Clinical parameters
Time for sedation
The mean±SD values of time for sedation for all the three groups were recorded and depicted in the Table 1.
The differences in sedation time among all the groups-T, P and M were statistically non-significant (P>0.05). The animals in all the groups did not show any sedation within the time period after pre-emptive analgesia to induction of anaesthesia (within 10 min). The time for sedation of animals in all the with groups-T, P and M was not recorded since there was no sedation. Many conflicting evidences are there with respect to sedative effect of tramadol in dogs. In one report, a dose-dependent sedative effect was noticed in dogs administered with tramadol (1, 2, or 4 mg/kg body weight, IV)
(McMillan et al., 2008). The inefficacy of opioids in enhancing the degree of sedation in dogs may be related to its pharmacokinetic and pharmacodynamic characteristics
(Monteiro et al., 2016).
Quality of sedation
The mean±SD values of Quality for sedation for all the three groups were recorded and depicted in the Table 1.
The differences in quality of sedation among groups-T, P and M were statistically non-significant (P>0.05). The animals in all the groups did not show any sedation within the time period after pre-emptive analgesia to induction of anaesthesia (within 10 min). The scoring of quality of sedation in animals with groups-T, P and M were recorded as 0.00±0.00 (score 0).
Time for induction
The mean±SD values of time for induction for all the three groups were recorded and depicted in the Table 1 and Fig 1.
The time for induction was significantly (P<0.05) higher in group-M as compared to group-T and -P. Non-significant (P>0.05) difference was noticed between groups-T and P. The time for induction of animals with propofol in group-T, P and M were recorded as 43.50±7.19, 48.67±4.27 and 57.83±9.60 seconds, respectively. Animals of group-T showed lowest induction time (43.50±7.19 seconds), whereas animals of group-P took a bit longer period for induction (48.67±4.27 seconds) and animals of group-M showed highest induction time (57.83±9.60 seconds).
Quality of induction
The mean±SD values of Quality for induction for all the three groups were recorded and depicted in the Table 1 and Fig 1.
The differences in quality of induction among all the three groups were statistically non-significant (P>0.05). The scoring of quality of induction of animals with propofol in groups-T, P and M were recorded as 0.17±0.40, 0.50±0.54 and 0.83±0.40, respectively. Animals in all the three groups showed smooth transition with no paddling (score 0) to occasional, slow paddling (score 1) movements while induction stage. Lower induction time noticed in group-T and group-P might be due to synergistic effect of opioids and propofol
(Anandmay et al., 2016).
Assessment of peri-operative analgesia
The mean±SD values of assessment of peri-operative analgesia for all the three groups were recorded and depicted in Table 1 and Fig 1.
The differences in peri-operative analgesia among all the three groups were statistically non-significant (P>0.05). The peri-operative analgesia in the animals of groups-T, P and M did not differ significantly (P>0.05) and the scores recorded were 0.00±0.00, 0.00±0.00 and 0.17±0.40, respectively. Group-T and group-P animals showed no peri-operative pain (score 0) and group-M animals showed no pain to little pain (range: score 0 to score 1). Pain caused due to intravenous administration of propofol can be reduced by administration of opioids (Branson, 2007). Tramadol has been categorized as an opioid analgesic although it can provide analgesia by both opioid and non-opioid mechanisms (Mastrocinque and Fantoni, 2003). It is probable that NSAIDs do not provide any surgical analgesia (Pyati and Gan, 2007).
Depth of anaesthesia
The mean±SD values of depth of anaesthesia for all three groups were recorded and depicted in Table 1 and Fig 1.
The differences in depth of anaesthesia among all the three groups were statistically non-significant (P>0.05). The depth of anaesthesia in the animals of group-T, P and M did not differ significantly (P>0.05) and the scores were recorded as 1.50±0.54, 1.33±0.51 and 1.50±0.54, respectively. Animals in all the three groups showed intact but weak (score 1) to very weak (score 2) palpebral reflex during anaesthesia. Occasional response of palpebral reflex might be due to pain during surgical procedure. In a previous study, mild palpebral reflexes were observed in dogs pre-medicated with pentazocine in propofol anaesthesia (Chandrashekarappa and Ananda, 2009).
Quality of recovery
The mean±SD values of quality of recovery for all the three groups were recorded and depicted in Table 1 and Fig 1.
