Comparison of xylazine and medetomidine as premedicants for cats being anaesthetised with propofol‐sevoflurane

Abstract

The effects of premedicating cats with saline, xylazine or medetomidine before anaesthetising them with propofol-sevoflurane were compared. Twenty-four cats were randomly assigned to three groups of eight to receive either 0·25 ml of saline, 0·50 mg/kg of xylazine or 0·02 mg/kg of medetomidine intravenously, and anaesthesia was induced with propofol and maintained with sevoflurane. Medetomidine produced a greater reduction in the induction dose of propofol and fewer adverse postoperative effects than saline or xylazine. Hypoxaemia was observed after induction with propofol in the cats premedicated with saline and xylazine, but not in the cats given medetomidine. The cats treated with medetomidine and xylazine developed profound bradycardia. The blood pressure of the cats premedicated with saline and xylazine decreased, but the blood pressure of the cats premedicated with medetomidine was maintained. The cats premedicated with saline took longer to recover from anaesthesia than the other two groups. (Doherty 1988, Dobromylskyj 1996, Golden and others 1998. Their sedative, analgesic and muscle relaxation properties make them particularly suitable for anaesthetising cats (Steinberg 1989, Tranquilli andBenson 1992). Medetomidine is more selective, more potent and more effective than xylazine; an intramuscular dose of 0·18 mg/kg of medetomidine induced the equivalent sedative effect as an intramuscular dose of 3·0 mg/kg of xylazine (Steinberg 1989).Bradycardia, a decrease in cardiac output and a brief period of hypertension followed by a prolonged decrease in arterial blood pressure are usually observed in cats after the administration of xylazine (Tranquilli and Benson 1992). The respiratory effects of xylazine are variable, but respiratory function often remains virtually unchanged (Short and Bufalari 1999). The cardiopulmonary effects of medetomidine are similar to those of xylazine, although they may be more pronounced (Pypendop and Verstegen 1998, Lamont and others 2001); the administration of medetomidine has been associated with sustained hypertension in cats and dogs (Keegan and others 1995, Dobromylskyj 1996, Golden and others 1998. Both xylazine and medetomidine are excellent for premedicating small animals before they are anaesthetised with several injectable and inhalational anaesthetics (Steinberg 1989, Short and Bufalari 1999, Kuusela and others 2001.Propofol is a rapid-acting, non-barbiturate intravenous anaesthetic. Its rapid onset and relatively short duration of action makes it an ideal agent for the induction of general anaesthesia (Bufalari and others 1998). Premedication with xylazine or medetomidine has been reported to significantly reduce the dose of propofol required in cats and dogs (Cullen and Reynoldson 1993).Sevoflurane is a halogenated agent with clinical characteristics similar to isoflurane, but it induces anaesthesia more rapidly, and animals recover from it more quickly than with isoflurane (Mutoh and others 1997). It has been reported to produce an increase in heart rate and a s...

Evaluation of sevoflurane and isoflurane as maintenance agent in buffaloes after glycopyrrolate-xylazine-butorphanol-propofol anaesthesia

“…Elcock and Sweeny (2002) also reported lower analgesia in human for knee artheroscopy maintained on sevoflurane after propofolfentanyl anesthesia than on isoflurane. However, the propofol-sevoflurane combination has also been used in cats (Selmi et al, 2005), dogs (Luis et al, 2009) and goats (Setoyama et al, 2003) but without any report of poor analgesia. Induction scores in both the groups were high as propofol is an ultrashort acting anaesthetic agent which has high serum protein binding (Dawidowicz et al, 2006).…”

The Association of Shelter Veterinarians veterinary medical care guidelines for spay-neuter programs

“…Numerous protocols combining multiple anesthetic agents, including injectable and inhalant agents, exist for pediatric and adult patients. 16,17,[51][52][53][54][55][56][57][58] Administration of analgesics-Analgesic agents are required for all patients undergoing neutering. 59,60 Acceptable choices include opioids (eg, butorphanol, buprenorphine, morphine, hydromorphone, and pentazocine), α 2 -adrenoceptor agonists (eg, medetomidine, dexmedetomidine, and xylazine), NSAIDs (eg, carprofen, meloxicam, tepoxalin, deracoxib, firocoxib, aspirin, flunixin, ketoprofen, and etodolac), and local anesthetics (eg, lidocaine and bupivacaine).…”

The Association of Shelter Veterinarians’ 2016 Veterinary Medical Care Guidelines for Spay-Neuter Programs

“…Numerous cost-effective protocols combining multiple anesthetic and analgesic drugs, including injectable and inhalant agents, exist for achieving balanced anesthesia in pediatric and adult patients. 20,21,[111][112][113][114][115][116][117][118][119][120][121][122] A complete listing of all effective and appropriate anesthetic and analgesic drugs is beyond the scope of these guidelines and is not included here. Extralabel use of many of these agents is an appropriate and common practice in any veterinary medical setting.…”

“…These can be delivered in combination with analgesics. 111,129,[152][153][154][155] Total IM anesthesia Administering a single injection that includes sedative, analgesic, and anesthetic induction agents may reduce patient pain and stress, compared with administering multiple injections. Combining premedications and anesthetic induction agents in a single injection is a useful technique for some spay-neuter programs.…”