Isoflurane Machine - theunissenlab/lab-documentation GitHub Wiki

Our lab has our own Isoflurane Machine for administering gas isoflurane for anesthesia. The machine itself works great. There are also two scavengers, one for use during surgery and one for use during induction.

Use:

You must first turn on the oxygen tank, and then open the oxygen valve on the isoflurane machine to either 1.0 (induction, for the little box), or 0.4 (surgery). After oxygen is running you turn on the isoflurane itself. Before you turn on the isoflurane, turn on the scavenger (so you don't forget).

The induction box uses a passive scavenger, you have to weigh it periodically to make sure the filter isn't full. We have a ton of backup filters so don't buy any. The tube that goes to the bird uses an active scavenger, when you flip the switch on it you should hear the fan and you should be able to just barely feel air being sucked into the tube, which should be placed well below the beak of the bird, on the base of the stereotax.

The bird can be induced with 1.0 - 2.0 isoflurane (L/min?). After ~ 5 minutes in the box, after the bird is very unconscious but before breathing starts getting irregular, move the bird to the stereotax, place in the ear bars and beak holder. Hopefully you accomplish all this before the animal begins waking up. Just before you move the animal from the box, turn down the Oxygen to 0.4 (L/min?), and turn down the isoflurane to ~0.5. Getting the animal in the ear bars is one of the hardest parts of an isoflurane surgery- move fast and practice in your mind.

Keep a close watch on their breathing- they should be breathing between 60-100 breaths per minute if they are properly anesthetized, and the temperature should be steady as well. Some animals need more Iso, some need less, and it's all dependent on where the supply tube and suction are located. If breathing goes below 60, or becomes irregular, cut the isoflurane immediately and monitor closely. The most dangerous part of the surgery is the beginning- you should spend the first 15 minutes of every surgery focused entirely on getting the anesthesia level correct, only after breathing is stable should you begin the actual surgery.

Troubleshooting:

  • Animal dies during surgery: Getting the level of anesthesia correct can be very hard. It is tempting to blame the machine, but it is never the machine's fault. It may be the placement of the tube the isoflurane is coming out of, or you just aren't being careful enough with the amount, or a combination. For instance, the most dangerous time in a surgery is ~5-15 minutes in, probably because isoflurane begins building up in their system and adrenaline begins wearing out. It is typical to start the surgery around 0.75 - 0.5 iso and to go even lower around 10 minutes in, say 0.25-0.5. Sometimes you may be at 0.0 and the bird is still unconscious. This is not great, but it is ok. These little birds do not need much! We have found the best place for the Isoflurane supply tube is resting on the beak bar, adjacent to the beak. You can try putting it in the beak as well, but just adjacent seems a little better- perhaps it lets them exhale the iso more effectively. The other thing to check is that the suction isn't too strong or too close to the supply. The suction should be below the bird, perhaps a bit to the side as well.

  • Nothing happens: -- Are you sure there is Oxygen in the oxygen tank? -- Is the oxygen tank on? -- Have you turned the Oxygen valve to 1.0 or 0.4 so the little ball is floating? -- Is the gas being routed to the right place? -- Is there isoflurane in the machine?

  • You get a headache: Make sure the scavenger is on!

  • Urgent need/machine breaks: Rent one from OLAC, which is always an option.

  • Buying Isoflurane: Best to do through the veterinary services website via OLAC. I think I've been able to just buy it through Fisher before though.

  • Inspections/calibration: There is a company that sends someone to Berkeley once a year to do inspections and make sure the machines are still calibrated. They'll send an email and then sign up. I think it has to be done every other year but they are trying to get everyone to do it yearly. As far as I can tell they don't ever actually do anything, and they calibrate to like, 1%, whereas we are usually worried about 0.1%, so it's not very helpful, but it's certainly better than nothing.