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

Abstract

Objectives The aim of the study was to evaluate, in a controlled, randomised, masked clinical trial, the influence of administration rate of alfaxalone at induction on its relative potency in cats and to report the incidence of cardiorespiratory adverse effects. Methods Twelve healthy female domestic cats admitted for ovariohysterectomy were premedicated with buprenorphine 20 µg/kg intramuscularly and alfaxalone 3.0 mg/kg subcutaneously. Sedation scores were established (using a published scale ranging from 1 [no sedation] to 5 [profound sedation]) prior to anaesthesia induction with alfaxalone intravenously at 2 mg/kg/min (group A2; n = 6) or 0.5 mg/kg/min (group A0.5; n = 6) to effect until orotracheal intubation was achieved. Sedation scores and alfaxalone induction doses were compared between the groups, using a Mann-Whitney exact test. Results are reported as median and range. Presence of apnoea (no breathing for more than 30 s) or hypotension (mean arterial blood pressure <60 mmHg) within 5 mins postintubation was also reported. Results Although sedation scores (1.5 [range 1.0-3.0] and 2.5 [range 1.0-3.0] for A2 and A0.5, respectively) were not significantly different ( P = 0.32), cats in group A2 required significantly more alfaxalone (4.3 mg/kg [range 3.4-7.0 mg/kg]) than group A0.5 (2.1 mg/kg [range 1.5-2.5 mg/kg]) ( P = 0.002). Two cats in each group presented postinduction apnoea, and two cats in group A2 and three cats in group A0.5 presented postinduction hypotension. Conclusions and relevance The use of a slower induction infusion rate resulted in an increase in the alfaxalone relative potency without obvious cardiorespiratory benefit.

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

“…As reported previously with alfaxalone for induction of anaesthesia in cats, the slower infusion rate resulted in a decreased propofol anaesthetic induction dose requirement. 4 This phenomenon, also seen in humans and in a physiological model in sheep, was explained by a lower but more sustained propofol concentration gradient for even drug delivery throughout the central nervous system when using a slower infusion rate. 3,7 In sheep, the slower infusion rate was also associated with a decrease in propofol peak arterial concentration.…”

“…Ten minutes prior to induction of anaesthesia the sedation level was assessed using a published scoring system (Table 1) and a 22 G over-the-needle catheter was placed in a cephalic vein. 4,6 Anaesthesia was induced with propofol (Provine, propofol emulsion injection, 10 mg/ml; Claris Lifesciences) IV at 4 mg/kg/min (fast) or 1 mg/kg/min (slow) to effect until orotracheal intubation was achieved using a calibrated volumetric infusion pump (Baxter Colleague 3CX; Baxter Healthcare). Once the cat was not supporting its head and its jaw tone was relaxed, lidocaine (5 mg) was sprayed over the larynx (Co-Phenylcaine Forte spray, lidocaine 5%, phenylephrine 0.5%; ENT Technologies) and 15 s later orotracheal intubation attempted.…”

“…The presence of excitement during induction of anaesthesia, bradycardia (HR <95 beats per min), hypotension (MABP <60 mmHg) or apnoea (no evidence of breathing for 30 s or more) within the first 15 mins postintubation Table 1 Sedation scores were ascribed following a published scale 4,5 Sedation score…”

“…3 A recent study in cats demonstrated that a slower induction infusion rate of another commonly used IV anaesthetic (alfaxalone), which also activates the GABA A receptors, resulted in a reduction in the alfaxalone dose needed to achieve orotracheal intubation. 4 The aims of the present study were to evaluate the influence of propofol administration rate at induction of anaesthesia on its relative potency in cats. The hypothesis was that a slower anaesthetic induction infusion rate would achieve anaesthesia using a lower dose of propofol.…”