Influence of two administration rates of propofol at induction of anaesthesia on its relative potency in cats: a pilot study

Abstract

Objectives This was a randomised, blinded trial to investigate the influence of administration rate on the dose of propofol required for the orotracheal intubation of cats. Methods Twenty-four female domestic cats undergoing ovariohysterectomy were premedicated with oral tramadol (6 mg/kg) or intramuscular tramadol (4 mg/kg), and intramuscular dexmedetomidine (0.007 mg/kg). Oral or intramuscular (IM) tramadol was administered 60 or 30 mins prior to induction of anaesthesia, respectively. Dexmedetomidine was administered 30 mins prior to anaesthetic induction. Sedation scores were established prior to anaesthesia induction with propofol intravenously at 4 mg/kg/min (fast) or 1 mg/kg/min (slow) to effect until orotracheal intubation was achieved without coughing. If coughing occurred, the intubation process was paused for 15 s. Four groups were determined: IM tramadol/propofol fast (GIMF, n = 6); IM tramadol/propofol slow (GIMS, n = 6); oral tramadol/propofol fast (GOF, n = 6); oral tramadol/propofol slow (GOS, n = 6). The Shapiro-Wilk test was used to evaluate for normality of residuals. Sedation scores and propofol anaesthetic induction doses were compared between GIMF and GIMS groups, and between GOF and GOS groups using the Mann-Whitney test and the t-test, respectively ( P = 0.05). The presence of hypotension (mean arterial blood pressure <60 mmHg) or apnoea (no breathing for 30 s or more) within the first 15 mins postintubation was recorded. Results The median sedation scores for GIMF and GOF were not significantly different compared with those for GIMS ( P = 0.94) and GOS ( P = 0.70). However, the mean ± SD propofol anaesthetic induction doses were higher in GIMF (9.1 ± 1.8 mg/kg) and GOF (7.9 ± 1.7 mg/kg) than in GIMS (5.1 ± 1.5 mg/kg; P <0.01) and GOS (5.4 ± 0.3 mg/kg; P <0.01). No hypotension or apnoea were detected. Conclusions and relevance Using the slower anaesthetic induction rate resulted in an increase in propofol relative potency.

Cardiopulmonary and propofol-sparing effects of dexmedetomidine in total intravenous anesthesia in cats undergoing ovariohysterectomy

“…15,16 However, the dexmedetomidine-sparing effect on the propofol dose to permit endotracheal intubation could be higher, considering the speed of propofol injection used in this study. 28 During the 60-min stabilization period, the animals in the dexmedetomidine groups had lower HRs than cats in the Prop group. This was an expected outcome, as dexmedetomidine decreases sympathetic tone, and the stimulation of peripheral adrenergic receptors in the vascular smooth muscle results in increased systemic vascular resistance and reflex bradycardia.…”

“…15,16 However, the dexmedetomidine-sparing effect on the propofol dose to permit endotracheal intubation could be higher, considering the speed of propofol injection used in this study. 28…”

The impact of a stress‐reducing protocol on the quality of pre‐anaesthesia in cats

“…It acts on the GABA A pentameric receptor, opening Cl-channels, but at a different site than benzodiazepines (such as midazolam), and as a glutamate antagonist on the NMDA receptor. 18 Statistically significant differences were found in propofol 'induction dose' between the two groups, suggesting that lower stress levels allowed for a lower dose of propofol to be administered. Again, a lower level of glutamate facilitates the effect of propofol, allowing for smaller doses to be used in anaesthetic induction.…”

“…Propofol was used to induce anaesthesia. It acts on the GABA A pentameric receptor, opening Cl‐channels, but at a different site than benzodiazepines (such as midazolam), and as a glutamate antagonist on the NMDA receptor 18 . Statistically significant differences were found in propofol ‘induction dose’ between the two groups, suggesting that lower stress levels allowed for a lower dose of propofol to be administered.…”

Dose requirement and cardiopulmonary effects of diluted and undiluted propofol for induction of anaesthesia in dogs

“…Due to its physicochemical properties, propofol requires time to reach the targeted receptors (Stokes et al 1991). In humans, cats, and dogs, slower infusion rates of propofol have resulted in lower doses required to induce anaesthesia, and in less cardiorespiratory depression (Peacock et al 1990;Bauquier et al 2017;Bigby et al 2017). The dilution of propofol may achieve a similar outcome without having to slow the induction rate.…”