The Use of Sevoflurane in a 2:1 Mixture of Nitrous Oxide and Oxygen for Rapid Mask Induction of Anaesthesia in the Cat

Abstract

An inhalational technique for rapid induction of anaesthesia in unsedated cats using sevoflurane and nitrous oxide is described. Using a pliable, tight-fitting, face mask, sevoflurane (7.5-8%) was delivered from an out-of-circuit precision vaporiser connected to a coaxial non-rebreathing system using a fresh gas flow of 1 l oxygen and 2 l nitrous oxide per min. Cats were restrained with gentle but firm pressure applied by scruffing the dorsal cervical skin until the righting reflex was lost and the patient could be positioned in lateral recumbency. Typically, cats could be positioned on their side in a light plane of anaesthesia within 1 min of applying the mask, at which time the sevoflurane concentration was reduced to 5% or less. A similar protocol, using a lower initial concentration of sevoflurane, is recommended for old or debilitated patients. Maintenance of light sevoflurane (2-4%) anaesthesia by mask permitted minor interventions to be performed readily, including blood collection, intravenous chemotherapy, abdominal palpation, radiography and ultrasonography. More painful procedures, such as bone marrow aspiration, required a deeper plane of anaesthesia. Cats were sufficiently deep to be intubated, if this was required, about 3 min after commencing the induction. Recovery from sevoflurane/nitrous oxide anaesthesia was smooth and rapid, with most cats being able to right within 5 min of discontinuing the agents. This protocol for rapid inhalational induction and recovery is particularly suited to feline practice, where rendering an uncooperative patient unconscious greatly facilitates the completion of many minor diagnostic and therapeutic procedures, especially when these must be performed on successive days or when peripheral vascular access is limited. For longer procedures, isoflurane may be substituted for sevoflurane for maintenance of anaesthesia in order to minimise cost.

Therapy for Australian cats with lymphosarcoma

“…This may be less of an issue for private practitioners conducting chemotherapy close to the owners place of residence, and where chemotherapy can be done at a more convenient time (such as weekends). Further, the ability to use sevoflurane 14 to immobilise cats rapidly and reversibly for chemotherapy has substantially improved the speed and readiness with which IV chemotherapy can be conducted; this may make the process of out-patient chemotherapy even more convenient for owners and the veterinary team. Overall, the results of the survey suggest that when confronted with a reasonably priced chemotherapy protocol, most well-motivated owners found the results of therapy rewarding, irrespective of the survival time of the individual cat.…”

“…Indeed, treatment of cats with LSA is considerably less expensive than treating dogs with LSA (especially large canine patients), as cytotoxic drugs are used in much smaller quantities. The recent decrease in the cost of doxorubicin 13 has further improved the affordability of multi-drug protocols incorporating this agent, while the availability of sevoflurane anaesthesia 14 to restrain temporarily cats during IV chemotherapy makes the mechanics of performing the procedure simpler, easier and quicker than in the past. Finally, recent detailed reports of survival times for North American cats treated with chemotherapy protocols are promising in terms of remission times, quality of life and the possibility of cure in a select proportion of cases.…”

“…Finally, recent detailed reports of survival times for North American cats treated with chemotherapy protocols are promising in terms of remission times, quality of life and the possibility of cure in a select proportion of cases. 11,12,[14][15][16][17][18][19][20][21][22][23][24][25] In human patients with lymphoma, histological classification, clinical staging and presence or absence of secondary clinical signs are well correlated with response to specified chemotherapy protocols. 26,27 Attempts to identify similar correlations are progressing in canine LSA 28 and similar data are emerging for cats also.…”

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

“…Like other inhalational agents, it produces a dose-dependent decrease in cardiac output, but at clinically effective concentrations cardiac output is well maintained (Doi andothers 1983, Hikasa andothers 1997). There is increasing interest in the use of sevoflurane in veterinary medicine (Branson and others 2001), and clinical trials have shown that this volatile anaesthetic agent is effective in cats and dogs (Tzannes andothers 2000, Branson andothers 2001).…”

Sevoflurane and its use in veterinary practice

“…Για την εγκατάσταση της αναισθησίας στις γάτες έχει περιγραφεί η χρήση του σεβοφλουρανίου σε συνδυασμό με Ν 2 0, χωρίς την προηγουμένη εφαρμογή προαναισθη-τικής αγωγής, για την πραγματοποίηση συντόμων κλινι κών πράξεων (Tzannes et al 2000).…”