Thirteen client owned dogs presented for various surgical procedures were divided randomly into group I (Butorphanol-Diazepam group, n=7) and II (Butorphanol-Midazolam group, n=6). The animals were kept off feed for 12 hours before surgery and water was withheld for 6 hours. The dogs were pre-medicated with atropine sulphate (@ 0.04 mg/kg body wt.) followed by butorphanol (@ 0.02 mg/kg body wt. IV) after 5 minutes followed by an immediate injection of diazepam (@ 0.5 mg/kg body wt. IV in group I) or midazolam (@ 0.2 mg/kg in group II). Induction was made after 5 min of the preanaesthetic medication by propofol @ 4–8 mg/kg IV bolus "till effect". Maintenance was done by repeated intravenous bolus (RIB) injection of propofol (Table 1).

The dose of propofol required for induction of anaesthesia was calculated in milligram per kilogram (mg/Kg) as well as the maintenance dose was calculated per animal in milligram per kilogram per minute (mg/kg/min). The time from which maintenance of anaesthesia was stopped to the re-appearance of pedal reflex was recorded as recovery time and was noted.

Physiological parameters like rectal temperature (RT-°C), pulse rate (beats/min), respiratory rate (RR-breaths/min), systolic blood pressure (SBP-mm of Hg), diastolic blood pressure (DBP-mm of Hg), mean arterial pressure (MAP-mm of Hg) and arterial oxygen saturation (SpO₂%) were recorded by multipara monitor (Vital signs monitor, BM5 VET, Bionet Company Ltd, Korea) after induction of anaesthesia with propofol and thereafter at regular 15 minute time interval or till the end of the surgery.

Venous blood samples were collected for hematobiochemical estimation, after induction of anaesthesia and thereafter, at every 15 minute interval, till end of the surgery for estimation of haemoglobin (g/L) DLC (%), TLC (x10^-9/L) and PCV (L/L) using automatic haemato-analyzer. Estimation of blood glucose (mg/dL) was estimated by using glucometer, whereas, plasma urea nitrogen (mmol/L) and creatinine (nmol/L) was estimated using standard diagnostic kits using semi-automatic biochemical analyser.

Analysis of variance (ANOVA) and Duncan’s multiple range tests (DMRT) were used to compare the means at different intervals between two groups. Paired “t” test was used to compare the mean values at different levels with their respective base value in each group.

In group I (diazepam-butorphanol) the mean and S.E. dose of propofol for induction (Fig. 1) came as 3.58 ± 0.29 mg/ kg and was non-significantly (P≤0.05) lower than in group II (midazolam-butorphanol) which was calculated as 4.02 ± 0.10 mg/kg. Likewise, the maintenance dose of propofol (Fig. 2) was also non-significantly (P≤0.05) higher than in group II (0.27 ± 0.03 mg/kg/min.) than in group I (0.18 ± 0.03 mg/kg/min.). The recovery time of group I was non-significantly (P≤0.05) higher than that of group II (Fig. 3).

A significant reduction in the dose of propofol required for tracheal intubation (post induction of anaesthesia) was reported in diazepam and midazolam premedicated cats (Rebecca and Kate, 2015). Sano et al., 2003 also reported a considerable reduction in the induction dose of propofol administered with butorphanol and benzodiazepine as preanaesthetic drugs, similar to our findings.

The rectal temperature slowly and gradually decreased in both the groups after induction of the anaesthesia. Post anaesthetic hypothermia observed may be the result of peripheral vasodilatation, reduced BMR, inhibition of skeletal muscle movement and depression of the thermoregulatory centre due to interactive actions of different anaesthetic agents as well as increased heat dissipation and heat loss through respiratory system (Khandekar et al., 2015). The pulse rate increased in both the groups but the increase was gradual with no difference between the groups at different time intervals. An increase in heart rate may be due to the effect of the propofol as also reported in earlier references (Surbhi et al., 2010; Suthar et al., 2018). Respiratory rate also showed a decreasing trend in both the groups with a more significant decrease in group II, although no significant difference was observed between the two groups. The respiratory depression observed might be due to the combined effect of butorphanol (Kuo et al., 2004), and propofol (Mutoh et al., 1997). Mean arterial pressure values increased non-significantly in both the groups with no difference between group I and II. However, a decrease in MAP was recorded in some earlier studies (Suthar et al., 2018). Oxygen saturation of haemoglobin (SpO₂) values remained within the normal range at different time intervals post induction in both the groups. Post induction an immediate endotracheal intubation was done. A decrease in SpO₂ was reported by Surbhi et al., 2010; however, no such reduction in SpO₂ has been reported in other studies (Suthar et al., 2018). The mean values of different physiological parameters have been summarized in table 2.

Haemoglobin and PCV reduced non-significantly in both the groups, although all other haematological parameters exhibited a non-significant difference in mean values when compared at different time intervals within and between the groups. The value of glucose increased slightly in the group-II. Anaesthetic and surgical stress can lead to an increased secretion of adrenocortical hormone (ACTH) and glucocorticoids which contribute for rise in blood glucose level (Dikshit and Prasad, 1971; Mirakhur et al., 1984). The biochemical parameters also showed a nonsignificant difference at different time intervals within and between the groups.

The present study indicated that both preanaesthetic combinations of Atropine-Butorphanol-Diazepam (A-B-D) and Atropine-Butorphanol-Midazolam (A-B-M) showed non-significant and transient alterations in different clinico-physiological and haemato-biochemical parameters with a marked dose sparing action on the propofol required for induction and maintenance in dogs; with group I (A-B-D) slightly better than group II (A-B-M).