The scoring of quality of recovery was significantly (P<0.05) higher in group-M as compared to group-T and P. Non-significant (P>0.05) difference was noticed between group-T and P. The scoring of quality of recovery in group-T, P and M animals were recorded as 0.33±0.51, 0.83±0.40 and 1.67±0.51, respectively. Animals in group-T and P showed smooth uncomplicated recovery (score 0) to uncomplicated recovery (score 1) whereas animals in group-M showed uncomplicated recovery (score 1) to difficult recovery (score 2). Combination of IV anaesthetic with opioid analgesics have been used for achieving balanced anaesthesia with reduced side effects and promote earlier recovery time
(Wu et al., 2014). Uncomplicated recovery without any complications was observed in all the three groups. Similar findings were also observed by,
Sams et al., (2008), Thejasree et al., (2017) and
Shinde et al., (2018) in propofol anaesthesia.
Assessment of post-operative analgesia
The mean±SD values of VAS for all the three groups were recorded and depicted in Table 2 and Fig 2.
The VAS was significantly (P<0.05) higher in group-P and M as compared to group-T at 1 hr interval after analgesia. The VAS was significantly (P<0.05) higher in group-M as compared to group-T and group-P at 2 hr interval after analgesia. At 3 hr interval after analgesia, the VAS was significantly (P<0.05) lower in group-T as compared to group-P and M. There was significant (P<0.05) decrease in VAS at different time intervals (1 hr, 2 hr and 3 hr) in all the three groups. At 3 hr interval after analgesia, group-T recorded least VAS (0.33±0.51) followed by group P (1.33±0.81) and group M (2.33±0.51). Tramadol has been categorized as an opioid analgesic although it can provide analgesia by both opioid and non-opioid mechanisms and has been shown to provide sufficient post-operative analgesia in dogs undergoing ovariohysterectomy (Mastrocinque and Fantoni, 2003). Tramadol provided sufficient post-operative analgesia without any side effects in dogs undergoing maxillectomy or mandibulectomy
(Martins et al., 2010). NSAIDs are not effective in acute pain and are thus ineffective (though useful later) are inadequate for immediate post-operative analgesia. It is probable that NSAIDs do not provide any surgical analgesia (Pyati and Gan, 2007).
Physiological parameters
Heart rate (beats/minute)
The mean±SD values of heart rate (beats/min) of different groups at different time intervals were recorded and depicted in the Table 3 and Fig 3.
There was non-significant (P>0.05) difference noticed in the mean values of heart rate between different groups at various time intervals throughout the study period. The heart rate differed non-significantly (P>0.05) at 10 min after analgesia in all the groups as compared to 0 min (baseline) value and at 30 min post analgesia there was significant (P<0.05) increase and thereafter it decreased significantly (P<0.05) till the end of the study. Heart rate increased after the administration of glycopyrrolate in all three groups as it causes increase in heart rate as also opined by Dyson and Davies (1999). Tachycardia noticed in group-T animals could be attributed to vagolytic effect of anticolinergic drug and lack of cardiac depression effect of tramadol as reported by
Natalini et al., (2007) and
Borges et al., (2008). In group-P and -M tachycardia effect could be due to anticolinergic drug as reported by Pandey and Sharma (1986) and
Amarpal et al., (1996).
Respiration rate (breaths/minute)
The mean±SD values of respiratory rate (breaths/min) of different groups at different time intervals were recorded and depicted in the Table 3 and Fig 4.
There was non-significant (P>0.05) difference noticed in the mean values of respiratory rate between different groups at different time intervals throughout the study period. The respiratory rate decreased significantly (P<0.05) from 0 min to 1 hr after analgesia in group-T and P. In group-M, there was non-significant (P>0.05) difference noticed between 0 min to 10 min after analgesia, thereafter it significantly (P<0.05) decreased up to 1 hr after analgesia. Significant (P<0.05) increase in respiratory rate was noticed from 1 hr till the end of the study in all the three groups. The decrease in respiratory rate could be due to depression of respiratory center by propofol. Similar finding of significant (P<0.05) decrease in the respiratory rate followed by increase in respiratory rate of dogs in propofol anaesthesia was observed by
Thejasree et al., (2018) and
Saikia et al., (2019). The decrease in respiratory rate following tramadol administration was also observed by
Mondal et al., (2006), McMillan et al., (2008) and
Gupta et al., (2009). The decline in respiratory rate following pentazocine lactate administration was also recorded by
Amarpal et al., (1996) and
Chandrashekarappa et al., (2009) and following meloxicam administration by
Laredo et al., (2004). Early significant (P<0.05) decrease in the respiratory rate noticed in group-T and P as compared to group-M could be due to the depressing effect of opioids (tramadol and pentazocine lactate) on respiratory center.
