁ group, 2% and 3.5% in A₂ group, 1% and 2% in B₁ group and 1% and 3% in B₂ group, respectively. Preanaesthetic combination of glycopyrrolate, dexmedetomidine and butorphanol (GDB) was found better in comparison to the combination of glycopyrrolate, dexmedetomidine, fentanyl (GDF) in terms of the sedation quality, recovery time, dose sparing action on the induction and maintenance agents used, better maintenance of the cardiopulmonary and haemodynamics in both adult healthy and geriatric canine patients. All the four preanaesthetic combinations were comparable in terms of the cardio-respiratory and haemodynamic stability and did not produce any serious alterations on these parameters.