ABSTRACT: The opportunities for practising safe anaesthesia are constantly increasing over time. New and improved anaesthetic injectable drugs and gases are becoming available. One of the current opportunities is to upgrade your anaesthetic gas to Sevoflurane. Having undergone this change in our practice, it feels as if the anaesthetics have undergone a fine tuning – comparable to changing from driving a standard car to that of driving one with power steering.

Sevoflurane (SevoFlo – Abbott Animal Health) is a relatively ‘new’ volatile gaseous anaesthetic agent to veterinary practice. Its use is already established in the human field and an increasing number of veterinary practices are starting to use it as the inhalation anaesthetic of choice.

Table 1 shows a comparison between Sevoflurane and Isoflurane – the latter currently being the most commonly used anaesthetic agent in veterinary practice.

Figure 1: Comparison of the blood:gas solubility IBGS] coefficients of three anaesthetic agents

Personal experience

Even with full training, it was still a daunting experience to start to use a new volatile agent. However, the practice team and I soon became more confident in using Sevoflurane. The manufacturers offered:

•   vaporisers on a loan basis

•   as arranged by the local representative

•   a leak check of the anaesthetic machines

•   full training to obtain the best from their Sevoflurane gas system

•   literature to help the practice market this anaesthetic to clients.

The training guide outlines a suggested induction sequence (Figure 2).

Figure 2: Suggested Sevoflurane anaesthesia induction sequence

I was expecting to see quite a change in the way an animal was ‘masked down’. However, there was not a dramatic change; although, as a general rule, I have found that the procedure is now easier than it was before. I think that this is because Sevoflurane appears to be less irritant to mucous membranes and to result in faster induction than with Isoflurane.

Routine general anaesthesia

The routine procedure for administering a general anaesthetic in my practice is to use a combination dose of acepromazine and buprenorphine as the premedicant, followed by propofol as the intravenous induction agent.

Premedication

Most manufacturers supply charts with premedication dose guides. Any changes in the premedication regimen are decided by the veterinary surgeon in charge. My experience of working with Sevoflurane is that that veterinary surgeons chose to modify the premedication quantities from that listed on the chart, in order to tailor the level of anaesthesia to the individual needs of the animal – this usually involved an adjustment of the dose of buprenorphine.

Induction

It is recommended that during the induction phase, the Sevoflurane is set at 3%. This can then be adjusted according to the depth of anaesthesia, as under usual circumstances. I have found that there is very little difference between the induction process with either Sevoflurane or Isoflurane.

Maintenance

To create a change in the anaesthetic level, I found it best to work in increments of 0.25%. This enabled me to ‘fine tune’ the depth of anaesthesia in my patients.

The data sheet suggests that ‘surgical levels of anaesthesia in the healthy dog can be maintained with inhaled concentrations of 3.3 to 3.6% in the presence of premedication’. As a general rule, I have found the above to be true.

As would be expected, higher levels of Sevoflurane gas are occasionally needed as the level of surgical pain is increased. The same is true that lower levels of gas are often used to maintain cases where there is little or no pain stimulus.

Recovery

As a consequence of the veterinary surgeon tailoring the premedication, we have seen improvements in the recovery of patients – it is generally smooth and patients are usually in sternal recumbency faster than when using Isoflurane.

Cost and equipment implications

At purchase level, Sevoflurane is considerably more expensive than Isoflurane at £156.00 as opposed to between £21.00-642.00 for Isoflurane; but if it is used with a ‘low-flow’ system, the actual costs of anaesthesia begin to equate and Sevoflurane is only slightly more expensive to use than Isoflurane. Sevoflurane requires a specific vaporiser, which can be fitted to a standard anaesthetic machine (Figure 3).

Figure 3: Sevoflurane requires a specific vaporiser

Conclusion

Overall, the change to Sevoflurane has had a positive impact on anaesthesia in the practice. I feel that, since the changeover, the veterinary team has had greater control over the anaesthetic procedures performed and that our patients have benefited from this. 

Author

Jo Lewis RVN D32/33 MBVNA

Jo began her veterinary nursing career in 1993. Since then, her nursing experience has been based in the Worcestershire/ Gloucestershire area. During that time she has had opportunities to experience the variety of mixed practice and to nurse birds of prey. Jo currently works at the Vets on the
Park veterinary clinics.

To cite this article use either

DOI: 10.1111/j.2045-0648.2011.00093.x or Veterinary Nursing Journal Vol 26 pp 361 -362

• VOL 26 • October 2011 • Veterinary Nursing Journal