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Welcome to our page! We do our best to provide to-be and current bunny owners up-to-date info on the best care for their house rabbits. When we adopted our first bunny in 2005, there was almost nothing on the internet to tell us how to care for him. Just in the past few years, information has exploded online, and now it can be confusing! We try to simplify it by posting weekly articles on current issues, daily care, concerns, proper feeding, and other info so you can enjoy your house-bun! If you are just finding us, feel free to look through the older posts also. Please email us if you have any questions! Happy bunnies make happy hearts!
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Saturday, April 9, 2016

Isoflurane vs. Sevoflurane Anesthesia

This article may speak of humans as well as animal in using these anesthesia, but the concept is the same. It seems the bottom line is that the smaller the animal or the more medical issues they may have, Sevoflurane is going to be the safest way. The vets anesthesiologist may need special training and equipment different than with the Isoflurane. (Rhonda)

Since rabbits are unable to vomit, there is no need to withhold the food and water longer than 2 to 4 hours before the planned surgical procedure.


Veterinarians have been using isoflurane since 1986, when it was approved for use in horses.
Approved for use in dogs in 1988 it gained widespread use in many species and in many
practices especially when the price dropped from its original $1/ml of liquid.






Induction of anesthesia in a rabbit, 
using a box or a mask









Advantages of isoflurane over older inhalants are: 
1. Speed of induction and recovery,
2. Greater control of depth of anesthesia, 
3. Less metabolism by the drug in the liver.
4. Significantly less sensitization of the heart to catecholamines.
These properties have made it an outstanding choice for all anesthesia procedures, but especially for the older, sicker patients more commonly seen in practice today.


What is different about sevoflurane?
It is less soluble than isoflurane, which means that inductions and recoveries are even faster.
Mask inductions with sevoflurane were faster and of better quality than with isoflurane in one
study (Johnson, et al, 1998).
Sevoflurane also appears to be better tolerated by mask induction, because it has low pungency and low airway irritability.

Is a faster recovery from anesthesia a significant advantage?
It may be if you are performing a non-painful procedure on an “out-patient” basis. However, if
you are using analgesics or tranquilizers intra- or post-operatively you may not recognize a
faster recovery, since all drugs administered affect recovery time, not just the speed of the
inhalant. (Matthews, et al, 1998)






Complete set of instruments needed for gas anesthesia




















Vaporizer for isoflurane (a halogenated ether used for inhalational anesthesia)












Is sevoflurane safer than isoflurane?
The two anesthesias appear to produce very similar degrees of depression in a dose-dependent manner. The only advantage sevoflurane may have over isoflurane is the ability to change depth of anesthesia slightly quicker. This means you can “lighten” the depth of anesthesia quickly, but it also means that if the animal is not closely observed, it may get too “deep” quickly also.
(In other words, if the animal goes into distress, they can be brought out of anesthesia quickly to save its life.)


What types of cases would I prefer to use sevoflurane for?
At this point, let me make it clear that this is just my opinion, and that we have been using
sevoflurane in both horses and dogs since 1996. If available, I would prefer to use sevoflurane
for mask or chamber inductions, cases requiring Caesarian sections and those very sickest,
moribund patients where I want the best possible control of anesthetic depth. It is also
convenient for an uncomplicated, non-painful short procedure where you want to send the
animal home as quickly as possible.

How much of a transition and adjustment is there to use sevoflurane?
For practitioners (and their technicians) who are using isoflurane, the adjustment to using
sevoflurane is fairly minimal. As previously mentioned, vaporizer settings need to be higher and
animals need to be closely monitored to recognize depth of anesthesia. For practitioners who
might be using halothane, the transition and adjustment is greater, but probably really worth the
effort, since either sevoflurane or isoflurane offers significant advantages over halothane.

If I want to use sevoflurane, how can I minimize the cost?
Since the current cost of sevoflurane is about $1/ml of liquid it is more expensive to use. Cost
can be minimized by limiting waste of the gas; making sure there aren’t leaks in the machine,
breathing circuit or leaks around the cuff of the endotracheal tube. Mask and chamber
inductions are expensive since higher oxygen flows must be used. Premedication with
sedatives or analgesics will help decrease the MAC-value needed for maintenance, which will
help reduce the cost.



Link with more detailed info on anesthesia on rabbits before surgery including videos:
Anesthesia and its monitoring in rabbits
http://www.medirabbit.com/EN/Surgery/Anesthesia/Anes_main/anes_main_en.htm


Footnotes:
http://www.surgivet.com/Userfiles/education-resources/clinical/Isoflurane%20vs%20Sevoflurane.pdf