Rectal temperature (°C)
The mean±SD values of rectal temperature (°C) of different groups at different time intervals were recorded and depicted in the Table 3 and Fig 5. There was non-significant (P>0.05) difference noticed in the mean values of rectal temperature between different groups at various time intervals throughout the study period. The rectal temperature decreased significantly (P<0.05) at 30 min after analgesia in all the three groups. At 3 hr after analgesia, there was significant (P<0.05) increase in rectal temperature noticed in all the three groups as compared to 30 min value. In general anaesthesia, there is hypothermia because of generalized distribution of blood as a result of peripheral vasodilation, reduced activity of reticular activating system, depression of thermoregulatory center, decreased metabolic rate and reduced skeletal muscle activity (Sahoo
, 2015). Similar finding of significant (P<0.05) decrease in rectal temperature after propofol administration was observed by
Thejasree et al., (2018). However non-significant (P>0.05) decrease was observed by
Shinde et al., (2018) and
Saikia et al., (2019) in propofol anaesthesia. At 3 hr after analgesia, there was significant (P<0.05) increase in rectal temperature noticed in all the three groups as compared to 30 min value which might be due to withdrawal effects of general anaesthesia.
Peripheral arterial oxygen saturation (SpO2), (%)
The mean±SD values of SpO
2 (%) of different groups at different time intervals were recorded and depicted in the Table 3 and Fig 6.
There was non-significant (P>0.05) difference noticed in the mean values of SpO
2 between different groups at various time intervals throughout the study period. The SpO
2 decreased significantly (P<0.05) at 30 min after analgesia in all the three groups. At 3 hr after analgesia, there was significant (P<0.05) increase in SpO
2 noticed in all the three groups as compared to 30 min value. Greater degree of respiratory depression might be the reason of higher decrease in SpO
2 values and the values remained within the normal physiological range
i.e., 90 to 100 in the present study. At 3 hr after analgesia, there was significant (P<0.05) increase in SpO
2 noticed in all the three groups as compared to 30 min value. Similar findings of significant decrease in SpO
2 after propofol administration was observed by
Thejasree et al., (2018) and
Saikia et al., (2019).
Blood pressure (mmHg)
Systolic pressure
The mean±SD values of systolic pressure (mmHg) of different groups at different time intervals were recorded and depicted in the Table 3 and Fig 7.
There was non-significant (P>0.05) difference noticed in the mean values of systolic pressure between different groups at various time intervals throughout the study period. The systolic pressure decreased significantly (P<0.05) at 30 min after analgesia as compared to 0 min (baseline) value in all the three groups and thereafter it increased gradually till the end of the study. Decrease in systolic pressure after propofol administration could be attributed to peripheral vasodilation, decreased sympathetic outflow and myocardial depression. Propofol induced decrease in systemic arterial blood pressure might be due to its direct negative inotropic action and decrease of arterial and venous vascular tone. Similar finding was also observed by
Sams et al., (2008), Amengual et al., (2013) and
Saikia et al., (2019) with propofol anaesthesia.
Diastolic pressure
The mean±SD values of diastolic pressure (mmHg) of different groups at different time intervals were recorded and depicted in the Table 3 and Fig 8.
There was non-significant (P>0.05) difference noticed in the mean values of diastolic pressure between different groups at various time intervals throughout the study period. The diastolic pressure decreased significantly (P<0.05) at 30 min after analgesia as compared to 0 min (baseline) value in all the three groups and thereafter it increased gradually till the end of the study. Decrease in diastolic pressure after propofol administration might have resulted due to peripheral vasodilation, decreased sympathetic outflow and myocardial depression. Decrease in diastolic pressure with propofol induction has also been reported by
Amengual et al., (2013), Taboada and Leece (2014) and
Saikia et al., (2019).