This case report describes the clinical signs and treatment of an alfaxalone 10 times overdose in a 12-year-old cat undergoing anaesthesia for MRI. The cat was discharged from hospital following a prolonged recovery including obtunded mentation and cardiorespiratory depression for several hours following cessation of anaesthesia. The cat received supportive therapy that included supplemental oxygen via a face mask, intravenous crystalloid fluids and active rewarming. The benefits of using alfaxalone for maintenance of anaesthesia, its pharmacokinetics and previously reported lethal doses are discussed. Strategies for reducing the incidence of medication errors are presented. An unintentional overdose of alfaxalone by continuous rate infusion has not been reported previously in a cat. Treatment is supportive and directed towards maintenance of the cardiorespiratory systems. Whenever possible, smart pumps that have been designed to reduce human error should be used to help prevent medication errors associated with continuous rate infusions.

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.

This study investigated the effects of vehicles on penetration and retention of lidocaine applied to sheep skin in vitro. Thoracic skin from two sheep was clipped of wool and stored at -20 °C, until used. Skin samples were defrosted and mounted in Franz-type diffusion cells, and then one of the following formulations, each saturated with lidocaine, was added: sodium lauryl sulphate (SLS) 0.5% in water, SLS 1% in water, dimethyl sulphoxide (DMSO) 50% in water (wt/wt), DMSO 100%, isopropyl myristate 100% (IPM), water alone, diethylene glycol monoethyl ether (DGME) 50% in water (wt/wt) and DGME 100%. The penetration of lidocaine in each skin sample was measured over 8 h. Significantly greater lidocaine skin concentrations and flux (J(SS)) were achieved with the nonaqueous vehicles, DMSO 100% (P < 0.00001 and P < 0.01, respectively), followed by DGME 100% and IPM (P < 0.00001 and P < 0.01, respectively). The lag time (t(lag)) for lidocaine penetration in the DMSO 100% vehicle was significantly shorter (P < 0.01) compared with all other vehicles except water. Improved transdermal penetration of lidocaine in the DMSO 100% vehicle was likely due to skin barrier disruption, as determined by differences in pre- and post-treatment transepidermal water loss (TEWL). This study has shown that nonaqueous vehicles enhanced penetration of lidocaine in sheep skin to a greater extent than aqueous vehicles, which has implications for topically applied local anaesthesia in sheep.

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